1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Programming & development tools.
43 * Gdb: (gdb). The @sc{gnu} debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2003 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Agent Expressions:: The GDB Agent Expression Mechanism
160 * Copying:: GNU General Public License says
161 how you can copy and share GDB
162 * GNU Free Documentation License:: The license for this documentation
171 @unnumbered Summary of @value{GDBN}
173 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
174 going on ``inside'' another program while it executes---or what another
175 program was doing at the moment it crashed.
177 @value{GDBN} can do four main kinds of things (plus other things in support of
178 these) to help you catch bugs in the act:
182 Start your program, specifying anything that might affect its behavior.
185 Make your program stop on specified conditions.
188 Examine what has happened, when your program has stopped.
191 Change things in your program, so you can experiment with correcting the
192 effects of one bug and go on to learn about another.
195 You can use @value{GDBN} to debug programs written in C and C++.
196 For more information, see @ref{Support,,Supported languages}.
197 For more information, see @ref{C,,C and C++}.
200 Support for Modula-2 is partial. For information on Modula-2, see
201 @ref{Modula-2,,Modula-2}.
204 Debugging Pascal programs which use sets, subranges, file variables, or
205 nested functions does not currently work. @value{GDBN} does not support
206 entering expressions, printing values, or similar features using Pascal
210 @value{GDBN} can be used to debug programs written in Fortran, although
211 it may be necessary to refer to some variables with a trailing
214 @value{GDBN} can be used to debug programs written in Objective-C,
215 using either the Apple/NeXT or the GNU Objective-C runtime.
218 * Free Software:: Freely redistributable software
219 * Contributors:: Contributors to GDB
223 @unnumberedsec Free software
225 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
226 General Public License
227 (GPL). The GPL gives you the freedom to copy or adapt a licensed
228 program---but every person getting a copy also gets with it the
229 freedom to modify that copy (which means that they must get access to
230 the source code), and the freedom to distribute further copies.
231 Typical software companies use copyrights to limit your freedoms; the
232 Free Software Foundation uses the GPL to preserve these freedoms.
234 Fundamentally, the General Public License is a license which says that
235 you have these freedoms and that you cannot take these freedoms away
238 @unnumberedsec Free Software Needs Free Documentation
240 The biggest deficiency in the free software community today is not in
241 the software---it is the lack of good free documentation that we can
242 include with the free software. Many of our most important
243 programs do not come with free reference manuals and free introductory
244 texts. Documentation is an essential part of any software package;
245 when an important free software package does not come with a free
246 manual and a free tutorial, that is a major gap. We have many such
249 Consider Perl, for instance. The tutorial manuals that people
250 normally use are non-free. How did this come about? Because the
251 authors of those manuals published them with restrictive terms---no
252 copying, no modification, source files not available---which exclude
253 them from the free software world.
255 That wasn't the first time this sort of thing happened, and it was far
256 from the last. Many times we have heard a GNU user eagerly describe a
257 manual that he is writing, his intended contribution to the community,
258 only to learn that he had ruined everything by signing a publication
259 contract to make it non-free.
261 Free documentation, like free software, is a matter of freedom, not
262 price. The problem with the non-free manual is not that publishers
263 charge a price for printed copies---that in itself is fine. (The Free
264 Software Foundation sells printed copies of manuals, too.) The
265 problem is the restrictions on the use of the manual. Free manuals
266 are available in source code form, and give you permission to copy and
267 modify. Non-free manuals do not allow this.
269 The criteria of freedom for a free manual are roughly the same as for
270 free software. Redistribution (including the normal kinds of
271 commercial redistribution) must be permitted, so that the manual can
272 accompany every copy of the program, both on-line and on paper.
274 Permission for modification of the technical content is crucial too.
275 When people modify the software, adding or changing features, if they
276 are conscientious they will change the manual too---so they can
277 provide accurate and clear documentation for the modified program. A
278 manual that leaves you no choice but to write a new manual to document
279 a changed version of the program is not really available to our
282 Some kinds of limits on the way modification is handled are
283 acceptable. For example, requirements to preserve the original
284 author's copyright notice, the distribution terms, or the list of
285 authors, are ok. It is also no problem to require modified versions
286 to include notice that they were modified. Even entire sections that
287 may not be deleted or changed are acceptable, as long as they deal
288 with nontechnical topics (like this one). These kinds of restrictions
289 are acceptable because they don't obstruct the community's normal use
292 However, it must be possible to modify all the @emph{technical}
293 content of the manual, and then distribute the result in all the usual
294 media, through all the usual channels. Otherwise, the restrictions
295 obstruct the use of the manual, it is not free, and we need another
296 manual to replace it.
298 Please spread the word about this issue. Our community continues to
299 lose manuals to proprietary publishing. If we spread the word that
300 free software needs free reference manuals and free tutorials, perhaps
301 the next person who wants to contribute by writing documentation will
302 realize, before it is too late, that only free manuals contribute to
303 the free software community.
305 If you are writing documentation, please insist on publishing it under
306 the GNU Free Documentation License or another free documentation
307 license. Remember that this decision requires your approval---you
308 don't have to let the publisher decide. Some commercial publishers
309 will use a free license if you insist, but they will not propose the
310 option; it is up to you to raise the issue and say firmly that this is
311 what you want. If the publisher you are dealing with refuses, please
312 try other publishers. If you're not sure whether a proposed license
313 is free, write to @email{licensing@@gnu.org}.
315 You can encourage commercial publishers to sell more free, copylefted
316 manuals and tutorials by buying them, and particularly by buying
317 copies from the publishers that paid for their writing or for major
318 improvements. Meanwhile, try to avoid buying non-free documentation
319 at all. Check the distribution terms of a manual before you buy it,
320 and insist that whoever seeks your business must respect your freedom.
321 Check the history of the book, and try to reward the publishers that
322 have paid or pay the authors to work on it.
324 The Free Software Foundation maintains a list of free documentation
325 published by other publishers, at
326 @url{http://www.fsf.org/doc/other-free-books.html}.
329 @unnumberedsec Contributors to @value{GDBN}
331 Richard Stallman was the original author of @value{GDBN}, and of many
332 other @sc{gnu} programs. Many others have contributed to its
333 development. This section attempts to credit major contributors. One
334 of the virtues of free software is that everyone is free to contribute
335 to it; with regret, we cannot actually acknowledge everyone here. The
336 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
337 blow-by-blow account.
339 Changes much prior to version 2.0 are lost in the mists of time.
342 @emph{Plea:} Additions to this section are particularly welcome. If you
343 or your friends (or enemies, to be evenhanded) have been unfairly
344 omitted from this list, we would like to add your names!
347 So that they may not regard their many labors as thankless, we
348 particularly thank those who shepherded @value{GDBN} through major
350 Andrew Cagney (releases 6.0, 5.3, 5.2, 5.1 and 5.0);
351 Jim Blandy (release 4.18);
352 Jason Molenda (release 4.17);
353 Stan Shebs (release 4.14);
354 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
355 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
356 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
357 Jim Kingdon (releases 3.5, 3.4, and 3.3);
358 and Randy Smith (releases 3.2, 3.1, and 3.0).
360 Richard Stallman, assisted at various times by Peter TerMaat, Chris
361 Hanson, and Richard Mlynarik, handled releases through 2.8.
363 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
364 in @value{GDBN}, with significant additional contributions from Per
365 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
366 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
367 much general update work leading to release 3.0).
369 @value{GDBN} uses the BFD subroutine library to examine multiple
370 object-file formats; BFD was a joint project of David V.
371 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
373 David Johnson wrote the original COFF support; Pace Willison did
374 the original support for encapsulated COFF.
376 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
378 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
379 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
381 Jean-Daniel Fekete contributed Sun 386i support.
382 Chris Hanson improved the HP9000 support.
383 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
384 David Johnson contributed Encore Umax support.
385 Jyrki Kuoppala contributed Altos 3068 support.
386 Jeff Law contributed HP PA and SOM support.
387 Keith Packard contributed NS32K support.
388 Doug Rabson contributed Acorn Risc Machine support.
389 Bob Rusk contributed Harris Nighthawk CX-UX support.
390 Chris Smith contributed Convex support (and Fortran debugging).
391 Jonathan Stone contributed Pyramid support.
392 Michael Tiemann contributed SPARC support.
393 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
394 Pace Willison contributed Intel 386 support.
395 Jay Vosburgh contributed Symmetry support.
396 Marko Mlinar contributed OpenRISC 1000 support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Renesas America, Ltd. sponsored the support for H8/300, H8/500, and
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Renesas sponsored the support for D10V, D30V, and M32R/D processors.
428 Toshiba sponsored the support for the TX39 Mips processor.
430 Matsushita sponsored the support for the MN10200 and MN10300 processors.
432 Fujitsu sponsored the support for SPARClite and FR30 processors.
434 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
437 Michael Snyder added support for tracepoints.
439 Stu Grossman wrote gdbserver.
441 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
442 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
444 The following people at the Hewlett-Packard Company contributed
445 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
446 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
447 compiler, and the terminal user interface: Ben Krepp, Richard Title,
448 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
449 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
450 information in this manual.
452 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
453 Robert Hoehne made significant contributions to the DJGPP port.
455 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
456 development since 1991. Cygnus engineers who have worked on @value{GDBN}
457 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
458 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
459 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
460 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
461 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
462 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
463 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
464 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
465 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
466 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
467 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
468 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
469 Zuhn have made contributions both large and small.
471 Jim Blandy added support for preprocessor macros, while working for Red
475 @chapter A Sample @value{GDBN} Session
477 You can use this manual at your leisure to read all about @value{GDBN}.
478 However, a handful of commands are enough to get started using the
479 debugger. This chapter illustrates those commands.
482 In this sample session, we emphasize user input like this: @b{input},
483 to make it easier to pick out from the surrounding output.
486 @c FIXME: this example may not be appropriate for some configs, where
487 @c FIXME...primary interest is in remote use.
489 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
490 processor) exhibits the following bug: sometimes, when we change its
491 quote strings from the default, the commands used to capture one macro
492 definition within another stop working. In the following short @code{m4}
493 session, we define a macro @code{foo} which expands to @code{0000}; we
494 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
495 same thing. However, when we change the open quote string to
496 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
497 procedure fails to define a new synonym @code{baz}:
506 @b{define(bar,defn(`foo'))}
510 @b{changequote(<QUOTE>,<UNQUOTE>)}
512 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
515 m4: End of input: 0: fatal error: EOF in string
519 Let us use @value{GDBN} to try to see what is going on.
522 $ @b{@value{GDBP} m4}
523 @c FIXME: this falsifies the exact text played out, to permit smallbook
524 @c FIXME... format to come out better.
525 @value{GDBN} is free software and you are welcome to distribute copies
526 of it under certain conditions; type "show copying" to see
528 There is absolutely no warranty for @value{GDBN}; type "show warranty"
531 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
536 @value{GDBN} reads only enough symbol data to know where to find the
537 rest when needed; as a result, the first prompt comes up very quickly.
538 We now tell @value{GDBN} to use a narrower display width than usual, so
539 that examples fit in this manual.
542 (@value{GDBP}) @b{set width 70}
546 We need to see how the @code{m4} built-in @code{changequote} works.
547 Having looked at the source, we know the relevant subroutine is
548 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
549 @code{break} command.
552 (@value{GDBP}) @b{break m4_changequote}
553 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
557 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
558 control; as long as control does not reach the @code{m4_changequote}
559 subroutine, the program runs as usual:
562 (@value{GDBP}) @b{run}
563 Starting program: /work/Editorial/gdb/gnu/m4/m4
571 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
572 suspends execution of @code{m4}, displaying information about the
573 context where it stops.
576 @b{changequote(<QUOTE>,<UNQUOTE>)}
578 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
580 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
584 Now we use the command @code{n} (@code{next}) to advance execution to
585 the next line of the current function.
589 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
594 @code{set_quotes} looks like a promising subroutine. We can go into it
595 by using the command @code{s} (@code{step}) instead of @code{next}.
596 @code{step} goes to the next line to be executed in @emph{any}
597 subroutine, so it steps into @code{set_quotes}.
601 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
603 530 if (lquote != def_lquote)
607 The display that shows the subroutine where @code{m4} is now
608 suspended (and its arguments) is called a stack frame display. It
609 shows a summary of the stack. We can use the @code{backtrace}
610 command (which can also be spelled @code{bt}), to see where we are
611 in the stack as a whole: the @code{backtrace} command displays a
612 stack frame for each active subroutine.
615 (@value{GDBP}) @b{bt}
616 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
618 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
620 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
621 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
623 #4 0x79dc in expand_input () at macro.c:40
624 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
628 We step through a few more lines to see what happens. The first two
629 times, we can use @samp{s}; the next two times we use @code{n} to avoid
630 falling into the @code{xstrdup} subroutine.
634 0x3b5c 532 if (rquote != def_rquote)
636 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
637 def_lquote : xstrdup(lq);
639 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
642 538 len_lquote = strlen(rquote);
646 The last line displayed looks a little odd; we can examine the variables
647 @code{lquote} and @code{rquote} to see if they are in fact the new left
648 and right quotes we specified. We use the command @code{p}
649 (@code{print}) to see their values.
652 (@value{GDBP}) @b{p lquote}
653 $1 = 0x35d40 "<QUOTE>"
654 (@value{GDBP}) @b{p rquote}
655 $2 = 0x35d50 "<UNQUOTE>"
659 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
660 To look at some context, we can display ten lines of source
661 surrounding the current line with the @code{l} (@code{list}) command.
667 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
669 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
672 538 len_lquote = strlen(rquote);
673 539 len_rquote = strlen(lquote);
680 Let us step past the two lines that set @code{len_lquote} and
681 @code{len_rquote}, and then examine the values of those variables.
685 539 len_rquote = strlen(lquote);
688 (@value{GDBP}) @b{p len_lquote}
690 (@value{GDBP}) @b{p len_rquote}
695 That certainly looks wrong, assuming @code{len_lquote} and
696 @code{len_rquote} are meant to be the lengths of @code{lquote} and
697 @code{rquote} respectively. We can set them to better values using
698 the @code{p} command, since it can print the value of
699 any expression---and that expression can include subroutine calls and
703 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
705 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
710 Is that enough to fix the problem of using the new quotes with the
711 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
712 executing with the @code{c} (@code{continue}) command, and then try the
713 example that caused trouble initially:
719 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
726 Success! The new quotes now work just as well as the default ones. The
727 problem seems to have been just the two typos defining the wrong
728 lengths. We allow @code{m4} exit by giving it an EOF as input:
732 Program exited normally.
736 The message @samp{Program exited normally.} is from @value{GDBN}; it
737 indicates @code{m4} has finished executing. We can end our @value{GDBN}
738 session with the @value{GDBN} @code{quit} command.
741 (@value{GDBP}) @b{quit}
745 @chapter Getting In and Out of @value{GDBN}
747 This chapter discusses how to start @value{GDBN}, and how to get out of it.
751 type @samp{@value{GDBP}} to start @value{GDBN}.
753 type @kbd{quit} or @kbd{C-d} to exit.
757 * Invoking GDB:: How to start @value{GDBN}
758 * Quitting GDB:: How to quit @value{GDBN}
759 * Shell Commands:: How to use shell commands inside @value{GDBN}
760 * Logging output:: How to log @value{GDBN}'s output to a file
764 @section Invoking @value{GDBN}
766 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
767 @value{GDBN} reads commands from the terminal until you tell it to exit.
769 You can also run @code{@value{GDBP}} with a variety of arguments and options,
770 to specify more of your debugging environment at the outset.
772 The command-line options described here are designed
773 to cover a variety of situations; in some environments, some of these
774 options may effectively be unavailable.
776 The most usual way to start @value{GDBN} is with one argument,
777 specifying an executable program:
780 @value{GDBP} @var{program}
784 You can also start with both an executable program and a core file
788 @value{GDBP} @var{program} @var{core}
791 You can, instead, specify a process ID as a second argument, if you want
792 to debug a running process:
795 @value{GDBP} @var{program} 1234
799 would attach @value{GDBN} to process @code{1234} (unless you also have a file
800 named @file{1234}; @value{GDBN} does check for a core file first).
802 Taking advantage of the second command-line argument requires a fairly
803 complete operating system; when you use @value{GDBN} as a remote
804 debugger attached to a bare board, there may not be any notion of
805 ``process'', and there is often no way to get a core dump. @value{GDBN}
806 will warn you if it is unable to attach or to read core dumps.
808 You can optionally have @code{@value{GDBP}} pass any arguments after the
809 executable file to the inferior using @code{--args}. This option stops
812 gdb --args gcc -O2 -c foo.c
814 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
815 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
817 You can run @code{@value{GDBP}} without printing the front material, which describes
818 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
825 You can further control how @value{GDBN} starts up by using command-line
826 options. @value{GDBN} itself can remind you of the options available.
836 to display all available options and briefly describe their use
837 (@samp{@value{GDBP} -h} is a shorter equivalent).
839 All options and command line arguments you give are processed
840 in sequential order. The order makes a difference when the
841 @samp{-x} option is used.
845 * File Options:: Choosing files
846 * Mode Options:: Choosing modes
850 @subsection Choosing files
852 When @value{GDBN} starts, it reads any arguments other than options as
853 specifying an executable file and core file (or process ID). This is
854 the same as if the arguments were specified by the @samp{-se} and
855 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
856 first argument that does not have an associated option flag as
857 equivalent to the @samp{-se} option followed by that argument; and the
858 second argument that does not have an associated option flag, if any, as
859 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
860 If the second argument begins with a decimal digit, @value{GDBN} will
861 first attempt to attach to it as a process, and if that fails, attempt
862 to open it as a corefile. If you have a corefile whose name begins with
863 a digit, you can prevent @value{GDBN} from treating it as a pid by
864 prefixing it with @file{./}, eg. @file{./12345}.
866 If @value{GDBN} has not been configured to included core file support,
867 such as for most embedded targets, then it will complain about a second
868 argument and ignore it.
870 Many options have both long and short forms; both are shown in the
871 following list. @value{GDBN} also recognizes the long forms if you truncate
872 them, so long as enough of the option is present to be unambiguous.
873 (If you prefer, you can flag option arguments with @samp{--} rather
874 than @samp{-}, though we illustrate the more usual convention.)
876 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
877 @c way, both those who look for -foo and --foo in the index, will find
881 @item -symbols @var{file}
883 @cindex @code{--symbols}
885 Read symbol table from file @var{file}.
887 @item -exec @var{file}
889 @cindex @code{--exec}
891 Use file @var{file} as the executable file to execute when appropriate,
892 and for examining pure data in conjunction with a core dump.
896 Read symbol table from file @var{file} and use it as the executable
899 @item -core @var{file}
901 @cindex @code{--core}
903 Use file @var{file} as a core dump to examine.
905 @item -c @var{number}
906 @item -pid @var{number}
907 @itemx -p @var{number}
910 Connect to process ID @var{number}, as with the @code{attach} command.
911 If there is no such process, @value{GDBN} will attempt to open a core
912 file named @var{number}.
914 @item -command @var{file}
916 @cindex @code{--command}
918 Execute @value{GDBN} commands from file @var{file}. @xref{Command
919 Files,, Command files}.
921 @item -directory @var{directory}
922 @itemx -d @var{directory}
923 @cindex @code{--directory}
925 Add @var{directory} to the path to search for source files.
929 @cindex @code{--mapped}
931 @emph{Warning: this option depends on operating system facilities that are not
932 supported on all systems.}@*
933 If memory-mapped files are available on your system through the @code{mmap}
934 system call, you can use this option
935 to have @value{GDBN} write the symbols from your
936 program into a reusable file in the current directory. If the program you are debugging is
937 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
938 Future @value{GDBN} debugging sessions notice the presence of this file,
939 and can quickly map in symbol information from it, rather than reading
940 the symbol table from the executable program.
942 The @file{.syms} file is specific to the host machine where @value{GDBN}
943 is run. It holds an exact image of the internal @value{GDBN} symbol
944 table. It cannot be shared across multiple host platforms.
948 @cindex @code{--readnow}
950 Read each symbol file's entire symbol table immediately, rather than
951 the default, which is to read it incrementally as it is needed.
952 This makes startup slower, but makes future operations faster.
956 You typically combine the @code{-mapped} and @code{-readnow} options in
957 order to build a @file{.syms} file that contains complete symbol
958 information. (@xref{Files,,Commands to specify files}, for information
959 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
960 but build a @file{.syms} file for future use is:
963 gdb -batch -nx -mapped -readnow programname
967 @subsection Choosing modes
969 You can run @value{GDBN} in various alternative modes---for example, in
970 batch mode or quiet mode.
977 Do not execute commands found in any initialization files. Normally,
978 @value{GDBN} executes the commands in these files after all the command
979 options and arguments have been processed. @xref{Command Files,,Command
985 @cindex @code{--quiet}
986 @cindex @code{--silent}
988 ``Quiet''. Do not print the introductory and copyright messages. These
989 messages are also suppressed in batch mode.
992 @cindex @code{--batch}
993 Run in batch mode. Exit with status @code{0} after processing all the
994 command files specified with @samp{-x} (and all commands from
995 initialization files, if not inhibited with @samp{-n}). Exit with
996 nonzero status if an error occurs in executing the @value{GDBN} commands
997 in the command files.
999 Batch mode may be useful for running @value{GDBN} as a filter, for
1000 example to download and run a program on another computer; in order to
1001 make this more useful, the message
1004 Program exited normally.
1008 (which is ordinarily issued whenever a program running under
1009 @value{GDBN} control terminates) is not issued when running in batch
1014 @cindex @code{--nowindows}
1016 ``No windows''. If @value{GDBN} comes with a graphical user interface
1017 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1018 interface. If no GUI is available, this option has no effect.
1022 @cindex @code{--windows}
1024 If @value{GDBN} includes a GUI, then this option requires it to be
1027 @item -cd @var{directory}
1029 Run @value{GDBN} using @var{directory} as its working directory,
1030 instead of the current directory.
1034 @cindex @code{--fullname}
1036 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1037 subprocess. It tells @value{GDBN} to output the full file name and line
1038 number in a standard, recognizable fashion each time a stack frame is
1039 displayed (which includes each time your program stops). This
1040 recognizable format looks like two @samp{\032} characters, followed by
1041 the file name, line number and character position separated by colons,
1042 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1043 @samp{\032} characters as a signal to display the source code for the
1047 @cindex @code{--epoch}
1048 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1049 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1050 routines so as to allow Epoch to display values of expressions in a
1053 @item -annotate @var{level}
1054 @cindex @code{--annotate}
1055 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1056 effect is identical to using @samp{set annotate @var{level}}
1057 (@pxref{Annotations}). The annotation @var{level} controls how much
1058 information @value{GDBN} prints together with its prompt, values of
1059 expressions, source lines, and other types of output. Level 0 is the
1060 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1061 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1062 that control @value{GDBN}, and level 2 has been deprecated.
1064 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1068 @cindex @code{--async}
1069 Use the asynchronous event loop for the command-line interface.
1070 @value{GDBN} processes all events, such as user keyboard input, via a
1071 special event loop. This allows @value{GDBN} to accept and process user
1072 commands in parallel with the debugged process being
1073 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1074 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1075 suspended when the debuggee runs.}, so you don't need to wait for
1076 control to return to @value{GDBN} before you type the next command.
1077 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1078 operation is not yet in place, so @samp{-async} does not work fully
1080 @c FIXME: when the target side of the event loop is done, the above NOTE
1081 @c should be removed.
1083 When the standard input is connected to a terminal device, @value{GDBN}
1084 uses the asynchronous event loop by default, unless disabled by the
1085 @samp{-noasync} option.
1088 @cindex @code{--noasync}
1089 Disable the asynchronous event loop for the command-line interface.
1092 @cindex @code{--args}
1093 Change interpretation of command line so that arguments following the
1094 executable file are passed as command line arguments to the inferior.
1095 This option stops option processing.
1097 @item -baud @var{bps}
1099 @cindex @code{--baud}
1101 Set the line speed (baud rate or bits per second) of any serial
1102 interface used by @value{GDBN} for remote debugging.
1104 @item -tty @var{device}
1105 @itemx -t @var{device}
1106 @cindex @code{--tty}
1108 Run using @var{device} for your program's standard input and output.
1109 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1111 @c resolve the situation of these eventually
1113 @cindex @code{--tui}
1114 Activate the Terminal User Interface when starting.
1115 The Terminal User Interface manages several text windows on the terminal,
1116 showing source, assembly, registers and @value{GDBN} command outputs
1117 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1118 Do not use this option if you run @value{GDBN} from Emacs
1119 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1122 @c @cindex @code{--xdb}
1123 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1124 @c For information, see the file @file{xdb_trans.html}, which is usually
1125 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1128 @item -interpreter @var{interp}
1129 @cindex @code{--interpreter}
1130 Use the interpreter @var{interp} for interface with the controlling
1131 program or device. This option is meant to be set by programs which
1132 communicate with @value{GDBN} using it as a back end.
1133 @xref{Interpreters, , Command Interpreters}.
1135 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1136 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1137 The @sc{gdb/mi} Interface}) included in @var{GDBN} version 6.0. The
1138 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3,
1139 can be selected with @samp{--interpreter=mi1}. Earlier @sc{gdb/mi}
1140 interfaces are not supported.
1143 @cindex @code{--write}
1144 Open the executable and core files for both reading and writing. This
1145 is equivalent to the @samp{set write on} command inside @value{GDBN}
1149 @cindex @code{--statistics}
1150 This option causes @value{GDBN} to print statistics about time and
1151 memory usage after it completes each command and returns to the prompt.
1154 @cindex @code{--version}
1155 This option causes @value{GDBN} to print its version number and
1156 no-warranty blurb, and exit.
1161 @section Quitting @value{GDBN}
1162 @cindex exiting @value{GDBN}
1163 @cindex leaving @value{GDBN}
1166 @kindex quit @r{[}@var{expression}@r{]}
1167 @kindex q @r{(@code{quit})}
1168 @item quit @r{[}@var{expression}@r{]}
1170 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1171 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1172 do not supply @var{expression}, @value{GDBN} will terminate normally;
1173 otherwise it will terminate using the result of @var{expression} as the
1178 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1179 terminates the action of any @value{GDBN} command that is in progress and
1180 returns to @value{GDBN} command level. It is safe to type the interrupt
1181 character at any time because @value{GDBN} does not allow it to take effect
1182 until a time when it is safe.
1184 If you have been using @value{GDBN} to control an attached process or
1185 device, you can release it with the @code{detach} command
1186 (@pxref{Attach, ,Debugging an already-running process}).
1188 @node Shell Commands
1189 @section Shell commands
1191 If you need to execute occasional shell commands during your
1192 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1193 just use the @code{shell} command.
1197 @cindex shell escape
1198 @item shell @var{command string}
1199 Invoke a standard shell to execute @var{command string}.
1200 If it exists, the environment variable @code{SHELL} determines which
1201 shell to run. Otherwise @value{GDBN} uses the default shell
1202 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1205 The utility @code{make} is often needed in development environments.
1206 You do not have to use the @code{shell} command for this purpose in
1211 @cindex calling make
1212 @item make @var{make-args}
1213 Execute the @code{make} program with the specified
1214 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1217 @node Logging output
1218 @section Logging output
1219 @cindex logging @value{GDBN} output
1221 You may want to save the output of @value{GDBN} commands to a file.
1222 There are several commands to control @value{GDBN}'s logging.
1226 @item set logging on
1228 @item set logging off
1230 @item set logging file @var{file}
1231 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1232 @item set logging overwrite [on|off]
1233 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1234 you want @code{set logging on} to overwrite the logfile instead.
1235 @item set logging redirect [on|off]
1236 By default, @value{GDBN} output will go to both the terminal and the logfile.
1237 Set @code{redirect} if you want output to go only to the log file.
1238 @kindex show logging
1240 Show the current values of the logging settings.
1244 @chapter @value{GDBN} Commands
1246 You can abbreviate a @value{GDBN} command to the first few letters of the command
1247 name, if that abbreviation is unambiguous; and you can repeat certain
1248 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1249 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1250 show you the alternatives available, if there is more than one possibility).
1253 * Command Syntax:: How to give commands to @value{GDBN}
1254 * Completion:: Command completion
1255 * Help:: How to ask @value{GDBN} for help
1258 @node Command Syntax
1259 @section Command syntax
1261 A @value{GDBN} command is a single line of input. There is no limit on
1262 how long it can be. It starts with a command name, which is followed by
1263 arguments whose meaning depends on the command name. For example, the
1264 command @code{step} accepts an argument which is the number of times to
1265 step, as in @samp{step 5}. You can also use the @code{step} command
1266 with no arguments. Some commands do not allow any arguments.
1268 @cindex abbreviation
1269 @value{GDBN} command names may always be truncated if that abbreviation is
1270 unambiguous. Other possible command abbreviations are listed in the
1271 documentation for individual commands. In some cases, even ambiguous
1272 abbreviations are allowed; for example, @code{s} is specially defined as
1273 equivalent to @code{step} even though there are other commands whose
1274 names start with @code{s}. You can test abbreviations by using them as
1275 arguments to the @code{help} command.
1277 @cindex repeating commands
1278 @kindex RET @r{(repeat last command)}
1279 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1280 repeat the previous command. Certain commands (for example, @code{run})
1281 will not repeat this way; these are commands whose unintentional
1282 repetition might cause trouble and which you are unlikely to want to
1285 The @code{list} and @code{x} commands, when you repeat them with
1286 @key{RET}, construct new arguments rather than repeating
1287 exactly as typed. This permits easy scanning of source or memory.
1289 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1290 output, in a way similar to the common utility @code{more}
1291 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1292 @key{RET} too many in this situation, @value{GDBN} disables command
1293 repetition after any command that generates this sort of display.
1295 @kindex # @r{(a comment)}
1297 Any text from a @kbd{#} to the end of the line is a comment; it does
1298 nothing. This is useful mainly in command files (@pxref{Command
1299 Files,,Command files}).
1301 @cindex repeating command sequences
1302 @kindex C-o @r{(operate-and-get-next)}
1303 The @kbd{C-o} binding is useful for repeating a complex sequence of
1304 commands. This command accepts the current line, like @kbd{RET}, and
1305 then fetches the next line relative to the current line from the history
1309 @section Command completion
1312 @cindex word completion
1313 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1314 only one possibility; it can also show you what the valid possibilities
1315 are for the next word in a command, at any time. This works for @value{GDBN}
1316 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1318 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1319 of a word. If there is only one possibility, @value{GDBN} fills in the
1320 word, and waits for you to finish the command (or press @key{RET} to
1321 enter it). For example, if you type
1323 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1324 @c complete accuracy in these examples; space introduced for clarity.
1325 @c If texinfo enhancements make it unnecessary, it would be nice to
1326 @c replace " @key" by "@key" in the following...
1328 (@value{GDBP}) info bre @key{TAB}
1332 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1333 the only @code{info} subcommand beginning with @samp{bre}:
1336 (@value{GDBP}) info breakpoints
1340 You can either press @key{RET} at this point, to run the @code{info
1341 breakpoints} command, or backspace and enter something else, if
1342 @samp{breakpoints} does not look like the command you expected. (If you
1343 were sure you wanted @code{info breakpoints} in the first place, you
1344 might as well just type @key{RET} immediately after @samp{info bre},
1345 to exploit command abbreviations rather than command completion).
1347 If there is more than one possibility for the next word when you press
1348 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1349 characters and try again, or just press @key{TAB} a second time;
1350 @value{GDBN} displays all the possible completions for that word. For
1351 example, you might want to set a breakpoint on a subroutine whose name
1352 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1353 just sounds the bell. Typing @key{TAB} again displays all the
1354 function names in your program that begin with those characters, for
1358 (@value{GDBP}) b make_ @key{TAB}
1359 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1360 make_a_section_from_file make_environ
1361 make_abs_section make_function_type
1362 make_blockvector make_pointer_type
1363 make_cleanup make_reference_type
1364 make_command make_symbol_completion_list
1365 (@value{GDBP}) b make_
1369 After displaying the available possibilities, @value{GDBN} copies your
1370 partial input (@samp{b make_} in the example) so you can finish the
1373 If you just want to see the list of alternatives in the first place, you
1374 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1375 means @kbd{@key{META} ?}. You can type this either by holding down a
1376 key designated as the @key{META} shift on your keyboard (if there is
1377 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1379 @cindex quotes in commands
1380 @cindex completion of quoted strings
1381 Sometimes the string you need, while logically a ``word'', may contain
1382 parentheses or other characters that @value{GDBN} normally excludes from
1383 its notion of a word. To permit word completion to work in this
1384 situation, you may enclose words in @code{'} (single quote marks) in
1385 @value{GDBN} commands.
1387 The most likely situation where you might need this is in typing the
1388 name of a C@t{++} function. This is because C@t{++} allows function
1389 overloading (multiple definitions of the same function, distinguished
1390 by argument type). For example, when you want to set a breakpoint you
1391 may need to distinguish whether you mean the version of @code{name}
1392 that takes an @code{int} parameter, @code{name(int)}, or the version
1393 that takes a @code{float} parameter, @code{name(float)}. To use the
1394 word-completion facilities in this situation, type a single quote
1395 @code{'} at the beginning of the function name. This alerts
1396 @value{GDBN} that it may need to consider more information than usual
1397 when you press @key{TAB} or @kbd{M-?} to request word completion:
1400 (@value{GDBP}) b 'bubble( @kbd{M-?}
1401 bubble(double,double) bubble(int,int)
1402 (@value{GDBP}) b 'bubble(
1405 In some cases, @value{GDBN} can tell that completing a name requires using
1406 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1407 completing as much as it can) if you do not type the quote in the first
1411 (@value{GDBP}) b bub @key{TAB}
1412 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1413 (@value{GDBP}) b 'bubble(
1417 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1418 you have not yet started typing the argument list when you ask for
1419 completion on an overloaded symbol.
1421 For more information about overloaded functions, see @ref{C plus plus
1422 expressions, ,C@t{++} expressions}. You can use the command @code{set
1423 overload-resolution off} to disable overload resolution;
1424 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1428 @section Getting help
1429 @cindex online documentation
1432 You can always ask @value{GDBN} itself for information on its commands,
1433 using the command @code{help}.
1436 @kindex h @r{(@code{help})}
1439 You can use @code{help} (abbreviated @code{h}) with no arguments to
1440 display a short list of named classes of commands:
1444 List of classes of commands:
1446 aliases -- Aliases of other commands
1447 breakpoints -- Making program stop at certain points
1448 data -- Examining data
1449 files -- Specifying and examining files
1450 internals -- Maintenance commands
1451 obscure -- Obscure features
1452 running -- Running the program
1453 stack -- Examining the stack
1454 status -- Status inquiries
1455 support -- Support facilities
1456 tracepoints -- Tracing of program execution without@*
1457 stopping the program
1458 user-defined -- User-defined commands
1460 Type "help" followed by a class name for a list of
1461 commands in that class.
1462 Type "help" followed by command name for full
1464 Command name abbreviations are allowed if unambiguous.
1467 @c the above line break eliminates huge line overfull...
1469 @item help @var{class}
1470 Using one of the general help classes as an argument, you can get a
1471 list of the individual commands in that class. For example, here is the
1472 help display for the class @code{status}:
1475 (@value{GDBP}) help status
1480 @c Line break in "show" line falsifies real output, but needed
1481 @c to fit in smallbook page size.
1482 info -- Generic command for showing things
1483 about the program being debugged
1484 show -- Generic command for showing things
1487 Type "help" followed by command name for full
1489 Command name abbreviations are allowed if unambiguous.
1493 @item help @var{command}
1494 With a command name as @code{help} argument, @value{GDBN} displays a
1495 short paragraph on how to use that command.
1498 @item apropos @var{args}
1499 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1500 commands, and their documentation, for the regular expression specified in
1501 @var{args}. It prints out all matches found. For example:
1512 set symbol-reloading -- Set dynamic symbol table reloading
1513 multiple times in one run
1514 show symbol-reloading -- Show dynamic symbol table reloading
1515 multiple times in one run
1520 @item complete @var{args}
1521 The @code{complete @var{args}} command lists all the possible completions
1522 for the beginning of a command. Use @var{args} to specify the beginning of the
1523 command you want completed. For example:
1529 @noindent results in:
1540 @noindent This is intended for use by @sc{gnu} Emacs.
1543 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1544 and @code{show} to inquire about the state of your program, or the state
1545 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1546 manual introduces each of them in the appropriate context. The listings
1547 under @code{info} and under @code{show} in the Index point to
1548 all the sub-commands. @xref{Index}.
1553 @kindex i @r{(@code{info})}
1555 This command (abbreviated @code{i}) is for describing the state of your
1556 program. For example, you can list the arguments given to your program
1557 with @code{info args}, list the registers currently in use with @code{info
1558 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1559 You can get a complete list of the @code{info} sub-commands with
1560 @w{@code{help info}}.
1564 You can assign the result of an expression to an environment variable with
1565 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1566 @code{set prompt $}.
1570 In contrast to @code{info}, @code{show} is for describing the state of
1571 @value{GDBN} itself.
1572 You can change most of the things you can @code{show}, by using the
1573 related command @code{set}; for example, you can control what number
1574 system is used for displays with @code{set radix}, or simply inquire
1575 which is currently in use with @code{show radix}.
1578 To display all the settable parameters and their current
1579 values, you can use @code{show} with no arguments; you may also use
1580 @code{info set}. Both commands produce the same display.
1581 @c FIXME: "info set" violates the rule that "info" is for state of
1582 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1583 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1587 Here are three miscellaneous @code{show} subcommands, all of which are
1588 exceptional in lacking corresponding @code{set} commands:
1591 @kindex show version
1592 @cindex version number
1594 Show what version of @value{GDBN} is running. You should include this
1595 information in @value{GDBN} bug-reports. If multiple versions of
1596 @value{GDBN} are in use at your site, you may need to determine which
1597 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1598 commands are introduced, and old ones may wither away. Also, many
1599 system vendors ship variant versions of @value{GDBN}, and there are
1600 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1601 The version number is the same as the one announced when you start
1604 @kindex show copying
1606 Display information about permission for copying @value{GDBN}.
1608 @kindex show warranty
1610 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1611 if your version of @value{GDBN} comes with one.
1616 @chapter Running Programs Under @value{GDBN}
1618 When you run a program under @value{GDBN}, you must first generate
1619 debugging information when you compile it.
1621 You may start @value{GDBN} with its arguments, if any, in an environment
1622 of your choice. If you are doing native debugging, you may redirect
1623 your program's input and output, debug an already running process, or
1624 kill a child process.
1627 * Compilation:: Compiling for debugging
1628 * Starting:: Starting your program
1629 * Arguments:: Your program's arguments
1630 * Environment:: Your program's environment
1632 * Working Directory:: Your program's working directory
1633 * Input/Output:: Your program's input and output
1634 * Attach:: Debugging an already-running process
1635 * Kill Process:: Killing the child process
1637 * Threads:: Debugging programs with multiple threads
1638 * Processes:: Debugging programs with multiple processes
1642 @section Compiling for debugging
1644 In order to debug a program effectively, you need to generate
1645 debugging information when you compile it. This debugging information
1646 is stored in the object file; it describes the data type of each
1647 variable or function and the correspondence between source line numbers
1648 and addresses in the executable code.
1650 To request debugging information, specify the @samp{-g} option when you run
1653 Most compilers do not include information about preprocessor macros in
1654 the debugging information if you specify the @option{-g} flag alone,
1655 because this information is rather large. Version 3.1 of @value{NGCC},
1656 the @sc{gnu} C compiler, provides macro information if you specify the
1657 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1658 debugging information in the Dwarf 2 format, and the latter requests
1659 ``extra information''. In the future, we hope to find more compact ways
1660 to represent macro information, so that it can be included with
1663 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1664 options together. Using those compilers, you cannot generate optimized
1665 executables containing debugging information.
1667 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1668 without @samp{-O}, making it possible to debug optimized code. We
1669 recommend that you @emph{always} use @samp{-g} whenever you compile a
1670 program. You may think your program is correct, but there is no sense
1671 in pushing your luck.
1673 @cindex optimized code, debugging
1674 @cindex debugging optimized code
1675 When you debug a program compiled with @samp{-g -O}, remember that the
1676 optimizer is rearranging your code; the debugger shows you what is
1677 really there. Do not be too surprised when the execution path does not
1678 exactly match your source file! An extreme example: if you define a
1679 variable, but never use it, @value{GDBN} never sees that
1680 variable---because the compiler optimizes it out of existence.
1682 Some things do not work as well with @samp{-g -O} as with just
1683 @samp{-g}, particularly on machines with instruction scheduling. If in
1684 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1685 please report it to us as a bug (including a test case!).
1687 Older versions of the @sc{gnu} C compiler permitted a variant option
1688 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1689 format; if your @sc{gnu} C compiler has this option, do not use it.
1693 @section Starting your program
1699 @kindex r @r{(@code{run})}
1702 Use the @code{run} command to start your program under @value{GDBN}.
1703 You must first specify the program name (except on VxWorks) with an
1704 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1705 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1706 (@pxref{Files, ,Commands to specify files}).
1710 If you are running your program in an execution environment that
1711 supports processes, @code{run} creates an inferior process and makes
1712 that process run your program. (In environments without processes,
1713 @code{run} jumps to the start of your program.)
1715 The execution of a program is affected by certain information it
1716 receives from its superior. @value{GDBN} provides ways to specify this
1717 information, which you must do @emph{before} starting your program. (You
1718 can change it after starting your program, but such changes only affect
1719 your program the next time you start it.) This information may be
1720 divided into four categories:
1723 @item The @emph{arguments.}
1724 Specify the arguments to give your program as the arguments of the
1725 @code{run} command. If a shell is available on your target, the shell
1726 is used to pass the arguments, so that you may use normal conventions
1727 (such as wildcard expansion or variable substitution) in describing
1729 In Unix systems, you can control which shell is used with the
1730 @code{SHELL} environment variable.
1731 @xref{Arguments, ,Your program's arguments}.
1733 @item The @emph{environment.}
1734 Your program normally inherits its environment from @value{GDBN}, but you can
1735 use the @value{GDBN} commands @code{set environment} and @code{unset
1736 environment} to change parts of the environment that affect
1737 your program. @xref{Environment, ,Your program's environment}.
1739 @item The @emph{working directory.}
1740 Your program inherits its working directory from @value{GDBN}. You can set
1741 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1742 @xref{Working Directory, ,Your program's working directory}.
1744 @item The @emph{standard input and output.}
1745 Your program normally uses the same device for standard input and
1746 standard output as @value{GDBN} is using. You can redirect input and output
1747 in the @code{run} command line, or you can use the @code{tty} command to
1748 set a different device for your program.
1749 @xref{Input/Output, ,Your program's input and output}.
1752 @emph{Warning:} While input and output redirection work, you cannot use
1753 pipes to pass the output of the program you are debugging to another
1754 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1758 When you issue the @code{run} command, your program begins to execute
1759 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1760 of how to arrange for your program to stop. Once your program has
1761 stopped, you may call functions in your program, using the @code{print}
1762 or @code{call} commands. @xref{Data, ,Examining Data}.
1764 If the modification time of your symbol file has changed since the last
1765 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1766 table, and reads it again. When it does this, @value{GDBN} tries to retain
1767 your current breakpoints.
1770 @section Your program's arguments
1772 @cindex arguments (to your program)
1773 The arguments to your program can be specified by the arguments of the
1775 They are passed to a shell, which expands wildcard characters and
1776 performs redirection of I/O, and thence to your program. Your
1777 @code{SHELL} environment variable (if it exists) specifies what shell
1778 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1779 the default shell (@file{/bin/sh} on Unix).
1781 On non-Unix systems, the program is usually invoked directly by
1782 @value{GDBN}, which emulates I/O redirection via the appropriate system
1783 calls, and the wildcard characters are expanded by the startup code of
1784 the program, not by the shell.
1786 @code{run} with no arguments uses the same arguments used by the previous
1787 @code{run}, or those set by the @code{set args} command.
1792 Specify the arguments to be used the next time your program is run. If
1793 @code{set args} has no arguments, @code{run} executes your program
1794 with no arguments. Once you have run your program with arguments,
1795 using @code{set args} before the next @code{run} is the only way to run
1796 it again without arguments.
1800 Show the arguments to give your program when it is started.
1804 @section Your program's environment
1806 @cindex environment (of your program)
1807 The @dfn{environment} consists of a set of environment variables and
1808 their values. Environment variables conventionally record such things as
1809 your user name, your home directory, your terminal type, and your search
1810 path for programs to run. Usually you set up environment variables with
1811 the shell and they are inherited by all the other programs you run. When
1812 debugging, it can be useful to try running your program with a modified
1813 environment without having to start @value{GDBN} over again.
1817 @item path @var{directory}
1818 Add @var{directory} to the front of the @code{PATH} environment variable
1819 (the search path for executables) that will be passed to your program.
1820 The value of @code{PATH} used by @value{GDBN} does not change.
1821 You may specify several directory names, separated by whitespace or by a
1822 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1823 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1824 is moved to the front, so it is searched sooner.
1826 You can use the string @samp{$cwd} to refer to whatever is the current
1827 working directory at the time @value{GDBN} searches the path. If you
1828 use @samp{.} instead, it refers to the directory where you executed the
1829 @code{path} command. @value{GDBN} replaces @samp{.} in the
1830 @var{directory} argument (with the current path) before adding
1831 @var{directory} to the search path.
1832 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1833 @c document that, since repeating it would be a no-op.
1837 Display the list of search paths for executables (the @code{PATH}
1838 environment variable).
1840 @kindex show environment
1841 @item show environment @r{[}@var{varname}@r{]}
1842 Print the value of environment variable @var{varname} to be given to
1843 your program when it starts. If you do not supply @var{varname},
1844 print the names and values of all environment variables to be given to
1845 your program. You can abbreviate @code{environment} as @code{env}.
1847 @kindex set environment
1848 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1849 Set environment variable @var{varname} to @var{value}. The value
1850 changes for your program only, not for @value{GDBN} itself. @var{value} may
1851 be any string; the values of environment variables are just strings, and
1852 any interpretation is supplied by your program itself. The @var{value}
1853 parameter is optional; if it is eliminated, the variable is set to a
1855 @c "any string" here does not include leading, trailing
1856 @c blanks. Gnu asks: does anyone care?
1858 For example, this command:
1865 tells the debugged program, when subsequently run, that its user is named
1866 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1867 are not actually required.)
1869 @kindex unset environment
1870 @item unset environment @var{varname}
1871 Remove variable @var{varname} from the environment to be passed to your
1872 program. This is different from @samp{set env @var{varname} =};
1873 @code{unset environment} removes the variable from the environment,
1874 rather than assigning it an empty value.
1877 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1879 by your @code{SHELL} environment variable if it exists (or
1880 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1881 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1882 @file{.bashrc} for BASH---any variables you set in that file affect
1883 your program. You may wish to move setting of environment variables to
1884 files that are only run when you sign on, such as @file{.login} or
1887 @node Working Directory
1888 @section Your program's working directory
1890 @cindex working directory (of your program)
1891 Each time you start your program with @code{run}, it inherits its
1892 working directory from the current working directory of @value{GDBN}.
1893 The @value{GDBN} working directory is initially whatever it inherited
1894 from its parent process (typically the shell), but you can specify a new
1895 working directory in @value{GDBN} with the @code{cd} command.
1897 The @value{GDBN} working directory also serves as a default for the commands
1898 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1903 @item cd @var{directory}
1904 Set the @value{GDBN} working directory to @var{directory}.
1908 Print the @value{GDBN} working directory.
1912 @section Your program's input and output
1917 By default, the program you run under @value{GDBN} does input and output to
1918 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1919 to its own terminal modes to interact with you, but it records the terminal
1920 modes your program was using and switches back to them when you continue
1921 running your program.
1924 @kindex info terminal
1926 Displays information recorded by @value{GDBN} about the terminal modes your
1930 You can redirect your program's input and/or output using shell
1931 redirection with the @code{run} command. For example,
1938 starts your program, diverting its output to the file @file{outfile}.
1941 @cindex controlling terminal
1942 Another way to specify where your program should do input and output is
1943 with the @code{tty} command. This command accepts a file name as
1944 argument, and causes this file to be the default for future @code{run}
1945 commands. It also resets the controlling terminal for the child
1946 process, for future @code{run} commands. For example,
1953 directs that processes started with subsequent @code{run} commands
1954 default to do input and output on the terminal @file{/dev/ttyb} and have
1955 that as their controlling terminal.
1957 An explicit redirection in @code{run} overrides the @code{tty} command's
1958 effect on the input/output device, but not its effect on the controlling
1961 When you use the @code{tty} command or redirect input in the @code{run}
1962 command, only the input @emph{for your program} is affected. The input
1963 for @value{GDBN} still comes from your terminal.
1966 @section Debugging an already-running process
1971 @item attach @var{process-id}
1972 This command attaches to a running process---one that was started
1973 outside @value{GDBN}. (@code{info files} shows your active
1974 targets.) The command takes as argument a process ID. The usual way to
1975 find out the process-id of a Unix process is with the @code{ps} utility,
1976 or with the @samp{jobs -l} shell command.
1978 @code{attach} does not repeat if you press @key{RET} a second time after
1979 executing the command.
1982 To use @code{attach}, your program must be running in an environment
1983 which supports processes; for example, @code{attach} does not work for
1984 programs on bare-board targets that lack an operating system. You must
1985 also have permission to send the process a signal.
1987 When you use @code{attach}, the debugger finds the program running in
1988 the process first by looking in the current working directory, then (if
1989 the program is not found) by using the source file search path
1990 (@pxref{Source Path, ,Specifying source directories}). You can also use
1991 the @code{file} command to load the program. @xref{Files, ,Commands to
1994 The first thing @value{GDBN} does after arranging to debug the specified
1995 process is to stop it. You can examine and modify an attached process
1996 with all the @value{GDBN} commands that are ordinarily available when
1997 you start processes with @code{run}. You can insert breakpoints; you
1998 can step and continue; you can modify storage. If you would rather the
1999 process continue running, you may use the @code{continue} command after
2000 attaching @value{GDBN} to the process.
2005 When you have finished debugging the attached process, you can use the
2006 @code{detach} command to release it from @value{GDBN} control. Detaching
2007 the process continues its execution. After the @code{detach} command,
2008 that process and @value{GDBN} become completely independent once more, and you
2009 are ready to @code{attach} another process or start one with @code{run}.
2010 @code{detach} does not repeat if you press @key{RET} again after
2011 executing the command.
2014 If you exit @value{GDBN} or use the @code{run} command while you have an
2015 attached process, you kill that process. By default, @value{GDBN} asks
2016 for confirmation if you try to do either of these things; you can
2017 control whether or not you need to confirm by using the @code{set
2018 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2022 @section Killing the child process
2027 Kill the child process in which your program is running under @value{GDBN}.
2030 This command is useful if you wish to debug a core dump instead of a
2031 running process. @value{GDBN} ignores any core dump file while your program
2034 On some operating systems, a program cannot be executed outside @value{GDBN}
2035 while you have breakpoints set on it inside @value{GDBN}. You can use the
2036 @code{kill} command in this situation to permit running your program
2037 outside the debugger.
2039 The @code{kill} command is also useful if you wish to recompile and
2040 relink your program, since on many systems it is impossible to modify an
2041 executable file while it is running in a process. In this case, when you
2042 next type @code{run}, @value{GDBN} notices that the file has changed, and
2043 reads the symbol table again (while trying to preserve your current
2044 breakpoint settings).
2047 @section Debugging programs with multiple threads
2049 @cindex threads of execution
2050 @cindex multiple threads
2051 @cindex switching threads
2052 In some operating systems, such as HP-UX and Solaris, a single program
2053 may have more than one @dfn{thread} of execution. The precise semantics
2054 of threads differ from one operating system to another, but in general
2055 the threads of a single program are akin to multiple processes---except
2056 that they share one address space (that is, they can all examine and
2057 modify the same variables). On the other hand, each thread has its own
2058 registers and execution stack, and perhaps private memory.
2060 @value{GDBN} provides these facilities for debugging multi-thread
2064 @item automatic notification of new threads
2065 @item @samp{thread @var{threadno}}, a command to switch among threads
2066 @item @samp{info threads}, a command to inquire about existing threads
2067 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2068 a command to apply a command to a list of threads
2069 @item thread-specific breakpoints
2073 @emph{Warning:} These facilities are not yet available on every
2074 @value{GDBN} configuration where the operating system supports threads.
2075 If your @value{GDBN} does not support threads, these commands have no
2076 effect. For example, a system without thread support shows no output
2077 from @samp{info threads}, and always rejects the @code{thread} command,
2081 (@value{GDBP}) info threads
2082 (@value{GDBP}) thread 1
2083 Thread ID 1 not known. Use the "info threads" command to
2084 see the IDs of currently known threads.
2086 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2087 @c doesn't support threads"?
2090 @cindex focus of debugging
2091 @cindex current thread
2092 The @value{GDBN} thread debugging facility allows you to observe all
2093 threads while your program runs---but whenever @value{GDBN} takes
2094 control, one thread in particular is always the focus of debugging.
2095 This thread is called the @dfn{current thread}. Debugging commands show
2096 program information from the perspective of the current thread.
2098 @cindex @code{New} @var{systag} message
2099 @cindex thread identifier (system)
2100 @c FIXME-implementors!! It would be more helpful if the [New...] message
2101 @c included GDB's numeric thread handle, so you could just go to that
2102 @c thread without first checking `info threads'.
2103 Whenever @value{GDBN} detects a new thread in your program, it displays
2104 the target system's identification for the thread with a message in the
2105 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2106 whose form varies depending on the particular system. For example, on
2107 LynxOS, you might see
2110 [New process 35 thread 27]
2114 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2115 the @var{systag} is simply something like @samp{process 368}, with no
2118 @c FIXME!! (1) Does the [New...] message appear even for the very first
2119 @c thread of a program, or does it only appear for the
2120 @c second---i.e.@: when it becomes obvious we have a multithread
2122 @c (2) *Is* there necessarily a first thread always? Or do some
2123 @c multithread systems permit starting a program with multiple
2124 @c threads ab initio?
2126 @cindex thread number
2127 @cindex thread identifier (GDB)
2128 For debugging purposes, @value{GDBN} associates its own thread
2129 number---always a single integer---with each thread in your program.
2132 @kindex info threads
2134 Display a summary of all threads currently in your
2135 program. @value{GDBN} displays for each thread (in this order):
2138 @item the thread number assigned by @value{GDBN}
2140 @item the target system's thread identifier (@var{systag})
2142 @item the current stack frame summary for that thread
2146 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2147 indicates the current thread.
2151 @c end table here to get a little more width for example
2154 (@value{GDBP}) info threads
2155 3 process 35 thread 27 0x34e5 in sigpause ()
2156 2 process 35 thread 23 0x34e5 in sigpause ()
2157 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2163 @cindex thread number
2164 @cindex thread identifier (GDB)
2165 For debugging purposes, @value{GDBN} associates its own thread
2166 number---a small integer assigned in thread-creation order---with each
2167 thread in your program.
2169 @cindex @code{New} @var{systag} message, on HP-UX
2170 @cindex thread identifier (system), on HP-UX
2171 @c FIXME-implementors!! It would be more helpful if the [New...] message
2172 @c included GDB's numeric thread handle, so you could just go to that
2173 @c thread without first checking `info threads'.
2174 Whenever @value{GDBN} detects a new thread in your program, it displays
2175 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2176 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2177 whose form varies depending on the particular system. For example, on
2181 [New thread 2 (system thread 26594)]
2185 when @value{GDBN} notices a new thread.
2188 @kindex info threads
2190 Display a summary of all threads currently in your
2191 program. @value{GDBN} displays for each thread (in this order):
2194 @item the thread number assigned by @value{GDBN}
2196 @item the target system's thread identifier (@var{systag})
2198 @item the current stack frame summary for that thread
2202 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2203 indicates the current thread.
2207 @c end table here to get a little more width for example
2210 (@value{GDBP}) info threads
2211 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2213 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2214 from /usr/lib/libc.2
2215 1 system thread 27905 0x7b003498 in _brk () \@*
2216 from /usr/lib/libc.2
2220 @kindex thread @var{threadno}
2221 @item thread @var{threadno}
2222 Make thread number @var{threadno} the current thread. The command
2223 argument @var{threadno} is the internal @value{GDBN} thread number, as
2224 shown in the first field of the @samp{info threads} display.
2225 @value{GDBN} responds by displaying the system identifier of the thread
2226 you selected, and its current stack frame summary:
2229 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2230 (@value{GDBP}) thread 2
2231 [Switching to process 35 thread 23]
2232 0x34e5 in sigpause ()
2236 As with the @samp{[New @dots{}]} message, the form of the text after
2237 @samp{Switching to} depends on your system's conventions for identifying
2240 @kindex thread apply
2241 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2242 The @code{thread apply} command allows you to apply a command to one or
2243 more threads. Specify the numbers of the threads that you want affected
2244 with the command argument @var{threadno}. @var{threadno} is the internal
2245 @value{GDBN} thread number, as shown in the first field of the @samp{info
2246 threads} display. To apply a command to all threads, use
2247 @code{thread apply all} @var{args}.
2250 @cindex automatic thread selection
2251 @cindex switching threads automatically
2252 @cindex threads, automatic switching
2253 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2254 signal, it automatically selects the thread where that breakpoint or
2255 signal happened. @value{GDBN} alerts you to the context switch with a
2256 message of the form @samp{[Switching to @var{systag}]} to identify the
2259 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2260 more information about how @value{GDBN} behaves when you stop and start
2261 programs with multiple threads.
2263 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2264 watchpoints in programs with multiple threads.
2267 @section Debugging programs with multiple processes
2269 @cindex fork, debugging programs which call
2270 @cindex multiple processes
2271 @cindex processes, multiple
2272 On most systems, @value{GDBN} has no special support for debugging
2273 programs which create additional processes using the @code{fork}
2274 function. When a program forks, @value{GDBN} will continue to debug the
2275 parent process and the child process will run unimpeded. If you have
2276 set a breakpoint in any code which the child then executes, the child
2277 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2278 will cause it to terminate.
2280 However, if you want to debug the child process there is a workaround
2281 which isn't too painful. Put a call to @code{sleep} in the code which
2282 the child process executes after the fork. It may be useful to sleep
2283 only if a certain environment variable is set, or a certain file exists,
2284 so that the delay need not occur when you don't want to run @value{GDBN}
2285 on the child. While the child is sleeping, use the @code{ps} program to
2286 get its process ID. Then tell @value{GDBN} (a new invocation of
2287 @value{GDBN} if you are also debugging the parent process) to attach to
2288 the child process (@pxref{Attach}). From that point on you can debug
2289 the child process just like any other process which you attached to.
2291 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2292 debugging programs that create additional processes using the
2293 @code{fork} or @code{vfork} function.
2295 By default, when a program forks, @value{GDBN} will continue to debug
2296 the parent process and the child process will run unimpeded.
2298 If you want to follow the child process instead of the parent process,
2299 use the command @w{@code{set follow-fork-mode}}.
2302 @kindex set follow-fork-mode
2303 @item set follow-fork-mode @var{mode}
2304 Set the debugger response to a program call of @code{fork} or
2305 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2306 process. The @var{mode} can be:
2310 The original process is debugged after a fork. The child process runs
2311 unimpeded. This is the default.
2314 The new process is debugged after a fork. The parent process runs
2318 The debugger will ask for one of the above choices.
2321 @item show follow-fork-mode
2322 Display the current debugger response to a @code{fork} or @code{vfork} call.
2325 If you ask to debug a child process and a @code{vfork} is followed by an
2326 @code{exec}, @value{GDBN} executes the new target up to the first
2327 breakpoint in the new target. If you have a breakpoint set on
2328 @code{main} in your original program, the breakpoint will also be set on
2329 the child process's @code{main}.
2331 When a child process is spawned by @code{vfork}, you cannot debug the
2332 child or parent until an @code{exec} call completes.
2334 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2335 call executes, the new target restarts. To restart the parent process,
2336 use the @code{file} command with the parent executable name as its
2339 You can use the @code{catch} command to make @value{GDBN} stop whenever
2340 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2341 Catchpoints, ,Setting catchpoints}.
2344 @chapter Stopping and Continuing
2346 The principal purposes of using a debugger are so that you can stop your
2347 program before it terminates; or so that, if your program runs into
2348 trouble, you can investigate and find out why.
2350 Inside @value{GDBN}, your program may stop for any of several reasons,
2351 such as a signal, a breakpoint, or reaching a new line after a
2352 @value{GDBN} command such as @code{step}. You may then examine and
2353 change variables, set new breakpoints or remove old ones, and then
2354 continue execution. Usually, the messages shown by @value{GDBN} provide
2355 ample explanation of the status of your program---but you can also
2356 explicitly request this information at any time.
2359 @kindex info program
2361 Display information about the status of your program: whether it is
2362 running or not, what process it is, and why it stopped.
2366 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2367 * Continuing and Stepping:: Resuming execution
2369 * Thread Stops:: Stopping and starting multi-thread programs
2373 @section Breakpoints, watchpoints, and catchpoints
2376 A @dfn{breakpoint} makes your program stop whenever a certain point in
2377 the program is reached. For each breakpoint, you can add conditions to
2378 control in finer detail whether your program stops. You can set
2379 breakpoints with the @code{break} command and its variants (@pxref{Set
2380 Breaks, ,Setting breakpoints}), to specify the place where your program
2381 should stop by line number, function name or exact address in the
2384 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2385 breakpoints in shared libraries before the executable is run. There is
2386 a minor limitation on HP-UX systems: you must wait until the executable
2387 is run in order to set breakpoints in shared library routines that are
2388 not called directly by the program (for example, routines that are
2389 arguments in a @code{pthread_create} call).
2392 @cindex memory tracing
2393 @cindex breakpoint on memory address
2394 @cindex breakpoint on variable modification
2395 A @dfn{watchpoint} is a special breakpoint that stops your program
2396 when the value of an expression changes. You must use a different
2397 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2398 watchpoints}), but aside from that, you can manage a watchpoint like
2399 any other breakpoint: you enable, disable, and delete both breakpoints
2400 and watchpoints using the same commands.
2402 You can arrange to have values from your program displayed automatically
2403 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2407 @cindex breakpoint on events
2408 A @dfn{catchpoint} is another special breakpoint that stops your program
2409 when a certain kind of event occurs, such as the throwing of a C@t{++}
2410 exception or the loading of a library. As with watchpoints, you use a
2411 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2412 catchpoints}), but aside from that, you can manage a catchpoint like any
2413 other breakpoint. (To stop when your program receives a signal, use the
2414 @code{handle} command; see @ref{Signals, ,Signals}.)
2416 @cindex breakpoint numbers
2417 @cindex numbers for breakpoints
2418 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2419 catchpoint when you create it; these numbers are successive integers
2420 starting with one. In many of the commands for controlling various
2421 features of breakpoints you use the breakpoint number to say which
2422 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2423 @dfn{disabled}; if disabled, it has no effect on your program until you
2426 @cindex breakpoint ranges
2427 @cindex ranges of breakpoints
2428 Some @value{GDBN} commands accept a range of breakpoints on which to
2429 operate. A breakpoint range is either a single breakpoint number, like
2430 @samp{5}, or two such numbers, in increasing order, separated by a
2431 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2432 all breakpoint in that range are operated on.
2435 * Set Breaks:: Setting breakpoints
2436 * Set Watchpoints:: Setting watchpoints
2437 * Set Catchpoints:: Setting catchpoints
2438 * Delete Breaks:: Deleting breakpoints
2439 * Disabling:: Disabling breakpoints
2440 * Conditions:: Break conditions
2441 * Break Commands:: Breakpoint command lists
2442 * Breakpoint Menus:: Breakpoint menus
2443 * Error in Breakpoints:: ``Cannot insert breakpoints''
2447 @subsection Setting breakpoints
2449 @c FIXME LMB what does GDB do if no code on line of breakpt?
2450 @c consider in particular declaration with/without initialization.
2452 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2455 @kindex b @r{(@code{break})}
2456 @vindex $bpnum@r{, convenience variable}
2457 @cindex latest breakpoint
2458 Breakpoints are set with the @code{break} command (abbreviated
2459 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2460 number of the breakpoint you've set most recently; see @ref{Convenience
2461 Vars,, Convenience variables}, for a discussion of what you can do with
2462 convenience variables.
2464 You have several ways to say where the breakpoint should go.
2467 @item break @var{function}
2468 Set a breakpoint at entry to function @var{function}.
2469 When using source languages that permit overloading of symbols, such as
2470 C@t{++}, @var{function} may refer to more than one possible place to break.
2471 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2473 @item break +@var{offset}
2474 @itemx break -@var{offset}
2475 Set a breakpoint some number of lines forward or back from the position
2476 at which execution stopped in the currently selected @dfn{stack frame}.
2477 (@xref{Frames, ,Frames}, for a description of stack frames.)
2479 @item break @var{linenum}
2480 Set a breakpoint at line @var{linenum} in the current source file.
2481 The current source file is the last file whose source text was printed.
2482 The breakpoint will stop your program just before it executes any of the
2485 @item break @var{filename}:@var{linenum}
2486 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2488 @item break @var{filename}:@var{function}
2489 Set a breakpoint at entry to function @var{function} found in file
2490 @var{filename}. Specifying a file name as well as a function name is
2491 superfluous except when multiple files contain similarly named
2494 @item break *@var{address}
2495 Set a breakpoint at address @var{address}. You can use this to set
2496 breakpoints in parts of your program which do not have debugging
2497 information or source files.
2500 When called without any arguments, @code{break} sets a breakpoint at
2501 the next instruction to be executed in the selected stack frame
2502 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2503 innermost, this makes your program stop as soon as control
2504 returns to that frame. This is similar to the effect of a
2505 @code{finish} command in the frame inside the selected frame---except
2506 that @code{finish} does not leave an active breakpoint. If you use
2507 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2508 the next time it reaches the current location; this may be useful
2511 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2512 least one instruction has been executed. If it did not do this, you
2513 would be unable to proceed past a breakpoint without first disabling the
2514 breakpoint. This rule applies whether or not the breakpoint already
2515 existed when your program stopped.
2517 @item break @dots{} if @var{cond}
2518 Set a breakpoint with condition @var{cond}; evaluate the expression
2519 @var{cond} each time the breakpoint is reached, and stop only if the
2520 value is nonzero---that is, if @var{cond} evaluates as true.
2521 @samp{@dots{}} stands for one of the possible arguments described
2522 above (or no argument) specifying where to break. @xref{Conditions,
2523 ,Break conditions}, for more information on breakpoint conditions.
2526 @item tbreak @var{args}
2527 Set a breakpoint enabled only for one stop. @var{args} are the
2528 same as for the @code{break} command, and the breakpoint is set in the same
2529 way, but the breakpoint is automatically deleted after the first time your
2530 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2533 @item hbreak @var{args}
2534 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2535 @code{break} command and the breakpoint is set in the same way, but the
2536 breakpoint requires hardware support and some target hardware may not
2537 have this support. The main purpose of this is EPROM/ROM code
2538 debugging, so you can set a breakpoint at an instruction without
2539 changing the instruction. This can be used with the new trap-generation
2540 provided by SPARClite DSU and some x86-based targets. These targets
2541 will generate traps when a program accesses some data or instruction
2542 address that is assigned to the debug registers. However the hardware
2543 breakpoint registers can take a limited number of breakpoints. For
2544 example, on the DSU, only two data breakpoints can be set at a time, and
2545 @value{GDBN} will reject this command if more than two are used. Delete
2546 or disable unused hardware breakpoints before setting new ones
2547 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2548 @xref{set remote hardware-breakpoint-limit}.
2552 @item thbreak @var{args}
2553 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2554 are the same as for the @code{hbreak} command and the breakpoint is set in
2555 the same way. However, like the @code{tbreak} command,
2556 the breakpoint is automatically deleted after the
2557 first time your program stops there. Also, like the @code{hbreak}
2558 command, the breakpoint requires hardware support and some target hardware
2559 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2560 See also @ref{Conditions, ,Break conditions}.
2563 @cindex regular expression
2564 @item rbreak @var{regex}
2565 Set breakpoints on all functions matching the regular expression
2566 @var{regex}. This command sets an unconditional breakpoint on all
2567 matches, printing a list of all breakpoints it set. Once these
2568 breakpoints are set, they are treated just like the breakpoints set with
2569 the @code{break} command. You can delete them, disable them, or make
2570 them conditional the same way as any other breakpoint.
2572 The syntax of the regular expression is the standard one used with tools
2573 like @file{grep}. Note that this is different from the syntax used by
2574 shells, so for instance @code{foo*} matches all functions that include
2575 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2576 @code{.*} leading and trailing the regular expression you supply, so to
2577 match only functions that begin with @code{foo}, use @code{^foo}.
2579 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2580 breakpoints on overloaded functions that are not members of any special
2583 @kindex info breakpoints
2584 @cindex @code{$_} and @code{info breakpoints}
2585 @item info breakpoints @r{[}@var{n}@r{]}
2586 @itemx info break @r{[}@var{n}@r{]}
2587 @itemx info watchpoints @r{[}@var{n}@r{]}
2588 Print a table of all breakpoints, watchpoints, and catchpoints set and
2589 not deleted, with the following columns for each breakpoint:
2592 @item Breakpoint Numbers
2594 Breakpoint, watchpoint, or catchpoint.
2596 Whether the breakpoint is marked to be disabled or deleted when hit.
2597 @item Enabled or Disabled
2598 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2599 that are not enabled.
2601 Where the breakpoint is in your program, as a memory address.
2603 Where the breakpoint is in the source for your program, as a file and
2608 If a breakpoint is conditional, @code{info break} shows the condition on
2609 the line following the affected breakpoint; breakpoint commands, if any,
2610 are listed after that.
2613 @code{info break} with a breakpoint
2614 number @var{n} as argument lists only that breakpoint. The
2615 convenience variable @code{$_} and the default examining-address for
2616 the @code{x} command are set to the address of the last breakpoint
2617 listed (@pxref{Memory, ,Examining memory}).
2620 @code{info break} displays a count of the number of times the breakpoint
2621 has been hit. This is especially useful in conjunction with the
2622 @code{ignore} command. You can ignore a large number of breakpoint
2623 hits, look at the breakpoint info to see how many times the breakpoint
2624 was hit, and then run again, ignoring one less than that number. This
2625 will get you quickly to the last hit of that breakpoint.
2628 @value{GDBN} allows you to set any number of breakpoints at the same place in
2629 your program. There is nothing silly or meaningless about this. When
2630 the breakpoints are conditional, this is even useful
2631 (@pxref{Conditions, ,Break conditions}).
2633 @cindex negative breakpoint numbers
2634 @cindex internal @value{GDBN} breakpoints
2635 @value{GDBN} itself sometimes sets breakpoints in your program for
2636 special purposes, such as proper handling of @code{longjmp} (in C
2637 programs). These internal breakpoints are assigned negative numbers,
2638 starting with @code{-1}; @samp{info breakpoints} does not display them.
2639 You can see these breakpoints with the @value{GDBN} maintenance command
2640 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2643 @node Set Watchpoints
2644 @subsection Setting watchpoints
2646 @cindex setting watchpoints
2647 @cindex software watchpoints
2648 @cindex hardware watchpoints
2649 You can use a watchpoint to stop execution whenever the value of an
2650 expression changes, without having to predict a particular place where
2653 Depending on your system, watchpoints may be implemented in software or
2654 hardware. @value{GDBN} does software watchpointing by single-stepping your
2655 program and testing the variable's value each time, which is hundreds of
2656 times slower than normal execution. (But this may still be worth it, to
2657 catch errors where you have no clue what part of your program is the
2660 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2661 @value{GDBN} includes support for
2662 hardware watchpoints, which do not slow down the running of your
2667 @item watch @var{expr}
2668 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2669 is written into by the program and its value changes.
2672 @item rwatch @var{expr}
2673 Set a watchpoint that will break when watch @var{expr} is read by the program.
2676 @item awatch @var{expr}
2677 Set a watchpoint that will break when @var{expr} is either read or written into
2680 @kindex info watchpoints
2681 @item info watchpoints
2682 This command prints a list of watchpoints, breakpoints, and catchpoints;
2683 it is the same as @code{info break}.
2686 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2687 watchpoints execute very quickly, and the debugger reports a change in
2688 value at the exact instruction where the change occurs. If @value{GDBN}
2689 cannot set a hardware watchpoint, it sets a software watchpoint, which
2690 executes more slowly and reports the change in value at the next
2691 statement, not the instruction, after the change occurs.
2693 When you issue the @code{watch} command, @value{GDBN} reports
2696 Hardware watchpoint @var{num}: @var{expr}
2700 if it was able to set a hardware watchpoint.
2702 Currently, the @code{awatch} and @code{rwatch} commands can only set
2703 hardware watchpoints, because accesses to data that don't change the
2704 value of the watched expression cannot be detected without examining
2705 every instruction as it is being executed, and @value{GDBN} does not do
2706 that currently. If @value{GDBN} finds that it is unable to set a
2707 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2708 will print a message like this:
2711 Expression cannot be implemented with read/access watchpoint.
2714 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2715 data type of the watched expression is wider than what a hardware
2716 watchpoint on the target machine can handle. For example, some systems
2717 can only watch regions that are up to 4 bytes wide; on such systems you
2718 cannot set hardware watchpoints for an expression that yields a
2719 double-precision floating-point number (which is typically 8 bytes
2720 wide). As a work-around, it might be possible to break the large region
2721 into a series of smaller ones and watch them with separate watchpoints.
2723 If you set too many hardware watchpoints, @value{GDBN} might be unable
2724 to insert all of them when you resume the execution of your program.
2725 Since the precise number of active watchpoints is unknown until such
2726 time as the program is about to be resumed, @value{GDBN} might not be
2727 able to warn you about this when you set the watchpoints, and the
2728 warning will be printed only when the program is resumed:
2731 Hardware watchpoint @var{num}: Could not insert watchpoint
2735 If this happens, delete or disable some of the watchpoints.
2737 The SPARClite DSU will generate traps when a program accesses some data
2738 or instruction address that is assigned to the debug registers. For the
2739 data addresses, DSU facilitates the @code{watch} command. However the
2740 hardware breakpoint registers can only take two data watchpoints, and
2741 both watchpoints must be the same kind. For example, you can set two
2742 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2743 @strong{or} two with @code{awatch} commands, but you cannot set one
2744 watchpoint with one command and the other with a different command.
2745 @value{GDBN} will reject the command if you try to mix watchpoints.
2746 Delete or disable unused watchpoint commands before setting new ones.
2748 If you call a function interactively using @code{print} or @code{call},
2749 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2750 kind of breakpoint or the call completes.
2752 @value{GDBN} automatically deletes watchpoints that watch local
2753 (automatic) variables, or expressions that involve such variables, when
2754 they go out of scope, that is, when the execution leaves the block in
2755 which these variables were defined. In particular, when the program
2756 being debugged terminates, @emph{all} local variables go out of scope,
2757 and so only watchpoints that watch global variables remain set. If you
2758 rerun the program, you will need to set all such watchpoints again. One
2759 way of doing that would be to set a code breakpoint at the entry to the
2760 @code{main} function and when it breaks, set all the watchpoints.
2763 @cindex watchpoints and threads
2764 @cindex threads and watchpoints
2765 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2766 usefulness. With the current watchpoint implementation, @value{GDBN}
2767 can only watch the value of an expression @emph{in a single thread}. If
2768 you are confident that the expression can only change due to the current
2769 thread's activity (and if you are also confident that no other thread
2770 can become current), then you can use watchpoints as usual. However,
2771 @value{GDBN} may not notice when a non-current thread's activity changes
2774 @c FIXME: this is almost identical to the previous paragraph.
2775 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2776 have only limited usefulness. If @value{GDBN} creates a software
2777 watchpoint, it can only watch the value of an expression @emph{in a
2778 single thread}. If you are confident that the expression can only
2779 change due to the current thread's activity (and if you are also
2780 confident that no other thread can become current), then you can use
2781 software watchpoints as usual. However, @value{GDBN} may not notice
2782 when a non-current thread's activity changes the expression. (Hardware
2783 watchpoints, in contrast, watch an expression in all threads.)
2786 @xref{set remote hardware-watchpoint-limit}.
2788 @node Set Catchpoints
2789 @subsection Setting catchpoints
2790 @cindex catchpoints, setting
2791 @cindex exception handlers
2792 @cindex event handling
2794 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2795 kinds of program events, such as C@t{++} exceptions or the loading of a
2796 shared library. Use the @code{catch} command to set a catchpoint.
2800 @item catch @var{event}
2801 Stop when @var{event} occurs. @var{event} can be any of the following:
2805 The throwing of a C@t{++} exception.
2809 The catching of a C@t{++} exception.
2813 A call to @code{exec}. This is currently only available for HP-UX.
2817 A call to @code{fork}. This is currently only available for HP-UX.
2821 A call to @code{vfork}. This is currently only available for HP-UX.
2824 @itemx load @var{libname}
2826 The dynamic loading of any shared library, or the loading of the library
2827 @var{libname}. This is currently only available for HP-UX.
2830 @itemx unload @var{libname}
2831 @kindex catch unload
2832 The unloading of any dynamically loaded shared library, or the unloading
2833 of the library @var{libname}. This is currently only available for HP-UX.
2836 @item tcatch @var{event}
2837 Set a catchpoint that is enabled only for one stop. The catchpoint is
2838 automatically deleted after the first time the event is caught.
2842 Use the @code{info break} command to list the current catchpoints.
2844 There are currently some limitations to C@t{++} exception handling
2845 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2849 If you call a function interactively, @value{GDBN} normally returns
2850 control to you when the function has finished executing. If the call
2851 raises an exception, however, the call may bypass the mechanism that
2852 returns control to you and cause your program either to abort or to
2853 simply continue running until it hits a breakpoint, catches a signal
2854 that @value{GDBN} is listening for, or exits. This is the case even if
2855 you set a catchpoint for the exception; catchpoints on exceptions are
2856 disabled within interactive calls.
2859 You cannot raise an exception interactively.
2862 You cannot install an exception handler interactively.
2865 @cindex raise exceptions
2866 Sometimes @code{catch} is not the best way to debug exception handling:
2867 if you need to know exactly where an exception is raised, it is better to
2868 stop @emph{before} the exception handler is called, since that way you
2869 can see the stack before any unwinding takes place. If you set a
2870 breakpoint in an exception handler instead, it may not be easy to find
2871 out where the exception was raised.
2873 To stop just before an exception handler is called, you need some
2874 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2875 raised by calling a library function named @code{__raise_exception}
2876 which has the following ANSI C interface:
2879 /* @var{addr} is where the exception identifier is stored.
2880 @var{id} is the exception identifier. */
2881 void __raise_exception (void **addr, void *id);
2885 To make the debugger catch all exceptions before any stack
2886 unwinding takes place, set a breakpoint on @code{__raise_exception}
2887 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2889 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2890 that depends on the value of @var{id}, you can stop your program when
2891 a specific exception is raised. You can use multiple conditional
2892 breakpoints to stop your program when any of a number of exceptions are
2897 @subsection Deleting breakpoints
2899 @cindex clearing breakpoints, watchpoints, catchpoints
2900 @cindex deleting breakpoints, watchpoints, catchpoints
2901 It is often necessary to eliminate a breakpoint, watchpoint, or
2902 catchpoint once it has done its job and you no longer want your program
2903 to stop there. This is called @dfn{deleting} the breakpoint. A
2904 breakpoint that has been deleted no longer exists; it is forgotten.
2906 With the @code{clear} command you can delete breakpoints according to
2907 where they are in your program. With the @code{delete} command you can
2908 delete individual breakpoints, watchpoints, or catchpoints by specifying
2909 their breakpoint numbers.
2911 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2912 automatically ignores breakpoints on the first instruction to be executed
2913 when you continue execution without changing the execution address.
2918 Delete any breakpoints at the next instruction to be executed in the
2919 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2920 the innermost frame is selected, this is a good way to delete a
2921 breakpoint where your program just stopped.
2923 @item clear @var{function}
2924 @itemx clear @var{filename}:@var{function}
2925 Delete any breakpoints set at entry to the function @var{function}.
2927 @item clear @var{linenum}
2928 @itemx clear @var{filename}:@var{linenum}
2929 Delete any breakpoints set at or within the code of the specified line.
2931 @cindex delete breakpoints
2933 @kindex d @r{(@code{delete})}
2934 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2935 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2936 ranges specified as arguments. If no argument is specified, delete all
2937 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2938 confirm off}). You can abbreviate this command as @code{d}.
2942 @subsection Disabling breakpoints
2944 @kindex disable breakpoints
2945 @kindex enable breakpoints
2946 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2947 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2948 it had been deleted, but remembers the information on the breakpoint so
2949 that you can @dfn{enable} it again later.
2951 You disable and enable breakpoints, watchpoints, and catchpoints with
2952 the @code{enable} and @code{disable} commands, optionally specifying one
2953 or more breakpoint numbers as arguments. Use @code{info break} or
2954 @code{info watch} to print a list of breakpoints, watchpoints, and
2955 catchpoints if you do not know which numbers to use.
2957 A breakpoint, watchpoint, or catchpoint can have any of four different
2958 states of enablement:
2962 Enabled. The breakpoint stops your program. A breakpoint set
2963 with the @code{break} command starts out in this state.
2965 Disabled. The breakpoint has no effect on your program.
2967 Enabled once. The breakpoint stops your program, but then becomes
2970 Enabled for deletion. The breakpoint stops your program, but
2971 immediately after it does so it is deleted permanently. A breakpoint
2972 set with the @code{tbreak} command starts out in this state.
2975 You can use the following commands to enable or disable breakpoints,
2976 watchpoints, and catchpoints:
2979 @kindex disable breakpoints
2981 @kindex dis @r{(@code{disable})}
2982 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2983 Disable the specified breakpoints---or all breakpoints, if none are
2984 listed. A disabled breakpoint has no effect but is not forgotten. All
2985 options such as ignore-counts, conditions and commands are remembered in
2986 case the breakpoint is enabled again later. You may abbreviate
2987 @code{disable} as @code{dis}.
2989 @kindex enable breakpoints
2991 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2992 Enable the specified breakpoints (or all defined breakpoints). They
2993 become effective once again in stopping your program.
2995 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2996 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2997 of these breakpoints immediately after stopping your program.
2999 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3000 Enable the specified breakpoints to work once, then die. @value{GDBN}
3001 deletes any of these breakpoints as soon as your program stops there.
3004 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3005 @c confusing: tbreak is also initially enabled.
3006 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3007 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3008 subsequently, they become disabled or enabled only when you use one of
3009 the commands above. (The command @code{until} can set and delete a
3010 breakpoint of its own, but it does not change the state of your other
3011 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3015 @subsection Break conditions
3016 @cindex conditional breakpoints
3017 @cindex breakpoint conditions
3019 @c FIXME what is scope of break condition expr? Context where wanted?
3020 @c in particular for a watchpoint?
3021 The simplest sort of breakpoint breaks every time your program reaches a
3022 specified place. You can also specify a @dfn{condition} for a
3023 breakpoint. A condition is just a Boolean expression in your
3024 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3025 a condition evaluates the expression each time your program reaches it,
3026 and your program stops only if the condition is @emph{true}.
3028 This is the converse of using assertions for program validation; in that
3029 situation, you want to stop when the assertion is violated---that is,
3030 when the condition is false. In C, if you want to test an assertion expressed
3031 by the condition @var{assert}, you should set the condition
3032 @samp{! @var{assert}} on the appropriate breakpoint.
3034 Conditions are also accepted for watchpoints; you may not need them,
3035 since a watchpoint is inspecting the value of an expression anyhow---but
3036 it might be simpler, say, to just set a watchpoint on a variable name,
3037 and specify a condition that tests whether the new value is an interesting
3040 Break conditions can have side effects, and may even call functions in
3041 your program. This can be useful, for example, to activate functions
3042 that log program progress, or to use your own print functions to
3043 format special data structures. The effects are completely predictable
3044 unless there is another enabled breakpoint at the same address. (In
3045 that case, @value{GDBN} might see the other breakpoint first and stop your
3046 program without checking the condition of this one.) Note that
3047 breakpoint commands are usually more convenient and flexible than break
3049 purpose of performing side effects when a breakpoint is reached
3050 (@pxref{Break Commands, ,Breakpoint command lists}).
3052 Break conditions can be specified when a breakpoint is set, by using
3053 @samp{if} in the arguments to the @code{break} command. @xref{Set
3054 Breaks, ,Setting breakpoints}. They can also be changed at any time
3055 with the @code{condition} command.
3057 You can also use the @code{if} keyword with the @code{watch} command.
3058 The @code{catch} command does not recognize the @code{if} keyword;
3059 @code{condition} is the only way to impose a further condition on a
3064 @item condition @var{bnum} @var{expression}
3065 Specify @var{expression} as the break condition for breakpoint,
3066 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3067 breakpoint @var{bnum} stops your program only if the value of
3068 @var{expression} is true (nonzero, in C). When you use
3069 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3070 syntactic correctness, and to determine whether symbols in it have
3071 referents in the context of your breakpoint. If @var{expression} uses
3072 symbols not referenced in the context of the breakpoint, @value{GDBN}
3073 prints an error message:
3076 No symbol "foo" in current context.
3081 not actually evaluate @var{expression} at the time the @code{condition}
3082 command (or a command that sets a breakpoint with a condition, like
3083 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3085 @item condition @var{bnum}
3086 Remove the condition from breakpoint number @var{bnum}. It becomes
3087 an ordinary unconditional breakpoint.
3090 @cindex ignore count (of breakpoint)
3091 A special case of a breakpoint condition is to stop only when the
3092 breakpoint has been reached a certain number of times. This is so
3093 useful that there is a special way to do it, using the @dfn{ignore
3094 count} of the breakpoint. Every breakpoint has an ignore count, which
3095 is an integer. Most of the time, the ignore count is zero, and
3096 therefore has no effect. But if your program reaches a breakpoint whose
3097 ignore count is positive, then instead of stopping, it just decrements
3098 the ignore count by one and continues. As a result, if the ignore count
3099 value is @var{n}, the breakpoint does not stop the next @var{n} times
3100 your program reaches it.
3104 @item ignore @var{bnum} @var{count}
3105 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3106 The next @var{count} times the breakpoint is reached, your program's
3107 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3110 To make the breakpoint stop the next time it is reached, specify
3113 When you use @code{continue} to resume execution of your program from a
3114 breakpoint, you can specify an ignore count directly as an argument to
3115 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3116 Stepping,,Continuing and stepping}.
3118 If a breakpoint has a positive ignore count and a condition, the
3119 condition is not checked. Once the ignore count reaches zero,
3120 @value{GDBN} resumes checking the condition.
3122 You could achieve the effect of the ignore count with a condition such
3123 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3124 is decremented each time. @xref{Convenience Vars, ,Convenience
3128 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3131 @node Break Commands
3132 @subsection Breakpoint command lists
3134 @cindex breakpoint commands
3135 You can give any breakpoint (or watchpoint or catchpoint) a series of
3136 commands to execute when your program stops due to that breakpoint. For
3137 example, you might want to print the values of certain expressions, or
3138 enable other breakpoints.
3143 @item commands @r{[}@var{bnum}@r{]}
3144 @itemx @dots{} @var{command-list} @dots{}
3146 Specify a list of commands for breakpoint number @var{bnum}. The commands
3147 themselves appear on the following lines. Type a line containing just
3148 @code{end} to terminate the commands.
3150 To remove all commands from a breakpoint, type @code{commands} and
3151 follow it immediately with @code{end}; that is, give no commands.
3153 With no @var{bnum} argument, @code{commands} refers to the last
3154 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3155 recently encountered).
3158 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3159 disabled within a @var{command-list}.
3161 You can use breakpoint commands to start your program up again. Simply
3162 use the @code{continue} command, or @code{step}, or any other command
3163 that resumes execution.
3165 Any other commands in the command list, after a command that resumes
3166 execution, are ignored. This is because any time you resume execution
3167 (even with a simple @code{next} or @code{step}), you may encounter
3168 another breakpoint---which could have its own command list, leading to
3169 ambiguities about which list to execute.
3172 If the first command you specify in a command list is @code{silent}, the
3173 usual message about stopping at a breakpoint is not printed. This may
3174 be desirable for breakpoints that are to print a specific message and
3175 then continue. If none of the remaining commands print anything, you
3176 see no sign that the breakpoint was reached. @code{silent} is
3177 meaningful only at the beginning of a breakpoint command list.
3179 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3180 print precisely controlled output, and are often useful in silent
3181 breakpoints. @xref{Output, ,Commands for controlled output}.
3183 For example, here is how you could use breakpoint commands to print the
3184 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3190 printf "x is %d\n",x
3195 One application for breakpoint commands is to compensate for one bug so
3196 you can test for another. Put a breakpoint just after the erroneous line
3197 of code, give it a condition to detect the case in which something
3198 erroneous has been done, and give it commands to assign correct values
3199 to any variables that need them. End with the @code{continue} command
3200 so that your program does not stop, and start with the @code{silent}
3201 command so that no output is produced. Here is an example:
3212 @node Breakpoint Menus
3213 @subsection Breakpoint menus
3215 @cindex symbol overloading
3217 Some programming languages (notably C@t{++} and Objective-C) permit a
3218 single function name
3219 to be defined several times, for application in different contexts.
3220 This is called @dfn{overloading}. When a function name is overloaded,
3221 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3222 a breakpoint. If you realize this is a problem, you can use
3223 something like @samp{break @var{function}(@var{types})} to specify which
3224 particular version of the function you want. Otherwise, @value{GDBN} offers
3225 you a menu of numbered choices for different possible breakpoints, and
3226 waits for your selection with the prompt @samp{>}. The first two
3227 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3228 sets a breakpoint at each definition of @var{function}, and typing
3229 @kbd{0} aborts the @code{break} command without setting any new
3232 For example, the following session excerpt shows an attempt to set a
3233 breakpoint at the overloaded symbol @code{String::after}.
3234 We choose three particular definitions of that function name:
3236 @c FIXME! This is likely to change to show arg type lists, at least
3239 (@value{GDBP}) b String::after
3242 [2] file:String.cc; line number:867
3243 [3] file:String.cc; line number:860
3244 [4] file:String.cc; line number:875
3245 [5] file:String.cc; line number:853
3246 [6] file:String.cc; line number:846
3247 [7] file:String.cc; line number:735
3249 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3250 Breakpoint 2 at 0xb344: file String.cc, line 875.
3251 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3252 Multiple breakpoints were set.
3253 Use the "delete" command to delete unwanted
3259 @c @ifclear BARETARGET
3260 @node Error in Breakpoints
3261 @subsection ``Cannot insert breakpoints''
3263 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3265 Under some operating systems, breakpoints cannot be used in a program if
3266 any other process is running that program. In this situation,
3267 attempting to run or continue a program with a breakpoint causes
3268 @value{GDBN} to print an error message:
3271 Cannot insert breakpoints.
3272 The same program may be running in another process.
3275 When this happens, you have three ways to proceed:
3279 Remove or disable the breakpoints, then continue.
3282 Suspend @value{GDBN}, and copy the file containing your program to a new
3283 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3284 that @value{GDBN} should run your program under that name.
3285 Then start your program again.
3288 Relink your program so that the text segment is nonsharable, using the
3289 linker option @samp{-N}. The operating system limitation may not apply
3290 to nonsharable executables.
3294 A similar message can be printed if you request too many active
3295 hardware-assisted breakpoints and watchpoints:
3297 @c FIXME: the precise wording of this message may change; the relevant
3298 @c source change is not committed yet (Sep 3, 1999).
3300 Stopped; cannot insert breakpoints.
3301 You may have requested too many hardware breakpoints and watchpoints.
3305 This message is printed when you attempt to resume the program, since
3306 only then @value{GDBN} knows exactly how many hardware breakpoints and
3307 watchpoints it needs to insert.
3309 When this message is printed, you need to disable or remove some of the
3310 hardware-assisted breakpoints and watchpoints, and then continue.
3313 @node Continuing and Stepping
3314 @section Continuing and stepping
3318 @cindex resuming execution
3319 @dfn{Continuing} means resuming program execution until your program
3320 completes normally. In contrast, @dfn{stepping} means executing just
3321 one more ``step'' of your program, where ``step'' may mean either one
3322 line of source code, or one machine instruction (depending on what
3323 particular command you use). Either when continuing or when stepping,
3324 your program may stop even sooner, due to a breakpoint or a signal. (If
3325 it stops due to a signal, you may want to use @code{handle}, or use
3326 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3330 @kindex c @r{(@code{continue})}
3331 @kindex fg @r{(resume foreground execution)}
3332 @item continue @r{[}@var{ignore-count}@r{]}
3333 @itemx c @r{[}@var{ignore-count}@r{]}
3334 @itemx fg @r{[}@var{ignore-count}@r{]}
3335 Resume program execution, at the address where your program last stopped;
3336 any breakpoints set at that address are bypassed. The optional argument
3337 @var{ignore-count} allows you to specify a further number of times to
3338 ignore a breakpoint at this location; its effect is like that of
3339 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3341 The argument @var{ignore-count} is meaningful only when your program
3342 stopped due to a breakpoint. At other times, the argument to
3343 @code{continue} is ignored.
3345 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3346 debugged program is deemed to be the foreground program) are provided
3347 purely for convenience, and have exactly the same behavior as
3351 To resume execution at a different place, you can use @code{return}
3352 (@pxref{Returning, ,Returning from a function}) to go back to the
3353 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3354 different address}) to go to an arbitrary location in your program.
3356 A typical technique for using stepping is to set a breakpoint
3357 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3358 beginning of the function or the section of your program where a problem
3359 is believed to lie, run your program until it stops at that breakpoint,
3360 and then step through the suspect area, examining the variables that are
3361 interesting, until you see the problem happen.
3365 @kindex s @r{(@code{step})}
3367 Continue running your program until control reaches a different source
3368 line, then stop it and return control to @value{GDBN}. This command is
3369 abbreviated @code{s}.
3372 @c "without debugging information" is imprecise; actually "without line
3373 @c numbers in the debugging information". (gcc -g1 has debugging info but
3374 @c not line numbers). But it seems complex to try to make that
3375 @c distinction here.
3376 @emph{Warning:} If you use the @code{step} command while control is
3377 within a function that was compiled without debugging information,
3378 execution proceeds until control reaches a function that does have
3379 debugging information. Likewise, it will not step into a function which
3380 is compiled without debugging information. To step through functions
3381 without debugging information, use the @code{stepi} command, described
3385 The @code{step} command only stops at the first instruction of a source
3386 line. This prevents the multiple stops that could otherwise occur in
3387 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3388 to stop if a function that has debugging information is called within
3389 the line. In other words, @code{step} @emph{steps inside} any functions
3390 called within the line.
3392 Also, the @code{step} command only enters a function if there is line
3393 number information for the function. Otherwise it acts like the
3394 @code{next} command. This avoids problems when using @code{cc -gl}
3395 on MIPS machines. Previously, @code{step} entered subroutines if there
3396 was any debugging information about the routine.
3398 @item step @var{count}
3399 Continue running as in @code{step}, but do so @var{count} times. If a
3400 breakpoint is reached, or a signal not related to stepping occurs before
3401 @var{count} steps, stepping stops right away.
3404 @kindex n @r{(@code{next})}
3405 @item next @r{[}@var{count}@r{]}
3406 Continue to the next source line in the current (innermost) stack frame.
3407 This is similar to @code{step}, but function calls that appear within
3408 the line of code are executed without stopping. Execution stops when
3409 control reaches a different line of code at the original stack level
3410 that was executing when you gave the @code{next} command. This command
3411 is abbreviated @code{n}.
3413 An argument @var{count} is a repeat count, as for @code{step}.
3416 @c FIX ME!! Do we delete this, or is there a way it fits in with
3417 @c the following paragraph? --- Vctoria
3419 @c @code{next} within a function that lacks debugging information acts like
3420 @c @code{step}, but any function calls appearing within the code of the
3421 @c function are executed without stopping.
3423 The @code{next} command only stops at the first instruction of a
3424 source line. This prevents multiple stops that could otherwise occur in
3425 @code{switch} statements, @code{for} loops, etc.
3427 @kindex set step-mode
3429 @cindex functions without line info, and stepping
3430 @cindex stepping into functions with no line info
3431 @itemx set step-mode on
3432 The @code{set step-mode on} command causes the @code{step} command to
3433 stop at the first instruction of a function which contains no debug line
3434 information rather than stepping over it.
3436 This is useful in cases where you may be interested in inspecting the
3437 machine instructions of a function which has no symbolic info and do not
3438 want @value{GDBN} to automatically skip over this function.
3440 @item set step-mode off
3441 Causes the @code{step} command to step over any functions which contains no
3442 debug information. This is the default.
3446 Continue running until just after function in the selected stack frame
3447 returns. Print the returned value (if any).
3449 Contrast this with the @code{return} command (@pxref{Returning,
3450 ,Returning from a function}).
3453 @kindex u @r{(@code{until})}
3456 Continue running until a source line past the current line, in the
3457 current stack frame, is reached. This command is used to avoid single
3458 stepping through a loop more than once. It is like the @code{next}
3459 command, except that when @code{until} encounters a jump, it
3460 automatically continues execution until the program counter is greater
3461 than the address of the jump.
3463 This means that when you reach the end of a loop after single stepping
3464 though it, @code{until} makes your program continue execution until it
3465 exits the loop. In contrast, a @code{next} command at the end of a loop
3466 simply steps back to the beginning of the loop, which forces you to step
3467 through the next iteration.
3469 @code{until} always stops your program if it attempts to exit the current
3472 @code{until} may produce somewhat counterintuitive results if the order
3473 of machine code does not match the order of the source lines. For
3474 example, in the following excerpt from a debugging session, the @code{f}
3475 (@code{frame}) command shows that execution is stopped at line
3476 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3480 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3482 (@value{GDBP}) until
3483 195 for ( ; argc > 0; NEXTARG) @{
3486 This happened because, for execution efficiency, the compiler had
3487 generated code for the loop closure test at the end, rather than the
3488 start, of the loop---even though the test in a C @code{for}-loop is
3489 written before the body of the loop. The @code{until} command appeared
3490 to step back to the beginning of the loop when it advanced to this
3491 expression; however, it has not really gone to an earlier
3492 statement---not in terms of the actual machine code.
3494 @code{until} with no argument works by means of single
3495 instruction stepping, and hence is slower than @code{until} with an
3498 @item until @var{location}
3499 @itemx u @var{location}
3500 Continue running your program until either the specified location is
3501 reached, or the current stack frame returns. @var{location} is any of
3502 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3503 ,Setting breakpoints}). This form of the command uses breakpoints, and
3504 hence is quicker than @code{until} without an argument. The specified
3505 location is actually reached only if it is in the current frame. This
3506 implies that @code{until} can be used to skip over recursive function
3507 invocations. For instance in the code below, if the current location is
3508 line @code{96}, issuing @code{until 99} will execute the program up to
3509 line @code{99} in the same invocation of factorial, i.e. after the inner
3510 invocations have returned.
3513 94 int factorial (int value)
3515 96 if (value > 1) @{
3516 97 value *= factorial (value - 1);
3523 @kindex advance @var{location}
3524 @itemx advance @var{location}
3525 Continue running the program up to the given location. An argument is
3526 required, anything of the same form as arguments for the @code{break}
3527 command. Execution will also stop upon exit from the current stack
3528 frame. This command is similar to @code{until}, but @code{advance} will
3529 not skip over recursive function calls, and the target location doesn't
3530 have to be in the same frame as the current one.
3534 @kindex si @r{(@code{stepi})}
3536 @itemx stepi @var{arg}
3538 Execute one machine instruction, then stop and return to the debugger.
3540 It is often useful to do @samp{display/i $pc} when stepping by machine
3541 instructions. This makes @value{GDBN} automatically display the next
3542 instruction to be executed, each time your program stops. @xref{Auto
3543 Display,, Automatic display}.
3545 An argument is a repeat count, as in @code{step}.
3549 @kindex ni @r{(@code{nexti})}
3551 @itemx nexti @var{arg}
3553 Execute one machine instruction, but if it is a function call,
3554 proceed until the function returns.
3556 An argument is a repeat count, as in @code{next}.
3563 A signal is an asynchronous event that can happen in a program. The
3564 operating system defines the possible kinds of signals, and gives each
3565 kind a name and a number. For example, in Unix @code{SIGINT} is the
3566 signal a program gets when you type an interrupt character (often @kbd{C-c});
3567 @code{SIGSEGV} is the signal a program gets from referencing a place in
3568 memory far away from all the areas in use; @code{SIGALRM} occurs when
3569 the alarm clock timer goes off (which happens only if your program has
3570 requested an alarm).
3572 @cindex fatal signals
3573 Some signals, including @code{SIGALRM}, are a normal part of the
3574 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3575 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3576 program has not specified in advance some other way to handle the signal.
3577 @code{SIGINT} does not indicate an error in your program, but it is normally
3578 fatal so it can carry out the purpose of the interrupt: to kill the program.
3580 @value{GDBN} has the ability to detect any occurrence of a signal in your
3581 program. You can tell @value{GDBN} in advance what to do for each kind of
3584 @cindex handling signals
3585 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3586 @code{SIGALRM} be silently passed to your program
3587 (so as not to interfere with their role in the program's functioning)
3588 but to stop your program immediately whenever an error signal happens.
3589 You can change these settings with the @code{handle} command.
3592 @kindex info signals
3595 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3596 handle each one. You can use this to see the signal numbers of all
3597 the defined types of signals.
3599 @code{info handle} is an alias for @code{info signals}.
3602 @item handle @var{signal} @var{keywords}@dots{}
3603 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3604 can be the number of a signal or its name (with or without the
3605 @samp{SIG} at the beginning); a list of signal numbers of the form
3606 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3607 known signals. The @var{keywords} say what change to make.
3611 The keywords allowed by the @code{handle} command can be abbreviated.
3612 Their full names are:
3616 @value{GDBN} should not stop your program when this signal happens. It may
3617 still print a message telling you that the signal has come in.
3620 @value{GDBN} should stop your program when this signal happens. This implies
3621 the @code{print} keyword as well.
3624 @value{GDBN} should print a message when this signal happens.
3627 @value{GDBN} should not mention the occurrence of the signal at all. This
3628 implies the @code{nostop} keyword as well.
3632 @value{GDBN} should allow your program to see this signal; your program
3633 can handle the signal, or else it may terminate if the signal is fatal
3634 and not handled. @code{pass} and @code{noignore} are synonyms.
3638 @value{GDBN} should not allow your program to see this signal.
3639 @code{nopass} and @code{ignore} are synonyms.
3643 When a signal stops your program, the signal is not visible to the
3645 continue. Your program sees the signal then, if @code{pass} is in
3646 effect for the signal in question @emph{at that time}. In other words,
3647 after @value{GDBN} reports a signal, you can use the @code{handle}
3648 command with @code{pass} or @code{nopass} to control whether your
3649 program sees that signal when you continue.
3651 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3652 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3653 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3656 You can also use the @code{signal} command to prevent your program from
3657 seeing a signal, or cause it to see a signal it normally would not see,
3658 or to give it any signal at any time. For example, if your program stopped
3659 due to some sort of memory reference error, you might store correct
3660 values into the erroneous variables and continue, hoping to see more
3661 execution; but your program would probably terminate immediately as
3662 a result of the fatal signal once it saw the signal. To prevent this,
3663 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3667 @section Stopping and starting multi-thread programs
3669 When your program has multiple threads (@pxref{Threads,, Debugging
3670 programs with multiple threads}), you can choose whether to set
3671 breakpoints on all threads, or on a particular thread.
3674 @cindex breakpoints and threads
3675 @cindex thread breakpoints
3676 @kindex break @dots{} thread @var{threadno}
3677 @item break @var{linespec} thread @var{threadno}
3678 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3679 @var{linespec} specifies source lines; there are several ways of
3680 writing them, but the effect is always to specify some source line.
3682 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3683 to specify that you only want @value{GDBN} to stop the program when a
3684 particular thread reaches this breakpoint. @var{threadno} is one of the
3685 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3686 column of the @samp{info threads} display.
3688 If you do not specify @samp{thread @var{threadno}} when you set a
3689 breakpoint, the breakpoint applies to @emph{all} threads of your
3692 You can use the @code{thread} qualifier on conditional breakpoints as
3693 well; in this case, place @samp{thread @var{threadno}} before the
3694 breakpoint condition, like this:
3697 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3702 @cindex stopped threads
3703 @cindex threads, stopped
3704 Whenever your program stops under @value{GDBN} for any reason,
3705 @emph{all} threads of execution stop, not just the current thread. This
3706 allows you to examine the overall state of the program, including
3707 switching between threads, without worrying that things may change
3710 @cindex continuing threads
3711 @cindex threads, continuing
3712 Conversely, whenever you restart the program, @emph{all} threads start
3713 executing. @emph{This is true even when single-stepping} with commands
3714 like @code{step} or @code{next}.
3716 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3717 Since thread scheduling is up to your debugging target's operating
3718 system (not controlled by @value{GDBN}), other threads may
3719 execute more than one statement while the current thread completes a
3720 single step. Moreover, in general other threads stop in the middle of a
3721 statement, rather than at a clean statement boundary, when the program
3724 You might even find your program stopped in another thread after
3725 continuing or even single-stepping. This happens whenever some other
3726 thread runs into a breakpoint, a signal, or an exception before the
3727 first thread completes whatever you requested.
3729 On some OSes, you can lock the OS scheduler and thus allow only a single
3733 @item set scheduler-locking @var{mode}
3734 Set the scheduler locking mode. If it is @code{off}, then there is no
3735 locking and any thread may run at any time. If @code{on}, then only the
3736 current thread may run when the inferior is resumed. The @code{step}
3737 mode optimizes for single-stepping. It stops other threads from
3738 ``seizing the prompt'' by preempting the current thread while you are
3739 stepping. Other threads will only rarely (or never) get a chance to run
3740 when you step. They are more likely to run when you @samp{next} over a
3741 function call, and they are completely free to run when you use commands
3742 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3743 thread hits a breakpoint during its timeslice, they will never steal the
3744 @value{GDBN} prompt away from the thread that you are debugging.
3746 @item show scheduler-locking
3747 Display the current scheduler locking mode.
3752 @chapter Examining the Stack
3754 When your program has stopped, the first thing you need to know is where it
3755 stopped and how it got there.
3758 Each time your program performs a function call, information about the call
3760 That information includes the location of the call in your program,
3761 the arguments of the call,
3762 and the local variables of the function being called.
3763 The information is saved in a block of data called a @dfn{stack frame}.
3764 The stack frames are allocated in a region of memory called the @dfn{call
3767 When your program stops, the @value{GDBN} commands for examining the
3768 stack allow you to see all of this information.
3770 @cindex selected frame
3771 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3772 @value{GDBN} commands refer implicitly to the selected frame. In
3773 particular, whenever you ask @value{GDBN} for the value of a variable in
3774 your program, the value is found in the selected frame. There are
3775 special @value{GDBN} commands to select whichever frame you are
3776 interested in. @xref{Selection, ,Selecting a frame}.
3778 When your program stops, @value{GDBN} automatically selects the
3779 currently executing frame and describes it briefly, similar to the
3780 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3783 * Frames:: Stack frames
3784 * Backtrace:: Backtraces
3785 * Selection:: Selecting a frame
3786 * Frame Info:: Information on a frame
3791 @section Stack frames
3793 @cindex frame, definition
3795 The call stack is divided up into contiguous pieces called @dfn{stack
3796 frames}, or @dfn{frames} for short; each frame is the data associated
3797 with one call to one function. The frame contains the arguments given
3798 to the function, the function's local variables, and the address at
3799 which the function is executing.
3801 @cindex initial frame
3802 @cindex outermost frame
3803 @cindex innermost frame
3804 When your program is started, the stack has only one frame, that of the
3805 function @code{main}. This is called the @dfn{initial} frame or the
3806 @dfn{outermost} frame. Each time a function is called, a new frame is
3807 made. Each time a function returns, the frame for that function invocation
3808 is eliminated. If a function is recursive, there can be many frames for
3809 the same function. The frame for the function in which execution is
3810 actually occurring is called the @dfn{innermost} frame. This is the most
3811 recently created of all the stack frames that still exist.
3813 @cindex frame pointer
3814 Inside your program, stack frames are identified by their addresses. A
3815 stack frame consists of many bytes, each of which has its own address; each
3816 kind of computer has a convention for choosing one byte whose
3817 address serves as the address of the frame. Usually this address is kept
3818 in a register called the @dfn{frame pointer register} while execution is
3819 going on in that frame.
3821 @cindex frame number
3822 @value{GDBN} assigns numbers to all existing stack frames, starting with
3823 zero for the innermost frame, one for the frame that called it,
3824 and so on upward. These numbers do not really exist in your program;
3825 they are assigned by @value{GDBN} to give you a way of designating stack
3826 frames in @value{GDBN} commands.
3828 @c The -fomit-frame-pointer below perennially causes hbox overflow
3829 @c underflow problems.
3830 @cindex frameless execution
3831 Some compilers provide a way to compile functions so that they operate
3832 without stack frames. (For example, the @value{GCC} option
3834 @samp{-fomit-frame-pointer}
3836 generates functions without a frame.)
3837 This is occasionally done with heavily used library functions to save
3838 the frame setup time. @value{GDBN} has limited facilities for dealing
3839 with these function invocations. If the innermost function invocation
3840 has no stack frame, @value{GDBN} nevertheless regards it as though
3841 it had a separate frame, which is numbered zero as usual, allowing
3842 correct tracing of the function call chain. However, @value{GDBN} has
3843 no provision for frameless functions elsewhere in the stack.
3846 @kindex frame@r{, command}
3847 @cindex current stack frame
3848 @item frame @var{args}
3849 The @code{frame} command allows you to move from one stack frame to another,
3850 and to print the stack frame you select. @var{args} may be either the
3851 address of the frame or the stack frame number. Without an argument,
3852 @code{frame} prints the current stack frame.
3854 @kindex select-frame
3855 @cindex selecting frame silently
3857 The @code{select-frame} command allows you to move from one stack frame
3858 to another without printing the frame. This is the silent version of
3867 @cindex stack traces
3868 A backtrace is a summary of how your program got where it is. It shows one
3869 line per frame, for many frames, starting with the currently executing
3870 frame (frame zero), followed by its caller (frame one), and on up the
3875 @kindex bt @r{(@code{backtrace})}
3878 Print a backtrace of the entire stack: one line per frame for all
3879 frames in the stack.
3881 You can stop the backtrace at any time by typing the system interrupt
3882 character, normally @kbd{C-c}.
3884 @item backtrace @var{n}
3886 Similar, but print only the innermost @var{n} frames.
3888 @item backtrace -@var{n}
3890 Similar, but print only the outermost @var{n} frames.
3895 @kindex info s @r{(@code{info stack})}
3896 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3897 are additional aliases for @code{backtrace}.
3899 Each line in the backtrace shows the frame number and the function name.
3900 The program counter value is also shown---unless you use @code{set
3901 print address off}. The backtrace also shows the source file name and
3902 line number, as well as the arguments to the function. The program
3903 counter value is omitted if it is at the beginning of the code for that
3906 Here is an example of a backtrace. It was made with the command
3907 @samp{bt 3}, so it shows the innermost three frames.
3911 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3913 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3914 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3916 (More stack frames follow...)
3921 The display for frame zero does not begin with a program counter
3922 value, indicating that your program has stopped at the beginning of the
3923 code for line @code{993} of @code{builtin.c}.
3925 @kindex set backtrace past-main
3926 @kindex show backtrace past-main
3927 @kindex set backtrace limit
3928 @kindex show backtrace limit
3930 Most programs have a standard user entry point---a place where system
3931 libraries and startup code transition into user code. For C this is
3932 @code{main}. When @value{GDBN} finds the entry function in a backtrace
3933 it will terminate the backtrace, to avoid tracing into highly
3934 system-specific (and generally uninteresting) code.
3936 If you need to examine the startup code, or limit the number of levels
3937 in a backtrace, you can change this behavior:
3940 @item set backtrace past-main
3941 @itemx set backtrace past-main on
3942 Backtraces will continue past the user entry point.
3944 @item set backtrace past-main off
3945 Backtraces will stop when they encounter the user entry point. This is the
3948 @item show backtrace past-main
3949 Display the current user entry point backtrace policy.
3951 @item set backtrace limit @var{n}
3952 @itemx set backtrace limit 0
3953 @cindex backtrace limit
3954 Limit the backtrace to @var{n} levels. A value of zero means
3957 @item show backtrace limit
3958 Display the current limit on backtrace levels.
3962 @section Selecting a frame
3964 Most commands for examining the stack and other data in your program work on
3965 whichever stack frame is selected at the moment. Here are the commands for
3966 selecting a stack frame; all of them finish by printing a brief description
3967 of the stack frame just selected.
3970 @kindex frame@r{, selecting}
3971 @kindex f @r{(@code{frame})}
3974 Select frame number @var{n}. Recall that frame zero is the innermost
3975 (currently executing) frame, frame one is the frame that called the
3976 innermost one, and so on. The highest-numbered frame is the one for
3979 @item frame @var{addr}
3981 Select the frame at address @var{addr}. This is useful mainly if the
3982 chaining of stack frames has been damaged by a bug, making it
3983 impossible for @value{GDBN} to assign numbers properly to all frames. In
3984 addition, this can be useful when your program has multiple stacks and
3985 switches between them.
3987 On the SPARC architecture, @code{frame} needs two addresses to
3988 select an arbitrary frame: a frame pointer and a stack pointer.
3990 On the MIPS and Alpha architecture, it needs two addresses: a stack
3991 pointer and a program counter.
3993 On the 29k architecture, it needs three addresses: a register stack
3994 pointer, a program counter, and a memory stack pointer.
3995 @c note to future updaters: this is conditioned on a flag
3996 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3997 @c as of 27 Jan 1994.
4001 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4002 advances toward the outermost frame, to higher frame numbers, to frames
4003 that have existed longer. @var{n} defaults to one.
4006 @kindex do @r{(@code{down})}
4008 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4009 advances toward the innermost frame, to lower frame numbers, to frames
4010 that were created more recently. @var{n} defaults to one. You may
4011 abbreviate @code{down} as @code{do}.
4014 All of these commands end by printing two lines of output describing the
4015 frame. The first line shows the frame number, the function name, the
4016 arguments, and the source file and line number of execution in that
4017 frame. The second line shows the text of that source line.
4025 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4027 10 read_input_file (argv[i]);
4031 After such a printout, the @code{list} command with no arguments
4032 prints ten lines centered on the point of execution in the frame.
4033 You can also edit the program at the point of execution with your favorite
4034 editing program by typing @code{edit}.
4035 @xref{List, ,Printing source lines},
4039 @kindex down-silently
4041 @item up-silently @var{n}
4042 @itemx down-silently @var{n}
4043 These two commands are variants of @code{up} and @code{down},
4044 respectively; they differ in that they do their work silently, without
4045 causing display of the new frame. They are intended primarily for use
4046 in @value{GDBN} command scripts, where the output might be unnecessary and
4051 @section Information about a frame
4053 There are several other commands to print information about the selected
4059 When used without any argument, this command does not change which
4060 frame is selected, but prints a brief description of the currently
4061 selected stack frame. It can be abbreviated @code{f}. With an
4062 argument, this command is used to select a stack frame.
4063 @xref{Selection, ,Selecting a frame}.
4066 @kindex info f @r{(@code{info frame})}
4069 This command prints a verbose description of the selected stack frame,
4074 the address of the frame
4076 the address of the next frame down (called by this frame)
4078 the address of the next frame up (caller of this frame)
4080 the language in which the source code corresponding to this frame is written
4082 the address of the frame's arguments
4084 the address of the frame's local variables
4086 the program counter saved in it (the address of execution in the caller frame)
4088 which registers were saved in the frame
4091 @noindent The verbose description is useful when
4092 something has gone wrong that has made the stack format fail to fit
4093 the usual conventions.
4095 @item info frame @var{addr}
4096 @itemx info f @var{addr}
4097 Print a verbose description of the frame at address @var{addr}, without
4098 selecting that frame. The selected frame remains unchanged by this
4099 command. This requires the same kind of address (more than one for some
4100 architectures) that you specify in the @code{frame} command.
4101 @xref{Selection, ,Selecting a frame}.
4105 Print the arguments of the selected frame, each on a separate line.
4109 Print the local variables of the selected frame, each on a separate
4110 line. These are all variables (declared either static or automatic)
4111 accessible at the point of execution of the selected frame.
4114 @cindex catch exceptions, list active handlers
4115 @cindex exception handlers, how to list
4117 Print a list of all the exception handlers that are active in the
4118 current stack frame at the current point of execution. To see other
4119 exception handlers, visit the associated frame (using the @code{up},
4120 @code{down}, or @code{frame} commands); then type @code{info catch}.
4121 @xref{Set Catchpoints, , Setting catchpoints}.
4127 @chapter Examining Source Files
4129 @value{GDBN} can print parts of your program's source, since the debugging
4130 information recorded in the program tells @value{GDBN} what source files were
4131 used to build it. When your program stops, @value{GDBN} spontaneously prints
4132 the line where it stopped. Likewise, when you select a stack frame
4133 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4134 execution in that frame has stopped. You can print other portions of
4135 source files by explicit command.
4137 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4138 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4139 @value{GDBN} under @sc{gnu} Emacs}.
4142 * List:: Printing source lines
4143 * Edit:: Editing source files
4144 * Search:: Searching source files
4145 * Source Path:: Specifying source directories
4146 * Machine Code:: Source and machine code
4150 @section Printing source lines
4153 @kindex l @r{(@code{list})}
4154 To print lines from a source file, use the @code{list} command
4155 (abbreviated @code{l}). By default, ten lines are printed.
4156 There are several ways to specify what part of the file you want to print.
4158 Here are the forms of the @code{list} command most commonly used:
4161 @item list @var{linenum}
4162 Print lines centered around line number @var{linenum} in the
4163 current source file.
4165 @item list @var{function}
4166 Print lines centered around the beginning of function
4170 Print more lines. If the last lines printed were printed with a
4171 @code{list} command, this prints lines following the last lines
4172 printed; however, if the last line printed was a solitary line printed
4173 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4174 Stack}), this prints lines centered around that line.
4177 Print lines just before the lines last printed.
4180 By default, @value{GDBN} prints ten source lines with any of these forms of
4181 the @code{list} command. You can change this using @code{set listsize}:
4184 @kindex set listsize
4185 @item set listsize @var{count}
4186 Make the @code{list} command display @var{count} source lines (unless
4187 the @code{list} argument explicitly specifies some other number).
4189 @kindex show listsize
4191 Display the number of lines that @code{list} prints.
4194 Repeating a @code{list} command with @key{RET} discards the argument,
4195 so it is equivalent to typing just @code{list}. This is more useful
4196 than listing the same lines again. An exception is made for an
4197 argument of @samp{-}; that argument is preserved in repetition so that
4198 each repetition moves up in the source file.
4201 In general, the @code{list} command expects you to supply zero, one or two
4202 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4203 of writing them, but the effect is always to specify some source line.
4204 Here is a complete description of the possible arguments for @code{list}:
4207 @item list @var{linespec}
4208 Print lines centered around the line specified by @var{linespec}.
4210 @item list @var{first},@var{last}
4211 Print lines from @var{first} to @var{last}. Both arguments are
4214 @item list ,@var{last}
4215 Print lines ending with @var{last}.
4217 @item list @var{first},
4218 Print lines starting with @var{first}.
4221 Print lines just after the lines last printed.
4224 Print lines just before the lines last printed.
4227 As described in the preceding table.
4230 Here are the ways of specifying a single source line---all the
4235 Specifies line @var{number} of the current source file.
4236 When a @code{list} command has two linespecs, this refers to
4237 the same source file as the first linespec.
4240 Specifies the line @var{offset} lines after the last line printed.
4241 When used as the second linespec in a @code{list} command that has
4242 two, this specifies the line @var{offset} lines down from the
4246 Specifies the line @var{offset} lines before the last line printed.
4248 @item @var{filename}:@var{number}
4249 Specifies line @var{number} in the source file @var{filename}.
4251 @item @var{function}
4252 Specifies the line that begins the body of the function @var{function}.
4253 For example: in C, this is the line with the open brace.
4255 @item @var{filename}:@var{function}
4256 Specifies the line of the open-brace that begins the body of the
4257 function @var{function} in the file @var{filename}. You only need the
4258 file name with a function name to avoid ambiguity when there are
4259 identically named functions in different source files.
4261 @item *@var{address}
4262 Specifies the line containing the program address @var{address}.
4263 @var{address} may be any expression.
4267 @section Editing source files
4268 @cindex editing source files
4271 @kindex e @r{(@code{edit})}
4272 To edit the lines in a source file, use the @code{edit} command.
4273 The editing program of your choice
4274 is invoked with the current line set to
4275 the active line in the program.
4276 Alternatively, there are several ways to specify what part of the file you
4277 want to print if you want to see other parts of the program.
4279 Here are the forms of the @code{edit} command most commonly used:
4283 Edit the current source file at the active line number in the program.
4285 @item edit @var{number}
4286 Edit the current source file with @var{number} as the active line number.
4288 @item edit @var{function}
4289 Edit the file containing @var{function} at the beginning of its definition.
4291 @item edit @var{filename}:@var{number}
4292 Specifies line @var{number} in the source file @var{filename}.
4294 @item edit @var{filename}:@var{function}
4295 Specifies the line that begins the body of the
4296 function @var{function} in the file @var{filename}. You only need the
4297 file name with a function name to avoid ambiguity when there are
4298 identically named functions in different source files.
4300 @item edit *@var{address}
4301 Specifies the line containing the program address @var{address}.
4302 @var{address} may be any expression.
4305 @subsection Choosing your editor
4306 You can customize @value{GDBN} to use any editor you want
4308 The only restriction is that your editor (say @code{ex}), recognizes the
4309 following command-line syntax:
4311 ex +@var{number} file
4313 The optional numeric value +@var{number} designates the active line in
4314 the file.}. By default, it is @value{EDITOR}, but you can change this
4315 by setting the environment variable @code{EDITOR} before using
4316 @value{GDBN}. For example, to configure @value{GDBN} to use the
4317 @code{vi} editor, you could use these commands with the @code{sh} shell:
4323 or in the @code{csh} shell,
4325 setenv EDITOR /usr/bin/vi
4330 @section Searching source files
4332 @kindex reverse-search
4334 There are two commands for searching through the current source file for a
4339 @kindex forward-search
4340 @item forward-search @var{regexp}
4341 @itemx search @var{regexp}
4342 The command @samp{forward-search @var{regexp}} checks each line,
4343 starting with the one following the last line listed, for a match for
4344 @var{regexp}. It lists the line that is found. You can use the
4345 synonym @samp{search @var{regexp}} or abbreviate the command name as
4348 @item reverse-search @var{regexp}
4349 The command @samp{reverse-search @var{regexp}} checks each line, starting
4350 with the one before the last line listed and going backward, for a match
4351 for @var{regexp}. It lists the line that is found. You can abbreviate
4352 this command as @code{rev}.
4356 @section Specifying source directories
4359 @cindex directories for source files
4360 Executable programs sometimes do not record the directories of the source
4361 files from which they were compiled, just the names. Even when they do,
4362 the directories could be moved between the compilation and your debugging
4363 session. @value{GDBN} has a list of directories to search for source files;
4364 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4365 it tries all the directories in the list, in the order they are present
4366 in the list, until it finds a file with the desired name. Note that
4367 the executable search path is @emph{not} used for this purpose. Neither is
4368 the current working directory, unless it happens to be in the source
4371 If @value{GDBN} cannot find a source file in the source path, and the
4372 object program records a directory, @value{GDBN} tries that directory
4373 too. If the source path is empty, and there is no record of the
4374 compilation directory, @value{GDBN} looks in the current directory as a
4377 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4378 any information it has cached about where source files are found and where
4379 each line is in the file.
4383 When you start @value{GDBN}, its source path includes only @samp{cdir}
4384 and @samp{cwd}, in that order.
4385 To add other directories, use the @code{directory} command.
4388 @item directory @var{dirname} @dots{}
4389 @item dir @var{dirname} @dots{}
4390 Add directory @var{dirname} to the front of the source path. Several
4391 directory names may be given to this command, separated by @samp{:}
4392 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4393 part of absolute file names) or
4394 whitespace. You may specify a directory that is already in the source
4395 path; this moves it forward, so @value{GDBN} searches it sooner.
4399 @vindex $cdir@r{, convenience variable}
4400 @vindex $cwdr@r{, convenience variable}
4401 @cindex compilation directory
4402 @cindex current directory
4403 @cindex working directory
4404 @cindex directory, current
4405 @cindex directory, compilation
4406 You can use the string @samp{$cdir} to refer to the compilation
4407 directory (if one is recorded), and @samp{$cwd} to refer to the current
4408 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4409 tracks the current working directory as it changes during your @value{GDBN}
4410 session, while the latter is immediately expanded to the current
4411 directory at the time you add an entry to the source path.
4414 Reset the source path to empty again. This requires confirmation.
4416 @c RET-repeat for @code{directory} is explicitly disabled, but since
4417 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4419 @item show directories
4420 @kindex show directories
4421 Print the source path: show which directories it contains.
4424 If your source path is cluttered with directories that are no longer of
4425 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4426 versions of source. You can correct the situation as follows:
4430 Use @code{directory} with no argument to reset the source path to empty.
4433 Use @code{directory} with suitable arguments to reinstall the
4434 directories you want in the source path. You can add all the
4435 directories in one command.
4439 @section Source and machine code
4441 You can use the command @code{info line} to map source lines to program
4442 addresses (and vice versa), and the command @code{disassemble} to display
4443 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4444 mode, the @code{info line} command causes the arrow to point to the
4445 line specified. Also, @code{info line} prints addresses in symbolic form as
4450 @item info line @var{linespec}
4451 Print the starting and ending addresses of the compiled code for
4452 source line @var{linespec}. You can specify source lines in any of
4453 the ways understood by the @code{list} command (@pxref{List, ,Printing
4457 For example, we can use @code{info line} to discover the location of
4458 the object code for the first line of function
4459 @code{m4_changequote}:
4461 @c FIXME: I think this example should also show the addresses in
4462 @c symbolic form, as they usually would be displayed.
4464 (@value{GDBP}) info line m4_changequote
4465 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4469 We can also inquire (using @code{*@var{addr}} as the form for
4470 @var{linespec}) what source line covers a particular address:
4472 (@value{GDBP}) info line *0x63ff
4473 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4476 @cindex @code{$_} and @code{info line}
4477 @kindex x@r{(examine), and} info line
4478 After @code{info line}, the default address for the @code{x} command
4479 is changed to the starting address of the line, so that @samp{x/i} is
4480 sufficient to begin examining the machine code (@pxref{Memory,
4481 ,Examining memory}). Also, this address is saved as the value of the
4482 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4487 @cindex assembly instructions
4488 @cindex instructions, assembly
4489 @cindex machine instructions
4490 @cindex listing machine instructions
4492 This specialized command dumps a range of memory as machine
4493 instructions. The default memory range is the function surrounding the
4494 program counter of the selected frame. A single argument to this
4495 command is a program counter value; @value{GDBN} dumps the function
4496 surrounding this value. Two arguments specify a range of addresses
4497 (first inclusive, second exclusive) to dump.
4500 The following example shows the disassembly of a range of addresses of
4501 HP PA-RISC 2.0 code:
4504 (@value{GDBP}) disas 0x32c4 0x32e4
4505 Dump of assembler code from 0x32c4 to 0x32e4:
4506 0x32c4 <main+204>: addil 0,dp
4507 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4508 0x32cc <main+212>: ldil 0x3000,r31
4509 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4510 0x32d4 <main+220>: ldo 0(r31),rp
4511 0x32d8 <main+224>: addil -0x800,dp
4512 0x32dc <main+228>: ldo 0x588(r1),r26
4513 0x32e0 <main+232>: ldil 0x3000,r31
4514 End of assembler dump.
4517 Some architectures have more than one commonly-used set of instruction
4518 mnemonics or other syntax.
4521 @kindex set disassembly-flavor
4522 @cindex assembly instructions
4523 @cindex instructions, assembly
4524 @cindex machine instructions
4525 @cindex listing machine instructions
4526 @cindex Intel disassembly flavor
4527 @cindex AT&T disassembly flavor
4528 @item set disassembly-flavor @var{instruction-set}
4529 Select the instruction set to use when disassembling the
4530 program via the @code{disassemble} or @code{x/i} commands.
4532 Currently this command is only defined for the Intel x86 family. You
4533 can set @var{instruction-set} to either @code{intel} or @code{att}.
4534 The default is @code{att}, the AT&T flavor used by default by Unix
4535 assemblers for x86-based targets.
4540 @chapter Examining Data
4542 @cindex printing data
4543 @cindex examining data
4546 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4547 @c document because it is nonstandard... Under Epoch it displays in a
4548 @c different window or something like that.
4549 The usual way to examine data in your program is with the @code{print}
4550 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4551 evaluates and prints the value of an expression of the language your
4552 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4553 Different Languages}).
4556 @item print @var{expr}
4557 @itemx print /@var{f} @var{expr}
4558 @var{expr} is an expression (in the source language). By default the
4559 value of @var{expr} is printed in a format appropriate to its data type;
4560 you can choose a different format by specifying @samp{/@var{f}}, where
4561 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4565 @itemx print /@var{f}
4566 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4567 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4568 conveniently inspect the same value in an alternative format.
4571 A more low-level way of examining data is with the @code{x} command.
4572 It examines data in memory at a specified address and prints it in a
4573 specified format. @xref{Memory, ,Examining memory}.
4575 If you are interested in information about types, or about how the
4576 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4577 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4581 * Expressions:: Expressions
4582 * Variables:: Program variables
4583 * Arrays:: Artificial arrays
4584 * Output Formats:: Output formats
4585 * Memory:: Examining memory
4586 * Auto Display:: Automatic display
4587 * Print Settings:: Print settings
4588 * Value History:: Value history
4589 * Convenience Vars:: Convenience variables
4590 * Registers:: Registers
4591 * Floating Point Hardware:: Floating point hardware
4592 * Vector Unit:: Vector Unit
4593 * Memory Region Attributes:: Memory region attributes
4594 * Dump/Restore Files:: Copy between memory and a file
4595 * Character Sets:: Debugging programs that use a different
4596 character set than GDB does
4600 @section Expressions
4603 @code{print} and many other @value{GDBN} commands accept an expression and
4604 compute its value. Any kind of constant, variable or operator defined
4605 by the programming language you are using is valid in an expression in
4606 @value{GDBN}. This includes conditional expressions, function calls,
4607 casts, and string constants. It also includes preprocessor macros, if
4608 you compiled your program to include this information; see
4611 @value{GDBN} supports array constants in expressions input by
4612 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4613 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4614 memory that is @code{malloc}ed in the target program.
4616 Because C is so widespread, most of the expressions shown in examples in
4617 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4618 Languages}, for information on how to use expressions in other
4621 In this section, we discuss operators that you can use in @value{GDBN}
4622 expressions regardless of your programming language.
4624 Casts are supported in all languages, not just in C, because it is so
4625 useful to cast a number into a pointer in order to examine a structure
4626 at that address in memory.
4627 @c FIXME: casts supported---Mod2 true?
4629 @value{GDBN} supports these operators, in addition to those common
4630 to programming languages:
4634 @samp{@@} is a binary operator for treating parts of memory as arrays.
4635 @xref{Arrays, ,Artificial arrays}, for more information.
4638 @samp{::} allows you to specify a variable in terms of the file or
4639 function where it is defined. @xref{Variables, ,Program variables}.
4641 @cindex @{@var{type}@}
4642 @cindex type casting memory
4643 @cindex memory, viewing as typed object
4644 @cindex casts, to view memory
4645 @item @{@var{type}@} @var{addr}
4646 Refers to an object of type @var{type} stored at address @var{addr} in
4647 memory. @var{addr} may be any expression whose value is an integer or
4648 pointer (but parentheses are required around binary operators, just as in
4649 a cast). This construct is allowed regardless of what kind of data is
4650 normally supposed to reside at @var{addr}.
4654 @section Program variables
4656 The most common kind of expression to use is the name of a variable
4659 Variables in expressions are understood in the selected stack frame
4660 (@pxref{Selection, ,Selecting a frame}); they must be either:
4664 global (or file-static)
4671 visible according to the scope rules of the
4672 programming language from the point of execution in that frame
4675 @noindent This means that in the function
4690 you can examine and use the variable @code{a} whenever your program is
4691 executing within the function @code{foo}, but you can only use or
4692 examine the variable @code{b} while your program is executing inside
4693 the block where @code{b} is declared.
4695 @cindex variable name conflict
4696 There is an exception: you can refer to a variable or function whose
4697 scope is a single source file even if the current execution point is not
4698 in this file. But it is possible to have more than one such variable or
4699 function with the same name (in different source files). If that
4700 happens, referring to that name has unpredictable effects. If you wish,
4701 you can specify a static variable in a particular function or file,
4702 using the colon-colon notation:
4704 @cindex colon-colon, context for variables/functions
4706 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4707 @cindex @code{::}, context for variables/functions
4710 @var{file}::@var{variable}
4711 @var{function}::@var{variable}
4715 Here @var{file} or @var{function} is the name of the context for the
4716 static @var{variable}. In the case of file names, you can use quotes to
4717 make sure @value{GDBN} parses the file name as a single word---for example,
4718 to print a global value of @code{x} defined in @file{f2.c}:
4721 (@value{GDBP}) p 'f2.c'::x
4724 @cindex C@t{++} scope resolution
4725 This use of @samp{::} is very rarely in conflict with the very similar
4726 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4727 scope resolution operator in @value{GDBN} expressions.
4728 @c FIXME: Um, so what happens in one of those rare cases where it's in
4731 @cindex wrong values
4732 @cindex variable values, wrong
4734 @emph{Warning:} Occasionally, a local variable may appear to have the
4735 wrong value at certain points in a function---just after entry to a new
4736 scope, and just before exit.
4738 You may see this problem when you are stepping by machine instructions.
4739 This is because, on most machines, it takes more than one instruction to
4740 set up a stack frame (including local variable definitions); if you are
4741 stepping by machine instructions, variables may appear to have the wrong
4742 values until the stack frame is completely built. On exit, it usually
4743 also takes more than one machine instruction to destroy a stack frame;
4744 after you begin stepping through that group of instructions, local
4745 variable definitions may be gone.
4747 This may also happen when the compiler does significant optimizations.
4748 To be sure of always seeing accurate values, turn off all optimization
4751 @cindex ``No symbol "foo" in current context''
4752 Another possible effect of compiler optimizations is to optimize
4753 unused variables out of existence, or assign variables to registers (as
4754 opposed to memory addresses). Depending on the support for such cases
4755 offered by the debug info format used by the compiler, @value{GDBN}
4756 might not be able to display values for such local variables. If that
4757 happens, @value{GDBN} will print a message like this:
4760 No symbol "foo" in current context.
4763 To solve such problems, either recompile without optimizations, or use a
4764 different debug info format, if the compiler supports several such
4765 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4766 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4767 produces debug info in a format that is superior to formats such as
4768 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4769 an effective form for debug info. @xref{Debugging Options,,Options
4770 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4774 @section Artificial arrays
4776 @cindex artificial array
4777 @kindex @@@r{, referencing memory as an array}
4778 It is often useful to print out several successive objects of the
4779 same type in memory; a section of an array, or an array of
4780 dynamically determined size for which only a pointer exists in the
4783 You can do this by referring to a contiguous span of memory as an
4784 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4785 operand of @samp{@@} should be the first element of the desired array
4786 and be an individual object. The right operand should be the desired length
4787 of the array. The result is an array value whose elements are all of
4788 the type of the left argument. The first element is actually the left
4789 argument; the second element comes from bytes of memory immediately
4790 following those that hold the first element, and so on. Here is an
4791 example. If a program says
4794 int *array = (int *) malloc (len * sizeof (int));
4798 you can print the contents of @code{array} with
4804 The left operand of @samp{@@} must reside in memory. Array values made
4805 with @samp{@@} in this way behave just like other arrays in terms of
4806 subscripting, and are coerced to pointers when used in expressions.
4807 Artificial arrays most often appear in expressions via the value history
4808 (@pxref{Value History, ,Value history}), after printing one out.
4810 Another way to create an artificial array is to use a cast.
4811 This re-interprets a value as if it were an array.
4812 The value need not be in memory:
4814 (@value{GDBP}) p/x (short[2])0x12345678
4815 $1 = @{0x1234, 0x5678@}
4818 As a convenience, if you leave the array length out (as in
4819 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4820 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4822 (@value{GDBP}) p/x (short[])0x12345678
4823 $2 = @{0x1234, 0x5678@}
4826 Sometimes the artificial array mechanism is not quite enough; in
4827 moderately complex data structures, the elements of interest may not
4828 actually be adjacent---for example, if you are interested in the values
4829 of pointers in an array. One useful work-around in this situation is
4830 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4831 variables}) as a counter in an expression that prints the first
4832 interesting value, and then repeat that expression via @key{RET}. For
4833 instance, suppose you have an array @code{dtab} of pointers to
4834 structures, and you are interested in the values of a field @code{fv}
4835 in each structure. Here is an example of what you might type:
4845 @node Output Formats
4846 @section Output formats
4848 @cindex formatted output
4849 @cindex output formats
4850 By default, @value{GDBN} prints a value according to its data type. Sometimes
4851 this is not what you want. For example, you might want to print a number
4852 in hex, or a pointer in decimal. Or you might want to view data in memory
4853 at a certain address as a character string or as an instruction. To do
4854 these things, specify an @dfn{output format} when you print a value.
4856 The simplest use of output formats is to say how to print a value
4857 already computed. This is done by starting the arguments of the
4858 @code{print} command with a slash and a format letter. The format
4859 letters supported are:
4863 Regard the bits of the value as an integer, and print the integer in
4867 Print as integer in signed decimal.
4870 Print as integer in unsigned decimal.
4873 Print as integer in octal.
4876 Print as integer in binary. The letter @samp{t} stands for ``two''.
4877 @footnote{@samp{b} cannot be used because these format letters are also
4878 used with the @code{x} command, where @samp{b} stands for ``byte'';
4879 see @ref{Memory,,Examining memory}.}
4882 @cindex unknown address, locating
4883 @cindex locate address
4884 Print as an address, both absolute in hexadecimal and as an offset from
4885 the nearest preceding symbol. You can use this format used to discover
4886 where (in what function) an unknown address is located:
4889 (@value{GDBP}) p/a 0x54320
4890 $3 = 0x54320 <_initialize_vx+396>
4894 The command @code{info symbol 0x54320} yields similar results.
4895 @xref{Symbols, info symbol}.
4898 Regard as an integer and print it as a character constant.
4901 Regard the bits of the value as a floating point number and print
4902 using typical floating point syntax.
4905 For example, to print the program counter in hex (@pxref{Registers}), type
4912 Note that no space is required before the slash; this is because command
4913 names in @value{GDBN} cannot contain a slash.
4915 To reprint the last value in the value history with a different format,
4916 you can use the @code{print} command with just a format and no
4917 expression. For example, @samp{p/x} reprints the last value in hex.
4920 @section Examining memory
4922 You can use the command @code{x} (for ``examine'') to examine memory in
4923 any of several formats, independently of your program's data types.
4925 @cindex examining memory
4927 @kindex x @r{(examine memory)}
4928 @item x/@var{nfu} @var{addr}
4931 Use the @code{x} command to examine memory.
4934 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4935 much memory to display and how to format it; @var{addr} is an
4936 expression giving the address where you want to start displaying memory.
4937 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4938 Several commands set convenient defaults for @var{addr}.
4941 @item @var{n}, the repeat count
4942 The repeat count is a decimal integer; the default is 1. It specifies
4943 how much memory (counting by units @var{u}) to display.
4944 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4947 @item @var{f}, the display format
4948 The display format is one of the formats used by @code{print},
4949 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4950 The default is @samp{x} (hexadecimal) initially.
4951 The default changes each time you use either @code{x} or @code{print}.
4953 @item @var{u}, the unit size
4954 The unit size is any of
4960 Halfwords (two bytes).
4962 Words (four bytes). This is the initial default.
4964 Giant words (eight bytes).
4967 Each time you specify a unit size with @code{x}, that size becomes the
4968 default unit the next time you use @code{x}. (For the @samp{s} and
4969 @samp{i} formats, the unit size is ignored and is normally not written.)
4971 @item @var{addr}, starting display address
4972 @var{addr} is the address where you want @value{GDBN} to begin displaying
4973 memory. The expression need not have a pointer value (though it may);
4974 it is always interpreted as an integer address of a byte of memory.
4975 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4976 @var{addr} is usually just after the last address examined---but several
4977 other commands also set the default address: @code{info breakpoints} (to
4978 the address of the last breakpoint listed), @code{info line} (to the
4979 starting address of a line), and @code{print} (if you use it to display
4980 a value from memory).
4983 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4984 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4985 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4986 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4987 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4989 Since the letters indicating unit sizes are all distinct from the
4990 letters specifying output formats, you do not have to remember whether
4991 unit size or format comes first; either order works. The output
4992 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4993 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4995 Even though the unit size @var{u} is ignored for the formats @samp{s}
4996 and @samp{i}, you might still want to use a count @var{n}; for example,
4997 @samp{3i} specifies that you want to see three machine instructions,
4998 including any operands. The command @code{disassemble} gives an
4999 alternative way of inspecting machine instructions; see @ref{Machine
5000 Code,,Source and machine code}.
5002 All the defaults for the arguments to @code{x} are designed to make it
5003 easy to continue scanning memory with minimal specifications each time
5004 you use @code{x}. For example, after you have inspected three machine
5005 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5006 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5007 the repeat count @var{n} is used again; the other arguments default as
5008 for successive uses of @code{x}.
5010 @cindex @code{$_}, @code{$__}, and value history
5011 The addresses and contents printed by the @code{x} command are not saved
5012 in the value history because there is often too much of them and they
5013 would get in the way. Instead, @value{GDBN} makes these values available for
5014 subsequent use in expressions as values of the convenience variables
5015 @code{$_} and @code{$__}. After an @code{x} command, the last address
5016 examined is available for use in expressions in the convenience variable
5017 @code{$_}. The contents of that address, as examined, are available in
5018 the convenience variable @code{$__}.
5020 If the @code{x} command has a repeat count, the address and contents saved
5021 are from the last memory unit printed; this is not the same as the last
5022 address printed if several units were printed on the last line of output.
5025 @section Automatic display
5026 @cindex automatic display
5027 @cindex display of expressions
5029 If you find that you want to print the value of an expression frequently
5030 (to see how it changes), you might want to add it to the @dfn{automatic
5031 display list} so that @value{GDBN} prints its value each time your program stops.
5032 Each expression added to the list is given a number to identify it;
5033 to remove an expression from the list, you specify that number.
5034 The automatic display looks like this:
5038 3: bar[5] = (struct hack *) 0x3804
5042 This display shows item numbers, expressions and their current values. As with
5043 displays you request manually using @code{x} or @code{print}, you can
5044 specify the output format you prefer; in fact, @code{display} decides
5045 whether to use @code{print} or @code{x} depending on how elaborate your
5046 format specification is---it uses @code{x} if you specify a unit size,
5047 or one of the two formats (@samp{i} and @samp{s}) that are only
5048 supported by @code{x}; otherwise it uses @code{print}.
5052 @item display @var{expr}
5053 Add the expression @var{expr} to the list of expressions to display
5054 each time your program stops. @xref{Expressions, ,Expressions}.
5056 @code{display} does not repeat if you press @key{RET} again after using it.
5058 @item display/@var{fmt} @var{expr}
5059 For @var{fmt} specifying only a display format and not a size or
5060 count, add the expression @var{expr} to the auto-display list but
5061 arrange to display it each time in the specified format @var{fmt}.
5062 @xref{Output Formats,,Output formats}.
5064 @item display/@var{fmt} @var{addr}
5065 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5066 number of units, add the expression @var{addr} as a memory address to
5067 be examined each time your program stops. Examining means in effect
5068 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5071 For example, @samp{display/i $pc} can be helpful, to see the machine
5072 instruction about to be executed each time execution stops (@samp{$pc}
5073 is a common name for the program counter; @pxref{Registers, ,Registers}).
5076 @kindex delete display
5078 @item undisplay @var{dnums}@dots{}
5079 @itemx delete display @var{dnums}@dots{}
5080 Remove item numbers @var{dnums} from the list of expressions to display.
5082 @code{undisplay} does not repeat if you press @key{RET} after using it.
5083 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5085 @kindex disable display
5086 @item disable display @var{dnums}@dots{}
5087 Disable the display of item numbers @var{dnums}. A disabled display
5088 item is not printed automatically, but is not forgotten. It may be
5089 enabled again later.
5091 @kindex enable display
5092 @item enable display @var{dnums}@dots{}
5093 Enable display of item numbers @var{dnums}. It becomes effective once
5094 again in auto display of its expression, until you specify otherwise.
5097 Display the current values of the expressions on the list, just as is
5098 done when your program stops.
5100 @kindex info display
5102 Print the list of expressions previously set up to display
5103 automatically, each one with its item number, but without showing the
5104 values. This includes disabled expressions, which are marked as such.
5105 It also includes expressions which would not be displayed right now
5106 because they refer to automatic variables not currently available.
5109 If a display expression refers to local variables, then it does not make
5110 sense outside the lexical context for which it was set up. Such an
5111 expression is disabled when execution enters a context where one of its
5112 variables is not defined. For example, if you give the command
5113 @code{display last_char} while inside a function with an argument
5114 @code{last_char}, @value{GDBN} displays this argument while your program
5115 continues to stop inside that function. When it stops elsewhere---where
5116 there is no variable @code{last_char}---the display is disabled
5117 automatically. The next time your program stops where @code{last_char}
5118 is meaningful, you can enable the display expression once again.
5120 @node Print Settings
5121 @section Print settings
5123 @cindex format options
5124 @cindex print settings
5125 @value{GDBN} provides the following ways to control how arrays, structures,
5126 and symbols are printed.
5129 These settings are useful for debugging programs in any language:
5132 @kindex set print address
5133 @item set print address
5134 @itemx set print address on
5135 @value{GDBN} prints memory addresses showing the location of stack
5136 traces, structure values, pointer values, breakpoints, and so forth,
5137 even when it also displays the contents of those addresses. The default
5138 is @code{on}. For example, this is what a stack frame display looks like with
5139 @code{set print address on}:
5144 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5146 530 if (lquote != def_lquote)
5150 @item set print address off
5151 Do not print addresses when displaying their contents. For example,
5152 this is the same stack frame displayed with @code{set print address off}:
5156 (@value{GDBP}) set print addr off
5158 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5159 530 if (lquote != def_lquote)
5163 You can use @samp{set print address off} to eliminate all machine
5164 dependent displays from the @value{GDBN} interface. For example, with
5165 @code{print address off}, you should get the same text for backtraces on
5166 all machines---whether or not they involve pointer arguments.
5168 @kindex show print address
5169 @item show print address
5170 Show whether or not addresses are to be printed.
5173 When @value{GDBN} prints a symbolic address, it normally prints the
5174 closest earlier symbol plus an offset. If that symbol does not uniquely
5175 identify the address (for example, it is a name whose scope is a single
5176 source file), you may need to clarify. One way to do this is with
5177 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5178 you can set @value{GDBN} to print the source file and line number when
5179 it prints a symbolic address:
5182 @kindex set print symbol-filename
5183 @item set print symbol-filename on
5184 Tell @value{GDBN} to print the source file name and line number of a
5185 symbol in the symbolic form of an address.
5187 @item set print symbol-filename off
5188 Do not print source file name and line number of a symbol. This is the
5191 @kindex show print symbol-filename
5192 @item show print symbol-filename
5193 Show whether or not @value{GDBN} will print the source file name and
5194 line number of a symbol in the symbolic form of an address.
5197 Another situation where it is helpful to show symbol filenames and line
5198 numbers is when disassembling code; @value{GDBN} shows you the line
5199 number and source file that corresponds to each instruction.
5201 Also, you may wish to see the symbolic form only if the address being
5202 printed is reasonably close to the closest earlier symbol:
5205 @kindex set print max-symbolic-offset
5206 @item set print max-symbolic-offset @var{max-offset}
5207 Tell @value{GDBN} to only display the symbolic form of an address if the
5208 offset between the closest earlier symbol and the address is less than
5209 @var{max-offset}. The default is 0, which tells @value{GDBN}
5210 to always print the symbolic form of an address if any symbol precedes it.
5212 @kindex show print max-symbolic-offset
5213 @item show print max-symbolic-offset
5214 Ask how large the maximum offset is that @value{GDBN} prints in a
5218 @cindex wild pointer, interpreting
5219 @cindex pointer, finding referent
5220 If you have a pointer and you are not sure where it points, try
5221 @samp{set print symbol-filename on}. Then you can determine the name
5222 and source file location of the variable where it points, using
5223 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5224 For example, here @value{GDBN} shows that a variable @code{ptt} points
5225 at another variable @code{t}, defined in @file{hi2.c}:
5228 (@value{GDBP}) set print symbol-filename on
5229 (@value{GDBP}) p/a ptt
5230 $4 = 0xe008 <t in hi2.c>
5234 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5235 does not show the symbol name and filename of the referent, even with
5236 the appropriate @code{set print} options turned on.
5239 Other settings control how different kinds of objects are printed:
5242 @kindex set print array
5243 @item set print array
5244 @itemx set print array on
5245 Pretty print arrays. This format is more convenient to read,
5246 but uses more space. The default is off.
5248 @item set print array off
5249 Return to compressed format for arrays.
5251 @kindex show print array
5252 @item show print array
5253 Show whether compressed or pretty format is selected for displaying
5256 @kindex set print elements
5257 @item set print elements @var{number-of-elements}
5258 Set a limit on how many elements of an array @value{GDBN} will print.
5259 If @value{GDBN} is printing a large array, it stops printing after it has
5260 printed the number of elements set by the @code{set print elements} command.
5261 This limit also applies to the display of strings.
5262 When @value{GDBN} starts, this limit is set to 200.
5263 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5265 @kindex show print elements
5266 @item show print elements
5267 Display the number of elements of a large array that @value{GDBN} will print.
5268 If the number is 0, then the printing is unlimited.
5270 @kindex set print null-stop
5271 @item set print null-stop
5272 Cause @value{GDBN} to stop printing the characters of an array when the first
5273 @sc{null} is encountered. This is useful when large arrays actually
5274 contain only short strings.
5277 @kindex set print pretty
5278 @item set print pretty on
5279 Cause @value{GDBN} to print structures in an indented format with one member
5280 per line, like this:
5295 @item set print pretty off
5296 Cause @value{GDBN} to print structures in a compact format, like this:
5300 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5301 meat = 0x54 "Pork"@}
5306 This is the default format.
5308 @kindex show print pretty
5309 @item show print pretty
5310 Show which format @value{GDBN} is using to print structures.
5312 @kindex set print sevenbit-strings
5313 @item set print sevenbit-strings on
5314 Print using only seven-bit characters; if this option is set,
5315 @value{GDBN} displays any eight-bit characters (in strings or
5316 character values) using the notation @code{\}@var{nnn}. This setting is
5317 best if you are working in English (@sc{ascii}) and you use the
5318 high-order bit of characters as a marker or ``meta'' bit.
5320 @item set print sevenbit-strings off
5321 Print full eight-bit characters. This allows the use of more
5322 international character sets, and is the default.
5324 @kindex show print sevenbit-strings
5325 @item show print sevenbit-strings
5326 Show whether or not @value{GDBN} is printing only seven-bit characters.
5328 @kindex set print union
5329 @item set print union on
5330 Tell @value{GDBN} to print unions which are contained in structures. This
5331 is the default setting.
5333 @item set print union off
5334 Tell @value{GDBN} not to print unions which are contained in structures.
5336 @kindex show print union
5337 @item show print union
5338 Ask @value{GDBN} whether or not it will print unions which are contained in
5341 For example, given the declarations
5344 typedef enum @{Tree, Bug@} Species;
5345 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5346 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5357 struct thing foo = @{Tree, @{Acorn@}@};
5361 with @code{set print union on} in effect @samp{p foo} would print
5364 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5368 and with @code{set print union off} in effect it would print
5371 $1 = @{it = Tree, form = @{...@}@}
5377 These settings are of interest when debugging C@t{++} programs:
5381 @kindex set print demangle
5382 @item set print demangle
5383 @itemx set print demangle on
5384 Print C@t{++} names in their source form rather than in the encoded
5385 (``mangled'') form passed to the assembler and linker for type-safe
5386 linkage. The default is on.
5388 @kindex show print demangle
5389 @item show print demangle
5390 Show whether C@t{++} names are printed in mangled or demangled form.
5392 @kindex set print asm-demangle
5393 @item set print asm-demangle
5394 @itemx set print asm-demangle on
5395 Print C@t{++} names in their source form rather than their mangled form, even
5396 in assembler code printouts such as instruction disassemblies.
5399 @kindex show print asm-demangle
5400 @item show print asm-demangle
5401 Show whether C@t{++} names in assembly listings are printed in mangled
5404 @kindex set demangle-style
5405 @cindex C@t{++} symbol decoding style
5406 @cindex symbol decoding style, C@t{++}
5407 @item set demangle-style @var{style}
5408 Choose among several encoding schemes used by different compilers to
5409 represent C@t{++} names. The choices for @var{style} are currently:
5413 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5416 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5417 This is the default.
5420 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5423 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5426 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5427 @strong{Warning:} this setting alone is not sufficient to allow
5428 debugging @code{cfront}-generated executables. @value{GDBN} would
5429 require further enhancement to permit that.
5432 If you omit @var{style}, you will see a list of possible formats.
5434 @kindex show demangle-style
5435 @item show demangle-style
5436 Display the encoding style currently in use for decoding C@t{++} symbols.
5438 @kindex set print object
5439 @item set print object
5440 @itemx set print object on
5441 When displaying a pointer to an object, identify the @emph{actual}
5442 (derived) type of the object rather than the @emph{declared} type, using
5443 the virtual function table.
5445 @item set print object off
5446 Display only the declared type of objects, without reference to the
5447 virtual function table. This is the default setting.
5449 @kindex show print object
5450 @item show print object
5451 Show whether actual, or declared, object types are displayed.
5453 @kindex set print static-members
5454 @item set print static-members
5455 @itemx set print static-members on
5456 Print static members when displaying a C@t{++} object. The default is on.
5458 @item set print static-members off
5459 Do not print static members when displaying a C@t{++} object.
5461 @kindex show print static-members
5462 @item show print static-members
5463 Show whether C@t{++} static members are printed, or not.
5465 @c These don't work with HP ANSI C++ yet.
5466 @kindex set print vtbl
5467 @item set print vtbl
5468 @itemx set print vtbl on
5469 Pretty print C@t{++} virtual function tables. The default is off.
5470 (The @code{vtbl} commands do not work on programs compiled with the HP
5471 ANSI C@t{++} compiler (@code{aCC}).)
5473 @item set print vtbl off
5474 Do not pretty print C@t{++} virtual function tables.
5476 @kindex show print vtbl
5477 @item show print vtbl
5478 Show whether C@t{++} virtual function tables are pretty printed, or not.
5482 @section Value history
5484 @cindex value history
5485 Values printed by the @code{print} command are saved in the @value{GDBN}
5486 @dfn{value history}. This allows you to refer to them in other expressions.
5487 Values are kept until the symbol table is re-read or discarded
5488 (for example with the @code{file} or @code{symbol-file} commands).
5489 When the symbol table changes, the value history is discarded,
5490 since the values may contain pointers back to the types defined in the
5495 @cindex history number
5496 The values printed are given @dfn{history numbers} by which you can
5497 refer to them. These are successive integers starting with one.
5498 @code{print} shows you the history number assigned to a value by
5499 printing @samp{$@var{num} = } before the value; here @var{num} is the
5502 To refer to any previous value, use @samp{$} followed by the value's
5503 history number. The way @code{print} labels its output is designed to
5504 remind you of this. Just @code{$} refers to the most recent value in
5505 the history, and @code{$$} refers to the value before that.
5506 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5507 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5508 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5510 For example, suppose you have just printed a pointer to a structure and
5511 want to see the contents of the structure. It suffices to type
5517 If you have a chain of structures where the component @code{next} points
5518 to the next one, you can print the contents of the next one with this:
5525 You can print successive links in the chain by repeating this
5526 command---which you can do by just typing @key{RET}.
5528 Note that the history records values, not expressions. If the value of
5529 @code{x} is 4 and you type these commands:
5537 then the value recorded in the value history by the @code{print} command
5538 remains 4 even though the value of @code{x} has changed.
5543 Print the last ten values in the value history, with their item numbers.
5544 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5545 values} does not change the history.
5547 @item show values @var{n}
5548 Print ten history values centered on history item number @var{n}.
5551 Print ten history values just after the values last printed. If no more
5552 values are available, @code{show values +} produces no display.
5555 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5556 same effect as @samp{show values +}.
5558 @node Convenience Vars
5559 @section Convenience variables
5561 @cindex convenience variables
5562 @value{GDBN} provides @dfn{convenience variables} that you can use within
5563 @value{GDBN} to hold on to a value and refer to it later. These variables
5564 exist entirely within @value{GDBN}; they are not part of your program, and
5565 setting a convenience variable has no direct effect on further execution
5566 of your program. That is why you can use them freely.
5568 Convenience variables are prefixed with @samp{$}. Any name preceded by
5569 @samp{$} can be used for a convenience variable, unless it is one of
5570 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5571 (Value history references, in contrast, are @emph{numbers} preceded
5572 by @samp{$}. @xref{Value History, ,Value history}.)
5574 You can save a value in a convenience variable with an assignment
5575 expression, just as you would set a variable in your program.
5579 set $foo = *object_ptr
5583 would save in @code{$foo} the value contained in the object pointed to by
5586 Using a convenience variable for the first time creates it, but its
5587 value is @code{void} until you assign a new value. You can alter the
5588 value with another assignment at any time.
5590 Convenience variables have no fixed types. You can assign a convenience
5591 variable any type of value, including structures and arrays, even if
5592 that variable already has a value of a different type. The convenience
5593 variable, when used as an expression, has the type of its current value.
5596 @kindex show convenience
5597 @item show convenience
5598 Print a list of convenience variables used so far, and their values.
5599 Abbreviated @code{show conv}.
5602 One of the ways to use a convenience variable is as a counter to be
5603 incremented or a pointer to be advanced. For example, to print
5604 a field from successive elements of an array of structures:
5608 print bar[$i++]->contents
5612 Repeat that command by typing @key{RET}.
5614 Some convenience variables are created automatically by @value{GDBN} and given
5615 values likely to be useful.
5618 @vindex $_@r{, convenience variable}
5620 The variable @code{$_} is automatically set by the @code{x} command to
5621 the last address examined (@pxref{Memory, ,Examining memory}). Other
5622 commands which provide a default address for @code{x} to examine also
5623 set @code{$_} to that address; these commands include @code{info line}
5624 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5625 except when set by the @code{x} command, in which case it is a pointer
5626 to the type of @code{$__}.
5628 @vindex $__@r{, convenience variable}
5630 The variable @code{$__} is automatically set by the @code{x} command
5631 to the value found in the last address examined. Its type is chosen
5632 to match the format in which the data was printed.
5635 @vindex $_exitcode@r{, convenience variable}
5636 The variable @code{$_exitcode} is automatically set to the exit code when
5637 the program being debugged terminates.
5640 On HP-UX systems, if you refer to a function or variable name that
5641 begins with a dollar sign, @value{GDBN} searches for a user or system
5642 name first, before it searches for a convenience variable.
5648 You can refer to machine register contents, in expressions, as variables
5649 with names starting with @samp{$}. The names of registers are different
5650 for each machine; use @code{info registers} to see the names used on
5654 @kindex info registers
5655 @item info registers
5656 Print the names and values of all registers except floating-point
5657 and vector registers (in the selected stack frame).
5659 @kindex info all-registers
5660 @cindex floating point registers
5661 @item info all-registers
5662 Print the names and values of all registers, including floating-point
5663 and vector registers (in the selected stack frame).
5665 @item info registers @var{regname} @dots{}
5666 Print the @dfn{relativized} value of each specified register @var{regname}.
5667 As discussed in detail below, register values are normally relative to
5668 the selected stack frame. @var{regname} may be any register name valid on
5669 the machine you are using, with or without the initial @samp{$}.
5672 @value{GDBN} has four ``standard'' register names that are available (in
5673 expressions) on most machines---whenever they do not conflict with an
5674 architecture's canonical mnemonics for registers. The register names
5675 @code{$pc} and @code{$sp} are used for the program counter register and
5676 the stack pointer. @code{$fp} is used for a register that contains a
5677 pointer to the current stack frame, and @code{$ps} is used for a
5678 register that contains the processor status. For example,
5679 you could print the program counter in hex with
5686 or print the instruction to be executed next with
5693 or add four to the stack pointer@footnote{This is a way of removing
5694 one word from the stack, on machines where stacks grow downward in
5695 memory (most machines, nowadays). This assumes that the innermost
5696 stack frame is selected; setting @code{$sp} is not allowed when other
5697 stack frames are selected. To pop entire frames off the stack,
5698 regardless of machine architecture, use @code{return};
5699 see @ref{Returning, ,Returning from a function}.} with
5705 Whenever possible, these four standard register names are available on
5706 your machine even though the machine has different canonical mnemonics,
5707 so long as there is no conflict. The @code{info registers} command
5708 shows the canonical names. For example, on the SPARC, @code{info
5709 registers} displays the processor status register as @code{$psr} but you
5710 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5711 is an alias for the @sc{eflags} register.
5713 @value{GDBN} always considers the contents of an ordinary register as an
5714 integer when the register is examined in this way. Some machines have
5715 special registers which can hold nothing but floating point; these
5716 registers are considered to have floating point values. There is no way
5717 to refer to the contents of an ordinary register as floating point value
5718 (although you can @emph{print} it as a floating point value with
5719 @samp{print/f $@var{regname}}).
5721 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5722 means that the data format in which the register contents are saved by
5723 the operating system is not the same one that your program normally
5724 sees. For example, the registers of the 68881 floating point
5725 coprocessor are always saved in ``extended'' (raw) format, but all C
5726 programs expect to work with ``double'' (virtual) format. In such
5727 cases, @value{GDBN} normally works with the virtual format only (the format
5728 that makes sense for your program), but the @code{info registers} command
5729 prints the data in both formats.
5731 Normally, register values are relative to the selected stack frame
5732 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5733 value that the register would contain if all stack frames farther in
5734 were exited and their saved registers restored. In order to see the
5735 true contents of hardware registers, you must select the innermost
5736 frame (with @samp{frame 0}).
5738 However, @value{GDBN} must deduce where registers are saved, from the machine
5739 code generated by your compiler. If some registers are not saved, or if
5740 @value{GDBN} is unable to locate the saved registers, the selected stack
5741 frame makes no difference.
5743 @node Floating Point Hardware
5744 @section Floating point hardware
5745 @cindex floating point
5747 Depending on the configuration, @value{GDBN} may be able to give
5748 you more information about the status of the floating point hardware.
5753 Display hardware-dependent information about the floating
5754 point unit. The exact contents and layout vary depending on the
5755 floating point chip. Currently, @samp{info float} is supported on
5756 the ARM and x86 machines.
5760 @section Vector Unit
5763 Depending on the configuration, @value{GDBN} may be able to give you
5764 more information about the status of the vector unit.
5769 Display information about the vector unit. The exact contents and
5770 layout vary depending on the hardware.
5773 @node Memory Region Attributes
5774 @section Memory region attributes
5775 @cindex memory region attributes
5777 @dfn{Memory region attributes} allow you to describe special handling
5778 required by regions of your target's memory. @value{GDBN} uses attributes
5779 to determine whether to allow certain types of memory accesses; whether to
5780 use specific width accesses; and whether to cache target memory.
5782 Defined memory regions can be individually enabled and disabled. When a
5783 memory region is disabled, @value{GDBN} uses the default attributes when
5784 accessing memory in that region. Similarly, if no memory regions have
5785 been defined, @value{GDBN} uses the default attributes when accessing
5788 When a memory region is defined, it is given a number to identify it;
5789 to enable, disable, or remove a memory region, you specify that number.
5793 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5794 Define memory region bounded by @var{lower} and @var{upper} with
5795 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5796 special case: it is treated as the the target's maximum memory address.
5797 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5800 @item delete mem @var{nums}@dots{}
5801 Remove memory regions @var{nums}@dots{}.
5804 @item disable mem @var{nums}@dots{}
5805 Disable memory regions @var{nums}@dots{}.
5806 A disabled memory region is not forgotten.
5807 It may be enabled again later.
5810 @item enable mem @var{nums}@dots{}
5811 Enable memory regions @var{nums}@dots{}.
5815 Print a table of all defined memory regions, with the following columns
5819 @item Memory Region Number
5820 @item Enabled or Disabled.
5821 Enabled memory regions are marked with @samp{y}.
5822 Disabled memory regions are marked with @samp{n}.
5825 The address defining the inclusive lower bound of the memory region.
5828 The address defining the exclusive upper bound of the memory region.
5831 The list of attributes set for this memory region.
5836 @subsection Attributes
5838 @subsubsection Memory Access Mode
5839 The access mode attributes set whether @value{GDBN} may make read or
5840 write accesses to a memory region.
5842 While these attributes prevent @value{GDBN} from performing invalid
5843 memory accesses, they do nothing to prevent the target system, I/O DMA,
5844 etc. from accessing memory.
5848 Memory is read only.
5850 Memory is write only.
5852 Memory is read/write. This is the default.
5855 @subsubsection Memory Access Size
5856 The acccess size attributes tells @value{GDBN} to use specific sized
5857 accesses in the memory region. Often memory mapped device registers
5858 require specific sized accesses. If no access size attribute is
5859 specified, @value{GDBN} may use accesses of any size.
5863 Use 8 bit memory accesses.
5865 Use 16 bit memory accesses.
5867 Use 32 bit memory accesses.
5869 Use 64 bit memory accesses.
5872 @c @subsubsection Hardware/Software Breakpoints
5873 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5874 @c will use hardware or software breakpoints for the internal breakpoints
5875 @c used by the step, next, finish, until, etc. commands.
5879 @c Always use hardware breakpoints
5880 @c @item swbreak (default)
5883 @subsubsection Data Cache
5884 The data cache attributes set whether @value{GDBN} will cache target
5885 memory. While this generally improves performance by reducing debug
5886 protocol overhead, it can lead to incorrect results because @value{GDBN}
5887 does not know about volatile variables or memory mapped device
5892 Enable @value{GDBN} to cache target memory.
5894 Disable @value{GDBN} from caching target memory. This is the default.
5897 @c @subsubsection Memory Write Verification
5898 @c The memory write verification attributes set whether @value{GDBN}
5899 @c will re-reads data after each write to verify the write was successful.
5903 @c @item noverify (default)
5906 @node Dump/Restore Files
5907 @section Copy between memory and a file
5908 @cindex dump/restore files
5909 @cindex append data to a file
5910 @cindex dump data to a file
5911 @cindex restore data from a file
5913 You can use the commands @code{dump}, @code{append}, and
5914 @code{restore} to copy data between target memory and a file. The
5915 @code{dump} and @code{append} commands write data to a file, and the
5916 @code{restore} command reads data from a file back into the inferior's
5917 memory. Files may be in binary, Motorola S-record, Intel hex, or
5918 Tektronix Hex format; however, @value{GDBN} can only append to binary
5924 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5925 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
5926 Dump the contents of memory from @var{start_addr} to @var{end_addr},
5927 or the value of @var{expr}, to @var{filename} in the given format.
5929 The @var{format} parameter may be any one of:
5936 Motorola S-record format.
5938 Tektronix Hex format.
5941 @value{GDBN} uses the same definitions of these formats as the
5942 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
5943 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
5947 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5948 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
5949 Append the contents of memory from @var{start_addr} to @var{end_addr},
5950 or the value of @var{expr}, to @var{filename}, in raw binary form.
5951 (@value{GDBN} can only append data to files in raw binary form.)
5954 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
5955 Restore the contents of file @var{filename} into memory. The
5956 @code{restore} command can automatically recognize any known @sc{bfd}
5957 file format, except for raw binary. To restore a raw binary file you
5958 must specify the optional keyword @code{binary} after the filename.
5960 If @var{bias} is non-zero, its value will be added to the addresses
5961 contained in the file. Binary files always start at address zero, so
5962 they will be restored at address @var{bias}. Other bfd files have
5963 a built-in location; they will be restored at offset @var{bias}
5966 If @var{start} and/or @var{end} are non-zero, then only data between
5967 file offset @var{start} and file offset @var{end} will be restored.
5968 These offsets are relative to the addresses in the file, before
5969 the @var{bias} argument is applied.
5973 @node Character Sets
5974 @section Character Sets
5975 @cindex character sets
5977 @cindex translating between character sets
5978 @cindex host character set
5979 @cindex target character set
5981 If the program you are debugging uses a different character set to
5982 represent characters and strings than the one @value{GDBN} uses itself,
5983 @value{GDBN} can automatically translate between the character sets for
5984 you. The character set @value{GDBN} uses we call the @dfn{host
5985 character set}; the one the inferior program uses we call the
5986 @dfn{target character set}.
5988 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5989 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5990 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5991 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5992 then the host character set is Latin-1, and the target character set is
5993 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5994 target-charset EBCDIC-US}, then @value{GDBN} translates between
5995 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5996 character and string literals in expressions.
5998 @value{GDBN} has no way to automatically recognize which character set
5999 the inferior program uses; you must tell it, using the @code{set
6000 target-charset} command, described below.
6002 Here are the commands for controlling @value{GDBN}'s character set
6006 @item set target-charset @var{charset}
6007 @kindex set target-charset
6008 Set the current target character set to @var{charset}. We list the
6009 character set names @value{GDBN} recognizes below, but if you type
6010 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6011 list the target character sets it supports.
6015 @item set host-charset @var{charset}
6016 @kindex set host-charset
6017 Set the current host character set to @var{charset}.
6019 By default, @value{GDBN} uses a host character set appropriate to the
6020 system it is running on; you can override that default using the
6021 @code{set host-charset} command.
6023 @value{GDBN} can only use certain character sets as its host character
6024 set. We list the character set names @value{GDBN} recognizes below, and
6025 indicate which can be host character sets, but if you type
6026 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6027 list the host character sets it supports.
6029 @item set charset @var{charset}
6031 Set the current host and target character sets to @var{charset}. As
6032 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6033 @value{GDBN} will list the name of the character sets that can be used
6034 for both host and target.
6038 @kindex show charset
6039 Show the names of the current host and target charsets.
6041 @itemx show host-charset
6042 @kindex show host-charset
6043 Show the name of the current host charset.
6045 @itemx show target-charset
6046 @kindex show target-charset
6047 Show the name of the current target charset.
6051 @value{GDBN} currently includes support for the following character
6057 @cindex ASCII character set
6058 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6062 @cindex ISO 8859-1 character set
6063 @cindex ISO Latin 1 character set
6064 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6065 characters needed for French, German, and Spanish. @value{GDBN} can use
6066 this as its host character set.
6070 @cindex EBCDIC character set
6071 @cindex IBM1047 character set
6072 Variants of the @sc{ebcdic} character set, used on some of IBM's
6073 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6074 @value{GDBN} cannot use these as its host character set.
6078 Note that these are all single-byte character sets. More work inside
6079 GDB is needed to support multi-byte or variable-width character
6080 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6082 Here is an example of @value{GDBN}'s character set support in action.
6083 Assume that the following source code has been placed in the file
6084 @file{charset-test.c}:
6090 = @{72, 101, 108, 108, 111, 44, 32, 119,
6091 111, 114, 108, 100, 33, 10, 0@};
6092 char ibm1047_hello[]
6093 = @{200, 133, 147, 147, 150, 107, 64, 166,
6094 150, 153, 147, 132, 90, 37, 0@};
6098 printf ("Hello, world!\n");
6102 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6103 containing the string @samp{Hello, world!} followed by a newline,
6104 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6106 We compile the program, and invoke the debugger on it:
6109 $ gcc -g charset-test.c -o charset-test
6110 $ gdb -nw charset-test
6111 GNU gdb 2001-12-19-cvs
6112 Copyright 2001 Free Software Foundation, Inc.
6117 We can use the @code{show charset} command to see what character sets
6118 @value{GDBN} is currently using to interpret and display characters and
6123 The current host and target character set is `ISO-8859-1'.
6127 For the sake of printing this manual, let's use @sc{ascii} as our
6128 initial character set:
6130 (gdb) set charset ASCII
6132 The current host and target character set is `ASCII'.
6136 Let's assume that @sc{ascii} is indeed the correct character set for our
6137 host system --- in other words, let's assume that if @value{GDBN} prints
6138 characters using the @sc{ascii} character set, our terminal will display
6139 them properly. Since our current target character set is also
6140 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6143 (gdb) print ascii_hello
6144 $1 = 0x401698 "Hello, world!\n"
6145 (gdb) print ascii_hello[0]
6150 @value{GDBN} uses the target character set for character and string
6151 literals you use in expressions:
6159 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6162 @value{GDBN} relies on the user to tell it which character set the
6163 target program uses. If we print @code{ibm1047_hello} while our target
6164 character set is still @sc{ascii}, we get jibberish:
6167 (gdb) print ibm1047_hello
6168 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6169 (gdb) print ibm1047_hello[0]
6174 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6175 @value{GDBN} tells us the character sets it supports:
6178 (gdb) set target-charset
6179 ASCII EBCDIC-US IBM1047 ISO-8859-1
6180 (gdb) set target-charset
6183 We can select @sc{ibm1047} as our target character set, and examine the
6184 program's strings again. Now the @sc{ascii} string is wrong, but
6185 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6186 target character set, @sc{ibm1047}, to the host character set,
6187 @sc{ascii}, and they display correctly:
6190 (gdb) set target-charset IBM1047
6192 The current host character set is `ASCII'.
6193 The current target character set is `IBM1047'.
6194 (gdb) print ascii_hello
6195 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6196 (gdb) print ascii_hello[0]
6198 (gdb) print ibm1047_hello
6199 $8 = 0x4016a8 "Hello, world!\n"
6200 (gdb) print ibm1047_hello[0]
6205 As above, @value{GDBN} uses the target character set for character and
6206 string literals you use in expressions:
6214 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6219 @chapter C Preprocessor Macros
6221 Some languages, such as C and C++, provide a way to define and invoke
6222 ``preprocessor macros'' which expand into strings of tokens.
6223 @value{GDBN} can evaluate expressions containing macro invocations, show
6224 the result of macro expansion, and show a macro's definition, including
6225 where it was defined.
6227 You may need to compile your program specially to provide @value{GDBN}
6228 with information about preprocessor macros. Most compilers do not
6229 include macros in their debugging information, even when you compile
6230 with the @option{-g} flag. @xref{Compilation}.
6232 A program may define a macro at one point, remove that definition later,
6233 and then provide a different definition after that. Thus, at different
6234 points in the program, a macro may have different definitions, or have
6235 no definition at all. If there is a current stack frame, @value{GDBN}
6236 uses the macros in scope at that frame's source code line. Otherwise,
6237 @value{GDBN} uses the macros in scope at the current listing location;
6240 At the moment, @value{GDBN} does not support the @code{##}
6241 token-splicing operator, the @code{#} stringification operator, or
6242 variable-arity macros.
6244 Whenever @value{GDBN} evaluates an expression, it always expands any
6245 macro invocations present in the expression. @value{GDBN} also provides
6246 the following commands for working with macros explicitly.
6250 @kindex macro expand
6251 @cindex macro expansion, showing the results of preprocessor
6252 @cindex preprocessor macro expansion, showing the results of
6253 @cindex expanding preprocessor macros
6254 @item macro expand @var{expression}
6255 @itemx macro exp @var{expression}
6256 Show the results of expanding all preprocessor macro invocations in
6257 @var{expression}. Since @value{GDBN} simply expands macros, but does
6258 not parse the result, @var{expression} need not be a valid expression;
6259 it can be any string of tokens.
6261 @kindex macro expand-once
6262 @item macro expand-once @var{expression}
6263 @itemx macro exp1 @var{expression}
6264 @i{(This command is not yet implemented.)} Show the results of
6265 expanding those preprocessor macro invocations that appear explicitly in
6266 @var{expression}. Macro invocations appearing in that expansion are
6267 left unchanged. This command allows you to see the effect of a
6268 particular macro more clearly, without being confused by further
6269 expansions. Since @value{GDBN} simply expands macros, but does not
6270 parse the result, @var{expression} need not be a valid expression; it
6271 can be any string of tokens.
6274 @cindex macro definition, showing
6275 @cindex definition, showing a macro's
6276 @item info macro @var{macro}
6277 Show the definition of the macro named @var{macro}, and describe the
6278 source location where that definition was established.
6280 @kindex macro define
6281 @cindex user-defined macros
6282 @cindex defining macros interactively
6283 @cindex macros, user-defined
6284 @item macro define @var{macro} @var{replacement-list}
6285 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6286 @i{(This command is not yet implemented.)} Introduce a definition for a
6287 preprocessor macro named @var{macro}, invocations of which are replaced
6288 by the tokens given in @var{replacement-list}. The first form of this
6289 command defines an ``object-like'' macro, which takes no arguments; the
6290 second form defines a ``function-like'' macro, which takes the arguments
6291 given in @var{arglist}.
6293 A definition introduced by this command is in scope in every expression
6294 evaluated in @value{GDBN}, until it is removed with the @command{macro
6295 undef} command, described below. The definition overrides all
6296 definitions for @var{macro} present in the program being debugged, as
6297 well as any previous user-supplied definition.
6300 @item macro undef @var{macro}
6301 @i{(This command is not yet implemented.)} Remove any user-supplied
6302 definition for the macro named @var{macro}. This command only affects
6303 definitions provided with the @command{macro define} command, described
6304 above; it cannot remove definitions present in the program being
6309 @cindex macros, example of debugging with
6310 Here is a transcript showing the above commands in action. First, we
6311 show our source files:
6319 #define ADD(x) (M + x)
6324 printf ("Hello, world!\n");
6326 printf ("We're so creative.\n");
6328 printf ("Goodbye, world!\n");
6335 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6336 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6337 compiler includes information about preprocessor macros in the debugging
6341 $ gcc -gdwarf-2 -g3 sample.c -o sample
6345 Now, we start @value{GDBN} on our sample program:
6349 GNU gdb 2002-05-06-cvs
6350 Copyright 2002 Free Software Foundation, Inc.
6351 GDB is free software, @dots{}
6355 We can expand macros and examine their definitions, even when the
6356 program is not running. @value{GDBN} uses the current listing position
6357 to decide which macro definitions are in scope:
6363 5 #define ADD(x) (M + x)
6368 10 printf ("Hello, world!\n");
6370 12 printf ("We're so creative.\n");
6371 (gdb) info macro ADD
6372 Defined at /home/jimb/gdb/macros/play/sample.c:5
6373 #define ADD(x) (M + x)
6375 Defined at /home/jimb/gdb/macros/play/sample.h:1
6376 included at /home/jimb/gdb/macros/play/sample.c:2
6378 (gdb) macro expand ADD(1)
6379 expands to: (42 + 1)
6380 (gdb) macro expand-once ADD(1)
6381 expands to: once (M + 1)
6385 In the example above, note that @command{macro expand-once} expands only
6386 the macro invocation explicit in the original text --- the invocation of
6387 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6388 which was introduced by @code{ADD}.
6390 Once the program is running, GDB uses the macro definitions in force at
6391 the source line of the current stack frame:
6395 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6397 Starting program: /home/jimb/gdb/macros/play/sample
6399 Breakpoint 1, main () at sample.c:10
6400 10 printf ("Hello, world!\n");
6404 At line 10, the definition of the macro @code{N} at line 9 is in force:
6408 Defined at /home/jimb/gdb/macros/play/sample.c:9
6410 (gdb) macro expand N Q M
6417 As we step over directives that remove @code{N}'s definition, and then
6418 give it a new definition, @value{GDBN} finds the definition (or lack
6419 thereof) in force at each point:
6424 12 printf ("We're so creative.\n");
6426 The symbol `N' has no definition as a C/C++ preprocessor macro
6427 at /home/jimb/gdb/macros/play/sample.c:12
6430 14 printf ("Goodbye, world!\n");
6432 Defined at /home/jimb/gdb/macros/play/sample.c:13
6434 (gdb) macro expand N Q M
6435 expands to: 1729 < 42
6443 @chapter Tracepoints
6444 @c This chapter is based on the documentation written by Michael
6445 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6448 In some applications, it is not feasible for the debugger to interrupt
6449 the program's execution long enough for the developer to learn
6450 anything helpful about its behavior. If the program's correctness
6451 depends on its real-time behavior, delays introduced by a debugger
6452 might cause the program to change its behavior drastically, or perhaps
6453 fail, even when the code itself is correct. It is useful to be able
6454 to observe the program's behavior without interrupting it.
6456 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6457 specify locations in the program, called @dfn{tracepoints}, and
6458 arbitrary expressions to evaluate when those tracepoints are reached.
6459 Later, using the @code{tfind} command, you can examine the values
6460 those expressions had when the program hit the tracepoints. The
6461 expressions may also denote objects in memory---structures or arrays,
6462 for example---whose values @value{GDBN} should record; while visiting
6463 a particular tracepoint, you may inspect those objects as if they were
6464 in memory at that moment. However, because @value{GDBN} records these
6465 values without interacting with you, it can do so quickly and
6466 unobtrusively, hopefully not disturbing the program's behavior.
6468 The tracepoint facility is currently available only for remote
6469 targets. @xref{Targets}. In addition, your remote target must know how
6470 to collect trace data. This functionality is implemented in the remote
6471 stub; however, none of the stubs distributed with @value{GDBN} support
6472 tracepoints as of this writing.
6474 This chapter describes the tracepoint commands and features.
6478 * Analyze Collected Data::
6479 * Tracepoint Variables::
6482 @node Set Tracepoints
6483 @section Commands to Set Tracepoints
6485 Before running such a @dfn{trace experiment}, an arbitrary number of
6486 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6487 tracepoint has a number assigned to it by @value{GDBN}. Like with
6488 breakpoints, tracepoint numbers are successive integers starting from
6489 one. Many of the commands associated with tracepoints take the
6490 tracepoint number as their argument, to identify which tracepoint to
6493 For each tracepoint, you can specify, in advance, some arbitrary set
6494 of data that you want the target to collect in the trace buffer when
6495 it hits that tracepoint. The collected data can include registers,
6496 local variables, or global data. Later, you can use @value{GDBN}
6497 commands to examine the values these data had at the time the
6500 This section describes commands to set tracepoints and associated
6501 conditions and actions.
6504 * Create and Delete Tracepoints::
6505 * Enable and Disable Tracepoints::
6506 * Tracepoint Passcounts::
6507 * Tracepoint Actions::
6508 * Listing Tracepoints::
6509 * Starting and Stopping Trace Experiment::
6512 @node Create and Delete Tracepoints
6513 @subsection Create and Delete Tracepoints
6516 @cindex set tracepoint
6519 The @code{trace} command is very similar to the @code{break} command.
6520 Its argument can be a source line, a function name, or an address in
6521 the target program. @xref{Set Breaks}. The @code{trace} command
6522 defines a tracepoint, which is a point in the target program where the
6523 debugger will briefly stop, collect some data, and then allow the
6524 program to continue. Setting a tracepoint or changing its commands
6525 doesn't take effect until the next @code{tstart} command; thus, you
6526 cannot change the tracepoint attributes once a trace experiment is
6529 Here are some examples of using the @code{trace} command:
6532 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6534 (@value{GDBP}) @b{trace +2} // 2 lines forward
6536 (@value{GDBP}) @b{trace my_function} // first source line of function
6538 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6540 (@value{GDBP}) @b{trace *0x2117c4} // an address
6544 You can abbreviate @code{trace} as @code{tr}.
6547 @cindex last tracepoint number
6548 @cindex recent tracepoint number
6549 @cindex tracepoint number
6550 The convenience variable @code{$tpnum} records the tracepoint number
6551 of the most recently set tracepoint.
6553 @kindex delete tracepoint
6554 @cindex tracepoint deletion
6555 @item delete tracepoint @r{[}@var{num}@r{]}
6556 Permanently delete one or more tracepoints. With no argument, the
6557 default is to delete all tracepoints.
6562 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6564 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6568 You can abbreviate this command as @code{del tr}.
6571 @node Enable and Disable Tracepoints
6572 @subsection Enable and Disable Tracepoints
6575 @kindex disable tracepoint
6576 @item disable tracepoint @r{[}@var{num}@r{]}
6577 Disable tracepoint @var{num}, or all tracepoints if no argument
6578 @var{num} is given. A disabled tracepoint will have no effect during
6579 the next trace experiment, but it is not forgotten. You can re-enable
6580 a disabled tracepoint using the @code{enable tracepoint} command.
6582 @kindex enable tracepoint
6583 @item enable tracepoint @r{[}@var{num}@r{]}
6584 Enable tracepoint @var{num}, or all tracepoints. The enabled
6585 tracepoints will become effective the next time a trace experiment is
6589 @node Tracepoint Passcounts
6590 @subsection Tracepoint Passcounts
6594 @cindex tracepoint pass count
6595 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6596 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6597 automatically stop a trace experiment. If a tracepoint's passcount is
6598 @var{n}, then the trace experiment will be automatically stopped on
6599 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6600 @var{num} is not specified, the @code{passcount} command sets the
6601 passcount of the most recently defined tracepoint. If no passcount is
6602 given, the trace experiment will run until stopped explicitly by the
6608 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6609 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6611 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6612 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6613 (@value{GDBP}) @b{trace foo}
6614 (@value{GDBP}) @b{pass 3}
6615 (@value{GDBP}) @b{trace bar}
6616 (@value{GDBP}) @b{pass 2}
6617 (@value{GDBP}) @b{trace baz}
6618 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6619 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6620 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6621 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6625 @node Tracepoint Actions
6626 @subsection Tracepoint Action Lists
6630 @cindex tracepoint actions
6631 @item actions @r{[}@var{num}@r{]}
6632 This command will prompt for a list of actions to be taken when the
6633 tracepoint is hit. If the tracepoint number @var{num} is not
6634 specified, this command sets the actions for the one that was most
6635 recently defined (so that you can define a tracepoint and then say
6636 @code{actions} without bothering about its number). You specify the
6637 actions themselves on the following lines, one action at a time, and
6638 terminate the actions list with a line containing just @code{end}. So
6639 far, the only defined actions are @code{collect} and
6640 @code{while-stepping}.
6642 @cindex remove actions from a tracepoint
6643 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6644 and follow it immediately with @samp{end}.
6647 (@value{GDBP}) @b{collect @var{data}} // collect some data
6649 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6651 (@value{GDBP}) @b{end} // signals the end of actions.
6654 In the following example, the action list begins with @code{collect}
6655 commands indicating the things to be collected when the tracepoint is
6656 hit. Then, in order to single-step and collect additional data
6657 following the tracepoint, a @code{while-stepping} command is used,
6658 followed by the list of things to be collected while stepping. The
6659 @code{while-stepping} command is terminated by its own separate
6660 @code{end} command. Lastly, the action list is terminated by an
6664 (@value{GDBP}) @b{trace foo}
6665 (@value{GDBP}) @b{actions}
6666 Enter actions for tracepoint 1, one per line:
6675 @kindex collect @r{(tracepoints)}
6676 @item collect @var{expr1}, @var{expr2}, @dots{}
6677 Collect values of the given expressions when the tracepoint is hit.
6678 This command accepts a comma-separated list of any valid expressions.
6679 In addition to global, static, or local variables, the following
6680 special arguments are supported:
6684 collect all registers
6687 collect all function arguments
6690 collect all local variables.
6693 You can give several consecutive @code{collect} commands, each one
6694 with a single argument, or one @code{collect} command with several
6695 arguments separated by commas: the effect is the same.
6697 The command @code{info scope} (@pxref{Symbols, info scope}) is
6698 particularly useful for figuring out what data to collect.
6700 @kindex while-stepping @r{(tracepoints)}
6701 @item while-stepping @var{n}
6702 Perform @var{n} single-step traces after the tracepoint, collecting
6703 new data at each step. The @code{while-stepping} command is
6704 followed by the list of what to collect while stepping (followed by
6705 its own @code{end} command):
6709 > collect $regs, myglobal
6715 You may abbreviate @code{while-stepping} as @code{ws} or
6719 @node Listing Tracepoints
6720 @subsection Listing Tracepoints
6723 @kindex info tracepoints
6724 @cindex information about tracepoints
6725 @item info tracepoints @r{[}@var{num}@r{]}
6726 Display information about the tracepoint @var{num}. If you don't specify
6727 a tracepoint number, displays information about all the tracepoints
6728 defined so far. For each tracepoint, the following information is
6735 whether it is enabled or disabled
6739 its passcount as given by the @code{passcount @var{n}} command
6741 its step count as given by the @code{while-stepping @var{n}} command
6743 where in the source files is the tracepoint set
6745 its action list as given by the @code{actions} command
6749 (@value{GDBP}) @b{info trace}
6750 Num Enb Address PassC StepC What
6751 1 y 0x002117c4 0 0 <gdb_asm>
6752 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6753 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6758 This command can be abbreviated @code{info tp}.
6761 @node Starting and Stopping Trace Experiment
6762 @subsection Starting and Stopping Trace Experiment
6766 @cindex start a new trace experiment
6767 @cindex collected data discarded
6769 This command takes no arguments. It starts the trace experiment, and
6770 begins collecting data. This has the side effect of discarding all
6771 the data collected in the trace buffer during the previous trace
6775 @cindex stop a running trace experiment
6777 This command takes no arguments. It ends the trace experiment, and
6778 stops collecting data.
6780 @strong{Note:} a trace experiment and data collection may stop
6781 automatically if any tracepoint's passcount is reached
6782 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6785 @cindex status of trace data collection
6786 @cindex trace experiment, status of
6788 This command displays the status of the current trace data
6792 Here is an example of the commands we described so far:
6795 (@value{GDBP}) @b{trace gdb_c_test}
6796 (@value{GDBP}) @b{actions}
6797 Enter actions for tracepoint #1, one per line.
6798 > collect $regs,$locals,$args
6803 (@value{GDBP}) @b{tstart}
6804 [time passes @dots{}]
6805 (@value{GDBP}) @b{tstop}
6809 @node Analyze Collected Data
6810 @section Using the collected data
6812 After the tracepoint experiment ends, you use @value{GDBN} commands
6813 for examining the trace data. The basic idea is that each tracepoint
6814 collects a trace @dfn{snapshot} every time it is hit and another
6815 snapshot every time it single-steps. All these snapshots are
6816 consecutively numbered from zero and go into a buffer, and you can
6817 examine them later. The way you examine them is to @dfn{focus} on a
6818 specific trace snapshot. When the remote stub is focused on a trace
6819 snapshot, it will respond to all @value{GDBN} requests for memory and
6820 registers by reading from the buffer which belongs to that snapshot,
6821 rather than from @emph{real} memory or registers of the program being
6822 debugged. This means that @strong{all} @value{GDBN} commands
6823 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6824 behave as if we were currently debugging the program state as it was
6825 when the tracepoint occurred. Any requests for data that are not in
6826 the buffer will fail.
6829 * tfind:: How to select a trace snapshot
6830 * tdump:: How to display all data for a snapshot
6831 * save-tracepoints:: How to save tracepoints for a future run
6835 @subsection @code{tfind @var{n}}
6838 @cindex select trace snapshot
6839 @cindex find trace snapshot
6840 The basic command for selecting a trace snapshot from the buffer is
6841 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6842 counting from zero. If no argument @var{n} is given, the next
6843 snapshot is selected.
6845 Here are the various forms of using the @code{tfind} command.
6849 Find the first snapshot in the buffer. This is a synonym for
6850 @code{tfind 0} (since 0 is the number of the first snapshot).
6853 Stop debugging trace snapshots, resume @emph{live} debugging.
6856 Same as @samp{tfind none}.
6859 No argument means find the next trace snapshot.
6862 Find the previous trace snapshot before the current one. This permits
6863 retracing earlier steps.
6865 @item tfind tracepoint @var{num}
6866 Find the next snapshot associated with tracepoint @var{num}. Search
6867 proceeds forward from the last examined trace snapshot. If no
6868 argument @var{num} is given, it means find the next snapshot collected
6869 for the same tracepoint as the current snapshot.
6871 @item tfind pc @var{addr}
6872 Find the next snapshot associated with the value @var{addr} of the
6873 program counter. Search proceeds forward from the last examined trace
6874 snapshot. If no argument @var{addr} is given, it means find the next
6875 snapshot with the same value of PC as the current snapshot.
6877 @item tfind outside @var{addr1}, @var{addr2}
6878 Find the next snapshot whose PC is outside the given range of
6881 @item tfind range @var{addr1}, @var{addr2}
6882 Find the next snapshot whose PC is between @var{addr1} and
6883 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6885 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6886 Find the next snapshot associated with the source line @var{n}. If
6887 the optional argument @var{file} is given, refer to line @var{n} in
6888 that source file. Search proceeds forward from the last examined
6889 trace snapshot. If no argument @var{n} is given, it means find the
6890 next line other than the one currently being examined; thus saying
6891 @code{tfind line} repeatedly can appear to have the same effect as
6892 stepping from line to line in a @emph{live} debugging session.
6895 The default arguments for the @code{tfind} commands are specifically
6896 designed to make it easy to scan through the trace buffer. For
6897 instance, @code{tfind} with no argument selects the next trace
6898 snapshot, and @code{tfind -} with no argument selects the previous
6899 trace snapshot. So, by giving one @code{tfind} command, and then
6900 simply hitting @key{RET} repeatedly you can examine all the trace
6901 snapshots in order. Or, by saying @code{tfind -} and then hitting
6902 @key{RET} repeatedly you can examine the snapshots in reverse order.
6903 The @code{tfind line} command with no argument selects the snapshot
6904 for the next source line executed. The @code{tfind pc} command with
6905 no argument selects the next snapshot with the same program counter
6906 (PC) as the current frame. The @code{tfind tracepoint} command with
6907 no argument selects the next trace snapshot collected by the same
6908 tracepoint as the current one.
6910 In addition to letting you scan through the trace buffer manually,
6911 these commands make it easy to construct @value{GDBN} scripts that
6912 scan through the trace buffer and print out whatever collected data
6913 you are interested in. Thus, if we want to examine the PC, FP, and SP
6914 registers from each trace frame in the buffer, we can say this:
6917 (@value{GDBP}) @b{tfind start}
6918 (@value{GDBP}) @b{while ($trace_frame != -1)}
6919 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6920 $trace_frame, $pc, $sp, $fp
6924 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6925 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6926 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6927 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6928 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6929 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6930 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6931 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6932 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6933 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6934 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6937 Or, if we want to examine the variable @code{X} at each source line in
6941 (@value{GDBP}) @b{tfind start}
6942 (@value{GDBP}) @b{while ($trace_frame != -1)}
6943 > printf "Frame %d, X == %d\n", $trace_frame, X
6953 @subsection @code{tdump}
6955 @cindex dump all data collected at tracepoint
6956 @cindex tracepoint data, display
6958 This command takes no arguments. It prints all the data collected at
6959 the current trace snapshot.
6962 (@value{GDBP}) @b{trace 444}
6963 (@value{GDBP}) @b{actions}
6964 Enter actions for tracepoint #2, one per line:
6965 > collect $regs, $locals, $args, gdb_long_test
6968 (@value{GDBP}) @b{tstart}
6970 (@value{GDBP}) @b{tfind line 444}
6971 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6973 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6975 (@value{GDBP}) @b{tdump}
6976 Data collected at tracepoint 2, trace frame 1:
6977 d0 0xc4aa0085 -995491707
6981 d4 0x71aea3d 119204413
6986 a1 0x3000668 50333288
6989 a4 0x3000698 50333336
6991 fp 0x30bf3c 0x30bf3c
6992 sp 0x30bf34 0x30bf34
6994 pc 0x20b2c8 0x20b2c8
6998 p = 0x20e5b4 "gdb-test"
7005 gdb_long_test = 17 '\021'
7010 @node save-tracepoints
7011 @subsection @code{save-tracepoints @var{filename}}
7012 @kindex save-tracepoints
7013 @cindex save tracepoints for future sessions
7015 This command saves all current tracepoint definitions together with
7016 their actions and passcounts, into a file @file{@var{filename}}
7017 suitable for use in a later debugging session. To read the saved
7018 tracepoint definitions, use the @code{source} command (@pxref{Command
7021 @node Tracepoint Variables
7022 @section Convenience Variables for Tracepoints
7023 @cindex tracepoint variables
7024 @cindex convenience variables for tracepoints
7027 @vindex $trace_frame
7028 @item (int) $trace_frame
7029 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7030 snapshot is selected.
7033 @item (int) $tracepoint
7034 The tracepoint for the current trace snapshot.
7037 @item (int) $trace_line
7038 The line number for the current trace snapshot.
7041 @item (char []) $trace_file
7042 The source file for the current trace snapshot.
7045 @item (char []) $trace_func
7046 The name of the function containing @code{$tracepoint}.
7049 Note: @code{$trace_file} is not suitable for use in @code{printf},
7050 use @code{output} instead.
7052 Here's a simple example of using these convenience variables for
7053 stepping through all the trace snapshots and printing some of their
7057 (@value{GDBP}) @b{tfind start}
7059 (@value{GDBP}) @b{while $trace_frame != -1}
7060 > output $trace_file
7061 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7067 @chapter Debugging Programs That Use Overlays
7070 If your program is too large to fit completely in your target system's
7071 memory, you can sometimes use @dfn{overlays} to work around this
7072 problem. @value{GDBN} provides some support for debugging programs that
7076 * How Overlays Work:: A general explanation of overlays.
7077 * Overlay Commands:: Managing overlays in @value{GDBN}.
7078 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7079 mapped by asking the inferior.
7080 * Overlay Sample Program:: A sample program using overlays.
7083 @node How Overlays Work
7084 @section How Overlays Work
7085 @cindex mapped overlays
7086 @cindex unmapped overlays
7087 @cindex load address, overlay's
7088 @cindex mapped address
7089 @cindex overlay area
7091 Suppose you have a computer whose instruction address space is only 64
7092 kilobytes long, but which has much more memory which can be accessed by
7093 other means: special instructions, segment registers, or memory
7094 management hardware, for example. Suppose further that you want to
7095 adapt a program which is larger than 64 kilobytes to run on this system.
7097 One solution is to identify modules of your program which are relatively
7098 independent, and need not call each other directly; call these modules
7099 @dfn{overlays}. Separate the overlays from the main program, and place
7100 their machine code in the larger memory. Place your main program in
7101 instruction memory, but leave at least enough space there to hold the
7102 largest overlay as well.
7104 Now, to call a function located in an overlay, you must first copy that
7105 overlay's machine code from the large memory into the space set aside
7106 for it in the instruction memory, and then jump to its entry point
7109 @c NB: In the below the mapped area's size is greater or equal to the
7110 @c size of all overlays. This is intentional to remind the developer
7111 @c that overlays don't necessarily need to be the same size.
7115 Data Instruction Larger
7116 Address Space Address Space Address Space
7117 +-----------+ +-----------+ +-----------+
7119 +-----------+ +-----------+ +-----------+<-- overlay 1
7120 | program | | main | .----| overlay 1 | load address
7121 | variables | | program | | +-----------+
7122 | and heap | | | | | |
7123 +-----------+ | | | +-----------+<-- overlay 2
7124 | | +-----------+ | | | load address
7125 +-----------+ | | | .-| overlay 2 |
7127 mapped --->+-----------+ | | +-----------+
7129 | overlay | <-' | | |
7130 | area | <---' +-----------+<-- overlay 3
7131 | | <---. | | load address
7132 +-----------+ `--| overlay 3 |
7139 @anchor{A code overlay}A code overlay
7143 The diagram (@pxref{A code overlay}) shows a system with separate data
7144 and instruction address spaces. To map an overlay, the program copies
7145 its code from the larger address space to the instruction address space.
7146 Since the overlays shown here all use the same mapped address, only one
7147 may be mapped at a time. For a system with a single address space for
7148 data and instructions, the diagram would be similar, except that the
7149 program variables and heap would share an address space with the main
7150 program and the overlay area.
7152 An overlay loaded into instruction memory and ready for use is called a
7153 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7154 instruction memory. An overlay not present (or only partially present)
7155 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7156 is its address in the larger memory. The mapped address is also called
7157 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7158 called the @dfn{load memory address}, or @dfn{LMA}.
7160 Unfortunately, overlays are not a completely transparent way to adapt a
7161 program to limited instruction memory. They introduce a new set of
7162 global constraints you must keep in mind as you design your program:
7167 Before calling or returning to a function in an overlay, your program
7168 must make sure that overlay is actually mapped. Otherwise, the call or
7169 return will transfer control to the right address, but in the wrong
7170 overlay, and your program will probably crash.
7173 If the process of mapping an overlay is expensive on your system, you
7174 will need to choose your overlays carefully to minimize their effect on
7175 your program's performance.
7178 The executable file you load onto your system must contain each
7179 overlay's instructions, appearing at the overlay's load address, not its
7180 mapped address. However, each overlay's instructions must be relocated
7181 and its symbols defined as if the overlay were at its mapped address.
7182 You can use GNU linker scripts to specify different load and relocation
7183 addresses for pieces of your program; see @ref{Overlay Description,,,
7184 ld.info, Using ld: the GNU linker}.
7187 The procedure for loading executable files onto your system must be able
7188 to load their contents into the larger address space as well as the
7189 instruction and data spaces.
7193 The overlay system described above is rather simple, and could be
7194 improved in many ways:
7199 If your system has suitable bank switch registers or memory management
7200 hardware, you could use those facilities to make an overlay's load area
7201 contents simply appear at their mapped address in instruction space.
7202 This would probably be faster than copying the overlay to its mapped
7203 area in the usual way.
7206 If your overlays are small enough, you could set aside more than one
7207 overlay area, and have more than one overlay mapped at a time.
7210 You can use overlays to manage data, as well as instructions. In
7211 general, data overlays are even less transparent to your design than
7212 code overlays: whereas code overlays only require care when you call or
7213 return to functions, data overlays require care every time you access
7214 the data. Also, if you change the contents of a data overlay, you
7215 must copy its contents back out to its load address before you can copy a
7216 different data overlay into the same mapped area.
7221 @node Overlay Commands
7222 @section Overlay Commands
7224 To use @value{GDBN}'s overlay support, each overlay in your program must
7225 correspond to a separate section of the executable file. The section's
7226 virtual memory address and load memory address must be the overlay's
7227 mapped and load addresses. Identifying overlays with sections allows
7228 @value{GDBN} to determine the appropriate address of a function or
7229 variable, depending on whether the overlay is mapped or not.
7231 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7232 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7237 Disable @value{GDBN}'s overlay support. When overlay support is
7238 disabled, @value{GDBN} assumes that all functions and variables are
7239 always present at their mapped addresses. By default, @value{GDBN}'s
7240 overlay support is disabled.
7242 @item overlay manual
7243 @kindex overlay manual
7244 @cindex manual overlay debugging
7245 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7246 relies on you to tell it which overlays are mapped, and which are not,
7247 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7248 commands described below.
7250 @item overlay map-overlay @var{overlay}
7251 @itemx overlay map @var{overlay}
7252 @kindex overlay map-overlay
7253 @cindex map an overlay
7254 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7255 be the name of the object file section containing the overlay. When an
7256 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7257 functions and variables at their mapped addresses. @value{GDBN} assumes
7258 that any other overlays whose mapped ranges overlap that of
7259 @var{overlay} are now unmapped.
7261 @item overlay unmap-overlay @var{overlay}
7262 @itemx overlay unmap @var{overlay}
7263 @kindex overlay unmap-overlay
7264 @cindex unmap an overlay
7265 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7266 must be the name of the object file section containing the overlay.
7267 When an overlay is unmapped, @value{GDBN} assumes it can find the
7268 overlay's functions and variables at their load addresses.
7271 @kindex overlay auto
7272 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7273 consults a data structure the overlay manager maintains in the inferior
7274 to see which overlays are mapped. For details, see @ref{Automatic
7277 @item overlay load-target
7279 @kindex overlay load-target
7280 @cindex reloading the overlay table
7281 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7282 re-reads the table @value{GDBN} automatically each time the inferior
7283 stops, so this command should only be necessary if you have changed the
7284 overlay mapping yourself using @value{GDBN}. This command is only
7285 useful when using automatic overlay debugging.
7287 @item overlay list-overlays
7289 @cindex listing mapped overlays
7290 Display a list of the overlays currently mapped, along with their mapped
7291 addresses, load addresses, and sizes.
7295 Normally, when @value{GDBN} prints a code address, it includes the name
7296 of the function the address falls in:
7300 $3 = @{int ()@} 0x11a0 <main>
7303 When overlay debugging is enabled, @value{GDBN} recognizes code in
7304 unmapped overlays, and prints the names of unmapped functions with
7305 asterisks around them. For example, if @code{foo} is a function in an
7306 unmapped overlay, @value{GDBN} prints it this way:
7310 No sections are mapped.
7312 $5 = @{int (int)@} 0x100000 <*foo*>
7315 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7320 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7321 mapped at 0x1016 - 0x104a
7323 $6 = @{int (int)@} 0x1016 <foo>
7326 When overlay debugging is enabled, @value{GDBN} can find the correct
7327 address for functions and variables in an overlay, whether or not the
7328 overlay is mapped. This allows most @value{GDBN} commands, like
7329 @code{break} and @code{disassemble}, to work normally, even on unmapped
7330 code. However, @value{GDBN}'s breakpoint support has some limitations:
7334 @cindex breakpoints in overlays
7335 @cindex overlays, setting breakpoints in
7336 You can set breakpoints in functions in unmapped overlays, as long as
7337 @value{GDBN} can write to the overlay at its load address.
7339 @value{GDBN} can not set hardware or simulator-based breakpoints in
7340 unmapped overlays. However, if you set a breakpoint at the end of your
7341 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7342 you are using manual overlay management), @value{GDBN} will re-set its
7343 breakpoints properly.
7347 @node Automatic Overlay Debugging
7348 @section Automatic Overlay Debugging
7349 @cindex automatic overlay debugging
7351 @value{GDBN} can automatically track which overlays are mapped and which
7352 are not, given some simple co-operation from the overlay manager in the
7353 inferior. If you enable automatic overlay debugging with the
7354 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7355 looks in the inferior's memory for certain variables describing the
7356 current state of the overlays.
7358 Here are the variables your overlay manager must define to support
7359 @value{GDBN}'s automatic overlay debugging:
7363 @item @code{_ovly_table}:
7364 This variable must be an array of the following structures:
7369 /* The overlay's mapped address. */
7372 /* The size of the overlay, in bytes. */
7375 /* The overlay's load address. */
7378 /* Non-zero if the overlay is currently mapped;
7380 unsigned long mapped;
7384 @item @code{_novlys}:
7385 This variable must be a four-byte signed integer, holding the total
7386 number of elements in @code{_ovly_table}.
7390 To decide whether a particular overlay is mapped or not, @value{GDBN}
7391 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7392 @code{lma} members equal the VMA and LMA of the overlay's section in the
7393 executable file. When @value{GDBN} finds a matching entry, it consults
7394 the entry's @code{mapped} member to determine whether the overlay is
7397 In addition, your overlay manager may define a function called
7398 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7399 will silently set a breakpoint there. If the overlay manager then
7400 calls this function whenever it has changed the overlay table, this
7401 will enable @value{GDBN} to accurately keep track of which overlays
7402 are in program memory, and update any breakpoints that may be set
7403 in overlays. This will allow breakpoints to work even if the
7404 overlays are kept in ROM or other non-writable memory while they
7405 are not being executed.
7407 @node Overlay Sample Program
7408 @section Overlay Sample Program
7409 @cindex overlay example program
7411 When linking a program which uses overlays, you must place the overlays
7412 at their load addresses, while relocating them to run at their mapped
7413 addresses. To do this, you must write a linker script (@pxref{Overlay
7414 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7415 since linker scripts are specific to a particular host system, target
7416 architecture, and target memory layout, this manual cannot provide
7417 portable sample code demonstrating @value{GDBN}'s overlay support.
7419 However, the @value{GDBN} source distribution does contain an overlaid
7420 program, with linker scripts for a few systems, as part of its test
7421 suite. The program consists of the following files from
7422 @file{gdb/testsuite/gdb.base}:
7426 The main program file.
7428 A simple overlay manager, used by @file{overlays.c}.
7433 Overlay modules, loaded and used by @file{overlays.c}.
7436 Linker scripts for linking the test program on the @code{d10v-elf}
7437 and @code{m32r-elf} targets.
7440 You can build the test program using the @code{d10v-elf} GCC
7441 cross-compiler like this:
7444 $ d10v-elf-gcc -g -c overlays.c
7445 $ d10v-elf-gcc -g -c ovlymgr.c
7446 $ d10v-elf-gcc -g -c foo.c
7447 $ d10v-elf-gcc -g -c bar.c
7448 $ d10v-elf-gcc -g -c baz.c
7449 $ d10v-elf-gcc -g -c grbx.c
7450 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7451 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7454 The build process is identical for any other architecture, except that
7455 you must substitute the appropriate compiler and linker script for the
7456 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7460 @chapter Using @value{GDBN} with Different Languages
7463 Although programming languages generally have common aspects, they are
7464 rarely expressed in the same manner. For instance, in ANSI C,
7465 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7466 Modula-2, it is accomplished by @code{p^}. Values can also be
7467 represented (and displayed) differently. Hex numbers in C appear as
7468 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7470 @cindex working language
7471 Language-specific information is built into @value{GDBN} for some languages,
7472 allowing you to express operations like the above in your program's
7473 native language, and allowing @value{GDBN} to output values in a manner
7474 consistent with the syntax of your program's native language. The
7475 language you use to build expressions is called the @dfn{working
7479 * Setting:: Switching between source languages
7480 * Show:: Displaying the language
7481 * Checks:: Type and range checks
7482 * Support:: Supported languages
7483 * Unsupported languages:: Unsupported languages
7487 @section Switching between source languages
7489 There are two ways to control the working language---either have @value{GDBN}
7490 set it automatically, or select it manually yourself. You can use the
7491 @code{set language} command for either purpose. On startup, @value{GDBN}
7492 defaults to setting the language automatically. The working language is
7493 used to determine how expressions you type are interpreted, how values
7496 In addition to the working language, every source file that
7497 @value{GDBN} knows about has its own working language. For some object
7498 file formats, the compiler might indicate which language a particular
7499 source file is in. However, most of the time @value{GDBN} infers the
7500 language from the name of the file. The language of a source file
7501 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7502 show each frame appropriately for its own language. There is no way to
7503 set the language of a source file from within @value{GDBN}, but you can
7504 set the language associated with a filename extension. @xref{Show, ,
7505 Displaying the language}.
7507 This is most commonly a problem when you use a program, such
7508 as @code{cfront} or @code{f2c}, that generates C but is written in
7509 another language. In that case, make the
7510 program use @code{#line} directives in its C output; that way
7511 @value{GDBN} will know the correct language of the source code of the original
7512 program, and will display that source code, not the generated C code.
7515 * Filenames:: Filename extensions and languages.
7516 * Manually:: Setting the working language manually
7517 * Automatically:: Having @value{GDBN} infer the source language
7521 @subsection List of filename extensions and languages
7523 If a source file name ends in one of the following extensions, then
7524 @value{GDBN} infers that its language is the one indicated.
7540 Objective-C source file
7547 Modula-2 source file
7551 Assembler source file. This actually behaves almost like C, but
7552 @value{GDBN} does not skip over function prologues when stepping.
7555 In addition, you may set the language associated with a filename
7556 extension. @xref{Show, , Displaying the language}.
7559 @subsection Setting the working language
7561 If you allow @value{GDBN} to set the language automatically,
7562 expressions are interpreted the same way in your debugging session and
7565 @kindex set language
7566 If you wish, you may set the language manually. To do this, issue the
7567 command @samp{set language @var{lang}}, where @var{lang} is the name of
7569 @code{c} or @code{modula-2}.
7570 For a list of the supported languages, type @samp{set language}.
7572 Setting the language manually prevents @value{GDBN} from updating the working
7573 language automatically. This can lead to confusion if you try
7574 to debug a program when the working language is not the same as the
7575 source language, when an expression is acceptable to both
7576 languages---but means different things. For instance, if the current
7577 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7585 might not have the effect you intended. In C, this means to add
7586 @code{b} and @code{c} and place the result in @code{a}. The result
7587 printed would be the value of @code{a}. In Modula-2, this means to compare
7588 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7591 @subsection Having @value{GDBN} infer the source language
7593 To have @value{GDBN} set the working language automatically, use
7594 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7595 then infers the working language. That is, when your program stops in a
7596 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7597 working language to the language recorded for the function in that
7598 frame. If the language for a frame is unknown (that is, if the function
7599 or block corresponding to the frame was defined in a source file that
7600 does not have a recognized extension), the current working language is
7601 not changed, and @value{GDBN} issues a warning.
7603 This may not seem necessary for most programs, which are written
7604 entirely in one source language. However, program modules and libraries
7605 written in one source language can be used by a main program written in
7606 a different source language. Using @samp{set language auto} in this
7607 case frees you from having to set the working language manually.
7610 @section Displaying the language
7612 The following commands help you find out which language is the
7613 working language, and also what language source files were written in.
7615 @kindex show language
7616 @kindex info frame@r{, show the source language}
7617 @kindex info source@r{, show the source language}
7620 Display the current working language. This is the
7621 language you can use with commands such as @code{print} to
7622 build and compute expressions that may involve variables in your program.
7625 Display the source language for this frame. This language becomes the
7626 working language if you use an identifier from this frame.
7627 @xref{Frame Info, ,Information about a frame}, to identify the other
7628 information listed here.
7631 Display the source language of this source file.
7632 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7633 information listed here.
7636 In unusual circumstances, you may have source files with extensions
7637 not in the standard list. You can then set the extension associated
7638 with a language explicitly:
7640 @kindex set extension-language
7641 @kindex info extensions
7643 @item set extension-language @var{.ext} @var{language}
7644 Set source files with extension @var{.ext} to be assumed to be in
7645 the source language @var{language}.
7647 @item info extensions
7648 List all the filename extensions and the associated languages.
7652 @section Type and range checking
7655 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7656 checking are included, but they do not yet have any effect. This
7657 section documents the intended facilities.
7659 @c FIXME remove warning when type/range code added
7661 Some languages are designed to guard you against making seemingly common
7662 errors through a series of compile- and run-time checks. These include
7663 checking the type of arguments to functions and operators, and making
7664 sure mathematical overflows are caught at run time. Checks such as
7665 these help to ensure a program's correctness once it has been compiled
7666 by eliminating type mismatches, and providing active checks for range
7667 errors when your program is running.
7669 @value{GDBN} can check for conditions like the above if you wish.
7670 Although @value{GDBN} does not check the statements in your program, it
7671 can check expressions entered directly into @value{GDBN} for evaluation via
7672 the @code{print} command, for example. As with the working language,
7673 @value{GDBN} can also decide whether or not to check automatically based on
7674 your program's source language. @xref{Support, ,Supported languages},
7675 for the default settings of supported languages.
7678 * Type Checking:: An overview of type checking
7679 * Range Checking:: An overview of range checking
7682 @cindex type checking
7683 @cindex checks, type
7685 @subsection An overview of type checking
7687 Some languages, such as Modula-2, are strongly typed, meaning that the
7688 arguments to operators and functions have to be of the correct type,
7689 otherwise an error occurs. These checks prevent type mismatch
7690 errors from ever causing any run-time problems. For example,
7698 The second example fails because the @code{CARDINAL} 1 is not
7699 type-compatible with the @code{REAL} 2.3.
7701 For the expressions you use in @value{GDBN} commands, you can tell the
7702 @value{GDBN} type checker to skip checking;
7703 to treat any mismatches as errors and abandon the expression;
7704 or to only issue warnings when type mismatches occur,
7705 but evaluate the expression anyway. When you choose the last of
7706 these, @value{GDBN} evaluates expressions like the second example above, but
7707 also issues a warning.
7709 Even if you turn type checking off, there may be other reasons
7710 related to type that prevent @value{GDBN} from evaluating an expression.
7711 For instance, @value{GDBN} does not know how to add an @code{int} and
7712 a @code{struct foo}. These particular type errors have nothing to do
7713 with the language in use, and usually arise from expressions, such as
7714 the one described above, which make little sense to evaluate anyway.
7716 Each language defines to what degree it is strict about type. For
7717 instance, both Modula-2 and C require the arguments to arithmetical
7718 operators to be numbers. In C, enumerated types and pointers can be
7719 represented as numbers, so that they are valid arguments to mathematical
7720 operators. @xref{Support, ,Supported languages}, for further
7721 details on specific languages.
7723 @value{GDBN} provides some additional commands for controlling the type checker:
7725 @kindex set check@r{, type}
7726 @kindex set check type
7727 @kindex show check type
7729 @item set check type auto
7730 Set type checking on or off based on the current working language.
7731 @xref{Support, ,Supported languages}, for the default settings for
7734 @item set check type on
7735 @itemx set check type off
7736 Set type checking on or off, overriding the default setting for the
7737 current working language. Issue a warning if the setting does not
7738 match the language default. If any type mismatches occur in
7739 evaluating an expression while type checking is on, @value{GDBN} prints a
7740 message and aborts evaluation of the expression.
7742 @item set check type warn
7743 Cause the type checker to issue warnings, but to always attempt to
7744 evaluate the expression. Evaluating the expression may still
7745 be impossible for other reasons. For example, @value{GDBN} cannot add
7746 numbers and structures.
7749 Show the current setting of the type checker, and whether or not @value{GDBN}
7750 is setting it automatically.
7753 @cindex range checking
7754 @cindex checks, range
7755 @node Range Checking
7756 @subsection An overview of range checking
7758 In some languages (such as Modula-2), it is an error to exceed the
7759 bounds of a type; this is enforced with run-time checks. Such range
7760 checking is meant to ensure program correctness by making sure
7761 computations do not overflow, or indices on an array element access do
7762 not exceed the bounds of the array.
7764 For expressions you use in @value{GDBN} commands, you can tell
7765 @value{GDBN} to treat range errors in one of three ways: ignore them,
7766 always treat them as errors and abandon the expression, or issue
7767 warnings but evaluate the expression anyway.
7769 A range error can result from numerical overflow, from exceeding an
7770 array index bound, or when you type a constant that is not a member
7771 of any type. Some languages, however, do not treat overflows as an
7772 error. In many implementations of C, mathematical overflow causes the
7773 result to ``wrap around'' to lower values---for example, if @var{m} is
7774 the largest integer value, and @var{s} is the smallest, then
7777 @var{m} + 1 @result{} @var{s}
7780 This, too, is specific to individual languages, and in some cases
7781 specific to individual compilers or machines. @xref{Support, ,
7782 Supported languages}, for further details on specific languages.
7784 @value{GDBN} provides some additional commands for controlling the range checker:
7786 @kindex set check@r{, range}
7787 @kindex set check range
7788 @kindex show check range
7790 @item set check range auto
7791 Set range checking on or off based on the current working language.
7792 @xref{Support, ,Supported languages}, for the default settings for
7795 @item set check range on
7796 @itemx set check range off
7797 Set range checking on or off, overriding the default setting for the
7798 current working language. A warning is issued if the setting does not
7799 match the language default. If a range error occurs and range checking is on,
7800 then a message is printed and evaluation of the expression is aborted.
7802 @item set check range warn
7803 Output messages when the @value{GDBN} range checker detects a range error,
7804 but attempt to evaluate the expression anyway. Evaluating the
7805 expression may still be impossible for other reasons, such as accessing
7806 memory that the process does not own (a typical example from many Unix
7810 Show the current setting of the range checker, and whether or not it is
7811 being set automatically by @value{GDBN}.
7815 @section Supported languages
7817 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7818 @c This is false ...
7819 Some @value{GDBN} features may be used in expressions regardless of the
7820 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7821 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7822 ,Expressions}) can be used with the constructs of any supported
7825 The following sections detail to what degree each source language is
7826 supported by @value{GDBN}. These sections are not meant to be language
7827 tutorials or references, but serve only as a reference guide to what the
7828 @value{GDBN} expression parser accepts, and what input and output
7829 formats should look like for different languages. There are many good
7830 books written on each of these languages; please look to these for a
7831 language reference or tutorial.
7835 * Objective-C:: Objective-C
7836 * Modula-2:: Modula-2
7840 @subsection C and C@t{++}
7842 @cindex C and C@t{++}
7843 @cindex expressions in C or C@t{++}
7845 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7846 to both languages. Whenever this is the case, we discuss those languages
7850 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7851 @cindex @sc{gnu} C@t{++}
7852 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7853 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7854 effectively, you must compile your C@t{++} programs with a supported
7855 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7856 compiler (@code{aCC}).
7858 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7859 format; if it doesn't work on your system, try the stabs+ debugging
7860 format. You can select those formats explicitly with the @code{g++}
7861 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7862 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7863 CC, gcc.info, Using @sc{gnu} CC}.
7866 * C Operators:: C and C@t{++} operators
7867 * C Constants:: C and C@t{++} constants
7868 * C plus plus expressions:: C@t{++} expressions
7869 * C Defaults:: Default settings for C and C@t{++}
7870 * C Checks:: C and C@t{++} type and range checks
7871 * Debugging C:: @value{GDBN} and C
7872 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7876 @subsubsection C and C@t{++} operators
7878 @cindex C and C@t{++} operators
7880 Operators must be defined on values of specific types. For instance,
7881 @code{+} is defined on numbers, but not on structures. Operators are
7882 often defined on groups of types.
7884 For the purposes of C and C@t{++}, the following definitions hold:
7889 @emph{Integral types} include @code{int} with any of its storage-class
7890 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7893 @emph{Floating-point types} include @code{float}, @code{double}, and
7894 @code{long double} (if supported by the target platform).
7897 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7900 @emph{Scalar types} include all of the above.
7905 The following operators are supported. They are listed here
7906 in order of increasing precedence:
7910 The comma or sequencing operator. Expressions in a comma-separated list
7911 are evaluated from left to right, with the result of the entire
7912 expression being the last expression evaluated.
7915 Assignment. The value of an assignment expression is the value
7916 assigned. Defined on scalar types.
7919 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7920 and translated to @w{@code{@var{a} = @var{a op b}}}.
7921 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7922 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7923 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7926 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7927 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7931 Logical @sc{or}. Defined on integral types.
7934 Logical @sc{and}. Defined on integral types.
7937 Bitwise @sc{or}. Defined on integral types.
7940 Bitwise exclusive-@sc{or}. Defined on integral types.
7943 Bitwise @sc{and}. Defined on integral types.
7946 Equality and inequality. Defined on scalar types. The value of these
7947 expressions is 0 for false and non-zero for true.
7949 @item <@r{, }>@r{, }<=@r{, }>=
7950 Less than, greater than, less than or equal, greater than or equal.
7951 Defined on scalar types. The value of these expressions is 0 for false
7952 and non-zero for true.
7955 left shift, and right shift. Defined on integral types.
7958 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7961 Addition and subtraction. Defined on integral types, floating-point types and
7964 @item *@r{, }/@r{, }%
7965 Multiplication, division, and modulus. Multiplication and division are
7966 defined on integral and floating-point types. Modulus is defined on
7970 Increment and decrement. When appearing before a variable, the
7971 operation is performed before the variable is used in an expression;
7972 when appearing after it, the variable's value is used before the
7973 operation takes place.
7976 Pointer dereferencing. Defined on pointer types. Same precedence as
7980 Address operator. Defined on variables. Same precedence as @code{++}.
7982 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7983 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7984 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7985 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7989 Negative. Defined on integral and floating-point types. Same
7990 precedence as @code{++}.
7993 Logical negation. Defined on integral types. Same precedence as
7997 Bitwise complement operator. Defined on integral types. Same precedence as
8002 Structure member, and pointer-to-structure member. For convenience,
8003 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8004 pointer based on the stored type information.
8005 Defined on @code{struct} and @code{union} data.
8008 Dereferences of pointers to members.
8011 Array indexing. @code{@var{a}[@var{i}]} is defined as
8012 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8015 Function parameter list. Same precedence as @code{->}.
8018 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8019 and @code{class} types.
8022 Doubled colons also represent the @value{GDBN} scope operator
8023 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8027 If an operator is redefined in the user code, @value{GDBN} usually
8028 attempts to invoke the redefined version instead of using the operator's
8036 @subsubsection C and C@t{++} constants
8038 @cindex C and C@t{++} constants
8040 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8045 Integer constants are a sequence of digits. Octal constants are
8046 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8047 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8048 @samp{l}, specifying that the constant should be treated as a
8052 Floating point constants are a sequence of digits, followed by a decimal
8053 point, followed by a sequence of digits, and optionally followed by an
8054 exponent. An exponent is of the form:
8055 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8056 sequence of digits. The @samp{+} is optional for positive exponents.
8057 A floating-point constant may also end with a letter @samp{f} or
8058 @samp{F}, specifying that the constant should be treated as being of
8059 the @code{float} (as opposed to the default @code{double}) type; or with
8060 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8064 Enumerated constants consist of enumerated identifiers, or their
8065 integral equivalents.
8068 Character constants are a single character surrounded by single quotes
8069 (@code{'}), or a number---the ordinal value of the corresponding character
8070 (usually its @sc{ascii} value). Within quotes, the single character may
8071 be represented by a letter or by @dfn{escape sequences}, which are of
8072 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8073 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8074 @samp{@var{x}} is a predefined special character---for example,
8075 @samp{\n} for newline.
8078 String constants are a sequence of character constants surrounded by
8079 double quotes (@code{"}). Any valid character constant (as described
8080 above) may appear. Double quotes within the string must be preceded by
8081 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8085 Pointer constants are an integral value. You can also write pointers
8086 to constants using the C operator @samp{&}.
8089 Array constants are comma-separated lists surrounded by braces @samp{@{}
8090 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8091 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8092 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8096 * C plus plus expressions::
8103 @node C plus plus expressions
8104 @subsubsection C@t{++} expressions
8106 @cindex expressions in C@t{++}
8107 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8109 @cindex debugging C@t{++} programs
8110 @cindex C@t{++} compilers
8111 @cindex debug formats and C@t{++}
8112 @cindex @value{NGCC} and C@t{++}
8114 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8115 proper compiler and the proper debug format. Currently, @value{GDBN}
8116 works best when debugging C@t{++} code that is compiled with
8117 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8118 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8119 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8120 stabs+ as their default debug format, so you usually don't need to
8121 specify a debug format explicitly. Other compilers and/or debug formats
8122 are likely to work badly or not at all when using @value{GDBN} to debug
8128 @cindex member functions
8130 Member function calls are allowed; you can use expressions like
8133 count = aml->GetOriginal(x, y)
8136 @vindex this@r{, inside C@t{++} member functions}
8137 @cindex namespace in C@t{++}
8139 While a member function is active (in the selected stack frame), your
8140 expressions have the same namespace available as the member function;
8141 that is, @value{GDBN} allows implicit references to the class instance
8142 pointer @code{this} following the same rules as C@t{++}.
8144 @cindex call overloaded functions
8145 @cindex overloaded functions, calling
8146 @cindex type conversions in C@t{++}
8148 You can call overloaded functions; @value{GDBN} resolves the function
8149 call to the right definition, with some restrictions. @value{GDBN} does not
8150 perform overload resolution involving user-defined type conversions,
8151 calls to constructors, or instantiations of templates that do not exist
8152 in the program. It also cannot handle ellipsis argument lists or
8155 It does perform integral conversions and promotions, floating-point
8156 promotions, arithmetic conversions, pointer conversions, conversions of
8157 class objects to base classes, and standard conversions such as those of
8158 functions or arrays to pointers; it requires an exact match on the
8159 number of function arguments.
8161 Overload resolution is always performed, unless you have specified
8162 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8163 ,@value{GDBN} features for C@t{++}}.
8165 You must specify @code{set overload-resolution off} in order to use an
8166 explicit function signature to call an overloaded function, as in
8168 p 'foo(char,int)'('x', 13)
8171 The @value{GDBN} command-completion facility can simplify this;
8172 see @ref{Completion, ,Command completion}.
8174 @cindex reference declarations
8176 @value{GDBN} understands variables declared as C@t{++} references; you can use
8177 them in expressions just as you do in C@t{++} source---they are automatically
8180 In the parameter list shown when @value{GDBN} displays a frame, the values of
8181 reference variables are not displayed (unlike other variables); this
8182 avoids clutter, since references are often used for large structures.
8183 The @emph{address} of a reference variable is always shown, unless
8184 you have specified @samp{set print address off}.
8187 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8188 expressions can use it just as expressions in your program do. Since
8189 one scope may be defined in another, you can use @code{::} repeatedly if
8190 necessary, for example in an expression like
8191 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8192 resolving name scope by reference to source files, in both C and C@t{++}
8193 debugging (@pxref{Variables, ,Program variables}).
8196 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8197 calling virtual functions correctly, printing out virtual bases of
8198 objects, calling functions in a base subobject, casting objects, and
8199 invoking user-defined operators.
8202 @subsubsection C and C@t{++} defaults
8204 @cindex C and C@t{++} defaults
8206 If you allow @value{GDBN} to set type and range checking automatically, they
8207 both default to @code{off} whenever the working language changes to
8208 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8209 selects the working language.
8211 If you allow @value{GDBN} to set the language automatically, it
8212 recognizes source files whose names end with @file{.c}, @file{.C}, or
8213 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8214 these files, it sets the working language to C or C@t{++}.
8215 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8216 for further details.
8218 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8219 @c unimplemented. If (b) changes, it might make sense to let this node
8220 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8223 @subsubsection C and C@t{++} type and range checks
8225 @cindex C and C@t{++} checks
8227 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8228 is not used. However, if you turn type checking on, @value{GDBN}
8229 considers two variables type equivalent if:
8233 The two variables are structured and have the same structure, union, or
8237 The two variables have the same type name, or types that have been
8238 declared equivalent through @code{typedef}.
8241 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8244 The two @code{struct}, @code{union}, or @code{enum} variables are
8245 declared in the same declaration. (Note: this may not be true for all C
8250 Range checking, if turned on, is done on mathematical operations. Array
8251 indices are not checked, since they are often used to index a pointer
8252 that is not itself an array.
8255 @subsubsection @value{GDBN} and C
8257 The @code{set print union} and @code{show print union} commands apply to
8258 the @code{union} type. When set to @samp{on}, any @code{union} that is
8259 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8260 appears as @samp{@{...@}}.
8262 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8263 with pointers and a memory allocation function. @xref{Expressions,
8267 * Debugging C plus plus::
8270 @node Debugging C plus plus
8271 @subsubsection @value{GDBN} features for C@t{++}
8273 @cindex commands for C@t{++}
8275 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8276 designed specifically for use with C@t{++}. Here is a summary:
8279 @cindex break in overloaded functions
8280 @item @r{breakpoint menus}
8281 When you want a breakpoint in a function whose name is overloaded,
8282 @value{GDBN} breakpoint menus help you specify which function definition
8283 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8285 @cindex overloading in C@t{++}
8286 @item rbreak @var{regex}
8287 Setting breakpoints using regular expressions is helpful for setting
8288 breakpoints on overloaded functions that are not members of any special
8290 @xref{Set Breaks, ,Setting breakpoints}.
8292 @cindex C@t{++} exception handling
8295 Debug C@t{++} exception handling using these commands. @xref{Set
8296 Catchpoints, , Setting catchpoints}.
8299 @item ptype @var{typename}
8300 Print inheritance relationships as well as other information for type
8302 @xref{Symbols, ,Examining the Symbol Table}.
8304 @cindex C@t{++} symbol display
8305 @item set print demangle
8306 @itemx show print demangle
8307 @itemx set print asm-demangle
8308 @itemx show print asm-demangle
8309 Control whether C@t{++} symbols display in their source form, both when
8310 displaying code as C@t{++} source and when displaying disassemblies.
8311 @xref{Print Settings, ,Print settings}.
8313 @item set print object
8314 @itemx show print object
8315 Choose whether to print derived (actual) or declared types of objects.
8316 @xref{Print Settings, ,Print settings}.
8318 @item set print vtbl
8319 @itemx show print vtbl
8320 Control the format for printing virtual function tables.
8321 @xref{Print Settings, ,Print settings}.
8322 (The @code{vtbl} commands do not work on programs compiled with the HP
8323 ANSI C@t{++} compiler (@code{aCC}).)
8325 @kindex set overload-resolution
8326 @cindex overloaded functions, overload resolution
8327 @item set overload-resolution on
8328 Enable overload resolution for C@t{++} expression evaluation. The default
8329 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8330 and searches for a function whose signature matches the argument types,
8331 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8332 expressions}, for details). If it cannot find a match, it emits a
8335 @item set overload-resolution off
8336 Disable overload resolution for C@t{++} expression evaluation. For
8337 overloaded functions that are not class member functions, @value{GDBN}
8338 chooses the first function of the specified name that it finds in the
8339 symbol table, whether or not its arguments are of the correct type. For
8340 overloaded functions that are class member functions, @value{GDBN}
8341 searches for a function whose signature @emph{exactly} matches the
8344 @item @r{Overloaded symbol names}
8345 You can specify a particular definition of an overloaded symbol, using
8346 the same notation that is used to declare such symbols in C@t{++}: type
8347 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8348 also use the @value{GDBN} command-line word completion facilities to list the
8349 available choices, or to finish the type list for you.
8350 @xref{Completion,, Command completion}, for details on how to do this.
8354 @subsection Objective-C
8357 This section provides information about some commands and command
8358 options that are useful for debugging Objective-C code.
8361 * Method Names in Commands::
8362 * The Print Command with Objective-C::
8365 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8366 @subsubsection Method Names in Commands
8368 The following commands have been extended to accept Objective-C method
8369 names as line specifications:
8371 @kindex clear@r{, and Objective-C}
8372 @kindex break@r{, and Objective-C}
8373 @kindex info line@r{, and Objective-C}
8374 @kindex jump@r{, and Objective-C}
8375 @kindex list@r{, and Objective-C}
8379 @item @code{info line}
8384 A fully qualified Objective-C method name is specified as
8387 -[@var{Class} @var{methodName}]
8390 where the minus sign is used to indicate an instance method and a plus
8391 sign (not shown) is used to indicate a class method. The
8392 class name @var{Class} and method name @var{methoName} are enclosed in
8393 brackets, similar to the way messages are specified in Objective-C source
8394 code. For example, to set a breakpoint at the @code{create} instance method of
8395 class @code{Fruit} in the program currently being debugged, enter:
8398 break -[Fruit create]
8401 To list ten program lines around the @code{initialize} class method,
8405 list +[NSText initialize]
8408 In the current version of GDB, the plus or minus sign is required. In
8409 future versions of GDB, the plus or minus sign will be optional, but you
8410 can use it to narrow the search. It is also possible to specify just a
8417 You must specify the complete method name, including any colons. If
8418 your program's source files contain more than one @code{create} method,
8419 you'll be presented with a numbered list of classes that implement that
8420 method. Indicate your choice by number, or type @samp{0} to exit if
8423 As another example, to clear a breakpoint established at the
8424 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8427 clear -[NSWindow makeKeyAndOrderFront:]
8430 @node The Print Command with Objective-C
8431 @subsubsection The Print Command With Objective-C
8433 The print command has also been extended to accept methods. For example:
8436 print -[object hash]
8439 @cindex print an Objective-C object description
8440 will tell gdb to send the -hash message to object and print the
8441 result. Also an additional command has been added, @code{print-object}
8442 or @code{po} for short, which is meant to print the description of an
8443 object. However, this command may only work with certain Objective-C
8444 libraries that have a particular hook function, called
8445 @code{_NSPrintForDebugger} defined.
8447 @node Modula-2, , Objective-C, Support
8448 @subsection Modula-2
8450 @cindex Modula-2, @value{GDBN} support
8452 The extensions made to @value{GDBN} to support Modula-2 only support
8453 output from the @sc{gnu} Modula-2 compiler (which is currently being
8454 developed). Other Modula-2 compilers are not currently supported, and
8455 attempting to debug executables produced by them is most likely
8456 to give an error as @value{GDBN} reads in the executable's symbol
8459 @cindex expressions in Modula-2
8461 * M2 Operators:: Built-in operators
8462 * Built-In Func/Proc:: Built-in functions and procedures
8463 * M2 Constants:: Modula-2 constants
8464 * M2 Defaults:: Default settings for Modula-2
8465 * Deviations:: Deviations from standard Modula-2
8466 * M2 Checks:: Modula-2 type and range checks
8467 * M2 Scope:: The scope operators @code{::} and @code{.}
8468 * GDB/M2:: @value{GDBN} and Modula-2
8472 @subsubsection Operators
8473 @cindex Modula-2 operators
8475 Operators must be defined on values of specific types. For instance,
8476 @code{+} is defined on numbers, but not on structures. Operators are
8477 often defined on groups of types. For the purposes of Modula-2, the
8478 following definitions hold:
8483 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8487 @emph{Character types} consist of @code{CHAR} and its subranges.
8490 @emph{Floating-point types} consist of @code{REAL}.
8493 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8497 @emph{Scalar types} consist of all of the above.
8500 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8503 @emph{Boolean types} consist of @code{BOOLEAN}.
8507 The following operators are supported, and appear in order of
8508 increasing precedence:
8512 Function argument or array index separator.
8515 Assignment. The value of @var{var} @code{:=} @var{value} is
8519 Less than, greater than on integral, floating-point, or enumerated
8523 Less than or equal to, greater than or equal to
8524 on integral, floating-point and enumerated types, or set inclusion on
8525 set types. Same precedence as @code{<}.
8527 @item =@r{, }<>@r{, }#
8528 Equality and two ways of expressing inequality, valid on scalar types.
8529 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8530 available for inequality, since @code{#} conflicts with the script
8534 Set membership. Defined on set types and the types of their members.
8535 Same precedence as @code{<}.
8538 Boolean disjunction. Defined on boolean types.
8541 Boolean conjunction. Defined on boolean types.
8544 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8547 Addition and subtraction on integral and floating-point types, or union
8548 and difference on set types.
8551 Multiplication on integral and floating-point types, or set intersection
8555 Division on floating-point types, or symmetric set difference on set
8556 types. Same precedence as @code{*}.
8559 Integer division and remainder. Defined on integral types. Same
8560 precedence as @code{*}.
8563 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8566 Pointer dereferencing. Defined on pointer types.
8569 Boolean negation. Defined on boolean types. Same precedence as
8573 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8574 precedence as @code{^}.
8577 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8580 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8584 @value{GDBN} and Modula-2 scope operators.
8588 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8589 treats the use of the operator @code{IN}, or the use of operators
8590 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8591 @code{<=}, and @code{>=} on sets as an error.
8595 @node Built-In Func/Proc
8596 @subsubsection Built-in functions and procedures
8597 @cindex Modula-2 built-ins
8599 Modula-2 also makes available several built-in procedures and functions.
8600 In describing these, the following metavariables are used:
8605 represents an @code{ARRAY} variable.
8608 represents a @code{CHAR} constant or variable.
8611 represents a variable or constant of integral type.
8614 represents an identifier that belongs to a set. Generally used in the
8615 same function with the metavariable @var{s}. The type of @var{s} should
8616 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8619 represents a variable or constant of integral or floating-point type.
8622 represents a variable or constant of floating-point type.
8628 represents a variable.
8631 represents a variable or constant of one of many types. See the
8632 explanation of the function for details.
8635 All Modula-2 built-in procedures also return a result, described below.
8639 Returns the absolute value of @var{n}.
8642 If @var{c} is a lower case letter, it returns its upper case
8643 equivalent, otherwise it returns its argument.
8646 Returns the character whose ordinal value is @var{i}.
8649 Decrements the value in the variable @var{v} by one. Returns the new value.
8651 @item DEC(@var{v},@var{i})
8652 Decrements the value in the variable @var{v} by @var{i}. Returns the
8655 @item EXCL(@var{m},@var{s})
8656 Removes the element @var{m} from the set @var{s}. Returns the new
8659 @item FLOAT(@var{i})
8660 Returns the floating point equivalent of the integer @var{i}.
8663 Returns the index of the last member of @var{a}.
8666 Increments the value in the variable @var{v} by one. Returns the new value.
8668 @item INC(@var{v},@var{i})
8669 Increments the value in the variable @var{v} by @var{i}. Returns the
8672 @item INCL(@var{m},@var{s})
8673 Adds the element @var{m} to the set @var{s} if it is not already
8674 there. Returns the new set.
8677 Returns the maximum value of the type @var{t}.
8680 Returns the minimum value of the type @var{t}.
8683 Returns boolean TRUE if @var{i} is an odd number.
8686 Returns the ordinal value of its argument. For example, the ordinal
8687 value of a character is its @sc{ascii} value (on machines supporting the
8688 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8689 integral, character and enumerated types.
8692 Returns the size of its argument. @var{x} can be a variable or a type.
8694 @item TRUNC(@var{r})
8695 Returns the integral part of @var{r}.
8697 @item VAL(@var{t},@var{i})
8698 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8702 @emph{Warning:} Sets and their operations are not yet supported, so
8703 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8707 @cindex Modula-2 constants
8709 @subsubsection Constants
8711 @value{GDBN} allows you to express the constants of Modula-2 in the following
8717 Integer constants are simply a sequence of digits. When used in an
8718 expression, a constant is interpreted to be type-compatible with the
8719 rest of the expression. Hexadecimal integers are specified by a
8720 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8723 Floating point constants appear as a sequence of digits, followed by a
8724 decimal point and another sequence of digits. An optional exponent can
8725 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8726 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8727 digits of the floating point constant must be valid decimal (base 10)
8731 Character constants consist of a single character enclosed by a pair of
8732 like quotes, either single (@code{'}) or double (@code{"}). They may
8733 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8734 followed by a @samp{C}.
8737 String constants consist of a sequence of characters enclosed by a
8738 pair of like quotes, either single (@code{'}) or double (@code{"}).
8739 Escape sequences in the style of C are also allowed. @xref{C
8740 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8744 Enumerated constants consist of an enumerated identifier.
8747 Boolean constants consist of the identifiers @code{TRUE} and
8751 Pointer constants consist of integral values only.
8754 Set constants are not yet supported.
8758 @subsubsection Modula-2 defaults
8759 @cindex Modula-2 defaults
8761 If type and range checking are set automatically by @value{GDBN}, they
8762 both default to @code{on} whenever the working language changes to
8763 Modula-2. This happens regardless of whether you or @value{GDBN}
8764 selected the working language.
8766 If you allow @value{GDBN} to set the language automatically, then entering
8767 code compiled from a file whose name ends with @file{.mod} sets the
8768 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8769 the language automatically}, for further details.
8772 @subsubsection Deviations from standard Modula-2
8773 @cindex Modula-2, deviations from
8775 A few changes have been made to make Modula-2 programs easier to debug.
8776 This is done primarily via loosening its type strictness:
8780 Unlike in standard Modula-2, pointer constants can be formed by
8781 integers. This allows you to modify pointer variables during
8782 debugging. (In standard Modula-2, the actual address contained in a
8783 pointer variable is hidden from you; it can only be modified
8784 through direct assignment to another pointer variable or expression that
8785 returned a pointer.)
8788 C escape sequences can be used in strings and characters to represent
8789 non-printable characters. @value{GDBN} prints out strings with these
8790 escape sequences embedded. Single non-printable characters are
8791 printed using the @samp{CHR(@var{nnn})} format.
8794 The assignment operator (@code{:=}) returns the value of its right-hand
8798 All built-in procedures both modify @emph{and} return their argument.
8802 @subsubsection Modula-2 type and range checks
8803 @cindex Modula-2 checks
8806 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8809 @c FIXME remove warning when type/range checks added
8811 @value{GDBN} considers two Modula-2 variables type equivalent if:
8815 They are of types that have been declared equivalent via a @code{TYPE
8816 @var{t1} = @var{t2}} statement
8819 They have been declared on the same line. (Note: This is true of the
8820 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8823 As long as type checking is enabled, any attempt to combine variables
8824 whose types are not equivalent is an error.
8826 Range checking is done on all mathematical operations, assignment, array
8827 index bounds, and all built-in functions and procedures.
8830 @subsubsection The scope operators @code{::} and @code{.}
8832 @cindex @code{.}, Modula-2 scope operator
8833 @cindex colon, doubled as scope operator
8835 @vindex colon-colon@r{, in Modula-2}
8836 @c Info cannot handle :: but TeX can.
8839 @vindex ::@r{, in Modula-2}
8842 There are a few subtle differences between the Modula-2 scope operator
8843 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8848 @var{module} . @var{id}
8849 @var{scope} :: @var{id}
8853 where @var{scope} is the name of a module or a procedure,
8854 @var{module} the name of a module, and @var{id} is any declared
8855 identifier within your program, except another module.
8857 Using the @code{::} operator makes @value{GDBN} search the scope
8858 specified by @var{scope} for the identifier @var{id}. If it is not
8859 found in the specified scope, then @value{GDBN} searches all scopes
8860 enclosing the one specified by @var{scope}.
8862 Using the @code{.} operator makes @value{GDBN} search the current scope for
8863 the identifier specified by @var{id} that was imported from the
8864 definition module specified by @var{module}. With this operator, it is
8865 an error if the identifier @var{id} was not imported from definition
8866 module @var{module}, or if @var{id} is not an identifier in
8870 @subsubsection @value{GDBN} and Modula-2
8872 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8873 Five subcommands of @code{set print} and @code{show print} apply
8874 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8875 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8876 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8877 analogue in Modula-2.
8879 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8880 with any language, is not useful with Modula-2. Its
8881 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8882 created in Modula-2 as they can in C or C@t{++}. However, because an
8883 address can be specified by an integral constant, the construct
8884 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8886 @cindex @code{#} in Modula-2
8887 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8888 interpreted as the beginning of a comment. Use @code{<>} instead.
8890 @node Unsupported languages
8891 @section Unsupported languages
8893 @cindex unsupported languages
8894 @cindex minimal language
8895 In addition to the other fully-supported programming languages,
8896 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
8897 It does not represent a real programming language, but provides a set
8898 of capabilities close to what the C or assembly languages provide.
8899 This should allow most simple operations to be performed while debugging
8900 an application that uses a language currently not supported by @value{GDBN}.
8902 If the language is set to @code{auto}, @value{GDBN} will automatically
8903 select this language if the current frame corresponds to an unsupported
8907 @chapter Examining the Symbol Table
8909 The commands described in this chapter allow you to inquire about the
8910 symbols (names of variables, functions and types) defined in your
8911 program. This information is inherent in the text of your program and
8912 does not change as your program executes. @value{GDBN} finds it in your
8913 program's symbol table, in the file indicated when you started @value{GDBN}
8914 (@pxref{File Options, ,Choosing files}), or by one of the
8915 file-management commands (@pxref{Files, ,Commands to specify files}).
8917 @cindex symbol names
8918 @cindex names of symbols
8919 @cindex quoting names
8920 Occasionally, you may need to refer to symbols that contain unusual
8921 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8922 most frequent case is in referring to static variables in other
8923 source files (@pxref{Variables,,Program variables}). File names
8924 are recorded in object files as debugging symbols, but @value{GDBN} would
8925 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8926 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8927 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8934 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8937 @kindex info address
8938 @cindex address of a symbol
8939 @item info address @var{symbol}
8940 Describe where the data for @var{symbol} is stored. For a register
8941 variable, this says which register it is kept in. For a non-register
8942 local variable, this prints the stack-frame offset at which the variable
8945 Note the contrast with @samp{print &@var{symbol}}, which does not work
8946 at all for a register variable, and for a stack local variable prints
8947 the exact address of the current instantiation of the variable.
8950 @cindex symbol from address
8951 @item info symbol @var{addr}
8952 Print the name of a symbol which is stored at the address @var{addr}.
8953 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8954 nearest symbol and an offset from it:
8957 (@value{GDBP}) info symbol 0x54320
8958 _initialize_vx + 396 in section .text
8962 This is the opposite of the @code{info address} command. You can use
8963 it to find out the name of a variable or a function given its address.
8966 @item whatis @var{expr}
8967 Print the data type of expression @var{expr}. @var{expr} is not
8968 actually evaluated, and any side-effecting operations (such as
8969 assignments or function calls) inside it do not take place.
8970 @xref{Expressions, ,Expressions}.
8973 Print the data type of @code{$}, the last value in the value history.
8976 @item ptype @var{typename}
8977 Print a description of data type @var{typename}. @var{typename} may be
8978 the name of a type, or for C code it may have the form @samp{class
8979 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8980 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8982 @item ptype @var{expr}
8984 Print a description of the type of expression @var{expr}. @code{ptype}
8985 differs from @code{whatis} by printing a detailed description, instead
8986 of just the name of the type.
8988 For example, for this variable declaration:
8991 struct complex @{double real; double imag;@} v;
8995 the two commands give this output:
8999 (@value{GDBP}) whatis v
9000 type = struct complex
9001 (@value{GDBP}) ptype v
9002 type = struct complex @{
9010 As with @code{whatis}, using @code{ptype} without an argument refers to
9011 the type of @code{$}, the last value in the value history.
9014 @item info types @var{regexp}
9016 Print a brief description of all types whose names match @var{regexp}
9017 (or all types in your program, if you supply no argument). Each
9018 complete typename is matched as though it were a complete line; thus,
9019 @samp{i type value} gives information on all types in your program whose
9020 names include the string @code{value}, but @samp{i type ^value$} gives
9021 information only on types whose complete name is @code{value}.
9023 This command differs from @code{ptype} in two ways: first, like
9024 @code{whatis}, it does not print a detailed description; second, it
9025 lists all source files where a type is defined.
9028 @cindex local variables
9029 @item info scope @var{addr}
9030 List all the variables local to a particular scope. This command
9031 accepts a location---a function name, a source line, or an address
9032 preceded by a @samp{*}, and prints all the variables local to the
9033 scope defined by that location. For example:
9036 (@value{GDBP}) @b{info scope command_line_handler}
9037 Scope for command_line_handler:
9038 Symbol rl is an argument at stack/frame offset 8, length 4.
9039 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9040 Symbol linelength is in static storage at address 0x150a1c, length 4.
9041 Symbol p is a local variable in register $esi, length 4.
9042 Symbol p1 is a local variable in register $ebx, length 4.
9043 Symbol nline is a local variable in register $edx, length 4.
9044 Symbol repeat is a local variable at frame offset -8, length 4.
9048 This command is especially useful for determining what data to collect
9049 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9054 Show information about the current source file---that is, the source file for
9055 the function containing the current point of execution:
9058 the name of the source file, and the directory containing it,
9060 the directory it was compiled in,
9062 its length, in lines,
9064 which programming language it is written in,
9066 whether the executable includes debugging information for that file, and
9067 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9069 whether the debugging information includes information about
9070 preprocessor macros.
9074 @kindex info sources
9076 Print the names of all source files in your program for which there is
9077 debugging information, organized into two lists: files whose symbols
9078 have already been read, and files whose symbols will be read when needed.
9080 @kindex info functions
9081 @item info functions
9082 Print the names and data types of all defined functions.
9084 @item info functions @var{regexp}
9085 Print the names and data types of all defined functions
9086 whose names contain a match for regular expression @var{regexp}.
9087 Thus, @samp{info fun step} finds all functions whose names
9088 include @code{step}; @samp{info fun ^step} finds those whose names
9089 start with @code{step}. If a function name contains characters
9090 that conflict with the regular expression language (eg.
9091 @samp{operator*()}), they may be quoted with a backslash.
9093 @kindex info variables
9094 @item info variables
9095 Print the names and data types of all variables that are declared
9096 outside of functions (i.e.@: excluding local variables).
9098 @item info variables @var{regexp}
9099 Print the names and data types of all variables (except for local
9100 variables) whose names contain a match for regular expression
9103 @kindex info classes
9105 @itemx info classes @var{regexp}
9106 Display all Objective-C classes in your program, or
9107 (with the @var{regexp} argument) all those matching a particular regular
9110 @kindex info selectors
9111 @item info selectors
9112 @itemx info selectors @var{regexp}
9113 Display all Objective-C selectors in your program, or
9114 (with the @var{regexp} argument) all those matching a particular regular
9118 This was never implemented.
9119 @kindex info methods
9121 @itemx info methods @var{regexp}
9122 The @code{info methods} command permits the user to examine all defined
9123 methods within C@t{++} program, or (with the @var{regexp} argument) a
9124 specific set of methods found in the various C@t{++} classes. Many
9125 C@t{++} classes provide a large number of methods. Thus, the output
9126 from the @code{ptype} command can be overwhelming and hard to use. The
9127 @code{info-methods} command filters the methods, printing only those
9128 which match the regular-expression @var{regexp}.
9131 @cindex reloading symbols
9132 Some systems allow individual object files that make up your program to
9133 be replaced without stopping and restarting your program. For example,
9134 in VxWorks you can simply recompile a defective object file and keep on
9135 running. If you are running on one of these systems, you can allow
9136 @value{GDBN} to reload the symbols for automatically relinked modules:
9139 @kindex set symbol-reloading
9140 @item set symbol-reloading on
9141 Replace symbol definitions for the corresponding source file when an
9142 object file with a particular name is seen again.
9144 @item set symbol-reloading off
9145 Do not replace symbol definitions when encountering object files of the
9146 same name more than once. This is the default state; if you are not
9147 running on a system that permits automatic relinking of modules, you
9148 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9149 may discard symbols when linking large programs, that may contain
9150 several modules (from different directories or libraries) with the same
9153 @kindex show symbol-reloading
9154 @item show symbol-reloading
9155 Show the current @code{on} or @code{off} setting.
9158 @kindex set opaque-type-resolution
9159 @item set opaque-type-resolution on
9160 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9161 declared as a pointer to a @code{struct}, @code{class}, or
9162 @code{union}---for example, @code{struct MyType *}---that is used in one
9163 source file although the full declaration of @code{struct MyType} is in
9164 another source file. The default is on.
9166 A change in the setting of this subcommand will not take effect until
9167 the next time symbols for a file are loaded.
9169 @item set opaque-type-resolution off
9170 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9171 is printed as follows:
9173 @{<no data fields>@}
9176 @kindex show opaque-type-resolution
9177 @item show opaque-type-resolution
9178 Show whether opaque types are resolved or not.
9180 @kindex maint print symbols
9182 @kindex maint print psymbols
9183 @cindex partial symbol dump
9184 @item maint print symbols @var{filename}
9185 @itemx maint print psymbols @var{filename}
9186 @itemx maint print msymbols @var{filename}
9187 Write a dump of debugging symbol data into the file @var{filename}.
9188 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9189 symbols with debugging data are included. If you use @samp{maint print
9190 symbols}, @value{GDBN} includes all the symbols for which it has already
9191 collected full details: that is, @var{filename} reflects symbols for
9192 only those files whose symbols @value{GDBN} has read. You can use the
9193 command @code{info sources} to find out which files these are. If you
9194 use @samp{maint print psymbols} instead, the dump shows information about
9195 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9196 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9197 @samp{maint print msymbols} dumps just the minimal symbol information
9198 required for each object file from which @value{GDBN} has read some symbols.
9199 @xref{Files, ,Commands to specify files}, for a discussion of how
9200 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9202 @kindex maint info symtabs
9203 @kindex maint info psymtabs
9204 @cindex listing @value{GDBN}'s internal symbol tables
9205 @cindex symbol tables, listing @value{GDBN}'s internal
9206 @cindex full symbol tables, listing @value{GDBN}'s internal
9207 @cindex partial symbol tables, listing @value{GDBN}'s internal
9208 @item maint info symtabs @r{[} @var{regexp} @r{]}
9209 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9211 List the @code{struct symtab} or @code{struct partial_symtab}
9212 structures whose names match @var{regexp}. If @var{regexp} is not
9213 given, list them all. The output includes expressions which you can
9214 copy into a @value{GDBN} debugging this one to examine a particular
9215 structure in more detail. For example:
9218 (@value{GDBP}) maint info psymtabs dwarf2read
9219 @{ objfile /home/gnu/build/gdb/gdb
9220 ((struct objfile *) 0x82e69d0)
9221 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9222 ((struct partial_symtab *) 0x8474b10)
9225 text addresses 0x814d3c8 -- 0x8158074
9226 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9227 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9231 (@value{GDBP}) maint info symtabs
9235 We see that there is one partial symbol table whose filename contains
9236 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9237 and we see that @value{GDBN} has not read in any symtabs yet at all.
9238 If we set a breakpoint on a function, that will cause @value{GDBN} to
9239 read the symtab for the compilation unit containing that function:
9242 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9243 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9245 (@value{GDBP}) maint info symtabs
9246 @{ objfile /home/gnu/build/gdb/gdb
9247 ((struct objfile *) 0x82e69d0)
9248 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9249 ((struct symtab *) 0x86c1f38)
9252 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9262 @chapter Altering Execution
9264 Once you think you have found an error in your program, you might want to
9265 find out for certain whether correcting the apparent error would lead to
9266 correct results in the rest of the run. You can find the answer by
9267 experiment, using the @value{GDBN} features for altering execution of the
9270 For example, you can store new values into variables or memory
9271 locations, give your program a signal, restart it at a different
9272 address, or even return prematurely from a function.
9275 * Assignment:: Assignment to variables
9276 * Jumping:: Continuing at a different address
9277 * Signaling:: Giving your program a signal
9278 * Returning:: Returning from a function
9279 * Calling:: Calling your program's functions
9280 * Patching:: Patching your program
9284 @section Assignment to variables
9287 @cindex setting variables
9288 To alter the value of a variable, evaluate an assignment expression.
9289 @xref{Expressions, ,Expressions}. For example,
9296 stores the value 4 into the variable @code{x}, and then prints the
9297 value of the assignment expression (which is 4).
9298 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9299 information on operators in supported languages.
9301 @kindex set variable
9302 @cindex variables, setting
9303 If you are not interested in seeing the value of the assignment, use the
9304 @code{set} command instead of the @code{print} command. @code{set} is
9305 really the same as @code{print} except that the expression's value is
9306 not printed and is not put in the value history (@pxref{Value History,
9307 ,Value history}). The expression is evaluated only for its effects.
9309 If the beginning of the argument string of the @code{set} command
9310 appears identical to a @code{set} subcommand, use the @code{set
9311 variable} command instead of just @code{set}. This command is identical
9312 to @code{set} except for its lack of subcommands. For example, if your
9313 program has a variable @code{width}, you get an error if you try to set
9314 a new value with just @samp{set width=13}, because @value{GDBN} has the
9315 command @code{set width}:
9318 (@value{GDBP}) whatis width
9320 (@value{GDBP}) p width
9322 (@value{GDBP}) set width=47
9323 Invalid syntax in expression.
9327 The invalid expression, of course, is @samp{=47}. In
9328 order to actually set the program's variable @code{width}, use
9331 (@value{GDBP}) set var width=47
9334 Because the @code{set} command has many subcommands that can conflict
9335 with the names of program variables, it is a good idea to use the
9336 @code{set variable} command instead of just @code{set}. For example, if
9337 your program has a variable @code{g}, you run into problems if you try
9338 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9339 the command @code{set gnutarget}, abbreviated @code{set g}:
9343 (@value{GDBP}) whatis g
9347 (@value{GDBP}) set g=4
9351 The program being debugged has been started already.
9352 Start it from the beginning? (y or n) y
9353 Starting program: /home/smith/cc_progs/a.out
9354 "/home/smith/cc_progs/a.out": can't open to read symbols:
9356 (@value{GDBP}) show g
9357 The current BFD target is "=4".
9362 The program variable @code{g} did not change, and you silently set the
9363 @code{gnutarget} to an invalid value. In order to set the variable
9367 (@value{GDBP}) set var g=4
9370 @value{GDBN} allows more implicit conversions in assignments than C; you can
9371 freely store an integer value into a pointer variable or vice versa,
9372 and you can convert any structure to any other structure that is the
9373 same length or shorter.
9374 @comment FIXME: how do structs align/pad in these conversions?
9375 @comment /doc@cygnus.com 18dec1990
9377 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9378 construct to generate a value of specified type at a specified address
9379 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9380 to memory location @code{0x83040} as an integer (which implies a certain size
9381 and representation in memory), and
9384 set @{int@}0x83040 = 4
9388 stores the value 4 into that memory location.
9391 @section Continuing at a different address
9393 Ordinarily, when you continue your program, you do so at the place where
9394 it stopped, with the @code{continue} command. You can instead continue at
9395 an address of your own choosing, with the following commands:
9399 @item jump @var{linespec}
9400 Resume execution at line @var{linespec}. Execution stops again
9401 immediately if there is a breakpoint there. @xref{List, ,Printing
9402 source lines}, for a description of the different forms of
9403 @var{linespec}. It is common practice to use the @code{tbreak} command
9404 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9407 The @code{jump} command does not change the current stack frame, or
9408 the stack pointer, or the contents of any memory location or any
9409 register other than the program counter. If line @var{linespec} is in
9410 a different function from the one currently executing, the results may
9411 be bizarre if the two functions expect different patterns of arguments or
9412 of local variables. For this reason, the @code{jump} command requests
9413 confirmation if the specified line is not in the function currently
9414 executing. However, even bizarre results are predictable if you are
9415 well acquainted with the machine-language code of your program.
9417 @item jump *@var{address}
9418 Resume execution at the instruction at address @var{address}.
9421 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9422 On many systems, you can get much the same effect as the @code{jump}
9423 command by storing a new value into the register @code{$pc}. The
9424 difference is that this does not start your program running; it only
9425 changes the address of where it @emph{will} run when you continue. For
9433 makes the next @code{continue} command or stepping command execute at
9434 address @code{0x485}, rather than at the address where your program stopped.
9435 @xref{Continuing and Stepping, ,Continuing and stepping}.
9437 The most common occasion to use the @code{jump} command is to back
9438 up---perhaps with more breakpoints set---over a portion of a program
9439 that has already executed, in order to examine its execution in more
9444 @section Giving your program a signal
9448 @item signal @var{signal}
9449 Resume execution where your program stopped, but immediately give it the
9450 signal @var{signal}. @var{signal} can be the name or the number of a
9451 signal. For example, on many systems @code{signal 2} and @code{signal
9452 SIGINT} are both ways of sending an interrupt signal.
9454 Alternatively, if @var{signal} is zero, continue execution without
9455 giving a signal. This is useful when your program stopped on account of
9456 a signal and would ordinary see the signal when resumed with the
9457 @code{continue} command; @samp{signal 0} causes it to resume without a
9460 @code{signal} does not repeat when you press @key{RET} a second time
9461 after executing the command.
9465 Invoking the @code{signal} command is not the same as invoking the
9466 @code{kill} utility from the shell. Sending a signal with @code{kill}
9467 causes @value{GDBN} to decide what to do with the signal depending on
9468 the signal handling tables (@pxref{Signals}). The @code{signal} command
9469 passes the signal directly to your program.
9473 @section Returning from a function
9476 @cindex returning from a function
9479 @itemx return @var{expression}
9480 You can cancel execution of a function call with the @code{return}
9481 command. If you give an
9482 @var{expression} argument, its value is used as the function's return
9486 When you use @code{return}, @value{GDBN} discards the selected stack frame
9487 (and all frames within it). You can think of this as making the
9488 discarded frame return prematurely. If you wish to specify a value to
9489 be returned, give that value as the argument to @code{return}.
9491 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9492 frame}), and any other frames inside of it, leaving its caller as the
9493 innermost remaining frame. That frame becomes selected. The
9494 specified value is stored in the registers used for returning values
9497 The @code{return} command does not resume execution; it leaves the
9498 program stopped in the state that would exist if the function had just
9499 returned. In contrast, the @code{finish} command (@pxref{Continuing
9500 and Stepping, ,Continuing and stepping}) resumes execution until the
9501 selected stack frame returns naturally.
9504 @section Calling program functions
9506 @cindex calling functions
9509 @item call @var{expr}
9510 Evaluate the expression @var{expr} without displaying @code{void}
9514 You can use this variant of the @code{print} command if you want to
9515 execute a function from your program, but without cluttering the output
9516 with @code{void} returned values. If the result is not void, it
9517 is printed and saved in the value history.
9520 @section Patching programs
9522 @cindex patching binaries
9523 @cindex writing into executables
9524 @cindex writing into corefiles
9526 By default, @value{GDBN} opens the file containing your program's
9527 executable code (or the corefile) read-only. This prevents accidental
9528 alterations to machine code; but it also prevents you from intentionally
9529 patching your program's binary.
9531 If you'd like to be able to patch the binary, you can specify that
9532 explicitly with the @code{set write} command. For example, you might
9533 want to turn on internal debugging flags, or even to make emergency
9539 @itemx set write off
9540 If you specify @samp{set write on}, @value{GDBN} opens executable and
9541 core files for both reading and writing; if you specify @samp{set write
9542 off} (the default), @value{GDBN} opens them read-only.
9544 If you have already loaded a file, you must load it again (using the
9545 @code{exec-file} or @code{core-file} command) after changing @code{set
9546 write}, for your new setting to take effect.
9550 Display whether executable files and core files are opened for writing
9555 @chapter @value{GDBN} Files
9557 @value{GDBN} needs to know the file name of the program to be debugged,
9558 both in order to read its symbol table and in order to start your
9559 program. To debug a core dump of a previous run, you must also tell
9560 @value{GDBN} the name of the core dump file.
9563 * Files:: Commands to specify files
9564 * Separate Debug Files:: Debugging information in separate files
9565 * Symbol Errors:: Errors reading symbol files
9569 @section Commands to specify files
9571 @cindex symbol table
9572 @cindex core dump file
9574 You may want to specify executable and core dump file names. The usual
9575 way to do this is at start-up time, using the arguments to
9576 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9577 Out of @value{GDBN}}).
9579 Occasionally it is necessary to change to a different file during a
9580 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9581 a file you want to use. In these situations the @value{GDBN} commands
9582 to specify new files are useful.
9585 @cindex executable file
9587 @item file @var{filename}
9588 Use @var{filename} as the program to be debugged. It is read for its
9589 symbols and for the contents of pure memory. It is also the program
9590 executed when you use the @code{run} command. If you do not specify a
9591 directory and the file is not found in the @value{GDBN} working directory,
9592 @value{GDBN} uses the environment variable @code{PATH} as a list of
9593 directories to search, just as the shell does when looking for a program
9594 to run. You can change the value of this variable, for both @value{GDBN}
9595 and your program, using the @code{path} command.
9597 On systems with memory-mapped files, an auxiliary file named
9598 @file{@var{filename}.syms} may hold symbol table information for
9599 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9600 @file{@var{filename}.syms}, starting up more quickly. See the
9601 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9602 (available on the command line, and with the commands @code{file},
9603 @code{symbol-file}, or @code{add-symbol-file}, described below),
9604 for more information.
9607 @code{file} with no argument makes @value{GDBN} discard any information it
9608 has on both executable file and the symbol table.
9611 @item exec-file @r{[} @var{filename} @r{]}
9612 Specify that the program to be run (but not the symbol table) is found
9613 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9614 if necessary to locate your program. Omitting @var{filename} means to
9615 discard information on the executable file.
9618 @item symbol-file @r{[} @var{filename} @r{]}
9619 Read symbol table information from file @var{filename}. @code{PATH} is
9620 searched when necessary. Use the @code{file} command to get both symbol
9621 table and program to run from the same file.
9623 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9624 program's symbol table.
9626 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9627 of its convenience variables, the value history, and all breakpoints and
9628 auto-display expressions. This is because they may contain pointers to
9629 the internal data recording symbols and data types, which are part of
9630 the old symbol table data being discarded inside @value{GDBN}.
9632 @code{symbol-file} does not repeat if you press @key{RET} again after
9635 When @value{GDBN} is configured for a particular environment, it
9636 understands debugging information in whatever format is the standard
9637 generated for that environment; you may use either a @sc{gnu} compiler, or
9638 other compilers that adhere to the local conventions.
9639 Best results are usually obtained from @sc{gnu} compilers; for example,
9640 using @code{@value{GCC}} you can generate debugging information for
9643 For most kinds of object files, with the exception of old SVR3 systems
9644 using COFF, the @code{symbol-file} command does not normally read the
9645 symbol table in full right away. Instead, it scans the symbol table
9646 quickly to find which source files and which symbols are present. The
9647 details are read later, one source file at a time, as they are needed.
9649 The purpose of this two-stage reading strategy is to make @value{GDBN}
9650 start up faster. For the most part, it is invisible except for
9651 occasional pauses while the symbol table details for a particular source
9652 file are being read. (The @code{set verbose} command can turn these
9653 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9654 warnings and messages}.)
9656 We have not implemented the two-stage strategy for COFF yet. When the
9657 symbol table is stored in COFF format, @code{symbol-file} reads the
9658 symbol table data in full right away. Note that ``stabs-in-COFF''
9659 still does the two-stage strategy, since the debug info is actually
9663 @cindex reading symbols immediately
9664 @cindex symbols, reading immediately
9666 @cindex memory-mapped symbol file
9667 @cindex saving symbol table
9668 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9669 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9670 You can override the @value{GDBN} two-stage strategy for reading symbol
9671 tables by using the @samp{-readnow} option with any of the commands that
9672 load symbol table information, if you want to be sure @value{GDBN} has the
9673 entire symbol table available.
9675 If memory-mapped files are available on your system through the
9676 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9677 cause @value{GDBN} to write the symbols for your program into a reusable
9678 file. Future @value{GDBN} debugging sessions map in symbol information
9679 from this auxiliary symbol file (if the program has not changed), rather
9680 than spending time reading the symbol table from the executable
9681 program. Using the @samp{-mapped} option has the same effect as
9682 starting @value{GDBN} with the @samp{-mapped} command-line option.
9684 You can use both options together, to make sure the auxiliary symbol
9685 file has all the symbol information for your program.
9687 The auxiliary symbol file for a program called @var{myprog} is called
9688 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9689 than the corresponding executable), @value{GDBN} always attempts to use
9690 it when you debug @var{myprog}; no special options or commands are
9693 The @file{.syms} file is specific to the host machine where you run
9694 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9695 symbol table. It cannot be shared across multiple host platforms.
9697 @c FIXME: for now no mention of directories, since this seems to be in
9698 @c flux. 13mar1992 status is that in theory GDB would look either in
9699 @c current dir or in same dir as myprog; but issues like competing
9700 @c GDB's, or clutter in system dirs, mean that in practice right now
9701 @c only current dir is used. FFish says maybe a special GDB hierarchy
9702 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9707 @item core-file @r{[} @var{filename} @r{]}
9708 Specify the whereabouts of a core dump file to be used as the ``contents
9709 of memory''. Traditionally, core files contain only some parts of the
9710 address space of the process that generated them; @value{GDBN} can access the
9711 executable file itself for other parts.
9713 @code{core-file} with no argument specifies that no core file is
9716 Note that the core file is ignored when your program is actually running
9717 under @value{GDBN}. So, if you have been running your program and you
9718 wish to debug a core file instead, you must kill the subprocess in which
9719 the program is running. To do this, use the @code{kill} command
9720 (@pxref{Kill Process, ,Killing the child process}).
9722 @kindex add-symbol-file
9723 @cindex dynamic linking
9724 @item add-symbol-file @var{filename} @var{address}
9725 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9726 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9727 The @code{add-symbol-file} command reads additional symbol table
9728 information from the file @var{filename}. You would use this command
9729 when @var{filename} has been dynamically loaded (by some other means)
9730 into the program that is running. @var{address} should be the memory
9731 address at which the file has been loaded; @value{GDBN} cannot figure
9732 this out for itself. You can additionally specify an arbitrary number
9733 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9734 section name and base address for that section. You can specify any
9735 @var{address} as an expression.
9737 The symbol table of the file @var{filename} is added to the symbol table
9738 originally read with the @code{symbol-file} command. You can use the
9739 @code{add-symbol-file} command any number of times; the new symbol data
9740 thus read keeps adding to the old. To discard all old symbol data
9741 instead, use the @code{symbol-file} command without any arguments.
9743 @cindex relocatable object files, reading symbols from
9744 @cindex object files, relocatable, reading symbols from
9745 @cindex reading symbols from relocatable object files
9746 @cindex symbols, reading from relocatable object files
9747 @cindex @file{.o} files, reading symbols from
9748 Although @var{filename} is typically a shared library file, an
9749 executable file, or some other object file which has been fully
9750 relocated for loading into a process, you can also load symbolic
9751 information from relocatable @file{.o} files, as long as:
9755 the file's symbolic information refers only to linker symbols defined in
9756 that file, not to symbols defined by other object files,
9758 every section the file's symbolic information refers to has actually
9759 been loaded into the inferior, as it appears in the file, and
9761 you can determine the address at which every section was loaded, and
9762 provide these to the @code{add-symbol-file} command.
9766 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9767 relocatable files into an already running program; such systems
9768 typically make the requirements above easy to meet. However, it's
9769 important to recognize that many native systems use complex link
9770 procedures (@code{.linkonce} section factoring and C++ constructor table
9771 assembly, for example) that make the requirements difficult to meet. In
9772 general, one cannot assume that using @code{add-symbol-file} to read a
9773 relocatable object file's symbolic information will have the same effect
9774 as linking the relocatable object file into the program in the normal
9777 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9779 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9780 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9781 table information for @var{filename}.
9783 @kindex add-shared-symbol-file
9784 @item add-shared-symbol-file
9785 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9786 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9787 shared libraries, however if @value{GDBN} does not find yours, you can run
9788 @code{add-shared-symbol-file}. It takes no arguments.
9792 The @code{section} command changes the base address of section SECTION of
9793 the exec file to ADDR. This can be used if the exec file does not contain
9794 section addresses, (such as in the a.out format), or when the addresses
9795 specified in the file itself are wrong. Each section must be changed
9796 separately. The @code{info files} command, described below, lists all
9797 the sections and their addresses.
9803 @code{info files} and @code{info target} are synonymous; both print the
9804 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9805 including the names of the executable and core dump files currently in
9806 use by @value{GDBN}, and the files from which symbols were loaded. The
9807 command @code{help target} lists all possible targets rather than
9810 @kindex maint info sections
9811 @item maint info sections
9812 Another command that can give you extra information about program sections
9813 is @code{maint info sections}. In addition to the section information
9814 displayed by @code{info files}, this command displays the flags and file
9815 offset of each section in the executable and core dump files. In addition,
9816 @code{maint info sections} provides the following command options (which
9817 may be arbitrarily combined):
9821 Display sections for all loaded object files, including shared libraries.
9822 @item @var{sections}
9823 Display info only for named @var{sections}.
9824 @item @var{section-flags}
9825 Display info only for sections for which @var{section-flags} are true.
9826 The section flags that @value{GDBN} currently knows about are:
9829 Section will have space allocated in the process when loaded.
9830 Set for all sections except those containing debug information.
9832 Section will be loaded from the file into the child process memory.
9833 Set for pre-initialized code and data, clear for @code{.bss} sections.
9835 Section needs to be relocated before loading.
9837 Section cannot be modified by the child process.
9839 Section contains executable code only.
9841 Section contains data only (no executable code).
9843 Section will reside in ROM.
9845 Section contains data for constructor/destructor lists.
9847 Section is not empty.
9849 An instruction to the linker to not output the section.
9850 @item COFF_SHARED_LIBRARY
9851 A notification to the linker that the section contains
9852 COFF shared library information.
9854 Section contains common symbols.
9857 @kindex set trust-readonly-sections
9858 @item set trust-readonly-sections on
9859 Tell @value{GDBN} that readonly sections in your object file
9860 really are read-only (i.e.@: that their contents will not change).
9861 In that case, @value{GDBN} can fetch values from these sections
9862 out of the object file, rather than from the target program.
9863 For some targets (notably embedded ones), this can be a significant
9864 enhancement to debugging performance.
9868 @item set trust-readonly-sections off
9869 Tell @value{GDBN} not to trust readonly sections. This means that
9870 the contents of the section might change while the program is running,
9871 and must therefore be fetched from the target when needed.
9874 All file-specifying commands allow both absolute and relative file names
9875 as arguments. @value{GDBN} always converts the file name to an absolute file
9876 name and remembers it that way.
9878 @cindex shared libraries
9879 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9882 @value{GDBN} automatically loads symbol definitions from shared libraries
9883 when you use the @code{run} command, or when you examine a core file.
9884 (Before you issue the @code{run} command, @value{GDBN} does not understand
9885 references to a function in a shared library, however---unless you are
9886 debugging a core file).
9888 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9889 automatically loads the symbols at the time of the @code{shl_load} call.
9891 @c FIXME: some @value{GDBN} release may permit some refs to undef
9892 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9893 @c FIXME...lib; check this from time to time when updating manual
9895 There are times, however, when you may wish to not automatically load
9896 symbol definitions from shared libraries, such as when they are
9897 particularly large or there are many of them.
9899 To control the automatic loading of shared library symbols, use the
9903 @kindex set auto-solib-add
9904 @item set auto-solib-add @var{mode}
9905 If @var{mode} is @code{on}, symbols from all shared object libraries
9906 will be loaded automatically when the inferior begins execution, you
9907 attach to an independently started inferior, or when the dynamic linker
9908 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9909 is @code{off}, symbols must be loaded manually, using the
9910 @code{sharedlibrary} command. The default value is @code{on}.
9912 @kindex show auto-solib-add
9913 @item show auto-solib-add
9914 Display the current autoloading mode.
9917 To explicitly load shared library symbols, use the @code{sharedlibrary}
9921 @kindex info sharedlibrary
9924 @itemx info sharedlibrary
9925 Print the names of the shared libraries which are currently loaded.
9927 @kindex sharedlibrary
9929 @item sharedlibrary @var{regex}
9930 @itemx share @var{regex}
9931 Load shared object library symbols for files matching a
9932 Unix regular expression.
9933 As with files loaded automatically, it only loads shared libraries
9934 required by your program for a core file or after typing @code{run}. If
9935 @var{regex} is omitted all shared libraries required by your program are
9939 On some systems, such as HP-UX systems, @value{GDBN} supports
9940 autoloading shared library symbols until a limiting threshold size is
9941 reached. This provides the benefit of allowing autoloading to remain on
9942 by default, but avoids autoloading excessively large shared libraries,
9943 up to a threshold that is initially set, but which you can modify if you
9946 Beyond that threshold, symbols from shared libraries must be explicitly
9947 loaded. To load these symbols, use the command @code{sharedlibrary
9948 @var{filename}}. The base address of the shared library is determined
9949 automatically by @value{GDBN} and need not be specified.
9951 To display or set the threshold, use the commands:
9954 @kindex set auto-solib-limit
9955 @item set auto-solib-limit @var{threshold}
9956 Set the autoloading size threshold, in an integral number of megabytes.
9957 If @var{threshold} is nonzero and shared library autoloading is enabled,
9958 symbols from all shared object libraries will be loaded until the total
9959 size of the loaded shared library symbols exceeds this threshold.
9960 Otherwise, symbols must be loaded manually, using the
9961 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9964 @kindex show auto-solib-limit
9965 @item show auto-solib-limit
9966 Display the current autoloading size threshold, in megabytes.
9969 Shared libraries are also supported in many cross or remote debugging
9970 configurations. A copy of the target's libraries need to be present on the
9971 host system; they need to be the same as the target libraries, although the
9972 copies on the target can be stripped as long as the copies on the host are
9975 You need to tell @value{GDBN} where the target libraries are, so that it can
9976 load the correct copies---otherwise, it may try to load the host's libraries.
9977 @value{GDBN} has two variables to specify the search directories for target
9981 @kindex set solib-absolute-prefix
9982 @item set solib-absolute-prefix @var{path}
9983 If this variable is set, @var{path} will be used as a prefix for any
9984 absolute shared library paths; many runtime loaders store the absolute
9985 paths to the shared library in the target program's memory. If you use
9986 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9987 out in the same way that they are on the target, with e.g.@: a
9988 @file{/usr/lib} hierarchy under @var{path}.
9990 You can set the default value of @samp{solib-absolute-prefix} by using the
9991 configure-time @samp{--with-sysroot} option.
9993 @kindex show solib-absolute-prefix
9994 @item show solib-absolute-prefix
9995 Display the current shared library prefix.
9997 @kindex set solib-search-path
9998 @item set solib-search-path @var{path}
9999 If this variable is set, @var{path} is a colon-separated list of directories
10000 to search for shared libraries. @samp{solib-search-path} is used after
10001 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10002 the library is relative instead of absolute. If you want to use
10003 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10004 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10005 @value{GDBN} from finding your host's libraries.
10007 @kindex show solib-search-path
10008 @item show solib-search-path
10009 Display the current shared library search path.
10013 @node Separate Debug Files
10014 @section Debugging Information in Separate Files
10015 @cindex separate debugging information files
10016 @cindex debugging information in separate files
10017 @cindex @file{.debug} subdirectories
10018 @cindex debugging information directory, global
10019 @cindex global debugging information directory
10021 @value{GDBN} allows you to put a program's debugging information in a
10022 file separate from the executable itself, in a way that allows
10023 @value{GDBN} to find and load the debugging information automatically.
10024 Since debugging information can be very large --- sometimes larger
10025 than the executable code itself --- some systems distribute debugging
10026 information for their executables in separate files, which users can
10027 install only when they need to debug a problem.
10029 If an executable's debugging information has been extracted to a
10030 separate file, the executable should contain a @dfn{debug link} giving
10031 the name of the debugging information file (with no directory
10032 components), and a checksum of its contents. (The exact form of a
10033 debug link is described below.) If the full name of the directory
10034 containing the executable is @var{execdir}, and the executable has a
10035 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10036 will automatically search for the debugging information file in three
10041 the directory containing the executable file (that is, it will look
10042 for a file named @file{@var{execdir}/@var{debugfile}},
10044 a subdirectory of that directory named @file{.debug} (that is, the
10045 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10047 a subdirectory of the global debug file directory that includes the
10048 executable's full path, and the name from the link (that is, the file
10049 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10050 @var{globaldebugdir} is the global debug file directory, and
10051 @var{execdir} has been turned into a relative path).
10054 @value{GDBN} checks under each of these names for a debugging
10055 information file whose checksum matches that given in the link, and
10056 reads the debugging information from the first one it finds.
10058 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10059 which has a link containing the name @file{ls.debug}, and the global
10060 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10061 for debug information in @file{/usr/bin/ls.debug},
10062 @file{/usr/bin/.debug/ls.debug}, and
10063 @file{/usr/lib/debug/usr/bin/ls.debug}.
10065 You can set the global debugging info directory's name, and view the
10066 name @value{GDBN} is currently using.
10070 @kindex set debug-file-directory
10071 @item set debug-file-directory @var{directory}
10072 Set the directory which @value{GDBN} searches for separate debugging
10073 information files to @var{directory}.
10075 @kindex show debug-file-directory
10076 @item show debug-file-directory
10077 Show the directory @value{GDBN} searches for separate debugging
10082 @cindex @code{.gnu_debuglink} sections
10083 @cindex debug links
10084 A debug link is a special section of the executable file named
10085 @code{.gnu_debuglink}. The section must contain:
10089 A filename, with any leading directory components removed, followed by
10092 zero to three bytes of padding, as needed to reach the next four-byte
10093 boundary within the section, and
10095 a four-byte CRC checksum, stored in the same endianness used for the
10096 executable file itself. The checksum is computed on the debugging
10097 information file's full contents by the function given below, passing
10098 zero as the @var{crc} argument.
10101 Any executable file format can carry a debug link, as long as it can
10102 contain a section named @code{.gnu_debuglink} with the contents
10105 The debugging information file itself should be an ordinary
10106 executable, containing a full set of linker symbols, sections, and
10107 debugging information. The sections of the debugging information file
10108 should have the same names, addresses and sizes as the original file,
10109 but they need not contain any data --- much like a @code{.bss} section
10110 in an ordinary executable.
10112 As of December 2002, there is no standard GNU utility to produce
10113 separated executable / debugging information file pairs. Ulrich
10114 Drepper's @file{elfutils} package, starting with version 0.53,
10115 contains a version of the @code{strip} command such that the command
10116 @kbd{strip foo -f foo.debug} removes the debugging information from
10117 the executable file @file{foo}, places it in the file
10118 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10120 Since there are many different ways to compute CRC's (different
10121 polynomials, reversals, byte ordering, etc.), the simplest way to
10122 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10123 complete code for a function that computes it:
10125 @kindex @code{gnu_debuglink_crc32}
10128 gnu_debuglink_crc32 (unsigned long crc,
10129 unsigned char *buf, size_t len)
10131 static const unsigned long crc32_table[256] =
10133 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10134 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10135 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10136 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10137 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10138 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10139 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10140 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10141 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10142 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10143 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10144 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10145 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10146 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10147 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10148 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10149 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10150 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10151 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10152 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10153 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10154 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10155 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10156 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10157 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10158 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10159 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10160 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10161 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10162 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10163 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10164 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10165 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10166 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10167 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10168 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10169 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10170 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10171 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10172 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10173 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10174 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10175 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10176 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10177 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10178 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10179 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10180 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10181 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10182 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10183 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10186 unsigned char *end;
10188 crc = ~crc & 0xffffffff;
10189 for (end = buf + len; buf < end; ++buf)
10190 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10191 return ~crc & 0xffffffff;
10196 @node Symbol Errors
10197 @section Errors reading symbol files
10199 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10200 such as symbol types it does not recognize, or known bugs in compiler
10201 output. By default, @value{GDBN} does not notify you of such problems, since
10202 they are relatively common and primarily of interest to people
10203 debugging compilers. If you are interested in seeing information
10204 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10205 only one message about each such type of problem, no matter how many
10206 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10207 to see how many times the problems occur, with the @code{set
10208 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10211 The messages currently printed, and their meanings, include:
10214 @item inner block not inside outer block in @var{symbol}
10216 The symbol information shows where symbol scopes begin and end
10217 (such as at the start of a function or a block of statements). This
10218 error indicates that an inner scope block is not fully contained
10219 in its outer scope blocks.
10221 @value{GDBN} circumvents the problem by treating the inner block as if it had
10222 the same scope as the outer block. In the error message, @var{symbol}
10223 may be shown as ``@code{(don't know)}'' if the outer block is not a
10226 @item block at @var{address} out of order
10228 The symbol information for symbol scope blocks should occur in
10229 order of increasing addresses. This error indicates that it does not
10232 @value{GDBN} does not circumvent this problem, and has trouble
10233 locating symbols in the source file whose symbols it is reading. (You
10234 can often determine what source file is affected by specifying
10235 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10238 @item bad block start address patched
10240 The symbol information for a symbol scope block has a start address
10241 smaller than the address of the preceding source line. This is known
10242 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10244 @value{GDBN} circumvents the problem by treating the symbol scope block as
10245 starting on the previous source line.
10247 @item bad string table offset in symbol @var{n}
10250 Symbol number @var{n} contains a pointer into the string table which is
10251 larger than the size of the string table.
10253 @value{GDBN} circumvents the problem by considering the symbol to have the
10254 name @code{foo}, which may cause other problems if many symbols end up
10257 @item unknown symbol type @code{0x@var{nn}}
10259 The symbol information contains new data types that @value{GDBN} does
10260 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10261 uncomprehended information, in hexadecimal.
10263 @value{GDBN} circumvents the error by ignoring this symbol information.
10264 This usually allows you to debug your program, though certain symbols
10265 are not accessible. If you encounter such a problem and feel like
10266 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10267 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10268 and examine @code{*bufp} to see the symbol.
10270 @item stub type has NULL name
10272 @value{GDBN} could not find the full definition for a struct or class.
10274 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10275 The symbol information for a C@t{++} member function is missing some
10276 information that recent versions of the compiler should have output for
10279 @item info mismatch between compiler and debugger
10281 @value{GDBN} could not parse a type specification output by the compiler.
10286 @chapter Specifying a Debugging Target
10288 @cindex debugging target
10291 A @dfn{target} is the execution environment occupied by your program.
10293 Often, @value{GDBN} runs in the same host environment as your program;
10294 in that case, the debugging target is specified as a side effect when
10295 you use the @code{file} or @code{core} commands. When you need more
10296 flexibility---for example, running @value{GDBN} on a physically separate
10297 host, or controlling a standalone system over a serial port or a
10298 realtime system over a TCP/IP connection---you can use the @code{target}
10299 command to specify one of the target types configured for @value{GDBN}
10300 (@pxref{Target Commands, ,Commands for managing targets}).
10303 * Active Targets:: Active targets
10304 * Target Commands:: Commands for managing targets
10305 * Byte Order:: Choosing target byte order
10306 * Remote:: Remote debugging
10307 * KOD:: Kernel Object Display
10311 @node Active Targets
10312 @section Active targets
10314 @cindex stacking targets
10315 @cindex active targets
10316 @cindex multiple targets
10318 There are three classes of targets: processes, core files, and
10319 executable files. @value{GDBN} can work concurrently on up to three
10320 active targets, one in each class. This allows you to (for example)
10321 start a process and inspect its activity without abandoning your work on
10324 For example, if you execute @samp{gdb a.out}, then the executable file
10325 @code{a.out} is the only active target. If you designate a core file as
10326 well---presumably from a prior run that crashed and coredumped---then
10327 @value{GDBN} has two active targets and uses them in tandem, looking
10328 first in the corefile target, then in the executable file, to satisfy
10329 requests for memory addresses. (Typically, these two classes of target
10330 are complementary, since core files contain only a program's
10331 read-write memory---variables and so on---plus machine status, while
10332 executable files contain only the program text and initialized data.)
10334 When you type @code{run}, your executable file becomes an active process
10335 target as well. When a process target is active, all @value{GDBN}
10336 commands requesting memory addresses refer to that target; addresses in
10337 an active core file or executable file target are obscured while the
10338 process target is active.
10340 Use the @code{core-file} and @code{exec-file} commands to select a new
10341 core file or executable target (@pxref{Files, ,Commands to specify
10342 files}). To specify as a target a process that is already running, use
10343 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10346 @node Target Commands
10347 @section Commands for managing targets
10350 @item target @var{type} @var{parameters}
10351 Connects the @value{GDBN} host environment to a target machine or
10352 process. A target is typically a protocol for talking to debugging
10353 facilities. You use the argument @var{type} to specify the type or
10354 protocol of the target machine.
10356 Further @var{parameters} are interpreted by the target protocol, but
10357 typically include things like device names or host names to connect
10358 with, process numbers, and baud rates.
10360 The @code{target} command does not repeat if you press @key{RET} again
10361 after executing the command.
10363 @kindex help target
10365 Displays the names of all targets available. To display targets
10366 currently selected, use either @code{info target} or @code{info files}
10367 (@pxref{Files, ,Commands to specify files}).
10369 @item help target @var{name}
10370 Describe a particular target, including any parameters necessary to
10373 @kindex set gnutarget
10374 @item set gnutarget @var{args}
10375 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10376 knows whether it is reading an @dfn{executable},
10377 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10378 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10379 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10382 @emph{Warning:} To specify a file format with @code{set gnutarget},
10383 you must know the actual BFD name.
10387 @xref{Files, , Commands to specify files}.
10389 @kindex show gnutarget
10390 @item show gnutarget
10391 Use the @code{show gnutarget} command to display what file format
10392 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10393 @value{GDBN} will determine the file format for each file automatically,
10394 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10397 Here are some common targets (available, or not, depending on the GDB
10401 @kindex target exec
10402 @item target exec @var{program}
10403 An executable file. @samp{target exec @var{program}} is the same as
10404 @samp{exec-file @var{program}}.
10406 @kindex target core
10407 @item target core @var{filename}
10408 A core dump file. @samp{target core @var{filename}} is the same as
10409 @samp{core-file @var{filename}}.
10411 @kindex target remote
10412 @item target remote @var{dev}
10413 Remote serial target in GDB-specific protocol. The argument @var{dev}
10414 specifies what serial device to use for the connection (e.g.
10415 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10416 supports the @code{load} command. This is only useful if you have
10417 some other way of getting the stub to the target system, and you can put
10418 it somewhere in memory where it won't get clobbered by the download.
10422 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10430 works; however, you cannot assume that a specific memory map, device
10431 drivers, or even basic I/O is available, although some simulators do
10432 provide these. For info about any processor-specific simulator details,
10433 see the appropriate section in @ref{Embedded Processors, ,Embedded
10438 Some configurations may include these targets as well:
10442 @kindex target nrom
10443 @item target nrom @var{dev}
10444 NetROM ROM emulator. This target only supports downloading.
10448 Different targets are available on different configurations of @value{GDBN};
10449 your configuration may have more or fewer targets.
10451 Many remote targets require you to download the executable's code
10452 once you've successfully established a connection.
10456 @kindex load @var{filename}
10457 @item load @var{filename}
10458 Depending on what remote debugging facilities are configured into
10459 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10460 is meant to make @var{filename} (an executable) available for debugging
10461 on the remote system---by downloading, or dynamic linking, for example.
10462 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10463 the @code{add-symbol-file} command.
10465 If your @value{GDBN} does not have a @code{load} command, attempting to
10466 execute it gets the error message ``@code{You can't do that when your
10467 target is @dots{}}''
10469 The file is loaded at whatever address is specified in the executable.
10470 For some object file formats, you can specify the load address when you
10471 link the program; for other formats, like a.out, the object file format
10472 specifies a fixed address.
10473 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10475 @code{load} does not repeat if you press @key{RET} again after using it.
10479 @section Choosing target byte order
10481 @cindex choosing target byte order
10482 @cindex target byte order
10484 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10485 offer the ability to run either big-endian or little-endian byte
10486 orders. Usually the executable or symbol will include a bit to
10487 designate the endian-ness, and you will not need to worry about
10488 which to use. However, you may still find it useful to adjust
10489 @value{GDBN}'s idea of processor endian-ness manually.
10492 @kindex set endian big
10493 @item set endian big
10494 Instruct @value{GDBN} to assume the target is big-endian.
10496 @kindex set endian little
10497 @item set endian little
10498 Instruct @value{GDBN} to assume the target is little-endian.
10500 @kindex set endian auto
10501 @item set endian auto
10502 Instruct @value{GDBN} to use the byte order associated with the
10506 Display @value{GDBN}'s current idea of the target byte order.
10510 Note that these commands merely adjust interpretation of symbolic
10511 data on the host, and that they have absolutely no effect on the
10515 @section Remote debugging
10516 @cindex remote debugging
10518 If you are trying to debug a program running on a machine that cannot run
10519 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10520 For example, you might use remote debugging on an operating system kernel,
10521 or on a small system which does not have a general purpose operating system
10522 powerful enough to run a full-featured debugger.
10524 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10525 to make this work with particular debugging targets. In addition,
10526 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10527 but not specific to any particular target system) which you can use if you
10528 write the remote stubs---the code that runs on the remote system to
10529 communicate with @value{GDBN}.
10531 Other remote targets may be available in your
10532 configuration of @value{GDBN}; use @code{help target} to list them.
10535 @section Kernel Object Display
10537 @cindex kernel object display
10538 @cindex kernel object
10541 Some targets support kernel object display. Using this facility,
10542 @value{GDBN} communicates specially with the underlying operating system
10543 and can display information about operating system-level objects such as
10544 mutexes and other synchronization objects. Exactly which objects can be
10545 displayed is determined on a per-OS basis.
10547 Use the @code{set os} command to set the operating system. This tells
10548 @value{GDBN} which kernel object display module to initialize:
10551 (@value{GDBP}) set os cisco
10554 If @code{set os} succeeds, @value{GDBN} will display some information
10555 about the operating system, and will create a new @code{info} command
10556 which can be used to query the target. The @code{info} command is named
10557 after the operating system:
10560 (@value{GDBP}) info cisco
10561 List of Cisco Kernel Objects
10563 any Any and all objects
10566 Further subcommands can be used to query about particular objects known
10569 There is currently no way to determine whether a given operating system
10570 is supported other than to try it.
10573 @node Remote Debugging
10574 @chapter Debugging remote programs
10577 * Connecting:: Connecting to a remote target
10578 * Server:: Using the gdbserver program
10579 * NetWare:: Using the gdbserve.nlm program
10580 * Remote configuration:: Remote configuration
10581 * remote stub:: Implementing a remote stub
10585 @section Connecting to a remote target
10587 On the @value{GDBN} host machine, you will need an unstripped copy of
10588 your program, since @value{GDBN} needs symobl and debugging information.
10589 Start up @value{GDBN} as usual, using the name of the local copy of your
10590 program as the first argument.
10592 @cindex serial line, @code{target remote}
10593 If you're using a serial line, you may want to give @value{GDBN} the
10594 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10595 before the @code{target} command.
10597 After that, use @code{target remote} to establish communications with
10598 the target machine. Its argument specifies how to communicate---either
10599 via a devicename attached to a direct serial line, or a TCP or UDP port
10600 (possibly to a terminal server which in turn has a serial line to the
10601 target). For example, to use a serial line connected to the device
10602 named @file{/dev/ttyb}:
10605 target remote /dev/ttyb
10608 @cindex TCP port, @code{target remote}
10609 To use a TCP connection, use an argument of the form
10610 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10611 For example, to connect to port 2828 on a
10612 terminal server named @code{manyfarms}:
10615 target remote manyfarms:2828
10618 If your remote target is actually running on the same machine as
10619 your debugger session (e.g.@: a simulator of your target running on
10620 the same host), you can omit the hostname. For example, to connect
10621 to port 1234 on your local machine:
10624 target remote :1234
10628 Note that the colon is still required here.
10630 @cindex UDP port, @code{target remote}
10631 To use a UDP connection, use an argument of the form
10632 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10633 on a terminal server named @code{manyfarms}:
10636 target remote udp:manyfarms:2828
10639 When using a UDP connection for remote debugging, you should keep in mind
10640 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10641 busy or unreliable networks, which will cause havoc with your debugging
10644 Now you can use all the usual commands to examine and change data and to
10645 step and continue the remote program.
10647 @cindex interrupting remote programs
10648 @cindex remote programs, interrupting
10649 Whenever @value{GDBN} is waiting for the remote program, if you type the
10650 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10651 program. This may or may not succeed, depending in part on the hardware
10652 and the serial drivers the remote system uses. If you type the
10653 interrupt character once again, @value{GDBN} displays this prompt:
10656 Interrupted while waiting for the program.
10657 Give up (and stop debugging it)? (y or n)
10660 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10661 (If you decide you want to try again later, you can use @samp{target
10662 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10663 goes back to waiting.
10666 @kindex detach (remote)
10668 When you have finished debugging the remote program, you can use the
10669 @code{detach} command to release it from @value{GDBN} control.
10670 Detaching from the target normally resumes its execution, but the results
10671 will depend on your particular remote stub. After the @code{detach}
10672 command, @value{GDBN} is free to connect to another target.
10676 The @code{disconnect} command behaves like @code{detach}, except that
10677 the target is generally not resumed. It will wait for @value{GDBN}
10678 (this instance or another one) to connect and continue debugging. After
10679 the @code{disconnect} command, @value{GDBN} is again free to connect to
10684 @section Using the @code{gdbserver} program
10687 @cindex remote connection without stubs
10688 @code{gdbserver} is a control program for Unix-like systems, which
10689 allows you to connect your program with a remote @value{GDBN} via
10690 @code{target remote}---but without linking in the usual debugging stub.
10692 @code{gdbserver} is not a complete replacement for the debugging stubs,
10693 because it requires essentially the same operating-system facilities
10694 that @value{GDBN} itself does. In fact, a system that can run
10695 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10696 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10697 because it is a much smaller program than @value{GDBN} itself. It is
10698 also easier to port than all of @value{GDBN}, so you may be able to get
10699 started more quickly on a new system by using @code{gdbserver}.
10700 Finally, if you develop code for real-time systems, you may find that
10701 the tradeoffs involved in real-time operation make it more convenient to
10702 do as much development work as possible on another system, for example
10703 by cross-compiling. You can use @code{gdbserver} to make a similar
10704 choice for debugging.
10706 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10707 or a TCP connection, using the standard @value{GDBN} remote serial
10711 @item On the target machine,
10712 you need to have a copy of the program you want to debug.
10713 @code{gdbserver} does not need your program's symbol table, so you can
10714 strip the program if necessary to save space. @value{GDBN} on the host
10715 system does all the symbol handling.
10717 To use the server, you must tell it how to communicate with @value{GDBN};
10718 the name of your program; and the arguments for your program. The usual
10722 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10725 @var{comm} is either a device name (to use a serial line) or a TCP
10726 hostname and portnumber. For example, to debug Emacs with the argument
10727 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10731 target> gdbserver /dev/com1 emacs foo.txt
10734 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10737 To use a TCP connection instead of a serial line:
10740 target> gdbserver host:2345 emacs foo.txt
10743 The only difference from the previous example is the first argument,
10744 specifying that you are communicating with the host @value{GDBN} via
10745 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10746 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10747 (Currently, the @samp{host} part is ignored.) You can choose any number
10748 you want for the port number as long as it does not conflict with any
10749 TCP ports already in use on the target system (for example, @code{23} is
10750 reserved for @code{telnet}).@footnote{If you choose a port number that
10751 conflicts with another service, @code{gdbserver} prints an error message
10752 and exits.} You must use the same port number with the host @value{GDBN}
10753 @code{target remote} command.
10755 On some targets, @code{gdbserver} can also attach to running programs.
10756 This is accomplished via the @code{--attach} argument. The syntax is:
10759 target> gdbserver @var{comm} --attach @var{pid}
10762 @var{pid} is the process ID of a currently running process. It isn't necessary
10763 to point @code{gdbserver} at a binary for the running process.
10766 @cindex attach to a program by name
10767 You can debug processes by name instead of process ID if your target has the
10768 @code{pidof} utility:
10771 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10774 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10775 has multiple threads, most versions of @code{pidof} support the
10776 @code{-s} option to only return the first process ID.
10778 @item On the host machine,
10779 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10780 For TCP connections, you must start up @code{gdbserver} prior to using
10781 the @code{target remote} command. Otherwise you may get an error whose
10782 text depends on the host system, but which usually looks something like
10783 @samp{Connection refused}. You don't need to use the @code{load}
10784 command in @value{GDBN} when using gdbserver, since the program is
10785 already on the target.
10790 @section Using the @code{gdbserve.nlm} program
10792 @kindex gdbserve.nlm
10793 @code{gdbserve.nlm} is a control program for NetWare systems, which
10794 allows you to connect your program with a remote @value{GDBN} via
10795 @code{target remote}.
10797 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10798 using the standard @value{GDBN} remote serial protocol.
10801 @item On the target machine,
10802 you need to have a copy of the program you want to debug.
10803 @code{gdbserve.nlm} does not need your program's symbol table, so you
10804 can strip the program if necessary to save space. @value{GDBN} on the
10805 host system does all the symbol handling.
10807 To use the server, you must tell it how to communicate with
10808 @value{GDBN}; the name of your program; and the arguments for your
10809 program. The syntax is:
10812 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10813 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10816 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10817 the baud rate used by the connection. @var{port} and @var{node} default
10818 to 0, @var{baud} defaults to 9600@dmn{bps}.
10820 For example, to debug Emacs with the argument @samp{foo.txt}and
10821 communicate with @value{GDBN} over serial port number 2 or board 1
10822 using a 19200@dmn{bps} connection:
10825 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10829 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
10830 Connecting to a remote target}).
10834 @node Remote configuration
10835 @section Remote configuration
10837 The following configuration options are available when debugging remote
10841 @kindex set remote hardware-watchpoint-limit
10842 @kindex set remote hardware-breakpoint-limit
10843 @anchor{set remote hardware-watchpoint-limit}
10844 @anchor{set remote hardware-breakpoint-limit}
10845 @item set remote hardware-watchpoint-limit @var{limit}
10846 @itemx set remote hardware-breakpoint-limit @var{limit}
10847 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10848 watchpoints. A limit of -1, the default, is treated as unlimited.
10852 @section Implementing a remote stub
10854 @cindex debugging stub, example
10855 @cindex remote stub, example
10856 @cindex stub example, remote debugging
10857 The stub files provided with @value{GDBN} implement the target side of the
10858 communication protocol, and the @value{GDBN} side is implemented in the
10859 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10860 these subroutines to communicate, and ignore the details. (If you're
10861 implementing your own stub file, you can still ignore the details: start
10862 with one of the existing stub files. @file{sparc-stub.c} is the best
10863 organized, and therefore the easiest to read.)
10865 @cindex remote serial debugging, overview
10866 To debug a program running on another machine (the debugging
10867 @dfn{target} machine), you must first arrange for all the usual
10868 prerequisites for the program to run by itself. For example, for a C
10873 A startup routine to set up the C runtime environment; these usually
10874 have a name like @file{crt0}. The startup routine may be supplied by
10875 your hardware supplier, or you may have to write your own.
10878 A C subroutine library to support your program's
10879 subroutine calls, notably managing input and output.
10882 A way of getting your program to the other machine---for example, a
10883 download program. These are often supplied by the hardware
10884 manufacturer, but you may have to write your own from hardware
10888 The next step is to arrange for your program to use a serial port to
10889 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10890 machine). In general terms, the scheme looks like this:
10894 @value{GDBN} already understands how to use this protocol; when everything
10895 else is set up, you can simply use the @samp{target remote} command
10896 (@pxref{Targets,,Specifying a Debugging Target}).
10898 @item On the target,
10899 you must link with your program a few special-purpose subroutines that
10900 implement the @value{GDBN} remote serial protocol. The file containing these
10901 subroutines is called a @dfn{debugging stub}.
10903 On certain remote targets, you can use an auxiliary program
10904 @code{gdbserver} instead of linking a stub into your program.
10905 @xref{Server,,Using the @code{gdbserver} program}, for details.
10908 The debugging stub is specific to the architecture of the remote
10909 machine; for example, use @file{sparc-stub.c} to debug programs on
10912 @cindex remote serial stub list
10913 These working remote stubs are distributed with @value{GDBN}:
10918 @cindex @file{i386-stub.c}
10921 For Intel 386 and compatible architectures.
10924 @cindex @file{m68k-stub.c}
10925 @cindex Motorola 680x0
10927 For Motorola 680x0 architectures.
10930 @cindex @file{sh-stub.c}
10933 For Renesas SH architectures.
10936 @cindex @file{sparc-stub.c}
10938 For @sc{sparc} architectures.
10940 @item sparcl-stub.c
10941 @cindex @file{sparcl-stub.c}
10944 For Fujitsu @sc{sparclite} architectures.
10948 The @file{README} file in the @value{GDBN} distribution may list other
10949 recently added stubs.
10952 * Stub Contents:: What the stub can do for you
10953 * Bootstrapping:: What you must do for the stub
10954 * Debug Session:: Putting it all together
10957 @node Stub Contents
10958 @subsection What the stub can do for you
10960 @cindex remote serial stub
10961 The debugging stub for your architecture supplies these three
10965 @item set_debug_traps
10966 @kindex set_debug_traps
10967 @cindex remote serial stub, initialization
10968 This routine arranges for @code{handle_exception} to run when your
10969 program stops. You must call this subroutine explicitly near the
10970 beginning of your program.
10972 @item handle_exception
10973 @kindex handle_exception
10974 @cindex remote serial stub, main routine
10975 This is the central workhorse, but your program never calls it
10976 explicitly---the setup code arranges for @code{handle_exception} to
10977 run when a trap is triggered.
10979 @code{handle_exception} takes control when your program stops during
10980 execution (for example, on a breakpoint), and mediates communications
10981 with @value{GDBN} on the host machine. This is where the communications
10982 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10983 representative on the target machine. It begins by sending summary
10984 information on the state of your program, then continues to execute,
10985 retrieving and transmitting any information @value{GDBN} needs, until you
10986 execute a @value{GDBN} command that makes your program resume; at that point,
10987 @code{handle_exception} returns control to your own code on the target
10991 @cindex @code{breakpoint} subroutine, remote
10992 Use this auxiliary subroutine to make your program contain a
10993 breakpoint. Depending on the particular situation, this may be the only
10994 way for @value{GDBN} to get control. For instance, if your target
10995 machine has some sort of interrupt button, you won't need to call this;
10996 pressing the interrupt button transfers control to
10997 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10998 simply receiving characters on the serial port may also trigger a trap;
10999 again, in that situation, you don't need to call @code{breakpoint} from
11000 your own program---simply running @samp{target remote} from the host
11001 @value{GDBN} session gets control.
11003 Call @code{breakpoint} if none of these is true, or if you simply want
11004 to make certain your program stops at a predetermined point for the
11005 start of your debugging session.
11008 @node Bootstrapping
11009 @subsection What you must do for the stub
11011 @cindex remote stub, support routines
11012 The debugging stubs that come with @value{GDBN} are set up for a particular
11013 chip architecture, but they have no information about the rest of your
11014 debugging target machine.
11016 First of all you need to tell the stub how to communicate with the
11020 @item int getDebugChar()
11021 @kindex getDebugChar
11022 Write this subroutine to read a single character from the serial port.
11023 It may be identical to @code{getchar} for your target system; a
11024 different name is used to allow you to distinguish the two if you wish.
11026 @item void putDebugChar(int)
11027 @kindex putDebugChar
11028 Write this subroutine to write a single character to the serial port.
11029 It may be identical to @code{putchar} for your target system; a
11030 different name is used to allow you to distinguish the two if you wish.
11033 @cindex control C, and remote debugging
11034 @cindex interrupting remote targets
11035 If you want @value{GDBN} to be able to stop your program while it is
11036 running, you need to use an interrupt-driven serial driver, and arrange
11037 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11038 character). That is the character which @value{GDBN} uses to tell the
11039 remote system to stop.
11041 Getting the debugging target to return the proper status to @value{GDBN}
11042 probably requires changes to the standard stub; one quick and dirty way
11043 is to just execute a breakpoint instruction (the ``dirty'' part is that
11044 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11046 Other routines you need to supply are:
11049 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11050 @kindex exceptionHandler
11051 Write this function to install @var{exception_address} in the exception
11052 handling tables. You need to do this because the stub does not have any
11053 way of knowing what the exception handling tables on your target system
11054 are like (for example, the processor's table might be in @sc{rom},
11055 containing entries which point to a table in @sc{ram}).
11056 @var{exception_number} is the exception number which should be changed;
11057 its meaning is architecture-dependent (for example, different numbers
11058 might represent divide by zero, misaligned access, etc). When this
11059 exception occurs, control should be transferred directly to
11060 @var{exception_address}, and the processor state (stack, registers,
11061 and so on) should be just as it is when a processor exception occurs. So if
11062 you want to use a jump instruction to reach @var{exception_address}, it
11063 should be a simple jump, not a jump to subroutine.
11065 For the 386, @var{exception_address} should be installed as an interrupt
11066 gate so that interrupts are masked while the handler runs. The gate
11067 should be at privilege level 0 (the most privileged level). The
11068 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11069 help from @code{exceptionHandler}.
11071 @item void flush_i_cache()
11072 @kindex flush_i_cache
11073 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11074 instruction cache, if any, on your target machine. If there is no
11075 instruction cache, this subroutine may be a no-op.
11077 On target machines that have instruction caches, @value{GDBN} requires this
11078 function to make certain that the state of your program is stable.
11082 You must also make sure this library routine is available:
11085 @item void *memset(void *, int, int)
11087 This is the standard library function @code{memset} that sets an area of
11088 memory to a known value. If you have one of the free versions of
11089 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11090 either obtain it from your hardware manufacturer, or write your own.
11093 If you do not use the GNU C compiler, you may need other standard
11094 library subroutines as well; this varies from one stub to another,
11095 but in general the stubs are likely to use any of the common library
11096 subroutines which @code{@value{GCC}} generates as inline code.
11099 @node Debug Session
11100 @subsection Putting it all together
11102 @cindex remote serial debugging summary
11103 In summary, when your program is ready to debug, you must follow these
11108 Make sure you have defined the supporting low-level routines
11109 (@pxref{Bootstrapping,,What you must do for the stub}):
11111 @code{getDebugChar}, @code{putDebugChar},
11112 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11116 Insert these lines near the top of your program:
11124 For the 680x0 stub only, you need to provide a variable called
11125 @code{exceptionHook}. Normally you just use:
11128 void (*exceptionHook)() = 0;
11132 but if before calling @code{set_debug_traps}, you set it to point to a
11133 function in your program, that function is called when
11134 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11135 error). The function indicated by @code{exceptionHook} is called with
11136 one parameter: an @code{int} which is the exception number.
11139 Compile and link together: your program, the @value{GDBN} debugging stub for
11140 your target architecture, and the supporting subroutines.
11143 Make sure you have a serial connection between your target machine and
11144 the @value{GDBN} host, and identify the serial port on the host.
11147 @c The "remote" target now provides a `load' command, so we should
11148 @c document that. FIXME.
11149 Download your program to your target machine (or get it there by
11150 whatever means the manufacturer provides), and start it.
11153 Start @value{GDBN} on the host, and connect to the target
11154 (@pxref{Connecting,,Connecting to a remote target}).
11158 @node Configurations
11159 @chapter Configuration-Specific Information
11161 While nearly all @value{GDBN} commands are available for all native and
11162 cross versions of the debugger, there are some exceptions. This chapter
11163 describes things that are only available in certain configurations.
11165 There are three major categories of configurations: native
11166 configurations, where the host and target are the same, embedded
11167 operating system configurations, which are usually the same for several
11168 different processor architectures, and bare embedded processors, which
11169 are quite different from each other.
11174 * Embedded Processors::
11181 This section describes details specific to particular native
11186 * SVR4 Process Information:: SVR4 process information
11187 * DJGPP Native:: Features specific to the DJGPP port
11188 * Cygwin Native:: Features specific to the Cygwin port
11194 On HP-UX systems, if you refer to a function or variable name that
11195 begins with a dollar sign, @value{GDBN} searches for a user or system
11196 name first, before it searches for a convenience variable.
11198 @node SVR4 Process Information
11199 @subsection SVR4 process information
11202 @cindex process image
11204 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11205 used to examine the image of a running process using file-system
11206 subroutines. If @value{GDBN} is configured for an operating system with
11207 this facility, the command @code{info proc} is available to report on
11208 several kinds of information about the process running your program.
11209 @code{info proc} works only on SVR4 systems that include the
11210 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11211 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11216 Summarize available information about the process.
11218 @kindex info proc mappings
11219 @item info proc mappings
11220 Report on the address ranges accessible in the program, with information
11221 on whether your program may read, write, or execute each range.
11223 @comment These sub-options of 'info proc' were not included when
11224 @comment procfs.c was re-written. Keep their descriptions around
11225 @comment against the day when someone finds the time to put them back in.
11226 @kindex info proc times
11227 @item info proc times
11228 Starting time, user CPU time, and system CPU time for your program and
11231 @kindex info proc id
11233 Report on the process IDs related to your program: its own process ID,
11234 the ID of its parent, the process group ID, and the session ID.
11236 @kindex info proc status
11237 @item info proc status
11238 General information on the state of the process. If the process is
11239 stopped, this report includes the reason for stopping, and any signal
11242 @item info proc all
11243 Show all the above information about the process.
11248 @subsection Features for Debugging @sc{djgpp} Programs
11249 @cindex @sc{djgpp} debugging
11250 @cindex native @sc{djgpp} debugging
11251 @cindex MS-DOS-specific commands
11253 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11254 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11255 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11256 top of real-mode DOS systems and their emulations.
11258 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11259 defines a few commands specific to the @sc{djgpp} port. This
11260 subsection describes those commands.
11265 This is a prefix of @sc{djgpp}-specific commands which print
11266 information about the target system and important OS structures.
11269 @cindex MS-DOS system info
11270 @cindex free memory information (MS-DOS)
11271 @item info dos sysinfo
11272 This command displays assorted information about the underlying
11273 platform: the CPU type and features, the OS version and flavor, the
11274 DPMI version, and the available conventional and DPMI memory.
11279 @cindex segment descriptor tables
11280 @cindex descriptor tables display
11282 @itemx info dos ldt
11283 @itemx info dos idt
11284 These 3 commands display entries from, respectively, Global, Local,
11285 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11286 tables are data structures which store a descriptor for each segment
11287 that is currently in use. The segment's selector is an index into a
11288 descriptor table; the table entry for that index holds the
11289 descriptor's base address and limit, and its attributes and access
11292 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11293 segment (used for both data and the stack), and a DOS segment (which
11294 allows access to DOS/BIOS data structures and absolute addresses in
11295 conventional memory). However, the DPMI host will usually define
11296 additional segments in order to support the DPMI environment.
11298 @cindex garbled pointers
11299 These commands allow to display entries from the descriptor tables.
11300 Without an argument, all entries from the specified table are
11301 displayed. An argument, which should be an integer expression, means
11302 display a single entry whose index is given by the argument. For
11303 example, here's a convenient way to display information about the
11304 debugged program's data segment:
11307 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11308 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11312 This comes in handy when you want to see whether a pointer is outside
11313 the data segment's limit (i.e.@: @dfn{garbled}).
11315 @cindex page tables display (MS-DOS)
11317 @itemx info dos pte
11318 These two commands display entries from, respectively, the Page
11319 Directory and the Page Tables. Page Directories and Page Tables are
11320 data structures which control how virtual memory addresses are mapped
11321 into physical addresses. A Page Table includes an entry for every
11322 page of memory that is mapped into the program's address space; there
11323 may be several Page Tables, each one holding up to 4096 entries. A
11324 Page Directory has up to 4096 entries, one each for every Page Table
11325 that is currently in use.
11327 Without an argument, @kbd{info dos pde} displays the entire Page
11328 Directory, and @kbd{info dos pte} displays all the entries in all of
11329 the Page Tables. An argument, an integer expression, given to the
11330 @kbd{info dos pde} command means display only that entry from the Page
11331 Directory table. An argument given to the @kbd{info dos pte} command
11332 means display entries from a single Page Table, the one pointed to by
11333 the specified entry in the Page Directory.
11335 @cindex direct memory access (DMA) on MS-DOS
11336 These commands are useful when your program uses @dfn{DMA} (Direct
11337 Memory Access), which needs physical addresses to program the DMA
11340 These commands are supported only with some DPMI servers.
11342 @cindex physical address from linear address
11343 @item info dos address-pte @var{addr}
11344 This command displays the Page Table entry for a specified linear
11345 address. The argument linear address @var{addr} should already have the
11346 appropriate segment's base address added to it, because this command
11347 accepts addresses which may belong to @emph{any} segment. For
11348 example, here's how to display the Page Table entry for the page where
11349 the variable @code{i} is stored:
11352 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11353 @exdent @code{Page Table entry for address 0x11a00d30:}
11354 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11358 This says that @code{i} is stored at offset @code{0xd30} from the page
11359 whose physical base address is @code{0x02698000}, and prints all the
11360 attributes of that page.
11362 Note that you must cast the addresses of variables to a @code{char *},
11363 since otherwise the value of @code{__djgpp_base_address}, the base
11364 address of all variables and functions in a @sc{djgpp} program, will
11365 be added using the rules of C pointer arithmetics: if @code{i} is
11366 declared an @code{int}, @value{GDBN} will add 4 times the value of
11367 @code{__djgpp_base_address} to the address of @code{i}.
11369 Here's another example, it displays the Page Table entry for the
11373 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11374 @exdent @code{Page Table entry for address 0x29110:}
11375 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11379 (The @code{+ 3} offset is because the transfer buffer's address is the
11380 3rd member of the @code{_go32_info_block} structure.) The output of
11381 this command clearly shows that addresses in conventional memory are
11382 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11384 This command is supported only with some DPMI servers.
11387 @node Cygwin Native
11388 @subsection Features for Debugging MS Windows PE executables
11389 @cindex MS Windows debugging
11390 @cindex native Cygwin debugging
11391 @cindex Cygwin-specific commands
11393 @value{GDBN} supports native debugging of MS Windows programs, including
11394 DLLs with and without symbolic debugging information. There are various
11395 additional Cygwin-specific commands, described in this subsection. The
11396 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11397 that have no debugging symbols.
11403 This is a prefix of MS Windows specific commands which print
11404 information about the target system and important OS structures.
11406 @item info w32 selector
11407 This command displays information returned by
11408 the Win32 API @code{GetThreadSelectorEntry} function.
11409 It takes an optional argument that is evaluated to
11410 a long value to give the information about this given selector.
11411 Without argument, this command displays information
11412 about the the six segment registers.
11416 This is a Cygwin specific alias of info shared.
11418 @kindex dll-symbols
11420 This command loads symbols from a dll similarly to
11421 add-sym command but without the need to specify a base address.
11423 @kindex set new-console
11424 @item set new-console @var{mode}
11425 If @var{mode} is @code{on} the debuggee will
11426 be started in a new console on next start.
11427 If @var{mode} is @code{off}i, the debuggee will
11428 be started in the same console as the debugger.
11430 @kindex show new-console
11431 @item show new-console
11432 Displays whether a new console is used
11433 when the debuggee is started.
11435 @kindex set new-group
11436 @item set new-group @var{mode}
11437 This boolean value controls whether the debuggee should
11438 start a new group or stay in the same group as the debugger.
11439 This affects the way the Windows OS handles
11442 @kindex show new-group
11443 @item show new-group
11444 Displays current value of new-group boolean.
11446 @kindex set debugevents
11447 @item set debugevents
11448 This boolean value adds debug output concerning events seen by the debugger.
11450 @kindex set debugexec
11451 @item set debugexec
11452 This boolean value adds debug output concerning execute events
11453 seen by the debugger.
11455 @kindex set debugexceptions
11456 @item set debugexceptions
11457 This boolean value adds debug ouptut concerning exception events
11458 seen by the debugger.
11460 @kindex set debugmemory
11461 @item set debugmemory
11462 This boolean value adds debug ouptut concerning memory events
11463 seen by the debugger.
11467 This boolean values specifies whether the debuggee is called
11468 via a shell or directly (default value is on).
11472 Displays if the debuggee will be started with a shell.
11477 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11480 @node Non-debug DLL symbols
11481 @subsubsection Support for DLLs without debugging symbols
11482 @cindex DLLs with no debugging symbols
11483 @cindex Minimal symbols and DLLs
11485 Very often on windows, some of the DLLs that your program relies on do
11486 not include symbolic debugging information (for example,
11487 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11488 symbols in a DLL, it relies on the minimal amount of symbolic
11489 information contained in the DLL's export table. This subsubsection
11490 describes working with such symbols, known internally to @value{GDBN} as
11491 ``minimal symbols''.
11493 Note that before the debugged program has started execution, no DLLs
11494 will have been loaded. The easiest way around this problem is simply to
11495 start the program --- either by setting a breakpoint or letting the
11496 program run once to completion. It is also possible to force
11497 @value{GDBN} to load a particular DLL before starting the executable ---
11498 see the shared library information in @pxref{Files} or the
11499 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11500 explicitly loading symbols from a DLL with no debugging information will
11501 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11502 which may adversely affect symbol lookup performance.
11504 @subsubsection DLL name prefixes
11506 In keeping with the naming conventions used by the Microsoft debugging
11507 tools, DLL export symbols are made available with a prefix based on the
11508 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11509 also entered into the symbol table, so @code{CreateFileA} is often
11510 sufficient. In some cases there will be name clashes within a program
11511 (particularly if the executable itself includes full debugging symbols)
11512 necessitating the use of the fully qualified name when referring to the
11513 contents of the DLL. Use single-quotes around the name to avoid the
11514 exclamation mark (``!'') being interpreted as a language operator.
11516 Note that the internal name of the DLL may be all upper-case, even
11517 though the file name of the DLL is lower-case, or vice-versa. Since
11518 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11519 some confusion. If in doubt, try the @code{info functions} and
11520 @code{info variables} commands or even @code{maint print msymbols} (see
11521 @pxref{Symbols}). Here's an example:
11524 (gdb) info function CreateFileA
11525 All functions matching regular expression "CreateFileA":
11527 Non-debugging symbols:
11528 0x77e885f4 CreateFileA
11529 0x77e885f4 KERNEL32!CreateFileA
11533 (gdb) info function !
11534 All functions matching regular expression "!":
11536 Non-debugging symbols:
11537 0x6100114c cygwin1!__assert
11538 0x61004034 cygwin1!_dll_crt0@@0
11539 0x61004240 cygwin1!dll_crt0(per_process *)
11543 @subsubsection Working with minimal symbols
11545 Symbols extracted from a DLL's export table do not contain very much
11546 type information. All that @value{GDBN} can do is guess whether a symbol
11547 refers to a function or variable depending on the linker section that
11548 contains the symbol. Also note that the actual contents of the memory
11549 contained in a DLL are not available unless the program is running. This
11550 means that you cannot examine the contents of a variable or disassemble
11551 a function within a DLL without a running program.
11553 Variables are generally treated as pointers and dereferenced
11554 automatically. For this reason, it is often necessary to prefix a
11555 variable name with the address-of operator (``&'') and provide explicit
11556 type information in the command. Here's an example of the type of
11560 (gdb) print 'cygwin1!__argv'
11565 (gdb) x 'cygwin1!__argv'
11566 0x10021610: "\230y\""
11569 And two possible solutions:
11572 (gdb) print ((char **)'cygwin1!__argv')[0]
11573 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11577 (gdb) x/2x &'cygwin1!__argv'
11578 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11579 (gdb) x/x 0x10021608
11580 0x10021608: 0x0022fd98
11581 (gdb) x/s 0x0022fd98
11582 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11585 Setting a break point within a DLL is possible even before the program
11586 starts execution. However, under these circumstances, @value{GDBN} can't
11587 examine the initial instructions of the function in order to skip the
11588 function's frame set-up code. You can work around this by using ``*&''
11589 to set the breakpoint at a raw memory address:
11592 (gdb) break *&'python22!PyOS_Readline'
11593 Breakpoint 1 at 0x1e04eff0
11596 The author of these extensions is not entirely convinced that setting a
11597 break point within a shared DLL like @file{kernel32.dll} is completely
11601 @section Embedded Operating Systems
11603 This section describes configurations involving the debugging of
11604 embedded operating systems that are available for several different
11608 * VxWorks:: Using @value{GDBN} with VxWorks
11611 @value{GDBN} includes the ability to debug programs running on
11612 various real-time operating systems.
11615 @subsection Using @value{GDBN} with VxWorks
11621 @kindex target vxworks
11622 @item target vxworks @var{machinename}
11623 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11624 is the target system's machine name or IP address.
11628 On VxWorks, @code{load} links @var{filename} dynamically on the
11629 current target system as well as adding its symbols in @value{GDBN}.
11631 @value{GDBN} enables developers to spawn and debug tasks running on networked
11632 VxWorks targets from a Unix host. Already-running tasks spawned from
11633 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11634 both the Unix host and on the VxWorks target. The program
11635 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11636 installed with the name @code{vxgdb}, to distinguish it from a
11637 @value{GDBN} for debugging programs on the host itself.)
11640 @item VxWorks-timeout @var{args}
11641 @kindex vxworks-timeout
11642 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11643 This option is set by the user, and @var{args} represents the number of
11644 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11645 your VxWorks target is a slow software simulator or is on the far side
11646 of a thin network line.
11649 The following information on connecting to VxWorks was current when
11650 this manual was produced; newer releases of VxWorks may use revised
11653 @kindex INCLUDE_RDB
11654 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11655 to include the remote debugging interface routines in the VxWorks
11656 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11657 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11658 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11659 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11660 information on configuring and remaking VxWorks, see the manufacturer's
11662 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11664 Once you have included @file{rdb.a} in your VxWorks system image and set
11665 your Unix execution search path to find @value{GDBN}, you are ready to
11666 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11667 @code{vxgdb}, depending on your installation).
11669 @value{GDBN} comes up showing the prompt:
11676 * VxWorks Connection:: Connecting to VxWorks
11677 * VxWorks Download:: VxWorks download
11678 * VxWorks Attach:: Running tasks
11681 @node VxWorks Connection
11682 @subsubsection Connecting to VxWorks
11684 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11685 network. To connect to a target whose host name is ``@code{tt}'', type:
11688 (vxgdb) target vxworks tt
11692 @value{GDBN} displays messages like these:
11695 Attaching remote machine across net...
11700 @value{GDBN} then attempts to read the symbol tables of any object modules
11701 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11702 these files by searching the directories listed in the command search
11703 path (@pxref{Environment, ,Your program's environment}); if it fails
11704 to find an object file, it displays a message such as:
11707 prog.o: No such file or directory.
11710 When this happens, add the appropriate directory to the search path with
11711 the @value{GDBN} command @code{path}, and execute the @code{target}
11714 @node VxWorks Download
11715 @subsubsection VxWorks download
11717 @cindex download to VxWorks
11718 If you have connected to the VxWorks target and you want to debug an
11719 object that has not yet been loaded, you can use the @value{GDBN}
11720 @code{load} command to download a file from Unix to VxWorks
11721 incrementally. The object file given as an argument to the @code{load}
11722 command is actually opened twice: first by the VxWorks target in order
11723 to download the code, then by @value{GDBN} in order to read the symbol
11724 table. This can lead to problems if the current working directories on
11725 the two systems differ. If both systems have NFS mounted the same
11726 filesystems, you can avoid these problems by using absolute paths.
11727 Otherwise, it is simplest to set the working directory on both systems
11728 to the directory in which the object file resides, and then to reference
11729 the file by its name, without any path. For instance, a program
11730 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11731 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11732 program, type this on VxWorks:
11735 -> cd "@var{vxpath}/vw/demo/rdb"
11739 Then, in @value{GDBN}, type:
11742 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11743 (vxgdb) load prog.o
11746 @value{GDBN} displays a response similar to this:
11749 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11752 You can also use the @code{load} command to reload an object module
11753 after editing and recompiling the corresponding source file. Note that
11754 this makes @value{GDBN} delete all currently-defined breakpoints,
11755 auto-displays, and convenience variables, and to clear the value
11756 history. (This is necessary in order to preserve the integrity of
11757 debugger's data structures that reference the target system's symbol
11760 @node VxWorks Attach
11761 @subsubsection Running tasks
11763 @cindex running VxWorks tasks
11764 You can also attach to an existing task using the @code{attach} command as
11768 (vxgdb) attach @var{task}
11772 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11773 or suspended when you attach to it. Running tasks are suspended at
11774 the time of attachment.
11776 @node Embedded Processors
11777 @section Embedded Processors
11779 This section goes into details specific to particular embedded
11785 * H8/300:: Renesas H8/300
11786 * H8/500:: Renesas H8/500
11787 * M32R/D:: Renesas M32R/D
11788 * M68K:: Motorola M68K
11789 * MIPS Embedded:: MIPS Embedded
11790 * OpenRISC 1000:: OpenRisc 1000
11791 * PA:: HP PA Embedded
11794 * Sparclet:: Tsqware Sparclet
11795 * Sparclite:: Fujitsu Sparclite
11796 * ST2000:: Tandem ST2000
11797 * Z8000:: Zilog Z8000
11806 @item target rdi @var{dev}
11807 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11808 use this target to communicate with both boards running the Angel
11809 monitor, or with the EmbeddedICE JTAG debug device.
11812 @item target rdp @var{dev}
11818 @subsection Renesas H8/300
11822 @kindex target hms@r{, with H8/300}
11823 @item target hms @var{dev}
11824 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
11825 Use special commands @code{device} and @code{speed} to control the serial
11826 line and the communications speed used.
11828 @kindex target e7000@r{, with H8/300}
11829 @item target e7000 @var{dev}
11830 E7000 emulator for Renesas H8 and SH.
11832 @kindex target sh3@r{, with H8/300}
11833 @kindex target sh3e@r{, with H8/300}
11834 @item target sh3 @var{dev}
11835 @itemx target sh3e @var{dev}
11836 Renesas SH-3 and SH-3E target systems.
11840 @cindex download to H8/300 or H8/500
11841 @cindex H8/300 or H8/500 download
11842 @cindex download to Renesas SH
11843 @cindex Renesas SH download
11844 When you select remote debugging to a Renesas SH, H8/300, or H8/500
11845 board, the @code{load} command downloads your program to the Renesas
11846 board and also opens it as the current executable target for
11847 @value{GDBN} on your host (like the @code{file} command).
11849 @value{GDBN} needs to know these things to talk to your
11850 Renesas SH, H8/300, or H8/500:
11854 that you want to use @samp{target hms}, the remote debugging interface
11855 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
11856 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
11857 the default when @value{GDBN} is configured specifically for the Renesas SH,
11858 H8/300, or H8/500.)
11861 what serial device connects your host to your Renesas board (the first
11862 serial device available on your host is the default).
11865 what speed to use over the serial device.
11869 * Renesas Boards:: Connecting to Renesas boards.
11870 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
11871 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
11874 @node Renesas Boards
11875 @subsubsection Connecting to Renesas boards
11877 @c only for Unix hosts
11879 @cindex serial device, Renesas micros
11880 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11881 need to explicitly set the serial device. The default @var{port} is the
11882 first available port on your host. This is only necessary on Unix
11883 hosts, where it is typically something like @file{/dev/ttya}.
11886 @cindex serial line speed, Renesas micros
11887 @code{@value{GDBN}} has another special command to set the communications
11888 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11889 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11890 the DOS @code{mode} command (for instance,
11891 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11893 The @samp{device} and @samp{speed} commands are available only when you
11894 use a Unix host to debug your Renesas microprocessor programs. If you
11896 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11897 called @code{asynctsr} to communicate with the development board
11898 through a PC serial port. You must also use the DOS @code{mode} command
11899 to set up the serial port on the DOS side.
11901 The following sample session illustrates the steps needed to start a
11902 program under @value{GDBN} control on an H8/300. The example uses a
11903 sample H8/300 program called @file{t.x}. The procedure is the same for
11904 the Renesas SH and the H8/500.
11906 First hook up your development board. In this example, we use a
11907 board attached to serial port @code{COM2}; if you use a different serial
11908 port, substitute its name in the argument of the @code{mode} command.
11909 When you call @code{asynctsr}, the auxiliary comms program used by the
11910 debugger, you give it just the numeric part of the serial port's name;
11911 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11915 C:\H8300\TEST> asynctsr 2
11916 C:\H8300\TEST> mode com2:9600,n,8,1,p
11918 Resident portion of MODE loaded
11920 COM2: 9600, n, 8, 1, p
11925 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11926 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11927 disable it, or even boot without it, to use @code{asynctsr} to control
11928 your development board.
11931 @kindex target hms@r{, and serial protocol}
11932 Now that serial communications are set up, and the development board is
11933 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11934 the name of your program as the argument. @code{@value{GDBN}} prompts
11935 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11936 commands to begin your debugging session: @samp{target hms} to specify
11937 cross-debugging to the Renesas board, and the @code{load} command to
11938 download your program to the board. @code{load} displays the names of
11939 the program's sections, and a @samp{*} for each 2K of data downloaded.
11940 (If you want to refresh @value{GDBN} data on symbols or on the
11941 executable file without downloading, use the @value{GDBN} commands
11942 @code{file} or @code{symbol-file}. These commands, and @code{load}
11943 itself, are described in @ref{Files,,Commands to specify files}.)
11946 (eg-C:\H8300\TEST) @value{GDBP} t.x
11947 @value{GDBN} is free software and you are welcome to distribute copies
11948 of it under certain conditions; type "show copying" to see
11950 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11952 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11953 (@value{GDBP}) target hms
11954 Connected to remote H8/300 HMS system.
11955 (@value{GDBP}) load t.x
11956 .text : 0x8000 .. 0xabde ***********
11957 .data : 0xabde .. 0xad30 *
11958 .stack : 0xf000 .. 0xf014 *
11961 At this point, you're ready to run or debug your program. From here on,
11962 you can use all the usual @value{GDBN} commands. The @code{break} command
11963 sets breakpoints; the @code{run} command starts your program;
11964 @code{print} or @code{x} display data; the @code{continue} command
11965 resumes execution after stopping at a breakpoint. You can use the
11966 @code{help} command at any time to find out more about @value{GDBN} commands.
11968 Remember, however, that @emph{operating system} facilities aren't
11969 available on your development board; for example, if your program hangs,
11970 you can't send an interrupt---but you can press the @sc{reset} switch!
11972 Use the @sc{reset} button on the development board
11975 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11976 no way to pass an interrupt signal to the development board); and
11979 to return to the @value{GDBN} command prompt after your program finishes
11980 normally. The communications protocol provides no other way for @value{GDBN}
11981 to detect program completion.
11984 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11985 development board as a ``normal exit'' of your program.
11988 @subsubsection Using the E7000 in-circuit emulator
11990 @kindex target e7000@r{, with Renesas ICE}
11991 You can use the E7000 in-circuit emulator to develop code for either the
11992 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
11993 e7000} command to connect @value{GDBN} to your E7000:
11996 @item target e7000 @var{port} @var{speed}
11997 Use this form if your E7000 is connected to a serial port. The
11998 @var{port} argument identifies what serial port to use (for example,
11999 @samp{com2}). The third argument is the line speed in bits per second
12000 (for example, @samp{9600}).
12002 @item target e7000 @var{hostname}
12003 If your E7000 is installed as a host on a TCP/IP network, you can just
12004 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12007 @node Renesas Special
12008 @subsubsection Special @value{GDBN} commands for Renesas micros
12010 Some @value{GDBN} commands are available only for the H8/300:
12014 @kindex set machine
12015 @kindex show machine
12016 @item set machine h8300
12017 @itemx set machine h8300h
12018 Condition @value{GDBN} for one of the two variants of the H8/300
12019 architecture with @samp{set machine}. You can use @samp{show machine}
12020 to check which variant is currently in effect.
12029 @kindex set memory @var{mod}
12030 @cindex memory models, H8/500
12031 @item set memory @var{mod}
12033 Specify which H8/500 memory model (@var{mod}) you are using with
12034 @samp{set memory}; check which memory model is in effect with @samp{show
12035 memory}. The accepted values for @var{mod} are @code{small},
12036 @code{big}, @code{medium}, and @code{compact}.
12041 @subsection Renesas M32R/D
12045 @kindex target m32r
12046 @item target m32r @var{dev}
12047 Renesas M32R/D ROM monitor.
12054 The Motorola m68k configuration includes ColdFire support, and
12055 target command for the following ROM monitors.
12059 @kindex target abug
12060 @item target abug @var{dev}
12061 ABug ROM monitor for M68K.
12063 @kindex target cpu32bug
12064 @item target cpu32bug @var{dev}
12065 CPU32BUG monitor, running on a CPU32 (M68K) board.
12067 @kindex target dbug
12068 @item target dbug @var{dev}
12069 dBUG ROM monitor for Motorola ColdFire.
12072 @item target est @var{dev}
12073 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12075 @kindex target rom68k
12076 @item target rom68k @var{dev}
12077 ROM 68K monitor, running on an M68K IDP board.
12083 @kindex target rombug
12084 @item target rombug @var{dev}
12085 ROMBUG ROM monitor for OS/9000.
12089 @node MIPS Embedded
12090 @subsection MIPS Embedded
12092 @cindex MIPS boards
12093 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12094 MIPS board attached to a serial line. This is available when
12095 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12098 Use these @value{GDBN} commands to specify the connection to your target board:
12101 @item target mips @var{port}
12102 @kindex target mips @var{port}
12103 To run a program on the board, start up @code{@value{GDBP}} with the
12104 name of your program as the argument. To connect to the board, use the
12105 command @samp{target mips @var{port}}, where @var{port} is the name of
12106 the serial port connected to the board. If the program has not already
12107 been downloaded to the board, you may use the @code{load} command to
12108 download it. You can then use all the usual @value{GDBN} commands.
12110 For example, this sequence connects to the target board through a serial
12111 port, and loads and runs a program called @var{prog} through the
12115 host$ @value{GDBP} @var{prog}
12116 @value{GDBN} is free software and @dots{}
12117 (@value{GDBP}) target mips /dev/ttyb
12118 (@value{GDBP}) load @var{prog}
12122 @item target mips @var{hostname}:@var{portnumber}
12123 On some @value{GDBN} host configurations, you can specify a TCP
12124 connection (for instance, to a serial line managed by a terminal
12125 concentrator) instead of a serial port, using the syntax
12126 @samp{@var{hostname}:@var{portnumber}}.
12128 @item target pmon @var{port}
12129 @kindex target pmon @var{port}
12132 @item target ddb @var{port}
12133 @kindex target ddb @var{port}
12134 NEC's DDB variant of PMON for Vr4300.
12136 @item target lsi @var{port}
12137 @kindex target lsi @var{port}
12138 LSI variant of PMON.
12140 @kindex target r3900
12141 @item target r3900 @var{dev}
12142 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12144 @kindex target array
12145 @item target array @var{dev}
12146 Array Tech LSI33K RAID controller board.
12152 @value{GDBN} also supports these special commands for MIPS targets:
12155 @item set processor @var{args}
12156 @itemx show processor
12157 @kindex set processor @var{args}
12158 @kindex show processor
12159 Use the @code{set processor} command to set the type of MIPS
12160 processor when you want to access processor-type-specific registers.
12161 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12162 to use the CPU registers appropriate for the 3041 chip.
12163 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12164 is using. Use the @code{info reg} command to see what registers
12165 @value{GDBN} is using.
12167 @item set mipsfpu double
12168 @itemx set mipsfpu single
12169 @itemx set mipsfpu none
12170 @itemx show mipsfpu
12171 @kindex set mipsfpu
12172 @kindex show mipsfpu
12173 @cindex MIPS remote floating point
12174 @cindex floating point, MIPS remote
12175 If your target board does not support the MIPS floating point
12176 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12177 need this, you may wish to put the command in your @value{GDBN} init
12178 file). This tells @value{GDBN} how to find the return value of
12179 functions which return floating point values. It also allows
12180 @value{GDBN} to avoid saving the floating point registers when calling
12181 functions on the board. If you are using a floating point coprocessor
12182 with only single precision floating point support, as on the @sc{r4650}
12183 processor, use the command @samp{set mipsfpu single}. The default
12184 double precision floating point coprocessor may be selected using
12185 @samp{set mipsfpu double}.
12187 In previous versions the only choices were double precision or no
12188 floating point, so @samp{set mipsfpu on} will select double precision
12189 and @samp{set mipsfpu off} will select no floating point.
12191 As usual, you can inquire about the @code{mipsfpu} variable with
12192 @samp{show mipsfpu}.
12194 @item set remotedebug @var{n}
12195 @itemx show remotedebug
12196 @kindex set remotedebug@r{, MIPS protocol}
12197 @kindex show remotedebug@r{, MIPS protocol}
12198 @cindex @code{remotedebug}, MIPS protocol
12199 @cindex MIPS @code{remotedebug} protocol
12200 @c FIXME! For this to be useful, you must know something about the MIPS
12201 @c FIXME...protocol. Where is it described?
12202 You can see some debugging information about communications with the board
12203 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12204 @samp{set remotedebug 1}, every packet is displayed. If you set it
12205 to @code{2}, every character is displayed. You can check the current value
12206 at any time with the command @samp{show remotedebug}.
12208 @item set timeout @var{seconds}
12209 @itemx set retransmit-timeout @var{seconds}
12210 @itemx show timeout
12211 @itemx show retransmit-timeout
12212 @cindex @code{timeout}, MIPS protocol
12213 @cindex @code{retransmit-timeout}, MIPS protocol
12214 @kindex set timeout
12215 @kindex show timeout
12216 @kindex set retransmit-timeout
12217 @kindex show retransmit-timeout
12218 You can control the timeout used while waiting for a packet, in the MIPS
12219 remote protocol, with the @code{set timeout @var{seconds}} command. The
12220 default is 5 seconds. Similarly, you can control the timeout used while
12221 waiting for an acknowledgement of a packet with the @code{set
12222 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12223 You can inspect both values with @code{show timeout} and @code{show
12224 retransmit-timeout}. (These commands are @emph{only} available when
12225 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12227 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12228 is waiting for your program to stop. In that case, @value{GDBN} waits
12229 forever because it has no way of knowing how long the program is going
12230 to run before stopping.
12233 @node OpenRISC 1000
12234 @subsection OpenRISC 1000
12235 @cindex OpenRISC 1000
12237 @cindex or1k boards
12238 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12239 about platform and commands.
12243 @kindex target jtag
12244 @item target jtag jtag://@var{host}:@var{port}
12246 Connects to remote JTAG server.
12247 JTAG remote server can be either an or1ksim or JTAG server,
12248 connected via parallel port to the board.
12250 Example: @code{target jtag jtag://localhost:9999}
12253 @item or1ksim @var{command}
12254 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12255 Simulator, proprietary commands can be executed.
12257 @kindex info or1k spr
12258 @item info or1k spr
12259 Displays spr groups.
12261 @item info or1k spr @var{group}
12262 @itemx info or1k spr @var{groupno}
12263 Displays register names in selected group.
12265 @item info or1k spr @var{group} @var{register}
12266 @itemx info or1k spr @var{register}
12267 @itemx info or1k spr @var{groupno} @var{registerno}
12268 @itemx info or1k spr @var{registerno}
12269 Shows information about specified spr register.
12272 @item spr @var{group} @var{register} @var{value}
12273 @itemx spr @var{register @var{value}}
12274 @itemx spr @var{groupno} @var{registerno @var{value}}
12275 @itemx spr @var{registerno @var{value}}
12276 Writes @var{value} to specified spr register.
12279 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12280 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12281 program execution and is thus much faster. Hardware breakpoints/watchpoint
12282 triggers can be set using:
12285 Load effective address/data
12287 Store effective address/data
12289 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12294 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12295 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12297 @code{htrace} commands:
12298 @cindex OpenRISC 1000 htrace
12301 @item hwatch @var{conditional}
12302 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12303 or Data. For example:
12305 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12307 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12309 @kindex htrace info
12311 Display information about current HW trace configuration.
12313 @kindex htrace trigger
12314 @item htrace trigger @var{conditional}
12315 Set starting criteria for HW trace.
12317 @kindex htrace qualifier
12318 @item htrace qualifier @var{conditional}
12319 Set acquisition qualifier for HW trace.
12321 @kindex htrace stop
12322 @item htrace stop @var{conditional}
12323 Set HW trace stopping criteria.
12325 @kindex htrace record
12326 @item htrace record [@var{data}]*
12327 Selects the data to be recorded, when qualifier is met and HW trace was
12330 @kindex htrace enable
12331 @item htrace enable
12332 @kindex htrace disable
12333 @itemx htrace disable
12334 Enables/disables the HW trace.
12336 @kindex htrace rewind
12337 @item htrace rewind [@var{filename}]
12338 Clears currently recorded trace data.
12340 If filename is specified, new trace file is made and any newly collected data
12341 will be written there.
12343 @kindex htrace print
12344 @item htrace print [@var{start} [@var{len}]]
12345 Prints trace buffer, using current record configuration.
12347 @kindex htrace mode continuous
12348 @item htrace mode continuous
12349 Set continuous trace mode.
12351 @kindex htrace mode suspend
12352 @item htrace mode suspend
12353 Set suspend trace mode.
12358 @subsection PowerPC
12362 @kindex target dink32
12363 @item target dink32 @var{dev}
12364 DINK32 ROM monitor.
12366 @kindex target ppcbug
12367 @item target ppcbug @var{dev}
12368 @kindex target ppcbug1
12369 @item target ppcbug1 @var{dev}
12370 PPCBUG ROM monitor for PowerPC.
12373 @item target sds @var{dev}
12374 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12379 @subsection HP PA Embedded
12383 @kindex target op50n
12384 @item target op50n @var{dev}
12385 OP50N monitor, running on an OKI HPPA board.
12387 @kindex target w89k
12388 @item target w89k @var{dev}
12389 W89K monitor, running on a Winbond HPPA board.
12394 @subsection Renesas SH
12398 @kindex target hms@r{, with Renesas SH}
12399 @item target hms @var{dev}
12400 A Renesas SH board attached via serial line to your host. Use special
12401 commands @code{device} and @code{speed} to control the serial line and
12402 the communications speed used.
12404 @kindex target e7000@r{, with Renesas SH}
12405 @item target e7000 @var{dev}
12406 E7000 emulator for Renesas SH.
12408 @kindex target sh3@r{, with SH}
12409 @kindex target sh3e@r{, with SH}
12410 @item target sh3 @var{dev}
12411 @item target sh3e @var{dev}
12412 Renesas SH-3 and SH-3E target systems.
12417 @subsection Tsqware Sparclet
12421 @value{GDBN} enables developers to debug tasks running on
12422 Sparclet targets from a Unix host.
12423 @value{GDBN} uses code that runs on
12424 both the Unix host and on the Sparclet target. The program
12425 @code{@value{GDBP}} is installed and executed on the Unix host.
12428 @item remotetimeout @var{args}
12429 @kindex remotetimeout
12430 @value{GDBN} supports the option @code{remotetimeout}.
12431 This option is set by the user, and @var{args} represents the number of
12432 seconds @value{GDBN} waits for responses.
12435 @cindex compiling, on Sparclet
12436 When compiling for debugging, include the options @samp{-g} to get debug
12437 information and @samp{-Ttext} to relocate the program to where you wish to
12438 load it on the target. You may also want to add the options @samp{-n} or
12439 @samp{-N} in order to reduce the size of the sections. Example:
12442 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12445 You can use @code{objdump} to verify that the addresses are what you intended:
12448 sparclet-aout-objdump --headers --syms prog
12451 @cindex running, on Sparclet
12453 your Unix execution search path to find @value{GDBN}, you are ready to
12454 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12455 (or @code{sparclet-aout-gdb}, depending on your installation).
12457 @value{GDBN} comes up showing the prompt:
12464 * Sparclet File:: Setting the file to debug
12465 * Sparclet Connection:: Connecting to Sparclet
12466 * Sparclet Download:: Sparclet download
12467 * Sparclet Execution:: Running and debugging
12470 @node Sparclet File
12471 @subsubsection Setting file to debug
12473 The @value{GDBN} command @code{file} lets you choose with program to debug.
12476 (gdbslet) file prog
12480 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12481 @value{GDBN} locates
12482 the file by searching the directories listed in the command search
12484 If the file was compiled with debug information (option "-g"), source
12485 files will be searched as well.
12486 @value{GDBN} locates
12487 the source files by searching the directories listed in the directory search
12488 path (@pxref{Environment, ,Your program's environment}).
12490 to find a file, it displays a message such as:
12493 prog: No such file or directory.
12496 When this happens, add the appropriate directories to the search paths with
12497 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12498 @code{target} command again.
12500 @node Sparclet Connection
12501 @subsubsection Connecting to Sparclet
12503 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12504 To connect to a target on serial port ``@code{ttya}'', type:
12507 (gdbslet) target sparclet /dev/ttya
12508 Remote target sparclet connected to /dev/ttya
12509 main () at ../prog.c:3
12513 @value{GDBN} displays messages like these:
12519 @node Sparclet Download
12520 @subsubsection Sparclet download
12522 @cindex download to Sparclet
12523 Once connected to the Sparclet target,
12524 you can use the @value{GDBN}
12525 @code{load} command to download the file from the host to the target.
12526 The file name and load offset should be given as arguments to the @code{load}
12528 Since the file format is aout, the program must be loaded to the starting
12529 address. You can use @code{objdump} to find out what this value is. The load
12530 offset is an offset which is added to the VMA (virtual memory address)
12531 of each of the file's sections.
12532 For instance, if the program
12533 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12534 and bss at 0x12010170, in @value{GDBN}, type:
12537 (gdbslet) load prog 0x12010000
12538 Loading section .text, size 0xdb0 vma 0x12010000
12541 If the code is loaded at a different address then what the program was linked
12542 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12543 to tell @value{GDBN} where to map the symbol table.
12545 @node Sparclet Execution
12546 @subsubsection Running and debugging
12548 @cindex running and debugging Sparclet programs
12549 You can now begin debugging the task using @value{GDBN}'s execution control
12550 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12551 manual for the list of commands.
12555 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12557 Starting program: prog
12558 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12559 3 char *symarg = 0;
12561 4 char *execarg = "hello!";
12566 @subsection Fujitsu Sparclite
12570 @kindex target sparclite
12571 @item target sparclite @var{dev}
12572 Fujitsu sparclite boards, used only for the purpose of loading.
12573 You must use an additional command to debug the program.
12574 For example: target remote @var{dev} using @value{GDBN} standard
12580 @subsection Tandem ST2000
12582 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12585 To connect your ST2000 to the host system, see the manufacturer's
12586 manual. Once the ST2000 is physically attached, you can run:
12589 target st2000 @var{dev} @var{speed}
12593 to establish it as your debugging environment. @var{dev} is normally
12594 the name of a serial device, such as @file{/dev/ttya}, connected to the
12595 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12596 connection (for example, to a serial line attached via a terminal
12597 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12599 The @code{load} and @code{attach} commands are @emph{not} defined for
12600 this target; you must load your program into the ST2000 as you normally
12601 would for standalone operation. @value{GDBN} reads debugging information
12602 (such as symbols) from a separate, debugging version of the program
12603 available on your host computer.
12604 @c FIXME!! This is terribly vague; what little content is here is
12605 @c basically hearsay.
12607 @cindex ST2000 auxiliary commands
12608 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12612 @item st2000 @var{command}
12613 @kindex st2000 @var{cmd}
12614 @cindex STDBUG commands (ST2000)
12615 @cindex commands to STDBUG (ST2000)
12616 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12617 manual for available commands.
12620 @cindex connect (to STDBUG)
12621 Connect the controlling terminal to the STDBUG command monitor. When
12622 you are done interacting with STDBUG, typing either of two character
12623 sequences gets you back to the @value{GDBN} command prompt:
12624 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12625 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12629 @subsection Zilog Z8000
12632 @cindex simulator, Z8000
12633 @cindex Zilog Z8000 simulator
12635 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12638 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12639 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12640 segmented variant). The simulator recognizes which architecture is
12641 appropriate by inspecting the object code.
12644 @item target sim @var{args}
12646 @kindex target sim@r{, with Z8000}
12647 Debug programs on a simulated CPU. If the simulator supports setup
12648 options, specify them via @var{args}.
12652 After specifying this target, you can debug programs for the simulated
12653 CPU in the same style as programs for your host computer; use the
12654 @code{file} command to load a new program image, the @code{run} command
12655 to run your program, and so on.
12657 As well as making available all the usual machine registers
12658 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12659 additional items of information as specially named registers:
12664 Counts clock-ticks in the simulator.
12667 Counts instructions run in the simulator.
12670 Execution time in 60ths of a second.
12674 You can refer to these values in @value{GDBN} expressions with the usual
12675 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12676 conditional breakpoint that suspends only after at least 5000
12677 simulated clock ticks.
12679 @node Architectures
12680 @section Architectures
12682 This section describes characteristics of architectures that affect
12683 all uses of @value{GDBN} with the architecture, both native and cross.
12696 @kindex set rstack_high_address
12697 @cindex AMD 29K register stack
12698 @cindex register stack, AMD29K
12699 @item set rstack_high_address @var{address}
12700 On AMD 29000 family processors, registers are saved in a separate
12701 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12702 extent of this stack. Normally, @value{GDBN} just assumes that the
12703 stack is ``large enough''. This may result in @value{GDBN} referencing
12704 memory locations that do not exist. If necessary, you can get around
12705 this problem by specifying the ending address of the register stack with
12706 the @code{set rstack_high_address} command. The argument should be an
12707 address, which you probably want to precede with @samp{0x} to specify in
12710 @kindex show rstack_high_address
12711 @item show rstack_high_address
12712 Display the current limit of the register stack, on AMD 29000 family
12720 See the following section.
12725 @cindex stack on Alpha
12726 @cindex stack on MIPS
12727 @cindex Alpha stack
12729 Alpha- and MIPS-based computers use an unusual stack frame, which
12730 sometimes requires @value{GDBN} to search backward in the object code to
12731 find the beginning of a function.
12733 @cindex response time, MIPS debugging
12734 To improve response time (especially for embedded applications, where
12735 @value{GDBN} may be restricted to a slow serial line for this search)
12736 you may want to limit the size of this search, using one of these
12740 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12741 @item set heuristic-fence-post @var{limit}
12742 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12743 search for the beginning of a function. A value of @var{0} (the
12744 default) means there is no limit. However, except for @var{0}, the
12745 larger the limit the more bytes @code{heuristic-fence-post} must search
12746 and therefore the longer it takes to run.
12748 @item show heuristic-fence-post
12749 Display the current limit.
12753 These commands are available @emph{only} when @value{GDBN} is configured
12754 for debugging programs on Alpha or MIPS processors.
12757 @node Controlling GDB
12758 @chapter Controlling @value{GDBN}
12760 You can alter the way @value{GDBN} interacts with you by using the
12761 @code{set} command. For commands controlling how @value{GDBN} displays
12762 data, see @ref{Print Settings, ,Print settings}. Other settings are
12767 * Editing:: Command editing
12768 * History:: Command history
12769 * Screen Size:: Screen size
12770 * Numbers:: Numbers
12771 * ABI:: Configuring the current ABI
12772 * Messages/Warnings:: Optional warnings and messages
12773 * Debugging Output:: Optional messages about internal happenings
12781 @value{GDBN} indicates its readiness to read a command by printing a string
12782 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12783 can change the prompt string with the @code{set prompt} command. For
12784 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12785 the prompt in one of the @value{GDBN} sessions so that you can always tell
12786 which one you are talking to.
12788 @emph{Note:} @code{set prompt} does not add a space for you after the
12789 prompt you set. This allows you to set a prompt which ends in a space
12790 or a prompt that does not.
12794 @item set prompt @var{newprompt}
12795 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12797 @kindex show prompt
12799 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12803 @section Command editing
12805 @cindex command line editing
12807 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12808 @sc{gnu} library provides consistent behavior for programs which provide a
12809 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12810 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12811 substitution, and a storage and recall of command history across
12812 debugging sessions.
12814 You may control the behavior of command line editing in @value{GDBN} with the
12815 command @code{set}.
12818 @kindex set editing
12821 @itemx set editing on
12822 Enable command line editing (enabled by default).
12824 @item set editing off
12825 Disable command line editing.
12827 @kindex show editing
12829 Show whether command line editing is enabled.
12833 @section Command history
12835 @value{GDBN} can keep track of the commands you type during your
12836 debugging sessions, so that you can be certain of precisely what
12837 happened. Use these commands to manage the @value{GDBN} command
12841 @cindex history substitution
12842 @cindex history file
12843 @kindex set history filename
12844 @kindex GDBHISTFILE
12845 @item set history filename @var{fname}
12846 Set the name of the @value{GDBN} command history file to @var{fname}.
12847 This is the file where @value{GDBN} reads an initial command history
12848 list, and where it writes the command history from this session when it
12849 exits. You can access this list through history expansion or through
12850 the history command editing characters listed below. This file defaults
12851 to the value of the environment variable @code{GDBHISTFILE}, or to
12852 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12855 @cindex history save
12856 @kindex set history save
12857 @item set history save
12858 @itemx set history save on
12859 Record command history in a file, whose name may be specified with the
12860 @code{set history filename} command. By default, this option is disabled.
12862 @item set history save off
12863 Stop recording command history in a file.
12865 @cindex history size
12866 @kindex set history size
12867 @item set history size @var{size}
12868 Set the number of commands which @value{GDBN} keeps in its history list.
12869 This defaults to the value of the environment variable
12870 @code{HISTSIZE}, or to 256 if this variable is not set.
12873 @cindex history expansion
12874 History expansion assigns special meaning to the character @kbd{!}.
12875 @ifset have-readline-appendices
12876 @xref{Event Designators}.
12879 Since @kbd{!} is also the logical not operator in C, history expansion
12880 is off by default. If you decide to enable history expansion with the
12881 @code{set history expansion on} command, you may sometimes need to
12882 follow @kbd{!} (when it is used as logical not, in an expression) with
12883 a space or a tab to prevent it from being expanded. The readline
12884 history facilities do not attempt substitution on the strings
12885 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12887 The commands to control history expansion are:
12890 @kindex set history expansion
12891 @item set history expansion on
12892 @itemx set history expansion
12893 Enable history expansion. History expansion is off by default.
12895 @item set history expansion off
12896 Disable history expansion.
12898 The readline code comes with more complete documentation of
12899 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12900 or @code{vi} may wish to read it.
12901 @ifset have-readline-appendices
12902 @xref{Command Line Editing}.
12906 @kindex show history
12908 @itemx show history filename
12909 @itemx show history save
12910 @itemx show history size
12911 @itemx show history expansion
12912 These commands display the state of the @value{GDBN} history parameters.
12913 @code{show history} by itself displays all four states.
12919 @item show commands
12920 Display the last ten commands in the command history.
12922 @item show commands @var{n}
12923 Print ten commands centered on command number @var{n}.
12925 @item show commands +
12926 Print ten commands just after the commands last printed.
12930 @section Screen size
12931 @cindex size of screen
12932 @cindex pauses in output
12934 Certain commands to @value{GDBN} may produce large amounts of
12935 information output to the screen. To help you read all of it,
12936 @value{GDBN} pauses and asks you for input at the end of each page of
12937 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12938 to discard the remaining output. Also, the screen width setting
12939 determines when to wrap lines of output. Depending on what is being
12940 printed, @value{GDBN} tries to break the line at a readable place,
12941 rather than simply letting it overflow onto the following line.
12943 Normally @value{GDBN} knows the size of the screen from the terminal
12944 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12945 together with the value of the @code{TERM} environment variable and the
12946 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12947 you can override it with the @code{set height} and @code{set
12954 @kindex show height
12955 @item set height @var{lpp}
12957 @itemx set width @var{cpl}
12959 These @code{set} commands specify a screen height of @var{lpp} lines and
12960 a screen width of @var{cpl} characters. The associated @code{show}
12961 commands display the current settings.
12963 If you specify a height of zero lines, @value{GDBN} does not pause during
12964 output no matter how long the output is. This is useful if output is to a
12965 file or to an editor buffer.
12967 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12968 from wrapping its output.
12973 @cindex number representation
12974 @cindex entering numbers
12976 You can always enter numbers in octal, decimal, or hexadecimal in
12977 @value{GDBN} by the usual conventions: octal numbers begin with
12978 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12979 begin with @samp{0x}. Numbers that begin with none of these are, by
12980 default, entered in base 10; likewise, the default display for
12981 numbers---when no particular format is specified---is base 10. You can
12982 change the default base for both input and output with the @code{set
12986 @kindex set input-radix
12987 @item set input-radix @var{base}
12988 Set the default base for numeric input. Supported choices
12989 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12990 specified either unambiguously or using the current default radix; for
13000 sets the base to decimal. On the other hand, @samp{set radix 10}
13001 leaves the radix unchanged no matter what it was.
13003 @kindex set output-radix
13004 @item set output-radix @var{base}
13005 Set the default base for numeric display. Supported choices
13006 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13007 specified either unambiguously or using the current default radix.
13009 @kindex show input-radix
13010 @item show input-radix
13011 Display the current default base for numeric input.
13013 @kindex show output-radix
13014 @item show output-radix
13015 Display the current default base for numeric display.
13019 @section Configuring the current ABI
13021 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13022 application automatically. However, sometimes you need to override its
13023 conclusions. Use these commands to manage @value{GDBN}'s view of the
13030 One @value{GDBN} configuration can debug binaries for multiple operating
13031 system targets, either via remote debugging or native emulation.
13032 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13033 but you can override its conclusion using the @code{set osabi} command.
13034 One example where this is useful is in debugging of binaries which use
13035 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13036 not have the same identifying marks that the standard C library for your
13041 Show the OS ABI currently in use.
13044 With no argument, show the list of registered available OS ABI's.
13046 @item set osabi @var{abi}
13047 Set the current OS ABI to @var{abi}.
13050 @cindex float promotion
13051 @kindex set coerce-float-to-double
13053 Generally, the way that an argument of type @code{float} is passed to a
13054 function depends on whether the function is prototyped. For a prototyped
13055 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13056 according to the architecture's convention for @code{float}. For unprototyped
13057 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13058 @code{double} and then passed.
13060 Unfortunately, some forms of debug information do not reliably indicate whether
13061 a function is prototyped. If @value{GDBN} calls a function that is not marked
13062 as prototyped, it consults @kbd{set coerce-float-to-double}.
13065 @item set coerce-float-to-double
13066 @itemx set coerce-float-to-double on
13067 Arguments of type @code{float} will be promoted to @code{double} when passed
13068 to an unprototyped function. This is the default setting.
13070 @item set coerce-float-to-double off
13071 Arguments of type @code{float} will be passed directly to unprototyped
13076 @kindex show cp-abi
13077 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13078 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13079 used to build your application. @value{GDBN} only fully supports
13080 programs with a single C@t{++} ABI; if your program contains code using
13081 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13082 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13083 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13084 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13085 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13086 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13091 Show the C@t{++} ABI currently in use.
13094 With no argument, show the list of supported C@t{++} ABI's.
13096 @item set cp-abi @var{abi}
13097 @itemx set cp-abi auto
13098 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13101 @node Messages/Warnings
13102 @section Optional warnings and messages
13104 By default, @value{GDBN} is silent about its inner workings. If you are
13105 running on a slow machine, you may want to use the @code{set verbose}
13106 command. This makes @value{GDBN} tell you when it does a lengthy
13107 internal operation, so you will not think it has crashed.
13109 Currently, the messages controlled by @code{set verbose} are those
13110 which announce that the symbol table for a source file is being read;
13111 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13114 @kindex set verbose
13115 @item set verbose on
13116 Enables @value{GDBN} output of certain informational messages.
13118 @item set verbose off
13119 Disables @value{GDBN} output of certain informational messages.
13121 @kindex show verbose
13123 Displays whether @code{set verbose} is on or off.
13126 By default, if @value{GDBN} encounters bugs in the symbol table of an
13127 object file, it is silent; but if you are debugging a compiler, you may
13128 find this information useful (@pxref{Symbol Errors, ,Errors reading
13133 @kindex set complaints
13134 @item set complaints @var{limit}
13135 Permits @value{GDBN} to output @var{limit} complaints about each type of
13136 unusual symbols before becoming silent about the problem. Set
13137 @var{limit} to zero to suppress all complaints; set it to a large number
13138 to prevent complaints from being suppressed.
13140 @kindex show complaints
13141 @item show complaints
13142 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13146 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13147 lot of stupid questions to confirm certain commands. For example, if
13148 you try to run a program which is already running:
13152 The program being debugged has been started already.
13153 Start it from the beginning? (y or n)
13156 If you are willing to unflinchingly face the consequences of your own
13157 commands, you can disable this ``feature'':
13161 @kindex set confirm
13163 @cindex confirmation
13164 @cindex stupid questions
13165 @item set confirm off
13166 Disables confirmation requests.
13168 @item set confirm on
13169 Enables confirmation requests (the default).
13171 @kindex show confirm
13173 Displays state of confirmation requests.
13177 @node Debugging Output
13178 @section Optional messages about internal happenings
13180 @kindex set debug arch
13181 @item set debug arch
13182 Turns on or off display of gdbarch debugging info. The default is off
13183 @kindex show debug arch
13184 @item show debug arch
13185 Displays the current state of displaying gdbarch debugging info.
13186 @kindex set debug event
13187 @item set debug event
13188 Turns on or off display of @value{GDBN} event debugging info. The
13190 @kindex show debug event
13191 @item show debug event
13192 Displays the current state of displaying @value{GDBN} event debugging
13194 @kindex set debug expression
13195 @item set debug expression
13196 Turns on or off display of @value{GDBN} expression debugging info. The
13198 @kindex show debug expression
13199 @item show debug expression
13200 Displays the current state of displaying @value{GDBN} expression
13202 @kindex set debug frame
13203 @item set debug frame
13204 Turns on or off display of @value{GDBN} frame debugging info. The
13206 @kindex show debug frame
13207 @item show debug frame
13208 Displays the current state of displaying @value{GDBN} frame debugging
13210 @kindex set debug overload
13211 @item set debug overload
13212 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13213 info. This includes info such as ranking of functions, etc. The default
13215 @kindex show debug overload
13216 @item show debug overload
13217 Displays the current state of displaying @value{GDBN} C@t{++} overload
13219 @kindex set debug remote
13220 @cindex packets, reporting on stdout
13221 @cindex serial connections, debugging
13222 @item set debug remote
13223 Turns on or off display of reports on all packets sent back and forth across
13224 the serial line to the remote machine. The info is printed on the
13225 @value{GDBN} standard output stream. The default is off.
13226 @kindex show debug remote
13227 @item show debug remote
13228 Displays the state of display of remote packets.
13229 @kindex set debug serial
13230 @item set debug serial
13231 Turns on or off display of @value{GDBN} serial debugging info. The
13233 @kindex show debug serial
13234 @item show debug serial
13235 Displays the current state of displaying @value{GDBN} serial debugging
13237 @kindex set debug target
13238 @item set debug target
13239 Turns on or off display of @value{GDBN} target debugging info. This info
13240 includes what is going on at the target level of GDB, as it happens. The
13242 @kindex show debug target
13243 @item show debug target
13244 Displays the current state of displaying @value{GDBN} target debugging
13246 @kindex set debug varobj
13247 @item set debug varobj
13248 Turns on or off display of @value{GDBN} variable object debugging
13249 info. The default is off.
13250 @kindex show debug varobj
13251 @item show debug varobj
13252 Displays the current state of displaying @value{GDBN} variable object
13257 @chapter Canned Sequences of Commands
13259 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13260 command lists}), @value{GDBN} provides two ways to store sequences of
13261 commands for execution as a unit: user-defined commands and command
13265 * Define:: User-defined commands
13266 * Hooks:: User-defined command hooks
13267 * Command Files:: Command files
13268 * Output:: Commands for controlled output
13272 @section User-defined commands
13274 @cindex user-defined command
13275 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13276 which you assign a new name as a command. This is done with the
13277 @code{define} command. User commands may accept up to 10 arguments
13278 separated by whitespace. Arguments are accessed within the user command
13279 via @var{$arg0@dots{}$arg9}. A trivial example:
13283 print $arg0 + $arg1 + $arg2
13287 To execute the command use:
13294 This defines the command @code{adder}, which prints the sum of
13295 its three arguments. Note the arguments are text substitutions, so they may
13296 reference variables, use complex expressions, or even perform inferior
13302 @item define @var{commandname}
13303 Define a command named @var{commandname}. If there is already a command
13304 by that name, you are asked to confirm that you want to redefine it.
13306 The definition of the command is made up of other @value{GDBN} command lines,
13307 which are given following the @code{define} command. The end of these
13308 commands is marked by a line containing @code{end}.
13313 Takes a single argument, which is an expression to evaluate.
13314 It is followed by a series of commands that are executed
13315 only if the expression is true (nonzero).
13316 There can then optionally be a line @code{else}, followed
13317 by a series of commands that are only executed if the expression
13318 was false. The end of the list is marked by a line containing @code{end}.
13322 The syntax is similar to @code{if}: the command takes a single argument,
13323 which is an expression to evaluate, and must be followed by the commands to
13324 execute, one per line, terminated by an @code{end}.
13325 The commands are executed repeatedly as long as the expression
13329 @item document @var{commandname}
13330 Document the user-defined command @var{commandname}, so that it can be
13331 accessed by @code{help}. The command @var{commandname} must already be
13332 defined. This command reads lines of documentation just as @code{define}
13333 reads the lines of the command definition, ending with @code{end}.
13334 After the @code{document} command is finished, @code{help} on command
13335 @var{commandname} displays the documentation you have written.
13337 You may use the @code{document} command again to change the
13338 documentation of a command. Redefining the command with @code{define}
13339 does not change the documentation.
13341 @kindex help user-defined
13342 @item help user-defined
13343 List all user-defined commands, with the first line of the documentation
13348 @itemx show user @var{commandname}
13349 Display the @value{GDBN} commands used to define @var{commandname} (but
13350 not its documentation). If no @var{commandname} is given, display the
13351 definitions for all user-defined commands.
13353 @kindex show max-user-call-depth
13354 @kindex set max-user-call-depth
13355 @item show max-user-call-depth
13356 @itemx set max-user-call-depth
13357 The value of @code{max-user-call-depth} controls how many recursion
13358 levels are allowed in user-defined commands before GDB suspects an
13359 infinite recursion and aborts the command.
13363 When user-defined commands are executed, the
13364 commands of the definition are not printed. An error in any command
13365 stops execution of the user-defined command.
13367 If used interactively, commands that would ask for confirmation proceed
13368 without asking when used inside a user-defined command. Many @value{GDBN}
13369 commands that normally print messages to say what they are doing omit the
13370 messages when used in a user-defined command.
13373 @section User-defined command hooks
13374 @cindex command hooks
13375 @cindex hooks, for commands
13376 @cindex hooks, pre-command
13380 You may define @dfn{hooks}, which are a special kind of user-defined
13381 command. Whenever you run the command @samp{foo}, if the user-defined
13382 command @samp{hook-foo} exists, it is executed (with no arguments)
13383 before that command.
13385 @cindex hooks, post-command
13388 A hook may also be defined which is run after the command you executed.
13389 Whenever you run the command @samp{foo}, if the user-defined command
13390 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13391 that command. Post-execution hooks may exist simultaneously with
13392 pre-execution hooks, for the same command.
13394 It is valid for a hook to call the command which it hooks. If this
13395 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13397 @c It would be nice if hookpost could be passed a parameter indicating
13398 @c if the command it hooks executed properly or not. FIXME!
13400 @kindex stop@r{, a pseudo-command}
13401 In addition, a pseudo-command, @samp{stop} exists. Defining
13402 (@samp{hook-stop}) makes the associated commands execute every time
13403 execution stops in your program: before breakpoint commands are run,
13404 displays are printed, or the stack frame is printed.
13406 For example, to ignore @code{SIGALRM} signals while
13407 single-stepping, but treat them normally during normal execution,
13412 handle SIGALRM nopass
13416 handle SIGALRM pass
13419 define hook-continue
13420 handle SIGLARM pass
13424 As a further example, to hook at the begining and end of the @code{echo}
13425 command, and to add extra text to the beginning and end of the message,
13433 define hookpost-echo
13437 (@value{GDBP}) echo Hello World
13438 <<<---Hello World--->>>
13443 You can define a hook for any single-word command in @value{GDBN}, but
13444 not for command aliases; you should define a hook for the basic command
13445 name, e.g. @code{backtrace} rather than @code{bt}.
13446 @c FIXME! So how does Joe User discover whether a command is an alias
13448 If an error occurs during the execution of your hook, execution of
13449 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13450 (before the command that you actually typed had a chance to run).
13452 If you try to define a hook which does not match any known command, you
13453 get a warning from the @code{define} command.
13455 @node Command Files
13456 @section Command files
13458 @cindex command files
13459 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13460 commands. Comments (lines starting with @kbd{#}) may also be included.
13461 An empty line in a command file does nothing; it does not mean to repeat
13462 the last command, as it would from the terminal.
13465 @cindex @file{.gdbinit}
13466 @cindex @file{gdb.ini}
13467 When you start @value{GDBN}, it automatically executes commands from its
13468 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13469 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13470 limitations of file names imposed by DOS filesystems.}.
13471 During startup, @value{GDBN} does the following:
13475 Reads the init file (if any) in your home directory@footnote{On
13476 DOS/Windows systems, the home directory is the one pointed to by the
13477 @code{HOME} environment variable.}.
13480 Processes command line options and operands.
13483 Reads the init file (if any) in the current working directory.
13486 Reads command files specified by the @samp{-x} option.
13489 The init file in your home directory can set options (such as @samp{set
13490 complaints}) that affect subsequent processing of command line options
13491 and operands. Init files are not executed if you use the @samp{-nx}
13492 option (@pxref{Mode Options, ,Choosing modes}).
13494 @cindex init file name
13495 On some configurations of @value{GDBN}, the init file is known by a
13496 different name (these are typically environments where a specialized
13497 form of @value{GDBN} may need to coexist with other forms, hence a
13498 different name for the specialized version's init file). These are the
13499 environments with special init file names:
13501 @cindex @file{.vxgdbinit}
13504 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13506 @cindex @file{.os68gdbinit}
13508 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13510 @cindex @file{.esgdbinit}
13512 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13515 You can also request the execution of a command file with the
13516 @code{source} command:
13520 @item source @var{filename}
13521 Execute the command file @var{filename}.
13524 The lines in a command file are executed sequentially. They are not
13525 printed as they are executed. An error in any command terminates
13526 execution of the command file and control is returned to the console.
13528 Commands that would ask for confirmation if used interactively proceed
13529 without asking when used in a command file. Many @value{GDBN} commands that
13530 normally print messages to say what they are doing omit the messages
13531 when called from command files.
13533 @value{GDBN} also accepts command input from standard input. In this
13534 mode, normal output goes to standard output and error output goes to
13535 standard error. Errors in a command file supplied on standard input do
13536 not terminate execution of the command file --- execution continues with
13540 gdb < cmds > log 2>&1
13543 (The syntax above will vary depending on the shell used.) This example
13544 will execute commands from the file @file{cmds}. All output and errors
13545 would be directed to @file{log}.
13548 @section Commands for controlled output
13550 During the execution of a command file or a user-defined command, normal
13551 @value{GDBN} output is suppressed; the only output that appears is what is
13552 explicitly printed by the commands in the definition. This section
13553 describes three commands useful for generating exactly the output you
13558 @item echo @var{text}
13559 @c I do not consider backslash-space a standard C escape sequence
13560 @c because it is not in ANSI.
13561 Print @var{text}. Nonprinting characters can be included in
13562 @var{text} using C escape sequences, such as @samp{\n} to print a
13563 newline. @strong{No newline is printed unless you specify one.}
13564 In addition to the standard C escape sequences, a backslash followed
13565 by a space stands for a space. This is useful for displaying a
13566 string with spaces at the beginning or the end, since leading and
13567 trailing spaces are otherwise trimmed from all arguments.
13568 To print @samp{@w{ }and foo =@w{ }}, use the command
13569 @samp{echo \@w{ }and foo = \@w{ }}.
13571 A backslash at the end of @var{text} can be used, as in C, to continue
13572 the command onto subsequent lines. For example,
13575 echo This is some text\n\
13576 which is continued\n\
13577 onto several lines.\n
13580 produces the same output as
13583 echo This is some text\n
13584 echo which is continued\n
13585 echo onto several lines.\n
13589 @item output @var{expression}
13590 Print the value of @var{expression} and nothing but that value: no
13591 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13592 value history either. @xref{Expressions, ,Expressions}, for more information
13595 @item output/@var{fmt} @var{expression}
13596 Print the value of @var{expression} in format @var{fmt}. You can use
13597 the same formats as for @code{print}. @xref{Output Formats,,Output
13598 formats}, for more information.
13601 @item printf @var{string}, @var{expressions}@dots{}
13602 Print the values of the @var{expressions} under the control of
13603 @var{string}. The @var{expressions} are separated by commas and may be
13604 either numbers or pointers. Their values are printed as specified by
13605 @var{string}, exactly as if your program were to execute the C
13607 @c FIXME: the above implies that at least all ANSI C formats are
13608 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13609 @c Either this is a bug, or the manual should document what formats are
13613 printf (@var{string}, @var{expressions}@dots{});
13616 For example, you can print two values in hex like this:
13619 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13622 The only backslash-escape sequences that you can use in the format
13623 string are the simple ones that consist of backslash followed by a
13628 @chapter Command Interpreters
13629 @cindex command interpreters
13631 @value{GDBN} supports multiple command interpreters, and some command
13632 infrastructure to allow users or user interface writers to switch
13633 between interpreters or run commands in other interpreters.
13635 @value{GDBN} currently supports two command interpreters, the console
13636 interpreter (sometimes called the command-line interpreter or @sc{cli})
13637 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13638 describes both of these interfaces in great detail.
13640 By default, @value{GDBN} will start with the console interpreter.
13641 However, the user may choose to start @value{GDBN} with another
13642 interpreter by specifying the @option{-i} or @option{--interpreter}
13643 startup options. Defined interpreters include:
13647 @cindex console interpreter
13648 The traditional console or command-line interpreter. This is the most often
13649 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13650 @value{GDBN} will use this interpreter.
13653 @cindex mi interpreter
13654 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13655 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13656 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13660 @cindex mi2 interpreter
13661 The current @sc{gdb/mi} interface.
13664 @cindex mi1 interpreter
13665 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13669 @cindex invoke another interpreter
13670 The interpreter being used by @value{GDBN} may not be dynamically
13671 switched at runtime. Although possible, this could lead to a very
13672 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13673 enters the command "interpreter-set console" in a console view,
13674 @value{GDBN} would switch to using the console interpreter, rendering
13675 the IDE inoperable!
13677 @kindex interpreter-exec
13678 Although you may only choose a single interpreter at startup, you may execute
13679 commands in any interpreter from the current interpreter using the appropriate
13680 command. If you are running the console interpreter, simply use the
13681 @code{interpreter-exec} command:
13684 interpreter-exec mi "-data-list-register-names"
13687 @sc{gdb/mi} has a similar command, although it is only available in versions of
13688 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13691 @chapter @value{GDBN} Text User Interface
13695 * TUI Overview:: TUI overview
13696 * TUI Keys:: TUI key bindings
13697 * TUI Single Key Mode:: TUI single key mode
13698 * TUI Commands:: TUI specific commands
13699 * TUI Configuration:: TUI configuration variables
13702 The @value{GDBN} Text User Interface, TUI in short,
13703 is a terminal interface which uses the @code{curses} library
13704 to show the source file, the assembly output, the program registers
13705 and @value{GDBN} commands in separate text windows.
13706 The TUI is available only when @value{GDBN} is configured
13707 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13710 @section TUI overview
13712 The TUI has two display modes that can be switched while
13717 A curses (or TUI) mode in which it displays several text
13718 windows on the terminal.
13721 A standard mode which corresponds to the @value{GDBN} configured without
13725 In the TUI mode, @value{GDBN} can display several text window
13730 This window is the @value{GDBN} command window with the @value{GDBN}
13731 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13732 managed using readline but through the TUI. The @emph{command}
13733 window is always visible.
13736 The source window shows the source file of the program. The current
13737 line as well as active breakpoints are displayed in this window.
13740 The assembly window shows the disassembly output of the program.
13743 This window shows the processor registers. It detects when
13744 a register is changed and when this is the case, registers that have
13745 changed are highlighted.
13749 The source and assembly windows show the current program position
13750 by highlighting the current line and marking them with the @samp{>} marker.
13751 Breakpoints are also indicated with two markers. A first one
13752 indicates the breakpoint type:
13756 Breakpoint which was hit at least once.
13759 Breakpoint which was never hit.
13762 Hardware breakpoint which was hit at least once.
13765 Hardware breakpoint which was never hit.
13769 The second marker indicates whether the breakpoint is enabled or not:
13773 Breakpoint is enabled.
13776 Breakpoint is disabled.
13780 The source, assembly and register windows are attached to the thread
13781 and the frame position. They are updated when the current thread
13782 changes, when the frame changes or when the program counter changes.
13783 These three windows are arranged by the TUI according to several
13784 layouts. The layout defines which of these three windows are visible.
13785 The following layouts are available:
13795 source and assembly
13798 source and registers
13801 assembly and registers
13805 On top of the command window a status line gives various information
13806 concerning the current process begin debugged. The status line is
13807 updated when the information it shows changes. The following fields
13812 Indicates the current gdb target
13813 (@pxref{Targets, ,Specifying a Debugging Target}).
13816 Gives information about the current process or thread number.
13817 When no process is being debugged, this field is set to @code{No process}.
13820 Gives the current function name for the selected frame.
13821 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13822 When there is no symbol corresponding to the current program counter
13823 the string @code{??} is displayed.
13826 Indicates the current line number for the selected frame.
13827 When the current line number is not known the string @code{??} is displayed.
13830 Indicates the current program counter address.
13835 @section TUI Key Bindings
13836 @cindex TUI key bindings
13838 The TUI installs several key bindings in the readline keymaps
13839 (@pxref{Command Line Editing}).
13840 They allow to leave or enter in the TUI mode or they operate
13841 directly on the TUI layout and windows. The TUI also provides
13842 a @emph{SingleKey} keymap which binds several keys directly to
13843 @value{GDBN} commands. The following key bindings
13844 are installed for both TUI mode and the @value{GDBN} standard mode.
13853 Enter or leave the TUI mode. When the TUI mode is left,
13854 the curses window management is left and @value{GDBN} operates using
13855 its standard mode writing on the terminal directly. When the TUI
13856 mode is entered, the control is given back to the curses windows.
13857 The screen is then refreshed.
13861 Use a TUI layout with only one window. The layout will
13862 either be @samp{source} or @samp{assembly}. When the TUI mode
13863 is not active, it will switch to the TUI mode.
13865 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13869 Use a TUI layout with at least two windows. When the current
13870 layout shows already two windows, a next layout with two windows is used.
13871 When a new layout is chosen, one window will always be common to the
13872 previous layout and the new one.
13874 Think of it as the Emacs @kbd{C-x 2} binding.
13878 Change the active window. The TUI associates several key bindings
13879 (like scrolling and arrow keys) to the active window. This command
13880 gives the focus to the next TUI window.
13882 Think of it as the Emacs @kbd{C-x o} binding.
13886 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13887 (@pxref{TUI Single Key Mode}).
13891 The following key bindings are handled only by the TUI mode:
13896 Scroll the active window one page up.
13900 Scroll the active window one page down.
13904 Scroll the active window one line up.
13908 Scroll the active window one line down.
13912 Scroll the active window one column left.
13916 Scroll the active window one column right.
13920 Refresh the screen.
13924 In the TUI mode, the arrow keys are used by the active window
13925 for scrolling. This means they are available for readline when the
13926 active window is the command window. When the command window
13927 does not have the focus, it is necessary to use other readline
13928 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
13930 @node TUI Single Key Mode
13931 @section TUI Single Key Mode
13932 @cindex TUI single key mode
13934 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13935 key binding in the readline keymaps to connect single keys to
13939 @kindex c @r{(SingleKey TUI key)}
13943 @kindex d @r{(SingleKey TUI key)}
13947 @kindex f @r{(SingleKey TUI key)}
13951 @kindex n @r{(SingleKey TUI key)}
13955 @kindex q @r{(SingleKey TUI key)}
13957 exit the @emph{SingleKey} mode.
13959 @kindex r @r{(SingleKey TUI key)}
13963 @kindex s @r{(SingleKey TUI key)}
13967 @kindex u @r{(SingleKey TUI key)}
13971 @kindex v @r{(SingleKey TUI key)}
13975 @kindex w @r{(SingleKey TUI key)}
13981 Other keys temporarily switch to the @value{GDBN} command prompt.
13982 The key that was pressed is inserted in the editing buffer so that
13983 it is possible to type most @value{GDBN} commands without interaction
13984 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13985 @emph{SingleKey} mode is restored. The only way to permanently leave
13986 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13990 @section TUI specific commands
13991 @cindex TUI commands
13993 The TUI has specific commands to control the text windows.
13994 These commands are always available, that is they do not depend on
13995 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13996 is in the standard mode, using these commands will automatically switch
14002 List and give the size of all displayed windows.
14005 @kindex layout next
14006 Display the next layout.
14009 @kindex layout prev
14010 Display the previous layout.
14014 Display the source window only.
14018 Display the assembly window only.
14021 @kindex layout split
14022 Display the source and assembly window.
14025 @kindex layout regs
14026 Display the register window together with the source or assembly window.
14028 @item focus next | prev | src | asm | regs | split
14030 Set the focus to the named window.
14031 This command allows to change the active window so that scrolling keys
14032 can be affected to another window.
14036 Refresh the screen. This is similar to using @key{C-L} key.
14040 Update the source window and the current execution point.
14042 @item winheight @var{name} +@var{count}
14043 @itemx winheight @var{name} -@var{count}
14045 Change the height of the window @var{name} by @var{count}
14046 lines. Positive counts increase the height, while negative counts
14051 @node TUI Configuration
14052 @section TUI configuration variables
14053 @cindex TUI configuration variables
14055 The TUI has several configuration variables that control the
14056 appearance of windows on the terminal.
14059 @item set tui border-kind @var{kind}
14060 @kindex set tui border-kind
14061 Select the border appearance for the source, assembly and register windows.
14062 The possible values are the following:
14065 Use a space character to draw the border.
14068 Use ascii characters + - and | to draw the border.
14071 Use the Alternate Character Set to draw the border. The border is
14072 drawn using character line graphics if the terminal supports them.
14076 @item set tui active-border-mode @var{mode}
14077 @kindex set tui active-border-mode
14078 Select the attributes to display the border of the active window.
14079 The possible values are @code{normal}, @code{standout}, @code{reverse},
14080 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14082 @item set tui border-mode @var{mode}
14083 @kindex set tui border-mode
14084 Select the attributes to display the border of other windows.
14085 The @var{mode} can be one of the following:
14088 Use normal attributes to display the border.
14094 Use reverse video mode.
14097 Use half bright mode.
14099 @item half-standout
14100 Use half bright and standout mode.
14103 Use extra bright or bold mode.
14105 @item bold-standout
14106 Use extra bright or bold and standout mode.
14113 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14116 @cindex @sc{gnu} Emacs
14117 A special interface allows you to use @sc{gnu} Emacs to view (and
14118 edit) the source files for the program you are debugging with
14121 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14122 executable file you want to debug as an argument. This command starts
14123 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14124 created Emacs buffer.
14125 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14127 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14132 All ``terminal'' input and output goes through the Emacs buffer.
14135 This applies both to @value{GDBN} commands and their output, and to the input
14136 and output done by the program you are debugging.
14138 This is useful because it means that you can copy the text of previous
14139 commands and input them again; you can even use parts of the output
14142 All the facilities of Emacs' Shell mode are available for interacting
14143 with your program. In particular, you can send signals the usual
14144 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14149 @value{GDBN} displays source code through Emacs.
14152 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14153 source file for that frame and puts an arrow (@samp{=>}) at the
14154 left margin of the current line. Emacs uses a separate buffer for
14155 source display, and splits the screen to show both your @value{GDBN} session
14158 Explicit @value{GDBN} @code{list} or search commands still produce output as
14159 usual, but you probably have no reason to use them from Emacs.
14161 If you specify an absolute file name when prompted for the @kbd{M-x
14162 gdb} argument, then Emacs sets your current working directory to where
14163 your program resides. If you only specify the file name, then Emacs
14164 sets your current working directory to to the directory associated
14165 with the previous buffer. In this case, @value{GDBN} may find your
14166 program by searching your environment's @code{PATH} variable, but on
14167 some operating systems it might not find the source. So, although the
14168 @value{GDBN} input and output session proceeds normally, the auxiliary
14169 buffer does not display the current source and line of execution.
14171 The initial working directory of @value{GDBN} is printed on the top
14172 line of the @value{GDBN} I/O buffer and this serves as a default for
14173 the commands that specify files for @value{GDBN} to operate
14174 on. @xref{Files, ,Commands to specify files}.
14176 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14177 need to call @value{GDBN} by a different name (for example, if you
14178 keep several configurations around, with different names) you can
14179 customize the Emacs variable @code{gud-gdb-command-name} to run the
14182 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14183 addition to the standard Shell mode commands:
14187 Describe the features of Emacs' @value{GDBN} Mode.
14190 Execute to another source line, like the @value{GDBN} @code{step} command; also
14191 update the display window to show the current file and location.
14194 Execute to next source line in this function, skipping all function
14195 calls, like the @value{GDBN} @code{next} command. Then update the display window
14196 to show the current file and location.
14199 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14200 display window accordingly.
14203 Execute until exit from the selected stack frame, like the @value{GDBN}
14204 @code{finish} command.
14207 Continue execution of your program, like the @value{GDBN} @code{continue}
14211 Go up the number of frames indicated by the numeric argument
14212 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14213 like the @value{GDBN} @code{up} command.
14216 Go down the number of frames indicated by the numeric argument, like the
14217 @value{GDBN} @code{down} command.
14220 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14221 tells @value{GDBN} to set a breakpoint on the source line point is on.
14223 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14224 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14225 point to any frame in the stack and type @key{RET} to make it become the
14226 current frame and display the associated source in the source buffer.
14227 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14230 If you accidentally delete the source-display buffer, an easy way to get
14231 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14232 request a frame display; when you run under Emacs, this recreates
14233 the source buffer if necessary to show you the context of the current
14236 The source files displayed in Emacs are in ordinary Emacs buffers
14237 which are visiting the source files in the usual way. You can edit
14238 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14239 communicates with Emacs in terms of line numbers. If you add or
14240 delete lines from the text, the line numbers that @value{GDBN} knows cease
14241 to correspond properly with the code.
14243 The description given here is for GNU Emacs version 21.3 and a more
14244 detailed description of its interaction with @value{GDBN} is given in
14245 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14247 @c The following dropped because Epoch is nonstandard. Reactivate
14248 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14250 @kindex Emacs Epoch environment
14254 Version 18 of @sc{gnu} Emacs has a built-in window system
14255 called the @code{epoch}
14256 environment. Users of this environment can use a new command,
14257 @code{inspect} which performs identically to @code{print} except that
14258 each value is printed in its own window.
14263 @chapter The @sc{gdb/mi} Interface
14265 @unnumberedsec Function and Purpose
14267 @cindex @sc{gdb/mi}, its purpose
14268 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14269 specifically intended to support the development of systems which use
14270 the debugger as just one small component of a larger system.
14272 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14273 in the form of a reference manual.
14275 Note that @sc{gdb/mi} is still under construction, so some of the
14276 features described below are incomplete and subject to change.
14278 @unnumberedsec Notation and Terminology
14280 @cindex notational conventions, for @sc{gdb/mi}
14281 This chapter uses the following notation:
14285 @code{|} separates two alternatives.
14288 @code{[ @var{something} ]} indicates that @var{something} is optional:
14289 it may or may not be given.
14292 @code{( @var{group} )*} means that @var{group} inside the parentheses
14293 may repeat zero or more times.
14296 @code{( @var{group} )+} means that @var{group} inside the parentheses
14297 may repeat one or more times.
14300 @code{"@var{string}"} means a literal @var{string}.
14304 @heading Dependencies
14307 @heading Acknowledgments
14309 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14313 * GDB/MI Command Syntax::
14314 * GDB/MI Compatibility with CLI::
14315 * GDB/MI Output Records::
14316 * GDB/MI Command Description Format::
14317 * GDB/MI Breakpoint Table Commands::
14318 * GDB/MI Data Manipulation::
14319 * GDB/MI Program Control::
14320 * GDB/MI Miscellaneous Commands::
14322 * GDB/MI Kod Commands::
14323 * GDB/MI Memory Overlay Commands::
14324 * GDB/MI Signal Handling Commands::
14326 * GDB/MI Stack Manipulation::
14327 * GDB/MI Symbol Query::
14328 * GDB/MI Target Manipulation::
14329 * GDB/MI Thread Commands::
14330 * GDB/MI Tracepoint Commands::
14331 * GDB/MI Variable Objects::
14334 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14335 @node GDB/MI Command Syntax
14336 @section @sc{gdb/mi} Command Syntax
14339 * GDB/MI Input Syntax::
14340 * GDB/MI Output Syntax::
14341 * GDB/MI Simple Examples::
14344 @node GDB/MI Input Syntax
14345 @subsection @sc{gdb/mi} Input Syntax
14347 @cindex input syntax for @sc{gdb/mi}
14348 @cindex @sc{gdb/mi}, input syntax
14350 @item @var{command} @expansion{}
14351 @code{@var{cli-command} | @var{mi-command}}
14353 @item @var{cli-command} @expansion{}
14354 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14355 @var{cli-command} is any existing @value{GDBN} CLI command.
14357 @item @var{mi-command} @expansion{}
14358 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14359 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14361 @item @var{token} @expansion{}
14362 "any sequence of digits"
14364 @item @var{option} @expansion{}
14365 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14367 @item @var{parameter} @expansion{}
14368 @code{@var{non-blank-sequence} | @var{c-string}}
14370 @item @var{operation} @expansion{}
14371 @emph{any of the operations described in this chapter}
14373 @item @var{non-blank-sequence} @expansion{}
14374 @emph{anything, provided it doesn't contain special characters such as
14375 "-", @var{nl}, """ and of course " "}
14377 @item @var{c-string} @expansion{}
14378 @code{""" @var{seven-bit-iso-c-string-content} """}
14380 @item @var{nl} @expansion{}
14389 The CLI commands are still handled by the @sc{mi} interpreter; their
14390 output is described below.
14393 The @code{@var{token}}, when present, is passed back when the command
14397 Some @sc{mi} commands accept optional arguments as part of the parameter
14398 list. Each option is identified by a leading @samp{-} (dash) and may be
14399 followed by an optional argument parameter. Options occur first in the
14400 parameter list and can be delimited from normal parameters using
14401 @samp{--} (this is useful when some parameters begin with a dash).
14408 We want easy access to the existing CLI syntax (for debugging).
14411 We want it to be easy to spot a @sc{mi} operation.
14414 @node GDB/MI Output Syntax
14415 @subsection @sc{gdb/mi} Output Syntax
14417 @cindex output syntax of @sc{gdb/mi}
14418 @cindex @sc{gdb/mi}, output syntax
14419 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14420 followed, optionally, by a single result record. This result record
14421 is for the most recent command. The sequence of output records is
14422 terminated by @samp{(@value{GDBP})}.
14424 If an input command was prefixed with a @code{@var{token}} then the
14425 corresponding output for that command will also be prefixed by that same
14429 @item @var{output} @expansion{}
14430 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14432 @item @var{result-record} @expansion{}
14433 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14435 @item @var{out-of-band-record} @expansion{}
14436 @code{@var{async-record} | @var{stream-record}}
14438 @item @var{async-record} @expansion{}
14439 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14441 @item @var{exec-async-output} @expansion{}
14442 @code{[ @var{token} ] "*" @var{async-output}}
14444 @item @var{status-async-output} @expansion{}
14445 @code{[ @var{token} ] "+" @var{async-output}}
14447 @item @var{notify-async-output} @expansion{}
14448 @code{[ @var{token} ] "=" @var{async-output}}
14450 @item @var{async-output} @expansion{}
14451 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14453 @item @var{result-class} @expansion{}
14454 @code{"done" | "running" | "connected" | "error" | "exit"}
14456 @item @var{async-class} @expansion{}
14457 @code{"stopped" | @var{others}} (where @var{others} will be added
14458 depending on the needs---this is still in development).
14460 @item @var{result} @expansion{}
14461 @code{ @var{variable} "=" @var{value}}
14463 @item @var{variable} @expansion{}
14464 @code{ @var{string} }
14466 @item @var{value} @expansion{}
14467 @code{ @var{const} | @var{tuple} | @var{list} }
14469 @item @var{const} @expansion{}
14470 @code{@var{c-string}}
14472 @item @var{tuple} @expansion{}
14473 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14475 @item @var{list} @expansion{}
14476 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14477 @var{result} ( "," @var{result} )* "]" }
14479 @item @var{stream-record} @expansion{}
14480 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14482 @item @var{console-stream-output} @expansion{}
14483 @code{"~" @var{c-string}}
14485 @item @var{target-stream-output} @expansion{}
14486 @code{"@@" @var{c-string}}
14488 @item @var{log-stream-output} @expansion{}
14489 @code{"&" @var{c-string}}
14491 @item @var{nl} @expansion{}
14494 @item @var{token} @expansion{}
14495 @emph{any sequence of digits}.
14503 All output sequences end in a single line containing a period.
14506 The @code{@var{token}} is from the corresponding request. If an execution
14507 command is interrupted by the @samp{-exec-interrupt} command, the
14508 @var{token} associated with the @samp{*stopped} message is the one of the
14509 original execution command, not the one of the interrupt command.
14512 @cindex status output in @sc{gdb/mi}
14513 @var{status-async-output} contains on-going status information about the
14514 progress of a slow operation. It can be discarded. All status output is
14515 prefixed by @samp{+}.
14518 @cindex async output in @sc{gdb/mi}
14519 @var{exec-async-output} contains asynchronous state change on the target
14520 (stopped, started, disappeared). All async output is prefixed by
14524 @cindex notify output in @sc{gdb/mi}
14525 @var{notify-async-output} contains supplementary information that the
14526 client should handle (e.g., a new breakpoint information). All notify
14527 output is prefixed by @samp{=}.
14530 @cindex console output in @sc{gdb/mi}
14531 @var{console-stream-output} is output that should be displayed as is in the
14532 console. It is the textual response to a CLI command. All the console
14533 output is prefixed by @samp{~}.
14536 @cindex target output in @sc{gdb/mi}
14537 @var{target-stream-output} is the output produced by the target program.
14538 All the target output is prefixed by @samp{@@}.
14541 @cindex log output in @sc{gdb/mi}
14542 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14543 instance messages that should be displayed as part of an error log. All
14544 the log output is prefixed by @samp{&}.
14547 @cindex list output in @sc{gdb/mi}
14548 New @sc{gdb/mi} commands should only output @var{lists} containing
14554 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14555 details about the various output records.
14557 @node GDB/MI Simple Examples
14558 @subsection Simple Examples of @sc{gdb/mi} Interaction
14559 @cindex @sc{gdb/mi}, simple examples
14561 This subsection presents several simple examples of interaction using
14562 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14563 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14564 the output received from @sc{gdb/mi}.
14566 @subsubheading Target Stop
14567 @c Ummm... There is no "-stop" command. This assumes async, no?
14568 Here's an example of stopping the inferior process:
14579 <- *stop,reason="stop",address="0x123",source="a.c:123"
14583 @subsubheading Simple CLI Command
14585 Here's an example of a simple CLI command being passed through
14586 @sc{gdb/mi} and on to the CLI.
14596 @subsubheading Command With Side Effects
14599 -> -symbol-file xyz.exe
14600 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14604 @subsubheading A Bad Command
14606 Here's what happens if you pass a non-existent command:
14610 <- ^error,msg="Undefined MI command: rubbish"
14614 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14615 @node GDB/MI Compatibility with CLI
14616 @section @sc{gdb/mi} Compatibility with CLI
14618 @cindex compatibility, @sc{gdb/mi} and CLI
14619 @cindex @sc{gdb/mi}, compatibility with CLI
14620 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14621 accepts existing CLI commands. As specified by the syntax, such
14622 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14625 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14626 clients and not as a reliable interface into the CLI. Since the command
14627 is being interpreteted in an environment that assumes @sc{gdb/mi}
14628 behaviour, the exact output of such commands is likely to end up being
14629 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14632 @node GDB/MI Output Records
14633 @section @sc{gdb/mi} Output Records
14636 * GDB/MI Result Records::
14637 * GDB/MI Stream Records::
14638 * GDB/MI Out-of-band Records::
14641 @node GDB/MI Result Records
14642 @subsection @sc{gdb/mi} Result Records
14644 @cindex result records in @sc{gdb/mi}
14645 @cindex @sc{gdb/mi}, result records
14646 In addition to a number of out-of-band notifications, the response to a
14647 @sc{gdb/mi} command includes one of the following result indications:
14651 @item "^done" [ "," @var{results} ]
14652 The synchronous operation was successful, @code{@var{results}} are the return
14657 @c Is this one correct? Should it be an out-of-band notification?
14658 The asynchronous operation was successfully started. The target is
14661 @item "^error" "," @var{c-string}
14663 The operation failed. The @code{@var{c-string}} contains the corresponding
14667 @node GDB/MI Stream Records
14668 @subsection @sc{gdb/mi} Stream Records
14670 @cindex @sc{gdb/mi}, stream records
14671 @cindex stream records in @sc{gdb/mi}
14672 @value{GDBN} internally maintains a number of output streams: the console, the
14673 target, and the log. The output intended for each of these streams is
14674 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14676 Each stream record begins with a unique @dfn{prefix character} which
14677 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14678 Syntax}). In addition to the prefix, each stream record contains a
14679 @code{@var{string-output}}. This is either raw text (with an implicit new
14680 line) or a quoted C string (which does not contain an implicit newline).
14683 @item "~" @var{string-output}
14684 The console output stream contains text that should be displayed in the
14685 CLI console window. It contains the textual responses to CLI commands.
14687 @item "@@" @var{string-output}
14688 The target output stream contains any textual output from the running
14691 @item "&" @var{string-output}
14692 The log stream contains debugging messages being produced by @value{GDBN}'s
14696 @node GDB/MI Out-of-band Records
14697 @subsection @sc{gdb/mi} Out-of-band Records
14699 @cindex out-of-band records in @sc{gdb/mi}
14700 @cindex @sc{gdb/mi}, out-of-band records
14701 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14702 additional changes that have occurred. Those changes can either be a
14703 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14704 target activity (e.g., target stopped).
14706 The following is a preliminary list of possible out-of-band records.
14713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14714 @node GDB/MI Command Description Format
14715 @section @sc{gdb/mi} Command Description Format
14717 The remaining sections describe blocks of commands. Each block of
14718 commands is laid out in a fashion similar to this section.
14720 Note the the line breaks shown in the examples are here only for
14721 readability. They don't appear in the real output.
14722 Also note that the commands with a non-available example (N.A.@:) are
14723 not yet implemented.
14725 @subheading Motivation
14727 The motivation for this collection of commands.
14729 @subheading Introduction
14731 A brief introduction to this collection of commands as a whole.
14733 @subheading Commands
14735 For each command in the block, the following is described:
14737 @subsubheading Synopsis
14740 -command @var{args}@dots{}
14743 @subsubheading @value{GDBN} Command
14745 The corresponding @value{GDBN} CLI command.
14747 @subsubheading Result
14749 @subsubheading Out-of-band
14751 @subsubheading Notes
14753 @subsubheading Example
14756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14757 @node GDB/MI Breakpoint Table Commands
14758 @section @sc{gdb/mi} Breakpoint table commands
14760 @cindex breakpoint commands for @sc{gdb/mi}
14761 @cindex @sc{gdb/mi}, breakpoint commands
14762 This section documents @sc{gdb/mi} commands for manipulating
14765 @subheading The @code{-break-after} Command
14766 @findex -break-after
14768 @subsubheading Synopsis
14771 -break-after @var{number} @var{count}
14774 The breakpoint number @var{number} is not in effect until it has been
14775 hit @var{count} times. To see how this is reflected in the output of
14776 the @samp{-break-list} command, see the description of the
14777 @samp{-break-list} command below.
14779 @subsubheading @value{GDBN} Command
14781 The corresponding @value{GDBN} command is @samp{ignore}.
14783 @subsubheading Example
14788 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14795 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14796 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14797 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14798 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14799 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14800 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14801 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14802 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14803 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14809 @subheading The @code{-break-catch} Command
14810 @findex -break-catch
14812 @subheading The @code{-break-commands} Command
14813 @findex -break-commands
14817 @subheading The @code{-break-condition} Command
14818 @findex -break-condition
14820 @subsubheading Synopsis
14823 -break-condition @var{number} @var{expr}
14826 Breakpoint @var{number} will stop the program only if the condition in
14827 @var{expr} is true. The condition becomes part of the
14828 @samp{-break-list} output (see the description of the @samp{-break-list}
14831 @subsubheading @value{GDBN} Command
14833 The corresponding @value{GDBN} command is @samp{condition}.
14835 @subsubheading Example
14839 -break-condition 1 1
14843 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14844 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14845 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14846 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14847 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14848 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14849 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14850 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14851 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14852 times="0",ignore="3"@}]@}
14856 @subheading The @code{-break-delete} Command
14857 @findex -break-delete
14859 @subsubheading Synopsis
14862 -break-delete ( @var{breakpoint} )+
14865 Delete the breakpoint(s) whose number(s) are specified in the argument
14866 list. This is obviously reflected in the breakpoint list.
14868 @subsubheading @value{GDBN} command
14870 The corresponding @value{GDBN} command is @samp{delete}.
14872 @subsubheading Example
14880 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14881 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14882 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14883 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14884 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14885 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14886 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14891 @subheading The @code{-break-disable} Command
14892 @findex -break-disable
14894 @subsubheading Synopsis
14897 -break-disable ( @var{breakpoint} )+
14900 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14901 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14903 @subsubheading @value{GDBN} Command
14905 The corresponding @value{GDBN} command is @samp{disable}.
14907 @subsubheading Example
14915 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14916 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14917 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14918 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14919 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14920 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14921 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14922 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14923 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14927 @subheading The @code{-break-enable} Command
14928 @findex -break-enable
14930 @subsubheading Synopsis
14933 -break-enable ( @var{breakpoint} )+
14936 Enable (previously disabled) @var{breakpoint}(s).
14938 @subsubheading @value{GDBN} Command
14940 The corresponding @value{GDBN} command is @samp{enable}.
14942 @subsubheading Example
14950 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14957 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14958 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14962 @subheading The @code{-break-info} Command
14963 @findex -break-info
14965 @subsubheading Synopsis
14968 -break-info @var{breakpoint}
14972 Get information about a single breakpoint.
14974 @subsubheading @value{GDBN} command
14976 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14978 @subsubheading Example
14981 @subheading The @code{-break-insert} Command
14982 @findex -break-insert
14984 @subsubheading Synopsis
14987 -break-insert [ -t ] [ -h ] [ -r ]
14988 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14989 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14993 If specified, @var{line}, can be one of:
15000 @item filename:linenum
15001 @item filename:function
15005 The possible optional parameters of this command are:
15009 Insert a tempoary breakpoint.
15011 Insert a hardware breakpoint.
15012 @item -c @var{condition}
15013 Make the breakpoint conditional on @var{condition}.
15014 @item -i @var{ignore-count}
15015 Initialize the @var{ignore-count}.
15017 Insert a regular breakpoint in all the functions whose names match the
15018 given regular expression. Other flags are not applicable to regular
15022 @subsubheading Result
15024 The result is in the form:
15027 ^done,bkptno="@var{number}",func="@var{funcname}",
15028 file="@var{filename}",line="@var{lineno}"
15032 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15033 is the name of the function where the breakpoint was inserted,
15034 @var{filename} is the name of the source file which contains this
15035 function, and @var{lineno} is the source line number within that file.
15037 Note: this format is open to change.
15038 @c An out-of-band breakpoint instead of part of the result?
15040 @subsubheading @value{GDBN} Command
15042 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15043 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15045 @subsubheading Example
15050 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15052 -break-insert -t foo
15053 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15056 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15057 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15058 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15059 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15060 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15061 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15062 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15063 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15064 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15065 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15066 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15068 -break-insert -r foo.*
15069 ~int foo(int, int);
15070 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15074 @subheading The @code{-break-list} Command
15075 @findex -break-list
15077 @subsubheading Synopsis
15083 Displays the list of inserted breakpoints, showing the following fields:
15087 number of the breakpoint
15089 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15091 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15094 is the breakpoint enabled or no: @samp{y} or @samp{n}
15096 memory location at which the breakpoint is set
15098 logical location of the breakpoint, expressed by function name, file
15101 number of times the breakpoint has been hit
15104 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15105 @code{body} field is an empty list.
15107 @subsubheading @value{GDBN} Command
15109 The corresponding @value{GDBN} command is @samp{info break}.
15111 @subsubheading Example
15116 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15117 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15118 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15119 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15120 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15121 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15122 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15123 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15124 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15125 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15126 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15130 Here's an example of the result when there are no breakpoints:
15135 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15146 @subheading The @code{-break-watch} Command
15147 @findex -break-watch
15149 @subsubheading Synopsis
15152 -break-watch [ -a | -r ]
15155 Create a watchpoint. With the @samp{-a} option it will create an
15156 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15157 read from or on a write to the memory location. With the @samp{-r}
15158 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15159 trigger only when the memory location is accessed for reading. Without
15160 either of the options, the watchpoint created is a regular watchpoint,
15161 i.e. it will trigger when the memory location is accessed for writing.
15162 @xref{Set Watchpoints, , Setting watchpoints}.
15164 Note that @samp{-break-list} will report a single list of watchpoints and
15165 breakpoints inserted.
15167 @subsubheading @value{GDBN} Command
15169 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15172 @subsubheading Example
15174 Setting a watchpoint on a variable in the @code{main} function:
15179 ^done,wpt=@{number="2",exp="x"@}
15183 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15184 value=@{old="-268439212",new="55"@},
15185 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15189 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15190 the program execution twice: first for the variable changing value, then
15191 for the watchpoint going out of scope.
15196 ^done,wpt=@{number="5",exp="C"@}
15200 ^done,reason="watchpoint-trigger",
15201 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15202 frame=@{func="callee4",args=[],
15203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15207 ^done,reason="watchpoint-scope",wpnum="5",
15208 frame=@{func="callee3",args=[@{name="strarg",
15209 value="0x11940 \"A string argument.\""@}],
15210 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15214 Listing breakpoints and watchpoints, at different points in the program
15215 execution. Note that once the watchpoint goes out of scope, it is
15221 ^done,wpt=@{number="2",exp="C"@}
15224 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15225 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15226 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15227 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15228 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15229 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15230 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15231 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15232 addr="0x00010734",func="callee4",
15233 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15234 bkpt=@{number="2",type="watchpoint",disp="keep",
15235 enabled="y",addr="",what="C",times="0"@}]@}
15239 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15240 value=@{old="-276895068",new="3"@},
15241 frame=@{func="callee4",args=[],
15242 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15245 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15246 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15247 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15248 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15249 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15250 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15251 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15252 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15253 addr="0x00010734",func="callee4",
15254 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15255 bkpt=@{number="2",type="watchpoint",disp="keep",
15256 enabled="y",addr="",what="C",times="-5"@}]@}
15260 ^done,reason="watchpoint-scope",wpnum="2",
15261 frame=@{func="callee3",args=[@{name="strarg",
15262 value="0x11940 \"A string argument.\""@}],
15263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15266 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15267 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15268 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15269 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15270 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15271 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15272 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15273 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15274 addr="0x00010734",func="callee4",
15275 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15279 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15280 @node GDB/MI Data Manipulation
15281 @section @sc{gdb/mi} Data Manipulation
15283 @cindex data manipulation, in @sc{gdb/mi}
15284 @cindex @sc{gdb/mi}, data manipulation
15285 This section describes the @sc{gdb/mi} commands that manipulate data:
15286 examine memory and registers, evaluate expressions, etc.
15288 @c REMOVED FROM THE INTERFACE.
15289 @c @subheading -data-assign
15290 @c Change the value of a program variable. Plenty of side effects.
15291 @c @subsubheading GDB command
15293 @c @subsubheading Example
15296 @subheading The @code{-data-disassemble} Command
15297 @findex -data-disassemble
15299 @subsubheading Synopsis
15303 [ -s @var{start-addr} -e @var{end-addr} ]
15304 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15312 @item @var{start-addr}
15313 is the beginning address (or @code{$pc})
15314 @item @var{end-addr}
15316 @item @var{filename}
15317 is the name of the file to disassemble
15318 @item @var{linenum}
15319 is the line number to disassemble around
15321 is the the number of disassembly lines to be produced. If it is -1,
15322 the whole function will be disassembled, in case no @var{end-addr} is
15323 specified. If @var{end-addr} is specified as a non-zero value, and
15324 @var{lines} is lower than the number of disassembly lines between
15325 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15326 displayed; if @var{lines} is higher than the number of lines between
15327 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15330 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15334 @subsubheading Result
15336 The output for each instruction is composed of four fields:
15345 Note that whatever included in the instruction field, is not manipulated
15346 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15348 @subsubheading @value{GDBN} Command
15350 There's no direct mapping from this command to the CLI.
15352 @subsubheading Example
15354 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15358 -data-disassemble -s $pc -e "$pc + 20" -- 0
15361 @{address="0x000107c0",func-name="main",offset="4",
15362 inst="mov 2, %o0"@},
15363 @{address="0x000107c4",func-name="main",offset="8",
15364 inst="sethi %hi(0x11800), %o2"@},
15365 @{address="0x000107c8",func-name="main",offset="12",
15366 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15367 @{address="0x000107cc",func-name="main",offset="16",
15368 inst="sethi %hi(0x11800), %o2"@},
15369 @{address="0x000107d0",func-name="main",offset="20",
15370 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15374 Disassemble the whole @code{main} function. Line 32 is part of
15378 -data-disassemble -f basics.c -l 32 -- 0
15380 @{address="0x000107bc",func-name="main",offset="0",
15381 inst="save %sp, -112, %sp"@},
15382 @{address="0x000107c0",func-name="main",offset="4",
15383 inst="mov 2, %o0"@},
15384 @{address="0x000107c4",func-name="main",offset="8",
15385 inst="sethi %hi(0x11800), %o2"@},
15387 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15388 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15392 Disassemble 3 instructions from the start of @code{main}:
15396 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15398 @{address="0x000107bc",func-name="main",offset="0",
15399 inst="save %sp, -112, %sp"@},
15400 @{address="0x000107c0",func-name="main",offset="4",
15401 inst="mov 2, %o0"@},
15402 @{address="0x000107c4",func-name="main",offset="8",
15403 inst="sethi %hi(0x11800), %o2"@}]
15407 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15411 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15413 src_and_asm_line=@{line="31",
15414 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15415 testsuite/gdb.mi/basics.c",line_asm_insn=[
15416 @{address="0x000107bc",func-name="main",offset="0",
15417 inst="save %sp, -112, %sp"@}]@},
15418 src_and_asm_line=@{line="32",
15419 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15420 testsuite/gdb.mi/basics.c",line_asm_insn=[
15421 @{address="0x000107c0",func-name="main",offset="4",
15422 inst="mov 2, %o0"@},
15423 @{address="0x000107c4",func-name="main",offset="8",
15424 inst="sethi %hi(0x11800), %o2"@}]@}]
15429 @subheading The @code{-data-evaluate-expression} Command
15430 @findex -data-evaluate-expression
15432 @subsubheading Synopsis
15435 -data-evaluate-expression @var{expr}
15438 Evaluate @var{expr} as an expression. The expression could contain an
15439 inferior function call. The function call will execute synchronously.
15440 If the expression contains spaces, it must be enclosed in double quotes.
15442 @subsubheading @value{GDBN} Command
15444 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15445 @samp{call}. In @code{gdbtk} only, there's a corresponding
15446 @samp{gdb_eval} command.
15448 @subsubheading Example
15450 In the following example, the numbers that precede the commands are the
15451 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15452 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15456 211-data-evaluate-expression A
15459 311-data-evaluate-expression &A
15460 311^done,value="0xefffeb7c"
15462 411-data-evaluate-expression A+3
15465 511-data-evaluate-expression "A + 3"
15471 @subheading The @code{-data-list-changed-registers} Command
15472 @findex -data-list-changed-registers
15474 @subsubheading Synopsis
15477 -data-list-changed-registers
15480 Display a list of the registers that have changed.
15482 @subsubheading @value{GDBN} Command
15484 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15485 has the corresponding command @samp{gdb_changed_register_list}.
15487 @subsubheading Example
15489 On a PPC MBX board:
15497 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15498 args=[],file="try.c",line="5"@}
15500 -data-list-changed-registers
15501 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15502 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15503 "24","25","26","27","28","30","31","64","65","66","67","69"]
15508 @subheading The @code{-data-list-register-names} Command
15509 @findex -data-list-register-names
15511 @subsubheading Synopsis
15514 -data-list-register-names [ ( @var{regno} )+ ]
15517 Show a list of register names for the current target. If no arguments
15518 are given, it shows a list of the names of all the registers. If
15519 integer numbers are given as arguments, it will print a list of the
15520 names of the registers corresponding to the arguments. To ensure
15521 consistency between a register name and its number, the output list may
15522 include empty register names.
15524 @subsubheading @value{GDBN} Command
15526 @value{GDBN} does not have a command which corresponds to
15527 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15528 corresponding command @samp{gdb_regnames}.
15530 @subsubheading Example
15532 For the PPC MBX board:
15535 -data-list-register-names
15536 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15537 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15538 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15539 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15540 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15541 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15542 "", "pc","ps","cr","lr","ctr","xer"]
15544 -data-list-register-names 1 2 3
15545 ^done,register-names=["r1","r2","r3"]
15549 @subheading The @code{-data-list-register-values} Command
15550 @findex -data-list-register-values
15552 @subsubheading Synopsis
15555 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15558 Display the registers' contents. @var{fmt} is the format according to
15559 which the registers' contents are to be returned, followed by an optional
15560 list of numbers specifying the registers to display. A missing list of
15561 numbers indicates that the contents of all the registers must be returned.
15563 Allowed formats for @var{fmt} are:
15580 @subsubheading @value{GDBN} Command
15582 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15583 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15585 @subsubheading Example
15587 For a PPC MBX board (note: line breaks are for readability only, they
15588 don't appear in the actual output):
15592 -data-list-register-values r 64 65
15593 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15594 @{number="65",value="0x00029002"@}]
15596 -data-list-register-values x
15597 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15598 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15599 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15600 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15601 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15602 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15603 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15604 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15605 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15606 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15607 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15608 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15609 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15610 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15611 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15612 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15613 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15614 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15615 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15616 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15617 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15618 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15619 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15620 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15621 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15622 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15623 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15624 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15625 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15626 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15627 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15628 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15629 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15630 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15631 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15632 @{number="69",value="0x20002b03"@}]
15637 @subheading The @code{-data-read-memory} Command
15638 @findex -data-read-memory
15640 @subsubheading Synopsis
15643 -data-read-memory [ -o @var{byte-offset} ]
15644 @var{address} @var{word-format} @var{word-size}
15645 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15652 @item @var{address}
15653 An expression specifying the address of the first memory word to be
15654 read. Complex expressions containing embedded white space should be
15655 quoted using the C convention.
15657 @item @var{word-format}
15658 The format to be used to print the memory words. The notation is the
15659 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15662 @item @var{word-size}
15663 The size of each memory word in bytes.
15665 @item @var{nr-rows}
15666 The number of rows in the output table.
15668 @item @var{nr-cols}
15669 The number of columns in the output table.
15672 If present, indicates that each row should include an @sc{ascii} dump. The
15673 value of @var{aschar} is used as a padding character when a byte is not a
15674 member of the printable @sc{ascii} character set (printable @sc{ascii}
15675 characters are those whose code is between 32 and 126, inclusively).
15677 @item @var{byte-offset}
15678 An offset to add to the @var{address} before fetching memory.
15681 This command displays memory contents as a table of @var{nr-rows} by
15682 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15683 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15684 (returned as @samp{total-bytes}). Should less than the requested number
15685 of bytes be returned by the target, the missing words are identified
15686 using @samp{N/A}. The number of bytes read from the target is returned
15687 in @samp{nr-bytes} and the starting address used to read memory in
15690 The address of the next/previous row or page is available in
15691 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15694 @subsubheading @value{GDBN} Command
15696 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15697 @samp{gdb_get_mem} memory read command.
15699 @subsubheading Example
15701 Read six bytes of memory starting at @code{bytes+6} but then offset by
15702 @code{-6} bytes. Format as three rows of two columns. One byte per
15703 word. Display each word in hex.
15707 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15708 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15709 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15710 prev-page="0x0000138a",memory=[
15711 @{addr="0x00001390",data=["0x00","0x01"]@},
15712 @{addr="0x00001392",data=["0x02","0x03"]@},
15713 @{addr="0x00001394",data=["0x04","0x05"]@}]
15717 Read two bytes of memory starting at address @code{shorts + 64} and
15718 display as a single word formatted in decimal.
15722 5-data-read-memory shorts+64 d 2 1 1
15723 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15724 next-row="0x00001512",prev-row="0x0000150e",
15725 next-page="0x00001512",prev-page="0x0000150e",memory=[
15726 @{addr="0x00001510",data=["128"]@}]
15730 Read thirty two bytes of memory starting at @code{bytes+16} and format
15731 as eight rows of four columns. Include a string encoding with @samp{x}
15732 used as the non-printable character.
15736 4-data-read-memory bytes+16 x 1 8 4 x
15737 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15738 next-row="0x000013c0",prev-row="0x0000139c",
15739 next-page="0x000013c0",prev-page="0x00001380",memory=[
15740 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15741 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15742 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15743 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15744 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15745 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15746 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15747 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15751 @subheading The @code{-display-delete} Command
15752 @findex -display-delete
15754 @subsubheading Synopsis
15757 -display-delete @var{number}
15760 Delete the display @var{number}.
15762 @subsubheading @value{GDBN} Command
15764 The corresponding @value{GDBN} command is @samp{delete display}.
15766 @subsubheading Example
15770 @subheading The @code{-display-disable} Command
15771 @findex -display-disable
15773 @subsubheading Synopsis
15776 -display-disable @var{number}
15779 Disable display @var{number}.
15781 @subsubheading @value{GDBN} Command
15783 The corresponding @value{GDBN} command is @samp{disable display}.
15785 @subsubheading Example
15789 @subheading The @code{-display-enable} Command
15790 @findex -display-enable
15792 @subsubheading Synopsis
15795 -display-enable @var{number}
15798 Enable display @var{number}.
15800 @subsubheading @value{GDBN} Command
15802 The corresponding @value{GDBN} command is @samp{enable display}.
15804 @subsubheading Example
15808 @subheading The @code{-display-insert} Command
15809 @findex -display-insert
15811 @subsubheading Synopsis
15814 -display-insert @var{expression}
15817 Display @var{expression} every time the program stops.
15819 @subsubheading @value{GDBN} Command
15821 The corresponding @value{GDBN} command is @samp{display}.
15823 @subsubheading Example
15827 @subheading The @code{-display-list} Command
15828 @findex -display-list
15830 @subsubheading Synopsis
15836 List the displays. Do not show the current values.
15838 @subsubheading @value{GDBN} Command
15840 The corresponding @value{GDBN} command is @samp{info display}.
15842 @subsubheading Example
15846 @subheading The @code{-environment-cd} Command
15847 @findex -environment-cd
15849 @subsubheading Synopsis
15852 -environment-cd @var{pathdir}
15855 Set @value{GDBN}'s working directory.
15857 @subsubheading @value{GDBN} Command
15859 The corresponding @value{GDBN} command is @samp{cd}.
15861 @subsubheading Example
15865 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15871 @subheading The @code{-environment-directory} Command
15872 @findex -environment-directory
15874 @subsubheading Synopsis
15877 -environment-directory [ -r ] [ @var{pathdir} ]+
15880 Add directories @var{pathdir} to beginning of search path for source files.
15881 If the @samp{-r} option is used, the search path is reset to the default
15882 search path. If directories @var{pathdir} are supplied in addition to the
15883 @samp{-r} option, the search path is first reset and then addition
15885 Multiple directories may be specified, separated by blanks. Specifying
15886 multiple directories in a single command
15887 results in the directories added to the beginning of the
15888 search path in the same order they were presented in the command.
15889 If blanks are needed as
15890 part of a directory name, double-quotes should be used around
15891 the name. In the command output, the path will show up separated
15892 by the system directory-separator character. The directory-seperator
15893 character must not be used
15894 in any directory name.
15895 If no directories are specified, the current search path is displayed.
15897 @subsubheading @value{GDBN} Command
15899 The corresponding @value{GDBN} command is @samp{dir}.
15901 @subsubheading Example
15905 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15906 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15908 -environment-directory ""
15909 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15911 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15912 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15914 -environment-directory -r
15915 ^done,source-path="$cdir:$cwd"
15920 @subheading The @code{-environment-path} Command
15921 @findex -environment-path
15923 @subsubheading Synopsis
15926 -environment-path [ -r ] [ @var{pathdir} ]+
15929 Add directories @var{pathdir} to beginning of search path for object files.
15930 If the @samp{-r} option is used, the search path is reset to the original
15931 search path that existed at gdb start-up. If directories @var{pathdir} are
15932 supplied in addition to the
15933 @samp{-r} option, the search path is first reset and then addition
15935 Multiple directories may be specified, separated by blanks. Specifying
15936 multiple directories in a single command
15937 results in the directories added to the beginning of the
15938 search path in the same order they were presented in the command.
15939 If blanks are needed as
15940 part of a directory name, double-quotes should be used around
15941 the name. In the command output, the path will show up separated
15942 by the system directory-separator character. The directory-seperator
15943 character must not be used
15944 in any directory name.
15945 If no directories are specified, the current path is displayed.
15948 @subsubheading @value{GDBN} Command
15950 The corresponding @value{GDBN} command is @samp{path}.
15952 @subsubheading Example
15957 ^done,path="/usr/bin"
15959 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15960 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15962 -environment-path -r /usr/local/bin
15963 ^done,path="/usr/local/bin:/usr/bin"
15968 @subheading The @code{-environment-pwd} Command
15969 @findex -environment-pwd
15971 @subsubheading Synopsis
15977 Show the current working directory.
15979 @subsubheading @value{GDBN} command
15981 The corresponding @value{GDBN} command is @samp{pwd}.
15983 @subsubheading Example
15988 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15993 @node GDB/MI Program Control
15994 @section @sc{gdb/mi} Program control
15996 @subsubheading Program termination
15998 As a result of execution, the inferior program can run to completion, if
15999 it doesn't encounter any breakpoints. In this case the output will
16000 include an exit code, if the program has exited exceptionally.
16002 @subsubheading Examples
16005 Program exited normally:
16013 *stopped,reason="exited-normally"
16018 Program exited exceptionally:
16026 *stopped,reason="exited",exit-code="01"
16030 Another way the program can terminate is if it receives a signal such as
16031 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16035 *stopped,reason="exited-signalled",signal-name="SIGINT",
16036 signal-meaning="Interrupt"
16040 @subheading The @code{-exec-abort} Command
16041 @findex -exec-abort
16043 @subsubheading Synopsis
16049 Kill the inferior running program.
16051 @subsubheading @value{GDBN} Command
16053 The corresponding @value{GDBN} command is @samp{kill}.
16055 @subsubheading Example
16059 @subheading The @code{-exec-arguments} Command
16060 @findex -exec-arguments
16062 @subsubheading Synopsis
16065 -exec-arguments @var{args}
16068 Set the inferior program arguments, to be used in the next
16071 @subsubheading @value{GDBN} Command
16073 The corresponding @value{GDBN} command is @samp{set args}.
16075 @subsubheading Example
16078 Don't have one around.
16081 @subheading The @code{-exec-continue} Command
16082 @findex -exec-continue
16084 @subsubheading Synopsis
16090 Asynchronous command. Resumes the execution of the inferior program
16091 until a breakpoint is encountered, or until the inferior exits.
16093 @subsubheading @value{GDBN} Command
16095 The corresponding @value{GDBN} corresponding is @samp{continue}.
16097 @subsubheading Example
16104 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16105 file="hello.c",line="13"@}
16110 @subheading The @code{-exec-finish} Command
16111 @findex -exec-finish
16113 @subsubheading Synopsis
16119 Asynchronous command. Resumes the execution of the inferior program
16120 until the current function is exited. Displays the results returned by
16123 @subsubheading @value{GDBN} Command
16125 The corresponding @value{GDBN} command is @samp{finish}.
16127 @subsubheading Example
16129 Function returning @code{void}.
16136 *stopped,reason="function-finished",frame=@{func="main",args=[],
16137 file="hello.c",line="7"@}
16141 Function returning other than @code{void}. The name of the internal
16142 @value{GDBN} variable storing the result is printed, together with the
16149 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16150 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16151 file="recursive2.c",line="14"@},
16152 gdb-result-var="$1",return-value="0"
16157 @subheading The @code{-exec-interrupt} Command
16158 @findex -exec-interrupt
16160 @subsubheading Synopsis
16166 Asynchronous command. Interrupts the background execution of the target.
16167 Note how the token associated with the stop message is the one for the
16168 execution command that has been interrupted. The token for the interrupt
16169 itself only appears in the @samp{^done} output. If the user is trying to
16170 interrupt a non-running program, an error message will be printed.
16172 @subsubheading @value{GDBN} Command
16174 The corresponding @value{GDBN} command is @samp{interrupt}.
16176 @subsubheading Example
16187 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16188 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16193 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16198 @subheading The @code{-exec-next} Command
16201 @subsubheading Synopsis
16207 Asynchronous command. Resumes execution of the inferior program, stopping
16208 when the beginning of the next source line is reached.
16210 @subsubheading @value{GDBN} Command
16212 The corresponding @value{GDBN} command is @samp{next}.
16214 @subsubheading Example
16220 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16225 @subheading The @code{-exec-next-instruction} Command
16226 @findex -exec-next-instruction
16228 @subsubheading Synopsis
16231 -exec-next-instruction
16234 Asynchronous command. Executes one machine instruction. If the
16235 instruction is a function call continues until the function returns. If
16236 the program stops at an instruction in the middle of a source line, the
16237 address will be printed as well.
16239 @subsubheading @value{GDBN} Command
16241 The corresponding @value{GDBN} command is @samp{nexti}.
16243 @subsubheading Example
16247 -exec-next-instruction
16251 *stopped,reason="end-stepping-range",
16252 addr="0x000100d4",line="5",file="hello.c"
16257 @subheading The @code{-exec-return} Command
16258 @findex -exec-return
16260 @subsubheading Synopsis
16266 Makes current function return immediately. Doesn't execute the inferior.
16267 Displays the new current frame.
16269 @subsubheading @value{GDBN} Command
16271 The corresponding @value{GDBN} command is @samp{return}.
16273 @subsubheading Example
16277 200-break-insert callee4
16278 200^done,bkpt=@{number="1",addr="0x00010734",
16279 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16284 000*stopped,reason="breakpoint-hit",bkptno="1",
16285 frame=@{func="callee4",args=[],
16286 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16292 111^done,frame=@{level="0",func="callee3",
16293 args=[@{name="strarg",
16294 value="0x11940 \"A string argument.\""@}],
16295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16300 @subheading The @code{-exec-run} Command
16303 @subsubheading Synopsis
16309 Asynchronous command. Starts execution of the inferior from the
16310 beginning. The inferior executes until either a breakpoint is
16311 encountered or the program exits.
16313 @subsubheading @value{GDBN} Command
16315 The corresponding @value{GDBN} command is @samp{run}.
16317 @subsubheading Example
16322 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16327 *stopped,reason="breakpoint-hit",bkptno="1",
16328 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16333 @subheading The @code{-exec-show-arguments} Command
16334 @findex -exec-show-arguments
16336 @subsubheading Synopsis
16339 -exec-show-arguments
16342 Print the arguments of the program.
16344 @subsubheading @value{GDBN} Command
16346 The corresponding @value{GDBN} command is @samp{show args}.
16348 @subsubheading Example
16351 @c @subheading -exec-signal
16353 @subheading The @code{-exec-step} Command
16356 @subsubheading Synopsis
16362 Asynchronous command. Resumes execution of the inferior program, stopping
16363 when the beginning of the next source line is reached, if the next
16364 source line is not a function call. If it is, stop at the first
16365 instruction of the called function.
16367 @subsubheading @value{GDBN} Command
16369 The corresponding @value{GDBN} command is @samp{step}.
16371 @subsubheading Example
16373 Stepping into a function:
16379 *stopped,reason="end-stepping-range",
16380 frame=@{func="foo",args=[@{name="a",value="10"@},
16381 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16391 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16396 @subheading The @code{-exec-step-instruction} Command
16397 @findex -exec-step-instruction
16399 @subsubheading Synopsis
16402 -exec-step-instruction
16405 Asynchronous command. Resumes the inferior which executes one machine
16406 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16407 whether we have stopped in the middle of a source line or not. In the
16408 former case, the address at which the program stopped will be printed as
16411 @subsubheading @value{GDBN} Command
16413 The corresponding @value{GDBN} command is @samp{stepi}.
16415 @subsubheading Example
16419 -exec-step-instruction
16423 *stopped,reason="end-stepping-range",
16424 frame=@{func="foo",args=[],file="try.c",line="10"@}
16426 -exec-step-instruction
16430 *stopped,reason="end-stepping-range",
16431 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16436 @subheading The @code{-exec-until} Command
16437 @findex -exec-until
16439 @subsubheading Synopsis
16442 -exec-until [ @var{location} ]
16445 Asynchronous command. Executes the inferior until the @var{location}
16446 specified in the argument is reached. If there is no argument, the inferior
16447 executes until a source line greater than the current one is reached.
16448 The reason for stopping in this case will be @samp{location-reached}.
16450 @subsubheading @value{GDBN} Command
16452 The corresponding @value{GDBN} command is @samp{until}.
16454 @subsubheading Example
16458 -exec-until recursive2.c:6
16462 *stopped,reason="location-reached",frame=@{func="main",args=[],
16463 file="recursive2.c",line="6"@}
16468 @subheading -file-clear
16469 Is this going away????
16473 @subheading The @code{-file-exec-and-symbols} Command
16474 @findex -file-exec-and-symbols
16476 @subsubheading Synopsis
16479 -file-exec-and-symbols @var{file}
16482 Specify the executable file to be debugged. This file is the one from
16483 which the symbol table is also read. If no file is specified, the
16484 command clears the executable and symbol information. If breakpoints
16485 are set when using this command with no arguments, @value{GDBN} will produce
16486 error messages. Otherwise, no output is produced, except a completion
16489 @subsubheading @value{GDBN} Command
16491 The corresponding @value{GDBN} command is @samp{file}.
16493 @subsubheading Example
16497 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16503 @subheading The @code{-file-exec-file} Command
16504 @findex -file-exec-file
16506 @subsubheading Synopsis
16509 -file-exec-file @var{file}
16512 Specify the executable file to be debugged. Unlike
16513 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16514 from this file. If used without argument, @value{GDBN} clears the information
16515 about the executable file. No output is produced, except a completion
16518 @subsubheading @value{GDBN} Command
16520 The corresponding @value{GDBN} command is @samp{exec-file}.
16522 @subsubheading Example
16526 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16532 @subheading The @code{-file-list-exec-sections} Command
16533 @findex -file-list-exec-sections
16535 @subsubheading Synopsis
16538 -file-list-exec-sections
16541 List the sections of the current executable file.
16543 @subsubheading @value{GDBN} Command
16545 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16546 information as this command. @code{gdbtk} has a corresponding command
16547 @samp{gdb_load_info}.
16549 @subsubheading Example
16553 @subheading The @code{-file-list-exec-source-file} Command
16554 @findex -file-list-exec-source-file
16556 @subsubheading Synopsis
16559 -file-list-exec-source-file
16562 List the line number, the current source file, and the absolute path
16563 to the current source file for the current executable.
16565 @subsubheading @value{GDBN} Command
16567 There's no @value{GDBN} command which directly corresponds to this one.
16569 @subsubheading Example
16573 123-file-list-exec-source-file
16574 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16579 @subheading The @code{-file-list-exec-source-files} Command
16580 @findex -file-list-exec-source-files
16582 @subsubheading Synopsis
16585 -file-list-exec-source-files
16588 List the source files for the current executable.
16590 @subsubheading @value{GDBN} Command
16592 There's no @value{GDBN} command which directly corresponds to this one.
16593 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16595 @subsubheading Example
16599 @subheading The @code{-file-list-shared-libraries} Command
16600 @findex -file-list-shared-libraries
16602 @subsubheading Synopsis
16605 -file-list-shared-libraries
16608 List the shared libraries in the program.
16610 @subsubheading @value{GDBN} Command
16612 The corresponding @value{GDBN} command is @samp{info shared}.
16614 @subsubheading Example
16618 @subheading The @code{-file-list-symbol-files} Command
16619 @findex -file-list-symbol-files
16621 @subsubheading Synopsis
16624 -file-list-symbol-files
16629 @subsubheading @value{GDBN} Command
16631 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16633 @subsubheading Example
16637 @subheading The @code{-file-symbol-file} Command
16638 @findex -file-symbol-file
16640 @subsubheading Synopsis
16643 -file-symbol-file @var{file}
16646 Read symbol table info from the specified @var{file} argument. When
16647 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16648 produced, except for a completion notification.
16650 @subsubheading @value{GDBN} Command
16652 The corresponding @value{GDBN} command is @samp{symbol-file}.
16654 @subsubheading Example
16658 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16664 @node GDB/MI Miscellaneous Commands
16665 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16667 @c @subheading -gdb-complete
16669 @subheading The @code{-gdb-exit} Command
16672 @subsubheading Synopsis
16678 Exit @value{GDBN} immediately.
16680 @subsubheading @value{GDBN} Command
16682 Approximately corresponds to @samp{quit}.
16684 @subsubheading Example
16691 @subheading The @code{-gdb-set} Command
16694 @subsubheading Synopsis
16700 Set an internal @value{GDBN} variable.
16701 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16703 @subsubheading @value{GDBN} Command
16705 The corresponding @value{GDBN} command is @samp{set}.
16707 @subsubheading Example
16717 @subheading The @code{-gdb-show} Command
16720 @subsubheading Synopsis
16726 Show the current value of a @value{GDBN} variable.
16728 @subsubheading @value{GDBN} command
16730 The corresponding @value{GDBN} command is @samp{show}.
16732 @subsubheading Example
16741 @c @subheading -gdb-source
16744 @subheading The @code{-gdb-version} Command
16745 @findex -gdb-version
16747 @subsubheading Synopsis
16753 Show version information for @value{GDBN}. Used mostly in testing.
16755 @subsubheading @value{GDBN} Command
16757 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16758 information when you start an interactive session.
16760 @subsubheading Example
16762 @c This example modifies the actual output from GDB to avoid overfull
16768 ~Copyright 2000 Free Software Foundation, Inc.
16769 ~GDB is free software, covered by the GNU General Public License, and
16770 ~you are welcome to change it and/or distribute copies of it under
16771 ~ certain conditions.
16772 ~Type "show copying" to see the conditions.
16773 ~There is absolutely no warranty for GDB. Type "show warranty" for
16775 ~This GDB was configured as
16776 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16781 @subheading The @code{-interpreter-exec} Command
16782 @findex -interpreter-exec
16784 @subheading Synopsis
16787 -interpreter-exec @var{interpreter} @var{command}
16790 Execute the specified @var{command} in the given @var{interpreter}.
16792 @subheading @value{GDBN} Command
16794 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16796 @subheading Example
16800 -interpreter-exec console "break main"
16801 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16802 &"During symbol reading, bad structure-type format.\n"
16803 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16810 @node GDB/MI Kod Commands
16811 @section @sc{gdb/mi} Kod Commands
16813 The Kod commands are not implemented.
16815 @c @subheading -kod-info
16817 @c @subheading -kod-list
16819 @c @subheading -kod-list-object-types
16821 @c @subheading -kod-show
16823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16824 @node GDB/MI Memory Overlay Commands
16825 @section @sc{gdb/mi} Memory Overlay Commands
16827 The memory overlay commands are not implemented.
16829 @c @subheading -overlay-auto
16831 @c @subheading -overlay-list-mapping-state
16833 @c @subheading -overlay-list-overlays
16835 @c @subheading -overlay-map
16837 @c @subheading -overlay-off
16839 @c @subheading -overlay-on
16841 @c @subheading -overlay-unmap
16843 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16844 @node GDB/MI Signal Handling Commands
16845 @section @sc{gdb/mi} Signal Handling Commands
16847 Signal handling commands are not implemented.
16849 @c @subheading -signal-handle
16851 @c @subheading -signal-list-handle-actions
16853 @c @subheading -signal-list-signal-types
16857 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16858 @node GDB/MI Stack Manipulation
16859 @section @sc{gdb/mi} Stack Manipulation Commands
16862 @subheading The @code{-stack-info-frame} Command
16863 @findex -stack-info-frame
16865 @subsubheading Synopsis
16871 Get info on the current frame.
16873 @subsubheading @value{GDBN} Command
16875 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16876 (without arguments).
16878 @subsubheading Example
16881 @subheading The @code{-stack-info-depth} Command
16882 @findex -stack-info-depth
16884 @subsubheading Synopsis
16887 -stack-info-depth [ @var{max-depth} ]
16890 Return the depth of the stack. If the integer argument @var{max-depth}
16891 is specified, do not count beyond @var{max-depth} frames.
16893 @subsubheading @value{GDBN} Command
16895 There's no equivalent @value{GDBN} command.
16897 @subsubheading Example
16899 For a stack with frame levels 0 through 11:
16906 -stack-info-depth 4
16909 -stack-info-depth 12
16912 -stack-info-depth 11
16915 -stack-info-depth 13
16920 @subheading The @code{-stack-list-arguments} Command
16921 @findex -stack-list-arguments
16923 @subsubheading Synopsis
16926 -stack-list-arguments @var{show-values}
16927 [ @var{low-frame} @var{high-frame} ]
16930 Display a list of the arguments for the frames between @var{low-frame}
16931 and @var{high-frame} (inclusive). If @var{low-frame} and
16932 @var{high-frame} are not provided, list the arguments for the whole call
16935 The @var{show-values} argument must have a value of 0 or 1. A value of
16936 0 means that only the names of the arguments are listed, a value of 1
16937 means that both names and values of the arguments are printed.
16939 @subsubheading @value{GDBN} Command
16941 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16942 @samp{gdb_get_args} command which partially overlaps with the
16943 functionality of @samp{-stack-list-arguments}.
16945 @subsubheading Example
16952 frame=@{level="0",addr="0x00010734",func="callee4",
16953 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16954 frame=@{level="1",addr="0x0001076c",func="callee3",
16955 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16956 frame=@{level="2",addr="0x0001078c",func="callee2",
16957 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16958 frame=@{level="3",addr="0x000107b4",func="callee1",
16959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16960 frame=@{level="4",addr="0x000107e0",func="main",
16961 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16963 -stack-list-arguments 0
16966 frame=@{level="0",args=[]@},
16967 frame=@{level="1",args=[name="strarg"]@},
16968 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16969 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16970 frame=@{level="4",args=[]@}]
16972 -stack-list-arguments 1
16975 frame=@{level="0",args=[]@},
16977 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16978 frame=@{level="2",args=[
16979 @{name="intarg",value="2"@},
16980 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16981 @{frame=@{level="3",args=[
16982 @{name="intarg",value="2"@},
16983 @{name="strarg",value="0x11940 \"A string argument.\""@},
16984 @{name="fltarg",value="3.5"@}]@},
16985 frame=@{level="4",args=[]@}]
16987 -stack-list-arguments 0 2 2
16988 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16990 -stack-list-arguments 1 2 2
16991 ^done,stack-args=[frame=@{level="2",
16992 args=[@{name="intarg",value="2"@},
16993 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16997 @c @subheading -stack-list-exception-handlers
17000 @subheading The @code{-stack-list-frames} Command
17001 @findex -stack-list-frames
17003 @subsubheading Synopsis
17006 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17009 List the frames currently on the stack. For each frame it displays the
17014 The frame number, 0 being the topmost frame, i.e. the innermost function.
17016 The @code{$pc} value for that frame.
17020 File name of the source file where the function lives.
17022 Line number corresponding to the @code{$pc}.
17025 If invoked without arguments, this command prints a backtrace for the
17026 whole stack. If given two integer arguments, it shows the frames whose
17027 levels are between the two arguments (inclusive). If the two arguments
17028 are equal, it shows the single frame at the corresponding level.
17030 @subsubheading @value{GDBN} Command
17032 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17034 @subsubheading Example
17036 Full stack backtrace:
17042 [frame=@{level="0",addr="0x0001076c",func="foo",
17043 file="recursive2.c",line="11"@},
17044 frame=@{level="1",addr="0x000107a4",func="foo",
17045 file="recursive2.c",line="14"@},
17046 frame=@{level="2",addr="0x000107a4",func="foo",
17047 file="recursive2.c",line="14"@},
17048 frame=@{level="3",addr="0x000107a4",func="foo",
17049 file="recursive2.c",line="14"@},
17050 frame=@{level="4",addr="0x000107a4",func="foo",
17051 file="recursive2.c",line="14"@},
17052 frame=@{level="5",addr="0x000107a4",func="foo",
17053 file="recursive2.c",line="14"@},
17054 frame=@{level="6",addr="0x000107a4",func="foo",
17055 file="recursive2.c",line="14"@},
17056 frame=@{level="7",addr="0x000107a4",func="foo",
17057 file="recursive2.c",line="14"@},
17058 frame=@{level="8",addr="0x000107a4",func="foo",
17059 file="recursive2.c",line="14"@},
17060 frame=@{level="9",addr="0x000107a4",func="foo",
17061 file="recursive2.c",line="14"@},
17062 frame=@{level="10",addr="0x000107a4",func="foo",
17063 file="recursive2.c",line="14"@},
17064 frame=@{level="11",addr="0x00010738",func="main",
17065 file="recursive2.c",line="4"@}]
17069 Show frames between @var{low_frame} and @var{high_frame}:
17073 -stack-list-frames 3 5
17075 [frame=@{level="3",addr="0x000107a4",func="foo",
17076 file="recursive2.c",line="14"@},
17077 frame=@{level="4",addr="0x000107a4",func="foo",
17078 file="recursive2.c",line="14"@},
17079 frame=@{level="5",addr="0x000107a4",func="foo",
17080 file="recursive2.c",line="14"@}]
17084 Show a single frame:
17088 -stack-list-frames 3 3
17090 [frame=@{level="3",addr="0x000107a4",func="foo",
17091 file="recursive2.c",line="14"@}]
17096 @subheading The @code{-stack-list-locals} Command
17097 @findex -stack-list-locals
17099 @subsubheading Synopsis
17102 -stack-list-locals @var{print-values}
17105 Display the local variable names for the current frame. With an
17106 argument of 0 prints only the names of the variables, with argument of 1
17107 prints also their values.
17109 @subsubheading @value{GDBN} Command
17111 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17113 @subsubheading Example
17117 -stack-list-locals 0
17118 ^done,locals=[name="A",name="B",name="C"]
17120 -stack-list-locals 1
17121 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17122 @{name="C",value="3"@}]
17127 @subheading The @code{-stack-select-frame} Command
17128 @findex -stack-select-frame
17130 @subsubheading Synopsis
17133 -stack-select-frame @var{framenum}
17136 Change the current frame. Select a different frame @var{framenum} on
17139 @subsubheading @value{GDBN} Command
17141 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17142 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17144 @subsubheading Example
17148 -stack-select-frame 2
17153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17154 @node GDB/MI Symbol Query
17155 @section @sc{gdb/mi} Symbol Query Commands
17158 @subheading The @code{-symbol-info-address} Command
17159 @findex -symbol-info-address
17161 @subsubheading Synopsis
17164 -symbol-info-address @var{symbol}
17167 Describe where @var{symbol} is stored.
17169 @subsubheading @value{GDBN} Command
17171 The corresponding @value{GDBN} command is @samp{info address}.
17173 @subsubheading Example
17177 @subheading The @code{-symbol-info-file} Command
17178 @findex -symbol-info-file
17180 @subsubheading Synopsis
17186 Show the file for the symbol.
17188 @subsubheading @value{GDBN} Command
17190 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17191 @samp{gdb_find_file}.
17193 @subsubheading Example
17197 @subheading The @code{-symbol-info-function} Command
17198 @findex -symbol-info-function
17200 @subsubheading Synopsis
17203 -symbol-info-function
17206 Show which function the symbol lives in.
17208 @subsubheading @value{GDBN} Command
17210 @samp{gdb_get_function} in @code{gdbtk}.
17212 @subsubheading Example
17216 @subheading The @code{-symbol-info-line} Command
17217 @findex -symbol-info-line
17219 @subsubheading Synopsis
17225 Show the core addresses of the code for a source line.
17227 @subsubheading @value{GDBN} Command
17229 The corresponding @value{GDBN} command is @samp{info line}.
17230 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17232 @subsubheading Example
17236 @subheading The @code{-symbol-info-symbol} Command
17237 @findex -symbol-info-symbol
17239 @subsubheading Synopsis
17242 -symbol-info-symbol @var{addr}
17245 Describe what symbol is at location @var{addr}.
17247 @subsubheading @value{GDBN} Command
17249 The corresponding @value{GDBN} command is @samp{info symbol}.
17251 @subsubheading Example
17255 @subheading The @code{-symbol-list-functions} Command
17256 @findex -symbol-list-functions
17258 @subsubheading Synopsis
17261 -symbol-list-functions
17264 List the functions in the executable.
17266 @subsubheading @value{GDBN} Command
17268 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17269 @samp{gdb_search} in @code{gdbtk}.
17271 @subsubheading Example
17275 @subheading The @code{-symbol-list-lines} Command
17276 @findex -symbol-list-lines
17278 @subsubheading Synopsis
17281 -symbol-list-lines @var{filename}
17284 Print the list of lines that contain code and their associated program
17285 addresses for the given source filename. The entries are sorted in
17286 ascending PC order.
17288 @subsubheading @value{GDBN} Command
17290 There is no corresponding @value{GDBN} command.
17292 @subsubheading Example
17295 -symbol-list-lines basics.c
17296 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17301 @subheading The @code{-symbol-list-types} Command
17302 @findex -symbol-list-types
17304 @subsubheading Synopsis
17310 List all the type names.
17312 @subsubheading @value{GDBN} Command
17314 The corresponding commands are @samp{info types} in @value{GDBN},
17315 @samp{gdb_search} in @code{gdbtk}.
17317 @subsubheading Example
17321 @subheading The @code{-symbol-list-variables} Command
17322 @findex -symbol-list-variables
17324 @subsubheading Synopsis
17327 -symbol-list-variables
17330 List all the global and static variable names.
17332 @subsubheading @value{GDBN} Command
17334 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17336 @subsubheading Example
17340 @subheading The @code{-symbol-locate} Command
17341 @findex -symbol-locate
17343 @subsubheading Synopsis
17349 @subsubheading @value{GDBN} Command
17351 @samp{gdb_loc} in @code{gdbtk}.
17353 @subsubheading Example
17357 @subheading The @code{-symbol-type} Command
17358 @findex -symbol-type
17360 @subsubheading Synopsis
17363 -symbol-type @var{variable}
17366 Show type of @var{variable}.
17368 @subsubheading @value{GDBN} Command
17370 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17371 @samp{gdb_obj_variable}.
17373 @subsubheading Example
17377 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17378 @node GDB/MI Target Manipulation
17379 @section @sc{gdb/mi} Target Manipulation Commands
17382 @subheading The @code{-target-attach} Command
17383 @findex -target-attach
17385 @subsubheading Synopsis
17388 -target-attach @var{pid} | @var{file}
17391 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17393 @subsubheading @value{GDBN} command
17395 The corresponding @value{GDBN} command is @samp{attach}.
17397 @subsubheading Example
17401 @subheading The @code{-target-compare-sections} Command
17402 @findex -target-compare-sections
17404 @subsubheading Synopsis
17407 -target-compare-sections [ @var{section} ]
17410 Compare data of section @var{section} on target to the exec file.
17411 Without the argument, all sections are compared.
17413 @subsubheading @value{GDBN} Command
17415 The @value{GDBN} equivalent is @samp{compare-sections}.
17417 @subsubheading Example
17421 @subheading The @code{-target-detach} Command
17422 @findex -target-detach
17424 @subsubheading Synopsis
17430 Disconnect from the remote target. There's no output.
17432 @subsubheading @value{GDBN} command
17434 The corresponding @value{GDBN} command is @samp{detach}.
17436 @subsubheading Example
17446 @subheading The @code{-target-disconnect} Command
17447 @findex -target-disconnect
17449 @subsubheading Synopsis
17455 Disconnect from the remote target. There's no output.
17457 @subsubheading @value{GDBN} command
17459 The corresponding @value{GDBN} command is @samp{disconnect}.
17461 @subsubheading Example
17471 @subheading The @code{-target-download} Command
17472 @findex -target-download
17474 @subsubheading Synopsis
17480 Loads the executable onto the remote target.
17481 It prints out an update message every half second, which includes the fields:
17485 The name of the section.
17487 The size of what has been sent so far for that section.
17489 The size of the section.
17491 The total size of what was sent so far (the current and the previous sections).
17493 The size of the overall executable to download.
17497 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17498 @sc{gdb/mi} Output Syntax}).
17500 In addition, it prints the name and size of the sections, as they are
17501 downloaded. These messages include the following fields:
17505 The name of the section.
17507 The size of the section.
17509 The size of the overall executable to download.
17513 At the end, a summary is printed.
17515 @subsubheading @value{GDBN} Command
17517 The corresponding @value{GDBN} command is @samp{load}.
17519 @subsubheading Example
17521 Note: each status message appears on a single line. Here the messages
17522 have been broken down so that they can fit onto a page.
17527 +download,@{section=".text",section-size="6668",total-size="9880"@}
17528 +download,@{section=".text",section-sent="512",section-size="6668",
17529 total-sent="512",total-size="9880"@}
17530 +download,@{section=".text",section-sent="1024",section-size="6668",
17531 total-sent="1024",total-size="9880"@}
17532 +download,@{section=".text",section-sent="1536",section-size="6668",
17533 total-sent="1536",total-size="9880"@}
17534 +download,@{section=".text",section-sent="2048",section-size="6668",
17535 total-sent="2048",total-size="9880"@}
17536 +download,@{section=".text",section-sent="2560",section-size="6668",
17537 total-sent="2560",total-size="9880"@}
17538 +download,@{section=".text",section-sent="3072",section-size="6668",
17539 total-sent="3072",total-size="9880"@}
17540 +download,@{section=".text",section-sent="3584",section-size="6668",
17541 total-sent="3584",total-size="9880"@}
17542 +download,@{section=".text",section-sent="4096",section-size="6668",
17543 total-sent="4096",total-size="9880"@}
17544 +download,@{section=".text",section-sent="4608",section-size="6668",
17545 total-sent="4608",total-size="9880"@}
17546 +download,@{section=".text",section-sent="5120",section-size="6668",
17547 total-sent="5120",total-size="9880"@}
17548 +download,@{section=".text",section-sent="5632",section-size="6668",
17549 total-sent="5632",total-size="9880"@}
17550 +download,@{section=".text",section-sent="6144",section-size="6668",
17551 total-sent="6144",total-size="9880"@}
17552 +download,@{section=".text",section-sent="6656",section-size="6668",
17553 total-sent="6656",total-size="9880"@}
17554 +download,@{section=".init",section-size="28",total-size="9880"@}
17555 +download,@{section=".fini",section-size="28",total-size="9880"@}
17556 +download,@{section=".data",section-size="3156",total-size="9880"@}
17557 +download,@{section=".data",section-sent="512",section-size="3156",
17558 total-sent="7236",total-size="9880"@}
17559 +download,@{section=".data",section-sent="1024",section-size="3156",
17560 total-sent="7748",total-size="9880"@}
17561 +download,@{section=".data",section-sent="1536",section-size="3156",
17562 total-sent="8260",total-size="9880"@}
17563 +download,@{section=".data",section-sent="2048",section-size="3156",
17564 total-sent="8772",total-size="9880"@}
17565 +download,@{section=".data",section-sent="2560",section-size="3156",
17566 total-sent="9284",total-size="9880"@}
17567 +download,@{section=".data",section-sent="3072",section-size="3156",
17568 total-sent="9796",total-size="9880"@}
17569 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17575 @subheading The @code{-target-exec-status} Command
17576 @findex -target-exec-status
17578 @subsubheading Synopsis
17581 -target-exec-status
17584 Provide information on the state of the target (whether it is running or
17585 not, for instance).
17587 @subsubheading @value{GDBN} Command
17589 There's no equivalent @value{GDBN} command.
17591 @subsubheading Example
17595 @subheading The @code{-target-list-available-targets} Command
17596 @findex -target-list-available-targets
17598 @subsubheading Synopsis
17601 -target-list-available-targets
17604 List the possible targets to connect to.
17606 @subsubheading @value{GDBN} Command
17608 The corresponding @value{GDBN} command is @samp{help target}.
17610 @subsubheading Example
17614 @subheading The @code{-target-list-current-targets} Command
17615 @findex -target-list-current-targets
17617 @subsubheading Synopsis
17620 -target-list-current-targets
17623 Describe the current target.
17625 @subsubheading @value{GDBN} Command
17627 The corresponding information is printed by @samp{info file} (among
17630 @subsubheading Example
17634 @subheading The @code{-target-list-parameters} Command
17635 @findex -target-list-parameters
17637 @subsubheading Synopsis
17640 -target-list-parameters
17645 @subsubheading @value{GDBN} Command
17649 @subsubheading Example
17653 @subheading The @code{-target-select} Command
17654 @findex -target-select
17656 @subsubheading Synopsis
17659 -target-select @var{type} @var{parameters @dots{}}
17662 Connect @value{GDBN} to the remote target. This command takes two args:
17666 The type of target, for instance @samp{async}, @samp{remote}, etc.
17667 @item @var{parameters}
17668 Device names, host names and the like. @xref{Target Commands, ,
17669 Commands for managing targets}, for more details.
17672 The output is a connection notification, followed by the address at
17673 which the target program is, in the following form:
17676 ^connected,addr="@var{address}",func="@var{function name}",
17677 args=[@var{arg list}]
17680 @subsubheading @value{GDBN} Command
17682 The corresponding @value{GDBN} command is @samp{target}.
17684 @subsubheading Example
17688 -target-select async /dev/ttya
17689 ^connected,addr="0xfe00a300",func="??",args=[]
17693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17694 @node GDB/MI Thread Commands
17695 @section @sc{gdb/mi} Thread Commands
17698 @subheading The @code{-thread-info} Command
17699 @findex -thread-info
17701 @subsubheading Synopsis
17707 @subsubheading @value{GDBN} command
17711 @subsubheading Example
17715 @subheading The @code{-thread-list-all-threads} Command
17716 @findex -thread-list-all-threads
17718 @subsubheading Synopsis
17721 -thread-list-all-threads
17724 @subsubheading @value{GDBN} Command
17726 The equivalent @value{GDBN} command is @samp{info threads}.
17728 @subsubheading Example
17732 @subheading The @code{-thread-list-ids} Command
17733 @findex -thread-list-ids
17735 @subsubheading Synopsis
17741 Produces a list of the currently known @value{GDBN} thread ids. At the
17742 end of the list it also prints the total number of such threads.
17744 @subsubheading @value{GDBN} Command
17746 Part of @samp{info threads} supplies the same information.
17748 @subsubheading Example
17750 No threads present, besides the main process:
17755 ^done,thread-ids=@{@},number-of-threads="0"
17765 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17766 number-of-threads="3"
17771 @subheading The @code{-thread-select} Command
17772 @findex -thread-select
17774 @subsubheading Synopsis
17777 -thread-select @var{threadnum}
17780 Make @var{threadnum} the current thread. It prints the number of the new
17781 current thread, and the topmost frame for that thread.
17783 @subsubheading @value{GDBN} Command
17785 The corresponding @value{GDBN} command is @samp{thread}.
17787 @subsubheading Example
17794 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17795 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17799 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17800 number-of-threads="3"
17803 ^done,new-thread-id="3",
17804 frame=@{level="0",func="vprintf",
17805 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17806 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17810 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17811 @node GDB/MI Tracepoint Commands
17812 @section @sc{gdb/mi} Tracepoint Commands
17814 The tracepoint commands are not yet implemented.
17816 @c @subheading -trace-actions
17818 @c @subheading -trace-delete
17820 @c @subheading -trace-disable
17822 @c @subheading -trace-dump
17824 @c @subheading -trace-enable
17826 @c @subheading -trace-exists
17828 @c @subheading -trace-find
17830 @c @subheading -trace-frame-number
17832 @c @subheading -trace-info
17834 @c @subheading -trace-insert
17836 @c @subheading -trace-list
17838 @c @subheading -trace-pass-count
17840 @c @subheading -trace-save
17842 @c @subheading -trace-start
17844 @c @subheading -trace-stop
17847 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17848 @node GDB/MI Variable Objects
17849 @section @sc{gdb/mi} Variable Objects
17852 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17854 For the implementation of a variable debugger window (locals, watched
17855 expressions, etc.), we are proposing the adaptation of the existing code
17856 used by @code{Insight}.
17858 The two main reasons for that are:
17862 It has been proven in practice (it is already on its second generation).
17865 It will shorten development time (needless to say how important it is
17869 The original interface was designed to be used by Tcl code, so it was
17870 slightly changed so it could be used through @sc{gdb/mi}. This section
17871 describes the @sc{gdb/mi} operations that will be available and gives some
17872 hints about their use.
17874 @emph{Note}: In addition to the set of operations described here, we
17875 expect the @sc{gui} implementation of a variable window to require, at
17876 least, the following operations:
17879 @item @code{-gdb-show} @code{output-radix}
17880 @item @code{-stack-list-arguments}
17881 @item @code{-stack-list-locals}
17882 @item @code{-stack-select-frame}
17885 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17887 @cindex variable objects in @sc{gdb/mi}
17888 The basic idea behind variable objects is the creation of a named object
17889 to represent a variable, an expression, a memory location or even a CPU
17890 register. For each object created, a set of operations is available for
17891 examining or changing its properties.
17893 Furthermore, complex data types, such as C structures, are represented
17894 in a tree format. For instance, the @code{struct} type variable is the
17895 root and the children will represent the struct members. If a child
17896 is itself of a complex type, it will also have children of its own.
17897 Appropriate language differences are handled for C, C@t{++} and Java.
17899 When returning the actual values of the objects, this facility allows
17900 for the individual selection of the display format used in the result
17901 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17902 and natural. Natural refers to a default format automatically
17903 chosen based on the variable type (like decimal for an @code{int}, hex
17904 for pointers, etc.).
17906 The following is the complete set of @sc{gdb/mi} operations defined to
17907 access this functionality:
17909 @multitable @columnfractions .4 .6
17910 @item @strong{Operation}
17911 @tab @strong{Description}
17913 @item @code{-var-create}
17914 @tab create a variable object
17915 @item @code{-var-delete}
17916 @tab delete the variable object and its children
17917 @item @code{-var-set-format}
17918 @tab set the display format of this variable
17919 @item @code{-var-show-format}
17920 @tab show the display format of this variable
17921 @item @code{-var-info-num-children}
17922 @tab tells how many children this object has
17923 @item @code{-var-list-children}
17924 @tab return a list of the object's children
17925 @item @code{-var-info-type}
17926 @tab show the type of this variable object
17927 @item @code{-var-info-expression}
17928 @tab print what this variable object represents
17929 @item @code{-var-show-attributes}
17930 @tab is this variable editable? does it exist here?
17931 @item @code{-var-evaluate-expression}
17932 @tab get the value of this variable
17933 @item @code{-var-assign}
17934 @tab set the value of this variable
17935 @item @code{-var-update}
17936 @tab update the variable and its children
17939 In the next subsection we describe each operation in detail and suggest
17940 how it can be used.
17942 @subheading Description And Use of Operations on Variable Objects
17944 @subheading The @code{-var-create} Command
17945 @findex -var-create
17947 @subsubheading Synopsis
17950 -var-create @{@var{name} | "-"@}
17951 @{@var{frame-addr} | "*"@} @var{expression}
17954 This operation creates a variable object, which allows the monitoring of
17955 a variable, the result of an expression, a memory cell or a CPU
17958 The @var{name} parameter is the string by which the object can be
17959 referenced. It must be unique. If @samp{-} is specified, the varobj
17960 system will generate a string ``varNNNNNN'' automatically. It will be
17961 unique provided that one does not specify @var{name} on that format.
17962 The command fails if a duplicate name is found.
17964 The frame under which the expression should be evaluated can be
17965 specified by @var{frame-addr}. A @samp{*} indicates that the current
17966 frame should be used.
17968 @var{expression} is any expression valid on the current language set (must not
17969 begin with a @samp{*}), or one of the following:
17973 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17976 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17979 @samp{$@var{regname}} --- a CPU register name
17982 @subsubheading Result
17984 This operation returns the name, number of children and the type of the
17985 object created. Type is returned as a string as the ones generated by
17986 the @value{GDBN} CLI:
17989 name="@var{name}",numchild="N",type="@var{type}"
17993 @subheading The @code{-var-delete} Command
17994 @findex -var-delete
17996 @subsubheading Synopsis
17999 -var-delete @var{name}
18002 Deletes a previously created variable object and all of its children.
18004 Returns an error if the object @var{name} is not found.
18007 @subheading The @code{-var-set-format} Command
18008 @findex -var-set-format
18010 @subsubheading Synopsis
18013 -var-set-format @var{name} @var{format-spec}
18016 Sets the output format for the value of the object @var{name} to be
18019 The syntax for the @var{format-spec} is as follows:
18022 @var{format-spec} @expansion{}
18023 @{binary | decimal | hexadecimal | octal | natural@}
18027 @subheading The @code{-var-show-format} Command
18028 @findex -var-show-format
18030 @subsubheading Synopsis
18033 -var-show-format @var{name}
18036 Returns the format used to display the value of the object @var{name}.
18039 @var{format} @expansion{}
18044 @subheading The @code{-var-info-num-children} Command
18045 @findex -var-info-num-children
18047 @subsubheading Synopsis
18050 -var-info-num-children @var{name}
18053 Returns the number of children of a variable object @var{name}:
18060 @subheading The @code{-var-list-children} Command
18061 @findex -var-list-children
18063 @subsubheading Synopsis
18066 -var-list-children @var{name}
18069 Returns a list of the children of the specified variable object:
18072 numchild=@var{n},children=[@{name=@var{name},
18073 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18077 @subheading The @code{-var-info-type} Command
18078 @findex -var-info-type
18080 @subsubheading Synopsis
18083 -var-info-type @var{name}
18086 Returns the type of the specified variable @var{name}. The type is
18087 returned as a string in the same format as it is output by the
18091 type=@var{typename}
18095 @subheading The @code{-var-info-expression} Command
18096 @findex -var-info-expression
18098 @subsubheading Synopsis
18101 -var-info-expression @var{name}
18104 Returns what is represented by the variable object @var{name}:
18107 lang=@var{lang-spec},exp=@var{expression}
18111 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18113 @subheading The @code{-var-show-attributes} Command
18114 @findex -var-show-attributes
18116 @subsubheading Synopsis
18119 -var-show-attributes @var{name}
18122 List attributes of the specified variable object @var{name}:
18125 status=@var{attr} [ ( ,@var{attr} )* ]
18129 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18131 @subheading The @code{-var-evaluate-expression} Command
18132 @findex -var-evaluate-expression
18134 @subsubheading Synopsis
18137 -var-evaluate-expression @var{name}
18140 Evaluates the expression that is represented by the specified variable
18141 object and returns its value as a string in the current format specified
18148 Note that one must invoke @code{-var-list-children} for a variable
18149 before the value of a child variable can be evaluated.
18151 @subheading The @code{-var-assign} Command
18152 @findex -var-assign
18154 @subsubheading Synopsis
18157 -var-assign @var{name} @var{expression}
18160 Assigns the value of @var{expression} to the variable object specified
18161 by @var{name}. The object must be @samp{editable}. If the variable's
18162 value is altered by the assign, the variable will show up in any
18163 subsequent @code{-var-update} list.
18165 @subsubheading Example
18173 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18177 @subheading The @code{-var-update} Command
18178 @findex -var-update
18180 @subsubheading Synopsis
18183 -var-update @{@var{name} | "*"@}
18186 Update the value of the variable object @var{name} by evaluating its
18187 expression after fetching all the new values from memory or registers.
18188 A @samp{*} causes all existing variable objects to be updated.
18192 @chapter @value{GDBN} Annotations
18194 This chapter describes annotations in @value{GDBN}. Annotations were
18195 designed to interface @value{GDBN} to graphical user interfaces or other
18196 similar programs which want to interact with @value{GDBN} at a
18197 relatively high level.
18199 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18203 This is Edition @value{EDITION}, @value{DATE}.
18207 * Annotations Overview:: What annotations are; the general syntax.
18208 * Server Prefix:: Issuing a command without affecting user state.
18209 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18210 * Errors:: Annotations for error messages.
18211 * Invalidation:: Some annotations describe things now invalid.
18212 * Annotations for Running::
18213 Whether the program is running, how it stopped, etc.
18214 * Source Annotations:: Annotations describing source code.
18217 @node Annotations Overview
18218 @section What is an Annotation?
18219 @cindex annotations
18221 Annotations start with a newline character, two @samp{control-z}
18222 characters, and the name of the annotation. If there is no additional
18223 information associated with this annotation, the name of the annotation
18224 is followed immediately by a newline. If there is additional
18225 information, the name of the annotation is followed by a space, the
18226 additional information, and a newline. The additional information
18227 cannot contain newline characters.
18229 Any output not beginning with a newline and two @samp{control-z}
18230 characters denotes literal output from @value{GDBN}. Currently there is
18231 no need for @value{GDBN} to output a newline followed by two
18232 @samp{control-z} characters, but if there was such a need, the
18233 annotations could be extended with an @samp{escape} annotation which
18234 means those three characters as output.
18236 The annotation @var{level}, which is specified using the
18237 @option{--annotate} command line option (@pxref{Mode Options}), controls
18238 how much information @value{GDBN} prints together with its prompt,
18239 values of expressions, source lines, and other types of output. Level 0
18240 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18241 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18242 for programs that control @value{GDBN}, and level 2 annotations have
18243 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18244 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18245 describes level 3 annotations.
18247 A simple example of starting up @value{GDBN} with annotations is:
18250 $ @kbd{gdb --annotate=3}
18252 Copyright 2003 Free Software Foundation, Inc.
18253 GDB is free software, covered by the GNU General Public License,
18254 and you are welcome to change it and/or distribute copies of it
18255 under certain conditions.
18256 Type "show copying" to see the conditions.
18257 There is absolutely no warranty for GDB. Type "show warranty"
18259 This GDB was configured as "i386-pc-linux-gnu"
18270 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18271 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18272 denotes a @samp{control-z} character) are annotations; the rest is
18273 output from @value{GDBN}.
18275 @node Server Prefix
18276 @section The Server Prefix
18277 @cindex server prefix for annotations
18279 To issue a command to @value{GDBN} without affecting certain aspects of
18280 the state which is seen by users, prefix it with @samp{server }. This
18281 means that this command will not affect the command history, nor will it
18282 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18283 pressed on a line by itself.
18285 The server prefix does not affect the recording of values into the value
18286 history; to print a value without recording it into the value history,
18287 use the @code{output} command instead of the @code{print} command.
18290 @section Annotation for @value{GDBN} Input
18292 @cindex annotations for prompts
18293 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18294 to know when to send output, when the output from a given command is
18297 Different kinds of input each have a different @dfn{input type}. Each
18298 input type has three annotations: a @code{pre-} annotation, which
18299 denotes the beginning of any prompt which is being output, a plain
18300 annotation, which denotes the end of the prompt, and then a @code{post-}
18301 annotation which denotes the end of any echo which may (or may not) be
18302 associated with the input. For example, the @code{prompt} input type
18303 features the following annotations:
18311 The input types are
18316 @findex post-prompt
18318 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18320 @findex pre-commands
18322 @findex post-commands
18324 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18325 command. The annotations are repeated for each command which is input.
18327 @findex pre-overload-choice
18328 @findex overload-choice
18329 @findex post-overload-choice
18330 @item overload-choice
18331 When @value{GDBN} wants the user to select between various overloaded functions.
18337 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18339 @findex pre-prompt-for-continue
18340 @findex prompt-for-continue
18341 @findex post-prompt-for-continue
18342 @item prompt-for-continue
18343 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18344 expect this to work well; instead use @code{set height 0} to disable
18345 prompting. This is because the counting of lines is buggy in the
18346 presence of annotations.
18351 @cindex annotations for errors, warnings and interrupts
18358 This annotation occurs right before @value{GDBN} responds to an interrupt.
18365 This annotation occurs right before @value{GDBN} responds to an error.
18367 Quit and error annotations indicate that any annotations which @value{GDBN} was
18368 in the middle of may end abruptly. For example, if a
18369 @code{value-history-begin} annotation is followed by a @code{error}, one
18370 cannot expect to receive the matching @code{value-history-end}. One
18371 cannot expect not to receive it either, however; an error annotation
18372 does not necessarily mean that @value{GDBN} is immediately returning all the way
18375 @findex error-begin
18376 A quit or error annotation may be preceded by
18382 Any output between that and the quit or error annotation is the error
18385 Warning messages are not yet annotated.
18386 @c If we want to change that, need to fix warning(), type_error(),
18387 @c range_error(), and possibly other places.
18390 @section Invalidation Notices
18392 @cindex annotations for invalidation messages
18393 The following annotations say that certain pieces of state may have
18397 @findex frames-invalid
18398 @item ^Z^Zframes-invalid
18400 The frames (for example, output from the @code{backtrace} command) may
18403 @findex breakpoints-invalid
18404 @item ^Z^Zbreakpoints-invalid
18406 The breakpoints may have changed. For example, the user just added or
18407 deleted a breakpoint.
18410 @node Annotations for Running
18411 @section Running the Program
18412 @cindex annotations for running programs
18416 When the program starts executing due to a @value{GDBN} command such as
18417 @code{step} or @code{continue},
18423 is output. When the program stops,
18429 is output. Before the @code{stopped} annotation, a variety of
18430 annotations describe how the program stopped.
18434 @item ^Z^Zexited @var{exit-status}
18435 The program exited, and @var{exit-status} is the exit status (zero for
18436 successful exit, otherwise nonzero).
18439 @findex signal-name
18440 @findex signal-name-end
18441 @findex signal-string
18442 @findex signal-string-end
18443 @item ^Z^Zsignalled
18444 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18445 annotation continues:
18451 ^Z^Zsignal-name-end
18455 ^Z^Zsignal-string-end
18460 where @var{name} is the name of the signal, such as @code{SIGILL} or
18461 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18462 as @code{Illegal Instruction} or @code{Segmentation fault}.
18463 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18464 user's benefit and have no particular format.
18468 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18469 just saying that the program received the signal, not that it was
18470 terminated with it.
18473 @item ^Z^Zbreakpoint @var{number}
18474 The program hit breakpoint number @var{number}.
18477 @item ^Z^Zwatchpoint @var{number}
18478 The program hit watchpoint number @var{number}.
18481 @node Source Annotations
18482 @section Displaying Source
18483 @cindex annotations for source display
18486 The following annotation is used instead of displaying source code:
18489 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18492 where @var{filename} is an absolute file name indicating which source
18493 file, @var{line} is the line number within that file (where 1 is the
18494 first line in the file), @var{character} is the character position
18495 within the file (where 0 is the first character in the file) (for most
18496 debug formats this will necessarily point to the beginning of a line),
18497 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18498 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18499 @var{addr} is the address in the target program associated with the
18500 source which is being displayed. @var{addr} is in the form @samp{0x}
18501 followed by one or more lowercase hex digits (note that this does not
18502 depend on the language).
18505 @chapter Reporting Bugs in @value{GDBN}
18506 @cindex bugs in @value{GDBN}
18507 @cindex reporting bugs in @value{GDBN}
18509 Your bug reports play an essential role in making @value{GDBN} reliable.
18511 Reporting a bug may help you by bringing a solution to your problem, or it
18512 may not. But in any case the principal function of a bug report is to help
18513 the entire community by making the next version of @value{GDBN} work better. Bug
18514 reports are your contribution to the maintenance of @value{GDBN}.
18516 In order for a bug report to serve its purpose, you must include the
18517 information that enables us to fix the bug.
18520 * Bug Criteria:: Have you found a bug?
18521 * Bug Reporting:: How to report bugs
18525 @section Have you found a bug?
18526 @cindex bug criteria
18528 If you are not sure whether you have found a bug, here are some guidelines:
18531 @cindex fatal signal
18532 @cindex debugger crash
18533 @cindex crash of debugger
18535 If the debugger gets a fatal signal, for any input whatever, that is a
18536 @value{GDBN} bug. Reliable debuggers never crash.
18538 @cindex error on valid input
18540 If @value{GDBN} produces an error message for valid input, that is a
18541 bug. (Note that if you're cross debugging, the problem may also be
18542 somewhere in the connection to the target.)
18544 @cindex invalid input
18546 If @value{GDBN} does not produce an error message for invalid input,
18547 that is a bug. However, you should note that your idea of
18548 ``invalid input'' might be our idea of ``an extension'' or ``support
18549 for traditional practice''.
18552 If you are an experienced user of debugging tools, your suggestions
18553 for improvement of @value{GDBN} are welcome in any case.
18556 @node Bug Reporting
18557 @section How to report bugs
18558 @cindex bug reports
18559 @cindex @value{GDBN} bugs, reporting
18561 A number of companies and individuals offer support for @sc{gnu} products.
18562 If you obtained @value{GDBN} from a support organization, we recommend you
18563 contact that organization first.
18565 You can find contact information for many support companies and
18566 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18568 @c should add a web page ref...
18570 In any event, we also recommend that you submit bug reports for
18571 @value{GDBN}. The prefered method is to submit them directly using
18572 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18573 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18576 @strong{Do not send bug reports to @samp{info-gdb}, or to
18577 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18578 not want to receive bug reports. Those that do have arranged to receive
18581 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18582 serves as a repeater. The mailing list and the newsgroup carry exactly
18583 the same messages. Often people think of posting bug reports to the
18584 newsgroup instead of mailing them. This appears to work, but it has one
18585 problem which can be crucial: a newsgroup posting often lacks a mail
18586 path back to the sender. Thus, if we need to ask for more information,
18587 we may be unable to reach you. For this reason, it is better to send
18588 bug reports to the mailing list.
18590 The fundamental principle of reporting bugs usefully is this:
18591 @strong{report all the facts}. If you are not sure whether to state a
18592 fact or leave it out, state it!
18594 Often people omit facts because they think they know what causes the
18595 problem and assume that some details do not matter. Thus, you might
18596 assume that the name of the variable you use in an example does not matter.
18597 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18598 stray memory reference which happens to fetch from the location where that
18599 name is stored in memory; perhaps, if the name were different, the contents
18600 of that location would fool the debugger into doing the right thing despite
18601 the bug. Play it safe and give a specific, complete example. That is the
18602 easiest thing for you to do, and the most helpful.
18604 Keep in mind that the purpose of a bug report is to enable us to fix the
18605 bug. It may be that the bug has been reported previously, but neither
18606 you nor we can know that unless your bug report is complete and
18609 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18610 bell?'' Those bug reports are useless, and we urge everyone to
18611 @emph{refuse to respond to them} except to chide the sender to report
18614 To enable us to fix the bug, you should include all these things:
18618 The version of @value{GDBN}. @value{GDBN} announces it if you start
18619 with no arguments; you can also print it at any time using @code{show
18622 Without this, we will not know whether there is any point in looking for
18623 the bug in the current version of @value{GDBN}.
18626 The type of machine you are using, and the operating system name and
18630 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18631 ``@value{GCC}--2.8.1''.
18634 What compiler (and its version) was used to compile the program you are
18635 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18636 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18637 information; for other compilers, see the documentation for those
18641 The command arguments you gave the compiler to compile your example and
18642 observe the bug. For example, did you use @samp{-O}? To guarantee
18643 you will not omit something important, list them all. A copy of the
18644 Makefile (or the output from make) is sufficient.
18646 If we were to try to guess the arguments, we would probably guess wrong
18647 and then we might not encounter the bug.
18650 A complete input script, and all necessary source files, that will
18654 A description of what behavior you observe that you believe is
18655 incorrect. For example, ``It gets a fatal signal.''
18657 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18658 will certainly notice it. But if the bug is incorrect output, we might
18659 not notice unless it is glaringly wrong. You might as well not give us
18660 a chance to make a mistake.
18662 Even if the problem you experience is a fatal signal, you should still
18663 say so explicitly. Suppose something strange is going on, such as, your
18664 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18665 the C library on your system. (This has happened!) Your copy might
18666 crash and ours would not. If you told us to expect a crash, then when
18667 ours fails to crash, we would know that the bug was not happening for
18668 us. If you had not told us to expect a crash, then we would not be able
18669 to draw any conclusion from our observations.
18672 If you wish to suggest changes to the @value{GDBN} source, send us context
18673 diffs. If you even discuss something in the @value{GDBN} source, refer to
18674 it by context, not by line number.
18676 The line numbers in our development sources will not match those in your
18677 sources. Your line numbers would convey no useful information to us.
18681 Here are some things that are not necessary:
18685 A description of the envelope of the bug.
18687 Often people who encounter a bug spend a lot of time investigating
18688 which changes to the input file will make the bug go away and which
18689 changes will not affect it.
18691 This is often time consuming and not very useful, because the way we
18692 will find the bug is by running a single example under the debugger
18693 with breakpoints, not by pure deduction from a series of examples.
18694 We recommend that you save your time for something else.
18696 Of course, if you can find a simpler example to report @emph{instead}
18697 of the original one, that is a convenience for us. Errors in the
18698 output will be easier to spot, running under the debugger will take
18699 less time, and so on.
18701 However, simplification is not vital; if you do not want to do this,
18702 report the bug anyway and send us the entire test case you used.
18705 A patch for the bug.
18707 A patch for the bug does help us if it is a good one. But do not omit
18708 the necessary information, such as the test case, on the assumption that
18709 a patch is all we need. We might see problems with your patch and decide
18710 to fix the problem another way, or we might not understand it at all.
18712 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18713 construct an example that will make the program follow a certain path
18714 through the code. If you do not send us the example, we will not be able
18715 to construct one, so we will not be able to verify that the bug is fixed.
18717 And if we cannot understand what bug you are trying to fix, or why your
18718 patch should be an improvement, we will not install it. A test case will
18719 help us to understand.
18722 A guess about what the bug is or what it depends on.
18724 Such guesses are usually wrong. Even we cannot guess right about such
18725 things without first using the debugger to find the facts.
18728 @c The readline documentation is distributed with the readline code
18729 @c and consists of the two following files:
18731 @c inc-hist.texinfo
18732 @c Use -I with makeinfo to point to the appropriate directory,
18733 @c environment var TEXINPUTS with TeX.
18734 @include rluser.texinfo
18735 @include inc-hist.texinfo
18738 @node Formatting Documentation
18739 @appendix Formatting Documentation
18741 @cindex @value{GDBN} reference card
18742 @cindex reference card
18743 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18744 for printing with PostScript or Ghostscript, in the @file{gdb}
18745 subdirectory of the main source directory@footnote{In
18746 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18747 release.}. If you can use PostScript or Ghostscript with your printer,
18748 you can print the reference card immediately with @file{refcard.ps}.
18750 The release also includes the source for the reference card. You
18751 can format it, using @TeX{}, by typing:
18757 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18758 mode on US ``letter'' size paper;
18759 that is, on a sheet 11 inches wide by 8.5 inches
18760 high. You will need to specify this form of printing as an option to
18761 your @sc{dvi} output program.
18763 @cindex documentation
18765 All the documentation for @value{GDBN} comes as part of the machine-readable
18766 distribution. The documentation is written in Texinfo format, which is
18767 a documentation system that uses a single source file to produce both
18768 on-line information and a printed manual. You can use one of the Info
18769 formatting commands to create the on-line version of the documentation
18770 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18772 @value{GDBN} includes an already formatted copy of the on-line Info
18773 version of this manual in the @file{gdb} subdirectory. The main Info
18774 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18775 subordinate files matching @samp{gdb.info*} in the same directory. If
18776 necessary, you can print out these files, or read them with any editor;
18777 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18778 Emacs or the standalone @code{info} program, available as part of the
18779 @sc{gnu} Texinfo distribution.
18781 If you want to format these Info files yourself, you need one of the
18782 Info formatting programs, such as @code{texinfo-format-buffer} or
18785 If you have @code{makeinfo} installed, and are in the top level
18786 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18787 version @value{GDBVN}), you can make the Info file by typing:
18794 If you want to typeset and print copies of this manual, you need @TeX{},
18795 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18796 Texinfo definitions file.
18798 @TeX{} is a typesetting program; it does not print files directly, but
18799 produces output files called @sc{dvi} files. To print a typeset
18800 document, you need a program to print @sc{dvi} files. If your system
18801 has @TeX{} installed, chances are it has such a program. The precise
18802 command to use depends on your system; @kbd{lpr -d} is common; another
18803 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18804 require a file name without any extension or a @samp{.dvi} extension.
18806 @TeX{} also requires a macro definitions file called
18807 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18808 written in Texinfo format. On its own, @TeX{} cannot either read or
18809 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
18810 and is located in the @file{gdb-@var{version-number}/texinfo}
18813 If you have @TeX{} and a @sc{dvi} printer program installed, you can
18814 typeset and print this manual. First switch to the the @file{gdb}
18815 subdirectory of the main source directory (for example, to
18816 @file{gdb-@value{GDBVN}/gdb}) and type:
18822 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
18824 @node Installing GDB
18825 @appendix Installing @value{GDBN}
18826 @cindex configuring @value{GDBN}
18827 @cindex installation
18828 @cindex configuring @value{GDBN}, and source tree subdirectories
18830 @value{GDBN} comes with a @code{configure} script that automates the process
18831 of preparing @value{GDBN} for installation; you can then use @code{make} to
18832 build the @code{gdb} program.
18834 @c irrelevant in info file; it's as current as the code it lives with.
18835 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
18836 look at the @file{README} file in the sources; we may have improved the
18837 installation procedures since publishing this manual.}
18840 The @value{GDBN} distribution includes all the source code you need for
18841 @value{GDBN} in a single directory, whose name is usually composed by
18842 appending the version number to @samp{gdb}.
18844 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
18845 @file{gdb-@value{GDBVN}} directory. That directory contains:
18848 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
18849 script for configuring @value{GDBN} and all its supporting libraries
18851 @item gdb-@value{GDBVN}/gdb
18852 the source specific to @value{GDBN} itself
18854 @item gdb-@value{GDBVN}/bfd
18855 source for the Binary File Descriptor library
18857 @item gdb-@value{GDBVN}/include
18858 @sc{gnu} include files
18860 @item gdb-@value{GDBVN}/libiberty
18861 source for the @samp{-liberty} free software library
18863 @item gdb-@value{GDBVN}/opcodes
18864 source for the library of opcode tables and disassemblers
18866 @item gdb-@value{GDBVN}/readline
18867 source for the @sc{gnu} command-line interface
18869 @item gdb-@value{GDBVN}/glob
18870 source for the @sc{gnu} filename pattern-matching subroutine
18872 @item gdb-@value{GDBVN}/mmalloc
18873 source for the @sc{gnu} memory-mapped malloc package
18876 The simplest way to configure and build @value{GDBN} is to run @code{configure}
18877 from the @file{gdb-@var{version-number}} source directory, which in
18878 this example is the @file{gdb-@value{GDBVN}} directory.
18880 First switch to the @file{gdb-@var{version-number}} source directory
18881 if you are not already in it; then run @code{configure}. Pass the
18882 identifier for the platform on which @value{GDBN} will run as an
18888 cd gdb-@value{GDBVN}
18889 ./configure @var{host}
18894 where @var{host} is an identifier such as @samp{sun4} or
18895 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
18896 (You can often leave off @var{host}; @code{configure} tries to guess the
18897 correct value by examining your system.)
18899 Running @samp{configure @var{host}} and then running @code{make} builds the
18900 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
18901 libraries, then @code{gdb} itself. The configured source files, and the
18902 binaries, are left in the corresponding source directories.
18905 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
18906 system does not recognize this automatically when you run a different
18907 shell, you may need to run @code{sh} on it explicitly:
18910 sh configure @var{host}
18913 If you run @code{configure} from a directory that contains source
18914 directories for multiple libraries or programs, such as the
18915 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
18916 creates configuration files for every directory level underneath (unless
18917 you tell it not to, with the @samp{--norecursion} option).
18919 You should run the @code{configure} script from the top directory in the
18920 source tree, the @file{gdb-@var{version-number}} directory. If you run
18921 @code{configure} from one of the subdirectories, you will configure only
18922 that subdirectory. That is usually not what you want. In particular,
18923 if you run the first @code{configure} from the @file{gdb} subdirectory
18924 of the @file{gdb-@var{version-number}} directory, you will omit the
18925 configuration of @file{bfd}, @file{readline}, and other sibling
18926 directories of the @file{gdb} subdirectory. This leads to build errors
18927 about missing include files such as @file{bfd/bfd.h}.
18929 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
18930 However, you should make sure that the shell on your path (named by
18931 the @samp{SHELL} environment variable) is publicly readable. Remember
18932 that @value{GDBN} uses the shell to start your program---some systems refuse to
18933 let @value{GDBN} debug child processes whose programs are not readable.
18936 * Separate Objdir:: Compiling @value{GDBN} in another directory
18937 * Config Names:: Specifying names for hosts and targets
18938 * Configure Options:: Summary of options for configure
18941 @node Separate Objdir
18942 @section Compiling @value{GDBN} in another directory
18944 If you want to run @value{GDBN} versions for several host or target machines,
18945 you need a different @code{gdb} compiled for each combination of
18946 host and target. @code{configure} is designed to make this easy by
18947 allowing you to generate each configuration in a separate subdirectory,
18948 rather than in the source directory. If your @code{make} program
18949 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
18950 @code{make} in each of these directories builds the @code{gdb}
18951 program specified there.
18953 To build @code{gdb} in a separate directory, run @code{configure}
18954 with the @samp{--srcdir} option to specify where to find the source.
18955 (You also need to specify a path to find @code{configure}
18956 itself from your working directory. If the path to @code{configure}
18957 would be the same as the argument to @samp{--srcdir}, you can leave out
18958 the @samp{--srcdir} option; it is assumed.)
18960 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
18961 separate directory for a Sun 4 like this:
18965 cd gdb-@value{GDBVN}
18968 ../gdb-@value{GDBVN}/configure sun4
18973 When @code{configure} builds a configuration using a remote source
18974 directory, it creates a tree for the binaries with the same structure
18975 (and using the same names) as the tree under the source directory. In
18976 the example, you'd find the Sun 4 library @file{libiberty.a} in the
18977 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
18978 @file{gdb-sun4/gdb}.
18980 Make sure that your path to the @file{configure} script has just one
18981 instance of @file{gdb} in it. If your path to @file{configure} looks
18982 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
18983 one subdirectory of @value{GDBN}, not the whole package. This leads to
18984 build errors about missing include files such as @file{bfd/bfd.h}.
18986 One popular reason to build several @value{GDBN} configurations in separate
18987 directories is to configure @value{GDBN} for cross-compiling (where
18988 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
18989 programs that run on another machine---the @dfn{target}).
18990 You specify a cross-debugging target by
18991 giving the @samp{--target=@var{target}} option to @code{configure}.
18993 When you run @code{make} to build a program or library, you must run
18994 it in a configured directory---whatever directory you were in when you
18995 called @code{configure} (or one of its subdirectories).
18997 The @code{Makefile} that @code{configure} generates in each source
18998 directory also runs recursively. If you type @code{make} in a source
18999 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19000 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19001 will build all the required libraries, and then build GDB.
19003 When you have multiple hosts or targets configured in separate
19004 directories, you can run @code{make} on them in parallel (for example,
19005 if they are NFS-mounted on each of the hosts); they will not interfere
19009 @section Specifying names for hosts and targets
19011 The specifications used for hosts and targets in the @code{configure}
19012 script are based on a three-part naming scheme, but some short predefined
19013 aliases are also supported. The full naming scheme encodes three pieces
19014 of information in the following pattern:
19017 @var{architecture}-@var{vendor}-@var{os}
19020 For example, you can use the alias @code{sun4} as a @var{host} argument,
19021 or as the value for @var{target} in a @code{--target=@var{target}}
19022 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19024 The @code{configure} script accompanying @value{GDBN} does not provide
19025 any query facility to list all supported host and target names or
19026 aliases. @code{configure} calls the Bourne shell script
19027 @code{config.sub} to map abbreviations to full names; you can read the
19028 script, if you wish, or you can use it to test your guesses on
19029 abbreviations---for example:
19032 % sh config.sub i386-linux
19034 % sh config.sub alpha-linux
19035 alpha-unknown-linux-gnu
19036 % sh config.sub hp9k700
19038 % sh config.sub sun4
19039 sparc-sun-sunos4.1.1
19040 % sh config.sub sun3
19041 m68k-sun-sunos4.1.1
19042 % sh config.sub i986v
19043 Invalid configuration `i986v': machine `i986v' not recognized
19047 @code{config.sub} is also distributed in the @value{GDBN} source
19048 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19050 @node Configure Options
19051 @section @code{configure} options
19053 Here is a summary of the @code{configure} options and arguments that
19054 are most often useful for building @value{GDBN}. @code{configure} also has
19055 several other options not listed here. @inforef{What Configure
19056 Does,,configure.info}, for a full explanation of @code{configure}.
19059 configure @r{[}--help@r{]}
19060 @r{[}--prefix=@var{dir}@r{]}
19061 @r{[}--exec-prefix=@var{dir}@r{]}
19062 @r{[}--srcdir=@var{dirname}@r{]}
19063 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19064 @r{[}--target=@var{target}@r{]}
19069 You may introduce options with a single @samp{-} rather than
19070 @samp{--} if you prefer; but you may abbreviate option names if you use
19075 Display a quick summary of how to invoke @code{configure}.
19077 @item --prefix=@var{dir}
19078 Configure the source to install programs and files under directory
19081 @item --exec-prefix=@var{dir}
19082 Configure the source to install programs under directory
19085 @c avoid splitting the warning from the explanation:
19087 @item --srcdir=@var{dirname}
19088 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19089 @code{make} that implements the @code{VPATH} feature.}@*
19090 Use this option to make configurations in directories separate from the
19091 @value{GDBN} source directories. Among other things, you can use this to
19092 build (or maintain) several configurations simultaneously, in separate
19093 directories. @code{configure} writes configuration specific files in
19094 the current directory, but arranges for them to use the source in the
19095 directory @var{dirname}. @code{configure} creates directories under
19096 the working directory in parallel to the source directories below
19099 @item --norecursion
19100 Configure only the directory level where @code{configure} is executed; do not
19101 propagate configuration to subdirectories.
19103 @item --target=@var{target}
19104 Configure @value{GDBN} for cross-debugging programs running on the specified
19105 @var{target}. Without this option, @value{GDBN} is configured to debug
19106 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19108 There is no convenient way to generate a list of all available targets.
19110 @item @var{host} @dots{}
19111 Configure @value{GDBN} to run on the specified @var{host}.
19113 There is no convenient way to generate a list of all available hosts.
19116 There are many other options available as well, but they are generally
19117 needed for special purposes only.
19119 @node Maintenance Commands
19120 @appendix Maintenance Commands
19121 @cindex maintenance commands
19122 @cindex internal commands
19124 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19125 includes a number of commands intended for @value{GDBN} developers.
19126 These commands are provided here for reference.
19129 @kindex maint info breakpoints
19130 @item @anchor{maint info breakpoints}maint info breakpoints
19131 Using the same format as @samp{info breakpoints}, display both the
19132 breakpoints you've set explicitly, and those @value{GDBN} is using for
19133 internal purposes. Internal breakpoints are shown with negative
19134 breakpoint numbers. The type column identifies what kind of breakpoint
19139 Normal, explicitly set breakpoint.
19142 Normal, explicitly set watchpoint.
19145 Internal breakpoint, used to handle correctly stepping through
19146 @code{longjmp} calls.
19148 @item longjmp resume
19149 Internal breakpoint at the target of a @code{longjmp}.
19152 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19155 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19158 Shared library events.
19162 @kindex maint internal-error
19163 @kindex maint internal-warning
19164 @item maint internal-error
19165 @itemx maint internal-warning
19166 Cause @value{GDBN} to call the internal function @code{internal_error}
19167 or @code{internal_warning} and hence behave as though an internal error
19168 or internal warning has been detected. In addition to reporting the
19169 internal problem, these functions give the user the opportunity to
19170 either quit @value{GDBN} or create a core file of the current
19171 @value{GDBN} session.
19174 (gdb) @kbd{maint internal-error testing, 1, 2}
19175 @dots{}/maint.c:121: internal-error: testing, 1, 2
19176 A problem internal to GDB has been detected. Further
19177 debugging may prove unreliable.
19178 Quit this debugging session? (y or n) @kbd{n}
19179 Create a core file? (y or n) @kbd{n}
19183 Takes an optional parameter that is used as the text of the error or
19186 @kindex maint print dummy-frames
19187 @item maint print dummy-frames
19189 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19194 (gdb) @kbd{print add(2,3)}
19195 Breakpoint 2, add (a=2, b=3) at @dots{}
19197 The program being debugged stopped while in a function called from GDB.
19199 (gdb) @kbd{maint print dummy-frames}
19200 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19201 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19202 call_lo=0x01014000 call_hi=0x01014001
19206 Takes an optional file parameter.
19208 @kindex maint print registers
19209 @kindex maint print raw-registers
19210 @kindex maint print cooked-registers
19211 @kindex maint print register-groups
19212 @item maint print registers
19213 @itemx maint print raw-registers
19214 @itemx maint print cooked-registers
19215 @itemx maint print register-groups
19216 Print @value{GDBN}'s internal register data structures.
19218 The command @code{maint print raw-registers} includes the contents of
19219 the raw register cache; the command @code{maint print cooked-registers}
19220 includes the (cooked) value of all registers; and the command
19221 @code{maint print register-groups} includes the groups that each
19222 register is a member of. @xref{Registers,, Registers, gdbint,
19223 @value{GDBN} Internals}.
19225 Takes an optional file parameter.
19227 @kindex maint print reggroups
19228 @item maint print reggroups
19229 Print @value{GDBN}'s internal register group data structures.
19231 Takes an optional file parameter.
19234 (gdb) @kbd{maint print reggroups}
19245 @kindex maint set profile
19246 @kindex maint show profile
19247 @cindex profiling GDB
19248 @item maint set profile
19249 @itemx maint show profile
19250 Control profiling of @value{GDBN}.
19252 Profiling will be disabled until you use the @samp{maint set profile}
19253 command to enable it. When you enable profiling, the system will begin
19254 collecting timing and execution count data; when you disable profiling or
19255 exit @value{GDBN}, the results will be written to a log file. Remember that
19256 if you use profiling, @value{GDBN} will overwrite the profiling log file
19257 (often called @file{gmon.out}). If you have a record of important profiling
19258 data in a @file{gmon.out} file, be sure to move it to a safe location.
19260 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19261 compiled with the @samp{-pg} compiler option.
19266 @node Remote Protocol
19267 @appendix @value{GDBN} Remote Serial Protocol
19272 * Stop Reply Packets::
19273 * General Query Packets::
19274 * Register Packet Format::
19276 * File-I/O remote protocol extension::
19282 There may be occasions when you need to know something about the
19283 protocol---for example, if there is only one serial port to your target
19284 machine, you might want your program to do something special if it
19285 recognizes a packet meant for @value{GDBN}.
19287 In the examples below, @samp{->} and @samp{<-} are used to indicate
19288 transmitted and received data respectfully.
19290 @cindex protocol, @value{GDBN} remote serial
19291 @cindex serial protocol, @value{GDBN} remote
19292 @cindex remote serial protocol
19293 All @value{GDBN} commands and responses (other than acknowledgments) are
19294 sent as a @var{packet}. A @var{packet} is introduced with the character
19295 @samp{$}, the actual @var{packet-data}, and the terminating character
19296 @samp{#} followed by a two-digit @var{checksum}:
19299 @code{$}@var{packet-data}@code{#}@var{checksum}
19303 @cindex checksum, for @value{GDBN} remote
19305 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19306 characters between the leading @samp{$} and the trailing @samp{#} (an
19307 eight bit unsigned checksum).
19309 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19310 specification also included an optional two-digit @var{sequence-id}:
19313 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19316 @cindex sequence-id, for @value{GDBN} remote
19318 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19319 has never output @var{sequence-id}s. Stubs that handle packets added
19320 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19322 @cindex acknowledgment, for @value{GDBN} remote
19323 When either the host or the target machine receives a packet, the first
19324 response expected is an acknowledgment: either @samp{+} (to indicate
19325 the package was received correctly) or @samp{-} (to request
19329 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19334 The host (@value{GDBN}) sends @var{command}s, and the target (the
19335 debugging stub incorporated in your program) sends a @var{response}. In
19336 the case of step and continue @var{command}s, the response is only sent
19337 when the operation has completed (the target has again stopped).
19339 @var{packet-data} consists of a sequence of characters with the
19340 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19343 Fields within the packet should be separated using @samp{,} @samp{;} or
19344 @cindex remote protocol, field separator
19345 @samp{:}. Except where otherwise noted all numbers are represented in
19346 @sc{hex} with leading zeros suppressed.
19348 Implementors should note that prior to @value{GDBN} 5.0, the character
19349 @samp{:} could not appear as the third character in a packet (as it
19350 would potentially conflict with the @var{sequence-id}).
19352 Response @var{data} can be run-length encoded to save space. A @samp{*}
19353 means that the next character is an @sc{ascii} encoding giving a repeat count
19354 which stands for that many repetitions of the character preceding the
19355 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19356 where @code{n >=3} (which is where rle starts to win). The printable
19357 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19358 value greater than 126 should not be used.
19360 Some remote systems have used a different run-length encoding mechanism
19361 loosely refered to as the cisco encoding. Following the @samp{*}
19362 character are two hex digits that indicate the size of the packet.
19369 means the same as "0000".
19371 The error response returned for some packets includes a two character
19372 error number. That number is not well defined.
19374 For any @var{command} not supported by the stub, an empty response
19375 (@samp{$#00}) should be returned. That way it is possible to extend the
19376 protocol. A newer @value{GDBN} can tell if a packet is supported based
19379 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19380 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19386 The following table provides a complete list of all currently defined
19387 @var{command}s and their corresponding response @var{data}.
19391 @item @code{!} --- extended mode
19392 @cindex @code{!} packet
19394 Enable extended mode. In extended mode, the remote server is made
19395 persistent. The @samp{R} packet is used to restart the program being
19401 The remote target both supports and has enabled extended mode.
19404 @item @code{?} --- last signal
19405 @cindex @code{?} packet
19407 Indicate the reason the target halted. The reply is the same as for
19411 @xref{Stop Reply Packets}, for the reply specifications.
19413 @item @code{a} --- reserved
19415 Reserved for future use.
19417 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19418 @cindex @code{A} packet
19420 Initialized @samp{argv[]} array passed into program. @var{arglen}
19421 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19422 See @code{gdbserver} for more details.
19430 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19431 @cindex @code{b} packet
19433 Change the serial line speed to @var{baud}.
19435 JTC: @emph{When does the transport layer state change? When it's
19436 received, or after the ACK is transmitted. In either case, there are
19437 problems if the command or the acknowledgment packet is dropped.}
19439 Stan: @emph{If people really wanted to add something like this, and get
19440 it working for the first time, they ought to modify ser-unix.c to send
19441 some kind of out-of-band message to a specially-setup stub and have the
19442 switch happen "in between" packets, so that from remote protocol's point
19443 of view, nothing actually happened.}
19445 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19446 @cindex @code{B} packet
19448 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19449 breakpoint at @var{addr}.
19451 This packet has been replaced by the @samp{Z} and @samp{z} packets
19452 (@pxref{insert breakpoint or watchpoint packet}).
19454 @item @code{c}@var{addr} --- continue
19455 @cindex @code{c} packet
19457 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19461 @xref{Stop Reply Packets}, for the reply specifications.
19463 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19464 @cindex @code{C} packet
19466 Continue with signal @var{sig} (hex signal number). If
19467 @code{;}@var{addr} is omitted, resume at same address.
19470 @xref{Stop Reply Packets}, for the reply specifications.
19472 @item @code{d} --- toggle debug @strong{(deprecated)}
19473 @cindex @code{d} packet
19477 @item @code{D} --- detach
19478 @cindex @code{D} packet
19480 Detach @value{GDBN} from the remote system. Sent to the remote target
19481 before @value{GDBN} disconnects via the @code{detach} command.
19485 @item @emph{no response}
19486 @value{GDBN} does not check for any response after sending this packet.
19489 @item @code{e} --- reserved
19491 Reserved for future use.
19493 @item @code{E} --- reserved
19495 Reserved for future use.
19497 @item @code{f} --- reserved
19499 Reserved for future use.
19501 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19502 @cindex @code{F} packet
19504 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19505 sent by the target. This is part of the File-I/O protocol extension.
19506 @xref{File-I/O remote protocol extension}, for the specification.
19508 @item @code{g} --- read registers
19509 @anchor{read registers packet}
19510 @cindex @code{g} packet
19512 Read general registers.
19516 @item @var{XX@dots{}}
19517 Each byte of register data is described by two hex digits. The bytes
19518 with the register are transmitted in target byte order. The size of
19519 each register and their position within the @samp{g} @var{packet} are
19520 determined by the @value{GDBN} internal macros
19521 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19522 specification of several standard @code{g} packets is specified below.
19527 @item @code{G}@var{XX@dots{}} --- write regs
19528 @cindex @code{G} packet
19530 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19541 @item @code{h} --- reserved
19543 Reserved for future use.
19545 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19546 @cindex @code{H} packet
19548 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19549 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19550 should be @samp{c} for step and continue operations, @samp{g} for other
19551 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19552 the threads, a thread number, or zero which means pick any thread.
19563 @c 'H': How restrictive (or permissive) is the thread model. If a
19564 @c thread is selected and stopped, are other threads allowed
19565 @c to continue to execute? As I mentioned above, I think the
19566 @c semantics of each command when a thread is selected must be
19567 @c described. For example:
19569 @c 'g': If the stub supports threads and a specific thread is
19570 @c selected, returns the register block from that thread;
19571 @c otherwise returns current registers.
19573 @c 'G' If the stub supports threads and a specific thread is
19574 @c selected, sets the registers of the register block of
19575 @c that thread; otherwise sets current registers.
19577 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19578 @anchor{cycle step packet}
19579 @cindex @code{i} packet
19581 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19582 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19583 step starting at that address.
19585 @item @code{I} --- signal then cycle step @strong{(reserved)}
19586 @cindex @code{I} packet
19588 @xref{step with signal packet}. @xref{cycle step packet}.
19590 @item @code{j} --- reserved
19592 Reserved for future use.
19594 @item @code{J} --- reserved
19596 Reserved for future use.
19598 @item @code{k} --- kill request
19599 @cindex @code{k} packet
19601 FIXME: @emph{There is no description of how to operate when a specific
19602 thread context has been selected (i.e.@: does 'k' kill only that
19605 @item @code{K} --- reserved
19607 Reserved for future use.
19609 @item @code{l} --- reserved
19611 Reserved for future use.
19613 @item @code{L} --- reserved
19615 Reserved for future use.
19617 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19618 @cindex @code{m} packet
19620 Read @var{length} bytes of memory starting at address @var{addr}.
19621 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19622 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19623 transfer mechanism is needed.}
19627 @item @var{XX@dots{}}
19628 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19629 to read only part of the data. Neither @value{GDBN} nor the stub assume
19630 that sized memory transfers are assumed using word aligned
19631 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19637 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19638 @cindex @code{M} packet
19640 Write @var{length} bytes of memory starting at address @var{addr}.
19641 @var{XX@dots{}} is the data.
19648 for an error (this includes the case where only part of the data was
19652 @item @code{n} --- reserved
19654 Reserved for future use.
19656 @item @code{N} --- reserved
19658 Reserved for future use.
19660 @item @code{o} --- reserved
19662 Reserved for future use.
19664 @item @code{O} --- reserved
19666 Reserved for future use.
19668 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19669 @cindex @code{p} packet
19671 @xref{write register packet}.
19675 @item @var{r@dots{}.}
19676 The hex encoded value of the register in target byte order.
19679 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19680 @anchor{write register packet}
19681 @cindex @code{P} packet
19683 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19684 digits for each byte in the register (target byte order).
19694 @item @code{q}@var{query} --- general query
19695 @anchor{general query packet}
19696 @cindex @code{q} packet
19698 Request info about @var{query}. In general @value{GDBN} queries have a
19699 leading upper case letter. Custom vendor queries should use a company
19700 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19701 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19702 that they match the full @var{query} name.
19706 @item @var{XX@dots{}}
19707 Hex encoded data from query. The reply can not be empty.
19711 Indicating an unrecognized @var{query}.
19714 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19715 @cindex @code{Q} packet
19717 Set value of @var{var} to @var{val}.
19719 @xref{general query packet}, for a discussion of naming conventions.
19721 @item @code{r} --- reset @strong{(deprecated)}
19722 @cindex @code{r} packet
19724 Reset the entire system.
19726 @item @code{R}@var{XX} --- remote restart
19727 @cindex @code{R} packet
19729 Restart the program being debugged. @var{XX}, while needed, is ignored.
19730 This packet is only available in extended mode.
19734 @item @emph{no reply}
19735 The @samp{R} packet has no reply.
19738 @item @code{s}@var{addr} --- step
19739 @cindex @code{s} packet
19741 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19745 @xref{Stop Reply Packets}, for the reply specifications.
19747 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19748 @anchor{step with signal packet}
19749 @cindex @code{S} packet
19751 Like @samp{C} but step not continue.
19754 @xref{Stop Reply Packets}, for the reply specifications.
19756 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19757 @cindex @code{t} packet
19759 Search backwards starting at address @var{addr} for a match with pattern
19760 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19761 @var{addr} must be at least 3 digits.
19763 @item @code{T}@var{XX} --- thread alive
19764 @cindex @code{T} packet
19766 Find out if the thread XX is alive.
19771 thread is still alive
19776 @item @code{u} --- reserved
19778 Reserved for future use.
19780 @item @code{U} --- reserved
19782 Reserved for future use.
19784 @item @code{v} --- reserved
19786 Reserved for future use.
19788 @item @code{V} --- reserved
19790 Reserved for future use.
19792 @item @code{w} --- reserved
19794 Reserved for future use.
19796 @item @code{W} --- reserved
19798 Reserved for future use.
19800 @item @code{x} --- reserved
19802 Reserved for future use.
19804 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
19805 @cindex @code{X} packet
19807 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
19808 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
19809 escaped using @code{0x7d}.
19819 @item @code{y} --- reserved
19821 Reserved for future use.
19823 @item @code{Y} reserved
19825 Reserved for future use.
19827 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
19828 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
19829 @anchor{insert breakpoint or watchpoint packet}
19830 @cindex @code{z} packet
19831 @cindex @code{Z} packets
19833 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
19834 watchpoint starting at address @var{address} and covering the next
19835 @var{length} bytes.
19837 Each breakpoint and watchpoint packet @var{type} is documented
19840 @emph{Implementation notes: A remote target shall return an empty string
19841 for an unrecognized breakpoint or watchpoint packet @var{type}. A
19842 remote target shall support either both or neither of a given
19843 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
19844 avoid potential problems with duplicate packets, the operations should
19845 be implemented in an idempotent way.}
19847 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
19848 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
19849 @cindex @code{z0} packet
19850 @cindex @code{Z0} packet
19852 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
19853 @code{addr} of size @code{length}.
19855 A memory breakpoint is implemented by replacing the instruction at
19856 @var{addr} with a software breakpoint or trap instruction. The
19857 @code{length} is used by targets that indicates the size of the
19858 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
19859 @sc{mips} can insert either a 2 or 4 byte breakpoint).
19861 @emph{Implementation note: It is possible for a target to copy or move
19862 code that contains memory breakpoints (e.g., when implementing
19863 overlays). The behavior of this packet, in the presence of such a
19864 target, is not defined.}
19876 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
19877 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
19878 @cindex @code{z1} packet
19879 @cindex @code{Z1} packet
19881 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
19882 address @code{addr} of size @code{length}.
19884 A hardware breakpoint is implemented using a mechanism that is not
19885 dependant on being able to modify the target's memory.
19887 @emph{Implementation note: A hardware breakpoint is not affected by code
19900 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
19901 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
19902 @cindex @code{z2} packet
19903 @cindex @code{Z2} packet
19905 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
19917 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
19918 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
19919 @cindex @code{z3} packet
19920 @cindex @code{Z3} packet
19922 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
19934 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
19935 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
19936 @cindex @code{z4} packet
19937 @cindex @code{Z4} packet
19939 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
19953 @node Stop Reply Packets
19954 @section Stop Reply Packets
19955 @cindex stop reply packets
19957 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
19958 receive any of the below as a reply. In the case of the @samp{C},
19959 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
19960 when the target halts. In the below the exact meaning of @samp{signal
19961 number} is poorly defined. In general one of the UNIX signal numbering
19962 conventions is used.
19967 @var{AA} is the signal number
19969 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
19970 @cindex @code{T} packet reply
19972 @var{AA} = two hex digit signal number; @var{n...} = register number
19973 (hex), @var{r...} = target byte ordered register contents, size defined
19974 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
19975 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
19976 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
19977 address, this is a hex integer; @var{n...} = other string not starting
19978 with valid hex digit. @value{GDBN} should ignore this @var{n...},
19979 @var{r...} pair and go on to the next. This way we can extend the
19984 The process exited, and @var{AA} is the exit status. This is only
19985 applicable to certain targets.
19989 The process terminated with signal @var{AA}.
19991 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
19993 @var{AA} = signal number; @var{t@dots{}} = address of symbol
19994 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
19995 base of bss section. @emph{Note: only used by Cisco Systems targets.
19996 The difference between this reply and the @samp{qOffsets} query is that
19997 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
19998 is a query initiated by the host debugger.}
20000 @item O@var{XX@dots{}}
20002 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20003 any time while the program is running and the debugger should continue
20004 to wait for @samp{W}, @samp{T}, etc.
20006 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20008 @var{call-id} is the identifier which says which host system call should
20009 be called. This is just the name of the function. Translation into the
20010 correct system call is only applicable as it's defined in @value{GDBN}.
20011 @xref{File-I/O remote protocol extension}, for a list of implemented
20014 @var{parameter@dots{}} is a list of parameters as defined for this very
20017 The target replies with this packet when it expects @value{GDBN} to call
20018 a host system call on behalf of the target. @value{GDBN} replies with
20019 an appropriate @code{F} packet and keeps up waiting for the next reply
20020 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20021 @samp{s} action is expected to be continued.
20022 @xref{File-I/O remote protocol extension}, for more details.
20026 @node General Query Packets
20027 @section General Query Packets
20029 The following set and query packets have already been defined.
20033 @item @code{q}@code{C} --- current thread
20035 Return the current thread id.
20039 @item @code{QC}@var{pid}
20040 Where @var{pid} is a HEX encoded 16 bit process id.
20042 Any other reply implies the old pid.
20045 @item @code{q}@code{fThreadInfo} -- all thread ids
20047 @code{q}@code{sThreadInfo}
20049 Obtain a list of active thread ids from the target (OS). Since there
20050 may be too many active threads to fit into one reply packet, this query
20051 works iteratively: it may require more than one query/reply sequence to
20052 obtain the entire list of threads. The first query of the sequence will
20053 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20054 sequence will be the @code{qs}@code{ThreadInfo} query.
20056 NOTE: replaces the @code{qL} query (see below).
20060 @item @code{m}@var{id}
20062 @item @code{m}@var{id},@var{id}@dots{}
20063 a comma-separated list of thread ids
20065 (lower case 'el') denotes end of list.
20068 In response to each query, the target will reply with a list of one or
20069 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20070 will respond to each reply with a request for more thread ids (using the
20071 @code{qs} form of the query), until the target responds with @code{l}
20072 (lower-case el, for @code{'last'}).
20074 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20076 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20077 string description of a thread's attributes from the target OS. This
20078 string may contain anything that the target OS thinks is interesting for
20079 @value{GDBN} to tell the user about the thread. The string is displayed
20080 in @value{GDBN}'s @samp{info threads} display. Some examples of
20081 possible thread extra info strings are ``Runnable'', or ``Blocked on
20086 @item @var{XX@dots{}}
20087 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20088 the printable string containing the extra information about the thread's
20092 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20094 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20095 digit) is one to indicate the first query and zero to indicate a
20096 subsequent query; @var{threadcount} (two hex digits) is the maximum
20097 number of threads the response packet can contain; and @var{nextthread}
20098 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20099 returned in the response as @var{argthread}.
20101 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20106 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20107 Where: @var{count} (two hex digits) is the number of threads being
20108 returned; @var{done} (one hex digit) is zero to indicate more threads
20109 and one indicates no further threads; @var{argthreadid} (eight hex
20110 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20111 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20112 digits). See @code{remote.c:parse_threadlist_response()}.
20115 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20119 @item @code{E}@var{NN}
20120 An error (such as memory fault)
20121 @item @code{C}@var{CRC32}
20122 A 32 bit cyclic redundancy check of the specified memory region.
20125 @item @code{q}@code{Offsets} --- query sect offs
20127 Get section offsets that the target used when re-locating the downloaded
20128 image. @emph{Note: while a @code{Bss} offset is included in the
20129 response, @value{GDBN} ignores this and instead applies the @code{Data}
20130 offset to the @code{Bss} section.}
20134 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20137 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20139 Returns information on @var{threadid}. Where: @var{mode} is a hex
20140 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20147 See @code{remote.c:remote_unpack_thread_info_response()}.
20149 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20151 @var{command} (hex encoded) is passed to the local interpreter for
20152 execution. Invalid commands should be reported using the output string.
20153 Before the final result packet, the target may also respond with a
20154 number of intermediate @code{O}@var{output} console output packets.
20155 @emph{Implementors should note that providing access to a stubs's
20156 interpreter may have security implications}.
20161 A command response with no output.
20163 A command response with the hex encoded output string @var{OUTPUT}.
20164 @item @code{E}@var{NN}
20165 Indicate a badly formed request.
20167 When @samp{q}@samp{Rcmd} is not recognized.
20170 @item @code{qSymbol::} --- symbol lookup
20172 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20173 requests. Accept requests from the target for the values of symbols.
20178 The target does not need to look up any (more) symbols.
20179 @item @code{qSymbol:}@var{sym_name}
20180 The target requests the value of symbol @var{sym_name} (hex encoded).
20181 @value{GDBN} may provide the value by using the
20182 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20185 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20187 Set the value of @var{sym_name} to @var{sym_value}.
20189 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20190 target has previously requested.
20192 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20193 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20199 The target does not need to look up any (more) symbols.
20200 @item @code{qSymbol:}@var{sym_name}
20201 The target requests the value of a new symbol @var{sym_name} (hex
20202 encoded). @value{GDBN} will continue to supply the values of symbols
20203 (if available), until the target ceases to request them.
20208 @node Register Packet Format
20209 @section Register Packet Format
20211 The following @samp{g}/@samp{G} packets have previously been defined.
20212 In the below, some thirty-two bit registers are transferred as
20213 sixty-four bits. Those registers should be zero/sign extended (which?)
20214 to fill the space allocated. Register bytes are transfered in target
20215 byte order. The two nibbles within a register byte are transfered
20216 most-significant - least-significant.
20222 All registers are transfered as thirty-two bit quantities in the order:
20223 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20224 registers; fsr; fir; fp.
20228 All registers are transfered as sixty-four bit quantities (including
20229 thirty-two bit registers such as @code{sr}). The ordering is the same
20237 Example sequence of a target being re-started. Notice how the restart
20238 does not get any direct output:
20243 @emph{target restarts}
20246 <- @code{T001:1234123412341234}
20250 Example sequence of a target being stepped by a single instruction:
20253 -> @code{G1445@dots{}}
20258 <- @code{T001:1234123412341234}
20262 <- @code{1455@dots{}}
20266 @node File-I/O remote protocol extension
20267 @section File-I/O remote protocol extension
20268 @cindex File-I/O remote protocol extension
20271 * File-I/O Overview::
20272 * Protocol basics::
20273 * The `F' request packet::
20274 * The `F' reply packet::
20275 * Memory transfer::
20276 * The Ctrl-C message::
20278 * The isatty call::
20279 * The system call::
20280 * List of supported calls::
20281 * Protocol specific representation of datatypes::
20283 * File-I/O Examples::
20286 @node File-I/O Overview
20287 @subsection File-I/O Overview
20288 @cindex file-i/o overview
20290 The File I/O remote protocol extension (short: File-I/O) allows the
20291 target to use the hosts file system and console I/O when calling various
20292 system calls. System calls on the target system are translated into a
20293 remote protocol packet to the host system which then performs the needed
20294 actions and returns with an adequate response packet to the target system.
20295 This simulates file system operations even on targets that lack file systems.
20297 The protocol is defined host- and target-system independent. It uses
20298 it's own independent representation of datatypes and values. Both,
20299 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20300 translating the system dependent values into the unified protocol values
20301 when data is transmitted.
20303 The communication is synchronous. A system call is possible only
20304 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20305 packets. While @value{GDBN} handles the request for a system call,
20306 the target is stopped to allow deterministic access to the target's
20307 memory. Therefore File-I/O is not interuptible by target signals. It
20308 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20310 The target's request to perform a host system call does not finish
20311 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20312 after finishing the system call, the target returns to continuing the
20313 previous activity (continue, step). No additional continue or step
20314 request from @value{GDBN} is required.
20318 <- target requests 'system call X'
20319 target is stopped, @value{GDBN} executes system call
20320 -> GDB returns result
20321 ... target continues, GDB returns to wait for the target
20322 <- target hits breakpoint and sends a Txx packet
20325 The protocol is only used for files on the host file system and
20326 for I/O on the console. Character or block special devices, pipes,
20327 named pipes or sockets or any other communication method on the host
20328 system are not supported by this protocol.
20330 @node Protocol basics
20331 @subsection Protocol basics
20332 @cindex protocol basics, file-i/o
20334 The File-I/O protocol uses the @code{F} packet, as request as well
20335 as as reply packet. Since a File-I/O system call can only occur when
20336 @value{GDBN} is waiting for the continuing or stepping target, the
20337 File-I/O request is a reply that @value{GDBN} has to expect as a result
20338 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20339 This @code{F} packet contains all information needed to allow @value{GDBN}
20340 to call the appropriate host system call:
20344 A unique identifier for the requested system call.
20347 All parameters to the system call. Pointers are given as addresses
20348 in the target memory address space. Pointers to strings are given as
20349 pointer/length pair. Numerical values are given as they are.
20350 Numerical control values are given in a protocol specific representation.
20354 At that point @value{GDBN} has to perform the following actions.
20358 If parameter pointer values are given, which point to data needed as input
20359 to a system call, @value{GDBN} requests this data from the target with a
20360 standard @code{m} packet request. This additional communication has to be
20361 expected by the target implementation and is handled as any other @code{m}
20365 @value{GDBN} translates all value from protocol representation to host
20366 representation as needed. Datatypes are coerced into the host types.
20369 @value{GDBN} calls the system call
20372 It then coerces datatypes back to protocol representation.
20375 If pointer parameters in the request packet point to buffer space in which
20376 a system call is expected to copy data to, the data is transmitted to the
20377 target using a @code{M} or @code{X} packet. This packet has to be expected
20378 by the target implementation and is handled as any other @code{M} or @code{X}
20383 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20384 necessary information for the target to continue. This at least contains
20391 @code{errno}, if has been changed by the system call.
20398 After having done the needed type and value coercion, the target continues
20399 the latest continue or step action.
20401 @node The `F' request packet
20402 @subsection The @code{F} request packet
20403 @cindex file-i/o request packet
20404 @cindex @code{F} request packet
20406 The @code{F} request packet has the following format:
20411 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20414 @var{call-id} is the identifier to indicate the host system call to be called.
20415 This is just the name of the function.
20417 @var{parameter@dots{}} are the parameters to the system call.
20421 Parameters are hexadecimal integer values, either the real values in case
20422 of scalar datatypes, as pointers to target buffer space in case of compound
20423 datatypes and unspecified memory areas or as pointer/length pairs in case
20424 of string parameters. These are appended to the call-id, each separated
20425 from its predecessor by a comma. All values are transmitted in ASCII
20426 string representation, pointer/length pairs separated by a slash.
20428 @node The `F' reply packet
20429 @subsection The @code{F} reply packet
20430 @cindex file-i/o reply packet
20431 @cindex @code{F} reply packet
20433 The @code{F} reply packet has the following format:
20438 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20441 @var{retcode} is the return code of the system call as hexadecimal value.
20443 @var{errno} is the errno set by the call, in protocol specific representation.
20444 This parameter can be omitted if the call was successful.
20446 @var{Ctrl-C flag} is only send if the user requested a break. In this
20447 case, @var{errno} must be send as well, even if the call was successful.
20448 The @var{Ctrl-C flag} itself consists of the character 'C':
20455 or, if the call was interupted before the host call has been performed:
20462 assuming 4 is the protocol specific representation of @code{EINTR}.
20466 @node Memory transfer
20467 @subsection Memory transfer
20468 @cindex memory transfer, in file-i/o protocol
20470 Structured data which is transferred using a memory read or write as e.g.@:
20471 a @code{struct stat} is expected to be in a protocol specific format with
20472 all scalar multibyte datatypes being big endian. This should be done by
20473 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20474 it transfers memory to the target. Transferred pointers to structured
20475 data should point to the already coerced data at any time.
20477 @node The Ctrl-C message
20478 @subsection The Ctrl-C message
20479 @cindex ctrl-c message, in file-i/o protocol
20481 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20482 reply packet. In this case the target should behave, as if it had
20483 gotten a break message. The meaning for the target is ``system call
20484 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20485 (as with a break message) and return to @value{GDBN} with a @code{T02}
20486 packet. In this case, it's important for the target to know, in which
20487 state the system call was interrupted. Since this action is by design
20488 not an atomic operation, we have to differ between two cases:
20492 The system call hasn't been performed on the host yet.
20495 The system call on the host has been finished.
20499 These two states can be distinguished by the target by the value of the
20500 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20501 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20502 on POSIX systems. In any other case, the target may presume that the
20503 system call has been finished --- successful or not --- and should behave
20504 as if the break message arrived right after the system call.
20506 @value{GDBN} must behave reliable. If the system call has not been called
20507 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20508 @code{errno} in the packet. If the system call on the host has been finished
20509 before the user requests a break, the full action must be finshed by
20510 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20511 The @code{F} packet may only be send when either nothing has happened
20512 or the full action has been completed.
20515 @subsection Console I/O
20516 @cindex console i/o as part of file-i/o
20518 By default and if not explicitely closed by the target system, the file
20519 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20520 on the @value{GDBN} console is handled as any other file output operation
20521 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20522 by @value{GDBN} so that after the target read request from file descriptor
20523 0 all following typing is buffered until either one of the following
20528 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20530 system call is treated as finished.
20533 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20537 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20538 character, especially no Ctrl-D is appended to the input.
20542 If the user has typed more characters as fit in the buffer given to
20543 the read call, the trailing characters are buffered in @value{GDBN} until
20544 either another @code{read(0, @dots{})} is requested by the target or debugging
20545 is stopped on users request.
20547 @node The isatty call
20548 @subsection The isatty(3) call
20549 @cindex isatty call, file-i/o protocol
20551 A special case in this protocol is the library call @code{isatty} which
20552 is implemented as it's own call inside of this protocol. It returns
20553 1 to the target if the file descriptor given as parameter is attached
20554 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20555 would require implementing @code{ioctl} and would be more complex than
20558 @node The system call
20559 @subsection The system(3) call
20560 @cindex system call, file-i/o protocol
20562 The other special case in this protocol is the @code{system} call which
20563 is implemented as it's own call, too. @value{GDBN} is taking over the full
20564 task of calling the necessary host calls to perform the @code{system}
20565 call. The return value of @code{system} is simplified before it's returned
20566 to the target. Basically, the only signal transmitted back is @code{EINTR}
20567 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20568 entirely of the exit status of the called command.
20570 Due to security concerns, the @code{system} call is refused to be called
20571 by @value{GDBN} by default. The user has to allow this call explicitly by
20575 @kindex set remote system-call-allowed 1
20576 @item @code{set remote system-call-allowed 1}
20579 Disabling the @code{system} call is done by
20582 @kindex set remote system-call-allowed 0
20583 @item @code{set remote system-call-allowed 0}
20586 The current setting is shown by typing
20589 @kindex show remote system-call-allowed
20590 @item @code{show remote system-call-allowed}
20593 @node List of supported calls
20594 @subsection List of supported calls
20595 @cindex list of supported file-i/o calls
20612 @unnumberedsubsubsec open
20613 @cindex open, file-i/o system call
20617 int open(const char *pathname, int flags);
20618 int open(const char *pathname, int flags, mode_t mode);
20621 Fopen,pathptr/len,flags,mode
20625 @code{flags} is the bitwise or of the following values:
20629 If the file does not exist it will be created. The host
20630 rules apply as far as file ownership and time stamps
20634 When used with O_CREAT, if the file already exists it is
20635 an error and open() fails.
20638 If the file already exists and the open mode allows
20639 writing (O_RDWR or O_WRONLY is given) it will be
20640 truncated to length 0.
20643 The file is opened in append mode.
20646 The file is opened for reading only.
20649 The file is opened for writing only.
20652 The file is opened for reading and writing.
20655 Each other bit is silently ignored.
20660 @code{mode} is the bitwise or of the following values:
20664 User has read permission.
20667 User has write permission.
20670 Group has read permission.
20673 Group has write permission.
20676 Others have read permission.
20679 Others have write permission.
20682 Each other bit is silently ignored.
20687 @exdent Return value:
20688 open returns the new file descriptor or -1 if an error
20696 pathname already exists and O_CREAT and O_EXCL were used.
20699 pathname refers to a directory.
20702 The requested access is not allowed.
20705 pathname was too long.
20708 A directory component in pathname does not exist.
20711 pathname refers to a device, pipe, named pipe or socket.
20714 pathname refers to a file on a read-only filesystem and
20715 write access was requested.
20718 pathname is an invalid pointer value.
20721 No space on device to create the file.
20724 The process already has the maximum number of files open.
20727 The limit on the total number of files open on the system
20731 The call was interrupted by the user.
20735 @unnumberedsubsubsec close
20736 @cindex close, file-i/o system call
20745 @exdent Return value:
20746 close returns zero on success, or -1 if an error occurred.
20753 fd isn't a valid open file descriptor.
20756 The call was interrupted by the user.
20760 @unnumberedsubsubsec read
20761 @cindex read, file-i/o system call
20765 int read(int fd, void *buf, unsigned int count);
20768 Fread,fd,bufptr,count
20770 @exdent Return value:
20771 On success, the number of bytes read is returned.
20772 Zero indicates end of file. If count is zero, read
20773 returns zero as well. On error, -1 is returned.
20780 fd is not a valid file descriptor or is not open for
20784 buf is an invalid pointer value.
20787 The call was interrupted by the user.
20791 @unnumberedsubsubsec write
20792 @cindex write, file-i/o system call
20796 int write(int fd, const void *buf, unsigned int count);
20799 Fwrite,fd,bufptr,count
20801 @exdent Return value:
20802 On success, the number of bytes written are returned.
20803 Zero indicates nothing was written. On error, -1
20811 fd is not a valid file descriptor or is not open for
20815 buf is an invalid pointer value.
20818 An attempt was made to write a file that exceeds the
20819 host specific maximum file size allowed.
20822 No space on device to write the data.
20825 The call was interrupted by the user.
20829 @unnumberedsubsubsec lseek
20830 @cindex lseek, file-i/o system call
20834 long lseek (int fd, long offset, int flag);
20837 Flseek,fd,offset,flag
20840 @code{flag} is one of:
20844 The offset is set to offset bytes.
20847 The offset is set to its current location plus offset
20851 The offset is set to the size of the file plus offset
20856 @exdent Return value:
20857 On success, the resulting unsigned offset in bytes from
20858 the beginning of the file is returned. Otherwise, a
20859 value of -1 is returned.
20866 fd is not a valid open file descriptor.
20869 fd is associated with the @value{GDBN} console.
20872 flag is not a proper value.
20875 The call was interrupted by the user.
20879 @unnumberedsubsubsec rename
20880 @cindex rename, file-i/o system call
20884 int rename(const char *oldpath, const char *newpath);
20887 Frename,oldpathptr/len,newpathptr/len
20889 @exdent Return value:
20890 On success, zero is returned. On error, -1 is returned.
20897 newpath is an existing directory, but oldpath is not a
20901 newpath is a non-empty directory.
20904 oldpath or newpath is a directory that is in use by some
20908 An attempt was made to make a directory a subdirectory
20912 A component used as a directory in oldpath or new
20913 path is not a directory. Or oldpath is a directory
20914 and newpath exists but is not a directory.
20917 oldpathptr or newpathptr are invalid pointer values.
20920 No access to the file or the path of the file.
20924 oldpath or newpath was too long.
20927 A directory component in oldpath or newpath does not exist.
20930 The file is on a read-only filesystem.
20933 The device containing the file has no room for the new
20937 The call was interrupted by the user.
20941 @unnumberedsubsubsec unlink
20942 @cindex unlink, file-i/o system call
20946 int unlink(const char *pathname);
20949 Funlink,pathnameptr/len
20951 @exdent Return value:
20952 On success, zero is returned. On error, -1 is returned.
20959 No access to the file or the path of the file.
20962 The system does not allow unlinking of directories.
20965 The file pathname cannot be unlinked because it's
20966 being used by another process.
20969 pathnameptr is an invalid pointer value.
20972 pathname was too long.
20975 A directory component in pathname does not exist.
20978 A component of the path is not a directory.
20981 The file is on a read-only filesystem.
20984 The call was interrupted by the user.
20988 @unnumberedsubsubsec stat/fstat
20989 @cindex fstat, file-i/o system call
20990 @cindex stat, file-i/o system call
20994 int stat(const char *pathname, struct stat *buf);
20995 int fstat(int fd, struct stat *buf);
20998 Fstat,pathnameptr/len,bufptr
21001 @exdent Return value:
21002 On success, zero is returned. On error, -1 is returned.
21009 fd is not a valid open file.
21012 A directory component in pathname does not exist or the
21013 path is an empty string.
21016 A component of the path is not a directory.
21019 pathnameptr is an invalid pointer value.
21022 No access to the file or the path of the file.
21025 pathname was too long.
21028 The call was interrupted by the user.
21032 @unnumberedsubsubsec gettimeofday
21033 @cindex gettimeofday, file-i/o system call
21037 int gettimeofday(struct timeval *tv, void *tz);
21040 Fgettimeofday,tvptr,tzptr
21042 @exdent Return value:
21043 On success, 0 is returned, -1 otherwise.
21050 tz is a non-NULL pointer.
21053 tvptr and/or tzptr is an invalid pointer value.
21057 @unnumberedsubsubsec isatty
21058 @cindex isatty, file-i/o system call
21062 int isatty(int fd);
21067 @exdent Return value:
21068 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21075 The call was interrupted by the user.
21079 @unnumberedsubsubsec system
21080 @cindex system, file-i/o system call
21084 int system(const char *command);
21087 Fsystem,commandptr/len
21089 @exdent Return value:
21090 The value returned is -1 on error and the return status
21091 of the command otherwise. Only the exit status of the
21092 command is returned, which is extracted from the hosts
21093 system return value by calling WEXITSTATUS(retval).
21094 In case /bin/sh could not be executed, 127 is returned.
21101 The call was interrupted by the user.
21104 @node Protocol specific representation of datatypes
21105 @subsection Protocol specific representation of datatypes
21106 @cindex protocol specific representation of datatypes, in file-i/o protocol
21109 * Integral datatypes::
21115 @node Integral datatypes
21116 @unnumberedsubsubsec Integral datatypes
21117 @cindex integral datatypes, in file-i/o protocol
21119 The integral datatypes used in the system calls are
21122 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21125 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21126 implemented as 32 bit values in this protocol.
21128 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21130 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21131 in @file{limits.h}) to allow range checking on host and target.
21133 @code{time_t} datatypes are defined as seconds since the Epoch.
21135 All integral datatypes transferred as part of a memory read or write of a
21136 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21139 @node Pointer values
21140 @unnumberedsubsubsec Pointer values
21141 @cindex pointer values, in file-i/o protocol
21143 Pointers to target data are transmitted as they are. An exception
21144 is made for pointers to buffers for which the length isn't
21145 transmitted as part of the function call, namely strings. Strings
21146 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21153 which is a pointer to data of length 18 bytes at position 0x1aaf.
21154 The length is defined as the full string length in bytes, including
21155 the trailing null byte. Example:
21158 ``hello, world'' at address 0x123456
21169 @unnumberedsubsubsec struct stat
21170 @cindex struct stat, in file-i/o protocol
21172 The buffer of type struct stat used by the target and @value{GDBN} is defined
21177 unsigned int st_dev; /* device */
21178 unsigned int st_ino; /* inode */
21179 mode_t st_mode; /* protection */
21180 unsigned int st_nlink; /* number of hard links */
21181 unsigned int st_uid; /* user ID of owner */
21182 unsigned int st_gid; /* group ID of owner */
21183 unsigned int st_rdev; /* device type (if inode device) */
21184 unsigned long st_size; /* total size, in bytes */
21185 unsigned long st_blksize; /* blocksize for filesystem I/O */
21186 unsigned long st_blocks; /* number of blocks allocated */
21187 time_t st_atime; /* time of last access */
21188 time_t st_mtime; /* time of last modification */
21189 time_t st_ctime; /* time of last change */
21193 The integral datatypes are conforming to the definitions given in the
21194 approriate section (see @ref{Integral datatypes}, for details) so this
21195 structure is of size 64 bytes.
21197 The values of several fields have a restricted meaning and/or
21204 st_ino: No valid meaning for the target. Transmitted unchanged.
21206 st_mode: Valid mode bits are described in Appendix C. Any other
21207 bits have currently no meaning for the target.
21209 st_uid: No valid meaning for the target. Transmitted unchanged.
21211 st_gid: No valid meaning for the target. Transmitted unchanged.
21213 st_rdev: No valid meaning for the target. Transmitted unchanged.
21215 st_atime, st_mtime, st_ctime:
21216 These values have a host and file system dependent
21217 accuracy. Especially on Windows hosts the file systems
21218 don't support exact timing values.
21221 The target gets a struct stat of the above representation and is
21222 responsible to coerce it to the target representation before
21225 Note that due to size differences between the host and target
21226 representation of stat members, these members could eventually
21227 get truncated on the target.
21229 @node struct timeval
21230 @unnumberedsubsubsec struct timeval
21231 @cindex struct timeval, in file-i/o protocol
21233 The buffer of type struct timeval used by the target and @value{GDBN}
21234 is defined as follows:
21238 time_t tv_sec; /* second */
21239 long tv_usec; /* microsecond */
21243 The integral datatypes are conforming to the definitions given in the
21244 approriate section (see @ref{Integral datatypes}, for details) so this
21245 structure is of size 8 bytes.
21248 @subsection Constants
21249 @cindex constants, in file-i/o protocol
21251 The following values are used for the constants inside of the
21252 protocol. @value{GDBN} and target are resposible to translate these
21253 values before and after the call as needed.
21264 @unnumberedsubsubsec Open flags
21265 @cindex open flags, in file-i/o protocol
21267 All values are given in hexadecimal representation.
21279 @node mode_t values
21280 @unnumberedsubsubsec mode_t values
21281 @cindex mode_t values, in file-i/o protocol
21283 All values are given in octal representation.
21300 @unnumberedsubsubsec Errno values
21301 @cindex errno values, in file-i/o protocol
21303 All values are given in decimal representation.
21328 EUNKNOWN is used as a fallback error value if a host system returns
21329 any error value not in the list of supported error numbers.
21332 @unnumberedsubsubsec Lseek flags
21333 @cindex lseek flags, in file-i/o protocol
21342 @unnumberedsubsubsec Limits
21343 @cindex limits, in file-i/o protocol
21345 All values are given in decimal representation.
21348 INT_MIN -2147483648
21350 UINT_MAX 4294967295
21351 LONG_MIN -9223372036854775808
21352 LONG_MAX 9223372036854775807
21353 ULONG_MAX 18446744073709551615
21356 @node File-I/O Examples
21357 @subsection File-I/O Examples
21358 @cindex file-i/o examples
21360 Example sequence of a write call, file descriptor 3, buffer is at target
21361 address 0x1234, 6 bytes should be written:
21364 <- @code{Fwrite,3,1234,6}
21365 @emph{request memory read from target}
21368 @emph{return "6 bytes written"}
21372 Example sequence of a read call, file descriptor 3, buffer is at target
21373 address 0x1234, 6 bytes should be read:
21376 <- @code{Fread,3,1234,6}
21377 @emph{request memory write to target}
21378 -> @code{X1234,6:XXXXXX}
21379 @emph{return "6 bytes read"}
21383 Example sequence of a read call, call fails on the host due to invalid
21384 file descriptor (EBADF):
21387 <- @code{Fread,3,1234,6}
21391 Example sequence of a read call, user presses Ctrl-C before syscall on
21395 <- @code{Fread,3,1234,6}
21400 Example sequence of a read call, user presses Ctrl-C after syscall on
21404 <- @code{Fread,3,1234,6}
21405 -> @code{X1234,6:XXXXXX}
21409 @include agentexpr.texi
21421 % I think something like @colophon should be in texinfo. In the
21423 \long\def\colophon{\hbox to0pt{}\vfill
21424 \centerline{The body of this manual is set in}
21425 \centerline{\fontname\tenrm,}
21426 \centerline{with headings in {\bf\fontname\tenbf}}
21427 \centerline{and examples in {\tt\fontname\tentt}.}
21428 \centerline{{\it\fontname\tenit\/},}
21429 \centerline{{\bf\fontname\tenbf}, and}
21430 \centerline{{\sl\fontname\tensl\/}}
21431 \centerline{are used for emphasis.}\vfill}
21433 % Blame: doc@cygnus.com, 1991.