1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002
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!
33 @c !!set GDB manual's revision date
36 @c !!set GDB edit command default editor
39 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
41 @c This is a dir.info fragment to support semi-automated addition of
42 @c manuals to an info tree.
43 @dircategory Programming & development tools.
45 * Gdb: (gdb). The @sc{gnu} debugger.
49 This file documents the @sc{gnu} debugger @value{GDBN}.
52 This is the @value{EDITION} Edition, @value{DATE},
53 of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger}
54 for @value{GDBN} Version @value{GDBVN}.
56 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
57 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
59 Permission is granted to copy, distribute and/or modify this document
60 under the terms of the GNU Free Documentation License, Version 1.1 or
61 any later version published by the Free Software Foundation; with the
62 Invariant Sections being ``Free Software'' and ``Free Software Needs
63 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
64 and with the Back-Cover Texts as in (a) below.
66 (a) The Free Software Foundation's Back-Cover Text is: ``You have
67 freedom to copy and modify this GNU Manual, like GNU software. Copies
68 published by the Free Software Foundation raise funds for GNU
73 @title Debugging with @value{GDBN}
74 @subtitle The @sc{gnu} Source-Level Debugger
76 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
77 @subtitle @value{DATE}
78 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
82 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
83 \hfill {\it Debugging with @value{GDBN}}\par
84 \hfill \TeX{}info \texinfoversion\par
88 @vskip 0pt plus 1filll
89 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
90 1996, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
92 Published by the Free Software Foundation @*
93 59 Temple Place - Suite 330, @*
94 Boston, MA 02111-1307 USA @*
97 Permission is granted to copy, distribute and/or modify this document
98 under the terms of the GNU Free Documentation License, Version 1.1 or
99 any later version published by the Free Software Foundation; with the
100 Invariant Sections being ``Free Software'' and ``Free Software Needs
101 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
102 and with the Back-Cover Texts as in (a) below.
104 (a) The Free Software Foundation's Back-Cover Text is: ``You have
105 freedom to copy and modify this GNU Manual, like GNU software. Copies
106 published by the Free Software Foundation raise funds for GNU
112 @node Top, Summary, (dir), (dir)
114 @top Debugging with @value{GDBN}
116 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
118 This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
121 Copyright (C) 1988-2002 Free Software Foundation, Inc.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Stack:: Examining the stack
132 * Source:: Examining source files
133 * Data:: Examining data
134 * Macros:: Preprocessor Macros
135 * Tracepoints:: Debugging remote targets non-intrusively
136 * Overlays:: Debugging programs that use overlays
138 * Languages:: Using @value{GDBN} with different languages
140 * Symbols:: Examining the symbol table
141 * Altering:: Altering execution
142 * GDB Files:: @value{GDBN} files
143 * Targets:: Specifying a debugging target
144 * Remote Debugging:: Debugging remote programs
145 * Configurations:: Configuration-specific information
146 * Controlling GDB:: Controlling @value{GDBN}
147 * Sequences:: Canned sequences of commands
148 * TUI:: @value{GDBN} Text User Interface
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Copying:: GNU General Public License says
162 how you can copy and share GDB
163 * GNU Free Documentation License:: The license for this documentation
172 @unnumbered Summary of @value{GDBN}
174 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
175 going on ``inside'' another program while it executes---or what another
176 program was doing at the moment it crashed.
178 @value{GDBN} can do four main kinds of things (plus other things in support of
179 these) to help you catch bugs in the act:
183 Start your program, specifying anything that might affect its behavior.
186 Make your program stop on specified conditions.
189 Examine what has happened, when your program has stopped.
192 Change things in your program, so you can experiment with correcting the
193 effects of one bug and go on to learn about another.
196 You can use @value{GDBN} to debug programs written in C and C++.
197 For more information, see @ref{Support,,Supported languages}.
198 For more information, see @ref{C,,C and C++}.
200 @c OBSOLETE @cindex Chill
203 @c OBSOLETE and Chill
204 is partial. For information on Modula-2, see @ref{Modula-2,,Modula-2}.
205 @c OBSOLETE For information on Chill, see @ref{Chill}.
208 Debugging Pascal programs which use sets, subranges, file variables, or
209 nested functions does not currently work. @value{GDBN} does not support
210 entering expressions, printing values, or similar features using Pascal
214 @value{GDBN} can be used to debug programs written in Fortran, although
215 it may be necessary to refer to some variables with a trailing
219 * Free Software:: Freely redistributable software
220 * Contributors:: Contributors to GDB
224 @unnumberedsec Free software
226 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
227 General Public License
228 (GPL). The GPL gives you the freedom to copy or adapt a licensed
229 program---but every person getting a copy also gets with it the
230 freedom to modify that copy (which means that they must get access to
231 the source code), and the freedom to distribute further copies.
232 Typical software companies use copyrights to limit your freedoms; the
233 Free Software Foundation uses the GPL to preserve these freedoms.
235 Fundamentally, the General Public License is a license which says that
236 you have these freedoms and that you cannot take these freedoms away
239 @unnumberedsec Free Software Needs Free Documentation
241 The biggest deficiency in the free software community today is not in
242 the software---it is the lack of good free documentation that we can
243 include with the free software. Many of our most important
244 programs do not come with free reference manuals and free introductory
245 texts. Documentation is an essential part of any software package;
246 when an important free software package does not come with a free
247 manual and a free tutorial, that is a major gap. We have many such
250 Consider Perl, for instance. The tutorial manuals that people
251 normally use are non-free. How did this come about? Because the
252 authors of those manuals published them with restrictive terms---no
253 copying, no modification, source files not available---which exclude
254 them from the free software world.
256 That wasn't the first time this sort of thing happened, and it was far
257 from the last. Many times we have heard a GNU user eagerly describe a
258 manual that he is writing, his intended contribution to the community,
259 only to learn that he had ruined everything by signing a publication
260 contract to make it non-free.
262 Free documentation, like free software, is a matter of freedom, not
263 price. The problem with the non-free manual is not that publishers
264 charge a price for printed copies---that in itself is fine. (The Free
265 Software Foundation sells printed copies of manuals, too.) The
266 problem is the restrictions on the use of the manual. Free manuals
267 are available in source code form, and give you permission to copy and
268 modify. Non-free manuals do not allow this.
270 The criteria of freedom for a free manual are roughly the same as for
271 free software. Redistribution (including the normal kinds of
272 commercial redistribution) must be permitted, so that the manual can
273 accompany every copy of the program, both on-line and on paper.
275 Permission for modification of the technical content is crucial too.
276 When people modify the software, adding or changing features, if they
277 are conscientious they will change the manual too---so they can
278 provide accurate and clear documentation for the modified program. A
279 manual that leaves you no choice but to write a new manual to document
280 a changed version of the program is not really available to our
283 Some kinds of limits on the way modification is handled are
284 acceptable. For example, requirements to preserve the original
285 author's copyright notice, the distribution terms, or the list of
286 authors, are ok. It is also no problem to require modified versions
287 to include notice that they were modified. Even entire sections that
288 may not be deleted or changed are acceptable, as long as they deal
289 with nontechnical topics (like this one). These kinds of restrictions
290 are acceptable because they don't obstruct the community's normal use
293 However, it must be possible to modify all the @emph{technical}
294 content of the manual, and then distribute the result in all the usual
295 media, through all the usual channels. Otherwise, the restrictions
296 obstruct the use of the manual, it is not free, and we need another
297 manual to replace it.
299 Please spread the word about this issue. Our community continues to
300 lose manuals to proprietary publishing. If we spread the word that
301 free software needs free reference manuals and free tutorials, perhaps
302 the next person who wants to contribute by writing documentation will
303 realize, before it is too late, that only free manuals contribute to
304 the free software community.
306 If you are writing documentation, please insist on publishing it under
307 the GNU Free Documentation License or another free documentation
308 license. Remember that this decision requires your approval---you
309 don't have to let the publisher decide. Some commercial publishers
310 will use a free license if you insist, but they will not propose the
311 option; it is up to you to raise the issue and say firmly that this is
312 what you want. If the publisher you are dealing with refuses, please
313 try other publishers. If you're not sure whether a proposed license
314 is free, write to @email{licensing@@gnu.org}.
316 You can encourage commercial publishers to sell more free, copylefted
317 manuals and tutorials by buying them, and particularly by buying
318 copies from the publishers that paid for their writing or for major
319 improvements. Meanwhile, try to avoid buying non-free documentation
320 at all. Check the distribution terms of a manual before you buy it,
321 and insist that whoever seeks your business must respect your freedom.
322 Check the history of the book, and try to reward the publishers that
323 have paid or pay the authors to work on it.
325 The Free Software Foundation maintains a list of free documentation
326 published by other publishers, at
327 @url{http://www.fsf.org/doc/other-free-books.html}.
330 @unnumberedsec Contributors to @value{GDBN}
332 Richard Stallman was the original author of @value{GDBN}, and of many
333 other @sc{gnu} programs. Many others have contributed to its
334 development. This section attempts to credit major contributors. One
335 of the virtues of free software is that everyone is free to contribute
336 to it; with regret, we cannot actually acknowledge everyone here. The
337 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
338 blow-by-blow account.
340 Changes much prior to version 2.0 are lost in the mists of time.
343 @emph{Plea:} Additions to this section are particularly welcome. If you
344 or your friends (or enemies, to be evenhanded) have been unfairly
345 omitted from this list, we would like to add your names!
348 So that they may not regard their many labors as thankless, we
349 particularly thank those who shepherded @value{GDBN} through major
351 Andrew Cagney (releases 5.3, 5.2, 5.1 and 5.0);
352 Jim Blandy (release 4.18);
353 Jason Molenda (release 4.17);
354 Stan Shebs (release 4.14);
355 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
356 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
357 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
358 Jim Kingdon (releases 3.5, 3.4, and 3.3);
359 and Randy Smith (releases 3.2, 3.1, and 3.0).
361 Richard Stallman, assisted at various times by Peter TerMaat, Chris
362 Hanson, and Richard Mlynarik, handled releases through 2.8.
364 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
365 in @value{GDBN}, with significant additional contributions from Per
366 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
367 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
368 much general update work leading to release 3.0).
370 @value{GDBN} uses the BFD subroutine library to examine multiple
371 object-file formats; BFD was a joint project of David V.
372 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
374 David Johnson wrote the original COFF support; Pace Willison did
375 the original support for encapsulated COFF.
377 Brent Benson of Harris Computer Systems contributed DWARF2 support.
379 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
380 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
382 Jean-Daniel Fekete contributed Sun 386i support.
383 Chris Hanson improved the HP9000 support.
384 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
385 David Johnson contributed Encore Umax support.
386 Jyrki Kuoppala contributed Altos 3068 support.
387 Jeff Law contributed HP PA and SOM support.
388 Keith Packard contributed NS32K support.
389 Doug Rabson contributed Acorn Risc Machine support.
390 Bob Rusk contributed Harris Nighthawk CX-UX support.
391 Chris Smith contributed Convex support (and Fortran debugging).
392 Jonathan Stone contributed Pyramid support.
393 Michael Tiemann contributed SPARC support.
394 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
395 Pace Willison contributed Intel 386 support.
396 Jay Vosburgh contributed Symmetry support.
397 Marko Mlinar contributed OpenRISC 1000 support.
399 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
401 Rich Schaefer and Peter Schauer helped with support of SunOS shared
404 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
405 about several machine instruction sets.
407 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
408 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
409 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
410 and RDI targets, respectively.
412 Brian Fox is the author of the readline libraries providing
413 command-line editing and command history.
415 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
416 Modula-2 support, and contributed the Languages chapter of this manual.
418 Fred Fish wrote most of the support for Unix System Vr4.
419 He also enhanced the command-completion support to cover C@t{++} overloaded
422 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
425 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
427 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
429 Toshiba sponsored the support for the TX39 Mips processor.
431 Matsushita sponsored the support for the MN10200 and MN10300 processors.
433 Fujitsu sponsored the support for SPARClite and FR30 processors.
435 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
438 Michael Snyder added support for tracepoints.
440 Stu Grossman wrote gdbserver.
442 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
443 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
445 The following people at the Hewlett-Packard Company contributed
446 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
447 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
448 compiler, and the terminal user interface: Ben Krepp, Richard Title,
449 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
450 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
451 information in this manual.
453 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
454 Robert Hoehne made significant contributions to the DJGPP port.
456 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
457 development since 1991. Cygnus engineers who have worked on @value{GDBN}
458 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
459 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
460 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
461 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
462 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
463 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
464 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
465 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
466 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
467 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
468 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
469 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
470 Zuhn have made contributions both large and small.
472 Jim Blandy added support for preprocessor macros, while working for Red
476 @chapter A Sample @value{GDBN} Session
478 You can use this manual at your leisure to read all about @value{GDBN}.
479 However, a handful of commands are enough to get started using the
480 debugger. This chapter illustrates those commands.
483 In this sample session, we emphasize user input like this: @b{input},
484 to make it easier to pick out from the surrounding output.
487 @c FIXME: this example may not be appropriate for some configs, where
488 @c FIXME...primary interest is in remote use.
490 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
491 processor) exhibits the following bug: sometimes, when we change its
492 quote strings from the default, the commands used to capture one macro
493 definition within another stop working. In the following short @code{m4}
494 session, we define a macro @code{foo} which expands to @code{0000}; we
495 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
496 same thing. However, when we change the open quote string to
497 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
498 procedure fails to define a new synonym @code{baz}:
507 @b{define(bar,defn(`foo'))}
511 @b{changequote(<QUOTE>,<UNQUOTE>)}
513 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
516 m4: End of input: 0: fatal error: EOF in string
520 Let us use @value{GDBN} to try to see what is going on.
523 $ @b{@value{GDBP} m4}
524 @c FIXME: this falsifies the exact text played out, to permit smallbook
525 @c FIXME... format to come out better.
526 @value{GDBN} is free software and you are welcome to distribute copies
527 of it under certain conditions; type "show copying" to see
529 There is absolutely no warranty for @value{GDBN}; type "show warranty"
532 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
537 @value{GDBN} reads only enough symbol data to know where to find the
538 rest when needed; as a result, the first prompt comes up very quickly.
539 We now tell @value{GDBN} to use a narrower display width than usual, so
540 that examples fit in this manual.
543 (@value{GDBP}) @b{set width 70}
547 We need to see how the @code{m4} built-in @code{changequote} works.
548 Having looked at the source, we know the relevant subroutine is
549 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
550 @code{break} command.
553 (@value{GDBP}) @b{break m4_changequote}
554 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
558 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
559 control; as long as control does not reach the @code{m4_changequote}
560 subroutine, the program runs as usual:
563 (@value{GDBP}) @b{run}
564 Starting program: /work/Editorial/gdb/gnu/m4/m4
572 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
573 suspends execution of @code{m4}, displaying information about the
574 context where it stops.
577 @b{changequote(<QUOTE>,<UNQUOTE>)}
579 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
581 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
585 Now we use the command @code{n} (@code{next}) to advance execution to
586 the next line of the current function.
590 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
595 @code{set_quotes} looks like a promising subroutine. We can go into it
596 by using the command @code{s} (@code{step}) instead of @code{next}.
597 @code{step} goes to the next line to be executed in @emph{any}
598 subroutine, so it steps into @code{set_quotes}.
602 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
604 530 if (lquote != def_lquote)
608 The display that shows the subroutine where @code{m4} is now
609 suspended (and its arguments) is called a stack frame display. It
610 shows a summary of the stack. We can use the @code{backtrace}
611 command (which can also be spelled @code{bt}), to see where we are
612 in the stack as a whole: the @code{backtrace} command displays a
613 stack frame for each active subroutine.
616 (@value{GDBP}) @b{bt}
617 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
619 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
621 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
622 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
624 #4 0x79dc in expand_input () at macro.c:40
625 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
629 We step through a few more lines to see what happens. The first two
630 times, we can use @samp{s}; the next two times we use @code{n} to avoid
631 falling into the @code{xstrdup} subroutine.
635 0x3b5c 532 if (rquote != def_rquote)
637 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
638 def_lquote : xstrdup(lq);
640 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
643 538 len_lquote = strlen(rquote);
647 The last line displayed looks a little odd; we can examine the variables
648 @code{lquote} and @code{rquote} to see if they are in fact the new left
649 and right quotes we specified. We use the command @code{p}
650 (@code{print}) to see their values.
653 (@value{GDBP}) @b{p lquote}
654 $1 = 0x35d40 "<QUOTE>"
655 (@value{GDBP}) @b{p rquote}
656 $2 = 0x35d50 "<UNQUOTE>"
660 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
661 To look at some context, we can display ten lines of source
662 surrounding the current line with the @code{l} (@code{list}) command.
668 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
670 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
673 538 len_lquote = strlen(rquote);
674 539 len_rquote = strlen(lquote);
681 Let us step past the two lines that set @code{len_lquote} and
682 @code{len_rquote}, and then examine the values of those variables.
686 539 len_rquote = strlen(lquote);
689 (@value{GDBP}) @b{p len_lquote}
691 (@value{GDBP}) @b{p len_rquote}
696 That certainly looks wrong, assuming @code{len_lquote} and
697 @code{len_rquote} are meant to be the lengths of @code{lquote} and
698 @code{rquote} respectively. We can set them to better values using
699 the @code{p} command, since it can print the value of
700 any expression---and that expression can include subroutine calls and
704 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
706 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
711 Is that enough to fix the problem of using the new quotes with the
712 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
713 executing with the @code{c} (@code{continue}) command, and then try the
714 example that caused trouble initially:
720 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
727 Success! The new quotes now work just as well as the default ones. The
728 problem seems to have been just the two typos defining the wrong
729 lengths. We allow @code{m4} exit by giving it an EOF as input:
733 Program exited normally.
737 The message @samp{Program exited normally.} is from @value{GDBN}; it
738 indicates @code{m4} has finished executing. We can end our @value{GDBN}
739 session with the @value{GDBN} @code{quit} command.
742 (@value{GDBP}) @b{quit}
746 @chapter Getting In and Out of @value{GDBN}
748 This chapter discusses how to start @value{GDBN}, and how to get out of it.
752 type @samp{@value{GDBP}} to start @value{GDBN}.
754 type @kbd{quit} or @kbd{C-d} to exit.
758 * Invoking GDB:: How to start @value{GDBN}
759 * Quitting GDB:: How to quit @value{GDBN}
760 * Shell Commands:: How to use shell commands inside @value{GDBN}
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}).
1058 Annotation level controls how much information does @value{GDBN} print
1059 together with its prompt, values of expressions, source lines, and other
1060 types of output. Level 0 is the normal, level 1 is for use when
1061 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1062 maximum annotation suitable for programs that control @value{GDBN}.
1065 @cindex @code{--async}
1066 Use the asynchronous event loop for the command-line interface.
1067 @value{GDBN} processes all events, such as user keyboard input, via a
1068 special event loop. This allows @value{GDBN} to accept and process user
1069 commands in parallel with the debugged process being
1070 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1071 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1072 suspended when the debuggee runs.}, so you don't need to wait for
1073 control to return to @value{GDBN} before you type the next command.
1074 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1075 operation is not yet in place, so @samp{-async} does not work fully
1077 @c FIXME: when the target side of the event loop is done, the above NOTE
1078 @c should be removed.
1080 When the standard input is connected to a terminal device, @value{GDBN}
1081 uses the asynchronous event loop by default, unless disabled by the
1082 @samp{-noasync} option.
1085 @cindex @code{--noasync}
1086 Disable the asynchronous event loop for the command-line interface.
1089 @cindex @code{--args}
1090 Change interpretation of command line so that arguments following the
1091 executable file are passed as command line arguments to the inferior.
1092 This option stops option processing.
1094 @item -baud @var{bps}
1096 @cindex @code{--baud}
1098 Set the line speed (baud rate or bits per second) of any serial
1099 interface used by @value{GDBN} for remote debugging.
1101 @item -tty @var{device}
1102 @itemx -t @var{device}
1103 @cindex @code{--tty}
1105 Run using @var{device} for your program's standard input and output.
1106 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1108 @c resolve the situation of these eventually
1110 @cindex @code{--tui}
1111 Activate the Terminal User Interface when starting.
1112 The Terminal User Interface manages several text windows on the terminal,
1113 showing source, assembly, registers and @value{GDBN} command outputs
1114 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1115 Do not use this option if you run @value{GDBN} from Emacs
1116 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1119 @c @cindex @code{--xdb}
1120 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1121 @c For information, see the file @file{xdb_trans.html}, which is usually
1122 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1125 @item -interpreter @var{interp}
1126 @cindex @code{--interpreter}
1127 Use the interpreter @var{interp} for interface with the controlling
1128 program or device. This option is meant to be set by programs which
1129 communicate with @value{GDBN} using it as a back end.
1131 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1132 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1133 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1134 interface, included in @value{GDBN} version 5.3, can be selected with
1135 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1139 @cindex @code{--write}
1140 Open the executable and core files for both reading and writing. This
1141 is equivalent to the @samp{set write on} command inside @value{GDBN}
1145 @cindex @code{--statistics}
1146 This option causes @value{GDBN} to print statistics about time and
1147 memory usage after it completes each command and returns to the prompt.
1150 @cindex @code{--version}
1151 This option causes @value{GDBN} to print its version number and
1152 no-warranty blurb, and exit.
1157 @section Quitting @value{GDBN}
1158 @cindex exiting @value{GDBN}
1159 @cindex leaving @value{GDBN}
1162 @kindex quit @r{[}@var{expression}@r{]}
1163 @kindex q @r{(@code{quit})}
1164 @item quit @r{[}@var{expression}@r{]}
1166 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1167 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1168 do not supply @var{expression}, @value{GDBN} will terminate normally;
1169 otherwise it will terminate using the result of @var{expression} as the
1174 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1175 terminates the action of any @value{GDBN} command that is in progress and
1176 returns to @value{GDBN} command level. It is safe to type the interrupt
1177 character at any time because @value{GDBN} does not allow it to take effect
1178 until a time when it is safe.
1180 If you have been using @value{GDBN} to control an attached process or
1181 device, you can release it with the @code{detach} command
1182 (@pxref{Attach, ,Debugging an already-running process}).
1184 @node Shell Commands
1185 @section Shell commands
1187 If you need to execute occasional shell commands during your
1188 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1189 just use the @code{shell} command.
1193 @cindex shell escape
1194 @item shell @var{command string}
1195 Invoke a standard shell to execute @var{command string}.
1196 If it exists, the environment variable @code{SHELL} determines which
1197 shell to run. Otherwise @value{GDBN} uses the default shell
1198 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1201 The utility @code{make} is often needed in development environments.
1202 You do not have to use the @code{shell} command for this purpose in
1207 @cindex calling make
1208 @item make @var{make-args}
1209 Execute the @code{make} program with the specified
1210 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1214 @chapter @value{GDBN} Commands
1216 You can abbreviate a @value{GDBN} command to the first few letters of the command
1217 name, if that abbreviation is unambiguous; and you can repeat certain
1218 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1219 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1220 show you the alternatives available, if there is more than one possibility).
1223 * Command Syntax:: How to give commands to @value{GDBN}
1224 * Completion:: Command completion
1225 * Help:: How to ask @value{GDBN} for help
1228 @node Command Syntax
1229 @section Command syntax
1231 A @value{GDBN} command is a single line of input. There is no limit on
1232 how long it can be. It starts with a command name, which is followed by
1233 arguments whose meaning depends on the command name. For example, the
1234 command @code{step} accepts an argument which is the number of times to
1235 step, as in @samp{step 5}. You can also use the @code{step} command
1236 with no arguments. Some commands do not allow any arguments.
1238 @cindex abbreviation
1239 @value{GDBN} command names may always be truncated if that abbreviation is
1240 unambiguous. Other possible command abbreviations are listed in the
1241 documentation for individual commands. In some cases, even ambiguous
1242 abbreviations are allowed; for example, @code{s} is specially defined as
1243 equivalent to @code{step} even though there are other commands whose
1244 names start with @code{s}. You can test abbreviations by using them as
1245 arguments to the @code{help} command.
1247 @cindex repeating commands
1248 @kindex RET @r{(repeat last command)}
1249 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1250 repeat the previous command. Certain commands (for example, @code{run})
1251 will not repeat this way; these are commands whose unintentional
1252 repetition might cause trouble and which you are unlikely to want to
1255 The @code{list} and @code{x} commands, when you repeat them with
1256 @key{RET}, construct new arguments rather than repeating
1257 exactly as typed. This permits easy scanning of source or memory.
1259 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1260 output, in a way similar to the common utility @code{more}
1261 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1262 @key{RET} too many in this situation, @value{GDBN} disables command
1263 repetition after any command that generates this sort of display.
1265 @kindex # @r{(a comment)}
1267 Any text from a @kbd{#} to the end of the line is a comment; it does
1268 nothing. This is useful mainly in command files (@pxref{Command
1269 Files,,Command files}).
1271 @cindex repeating command sequences
1272 @kindex C-o @r{(operate-and-get-next)}
1273 The @kbd{C-o} binding is useful for repeating a complex sequence of
1274 commands. This command accepts the current line, like @kbd{RET}, and
1275 then fetches the next line relative to the current line from the history
1279 @section Command completion
1282 @cindex word completion
1283 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1284 only one possibility; it can also show you what the valid possibilities
1285 are for the next word in a command, at any time. This works for @value{GDBN}
1286 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1288 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1289 of a word. If there is only one possibility, @value{GDBN} fills in the
1290 word, and waits for you to finish the command (or press @key{RET} to
1291 enter it). For example, if you type
1293 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1294 @c complete accuracy in these examples; space introduced for clarity.
1295 @c If texinfo enhancements make it unnecessary, it would be nice to
1296 @c replace " @key" by "@key" in the following...
1298 (@value{GDBP}) info bre @key{TAB}
1302 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1303 the only @code{info} subcommand beginning with @samp{bre}:
1306 (@value{GDBP}) info breakpoints
1310 You can either press @key{RET} at this point, to run the @code{info
1311 breakpoints} command, or backspace and enter something else, if
1312 @samp{breakpoints} does not look like the command you expected. (If you
1313 were sure you wanted @code{info breakpoints} in the first place, you
1314 might as well just type @key{RET} immediately after @samp{info bre},
1315 to exploit command abbreviations rather than command completion).
1317 If there is more than one possibility for the next word when you press
1318 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1319 characters and try again, or just press @key{TAB} a second time;
1320 @value{GDBN} displays all the possible completions for that word. For
1321 example, you might want to set a breakpoint on a subroutine whose name
1322 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1323 just sounds the bell. Typing @key{TAB} again displays all the
1324 function names in your program that begin with those characters, for
1328 (@value{GDBP}) b make_ @key{TAB}
1329 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1330 make_a_section_from_file make_environ
1331 make_abs_section make_function_type
1332 make_blockvector make_pointer_type
1333 make_cleanup make_reference_type
1334 make_command make_symbol_completion_list
1335 (@value{GDBP}) b make_
1339 After displaying the available possibilities, @value{GDBN} copies your
1340 partial input (@samp{b make_} in the example) so you can finish the
1343 If you just want to see the list of alternatives in the first place, you
1344 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1345 means @kbd{@key{META} ?}. You can type this either by holding down a
1346 key designated as the @key{META} shift on your keyboard (if there is
1347 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1349 @cindex quotes in commands
1350 @cindex completion of quoted strings
1351 Sometimes the string you need, while logically a ``word'', may contain
1352 parentheses or other characters that @value{GDBN} normally excludes from
1353 its notion of a word. To permit word completion to work in this
1354 situation, you may enclose words in @code{'} (single quote marks) in
1355 @value{GDBN} commands.
1357 The most likely situation where you might need this is in typing the
1358 name of a C@t{++} function. This is because C@t{++} allows function
1359 overloading (multiple definitions of the same function, distinguished
1360 by argument type). For example, when you want to set a breakpoint you
1361 may need to distinguish whether you mean the version of @code{name}
1362 that takes an @code{int} parameter, @code{name(int)}, or the version
1363 that takes a @code{float} parameter, @code{name(float)}. To use the
1364 word-completion facilities in this situation, type a single quote
1365 @code{'} at the beginning of the function name. This alerts
1366 @value{GDBN} that it may need to consider more information than usual
1367 when you press @key{TAB} or @kbd{M-?} to request word completion:
1370 (@value{GDBP}) b 'bubble( @kbd{M-?}
1371 bubble(double,double) bubble(int,int)
1372 (@value{GDBP}) b 'bubble(
1375 In some cases, @value{GDBN} can tell that completing a name requires using
1376 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1377 completing as much as it can) if you do not type the quote in the first
1381 (@value{GDBP}) b bub @key{TAB}
1382 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1383 (@value{GDBP}) b 'bubble(
1387 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1388 you have not yet started typing the argument list when you ask for
1389 completion on an overloaded symbol.
1391 For more information about overloaded functions, see @ref{C plus plus
1392 expressions, ,C@t{++} expressions}. You can use the command @code{set
1393 overload-resolution off} to disable overload resolution;
1394 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1398 @section Getting help
1399 @cindex online documentation
1402 You can always ask @value{GDBN} itself for information on its commands,
1403 using the command @code{help}.
1406 @kindex h @r{(@code{help})}
1409 You can use @code{help} (abbreviated @code{h}) with no arguments to
1410 display a short list of named classes of commands:
1414 List of classes of commands:
1416 aliases -- Aliases of other commands
1417 breakpoints -- Making program stop at certain points
1418 data -- Examining data
1419 files -- Specifying and examining files
1420 internals -- Maintenance commands
1421 obscure -- Obscure features
1422 running -- Running the program
1423 stack -- Examining the stack
1424 status -- Status inquiries
1425 support -- Support facilities
1426 tracepoints -- Tracing of program execution without@*
1427 stopping the program
1428 user-defined -- User-defined commands
1430 Type "help" followed by a class name for a list of
1431 commands in that class.
1432 Type "help" followed by command name for full
1434 Command name abbreviations are allowed if unambiguous.
1437 @c the above line break eliminates huge line overfull...
1439 @item help @var{class}
1440 Using one of the general help classes as an argument, you can get a
1441 list of the individual commands in that class. For example, here is the
1442 help display for the class @code{status}:
1445 (@value{GDBP}) help status
1450 @c Line break in "show" line falsifies real output, but needed
1451 @c to fit in smallbook page size.
1452 info -- Generic command for showing things
1453 about the program being debugged
1454 show -- Generic command for showing things
1457 Type "help" followed by command name for full
1459 Command name abbreviations are allowed if unambiguous.
1463 @item help @var{command}
1464 With a command name as @code{help} argument, @value{GDBN} displays a
1465 short paragraph on how to use that command.
1468 @item apropos @var{args}
1469 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1470 commands, and their documentation, for the regular expression specified in
1471 @var{args}. It prints out all matches found. For example:
1482 set symbol-reloading -- Set dynamic symbol table reloading
1483 multiple times in one run
1484 show symbol-reloading -- Show dynamic symbol table reloading
1485 multiple times in one run
1490 @item complete @var{args}
1491 The @code{complete @var{args}} command lists all the possible completions
1492 for the beginning of a command. Use @var{args} to specify the beginning of the
1493 command you want completed. For example:
1499 @noindent results in:
1510 @noindent This is intended for use by @sc{gnu} Emacs.
1513 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1514 and @code{show} to inquire about the state of your program, or the state
1515 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1516 manual introduces each of them in the appropriate context. The listings
1517 under @code{info} and under @code{show} in the Index point to
1518 all the sub-commands. @xref{Index}.
1523 @kindex i @r{(@code{info})}
1525 This command (abbreviated @code{i}) is for describing the state of your
1526 program. For example, you can list the arguments given to your program
1527 with @code{info args}, list the registers currently in use with @code{info
1528 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1529 You can get a complete list of the @code{info} sub-commands with
1530 @w{@code{help info}}.
1534 You can assign the result of an expression to an environment variable with
1535 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1536 @code{set prompt $}.
1540 In contrast to @code{info}, @code{show} is for describing the state of
1541 @value{GDBN} itself.
1542 You can change most of the things you can @code{show}, by using the
1543 related command @code{set}; for example, you can control what number
1544 system is used for displays with @code{set radix}, or simply inquire
1545 which is currently in use with @code{show radix}.
1548 To display all the settable parameters and their current
1549 values, you can use @code{show} with no arguments; you may also use
1550 @code{info set}. Both commands produce the same display.
1551 @c FIXME: "info set" violates the rule that "info" is for state of
1552 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1553 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1557 Here are three miscellaneous @code{show} subcommands, all of which are
1558 exceptional in lacking corresponding @code{set} commands:
1561 @kindex show version
1562 @cindex version number
1564 Show what version of @value{GDBN} is running. You should include this
1565 information in @value{GDBN} bug-reports. If multiple versions of
1566 @value{GDBN} are in use at your site, you may need to determine which
1567 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1568 commands are introduced, and old ones may wither away. Also, many
1569 system vendors ship variant versions of @value{GDBN}, and there are
1570 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1571 The version number is the same as the one announced when you start
1574 @kindex show copying
1576 Display information about permission for copying @value{GDBN}.
1578 @kindex show warranty
1580 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1581 if your version of @value{GDBN} comes with one.
1586 @chapter Running Programs Under @value{GDBN}
1588 When you run a program under @value{GDBN}, you must first generate
1589 debugging information when you compile it.
1591 You may start @value{GDBN} with its arguments, if any, in an environment
1592 of your choice. If you are doing native debugging, you may redirect
1593 your program's input and output, debug an already running process, or
1594 kill a child process.
1597 * Compilation:: Compiling for debugging
1598 * Starting:: Starting your program
1599 * Arguments:: Your program's arguments
1600 * Environment:: Your program's environment
1602 * Working Directory:: Your program's working directory
1603 * Input/Output:: Your program's input and output
1604 * Attach:: Debugging an already-running process
1605 * Kill Process:: Killing the child process
1607 * Threads:: Debugging programs with multiple threads
1608 * Processes:: Debugging programs with multiple processes
1612 @section Compiling for debugging
1614 In order to debug a program effectively, you need to generate
1615 debugging information when you compile it. This debugging information
1616 is stored in the object file; it describes the data type of each
1617 variable or function and the correspondence between source line numbers
1618 and addresses in the executable code.
1620 To request debugging information, specify the @samp{-g} option when you run
1623 Most compilers do not include information about preprocessor macros in
1624 the debugging information if you specify the @option{-g} flag alone,
1625 because this information is rather large. Version 3.1 of @value{NGCC},
1626 the @sc{gnu} C compiler, provides macro information if you specify the
1627 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1628 debugging information in the Dwarf 2 format, and the latter requests
1629 ``extra information''. In the future, we hope to find more compact ways
1630 to represent macro information, so that it can be included with
1633 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1634 options together. Using those compilers, you cannot generate optimized
1635 executables containing debugging information.
1637 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1638 without @samp{-O}, making it possible to debug optimized code. We
1639 recommend that you @emph{always} use @samp{-g} whenever you compile a
1640 program. You may think your program is correct, but there is no sense
1641 in pushing your luck.
1643 @cindex optimized code, debugging
1644 @cindex debugging optimized code
1645 When you debug a program compiled with @samp{-g -O}, remember that the
1646 optimizer is rearranging your code; the debugger shows you what is
1647 really there. Do not be too surprised when the execution path does not
1648 exactly match your source file! An extreme example: if you define a
1649 variable, but never use it, @value{GDBN} never sees that
1650 variable---because the compiler optimizes it out of existence.
1652 Some things do not work as well with @samp{-g -O} as with just
1653 @samp{-g}, particularly on machines with instruction scheduling. If in
1654 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1655 please report it to us as a bug (including a test case!).
1657 Older versions of the @sc{gnu} C compiler permitted a variant option
1658 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1659 format; if your @sc{gnu} C compiler has this option, do not use it.
1663 @section Starting your program
1669 @kindex r @r{(@code{run})}
1672 Use the @code{run} command to start your program under @value{GDBN}.
1673 You must first specify the program name (except on VxWorks) with an
1674 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1675 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1676 (@pxref{Files, ,Commands to specify files}).
1680 If you are running your program in an execution environment that
1681 supports processes, @code{run} creates an inferior process and makes
1682 that process run your program. (In environments without processes,
1683 @code{run} jumps to the start of your program.)
1685 The execution of a program is affected by certain information it
1686 receives from its superior. @value{GDBN} provides ways to specify this
1687 information, which you must do @emph{before} starting your program. (You
1688 can change it after starting your program, but such changes only affect
1689 your program the next time you start it.) This information may be
1690 divided into four categories:
1693 @item The @emph{arguments.}
1694 Specify the arguments to give your program as the arguments of the
1695 @code{run} command. If a shell is available on your target, the shell
1696 is used to pass the arguments, so that you may use normal conventions
1697 (such as wildcard expansion or variable substitution) in describing
1699 In Unix systems, you can control which shell is used with the
1700 @code{SHELL} environment variable.
1701 @xref{Arguments, ,Your program's arguments}.
1703 @item The @emph{environment.}
1704 Your program normally inherits its environment from @value{GDBN}, but you can
1705 use the @value{GDBN} commands @code{set environment} and @code{unset
1706 environment} to change parts of the environment that affect
1707 your program. @xref{Environment, ,Your program's environment}.
1709 @item The @emph{working directory.}
1710 Your program inherits its working directory from @value{GDBN}. You can set
1711 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1712 @xref{Working Directory, ,Your program's working directory}.
1714 @item The @emph{standard input and output.}
1715 Your program normally uses the same device for standard input and
1716 standard output as @value{GDBN} is using. You can redirect input and output
1717 in the @code{run} command line, or you can use the @code{tty} command to
1718 set a different device for your program.
1719 @xref{Input/Output, ,Your program's input and output}.
1722 @emph{Warning:} While input and output redirection work, you cannot use
1723 pipes to pass the output of the program you are debugging to another
1724 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1728 When you issue the @code{run} command, your program begins to execute
1729 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1730 of how to arrange for your program to stop. Once your program has
1731 stopped, you may call functions in your program, using the @code{print}
1732 or @code{call} commands. @xref{Data, ,Examining Data}.
1734 If the modification time of your symbol file has changed since the last
1735 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1736 table, and reads it again. When it does this, @value{GDBN} tries to retain
1737 your current breakpoints.
1740 @section Your program's arguments
1742 @cindex arguments (to your program)
1743 The arguments to your program can be specified by the arguments of the
1745 They are passed to a shell, which expands wildcard characters and
1746 performs redirection of I/O, and thence to your program. Your
1747 @code{SHELL} environment variable (if it exists) specifies what shell
1748 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1749 the default shell (@file{/bin/sh} on Unix).
1751 On non-Unix systems, the program is usually invoked directly by
1752 @value{GDBN}, which emulates I/O redirection via the appropriate system
1753 calls, and the wildcard characters are expanded by the startup code of
1754 the program, not by the shell.
1756 @code{run} with no arguments uses the same arguments used by the previous
1757 @code{run}, or those set by the @code{set args} command.
1762 Specify the arguments to be used the next time your program is run. If
1763 @code{set args} has no arguments, @code{run} executes your program
1764 with no arguments. Once you have run your program with arguments,
1765 using @code{set args} before the next @code{run} is the only way to run
1766 it again without arguments.
1770 Show the arguments to give your program when it is started.
1774 @section Your program's environment
1776 @cindex environment (of your program)
1777 The @dfn{environment} consists of a set of environment variables and
1778 their values. Environment variables conventionally record such things as
1779 your user name, your home directory, your terminal type, and your search
1780 path for programs to run. Usually you set up environment variables with
1781 the shell and they are inherited by all the other programs you run. When
1782 debugging, it can be useful to try running your program with a modified
1783 environment without having to start @value{GDBN} over again.
1787 @item path @var{directory}
1788 Add @var{directory} to the front of the @code{PATH} environment variable
1789 (the search path for executables) that will be passed to your program.
1790 The value of @code{PATH} used by @value{GDBN} does not change.
1791 You may specify several directory names, separated by whitespace or by a
1792 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1793 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1794 is moved to the front, so it is searched sooner.
1796 You can use the string @samp{$cwd} to refer to whatever is the current
1797 working directory at the time @value{GDBN} searches the path. If you
1798 use @samp{.} instead, it refers to the directory where you executed the
1799 @code{path} command. @value{GDBN} replaces @samp{.} in the
1800 @var{directory} argument (with the current path) before adding
1801 @var{directory} to the search path.
1802 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1803 @c document that, since repeating it would be a no-op.
1807 Display the list of search paths for executables (the @code{PATH}
1808 environment variable).
1810 @kindex show environment
1811 @item show environment @r{[}@var{varname}@r{]}
1812 Print the value of environment variable @var{varname} to be given to
1813 your program when it starts. If you do not supply @var{varname},
1814 print the names and values of all environment variables to be given to
1815 your program. You can abbreviate @code{environment} as @code{env}.
1817 @kindex set environment
1818 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1819 Set environment variable @var{varname} to @var{value}. The value
1820 changes for your program only, not for @value{GDBN} itself. @var{value} may
1821 be any string; the values of environment variables are just strings, and
1822 any interpretation is supplied by your program itself. The @var{value}
1823 parameter is optional; if it is eliminated, the variable is set to a
1825 @c "any string" here does not include leading, trailing
1826 @c blanks. Gnu asks: does anyone care?
1828 For example, this command:
1835 tells the debugged program, when subsequently run, that its user is named
1836 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1837 are not actually required.)
1839 @kindex unset environment
1840 @item unset environment @var{varname}
1841 Remove variable @var{varname} from the environment to be passed to your
1842 program. This is different from @samp{set env @var{varname} =};
1843 @code{unset environment} removes the variable from the environment,
1844 rather than assigning it an empty value.
1847 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1849 by your @code{SHELL} environment variable if it exists (or
1850 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1851 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1852 @file{.bashrc} for BASH---any variables you set in that file affect
1853 your program. You may wish to move setting of environment variables to
1854 files that are only run when you sign on, such as @file{.login} or
1857 @node Working Directory
1858 @section Your program's working directory
1860 @cindex working directory (of your program)
1861 Each time you start your program with @code{run}, it inherits its
1862 working directory from the current working directory of @value{GDBN}.
1863 The @value{GDBN} working directory is initially whatever it inherited
1864 from its parent process (typically the shell), but you can specify a new
1865 working directory in @value{GDBN} with the @code{cd} command.
1867 The @value{GDBN} working directory also serves as a default for the commands
1868 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1873 @item cd @var{directory}
1874 Set the @value{GDBN} working directory to @var{directory}.
1878 Print the @value{GDBN} working directory.
1882 @section Your program's input and output
1887 By default, the program you run under @value{GDBN} does input and output to
1888 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1889 to its own terminal modes to interact with you, but it records the terminal
1890 modes your program was using and switches back to them when you continue
1891 running your program.
1894 @kindex info terminal
1896 Displays information recorded by @value{GDBN} about the terminal modes your
1900 You can redirect your program's input and/or output using shell
1901 redirection with the @code{run} command. For example,
1908 starts your program, diverting its output to the file @file{outfile}.
1911 @cindex controlling terminal
1912 Another way to specify where your program should do input and output is
1913 with the @code{tty} command. This command accepts a file name as
1914 argument, and causes this file to be the default for future @code{run}
1915 commands. It also resets the controlling terminal for the child
1916 process, for future @code{run} commands. For example,
1923 directs that processes started with subsequent @code{run} commands
1924 default to do input and output on the terminal @file{/dev/ttyb} and have
1925 that as their controlling terminal.
1927 An explicit redirection in @code{run} overrides the @code{tty} command's
1928 effect on the input/output device, but not its effect on the controlling
1931 When you use the @code{tty} command or redirect input in the @code{run}
1932 command, only the input @emph{for your program} is affected. The input
1933 for @value{GDBN} still comes from your terminal.
1936 @section Debugging an already-running process
1941 @item attach @var{process-id}
1942 This command attaches to a running process---one that was started
1943 outside @value{GDBN}. (@code{info files} shows your active
1944 targets.) The command takes as argument a process ID. The usual way to
1945 find out the process-id of a Unix process is with the @code{ps} utility,
1946 or with the @samp{jobs -l} shell command.
1948 @code{attach} does not repeat if you press @key{RET} a second time after
1949 executing the command.
1952 To use @code{attach}, your program must be running in an environment
1953 which supports processes; for example, @code{attach} does not work for
1954 programs on bare-board targets that lack an operating system. You must
1955 also have permission to send the process a signal.
1957 When you use @code{attach}, the debugger finds the program running in
1958 the process first by looking in the current working directory, then (if
1959 the program is not found) by using the source file search path
1960 (@pxref{Source Path, ,Specifying source directories}). You can also use
1961 the @code{file} command to load the program. @xref{Files, ,Commands to
1964 The first thing @value{GDBN} does after arranging to debug the specified
1965 process is to stop it. You can examine and modify an attached process
1966 with all the @value{GDBN} commands that are ordinarily available when
1967 you start processes with @code{run}. You can insert breakpoints; you
1968 can step and continue; you can modify storage. If you would rather the
1969 process continue running, you may use the @code{continue} command after
1970 attaching @value{GDBN} to the process.
1975 When you have finished debugging the attached process, you can use the
1976 @code{detach} command to release it from @value{GDBN} control. Detaching
1977 the process continues its execution. After the @code{detach} command,
1978 that process and @value{GDBN} become completely independent once more, and you
1979 are ready to @code{attach} another process or start one with @code{run}.
1980 @code{detach} does not repeat if you press @key{RET} again after
1981 executing the command.
1984 If you exit @value{GDBN} or use the @code{run} command while you have an
1985 attached process, you kill that process. By default, @value{GDBN} asks
1986 for confirmation if you try to do either of these things; you can
1987 control whether or not you need to confirm by using the @code{set
1988 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1992 @section Killing the child process
1997 Kill the child process in which your program is running under @value{GDBN}.
2000 This command is useful if you wish to debug a core dump instead of a
2001 running process. @value{GDBN} ignores any core dump file while your program
2004 On some operating systems, a program cannot be executed outside @value{GDBN}
2005 while you have breakpoints set on it inside @value{GDBN}. You can use the
2006 @code{kill} command in this situation to permit running your program
2007 outside the debugger.
2009 The @code{kill} command is also useful if you wish to recompile and
2010 relink your program, since on many systems it is impossible to modify an
2011 executable file while it is running in a process. In this case, when you
2012 next type @code{run}, @value{GDBN} notices that the file has changed, and
2013 reads the symbol table again (while trying to preserve your current
2014 breakpoint settings).
2017 @section Debugging programs with multiple threads
2019 @cindex threads of execution
2020 @cindex multiple threads
2021 @cindex switching threads
2022 In some operating systems, such as HP-UX and Solaris, a single program
2023 may have more than one @dfn{thread} of execution. The precise semantics
2024 of threads differ from one operating system to another, but in general
2025 the threads of a single program are akin to multiple processes---except
2026 that they share one address space (that is, they can all examine and
2027 modify the same variables). On the other hand, each thread has its own
2028 registers and execution stack, and perhaps private memory.
2030 @value{GDBN} provides these facilities for debugging multi-thread
2034 @item automatic notification of new threads
2035 @item @samp{thread @var{threadno}}, a command to switch among threads
2036 @item @samp{info threads}, a command to inquire about existing threads
2037 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2038 a command to apply a command to a list of threads
2039 @item thread-specific breakpoints
2043 @emph{Warning:} These facilities are not yet available on every
2044 @value{GDBN} configuration where the operating system supports threads.
2045 If your @value{GDBN} does not support threads, these commands have no
2046 effect. For example, a system without thread support shows no output
2047 from @samp{info threads}, and always rejects the @code{thread} command,
2051 (@value{GDBP}) info threads
2052 (@value{GDBP}) thread 1
2053 Thread ID 1 not known. Use the "info threads" command to
2054 see the IDs of currently known threads.
2056 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2057 @c doesn't support threads"?
2060 @cindex focus of debugging
2061 @cindex current thread
2062 The @value{GDBN} thread debugging facility allows you to observe all
2063 threads while your program runs---but whenever @value{GDBN} takes
2064 control, one thread in particular is always the focus of debugging.
2065 This thread is called the @dfn{current thread}. Debugging commands show
2066 program information from the perspective of the current thread.
2068 @cindex @code{New} @var{systag} message
2069 @cindex thread identifier (system)
2070 @c FIXME-implementors!! It would be more helpful if the [New...] message
2071 @c included GDB's numeric thread handle, so you could just go to that
2072 @c thread without first checking `info threads'.
2073 Whenever @value{GDBN} detects a new thread in your program, it displays
2074 the target system's identification for the thread with a message in the
2075 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2076 whose form varies depending on the particular system. For example, on
2077 LynxOS, you might see
2080 [New process 35 thread 27]
2084 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2085 the @var{systag} is simply something like @samp{process 368}, with no
2088 @c FIXME!! (1) Does the [New...] message appear even for the very first
2089 @c thread of a program, or does it only appear for the
2090 @c second---i.e.@: when it becomes obvious we have a multithread
2092 @c (2) *Is* there necessarily a first thread always? Or do some
2093 @c multithread systems permit starting a program with multiple
2094 @c threads ab initio?
2096 @cindex thread number
2097 @cindex thread identifier (GDB)
2098 For debugging purposes, @value{GDBN} associates its own thread
2099 number---always a single integer---with each thread in your program.
2102 @kindex info threads
2104 Display a summary of all threads currently in your
2105 program. @value{GDBN} displays for each thread (in this order):
2108 @item the thread number assigned by @value{GDBN}
2110 @item the target system's thread identifier (@var{systag})
2112 @item the current stack frame summary for that thread
2116 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2117 indicates the current thread.
2121 @c end table here to get a little more width for example
2124 (@value{GDBP}) info threads
2125 3 process 35 thread 27 0x34e5 in sigpause ()
2126 2 process 35 thread 23 0x34e5 in sigpause ()
2127 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2133 @cindex thread number
2134 @cindex thread identifier (GDB)
2135 For debugging purposes, @value{GDBN} associates its own thread
2136 number---a small integer assigned in thread-creation order---with each
2137 thread in your program.
2139 @cindex @code{New} @var{systag} message, on HP-UX
2140 @cindex thread identifier (system), on HP-UX
2141 @c FIXME-implementors!! It would be more helpful if the [New...] message
2142 @c included GDB's numeric thread handle, so you could just go to that
2143 @c thread without first checking `info threads'.
2144 Whenever @value{GDBN} detects a new thread in your program, it displays
2145 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2146 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2147 whose form varies depending on the particular system. For example, on
2151 [New thread 2 (system thread 26594)]
2155 when @value{GDBN} notices a new thread.
2158 @kindex info threads
2160 Display a summary of all threads currently in your
2161 program. @value{GDBN} displays for each thread (in this order):
2164 @item the thread number assigned by @value{GDBN}
2166 @item the target system's thread identifier (@var{systag})
2168 @item the current stack frame summary for that thread
2172 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2173 indicates the current thread.
2177 @c end table here to get a little more width for example
2180 (@value{GDBP}) info threads
2181 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2183 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2184 from /usr/lib/libc.2
2185 1 system thread 27905 0x7b003498 in _brk () \@*
2186 from /usr/lib/libc.2
2190 @kindex thread @var{threadno}
2191 @item thread @var{threadno}
2192 Make thread number @var{threadno} the current thread. The command
2193 argument @var{threadno} is the internal @value{GDBN} thread number, as
2194 shown in the first field of the @samp{info threads} display.
2195 @value{GDBN} responds by displaying the system identifier of the thread
2196 you selected, and its current stack frame summary:
2199 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2200 (@value{GDBP}) thread 2
2201 [Switching to process 35 thread 23]
2202 0x34e5 in sigpause ()
2206 As with the @samp{[New @dots{}]} message, the form of the text after
2207 @samp{Switching to} depends on your system's conventions for identifying
2210 @kindex thread apply
2211 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2212 The @code{thread apply} command allows you to apply a command to one or
2213 more threads. Specify the numbers of the threads that you want affected
2214 with the command argument @var{threadno}. @var{threadno} is the internal
2215 @value{GDBN} thread number, as shown in the first field of the @samp{info
2216 threads} display. To apply a command to all threads, use
2217 @code{thread apply all} @var{args}.
2220 @cindex automatic thread selection
2221 @cindex switching threads automatically
2222 @cindex threads, automatic switching
2223 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2224 signal, it automatically selects the thread where that breakpoint or
2225 signal happened. @value{GDBN} alerts you to the context switch with a
2226 message of the form @samp{[Switching to @var{systag}]} to identify the
2229 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2230 more information about how @value{GDBN} behaves when you stop and start
2231 programs with multiple threads.
2233 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2234 watchpoints in programs with multiple threads.
2237 @section Debugging programs with multiple processes
2239 @cindex fork, debugging programs which call
2240 @cindex multiple processes
2241 @cindex processes, multiple
2242 On most systems, @value{GDBN} has no special support for debugging
2243 programs which create additional processes using the @code{fork}
2244 function. When a program forks, @value{GDBN} will continue to debug the
2245 parent process and the child process will run unimpeded. If you have
2246 set a breakpoint in any code which the child then executes, the child
2247 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2248 will cause it to terminate.
2250 However, if you want to debug the child process there is a workaround
2251 which isn't too painful. Put a call to @code{sleep} in the code which
2252 the child process executes after the fork. It may be useful to sleep
2253 only if a certain environment variable is set, or a certain file exists,
2254 so that the delay need not occur when you don't want to run @value{GDBN}
2255 on the child. While the child is sleeping, use the @code{ps} program to
2256 get its process ID. Then tell @value{GDBN} (a new invocation of
2257 @value{GDBN} if you are also debugging the parent process) to attach to
2258 the child process (@pxref{Attach}). From that point on you can debug
2259 the child process just like any other process which you attached to.
2261 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2262 debugging programs that create additional processes using the
2263 @code{fork} or @code{vfork} function.
2265 By default, when a program forks, @value{GDBN} will continue to debug
2266 the parent process and the child process will run unimpeded.
2268 If you want to follow the child process instead of the parent process,
2269 use the command @w{@code{set follow-fork-mode}}.
2272 @kindex set follow-fork-mode
2273 @item set follow-fork-mode @var{mode}
2274 Set the debugger response to a program call of @code{fork} or
2275 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2276 process. The @var{mode} can be:
2280 The original process is debugged after a fork. The child process runs
2281 unimpeded. This is the default.
2284 The new process is debugged after a fork. The parent process runs
2288 The debugger will ask for one of the above choices.
2291 @item show follow-fork-mode
2292 Display the current debugger response to a @code{fork} or @code{vfork} call.
2295 If you ask to debug a child process and a @code{vfork} is followed by an
2296 @code{exec}, @value{GDBN} executes the new target up to the first
2297 breakpoint in the new target. If you have a breakpoint set on
2298 @code{main} in your original program, the breakpoint will also be set on
2299 the child process's @code{main}.
2301 When a child process is spawned by @code{vfork}, you cannot debug the
2302 child or parent until an @code{exec} call completes.
2304 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2305 call executes, the new target restarts. To restart the parent process,
2306 use the @code{file} command with the parent executable name as its
2309 You can use the @code{catch} command to make @value{GDBN} stop whenever
2310 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2311 Catchpoints, ,Setting catchpoints}.
2314 @chapter Stopping and Continuing
2316 The principal purposes of using a debugger are so that you can stop your
2317 program before it terminates; or so that, if your program runs into
2318 trouble, you can investigate and find out why.
2320 Inside @value{GDBN}, your program may stop for any of several reasons,
2321 such as a signal, a breakpoint, or reaching a new line after a
2322 @value{GDBN} command such as @code{step}. You may then examine and
2323 change variables, set new breakpoints or remove old ones, and then
2324 continue execution. Usually, the messages shown by @value{GDBN} provide
2325 ample explanation of the status of your program---but you can also
2326 explicitly request this information at any time.
2329 @kindex info program
2331 Display information about the status of your program: whether it is
2332 running or not, what process it is, and why it stopped.
2336 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2337 * Continuing and Stepping:: Resuming execution
2339 * Thread Stops:: Stopping and starting multi-thread programs
2343 @section Breakpoints, watchpoints, and catchpoints
2346 A @dfn{breakpoint} makes your program stop whenever a certain point in
2347 the program is reached. For each breakpoint, you can add conditions to
2348 control in finer detail whether your program stops. You can set
2349 breakpoints with the @code{break} command and its variants (@pxref{Set
2350 Breaks, ,Setting breakpoints}), to specify the place where your program
2351 should stop by line number, function name or exact address in the
2354 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2355 breakpoints in shared libraries before the executable is run. There is
2356 a minor limitation on HP-UX systems: you must wait until the executable
2357 is run in order to set breakpoints in shared library routines that are
2358 not called directly by the program (for example, routines that are
2359 arguments in a @code{pthread_create} call).
2362 @cindex memory tracing
2363 @cindex breakpoint on memory address
2364 @cindex breakpoint on variable modification
2365 A @dfn{watchpoint} is a special breakpoint that stops your program
2366 when the value of an expression changes. You must use a different
2367 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2368 watchpoints}), but aside from that, you can manage a watchpoint like
2369 any other breakpoint: you enable, disable, and delete both breakpoints
2370 and watchpoints using the same commands.
2372 You can arrange to have values from your program displayed automatically
2373 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2377 @cindex breakpoint on events
2378 A @dfn{catchpoint} is another special breakpoint that stops your program
2379 when a certain kind of event occurs, such as the throwing of a C@t{++}
2380 exception or the loading of a library. As with watchpoints, you use a
2381 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2382 catchpoints}), but aside from that, you can manage a catchpoint like any
2383 other breakpoint. (To stop when your program receives a signal, use the
2384 @code{handle} command; see @ref{Signals, ,Signals}.)
2386 @cindex breakpoint numbers
2387 @cindex numbers for breakpoints
2388 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2389 catchpoint when you create it; these numbers are successive integers
2390 starting with one. In many of the commands for controlling various
2391 features of breakpoints you use the breakpoint number to say which
2392 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2393 @dfn{disabled}; if disabled, it has no effect on your program until you
2396 @cindex breakpoint ranges
2397 @cindex ranges of breakpoints
2398 Some @value{GDBN} commands accept a range of breakpoints on which to
2399 operate. A breakpoint range is either a single breakpoint number, like
2400 @samp{5}, or two such numbers, in increasing order, separated by a
2401 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2402 all breakpoint in that range are operated on.
2405 * Set Breaks:: Setting breakpoints
2406 * Set Watchpoints:: Setting watchpoints
2407 * Set Catchpoints:: Setting catchpoints
2408 * Delete Breaks:: Deleting breakpoints
2409 * Disabling:: Disabling breakpoints
2410 * Conditions:: Break conditions
2411 * Break Commands:: Breakpoint command lists
2412 * Breakpoint Menus:: Breakpoint menus
2413 * Error in Breakpoints:: ``Cannot insert breakpoints''
2417 @subsection Setting breakpoints
2419 @c FIXME LMB what does GDB do if no code on line of breakpt?
2420 @c consider in particular declaration with/without initialization.
2422 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2425 @kindex b @r{(@code{break})}
2426 @vindex $bpnum@r{, convenience variable}
2427 @cindex latest breakpoint
2428 Breakpoints are set with the @code{break} command (abbreviated
2429 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2430 number of the breakpoint you've set most recently; see @ref{Convenience
2431 Vars,, Convenience variables}, for a discussion of what you can do with
2432 convenience variables.
2434 You have several ways to say where the breakpoint should go.
2437 @item break @var{function}
2438 Set a breakpoint at entry to function @var{function}.
2439 When using source languages that permit overloading of symbols, such as
2440 C@t{++}, @var{function} may refer to more than one possible place to break.
2441 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2443 @item break +@var{offset}
2444 @itemx break -@var{offset}
2445 Set a breakpoint some number of lines forward or back from the position
2446 at which execution stopped in the currently selected @dfn{stack frame}.
2447 (@xref{Frames, ,Frames}, for a description of stack frames.)
2449 @item break @var{linenum}
2450 Set a breakpoint at line @var{linenum} in the current source file.
2451 The current source file is the last file whose source text was printed.
2452 The breakpoint will stop your program just before it executes any of the
2455 @item break @var{filename}:@var{linenum}
2456 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2458 @item break @var{filename}:@var{function}
2459 Set a breakpoint at entry to function @var{function} found in file
2460 @var{filename}. Specifying a file name as well as a function name is
2461 superfluous except when multiple files contain similarly named
2464 @item break *@var{address}
2465 Set a breakpoint at address @var{address}. You can use this to set
2466 breakpoints in parts of your program which do not have debugging
2467 information or source files.
2470 When called without any arguments, @code{break} sets a breakpoint at
2471 the next instruction to be executed in the selected stack frame
2472 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2473 innermost, this makes your program stop as soon as control
2474 returns to that frame. This is similar to the effect of a
2475 @code{finish} command in the frame inside the selected frame---except
2476 that @code{finish} does not leave an active breakpoint. If you use
2477 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2478 the next time it reaches the current location; this may be useful
2481 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2482 least one instruction has been executed. If it did not do this, you
2483 would be unable to proceed past a breakpoint without first disabling the
2484 breakpoint. This rule applies whether or not the breakpoint already
2485 existed when your program stopped.
2487 @item break @dots{} if @var{cond}
2488 Set a breakpoint with condition @var{cond}; evaluate the expression
2489 @var{cond} each time the breakpoint is reached, and stop only if the
2490 value is nonzero---that is, if @var{cond} evaluates as true.
2491 @samp{@dots{}} stands for one of the possible arguments described
2492 above (or no argument) specifying where to break. @xref{Conditions,
2493 ,Break conditions}, for more information on breakpoint conditions.
2496 @item tbreak @var{args}
2497 Set a breakpoint enabled only for one stop. @var{args} are the
2498 same as for the @code{break} command, and the breakpoint is set in the same
2499 way, but the breakpoint is automatically deleted after the first time your
2500 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2503 @item hbreak @var{args}
2504 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2505 @code{break} command and the breakpoint is set in the same way, but the
2506 breakpoint requires hardware support and some target hardware may not
2507 have this support. The main purpose of this is EPROM/ROM code
2508 debugging, so you can set a breakpoint at an instruction without
2509 changing the instruction. This can be used with the new trap-generation
2510 provided by SPARClite DSU and some x86-based targets. These targets
2511 will generate traps when a program accesses some data or instruction
2512 address that is assigned to the debug registers. However the hardware
2513 breakpoint registers can take a limited number of breakpoints. For
2514 example, on the DSU, only two data breakpoints can be set at a time, and
2515 @value{GDBN} will reject this command if more than two are used. Delete
2516 or disable unused hardware breakpoints before setting new ones
2517 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2520 @item thbreak @var{args}
2521 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2522 are the same as for the @code{hbreak} command and the breakpoint is set in
2523 the same way. However, like the @code{tbreak} command,
2524 the breakpoint is automatically deleted after the
2525 first time your program stops there. Also, like the @code{hbreak}
2526 command, the breakpoint requires hardware support and some target hardware
2527 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2528 See also @ref{Conditions, ,Break conditions}.
2531 @cindex regular expression
2532 @item rbreak @var{regex}
2533 Set breakpoints on all functions matching the regular expression
2534 @var{regex}. This command sets an unconditional breakpoint on all
2535 matches, printing a list of all breakpoints it set. Once these
2536 breakpoints are set, they are treated just like the breakpoints set with
2537 the @code{break} command. You can delete them, disable them, or make
2538 them conditional the same way as any other breakpoint.
2540 The syntax of the regular expression is the standard one used with tools
2541 like @file{grep}. Note that this is different from the syntax used by
2542 shells, so for instance @code{foo*} matches all functions that include
2543 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2544 @code{.*} leading and trailing the regular expression you supply, so to
2545 match only functions that begin with @code{foo}, use @code{^foo}.
2547 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2548 breakpoints on overloaded functions that are not members of any special
2551 @kindex info breakpoints
2552 @cindex @code{$_} and @code{info breakpoints}
2553 @item info breakpoints @r{[}@var{n}@r{]}
2554 @itemx info break @r{[}@var{n}@r{]}
2555 @itemx info watchpoints @r{[}@var{n}@r{]}
2556 Print a table of all breakpoints, watchpoints, and catchpoints set and
2557 not deleted, with the following columns for each breakpoint:
2560 @item Breakpoint Numbers
2562 Breakpoint, watchpoint, or catchpoint.
2564 Whether the breakpoint is marked to be disabled or deleted when hit.
2565 @item Enabled or Disabled
2566 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2567 that are not enabled.
2569 Where the breakpoint is in your program, as a memory address.
2571 Where the breakpoint is in the source for your program, as a file and
2576 If a breakpoint is conditional, @code{info break} shows the condition on
2577 the line following the affected breakpoint; breakpoint commands, if any,
2578 are listed after that.
2581 @code{info break} with a breakpoint
2582 number @var{n} as argument lists only that breakpoint. The
2583 convenience variable @code{$_} and the default examining-address for
2584 the @code{x} command are set to the address of the last breakpoint
2585 listed (@pxref{Memory, ,Examining memory}).
2588 @code{info break} displays a count of the number of times the breakpoint
2589 has been hit. This is especially useful in conjunction with the
2590 @code{ignore} command. You can ignore a large number of breakpoint
2591 hits, look at the breakpoint info to see how many times the breakpoint
2592 was hit, and then run again, ignoring one less than that number. This
2593 will get you quickly to the last hit of that breakpoint.
2596 @value{GDBN} allows you to set any number of breakpoints at the same place in
2597 your program. There is nothing silly or meaningless about this. When
2598 the breakpoints are conditional, this is even useful
2599 (@pxref{Conditions, ,Break conditions}).
2601 @cindex negative breakpoint numbers
2602 @cindex internal @value{GDBN} breakpoints
2603 @value{GDBN} itself sometimes sets breakpoints in your program for
2604 special purposes, such as proper handling of @code{longjmp} (in C
2605 programs). These internal breakpoints are assigned negative numbers,
2606 starting with @code{-1}; @samp{info breakpoints} does not display them.
2607 You can see these breakpoints with the @value{GDBN} maintenance command
2608 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2611 @node Set Watchpoints
2612 @subsection Setting watchpoints
2614 @cindex setting watchpoints
2615 @cindex software watchpoints
2616 @cindex hardware watchpoints
2617 You can use a watchpoint to stop execution whenever the value of an
2618 expression changes, without having to predict a particular place where
2621 Depending on your system, watchpoints may be implemented in software or
2622 hardware. @value{GDBN} does software watchpointing by single-stepping your
2623 program and testing the variable's value each time, which is hundreds of
2624 times slower than normal execution. (But this may still be worth it, to
2625 catch errors where you have no clue what part of your program is the
2628 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2629 @value{GDBN} includes support for
2630 hardware watchpoints, which do not slow down the running of your
2635 @item watch @var{expr}
2636 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2637 is written into by the program and its value changes.
2640 @item rwatch @var{expr}
2641 Set a watchpoint that will break when watch @var{expr} is read by the program.
2644 @item awatch @var{expr}
2645 Set a watchpoint that will break when @var{expr} is either read or written into
2648 @kindex info watchpoints
2649 @item info watchpoints
2650 This command prints a list of watchpoints, breakpoints, and catchpoints;
2651 it is the same as @code{info break}.
2654 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2655 watchpoints execute very quickly, and the debugger reports a change in
2656 value at the exact instruction where the change occurs. If @value{GDBN}
2657 cannot set a hardware watchpoint, it sets a software watchpoint, which
2658 executes more slowly and reports the change in value at the next
2659 statement, not the instruction, after the change occurs.
2661 When you issue the @code{watch} command, @value{GDBN} reports
2664 Hardware watchpoint @var{num}: @var{expr}
2668 if it was able to set a hardware watchpoint.
2670 Currently, the @code{awatch} and @code{rwatch} commands can only set
2671 hardware watchpoints, because accesses to data that don't change the
2672 value of the watched expression cannot be detected without examining
2673 every instruction as it is being executed, and @value{GDBN} does not do
2674 that currently. If @value{GDBN} finds that it is unable to set a
2675 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2676 will print a message like this:
2679 Expression cannot be implemented with read/access watchpoint.
2682 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2683 data type of the watched expression is wider than what a hardware
2684 watchpoint on the target machine can handle. For example, some systems
2685 can only watch regions that are up to 4 bytes wide; on such systems you
2686 cannot set hardware watchpoints for an expression that yields a
2687 double-precision floating-point number (which is typically 8 bytes
2688 wide). As a work-around, it might be possible to break the large region
2689 into a series of smaller ones and watch them with separate watchpoints.
2691 If you set too many hardware watchpoints, @value{GDBN} might be unable
2692 to insert all of them when you resume the execution of your program.
2693 Since the precise number of active watchpoints is unknown until such
2694 time as the program is about to be resumed, @value{GDBN} might not be
2695 able to warn you about this when you set the watchpoints, and the
2696 warning will be printed only when the program is resumed:
2699 Hardware watchpoint @var{num}: Could not insert watchpoint
2703 If this happens, delete or disable some of the watchpoints.
2705 The SPARClite DSU will generate traps when a program accesses some data
2706 or instruction address that is assigned to the debug registers. For the
2707 data addresses, DSU facilitates the @code{watch} command. However the
2708 hardware breakpoint registers can only take two data watchpoints, and
2709 both watchpoints must be the same kind. For example, you can set two
2710 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2711 @strong{or} two with @code{awatch} commands, but you cannot set one
2712 watchpoint with one command and the other with a different command.
2713 @value{GDBN} will reject the command if you try to mix watchpoints.
2714 Delete or disable unused watchpoint commands before setting new ones.
2716 If you call a function interactively using @code{print} or @code{call},
2717 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2718 kind of breakpoint or the call completes.
2720 @value{GDBN} automatically deletes watchpoints that watch local
2721 (automatic) variables, or expressions that involve such variables, when
2722 they go out of scope, that is, when the execution leaves the block in
2723 which these variables were defined. In particular, when the program
2724 being debugged terminates, @emph{all} local variables go out of scope,
2725 and so only watchpoints that watch global variables remain set. If you
2726 rerun the program, you will need to set all such watchpoints again. One
2727 way of doing that would be to set a code breakpoint at the entry to the
2728 @code{main} function and when it breaks, set all the watchpoints.
2731 @cindex watchpoints and threads
2732 @cindex threads and watchpoints
2733 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2734 usefulness. With the current watchpoint implementation, @value{GDBN}
2735 can only watch the value of an expression @emph{in a single thread}. If
2736 you are confident that the expression can only change due to the current
2737 thread's activity (and if you are also confident that no other thread
2738 can become current), then you can use watchpoints as usual. However,
2739 @value{GDBN} may not notice when a non-current thread's activity changes
2742 @c FIXME: this is almost identical to the previous paragraph.
2743 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2744 have only limited usefulness. If @value{GDBN} creates a software
2745 watchpoint, it can only watch the value of an expression @emph{in a
2746 single thread}. If you are confident that the expression can only
2747 change due to the current thread's activity (and if you are also
2748 confident that no other thread can become current), then you can use
2749 software watchpoints as usual. However, @value{GDBN} may not notice
2750 when a non-current thread's activity changes the expression. (Hardware
2751 watchpoints, in contrast, watch an expression in all threads.)
2754 @node Set Catchpoints
2755 @subsection Setting catchpoints
2756 @cindex catchpoints, setting
2757 @cindex exception handlers
2758 @cindex event handling
2760 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2761 kinds of program events, such as C@t{++} exceptions or the loading of a
2762 shared library. Use the @code{catch} command to set a catchpoint.
2766 @item catch @var{event}
2767 Stop when @var{event} occurs. @var{event} can be any of the following:
2771 The throwing of a C@t{++} exception.
2775 The catching of a C@t{++} exception.
2779 A call to @code{exec}. This is currently only available for HP-UX.
2783 A call to @code{fork}. This is currently only available for HP-UX.
2787 A call to @code{vfork}. This is currently only available for HP-UX.
2790 @itemx load @var{libname}
2792 The dynamic loading of any shared library, or the loading of the library
2793 @var{libname}. This is currently only available for HP-UX.
2796 @itemx unload @var{libname}
2797 @kindex catch unload
2798 The unloading of any dynamically loaded shared library, or the unloading
2799 of the library @var{libname}. This is currently only available for HP-UX.
2802 @item tcatch @var{event}
2803 Set a catchpoint that is enabled only for one stop. The catchpoint is
2804 automatically deleted after the first time the event is caught.
2808 Use the @code{info break} command to list the current catchpoints.
2810 There are currently some limitations to C@t{++} exception handling
2811 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2815 If you call a function interactively, @value{GDBN} normally returns
2816 control to you when the function has finished executing. If the call
2817 raises an exception, however, the call may bypass the mechanism that
2818 returns control to you and cause your program either to abort or to
2819 simply continue running until it hits a breakpoint, catches a signal
2820 that @value{GDBN} is listening for, or exits. This is the case even if
2821 you set a catchpoint for the exception; catchpoints on exceptions are
2822 disabled within interactive calls.
2825 You cannot raise an exception interactively.
2828 You cannot install an exception handler interactively.
2831 @cindex raise exceptions
2832 Sometimes @code{catch} is not the best way to debug exception handling:
2833 if you need to know exactly where an exception is raised, it is better to
2834 stop @emph{before} the exception handler is called, since that way you
2835 can see the stack before any unwinding takes place. If you set a
2836 breakpoint in an exception handler instead, it may not be easy to find
2837 out where the exception was raised.
2839 To stop just before an exception handler is called, you need some
2840 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2841 raised by calling a library function named @code{__raise_exception}
2842 which has the following ANSI C interface:
2845 /* @var{addr} is where the exception identifier is stored.
2846 @var{id} is the exception identifier. */
2847 void __raise_exception (void **addr, void *id);
2851 To make the debugger catch all exceptions before any stack
2852 unwinding takes place, set a breakpoint on @code{__raise_exception}
2853 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2855 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2856 that depends on the value of @var{id}, you can stop your program when
2857 a specific exception is raised. You can use multiple conditional
2858 breakpoints to stop your program when any of a number of exceptions are
2863 @subsection Deleting breakpoints
2865 @cindex clearing breakpoints, watchpoints, catchpoints
2866 @cindex deleting breakpoints, watchpoints, catchpoints
2867 It is often necessary to eliminate a breakpoint, watchpoint, or
2868 catchpoint once it has done its job and you no longer want your program
2869 to stop there. This is called @dfn{deleting} the breakpoint. A
2870 breakpoint that has been deleted no longer exists; it is forgotten.
2872 With the @code{clear} command you can delete breakpoints according to
2873 where they are in your program. With the @code{delete} command you can
2874 delete individual breakpoints, watchpoints, or catchpoints by specifying
2875 their breakpoint numbers.
2877 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2878 automatically ignores breakpoints on the first instruction to be executed
2879 when you continue execution without changing the execution address.
2884 Delete any breakpoints at the next instruction to be executed in the
2885 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2886 the innermost frame is selected, this is a good way to delete a
2887 breakpoint where your program just stopped.
2889 @item clear @var{function}
2890 @itemx clear @var{filename}:@var{function}
2891 Delete any breakpoints set at entry to the function @var{function}.
2893 @item clear @var{linenum}
2894 @itemx clear @var{filename}:@var{linenum}
2895 Delete any breakpoints set at or within the code of the specified line.
2897 @cindex delete breakpoints
2899 @kindex d @r{(@code{delete})}
2900 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2901 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2902 ranges specified as arguments. If no argument is specified, delete all
2903 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2904 confirm off}). You can abbreviate this command as @code{d}.
2908 @subsection Disabling breakpoints
2910 @kindex disable breakpoints
2911 @kindex enable breakpoints
2912 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2913 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2914 it had been deleted, but remembers the information on the breakpoint so
2915 that you can @dfn{enable} it again later.
2917 You disable and enable breakpoints, watchpoints, and catchpoints with
2918 the @code{enable} and @code{disable} commands, optionally specifying one
2919 or more breakpoint numbers as arguments. Use @code{info break} or
2920 @code{info watch} to print a list of breakpoints, watchpoints, and
2921 catchpoints if you do not know which numbers to use.
2923 A breakpoint, watchpoint, or catchpoint can have any of four different
2924 states of enablement:
2928 Enabled. The breakpoint stops your program. A breakpoint set
2929 with the @code{break} command starts out in this state.
2931 Disabled. The breakpoint has no effect on your program.
2933 Enabled once. The breakpoint stops your program, but then becomes
2936 Enabled for deletion. The breakpoint stops your program, but
2937 immediately after it does so it is deleted permanently. A breakpoint
2938 set with the @code{tbreak} command starts out in this state.
2941 You can use the following commands to enable or disable breakpoints,
2942 watchpoints, and catchpoints:
2945 @kindex disable breakpoints
2947 @kindex dis @r{(@code{disable})}
2948 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2949 Disable the specified breakpoints---or all breakpoints, if none are
2950 listed. A disabled breakpoint has no effect but is not forgotten. All
2951 options such as ignore-counts, conditions and commands are remembered in
2952 case the breakpoint is enabled again later. You may abbreviate
2953 @code{disable} as @code{dis}.
2955 @kindex enable breakpoints
2957 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2958 Enable the specified breakpoints (or all defined breakpoints). They
2959 become effective once again in stopping your program.
2961 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2962 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2963 of these breakpoints immediately after stopping your program.
2965 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2966 Enable the specified breakpoints to work once, then die. @value{GDBN}
2967 deletes any of these breakpoints as soon as your program stops there.
2970 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2971 @c confusing: tbreak is also initially enabled.
2972 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2973 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2974 subsequently, they become disabled or enabled only when you use one of
2975 the commands above. (The command @code{until} can set and delete a
2976 breakpoint of its own, but it does not change the state of your other
2977 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2981 @subsection Break conditions
2982 @cindex conditional breakpoints
2983 @cindex breakpoint conditions
2985 @c FIXME what is scope of break condition expr? Context where wanted?
2986 @c in particular for a watchpoint?
2987 The simplest sort of breakpoint breaks every time your program reaches a
2988 specified place. You can also specify a @dfn{condition} for a
2989 breakpoint. A condition is just a Boolean expression in your
2990 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2991 a condition evaluates the expression each time your program reaches it,
2992 and your program stops only if the condition is @emph{true}.
2994 This is the converse of using assertions for program validation; in that
2995 situation, you want to stop when the assertion is violated---that is,
2996 when the condition is false. In C, if you want to test an assertion expressed
2997 by the condition @var{assert}, you should set the condition
2998 @samp{! @var{assert}} on the appropriate breakpoint.
3000 Conditions are also accepted for watchpoints; you may not need them,
3001 since a watchpoint is inspecting the value of an expression anyhow---but
3002 it might be simpler, say, to just set a watchpoint on a variable name,
3003 and specify a condition that tests whether the new value is an interesting
3006 Break conditions can have side effects, and may even call functions in
3007 your program. This can be useful, for example, to activate functions
3008 that log program progress, or to use your own print functions to
3009 format special data structures. The effects are completely predictable
3010 unless there is another enabled breakpoint at the same address. (In
3011 that case, @value{GDBN} might see the other breakpoint first and stop your
3012 program without checking the condition of this one.) Note that
3013 breakpoint commands are usually more convenient and flexible than break
3015 purpose of performing side effects when a breakpoint is reached
3016 (@pxref{Break Commands, ,Breakpoint command lists}).
3018 Break conditions can be specified when a breakpoint is set, by using
3019 @samp{if} in the arguments to the @code{break} command. @xref{Set
3020 Breaks, ,Setting breakpoints}. They can also be changed at any time
3021 with the @code{condition} command.
3023 You can also use the @code{if} keyword with the @code{watch} command.
3024 The @code{catch} command does not recognize the @code{if} keyword;
3025 @code{condition} is the only way to impose a further condition on a
3030 @item condition @var{bnum} @var{expression}
3031 Specify @var{expression} as the break condition for breakpoint,
3032 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3033 breakpoint @var{bnum} stops your program only if the value of
3034 @var{expression} is true (nonzero, in C). When you use
3035 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3036 syntactic correctness, and to determine whether symbols in it have
3037 referents in the context of your breakpoint. If @var{expression} uses
3038 symbols not referenced in the context of the breakpoint, @value{GDBN}
3039 prints an error message:
3042 No symbol "foo" in current context.
3047 not actually evaluate @var{expression} at the time the @code{condition}
3048 command (or a command that sets a breakpoint with a condition, like
3049 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3051 @item condition @var{bnum}
3052 Remove the condition from breakpoint number @var{bnum}. It becomes
3053 an ordinary unconditional breakpoint.
3056 @cindex ignore count (of breakpoint)
3057 A special case of a breakpoint condition is to stop only when the
3058 breakpoint has been reached a certain number of times. This is so
3059 useful that there is a special way to do it, using the @dfn{ignore
3060 count} of the breakpoint. Every breakpoint has an ignore count, which
3061 is an integer. Most of the time, the ignore count is zero, and
3062 therefore has no effect. But if your program reaches a breakpoint whose
3063 ignore count is positive, then instead of stopping, it just decrements
3064 the ignore count by one and continues. As a result, if the ignore count
3065 value is @var{n}, the breakpoint does not stop the next @var{n} times
3066 your program reaches it.
3070 @item ignore @var{bnum} @var{count}
3071 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3072 The next @var{count} times the breakpoint is reached, your program's
3073 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3076 To make the breakpoint stop the next time it is reached, specify
3079 When you use @code{continue} to resume execution of your program from a
3080 breakpoint, you can specify an ignore count directly as an argument to
3081 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3082 Stepping,,Continuing and stepping}.
3084 If a breakpoint has a positive ignore count and a condition, the
3085 condition is not checked. Once the ignore count reaches zero,
3086 @value{GDBN} resumes checking the condition.
3088 You could achieve the effect of the ignore count with a condition such
3089 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3090 is decremented each time. @xref{Convenience Vars, ,Convenience
3094 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3097 @node Break Commands
3098 @subsection Breakpoint command lists
3100 @cindex breakpoint commands
3101 You can give any breakpoint (or watchpoint or catchpoint) a series of
3102 commands to execute when your program stops due to that breakpoint. For
3103 example, you might want to print the values of certain expressions, or
3104 enable other breakpoints.
3109 @item commands @r{[}@var{bnum}@r{]}
3110 @itemx @dots{} @var{command-list} @dots{}
3112 Specify a list of commands for breakpoint number @var{bnum}. The commands
3113 themselves appear on the following lines. Type a line containing just
3114 @code{end} to terminate the commands.
3116 To remove all commands from a breakpoint, type @code{commands} and
3117 follow it immediately with @code{end}; that is, give no commands.
3119 With no @var{bnum} argument, @code{commands} refers to the last
3120 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3121 recently encountered).
3124 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3125 disabled within a @var{command-list}.
3127 You can use breakpoint commands to start your program up again. Simply
3128 use the @code{continue} command, or @code{step}, or any other command
3129 that resumes execution.
3131 Any other commands in the command list, after a command that resumes
3132 execution, are ignored. This is because any time you resume execution
3133 (even with a simple @code{next} or @code{step}), you may encounter
3134 another breakpoint---which could have its own command list, leading to
3135 ambiguities about which list to execute.
3138 If the first command you specify in a command list is @code{silent}, the
3139 usual message about stopping at a breakpoint is not printed. This may
3140 be desirable for breakpoints that are to print a specific message and
3141 then continue. If none of the remaining commands print anything, you
3142 see no sign that the breakpoint was reached. @code{silent} is
3143 meaningful only at the beginning of a breakpoint command list.
3145 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3146 print precisely controlled output, and are often useful in silent
3147 breakpoints. @xref{Output, ,Commands for controlled output}.
3149 For example, here is how you could use breakpoint commands to print the
3150 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3156 printf "x is %d\n",x
3161 One application for breakpoint commands is to compensate for one bug so
3162 you can test for another. Put a breakpoint just after the erroneous line
3163 of code, give it a condition to detect the case in which something
3164 erroneous has been done, and give it commands to assign correct values
3165 to any variables that need them. End with the @code{continue} command
3166 so that your program does not stop, and start with the @code{silent}
3167 command so that no output is produced. Here is an example:
3178 @node Breakpoint Menus
3179 @subsection Breakpoint menus
3181 @cindex symbol overloading
3183 Some programming languages (notably C@t{++}) permit a single function name
3184 to be defined several times, for application in different contexts.
3185 This is called @dfn{overloading}. When a function name is overloaded,
3186 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3187 a breakpoint. If you realize this is a problem, you can use
3188 something like @samp{break @var{function}(@var{types})} to specify which
3189 particular version of the function you want. Otherwise, @value{GDBN} offers
3190 you a menu of numbered choices for different possible breakpoints, and
3191 waits for your selection with the prompt @samp{>}. The first two
3192 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3193 sets a breakpoint at each definition of @var{function}, and typing
3194 @kbd{0} aborts the @code{break} command without setting any new
3197 For example, the following session excerpt shows an attempt to set a
3198 breakpoint at the overloaded symbol @code{String::after}.
3199 We choose three particular definitions of that function name:
3201 @c FIXME! This is likely to change to show arg type lists, at least
3204 (@value{GDBP}) b String::after
3207 [2] file:String.cc; line number:867
3208 [3] file:String.cc; line number:860
3209 [4] file:String.cc; line number:875
3210 [5] file:String.cc; line number:853
3211 [6] file:String.cc; line number:846
3212 [7] file:String.cc; line number:735
3214 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3215 Breakpoint 2 at 0xb344: file String.cc, line 875.
3216 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3217 Multiple breakpoints were set.
3218 Use the "delete" command to delete unwanted
3224 @c @ifclear BARETARGET
3225 @node Error in Breakpoints
3226 @subsection ``Cannot insert breakpoints''
3228 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3230 Under some operating systems, breakpoints cannot be used in a program if
3231 any other process is running that program. In this situation,
3232 attempting to run or continue a program with a breakpoint causes
3233 @value{GDBN} to print an error message:
3236 Cannot insert breakpoints.
3237 The same program may be running in another process.
3240 When this happens, you have three ways to proceed:
3244 Remove or disable the breakpoints, then continue.
3247 Suspend @value{GDBN}, and copy the file containing your program to a new
3248 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3249 that @value{GDBN} should run your program under that name.
3250 Then start your program again.
3253 Relink your program so that the text segment is nonsharable, using the
3254 linker option @samp{-N}. The operating system limitation may not apply
3255 to nonsharable executables.
3259 A similar message can be printed if you request too many active
3260 hardware-assisted breakpoints and watchpoints:
3262 @c FIXME: the precise wording of this message may change; the relevant
3263 @c source change is not committed yet (Sep 3, 1999).
3265 Stopped; cannot insert breakpoints.
3266 You may have requested too many hardware breakpoints and watchpoints.
3270 This message is printed when you attempt to resume the program, since
3271 only then @value{GDBN} knows exactly how many hardware breakpoints and
3272 watchpoints it needs to insert.
3274 When this message is printed, you need to disable or remove some of the
3275 hardware-assisted breakpoints and watchpoints, and then continue.
3278 @node Continuing and Stepping
3279 @section Continuing and stepping
3283 @cindex resuming execution
3284 @dfn{Continuing} means resuming program execution until your program
3285 completes normally. In contrast, @dfn{stepping} means executing just
3286 one more ``step'' of your program, where ``step'' may mean either one
3287 line of source code, or one machine instruction (depending on what
3288 particular command you use). Either when continuing or when stepping,
3289 your program may stop even sooner, due to a breakpoint or a signal. (If
3290 it stops due to a signal, you may want to use @code{handle}, or use
3291 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3295 @kindex c @r{(@code{continue})}
3296 @kindex fg @r{(resume foreground execution)}
3297 @item continue @r{[}@var{ignore-count}@r{]}
3298 @itemx c @r{[}@var{ignore-count}@r{]}
3299 @itemx fg @r{[}@var{ignore-count}@r{]}
3300 Resume program execution, at the address where your program last stopped;
3301 any breakpoints set at that address are bypassed. The optional argument
3302 @var{ignore-count} allows you to specify a further number of times to
3303 ignore a breakpoint at this location; its effect is like that of
3304 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3306 The argument @var{ignore-count} is meaningful only when your program
3307 stopped due to a breakpoint. At other times, the argument to
3308 @code{continue} is ignored.
3310 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3311 debugged program is deemed to be the foreground program) are provided
3312 purely for convenience, and have exactly the same behavior as
3316 To resume execution at a different place, you can use @code{return}
3317 (@pxref{Returning, ,Returning from a function}) to go back to the
3318 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3319 different address}) to go to an arbitrary location in your program.
3321 A typical technique for using stepping is to set a breakpoint
3322 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3323 beginning of the function or the section of your program where a problem
3324 is believed to lie, run your program until it stops at that breakpoint,
3325 and then step through the suspect area, examining the variables that are
3326 interesting, until you see the problem happen.
3330 @kindex s @r{(@code{step})}
3332 Continue running your program until control reaches a different source
3333 line, then stop it and return control to @value{GDBN}. This command is
3334 abbreviated @code{s}.
3337 @c "without debugging information" is imprecise; actually "without line
3338 @c numbers in the debugging information". (gcc -g1 has debugging info but
3339 @c not line numbers). But it seems complex to try to make that
3340 @c distinction here.
3341 @emph{Warning:} If you use the @code{step} command while control is
3342 within a function that was compiled without debugging information,
3343 execution proceeds until control reaches a function that does have
3344 debugging information. Likewise, it will not step into a function which
3345 is compiled without debugging information. To step through functions
3346 without debugging information, use the @code{stepi} command, described
3350 The @code{step} command only stops at the first instruction of a source
3351 line. This prevents the multiple stops that could otherwise occur in
3352 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3353 to stop if a function that has debugging information is called within
3354 the line. In other words, @code{step} @emph{steps inside} any functions
3355 called within the line.
3357 Also, the @code{step} command only enters a function if there is line
3358 number information for the function. Otherwise it acts like the
3359 @code{next} command. This avoids problems when using @code{cc -gl}
3360 on MIPS machines. Previously, @code{step} entered subroutines if there
3361 was any debugging information about the routine.
3363 @item step @var{count}
3364 Continue running as in @code{step}, but do so @var{count} times. If a
3365 breakpoint is reached, or a signal not related to stepping occurs before
3366 @var{count} steps, stepping stops right away.
3369 @kindex n @r{(@code{next})}
3370 @item next @r{[}@var{count}@r{]}
3371 Continue to the next source line in the current (innermost) stack frame.
3372 This is similar to @code{step}, but function calls that appear within
3373 the line of code are executed without stopping. Execution stops when
3374 control reaches a different line of code at the original stack level
3375 that was executing when you gave the @code{next} command. This command
3376 is abbreviated @code{n}.
3378 An argument @var{count} is a repeat count, as for @code{step}.
3381 @c FIX ME!! Do we delete this, or is there a way it fits in with
3382 @c the following paragraph? --- Vctoria
3384 @c @code{next} within a function that lacks debugging information acts like
3385 @c @code{step}, but any function calls appearing within the code of the
3386 @c function are executed without stopping.
3388 The @code{next} command only stops at the first instruction of a
3389 source line. This prevents multiple stops that could otherwise occur in
3390 @code{switch} statements, @code{for} loops, etc.
3392 @kindex set step-mode
3394 @cindex functions without line info, and stepping
3395 @cindex stepping into functions with no line info
3396 @itemx set step-mode on
3397 The @code{set step-mode on} command causes the @code{step} command to
3398 stop at the first instruction of a function which contains no debug line
3399 information rather than stepping over it.
3401 This is useful in cases where you may be interested in inspecting the
3402 machine instructions of a function which has no symbolic info and do not
3403 want @value{GDBN} to automatically skip over this function.
3405 @item set step-mode off
3406 Causes the @code{step} command to step over any functions which contains no
3407 debug information. This is the default.
3411 Continue running until just after function in the selected stack frame
3412 returns. Print the returned value (if any).
3414 Contrast this with the @code{return} command (@pxref{Returning,
3415 ,Returning from a function}).
3418 @kindex u @r{(@code{until})}
3421 Continue running until a source line past the current line, in the
3422 current stack frame, is reached. This command is used to avoid single
3423 stepping through a loop more than once. It is like the @code{next}
3424 command, except that when @code{until} encounters a jump, it
3425 automatically continues execution until the program counter is greater
3426 than the address of the jump.
3428 This means that when you reach the end of a loop after single stepping
3429 though it, @code{until} makes your program continue execution until it
3430 exits the loop. In contrast, a @code{next} command at the end of a loop
3431 simply steps back to the beginning of the loop, which forces you to step
3432 through the next iteration.
3434 @code{until} always stops your program if it attempts to exit the current
3437 @code{until} may produce somewhat counterintuitive results if the order
3438 of machine code does not match the order of the source lines. For
3439 example, in the following excerpt from a debugging session, the @code{f}
3440 (@code{frame}) command shows that execution is stopped at line
3441 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3445 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3447 (@value{GDBP}) until
3448 195 for ( ; argc > 0; NEXTARG) @{
3451 This happened because, for execution efficiency, the compiler had
3452 generated code for the loop closure test at the end, rather than the
3453 start, of the loop---even though the test in a C @code{for}-loop is
3454 written before the body of the loop. The @code{until} command appeared
3455 to step back to the beginning of the loop when it advanced to this
3456 expression; however, it has not really gone to an earlier
3457 statement---not in terms of the actual machine code.
3459 @code{until} with no argument works by means of single
3460 instruction stepping, and hence is slower than @code{until} with an
3463 @item until @var{location}
3464 @itemx u @var{location}
3465 Continue running your program until either the specified location is
3466 reached, or the current stack frame returns. @var{location} is any of
3467 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3468 ,Setting breakpoints}). This form of the command uses breakpoints,
3469 and hence is quicker than @code{until} without an argument.
3472 @kindex si @r{(@code{stepi})}
3474 @itemx stepi @var{arg}
3476 Execute one machine instruction, then stop and return to the debugger.
3478 It is often useful to do @samp{display/i $pc} when stepping by machine
3479 instructions. This makes @value{GDBN} automatically display the next
3480 instruction to be executed, each time your program stops. @xref{Auto
3481 Display,, Automatic display}.
3483 An argument is a repeat count, as in @code{step}.
3487 @kindex ni @r{(@code{nexti})}
3489 @itemx nexti @var{arg}
3491 Execute one machine instruction, but if it is a function call,
3492 proceed until the function returns.
3494 An argument is a repeat count, as in @code{next}.
3501 A signal is an asynchronous event that can happen in a program. The
3502 operating system defines the possible kinds of signals, and gives each
3503 kind a name and a number. For example, in Unix @code{SIGINT} is the
3504 signal a program gets when you type an interrupt character (often @kbd{C-c});
3505 @code{SIGSEGV} is the signal a program gets from referencing a place in
3506 memory far away from all the areas in use; @code{SIGALRM} occurs when
3507 the alarm clock timer goes off (which happens only if your program has
3508 requested an alarm).
3510 @cindex fatal signals
3511 Some signals, including @code{SIGALRM}, are a normal part of the
3512 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3513 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3514 program has not specified in advance some other way to handle the signal.
3515 @code{SIGINT} does not indicate an error in your program, but it is normally
3516 fatal so it can carry out the purpose of the interrupt: to kill the program.
3518 @value{GDBN} has the ability to detect any occurrence of a signal in your
3519 program. You can tell @value{GDBN} in advance what to do for each kind of
3522 @cindex handling signals
3523 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3524 @code{SIGALRM} be silently passed to your program
3525 (so as not to interfere with their role in the program's functioning)
3526 but to stop your program immediately whenever an error signal happens.
3527 You can change these settings with the @code{handle} command.
3530 @kindex info signals
3533 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3534 handle each one. You can use this to see the signal numbers of all
3535 the defined types of signals.
3537 @code{info handle} is an alias for @code{info signals}.
3540 @item handle @var{signal} @var{keywords}@dots{}
3541 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3542 can be the number of a signal or its name (with or without the
3543 @samp{SIG} at the beginning); a list of signal numbers of the form
3544 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3545 known signals. The @var{keywords} say what change to make.
3549 The keywords allowed by the @code{handle} command can be abbreviated.
3550 Their full names are:
3554 @value{GDBN} should not stop your program when this signal happens. It may
3555 still print a message telling you that the signal has come in.
3558 @value{GDBN} should stop your program when this signal happens. This implies
3559 the @code{print} keyword as well.
3562 @value{GDBN} should print a message when this signal happens.
3565 @value{GDBN} should not mention the occurrence of the signal at all. This
3566 implies the @code{nostop} keyword as well.
3570 @value{GDBN} should allow your program to see this signal; your program
3571 can handle the signal, or else it may terminate if the signal is fatal
3572 and not handled. @code{pass} and @code{noignore} are synonyms.
3576 @value{GDBN} should not allow your program to see this signal.
3577 @code{nopass} and @code{ignore} are synonyms.
3581 When a signal stops your program, the signal is not visible to the
3583 continue. Your program sees the signal then, if @code{pass} is in
3584 effect for the signal in question @emph{at that time}. In other words,
3585 after @value{GDBN} reports a signal, you can use the @code{handle}
3586 command with @code{pass} or @code{nopass} to control whether your
3587 program sees that signal when you continue.
3589 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3590 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3591 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3594 You can also use the @code{signal} command to prevent your program from
3595 seeing a signal, or cause it to see a signal it normally would not see,
3596 or to give it any signal at any time. For example, if your program stopped
3597 due to some sort of memory reference error, you might store correct
3598 values into the erroneous variables and continue, hoping to see more
3599 execution; but your program would probably terminate immediately as
3600 a result of the fatal signal once it saw the signal. To prevent this,
3601 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3605 @section Stopping and starting multi-thread programs
3607 When your program has multiple threads (@pxref{Threads,, Debugging
3608 programs with multiple threads}), you can choose whether to set
3609 breakpoints on all threads, or on a particular thread.
3612 @cindex breakpoints and threads
3613 @cindex thread breakpoints
3614 @kindex break @dots{} thread @var{threadno}
3615 @item break @var{linespec} thread @var{threadno}
3616 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3617 @var{linespec} specifies source lines; there are several ways of
3618 writing them, but the effect is always to specify some source line.
3620 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3621 to specify that you only want @value{GDBN} to stop the program when a
3622 particular thread reaches this breakpoint. @var{threadno} is one of the
3623 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3624 column of the @samp{info threads} display.
3626 If you do not specify @samp{thread @var{threadno}} when you set a
3627 breakpoint, the breakpoint applies to @emph{all} threads of your
3630 You can use the @code{thread} qualifier on conditional breakpoints as
3631 well; in this case, place @samp{thread @var{threadno}} before the
3632 breakpoint condition, like this:
3635 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3640 @cindex stopped threads
3641 @cindex threads, stopped
3642 Whenever your program stops under @value{GDBN} for any reason,
3643 @emph{all} threads of execution stop, not just the current thread. This
3644 allows you to examine the overall state of the program, including
3645 switching between threads, without worrying that things may change
3648 @cindex continuing threads
3649 @cindex threads, continuing
3650 Conversely, whenever you restart the program, @emph{all} threads start
3651 executing. @emph{This is true even when single-stepping} with commands
3652 like @code{step} or @code{next}.
3654 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3655 Since thread scheduling is up to your debugging target's operating
3656 system (not controlled by @value{GDBN}), other threads may
3657 execute more than one statement while the current thread completes a
3658 single step. Moreover, in general other threads stop in the middle of a
3659 statement, rather than at a clean statement boundary, when the program
3662 You might even find your program stopped in another thread after
3663 continuing or even single-stepping. This happens whenever some other
3664 thread runs into a breakpoint, a signal, or an exception before the
3665 first thread completes whatever you requested.
3667 On some OSes, you can lock the OS scheduler and thus allow only a single
3671 @item set scheduler-locking @var{mode}
3672 Set the scheduler locking mode. If it is @code{off}, then there is no
3673 locking and any thread may run at any time. If @code{on}, then only the
3674 current thread may run when the inferior is resumed. The @code{step}
3675 mode optimizes for single-stepping. It stops other threads from
3676 ``seizing the prompt'' by preempting the current thread while you are
3677 stepping. Other threads will only rarely (or never) get a chance to run
3678 when you step. They are more likely to run when you @samp{next} over a
3679 function call, and they are completely free to run when you use commands
3680 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3681 thread hits a breakpoint during its timeslice, they will never steal the
3682 @value{GDBN} prompt away from the thread that you are debugging.
3684 @item show scheduler-locking
3685 Display the current scheduler locking mode.
3690 @chapter Examining the Stack
3692 When your program has stopped, the first thing you need to know is where it
3693 stopped and how it got there.
3696 Each time your program performs a function call, information about the call
3698 That information includes the location of the call in your program,
3699 the arguments of the call,
3700 and the local variables of the function being called.
3701 The information is saved in a block of data called a @dfn{stack frame}.
3702 The stack frames are allocated in a region of memory called the @dfn{call
3705 When your program stops, the @value{GDBN} commands for examining the
3706 stack allow you to see all of this information.
3708 @cindex selected frame
3709 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3710 @value{GDBN} commands refer implicitly to the selected frame. In
3711 particular, whenever you ask @value{GDBN} for the value of a variable in
3712 your program, the value is found in the selected frame. There are
3713 special @value{GDBN} commands to select whichever frame you are
3714 interested in. @xref{Selection, ,Selecting a frame}.
3716 When your program stops, @value{GDBN} automatically selects the
3717 currently executing frame and describes it briefly, similar to the
3718 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3721 * Frames:: Stack frames
3722 * Backtrace:: Backtraces
3723 * Selection:: Selecting a frame
3724 * Frame Info:: Information on a frame
3729 @section Stack frames
3731 @cindex frame, definition
3733 The call stack is divided up into contiguous pieces called @dfn{stack
3734 frames}, or @dfn{frames} for short; each frame is the data associated
3735 with one call to one function. The frame contains the arguments given
3736 to the function, the function's local variables, and the address at
3737 which the function is executing.
3739 @cindex initial frame
3740 @cindex outermost frame
3741 @cindex innermost frame
3742 When your program is started, the stack has only one frame, that of the
3743 function @code{main}. This is called the @dfn{initial} frame or the
3744 @dfn{outermost} frame. Each time a function is called, a new frame is
3745 made. Each time a function returns, the frame for that function invocation
3746 is eliminated. If a function is recursive, there can be many frames for
3747 the same function. The frame for the function in which execution is
3748 actually occurring is called the @dfn{innermost} frame. This is the most
3749 recently created of all the stack frames that still exist.
3751 @cindex frame pointer
3752 Inside your program, stack frames are identified by their addresses. A
3753 stack frame consists of many bytes, each of which has its own address; each
3754 kind of computer has a convention for choosing one byte whose
3755 address serves as the address of the frame. Usually this address is kept
3756 in a register called the @dfn{frame pointer register} while execution is
3757 going on in that frame.
3759 @cindex frame number
3760 @value{GDBN} assigns numbers to all existing stack frames, starting with
3761 zero for the innermost frame, one for the frame that called it,
3762 and so on upward. These numbers do not really exist in your program;
3763 they are assigned by @value{GDBN} to give you a way of designating stack
3764 frames in @value{GDBN} commands.
3766 @c The -fomit-frame-pointer below perennially causes hbox overflow
3767 @c underflow problems.
3768 @cindex frameless execution
3769 Some compilers provide a way to compile functions so that they operate
3770 without stack frames. (For example, the @value{GCC} option
3772 @samp{-fomit-frame-pointer}
3774 generates functions without a frame.)
3775 This is occasionally done with heavily used library functions to save
3776 the frame setup time. @value{GDBN} has limited facilities for dealing
3777 with these function invocations. If the innermost function invocation
3778 has no stack frame, @value{GDBN} nevertheless regards it as though
3779 it had a separate frame, which is numbered zero as usual, allowing
3780 correct tracing of the function call chain. However, @value{GDBN} has
3781 no provision for frameless functions elsewhere in the stack.
3784 @kindex frame@r{, command}
3785 @cindex current stack frame
3786 @item frame @var{args}
3787 The @code{frame} command allows you to move from one stack frame to another,
3788 and to print the stack frame you select. @var{args} may be either the
3789 address of the frame or the stack frame number. Without an argument,
3790 @code{frame} prints the current stack frame.
3792 @kindex select-frame
3793 @cindex selecting frame silently
3795 The @code{select-frame} command allows you to move from one stack frame
3796 to another without printing the frame. This is the silent version of
3805 @cindex stack traces
3806 A backtrace is a summary of how your program got where it is. It shows one
3807 line per frame, for many frames, starting with the currently executing
3808 frame (frame zero), followed by its caller (frame one), and on up the
3813 @kindex bt @r{(@code{backtrace})}
3816 Print a backtrace of the entire stack: one line per frame for all
3817 frames in the stack.
3819 You can stop the backtrace at any time by typing the system interrupt
3820 character, normally @kbd{C-c}.
3822 @item backtrace @var{n}
3824 Similar, but print only the innermost @var{n} frames.
3826 @item backtrace -@var{n}
3828 Similar, but print only the outermost @var{n} frames.
3833 @kindex info s @r{(@code{info stack})}
3834 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3835 are additional aliases for @code{backtrace}.
3837 Each line in the backtrace shows the frame number and the function name.
3838 The program counter value is also shown---unless you use @code{set
3839 print address off}. The backtrace also shows the source file name and
3840 line number, as well as the arguments to the function. The program
3841 counter value is omitted if it is at the beginning of the code for that
3844 Here is an example of a backtrace. It was made with the command
3845 @samp{bt 3}, so it shows the innermost three frames.
3849 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3851 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3852 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3854 (More stack frames follow...)
3859 The display for frame zero does not begin with a program counter
3860 value, indicating that your program has stopped at the beginning of the
3861 code for line @code{993} of @code{builtin.c}.
3864 @section Selecting a frame
3866 Most commands for examining the stack and other data in your program work on
3867 whichever stack frame is selected at the moment. Here are the commands for
3868 selecting a stack frame; all of them finish by printing a brief description
3869 of the stack frame just selected.
3872 @kindex frame@r{, selecting}
3873 @kindex f @r{(@code{frame})}
3876 Select frame number @var{n}. Recall that frame zero is the innermost
3877 (currently executing) frame, frame one is the frame that called the
3878 innermost one, and so on. The highest-numbered frame is the one for
3881 @item frame @var{addr}
3883 Select the frame at address @var{addr}. This is useful mainly if the
3884 chaining of stack frames has been damaged by a bug, making it
3885 impossible for @value{GDBN} to assign numbers properly to all frames. In
3886 addition, this can be useful when your program has multiple stacks and
3887 switches between them.
3889 On the SPARC architecture, @code{frame} needs two addresses to
3890 select an arbitrary frame: a frame pointer and a stack pointer.
3892 On the MIPS and Alpha architecture, it needs two addresses: a stack
3893 pointer and a program counter.
3895 On the 29k architecture, it needs three addresses: a register stack
3896 pointer, a program counter, and a memory stack pointer.
3897 @c note to future updaters: this is conditioned on a flag
3898 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3899 @c as of 27 Jan 1994.
3903 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3904 advances toward the outermost frame, to higher frame numbers, to frames
3905 that have existed longer. @var{n} defaults to one.
3908 @kindex do @r{(@code{down})}
3910 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3911 advances toward the innermost frame, to lower frame numbers, to frames
3912 that were created more recently. @var{n} defaults to one. You may
3913 abbreviate @code{down} as @code{do}.
3916 All of these commands end by printing two lines of output describing the
3917 frame. The first line shows the frame number, the function name, the
3918 arguments, and the source file and line number of execution in that
3919 frame. The second line shows the text of that source line.
3927 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3929 10 read_input_file (argv[i]);
3933 After such a printout, the @code{list} command with no arguments
3934 prints ten lines centered on the point of execution in the frame.
3935 You can also edit the program at the point of execution with your favorite
3936 editing program by typing @code{edit}.
3937 @xref{List, ,Printing source lines},
3941 @kindex down-silently
3943 @item up-silently @var{n}
3944 @itemx down-silently @var{n}
3945 These two commands are variants of @code{up} and @code{down},
3946 respectively; they differ in that they do their work silently, without
3947 causing display of the new frame. They are intended primarily for use
3948 in @value{GDBN} command scripts, where the output might be unnecessary and
3953 @section Information about a frame
3955 There are several other commands to print information about the selected
3961 When used without any argument, this command does not change which
3962 frame is selected, but prints a brief description of the currently
3963 selected stack frame. It can be abbreviated @code{f}. With an
3964 argument, this command is used to select a stack frame.
3965 @xref{Selection, ,Selecting a frame}.
3968 @kindex info f @r{(@code{info frame})}
3971 This command prints a verbose description of the selected stack frame,
3976 the address of the frame
3978 the address of the next frame down (called by this frame)
3980 the address of the next frame up (caller of this frame)
3982 the language in which the source code corresponding to this frame is written
3984 the address of the frame's arguments
3986 the address of the frame's local variables
3988 the program counter saved in it (the address of execution in the caller frame)
3990 which registers were saved in the frame
3993 @noindent The verbose description is useful when
3994 something has gone wrong that has made the stack format fail to fit
3995 the usual conventions.
3997 @item info frame @var{addr}
3998 @itemx info f @var{addr}
3999 Print a verbose description of the frame at address @var{addr}, without
4000 selecting that frame. The selected frame remains unchanged by this
4001 command. This requires the same kind of address (more than one for some
4002 architectures) that you specify in the @code{frame} command.
4003 @xref{Selection, ,Selecting a frame}.
4007 Print the arguments of the selected frame, each on a separate line.
4011 Print the local variables of the selected frame, each on a separate
4012 line. These are all variables (declared either static or automatic)
4013 accessible at the point of execution of the selected frame.
4016 @cindex catch exceptions, list active handlers
4017 @cindex exception handlers, how to list
4019 Print a list of all the exception handlers that are active in the
4020 current stack frame at the current point of execution. To see other
4021 exception handlers, visit the associated frame (using the @code{up},
4022 @code{down}, or @code{frame} commands); then type @code{info catch}.
4023 @xref{Set Catchpoints, , Setting catchpoints}.
4029 @chapter Examining Source Files
4031 @value{GDBN} can print parts of your program's source, since the debugging
4032 information recorded in the program tells @value{GDBN} what source files were
4033 used to build it. When your program stops, @value{GDBN} spontaneously prints
4034 the line where it stopped. Likewise, when you select a stack frame
4035 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4036 execution in that frame has stopped. You can print other portions of
4037 source files by explicit command.
4039 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4040 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4041 @value{GDBN} under @sc{gnu} Emacs}.
4044 * List:: Printing source lines
4045 * Edit:: Editing source files
4046 * Search:: Searching source files
4047 * Source Path:: Specifying source directories
4048 * Machine Code:: Source and machine code
4052 @section Printing source lines
4055 @kindex l @r{(@code{list})}
4056 To print lines from a source file, use the @code{list} command
4057 (abbreviated @code{l}). By default, ten lines are printed.
4058 There are several ways to specify what part of the file you want to print.
4060 Here are the forms of the @code{list} command most commonly used:
4063 @item list @var{linenum}
4064 Print lines centered around line number @var{linenum} in the
4065 current source file.
4067 @item list @var{function}
4068 Print lines centered around the beginning of function
4072 Print more lines. If the last lines printed were printed with a
4073 @code{list} command, this prints lines following the last lines
4074 printed; however, if the last line printed was a solitary line printed
4075 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4076 Stack}), this prints lines centered around that line.
4079 Print lines just before the lines last printed.
4082 By default, @value{GDBN} prints ten source lines with any of these forms of
4083 the @code{list} command. You can change this using @code{set listsize}:
4086 @kindex set listsize
4087 @item set listsize @var{count}
4088 Make the @code{list} command display @var{count} source lines (unless
4089 the @code{list} argument explicitly specifies some other number).
4091 @kindex show listsize
4093 Display the number of lines that @code{list} prints.
4096 Repeating a @code{list} command with @key{RET} discards the argument,
4097 so it is equivalent to typing just @code{list}. This is more useful
4098 than listing the same lines again. An exception is made for an
4099 argument of @samp{-}; that argument is preserved in repetition so that
4100 each repetition moves up in the source file.
4103 In general, the @code{list} command expects you to supply zero, one or two
4104 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4105 of writing them, but the effect is always to specify some source line.
4106 Here is a complete description of the possible arguments for @code{list}:
4109 @item list @var{linespec}
4110 Print lines centered around the line specified by @var{linespec}.
4112 @item list @var{first},@var{last}
4113 Print lines from @var{first} to @var{last}. Both arguments are
4116 @item list ,@var{last}
4117 Print lines ending with @var{last}.
4119 @item list @var{first},
4120 Print lines starting with @var{first}.
4123 Print lines just after the lines last printed.
4126 Print lines just before the lines last printed.
4129 As described in the preceding table.
4132 Here are the ways of specifying a single source line---all the
4137 Specifies line @var{number} of the current source file.
4138 When a @code{list} command has two linespecs, this refers to
4139 the same source file as the first linespec.
4142 Specifies the line @var{offset} lines after the last line printed.
4143 When used as the second linespec in a @code{list} command that has
4144 two, this specifies the line @var{offset} lines down from the
4148 Specifies the line @var{offset} lines before the last line printed.
4150 @item @var{filename}:@var{number}
4151 Specifies line @var{number} in the source file @var{filename}.
4153 @item @var{function}
4154 Specifies the line that begins the body of the function @var{function}.
4155 For example: in C, this is the line with the open brace.
4157 @item @var{filename}:@var{function}
4158 Specifies the line of the open-brace that begins the body of the
4159 function @var{function} in the file @var{filename}. You only need the
4160 file name with a function name to avoid ambiguity when there are
4161 identically named functions in different source files.
4163 @item *@var{address}
4164 Specifies the line containing the program address @var{address}.
4165 @var{address} may be any expression.
4169 @section Editing source files
4170 @cindex editing source files
4173 @kindex e @r{(@code{edit})}
4174 To edit the lines in a source file, use the @code{edit} command.
4175 The editing program of your choice
4176 is invoked with the current line set to
4177 the active line in the program.
4178 Alternatively, there are several ways to specify what part of the file you
4179 want to print if you want to see other parts of the program.
4181 Here are the forms of the @code{edit} command most commonly used:
4185 Edit the current source file at the active line number in the program.
4187 @item edit @var{number}
4188 Edit the current source file with @var{number} as the active line number.
4190 @item edit @var{function}
4191 Edit the file containing @var{function} at the beginning of its definition.
4193 @item edit @var{filename}:@var{number}
4194 Specifies line @var{number} in the source file @var{filename}.
4196 @item edit @var{filename}:@var{function}
4197 Specifies the line that begins the body of the
4198 function @var{function} in the file @var{filename}. You only need the
4199 file name with a function name to avoid ambiguity when there are
4200 identically named functions in different source files.
4202 @item edit *@var{address}
4203 Specifies the line containing the program address @var{address}.
4204 @var{address} may be any expression.
4207 @subsection Choosing your editor
4208 You can customize @value{GDBN} to use any editor you want
4210 The only restriction is that your editor (say @code{ex}), recognizes the
4211 following command-line syntax:
4213 ex +@var{number} file
4215 The optional numeric value +@var{number} designates the active line in
4216 the file.}. By default, it is @value{EDITOR}, but you can change this
4217 by setting the environment variable @code{EDITOR} before using
4218 @value{GDBN}. For example, to configure @value{GDBN} to use the
4219 @code{vi} editor, you could use these commands with the @code{sh} shell:
4225 or in the @code{csh} shell,
4227 setenv EDITOR /usr/bin/vi
4232 @section Searching source files
4234 @kindex reverse-search
4236 There are two commands for searching through the current source file for a
4241 @kindex forward-search
4242 @item forward-search @var{regexp}
4243 @itemx search @var{regexp}
4244 The command @samp{forward-search @var{regexp}} checks each line,
4245 starting with the one following the last line listed, for a match for
4246 @var{regexp}. It lists the line that is found. You can use the
4247 synonym @samp{search @var{regexp}} or abbreviate the command name as
4250 @item reverse-search @var{regexp}
4251 The command @samp{reverse-search @var{regexp}} checks each line, starting
4252 with the one before the last line listed and going backward, for a match
4253 for @var{regexp}. It lists the line that is found. You can abbreviate
4254 this command as @code{rev}.
4258 @section Specifying source directories
4261 @cindex directories for source files
4262 Executable programs sometimes do not record the directories of the source
4263 files from which they were compiled, just the names. Even when they do,
4264 the directories could be moved between the compilation and your debugging
4265 session. @value{GDBN} has a list of directories to search for source files;
4266 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4267 it tries all the directories in the list, in the order they are present
4268 in the list, until it finds a file with the desired name. Note that
4269 the executable search path is @emph{not} used for this purpose. Neither is
4270 the current working directory, unless it happens to be in the source
4273 If @value{GDBN} cannot find a source file in the source path, and the
4274 object program records a directory, @value{GDBN} tries that directory
4275 too. If the source path is empty, and there is no record of the
4276 compilation directory, @value{GDBN} looks in the current directory as a
4279 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4280 any information it has cached about where source files are found and where
4281 each line is in the file.
4285 When you start @value{GDBN}, its source path includes only @samp{cdir}
4286 and @samp{cwd}, in that order.
4287 To add other directories, use the @code{directory} command.
4290 @item directory @var{dirname} @dots{}
4291 @item dir @var{dirname} @dots{}
4292 Add directory @var{dirname} to the front of the source path. Several
4293 directory names may be given to this command, separated by @samp{:}
4294 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4295 part of absolute file names) or
4296 whitespace. You may specify a directory that is already in the source
4297 path; this moves it forward, so @value{GDBN} searches it sooner.
4301 @vindex $cdir@r{, convenience variable}
4302 @vindex $cwdr@r{, convenience variable}
4303 @cindex compilation directory
4304 @cindex current directory
4305 @cindex working directory
4306 @cindex directory, current
4307 @cindex directory, compilation
4308 You can use the string @samp{$cdir} to refer to the compilation
4309 directory (if one is recorded), and @samp{$cwd} to refer to the current
4310 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4311 tracks the current working directory as it changes during your @value{GDBN}
4312 session, while the latter is immediately expanded to the current
4313 directory at the time you add an entry to the source path.
4316 Reset the source path to empty again. This requires confirmation.
4318 @c RET-repeat for @code{directory} is explicitly disabled, but since
4319 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4321 @item show directories
4322 @kindex show directories
4323 Print the source path: show which directories it contains.
4326 If your source path is cluttered with directories that are no longer of
4327 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4328 versions of source. You can correct the situation as follows:
4332 Use @code{directory} with no argument to reset the source path to empty.
4335 Use @code{directory} with suitable arguments to reinstall the
4336 directories you want in the source path. You can add all the
4337 directories in one command.
4341 @section Source and machine code
4343 You can use the command @code{info line} to map source lines to program
4344 addresses (and vice versa), and the command @code{disassemble} to display
4345 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4346 mode, the @code{info line} command causes the arrow to point to the
4347 line specified. Also, @code{info line} prints addresses in symbolic form as
4352 @item info line @var{linespec}
4353 Print the starting and ending addresses of the compiled code for
4354 source line @var{linespec}. You can specify source lines in any of
4355 the ways understood by the @code{list} command (@pxref{List, ,Printing
4359 For example, we can use @code{info line} to discover the location of
4360 the object code for the first line of function
4361 @code{m4_changequote}:
4363 @c FIXME: I think this example should also show the addresses in
4364 @c symbolic form, as they usually would be displayed.
4366 (@value{GDBP}) info line m4_changequote
4367 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4371 We can also inquire (using @code{*@var{addr}} as the form for
4372 @var{linespec}) what source line covers a particular address:
4374 (@value{GDBP}) info line *0x63ff
4375 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4378 @cindex @code{$_} and @code{info line}
4379 @kindex x@r{(examine), and} info line
4380 After @code{info line}, the default address for the @code{x} command
4381 is changed to the starting address of the line, so that @samp{x/i} is
4382 sufficient to begin examining the machine code (@pxref{Memory,
4383 ,Examining memory}). Also, this address is saved as the value of the
4384 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4389 @cindex assembly instructions
4390 @cindex instructions, assembly
4391 @cindex machine instructions
4392 @cindex listing machine instructions
4394 This specialized command dumps a range of memory as machine
4395 instructions. The default memory range is the function surrounding the
4396 program counter of the selected frame. A single argument to this
4397 command is a program counter value; @value{GDBN} dumps the function
4398 surrounding this value. Two arguments specify a range of addresses
4399 (first inclusive, second exclusive) to dump.
4402 The following example shows the disassembly of a range of addresses of
4403 HP PA-RISC 2.0 code:
4406 (@value{GDBP}) disas 0x32c4 0x32e4
4407 Dump of assembler code from 0x32c4 to 0x32e4:
4408 0x32c4 <main+204>: addil 0,dp
4409 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4410 0x32cc <main+212>: ldil 0x3000,r31
4411 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4412 0x32d4 <main+220>: ldo 0(r31),rp
4413 0x32d8 <main+224>: addil -0x800,dp
4414 0x32dc <main+228>: ldo 0x588(r1),r26
4415 0x32e0 <main+232>: ldil 0x3000,r31
4416 End of assembler dump.
4419 Some architectures have more than one commonly-used set of instruction
4420 mnemonics or other syntax.
4423 @kindex set disassembly-flavor
4424 @cindex assembly instructions
4425 @cindex instructions, assembly
4426 @cindex machine instructions
4427 @cindex listing machine instructions
4428 @cindex Intel disassembly flavor
4429 @cindex AT&T disassembly flavor
4430 @item set disassembly-flavor @var{instruction-set}
4431 Select the instruction set to use when disassembling the
4432 program via the @code{disassemble} or @code{x/i} commands.
4434 Currently this command is only defined for the Intel x86 family. You
4435 can set @var{instruction-set} to either @code{intel} or @code{att}.
4436 The default is @code{att}, the AT&T flavor used by default by Unix
4437 assemblers for x86-based targets.
4442 @chapter Examining Data
4444 @cindex printing data
4445 @cindex examining data
4448 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4449 @c document because it is nonstandard... Under Epoch it displays in a
4450 @c different window or something like that.
4451 The usual way to examine data in your program is with the @code{print}
4452 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4453 evaluates and prints the value of an expression of the language your
4454 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4455 Different Languages}).
4458 @item print @var{expr}
4459 @itemx print /@var{f} @var{expr}
4460 @var{expr} is an expression (in the source language). By default the
4461 value of @var{expr} is printed in a format appropriate to its data type;
4462 you can choose a different format by specifying @samp{/@var{f}}, where
4463 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4467 @itemx print /@var{f}
4468 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4469 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4470 conveniently inspect the same value in an alternative format.
4473 A more low-level way of examining data is with the @code{x} command.
4474 It examines data in memory at a specified address and prints it in a
4475 specified format. @xref{Memory, ,Examining memory}.
4477 If you are interested in information about types, or about how the
4478 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4479 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4483 * Expressions:: Expressions
4484 * Variables:: Program variables
4485 * Arrays:: Artificial arrays
4486 * Output Formats:: Output formats
4487 * Memory:: Examining memory
4488 * Auto Display:: Automatic display
4489 * Print Settings:: Print settings
4490 * Value History:: Value history
4491 * Convenience Vars:: Convenience variables
4492 * Registers:: Registers
4493 * Floating Point Hardware:: Floating point hardware
4494 * Vector Unit:: Vector Unit
4495 * Memory Region Attributes:: Memory region attributes
4496 * Dump/Restore Files:: Copy between memory and a file
4497 * Character Sets:: Debugging programs that use a different
4498 character set than GDB does
4502 @section Expressions
4505 @code{print} and many other @value{GDBN} commands accept an expression and
4506 compute its value. Any kind of constant, variable or operator defined
4507 by the programming language you are using is valid in an expression in
4508 @value{GDBN}. This includes conditional expressions, function calls,
4509 casts, and string constants. It also includes preprocessor macros, if
4510 you compiled your program to include this information; see
4513 @value{GDBN} supports array constants in expressions input by
4514 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4515 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4516 memory that is @code{malloc}ed in the target program.
4518 Because C is so widespread, most of the expressions shown in examples in
4519 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4520 Languages}, for information on how to use expressions in other
4523 In this section, we discuss operators that you can use in @value{GDBN}
4524 expressions regardless of your programming language.
4526 Casts are supported in all languages, not just in C, because it is so
4527 useful to cast a number into a pointer in order to examine a structure
4528 at that address in memory.
4529 @c FIXME: casts supported---Mod2 true?
4531 @value{GDBN} supports these operators, in addition to those common
4532 to programming languages:
4536 @samp{@@} is a binary operator for treating parts of memory as arrays.
4537 @xref{Arrays, ,Artificial arrays}, for more information.
4540 @samp{::} allows you to specify a variable in terms of the file or
4541 function where it is defined. @xref{Variables, ,Program variables}.
4543 @cindex @{@var{type}@}
4544 @cindex type casting memory
4545 @cindex memory, viewing as typed object
4546 @cindex casts, to view memory
4547 @item @{@var{type}@} @var{addr}
4548 Refers to an object of type @var{type} stored at address @var{addr} in
4549 memory. @var{addr} may be any expression whose value is an integer or
4550 pointer (but parentheses are required around binary operators, just as in
4551 a cast). This construct is allowed regardless of what kind of data is
4552 normally supposed to reside at @var{addr}.
4556 @section Program variables
4558 The most common kind of expression to use is the name of a variable
4561 Variables in expressions are understood in the selected stack frame
4562 (@pxref{Selection, ,Selecting a frame}); they must be either:
4566 global (or file-static)
4573 visible according to the scope rules of the
4574 programming language from the point of execution in that frame
4577 @noindent This means that in the function
4592 you can examine and use the variable @code{a} whenever your program is
4593 executing within the function @code{foo}, but you can only use or
4594 examine the variable @code{b} while your program is executing inside
4595 the block where @code{b} is declared.
4597 @cindex variable name conflict
4598 There is an exception: you can refer to a variable or function whose
4599 scope is a single source file even if the current execution point is not
4600 in this file. But it is possible to have more than one such variable or
4601 function with the same name (in different source files). If that
4602 happens, referring to that name has unpredictable effects. If you wish,
4603 you can specify a static variable in a particular function or file,
4604 using the colon-colon notation:
4606 @cindex colon-colon, context for variables/functions
4608 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4609 @cindex @code{::}, context for variables/functions
4612 @var{file}::@var{variable}
4613 @var{function}::@var{variable}
4617 Here @var{file} or @var{function} is the name of the context for the
4618 static @var{variable}. In the case of file names, you can use quotes to
4619 make sure @value{GDBN} parses the file name as a single word---for example,
4620 to print a global value of @code{x} defined in @file{f2.c}:
4623 (@value{GDBP}) p 'f2.c'::x
4626 @cindex C@t{++} scope resolution
4627 This use of @samp{::} is very rarely in conflict with the very similar
4628 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4629 scope resolution operator in @value{GDBN} expressions.
4630 @c FIXME: Um, so what happens in one of those rare cases where it's in
4633 @cindex wrong values
4634 @cindex variable values, wrong
4636 @emph{Warning:} Occasionally, a local variable may appear to have the
4637 wrong value at certain points in a function---just after entry to a new
4638 scope, and just before exit.
4640 You may see this problem when you are stepping by machine instructions.
4641 This is because, on most machines, it takes more than one instruction to
4642 set up a stack frame (including local variable definitions); if you are
4643 stepping by machine instructions, variables may appear to have the wrong
4644 values until the stack frame is completely built. On exit, it usually
4645 also takes more than one machine instruction to destroy a stack frame;
4646 after you begin stepping through that group of instructions, local
4647 variable definitions may be gone.
4649 This may also happen when the compiler does significant optimizations.
4650 To be sure of always seeing accurate values, turn off all optimization
4653 @cindex ``No symbol "foo" in current context''
4654 Another possible effect of compiler optimizations is to optimize
4655 unused variables out of existence, or assign variables to registers (as
4656 opposed to memory addresses). Depending on the support for such cases
4657 offered by the debug info format used by the compiler, @value{GDBN}
4658 might not be able to display values for such local variables. If that
4659 happens, @value{GDBN} will print a message like this:
4662 No symbol "foo" in current context.
4665 To solve such problems, either recompile without optimizations, or use a
4666 different debug info format, if the compiler supports several such
4667 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually
4668 supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info
4669 in a format that is superior to formats such as COFF. You may be able
4670 to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for
4671 debug info. See @ref{Debugging Options,,Options for Debugging Your
4672 Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more
4677 @section Artificial arrays
4679 @cindex artificial array
4680 @kindex @@@r{, referencing memory as an array}
4681 It is often useful to print out several successive objects of the
4682 same type in memory; a section of an array, or an array of
4683 dynamically determined size for which only a pointer exists in the
4686 You can do this by referring to a contiguous span of memory as an
4687 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4688 operand of @samp{@@} should be the first element of the desired array
4689 and be an individual object. The right operand should be the desired length
4690 of the array. The result is an array value whose elements are all of
4691 the type of the left argument. The first element is actually the left
4692 argument; the second element comes from bytes of memory immediately
4693 following those that hold the first element, and so on. Here is an
4694 example. If a program says
4697 int *array = (int *) malloc (len * sizeof (int));
4701 you can print the contents of @code{array} with
4707 The left operand of @samp{@@} must reside in memory. Array values made
4708 with @samp{@@} in this way behave just like other arrays in terms of
4709 subscripting, and are coerced to pointers when used in expressions.
4710 Artificial arrays most often appear in expressions via the value history
4711 (@pxref{Value History, ,Value history}), after printing one out.
4713 Another way to create an artificial array is to use a cast.
4714 This re-interprets a value as if it were an array.
4715 The value need not be in memory:
4717 (@value{GDBP}) p/x (short[2])0x12345678
4718 $1 = @{0x1234, 0x5678@}
4721 As a convenience, if you leave the array length out (as in
4722 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4723 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4725 (@value{GDBP}) p/x (short[])0x12345678
4726 $2 = @{0x1234, 0x5678@}
4729 Sometimes the artificial array mechanism is not quite enough; in
4730 moderately complex data structures, the elements of interest may not
4731 actually be adjacent---for example, if you are interested in the values
4732 of pointers in an array. One useful work-around in this situation is
4733 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4734 variables}) as a counter in an expression that prints the first
4735 interesting value, and then repeat that expression via @key{RET}. For
4736 instance, suppose you have an array @code{dtab} of pointers to
4737 structures, and you are interested in the values of a field @code{fv}
4738 in each structure. Here is an example of what you might type:
4748 @node Output Formats
4749 @section Output formats
4751 @cindex formatted output
4752 @cindex output formats
4753 By default, @value{GDBN} prints a value according to its data type. Sometimes
4754 this is not what you want. For example, you might want to print a number
4755 in hex, or a pointer in decimal. Or you might want to view data in memory
4756 at a certain address as a character string or as an instruction. To do
4757 these things, specify an @dfn{output format} when you print a value.
4759 The simplest use of output formats is to say how to print a value
4760 already computed. This is done by starting the arguments of the
4761 @code{print} command with a slash and a format letter. The format
4762 letters supported are:
4766 Regard the bits of the value as an integer, and print the integer in
4770 Print as integer in signed decimal.
4773 Print as integer in unsigned decimal.
4776 Print as integer in octal.
4779 Print as integer in binary. The letter @samp{t} stands for ``two''.
4780 @footnote{@samp{b} cannot be used because these format letters are also
4781 used with the @code{x} command, where @samp{b} stands for ``byte'';
4782 see @ref{Memory,,Examining memory}.}
4785 @cindex unknown address, locating
4786 @cindex locate address
4787 Print as an address, both absolute in hexadecimal and as an offset from
4788 the nearest preceding symbol. You can use this format used to discover
4789 where (in what function) an unknown address is located:
4792 (@value{GDBP}) p/a 0x54320
4793 $3 = 0x54320 <_initialize_vx+396>
4797 The command @code{info symbol 0x54320} yields similar results.
4798 @xref{Symbols, info symbol}.
4801 Regard as an integer and print it as a character constant.
4804 Regard the bits of the value as a floating point number and print
4805 using typical floating point syntax.
4808 For example, to print the program counter in hex (@pxref{Registers}), type
4815 Note that no space is required before the slash; this is because command
4816 names in @value{GDBN} cannot contain a slash.
4818 To reprint the last value in the value history with a different format,
4819 you can use the @code{print} command with just a format and no
4820 expression. For example, @samp{p/x} reprints the last value in hex.
4823 @section Examining memory
4825 You can use the command @code{x} (for ``examine'') to examine memory in
4826 any of several formats, independently of your program's data types.
4828 @cindex examining memory
4830 @kindex x @r{(examine memory)}
4831 @item x/@var{nfu} @var{addr}
4834 Use the @code{x} command to examine memory.
4837 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4838 much memory to display and how to format it; @var{addr} is an
4839 expression giving the address where you want to start displaying memory.
4840 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4841 Several commands set convenient defaults for @var{addr}.
4844 @item @var{n}, the repeat count
4845 The repeat count is a decimal integer; the default is 1. It specifies
4846 how much memory (counting by units @var{u}) to display.
4847 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4850 @item @var{f}, the display format
4851 The display format is one of the formats used by @code{print},
4852 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4853 The default is @samp{x} (hexadecimal) initially.
4854 The default changes each time you use either @code{x} or @code{print}.
4856 @item @var{u}, the unit size
4857 The unit size is any of
4863 Halfwords (two bytes).
4865 Words (four bytes). This is the initial default.
4867 Giant words (eight bytes).
4870 Each time you specify a unit size with @code{x}, that size becomes the
4871 default unit the next time you use @code{x}. (For the @samp{s} and
4872 @samp{i} formats, the unit size is ignored and is normally not written.)
4874 @item @var{addr}, starting display address
4875 @var{addr} is the address where you want @value{GDBN} to begin displaying
4876 memory. The expression need not have a pointer value (though it may);
4877 it is always interpreted as an integer address of a byte of memory.
4878 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4879 @var{addr} is usually just after the last address examined---but several
4880 other commands also set the default address: @code{info breakpoints} (to
4881 the address of the last breakpoint listed), @code{info line} (to the
4882 starting address of a line), and @code{print} (if you use it to display
4883 a value from memory).
4886 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4887 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4888 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4889 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4890 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4892 Since the letters indicating unit sizes are all distinct from the
4893 letters specifying output formats, you do not have to remember whether
4894 unit size or format comes first; either order works. The output
4895 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4896 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4898 Even though the unit size @var{u} is ignored for the formats @samp{s}
4899 and @samp{i}, you might still want to use a count @var{n}; for example,
4900 @samp{3i} specifies that you want to see three machine instructions,
4901 including any operands. The command @code{disassemble} gives an
4902 alternative way of inspecting machine instructions; see @ref{Machine
4903 Code,,Source and machine code}.
4905 All the defaults for the arguments to @code{x} are designed to make it
4906 easy to continue scanning memory with minimal specifications each time
4907 you use @code{x}. For example, after you have inspected three machine
4908 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4909 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4910 the repeat count @var{n} is used again; the other arguments default as
4911 for successive uses of @code{x}.
4913 @cindex @code{$_}, @code{$__}, and value history
4914 The addresses and contents printed by the @code{x} command are not saved
4915 in the value history because there is often too much of them and they
4916 would get in the way. Instead, @value{GDBN} makes these values available for
4917 subsequent use in expressions as values of the convenience variables
4918 @code{$_} and @code{$__}. After an @code{x} command, the last address
4919 examined is available for use in expressions in the convenience variable
4920 @code{$_}. The contents of that address, as examined, are available in
4921 the convenience variable @code{$__}.
4923 If the @code{x} command has a repeat count, the address and contents saved
4924 are from the last memory unit printed; this is not the same as the last
4925 address printed if several units were printed on the last line of output.
4928 @section Automatic display
4929 @cindex automatic display
4930 @cindex display of expressions
4932 If you find that you want to print the value of an expression frequently
4933 (to see how it changes), you might want to add it to the @dfn{automatic
4934 display list} so that @value{GDBN} prints its value each time your program stops.
4935 Each expression added to the list is given a number to identify it;
4936 to remove an expression from the list, you specify that number.
4937 The automatic display looks like this:
4941 3: bar[5] = (struct hack *) 0x3804
4945 This display shows item numbers, expressions and their current values. As with
4946 displays you request manually using @code{x} or @code{print}, you can
4947 specify the output format you prefer; in fact, @code{display} decides
4948 whether to use @code{print} or @code{x} depending on how elaborate your
4949 format specification is---it uses @code{x} if you specify a unit size,
4950 or one of the two formats (@samp{i} and @samp{s}) that are only
4951 supported by @code{x}; otherwise it uses @code{print}.
4955 @item display @var{expr}
4956 Add the expression @var{expr} to the list of expressions to display
4957 each time your program stops. @xref{Expressions, ,Expressions}.
4959 @code{display} does not repeat if you press @key{RET} again after using it.
4961 @item display/@var{fmt} @var{expr}
4962 For @var{fmt} specifying only a display format and not a size or
4963 count, add the expression @var{expr} to the auto-display list but
4964 arrange to display it each time in the specified format @var{fmt}.
4965 @xref{Output Formats,,Output formats}.
4967 @item display/@var{fmt} @var{addr}
4968 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
4969 number of units, add the expression @var{addr} as a memory address to
4970 be examined each time your program stops. Examining means in effect
4971 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
4974 For example, @samp{display/i $pc} can be helpful, to see the machine
4975 instruction about to be executed each time execution stops (@samp{$pc}
4976 is a common name for the program counter; @pxref{Registers, ,Registers}).
4979 @kindex delete display
4981 @item undisplay @var{dnums}@dots{}
4982 @itemx delete display @var{dnums}@dots{}
4983 Remove item numbers @var{dnums} from the list of expressions to display.
4985 @code{undisplay} does not repeat if you press @key{RET} after using it.
4986 (Otherwise you would just get the error @samp{No display number @dots{}}.)
4988 @kindex disable display
4989 @item disable display @var{dnums}@dots{}
4990 Disable the display of item numbers @var{dnums}. A disabled display
4991 item is not printed automatically, but is not forgotten. It may be
4992 enabled again later.
4994 @kindex enable display
4995 @item enable display @var{dnums}@dots{}
4996 Enable display of item numbers @var{dnums}. It becomes effective once
4997 again in auto display of its expression, until you specify otherwise.
5000 Display the current values of the expressions on the list, just as is
5001 done when your program stops.
5003 @kindex info display
5005 Print the list of expressions previously set up to display
5006 automatically, each one with its item number, but without showing the
5007 values. This includes disabled expressions, which are marked as such.
5008 It also includes expressions which would not be displayed right now
5009 because they refer to automatic variables not currently available.
5012 If a display expression refers to local variables, then it does not make
5013 sense outside the lexical context for which it was set up. Such an
5014 expression is disabled when execution enters a context where one of its
5015 variables is not defined. For example, if you give the command
5016 @code{display last_char} while inside a function with an argument
5017 @code{last_char}, @value{GDBN} displays this argument while your program
5018 continues to stop inside that function. When it stops elsewhere---where
5019 there is no variable @code{last_char}---the display is disabled
5020 automatically. The next time your program stops where @code{last_char}
5021 is meaningful, you can enable the display expression once again.
5023 @node Print Settings
5024 @section Print settings
5026 @cindex format options
5027 @cindex print settings
5028 @value{GDBN} provides the following ways to control how arrays, structures,
5029 and symbols are printed.
5032 These settings are useful for debugging programs in any language:
5035 @kindex set print address
5036 @item set print address
5037 @itemx set print address on
5038 @value{GDBN} prints memory addresses showing the location of stack
5039 traces, structure values, pointer values, breakpoints, and so forth,
5040 even when it also displays the contents of those addresses. The default
5041 is @code{on}. For example, this is what a stack frame display looks like with
5042 @code{set print address on}:
5047 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5049 530 if (lquote != def_lquote)
5053 @item set print address off
5054 Do not print addresses when displaying their contents. For example,
5055 this is the same stack frame displayed with @code{set print address off}:
5059 (@value{GDBP}) set print addr off
5061 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5062 530 if (lquote != def_lquote)
5066 You can use @samp{set print address off} to eliminate all machine
5067 dependent displays from the @value{GDBN} interface. For example, with
5068 @code{print address off}, you should get the same text for backtraces on
5069 all machines---whether or not they involve pointer arguments.
5071 @kindex show print address
5072 @item show print address
5073 Show whether or not addresses are to be printed.
5076 When @value{GDBN} prints a symbolic address, it normally prints the
5077 closest earlier symbol plus an offset. If that symbol does not uniquely
5078 identify the address (for example, it is a name whose scope is a single
5079 source file), you may need to clarify. One way to do this is with
5080 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5081 you can set @value{GDBN} to print the source file and line number when
5082 it prints a symbolic address:
5085 @kindex set print symbol-filename
5086 @item set print symbol-filename on
5087 Tell @value{GDBN} to print the source file name and line number of a
5088 symbol in the symbolic form of an address.
5090 @item set print symbol-filename off
5091 Do not print source file name and line number of a symbol. This is the
5094 @kindex show print symbol-filename
5095 @item show print symbol-filename
5096 Show whether or not @value{GDBN} will print the source file name and
5097 line number of a symbol in the symbolic form of an address.
5100 Another situation where it is helpful to show symbol filenames and line
5101 numbers is when disassembling code; @value{GDBN} shows you the line
5102 number and source file that corresponds to each instruction.
5104 Also, you may wish to see the symbolic form only if the address being
5105 printed is reasonably close to the closest earlier symbol:
5108 @kindex set print max-symbolic-offset
5109 @item set print max-symbolic-offset @var{max-offset}
5110 Tell @value{GDBN} to only display the symbolic form of an address if the
5111 offset between the closest earlier symbol and the address is less than
5112 @var{max-offset}. The default is 0, which tells @value{GDBN}
5113 to always print the symbolic form of an address if any symbol precedes it.
5115 @kindex show print max-symbolic-offset
5116 @item show print max-symbolic-offset
5117 Ask how large the maximum offset is that @value{GDBN} prints in a
5121 @cindex wild pointer, interpreting
5122 @cindex pointer, finding referent
5123 If you have a pointer and you are not sure where it points, try
5124 @samp{set print symbol-filename on}. Then you can determine the name
5125 and source file location of the variable where it points, using
5126 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5127 For example, here @value{GDBN} shows that a variable @code{ptt} points
5128 at another variable @code{t}, defined in @file{hi2.c}:
5131 (@value{GDBP}) set print symbol-filename on
5132 (@value{GDBP}) p/a ptt
5133 $4 = 0xe008 <t in hi2.c>
5137 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5138 does not show the symbol name and filename of the referent, even with
5139 the appropriate @code{set print} options turned on.
5142 Other settings control how different kinds of objects are printed:
5145 @kindex set print array
5146 @item set print array
5147 @itemx set print array on
5148 Pretty print arrays. This format is more convenient to read,
5149 but uses more space. The default is off.
5151 @item set print array off
5152 Return to compressed format for arrays.
5154 @kindex show print array
5155 @item show print array
5156 Show whether compressed or pretty format is selected for displaying
5159 @kindex set print elements
5160 @item set print elements @var{number-of-elements}
5161 Set a limit on how many elements of an array @value{GDBN} will print.
5162 If @value{GDBN} is printing a large array, it stops printing after it has
5163 printed the number of elements set by the @code{set print elements} command.
5164 This limit also applies to the display of strings.
5165 When @value{GDBN} starts, this limit is set to 200.
5166 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5168 @kindex show print elements
5169 @item show print elements
5170 Display the number of elements of a large array that @value{GDBN} will print.
5171 If the number is 0, then the printing is unlimited.
5173 @kindex set print null-stop
5174 @item set print null-stop
5175 Cause @value{GDBN} to stop printing the characters of an array when the first
5176 @sc{null} is encountered. This is useful when large arrays actually
5177 contain only short strings.
5180 @kindex set print pretty
5181 @item set print pretty on
5182 Cause @value{GDBN} to print structures in an indented format with one member
5183 per line, like this:
5198 @item set print pretty off
5199 Cause @value{GDBN} to print structures in a compact format, like this:
5203 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5204 meat = 0x54 "Pork"@}
5209 This is the default format.
5211 @kindex show print pretty
5212 @item show print pretty
5213 Show which format @value{GDBN} is using to print structures.
5215 @kindex set print sevenbit-strings
5216 @item set print sevenbit-strings on
5217 Print using only seven-bit characters; if this option is set,
5218 @value{GDBN} displays any eight-bit characters (in strings or
5219 character values) using the notation @code{\}@var{nnn}. This setting is
5220 best if you are working in English (@sc{ascii}) and you use the
5221 high-order bit of characters as a marker or ``meta'' bit.
5223 @item set print sevenbit-strings off
5224 Print full eight-bit characters. This allows the use of more
5225 international character sets, and is the default.
5227 @kindex show print sevenbit-strings
5228 @item show print sevenbit-strings
5229 Show whether or not @value{GDBN} is printing only seven-bit characters.
5231 @kindex set print union
5232 @item set print union on
5233 Tell @value{GDBN} to print unions which are contained in structures. This
5234 is the default setting.
5236 @item set print union off
5237 Tell @value{GDBN} not to print unions which are contained in structures.
5239 @kindex show print union
5240 @item show print union
5241 Ask @value{GDBN} whether or not it will print unions which are contained in
5244 For example, given the declarations
5247 typedef enum @{Tree, Bug@} Species;
5248 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5249 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5260 struct thing foo = @{Tree, @{Acorn@}@};
5264 with @code{set print union on} in effect @samp{p foo} would print
5267 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5271 and with @code{set print union off} in effect it would print
5274 $1 = @{it = Tree, form = @{...@}@}
5280 These settings are of interest when debugging C@t{++} programs:
5284 @kindex set print demangle
5285 @item set print demangle
5286 @itemx set print demangle on
5287 Print C@t{++} names in their source form rather than in the encoded
5288 (``mangled'') form passed to the assembler and linker for type-safe
5289 linkage. The default is on.
5291 @kindex show print demangle
5292 @item show print demangle
5293 Show whether C@t{++} names are printed in mangled or demangled form.
5295 @kindex set print asm-demangle
5296 @item set print asm-demangle
5297 @itemx set print asm-demangle on
5298 Print C@t{++} names in their source form rather than their mangled form, even
5299 in assembler code printouts such as instruction disassemblies.
5302 @kindex show print asm-demangle
5303 @item show print asm-demangle
5304 Show whether C@t{++} names in assembly listings are printed in mangled
5307 @kindex set demangle-style
5308 @cindex C@t{++} symbol decoding style
5309 @cindex symbol decoding style, C@t{++}
5310 @item set demangle-style @var{style}
5311 Choose among several encoding schemes used by different compilers to
5312 represent C@t{++} names. The choices for @var{style} are currently:
5316 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5319 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5320 This is the default.
5323 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5326 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5329 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5330 @strong{Warning:} this setting alone is not sufficient to allow
5331 debugging @code{cfront}-generated executables. @value{GDBN} would
5332 require further enhancement to permit that.
5335 If you omit @var{style}, you will see a list of possible formats.
5337 @kindex show demangle-style
5338 @item show demangle-style
5339 Display the encoding style currently in use for decoding C@t{++} symbols.
5341 @kindex set print object
5342 @item set print object
5343 @itemx set print object on
5344 When displaying a pointer to an object, identify the @emph{actual}
5345 (derived) type of the object rather than the @emph{declared} type, using
5346 the virtual function table.
5348 @item set print object off
5349 Display only the declared type of objects, without reference to the
5350 virtual function table. This is the default setting.
5352 @kindex show print object
5353 @item show print object
5354 Show whether actual, or declared, object types are displayed.
5356 @kindex set print static-members
5357 @item set print static-members
5358 @itemx set print static-members on
5359 Print static members when displaying a C@t{++} object. The default is on.
5361 @item set print static-members off
5362 Do not print static members when displaying a C@t{++} object.
5364 @kindex show print static-members
5365 @item show print static-members
5366 Show whether C@t{++} static members are printed, or not.
5368 @c These don't work with HP ANSI C++ yet.
5369 @kindex set print vtbl
5370 @item set print vtbl
5371 @itemx set print vtbl on
5372 Pretty print C@t{++} virtual function tables. The default is off.
5373 (The @code{vtbl} commands do not work on programs compiled with the HP
5374 ANSI C@t{++} compiler (@code{aCC}).)
5376 @item set print vtbl off
5377 Do not pretty print C@t{++} virtual function tables.
5379 @kindex show print vtbl
5380 @item show print vtbl
5381 Show whether C@t{++} virtual function tables are pretty printed, or not.
5385 @section Value history
5387 @cindex value history
5388 Values printed by the @code{print} command are saved in the @value{GDBN}
5389 @dfn{value history}. This allows you to refer to them in other expressions.
5390 Values are kept until the symbol table is re-read or discarded
5391 (for example with the @code{file} or @code{symbol-file} commands).
5392 When the symbol table changes, the value history is discarded,
5393 since the values may contain pointers back to the types defined in the
5398 @cindex history number
5399 The values printed are given @dfn{history numbers} by which you can
5400 refer to them. These are successive integers starting with one.
5401 @code{print} shows you the history number assigned to a value by
5402 printing @samp{$@var{num} = } before the value; here @var{num} is the
5405 To refer to any previous value, use @samp{$} followed by the value's
5406 history number. The way @code{print} labels its output is designed to
5407 remind you of this. Just @code{$} refers to the most recent value in
5408 the history, and @code{$$} refers to the value before that.
5409 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5410 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5411 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5413 For example, suppose you have just printed a pointer to a structure and
5414 want to see the contents of the structure. It suffices to type
5420 If you have a chain of structures where the component @code{next} points
5421 to the next one, you can print the contents of the next one with this:
5428 You can print successive links in the chain by repeating this
5429 command---which you can do by just typing @key{RET}.
5431 Note that the history records values, not expressions. If the value of
5432 @code{x} is 4 and you type these commands:
5440 then the value recorded in the value history by the @code{print} command
5441 remains 4 even though the value of @code{x} has changed.
5446 Print the last ten values in the value history, with their item numbers.
5447 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5448 values} does not change the history.
5450 @item show values @var{n}
5451 Print ten history values centered on history item number @var{n}.
5454 Print ten history values just after the values last printed. If no more
5455 values are available, @code{show values +} produces no display.
5458 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5459 same effect as @samp{show values +}.
5461 @node Convenience Vars
5462 @section Convenience variables
5464 @cindex convenience variables
5465 @value{GDBN} provides @dfn{convenience variables} that you can use within
5466 @value{GDBN} to hold on to a value and refer to it later. These variables
5467 exist entirely within @value{GDBN}; they are not part of your program, and
5468 setting a convenience variable has no direct effect on further execution
5469 of your program. That is why you can use them freely.
5471 Convenience variables are prefixed with @samp{$}. Any name preceded by
5472 @samp{$} can be used for a convenience variable, unless it is one of
5473 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5474 (Value history references, in contrast, are @emph{numbers} preceded
5475 by @samp{$}. @xref{Value History, ,Value history}.)
5477 You can save a value in a convenience variable with an assignment
5478 expression, just as you would set a variable in your program.
5482 set $foo = *object_ptr
5486 would save in @code{$foo} the value contained in the object pointed to by
5489 Using a convenience variable for the first time creates it, but its
5490 value is @code{void} until you assign a new value. You can alter the
5491 value with another assignment at any time.
5493 Convenience variables have no fixed types. You can assign a convenience
5494 variable any type of value, including structures and arrays, even if
5495 that variable already has a value of a different type. The convenience
5496 variable, when used as an expression, has the type of its current value.
5499 @kindex show convenience
5500 @item show convenience
5501 Print a list of convenience variables used so far, and their values.
5502 Abbreviated @code{show conv}.
5505 One of the ways to use a convenience variable is as a counter to be
5506 incremented or a pointer to be advanced. For example, to print
5507 a field from successive elements of an array of structures:
5511 print bar[$i++]->contents
5515 Repeat that command by typing @key{RET}.
5517 Some convenience variables are created automatically by @value{GDBN} and given
5518 values likely to be useful.
5521 @vindex $_@r{, convenience variable}
5523 The variable @code{$_} is automatically set by the @code{x} command to
5524 the last address examined (@pxref{Memory, ,Examining memory}). Other
5525 commands which provide a default address for @code{x} to examine also
5526 set @code{$_} to that address; these commands include @code{info line}
5527 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5528 except when set by the @code{x} command, in which case it is a pointer
5529 to the type of @code{$__}.
5531 @vindex $__@r{, convenience variable}
5533 The variable @code{$__} is automatically set by the @code{x} command
5534 to the value found in the last address examined. Its type is chosen
5535 to match the format in which the data was printed.
5538 @vindex $_exitcode@r{, convenience variable}
5539 The variable @code{$_exitcode} is automatically set to the exit code when
5540 the program being debugged terminates.
5543 On HP-UX systems, if you refer to a function or variable name that
5544 begins with a dollar sign, @value{GDBN} searches for a user or system
5545 name first, before it searches for a convenience variable.
5551 You can refer to machine register contents, in expressions, as variables
5552 with names starting with @samp{$}. The names of registers are different
5553 for each machine; use @code{info registers} to see the names used on
5557 @kindex info registers
5558 @item info registers
5559 Print the names and values of all registers except floating-point
5560 registers (in the selected stack frame).
5562 @kindex info all-registers
5563 @cindex floating point registers
5564 @item info all-registers
5565 Print the names and values of all registers, including floating-point
5568 @item info registers @var{regname} @dots{}
5569 Print the @dfn{relativized} value of each specified register @var{regname}.
5570 As discussed in detail below, register values are normally relative to
5571 the selected stack frame. @var{regname} may be any register name valid on
5572 the machine you are using, with or without the initial @samp{$}.
5575 @value{GDBN} has four ``standard'' register names that are available (in
5576 expressions) on most machines---whenever they do not conflict with an
5577 architecture's canonical mnemonics for registers. The register names
5578 @code{$pc} and @code{$sp} are used for the program counter register and
5579 the stack pointer. @code{$fp} is used for a register that contains a
5580 pointer to the current stack frame, and @code{$ps} is used for a
5581 register that contains the processor status. For example,
5582 you could print the program counter in hex with
5589 or print the instruction to be executed next with
5596 or add four to the stack pointer@footnote{This is a way of removing
5597 one word from the stack, on machines where stacks grow downward in
5598 memory (most machines, nowadays). This assumes that the innermost
5599 stack frame is selected; setting @code{$sp} is not allowed when other
5600 stack frames are selected. To pop entire frames off the stack,
5601 regardless of machine architecture, use @code{return};
5602 see @ref{Returning, ,Returning from a function}.} with
5608 Whenever possible, these four standard register names are available on
5609 your machine even though the machine has different canonical mnemonics,
5610 so long as there is no conflict. The @code{info registers} command
5611 shows the canonical names. For example, on the SPARC, @code{info
5612 registers} displays the processor status register as @code{$psr} but you
5613 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5614 is an alias for the @sc{eflags} register.
5616 @value{GDBN} always considers the contents of an ordinary register as an
5617 integer when the register is examined in this way. Some machines have
5618 special registers which can hold nothing but floating point; these
5619 registers are considered to have floating point values. There is no way
5620 to refer to the contents of an ordinary register as floating point value
5621 (although you can @emph{print} it as a floating point value with
5622 @samp{print/f $@var{regname}}).
5624 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5625 means that the data format in which the register contents are saved by
5626 the operating system is not the same one that your program normally
5627 sees. For example, the registers of the 68881 floating point
5628 coprocessor are always saved in ``extended'' (raw) format, but all C
5629 programs expect to work with ``double'' (virtual) format. In such
5630 cases, @value{GDBN} normally works with the virtual format only (the format
5631 that makes sense for your program), but the @code{info registers} command
5632 prints the data in both formats.
5634 Normally, register values are relative to the selected stack frame
5635 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5636 value that the register would contain if all stack frames farther in
5637 were exited and their saved registers restored. In order to see the
5638 true contents of hardware registers, you must select the innermost
5639 frame (with @samp{frame 0}).
5641 However, @value{GDBN} must deduce where registers are saved, from the machine
5642 code generated by your compiler. If some registers are not saved, or if
5643 @value{GDBN} is unable to locate the saved registers, the selected stack
5644 frame makes no difference.
5646 @node Floating Point Hardware
5647 @section Floating point hardware
5648 @cindex floating point
5650 Depending on the configuration, @value{GDBN} may be able to give
5651 you more information about the status of the floating point hardware.
5656 Display hardware-dependent information about the floating
5657 point unit. The exact contents and layout vary depending on the
5658 floating point chip. Currently, @samp{info float} is supported on
5659 the ARM and x86 machines.
5663 @section Vector Unit
5666 Depending on the configuration, @value{GDBN} may be able to give you
5667 more information about the status of the vector unit.
5672 Display information about the vector unit. The exact contents and
5673 layout vary depending on the hardware.
5676 @node Memory Region Attributes
5677 @section Memory region attributes
5678 @cindex memory region attributes
5680 @dfn{Memory region attributes} allow you to describe special handling
5681 required by regions of your target's memory. @value{GDBN} uses attributes
5682 to determine whether to allow certain types of memory accesses; whether to
5683 use specific width accesses; and whether to cache target memory.
5685 Defined memory regions can be individually enabled and disabled. When a
5686 memory region is disabled, @value{GDBN} uses the default attributes when
5687 accessing memory in that region. Similarly, if no memory regions have
5688 been defined, @value{GDBN} uses the default attributes when accessing
5691 When a memory region is defined, it is given a number to identify it;
5692 to enable, disable, or remove a memory region, you specify that number.
5696 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5697 Define memory region bounded by @var{lower} and @var{upper} with
5698 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5699 special case: it is treated as the the target's maximum memory address.
5700 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5703 @item delete mem @var{nums}@dots{}
5704 Remove memory regions @var{nums}@dots{}.
5707 @item disable mem @var{nums}@dots{}
5708 Disable memory regions @var{nums}@dots{}.
5709 A disabled memory region is not forgotten.
5710 It may be enabled again later.
5713 @item enable mem @var{nums}@dots{}
5714 Enable memory regions @var{nums}@dots{}.
5718 Print a table of all defined memory regions, with the following columns
5722 @item Memory Region Number
5723 @item Enabled or Disabled.
5724 Enabled memory regions are marked with @samp{y}.
5725 Disabled memory regions are marked with @samp{n}.
5728 The address defining the inclusive lower bound of the memory region.
5731 The address defining the exclusive upper bound of the memory region.
5734 The list of attributes set for this memory region.
5739 @subsection Attributes
5741 @subsubsection Memory Access Mode
5742 The access mode attributes set whether @value{GDBN} may make read or
5743 write accesses to a memory region.
5745 While these attributes prevent @value{GDBN} from performing invalid
5746 memory accesses, they do nothing to prevent the target system, I/O DMA,
5747 etc. from accessing memory.
5751 Memory is read only.
5753 Memory is write only.
5755 Memory is read/write. This is the default.
5758 @subsubsection Memory Access Size
5759 The acccess size attributes tells @value{GDBN} to use specific sized
5760 accesses in the memory region. Often memory mapped device registers
5761 require specific sized accesses. If no access size attribute is
5762 specified, @value{GDBN} may use accesses of any size.
5766 Use 8 bit memory accesses.
5768 Use 16 bit memory accesses.
5770 Use 32 bit memory accesses.
5772 Use 64 bit memory accesses.
5775 @c @subsubsection Hardware/Software Breakpoints
5776 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5777 @c will use hardware or software breakpoints for the internal breakpoints
5778 @c used by the step, next, finish, until, etc. commands.
5782 @c Always use hardware breakpoints
5783 @c @item swbreak (default)
5786 @subsubsection Data Cache
5787 The data cache attributes set whether @value{GDBN} will cache target
5788 memory. While this generally improves performance by reducing debug
5789 protocol overhead, it can lead to incorrect results because @value{GDBN}
5790 does not know about volatile variables or memory mapped device
5795 Enable @value{GDBN} to cache target memory.
5797 Disable @value{GDBN} from caching target memory. This is the default.
5800 @c @subsubsection Memory Write Verification
5801 @c The memory write verification attributes set whether @value{GDBN}
5802 @c will re-reads data after each write to verify the write was successful.
5806 @c @item noverify (default)
5809 @node Dump/Restore Files
5810 @section Copy between memory and a file
5811 @cindex dump/restore files
5812 @cindex append data to a file
5813 @cindex dump data to a file
5814 @cindex restore data from a file
5819 The commands @code{dump}, @code{append}, and @code{restore} are used
5820 for copying data between target memory and a file. Data is written
5821 into a file using @code{dump} or @code{append}, and restored from a
5822 file into memory by using @code{restore}. Files may be binary, srec,
5823 intel hex, or tekhex (but only binary files can be appended).
5827 @kindex append binary
5828 @item dump binary memory @var{filename} @var{start_addr} @var{end_addr}
5829 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5830 raw binary format file @var{filename}.
5832 @item append binary memory @var{filename} @var{start_addr} @var{end_addr}
5833 Append contents of memory from @var{start_addr} to @var{end_addr} to
5834 raw binary format file @var{filename}.
5836 @item dump binary value @var{filename} @var{expression}
5837 Dump value of @var{expression} into raw binary format file @var{filename}.
5839 @item append binary memory @var{filename} @var{expression}
5840 Append value of @var{expression} to raw binary format file @var{filename}.
5843 @item dump ihex memory @var{filename} @var{start_addr} @var{end_addr}
5844 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5845 intel hex format file @var{filename}.
5847 @item dump ihex value @var{filename} @var{expression}
5848 Dump value of @var{expression} into intel hex format file @var{filename}.
5851 @item dump srec memory @var{filename} @var{start_addr} @var{end_addr}
5852 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5853 srec format file @var{filename}.
5855 @item dump srec value @var{filename} @var{expression}
5856 Dump value of @var{expression} into srec format file @var{filename}.
5859 @item dump tekhex memory @var{filename} @var{start_addr} @var{end_addr}
5860 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5861 tekhex format file @var{filename}.
5863 @item dump tekhex value @var{filename} @var{expression}
5864 Dump value of @var{expression} into tekhex format file @var{filename}.
5866 @item restore @var{filename} [@var{binary}] @var{bias} @var{start} @var{end}
5867 Restore the contents of file @var{filename} into memory. The @code{restore}
5868 command can automatically recognize any known bfd file format, except for
5869 raw binary. To restore a raw binary file you must use the optional argument
5870 @var{binary} after the filename.
5872 If @var{bias} is non-zero, its value will be added to the addresses
5873 contained in the file. Binary files always start at address zero, so
5874 they will be restored at address @var{bias}. Other bfd files have
5875 a built-in location; they will be restored at offset @var{bias}
5878 If @var{start} and/or @var{end} are non-zero, then only data between
5879 file offset @var{start} and file offset @var{end} will be restored.
5880 These offsets are relative to the addresses in the file, before
5881 the @var{bias} argument is applied.
5885 @node Character Sets
5886 @section Character Sets
5887 @cindex character sets
5889 @cindex translating between character sets
5890 @cindex host character set
5891 @cindex target character set
5893 If the program you are debugging uses a different character set to
5894 represent characters and strings than the one @value{GDBN} uses itself,
5895 @value{GDBN} can automatically translate between the character sets for
5896 you. The character set @value{GDBN} uses we call the @dfn{host
5897 character set}; the one the inferior program uses we call the
5898 @dfn{target character set}.
5900 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5901 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5902 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5903 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5904 then the host character set is Latin-1, and the target character set is
5905 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5906 target-charset ebcdic-us}, then @value{GDBN} translates between
5907 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5908 character and string literals in expressions.
5910 @value{GDBN} has no way to automatically recognize which character set
5911 the inferior program uses; you must tell it, using the @code{set
5912 target-charset} command, described below.
5914 Here are the commands for controlling @value{GDBN}'s character set
5918 @item set target-charset @var{charset}
5919 @kindex set target-charset
5920 Set the current target character set to @var{charset}. We list the
5921 character set names @value{GDBN} recognizes below, but if you invoke the
5922 @code{set target-charset} command with no argument, @value{GDBN} lists
5923 the character sets it supports.
5927 @item set host-charset @var{charset}
5928 @kindex set host-charset
5929 Set the current host character set to @var{charset}.
5931 By default, @value{GDBN} uses a host character set appropriate to the
5932 system it is running on; you can override that default using the
5933 @code{set host-charset} command.
5935 @value{GDBN} can only use certain character sets as its host character
5936 set. We list the character set names @value{GDBN} recognizes below, and
5937 indicate which can be host character sets, but if you invoke the
5938 @code{set host-charset} command with no argument, @value{GDBN} lists the
5939 character sets it supports, placing an asterisk (@samp{*}) after those
5940 it can use as a host character set.
5942 @item set charset @var{charset}
5944 Set the current host and target character sets to @var{charset}. If you
5945 invoke the @code{set charset} command with no argument, it lists the
5946 character sets it supports. @value{GDBN} can only use certain character
5947 sets as its host character set; it marks those in the list with an
5948 asterisk (@samp{*}).
5951 @itemx show host-charset
5952 @itemx show target-charset
5953 @kindex show charset
5954 @kindex show host-charset
5955 @kindex show target-charset
5956 Show the current host and target charsets. The @code{show host-charset}
5957 and @code{show target-charset} commands are synonyms for @code{show
5962 @value{GDBN} currently includes support for the following character
5968 @cindex ASCII character set
5969 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
5973 @cindex ISO 8859-1 character set
5974 @cindex ISO Latin 1 character set
5975 The ISO Latin 1 character set. This extends ASCII with accented
5976 characters needed for French, German, and Spanish. @value{GDBN} can use
5977 this as its host character set.
5981 @cindex EBCDIC character set
5982 @cindex IBM1047 character set
5983 Variants of the @sc{ebcdic} character set, used on some of IBM's
5984 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
5985 @value{GDBN} cannot use these as its host character set.
5989 Note that these are all single-byte character sets. More work inside
5990 GDB is needed to support multi-byte or variable-width character
5991 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
5993 Here is an example of @value{GDBN}'s character set support in action.
5994 Assume that the following source code has been placed in the file
5995 @file{charset-test.c}:
6001 = @{72, 101, 108, 108, 111, 44, 32, 119,
6002 111, 114, 108, 100, 33, 10, 0@};
6003 char ibm1047_hello[]
6004 = @{200, 133, 147, 147, 150, 107, 64, 166,
6005 150, 153, 147, 132, 90, 37, 0@};
6009 printf ("Hello, world!\n");
6013 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6014 containing the string @samp{Hello, world!} followed by a newline,
6015 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6017 We compile the program, and invoke the debugger on it:
6020 $ gcc -g charset-test.c -o charset-test
6021 $ gdb -nw charset-test
6022 GNU gdb 2001-12-19-cvs
6023 Copyright 2001 Free Software Foundation, Inc.
6028 We can use the @code{show charset} command to see what character sets
6029 @value{GDBN} is currently using to interpret and display characters and
6034 The current host and target character set is `iso-8859-1'.
6038 For the sake of printing this manual, let's use @sc{ascii} as our
6039 initial character set:
6041 (gdb) set charset ascii
6043 The current host and target character set is `ascii'.
6047 Let's assume that @sc{ascii} is indeed the correct character set for our
6048 host system --- in other words, let's assume that if @value{GDBN} prints
6049 characters using the @sc{ascii} character set, our terminal will display
6050 them properly. Since our current target character set is also
6051 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6054 (gdb) print ascii_hello
6055 $1 = 0x401698 "Hello, world!\n"
6056 (gdb) print ascii_hello[0]
6061 @value{GDBN} uses the target character set for character and string
6062 literals you use in expressions:
6070 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6073 @value{GDBN} relies on the user to tell it which character set the
6074 target program uses. If we print @code{ibm1047_hello} while our target
6075 character set is still @sc{ascii}, we get jibberish:
6078 (gdb) print ibm1047_hello
6079 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6080 (gdb) print ibm1047_hello[0]
6085 If we invoke the @code{set target-charset} command without an argument,
6086 @value{GDBN} tells us the character sets it supports:
6089 (gdb) set target-charset
6090 Valid character sets are:
6095 * - can be used as a host character set
6098 We can select @sc{ibm1047} as our target character set, and examine the
6099 program's strings again. Now the @sc{ascii} string is wrong, but
6100 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6101 target character set, @sc{ibm1047}, to the host character set,
6102 @sc{ascii}, and they display correctly:
6105 (gdb) set target-charset ibm1047
6107 The current host character set is `ascii'.
6108 The current target character set is `ibm1047'.
6109 (gdb) print ascii_hello
6110 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6111 (gdb) print ascii_hello[0]
6113 (gdb) print ibm1047_hello
6114 $8 = 0x4016a8 "Hello, world!\n"
6115 (gdb) print ibm1047_hello[0]
6120 As above, @value{GDBN} uses the target character set for character and
6121 string literals you use in expressions:
6129 The IBM1047 character set uses the number 78 to encode the @samp{+}
6134 @chapter C Preprocessor Macros
6136 Some languages, such as C and C++, provide a way to define and invoke
6137 ``preprocessor macros'' which expand into strings of tokens.
6138 @value{GDBN} can evaluate expressions containing macro invocations, show
6139 the result of macro expansion, and show a macro's definition, including
6140 where it was defined.
6142 You may need to compile your program specially to provide @value{GDBN}
6143 with information about preprocessor macros. Most compilers do not
6144 include macros in their debugging information, even when you compile
6145 with the @option{-g} flag. @xref{Compilation}.
6147 A program may define a macro at one point, remove that definition later,
6148 and then provide a different definition after that. Thus, at different
6149 points in the program, a macro may have different definitions, or have
6150 no definition at all. If there is a current stack frame, @value{GDBN}
6151 uses the macros in scope at that frame's source code line. Otherwise,
6152 @value{GDBN} uses the macros in scope at the current listing location;
6155 At the moment, @value{GDBN} does not support the @code{##}
6156 token-splicing operator, the @code{#} stringification operator, or
6157 variable-arity macros.
6159 Whenever @value{GDBN} evaluates an expression, it always expands any
6160 macro invocations present in the expression. @value{GDBN} also provides
6161 the following commands for working with macros explicitly.
6165 @kindex macro expand
6166 @cindex macro expansion, showing the results of preprocessor
6167 @cindex preprocessor macro expansion, showing the results of
6168 @cindex expanding preprocessor macros
6169 @item macro expand @var{expression}
6170 @itemx macro exp @var{expression}
6171 Show the results of expanding all preprocessor macro invocations in
6172 @var{expression}. Since @value{GDBN} simply expands macros, but does
6173 not parse the result, @var{expression} need not be a valid expression;
6174 it can be any string of tokens.
6176 @kindex macro expand-once
6177 @item macro expand-once @var{expression}
6178 @itemx macro exp1 @var{expression}
6179 @i{(This command is not yet implemented.)} Show the results of
6180 expanding those preprocessor macro invocations that appear explicitly in
6181 @var{expression}. Macro invocations appearing in that expansion are
6182 left unchanged. This command allows you to see the effect of a
6183 particular macro more clearly, without being confused by further
6184 expansions. Since @value{GDBN} simply expands macros, but does not
6185 parse the result, @var{expression} need not be a valid expression; it
6186 can be any string of tokens.
6189 @cindex macro definition, showing
6190 @cindex definition, showing a macro's
6191 @item info macro @var{macro}
6192 Show the definition of the macro named @var{macro}, and describe the
6193 source location where that definition was established.
6195 @kindex macro define
6196 @cindex user-defined macros
6197 @cindex defining macros interactively
6198 @cindex macros, user-defined
6199 @item macro define @var{macro} @var{replacement-list}
6200 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6201 @i{(This command is not yet implemented.)} Introduce a definition for a
6202 preprocessor macro named @var{macro}, invocations of which are replaced
6203 by the tokens given in @var{replacement-list}. The first form of this
6204 command defines an ``object-like'' macro, which takes no arguments; the
6205 second form defines a ``function-like'' macro, which takes the arguments
6206 given in @var{arglist}.
6208 A definition introduced by this command is in scope in every expression
6209 evaluated in @value{GDBN}, until it is removed with the @command{macro
6210 undef} command, described below. The definition overrides all
6211 definitions for @var{macro} present in the program being debugged, as
6212 well as any previous user-supplied definition.
6215 @item macro undef @var{macro}
6216 @i{(This command is not yet implemented.)} Remove any user-supplied
6217 definition for the macro named @var{macro}. This command only affects
6218 definitions provided with the @command{macro define} command, described
6219 above; it cannot remove definitions present in the program being
6224 @cindex macros, example of debugging with
6225 Here is a transcript showing the above commands in action. First, we
6226 show our source files:
6234 #define ADD(x) (M + x)
6239 printf ("Hello, world!\n");
6241 printf ("We're so creative.\n");
6243 printf ("Goodbye, world!\n");
6250 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6251 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6252 compiler includes information about preprocessor macros in the debugging
6256 $ gcc -gdwarf-2 -g3 sample.c -o sample
6260 Now, we start @value{GDBN} on our sample program:
6264 GNU gdb 2002-05-06-cvs
6265 Copyright 2002 Free Software Foundation, Inc.
6266 GDB is free software, @dots{}
6270 We can expand macros and examine their definitions, even when the
6271 program is not running. @value{GDBN} uses the current listing position
6272 to decide which macro definitions are in scope:
6278 5 #define ADD(x) (M + x)
6283 10 printf ("Hello, world!\n");
6285 12 printf ("We're so creative.\n");
6286 (gdb) info macro ADD
6287 Defined at /home/jimb/gdb/macros/play/sample.c:5
6288 #define ADD(x) (M + x)
6290 Defined at /home/jimb/gdb/macros/play/sample.h:1
6291 included at /home/jimb/gdb/macros/play/sample.c:2
6293 (gdb) macro expand ADD(1)
6294 expands to: (42 + 1)
6295 (gdb) macro expand-once ADD(1)
6296 expands to: once (M + 1)
6300 In the example above, note that @command{macro expand-once} expands only
6301 the macro invocation explicit in the original text --- the invocation of
6302 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6303 which was introduced by @code{ADD}.
6305 Once the program is running, GDB uses the macro definitions in force at
6306 the source line of the current stack frame:
6310 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6312 Starting program: /home/jimb/gdb/macros/play/sample
6314 Breakpoint 1, main () at sample.c:10
6315 10 printf ("Hello, world!\n");
6319 At line 10, the definition of the macro @code{N} at line 9 is in force:
6323 Defined at /home/jimb/gdb/macros/play/sample.c:9
6325 (gdb) macro expand N Q M
6332 As we step over directives that remove @code{N}'s definition, and then
6333 give it a new definition, @value{GDBN} finds the definition (or lack
6334 thereof) in force at each point:
6339 12 printf ("We're so creative.\n");
6341 The symbol `N' has no definition as a C/C++ preprocessor macro
6342 at /home/jimb/gdb/macros/play/sample.c:12
6345 14 printf ("Goodbye, world!\n");
6347 Defined at /home/jimb/gdb/macros/play/sample.c:13
6349 (gdb) macro expand N Q M
6350 expands to: 1729 < 42
6358 @chapter Tracepoints
6359 @c This chapter is based on the documentation written by Michael
6360 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6363 In some applications, it is not feasible for the debugger to interrupt
6364 the program's execution long enough for the developer to learn
6365 anything helpful about its behavior. If the program's correctness
6366 depends on its real-time behavior, delays introduced by a debugger
6367 might cause the program to change its behavior drastically, or perhaps
6368 fail, even when the code itself is correct. It is useful to be able
6369 to observe the program's behavior without interrupting it.
6371 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6372 specify locations in the program, called @dfn{tracepoints}, and
6373 arbitrary expressions to evaluate when those tracepoints are reached.
6374 Later, using the @code{tfind} command, you can examine the values
6375 those expressions had when the program hit the tracepoints. The
6376 expressions may also denote objects in memory---structures or arrays,
6377 for example---whose values @value{GDBN} should record; while visiting
6378 a particular tracepoint, you may inspect those objects as if they were
6379 in memory at that moment. However, because @value{GDBN} records these
6380 values without interacting with you, it can do so quickly and
6381 unobtrusively, hopefully not disturbing the program's behavior.
6383 The tracepoint facility is currently available only for remote
6384 targets. @xref{Targets}. In addition, your remote target must know how
6385 to collect trace data. This functionality is implemented in the remote
6386 stub; however, none of the stubs distributed with @value{GDBN} support
6387 tracepoints as of this writing.
6389 This chapter describes the tracepoint commands and features.
6393 * Analyze Collected Data::
6394 * Tracepoint Variables::
6397 @node Set Tracepoints
6398 @section Commands to Set Tracepoints
6400 Before running such a @dfn{trace experiment}, an arbitrary number of
6401 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6402 tracepoint has a number assigned to it by @value{GDBN}. Like with
6403 breakpoints, tracepoint numbers are successive integers starting from
6404 one. Many of the commands associated with tracepoints take the
6405 tracepoint number as their argument, to identify which tracepoint to
6408 For each tracepoint, you can specify, in advance, some arbitrary set
6409 of data that you want the target to collect in the trace buffer when
6410 it hits that tracepoint. The collected data can include registers,
6411 local variables, or global data. Later, you can use @value{GDBN}
6412 commands to examine the values these data had at the time the
6415 This section describes commands to set tracepoints and associated
6416 conditions and actions.
6419 * Create and Delete Tracepoints::
6420 * Enable and Disable Tracepoints::
6421 * Tracepoint Passcounts::
6422 * Tracepoint Actions::
6423 * Listing Tracepoints::
6424 * Starting and Stopping Trace Experiment::
6427 @node Create and Delete Tracepoints
6428 @subsection Create and Delete Tracepoints
6431 @cindex set tracepoint
6434 The @code{trace} command is very similar to the @code{break} command.
6435 Its argument can be a source line, a function name, or an address in
6436 the target program. @xref{Set Breaks}. The @code{trace} command
6437 defines a tracepoint, which is a point in the target program where the
6438 debugger will briefly stop, collect some data, and then allow the
6439 program to continue. Setting a tracepoint or changing its commands
6440 doesn't take effect until the next @code{tstart} command; thus, you
6441 cannot change the tracepoint attributes once a trace experiment is
6444 Here are some examples of using the @code{trace} command:
6447 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6449 (@value{GDBP}) @b{trace +2} // 2 lines forward
6451 (@value{GDBP}) @b{trace my_function} // first source line of function
6453 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6455 (@value{GDBP}) @b{trace *0x2117c4} // an address
6459 You can abbreviate @code{trace} as @code{tr}.
6462 @cindex last tracepoint number
6463 @cindex recent tracepoint number
6464 @cindex tracepoint number
6465 The convenience variable @code{$tpnum} records the tracepoint number
6466 of the most recently set tracepoint.
6468 @kindex delete tracepoint
6469 @cindex tracepoint deletion
6470 @item delete tracepoint @r{[}@var{num}@r{]}
6471 Permanently delete one or more tracepoints. With no argument, the
6472 default is to delete all tracepoints.
6477 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6479 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6483 You can abbreviate this command as @code{del tr}.
6486 @node Enable and Disable Tracepoints
6487 @subsection Enable and Disable Tracepoints
6490 @kindex disable tracepoint
6491 @item disable tracepoint @r{[}@var{num}@r{]}
6492 Disable tracepoint @var{num}, or all tracepoints if no argument
6493 @var{num} is given. A disabled tracepoint will have no effect during
6494 the next trace experiment, but it is not forgotten. You can re-enable
6495 a disabled tracepoint using the @code{enable tracepoint} command.
6497 @kindex enable tracepoint
6498 @item enable tracepoint @r{[}@var{num}@r{]}
6499 Enable tracepoint @var{num}, or all tracepoints. The enabled
6500 tracepoints will become effective the next time a trace experiment is
6504 @node Tracepoint Passcounts
6505 @subsection Tracepoint Passcounts
6509 @cindex tracepoint pass count
6510 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6511 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6512 automatically stop a trace experiment. If a tracepoint's passcount is
6513 @var{n}, then the trace experiment will be automatically stopped on
6514 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6515 @var{num} is not specified, the @code{passcount} command sets the
6516 passcount of the most recently defined tracepoint. If no passcount is
6517 given, the trace experiment will run until stopped explicitly by the
6523 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6524 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6526 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6527 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6528 (@value{GDBP}) @b{trace foo}
6529 (@value{GDBP}) @b{pass 3}
6530 (@value{GDBP}) @b{trace bar}
6531 (@value{GDBP}) @b{pass 2}
6532 (@value{GDBP}) @b{trace baz}
6533 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6534 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6535 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6536 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6540 @node Tracepoint Actions
6541 @subsection Tracepoint Action Lists
6545 @cindex tracepoint actions
6546 @item actions @r{[}@var{num}@r{]}
6547 This command will prompt for a list of actions to be taken when the
6548 tracepoint is hit. If the tracepoint number @var{num} is not
6549 specified, this command sets the actions for the one that was most
6550 recently defined (so that you can define a tracepoint and then say
6551 @code{actions} without bothering about its number). You specify the
6552 actions themselves on the following lines, one action at a time, and
6553 terminate the actions list with a line containing just @code{end}. So
6554 far, the only defined actions are @code{collect} and
6555 @code{while-stepping}.
6557 @cindex remove actions from a tracepoint
6558 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6559 and follow it immediately with @samp{end}.
6562 (@value{GDBP}) @b{collect @var{data}} // collect some data
6564 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6566 (@value{GDBP}) @b{end} // signals the end of actions.
6569 In the following example, the action list begins with @code{collect}
6570 commands indicating the things to be collected when the tracepoint is
6571 hit. Then, in order to single-step and collect additional data
6572 following the tracepoint, a @code{while-stepping} command is used,
6573 followed by the list of things to be collected while stepping. The
6574 @code{while-stepping} command is terminated by its own separate
6575 @code{end} command. Lastly, the action list is terminated by an
6579 (@value{GDBP}) @b{trace foo}
6580 (@value{GDBP}) @b{actions}
6581 Enter actions for tracepoint 1, one per line:
6590 @kindex collect @r{(tracepoints)}
6591 @item collect @var{expr1}, @var{expr2}, @dots{}
6592 Collect values of the given expressions when the tracepoint is hit.
6593 This command accepts a comma-separated list of any valid expressions.
6594 In addition to global, static, or local variables, the following
6595 special arguments are supported:
6599 collect all registers
6602 collect all function arguments
6605 collect all local variables.
6608 You can give several consecutive @code{collect} commands, each one
6609 with a single argument, or one @code{collect} command with several
6610 arguments separated by commas: the effect is the same.
6612 The command @code{info scope} (@pxref{Symbols, info scope}) is
6613 particularly useful for figuring out what data to collect.
6615 @kindex while-stepping @r{(tracepoints)}
6616 @item while-stepping @var{n}
6617 Perform @var{n} single-step traces after the tracepoint, collecting
6618 new data at each step. The @code{while-stepping} command is
6619 followed by the list of what to collect while stepping (followed by
6620 its own @code{end} command):
6624 > collect $regs, myglobal
6630 You may abbreviate @code{while-stepping} as @code{ws} or
6634 @node Listing Tracepoints
6635 @subsection Listing Tracepoints
6638 @kindex info tracepoints
6639 @cindex information about tracepoints
6640 @item info tracepoints @r{[}@var{num}@r{]}
6641 Display information about the tracepoint @var{num}. If you don't specify
6642 a tracepoint number, displays information about all the tracepoints
6643 defined so far. For each tracepoint, the following information is
6650 whether it is enabled or disabled
6654 its passcount as given by the @code{passcount @var{n}} command
6656 its step count as given by the @code{while-stepping @var{n}} command
6658 where in the source files is the tracepoint set
6660 its action list as given by the @code{actions} command
6664 (@value{GDBP}) @b{info trace}
6665 Num Enb Address PassC StepC What
6666 1 y 0x002117c4 0 0 <gdb_asm>
6667 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6668 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6673 This command can be abbreviated @code{info tp}.
6676 @node Starting and Stopping Trace Experiment
6677 @subsection Starting and Stopping Trace Experiment
6681 @cindex start a new trace experiment
6682 @cindex collected data discarded
6684 This command takes no arguments. It starts the trace experiment, and
6685 begins collecting data. This has the side effect of discarding all
6686 the data collected in the trace buffer during the previous trace
6690 @cindex stop a running trace experiment
6692 This command takes no arguments. It ends the trace experiment, and
6693 stops collecting data.
6695 @strong{Note:} a trace experiment and data collection may stop
6696 automatically if any tracepoint's passcount is reached
6697 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6700 @cindex status of trace data collection
6701 @cindex trace experiment, status of
6703 This command displays the status of the current trace data
6707 Here is an example of the commands we described so far:
6710 (@value{GDBP}) @b{trace gdb_c_test}
6711 (@value{GDBP}) @b{actions}
6712 Enter actions for tracepoint #1, one per line.
6713 > collect $regs,$locals,$args
6718 (@value{GDBP}) @b{tstart}
6719 [time passes @dots{}]
6720 (@value{GDBP}) @b{tstop}
6724 @node Analyze Collected Data
6725 @section Using the collected data
6727 After the tracepoint experiment ends, you use @value{GDBN} commands
6728 for examining the trace data. The basic idea is that each tracepoint
6729 collects a trace @dfn{snapshot} every time it is hit and another
6730 snapshot every time it single-steps. All these snapshots are
6731 consecutively numbered from zero and go into a buffer, and you can
6732 examine them later. The way you examine them is to @dfn{focus} on a
6733 specific trace snapshot. When the remote stub is focused on a trace
6734 snapshot, it will respond to all @value{GDBN} requests for memory and
6735 registers by reading from the buffer which belongs to that snapshot,
6736 rather than from @emph{real} memory or registers of the program being
6737 debugged. This means that @strong{all} @value{GDBN} commands
6738 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6739 behave as if we were currently debugging the program state as it was
6740 when the tracepoint occurred. Any requests for data that are not in
6741 the buffer will fail.
6744 * tfind:: How to select a trace snapshot
6745 * tdump:: How to display all data for a snapshot
6746 * save-tracepoints:: How to save tracepoints for a future run
6750 @subsection @code{tfind @var{n}}
6753 @cindex select trace snapshot
6754 @cindex find trace snapshot
6755 The basic command for selecting a trace snapshot from the buffer is
6756 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6757 counting from zero. If no argument @var{n} is given, the next
6758 snapshot is selected.
6760 Here are the various forms of using the @code{tfind} command.
6764 Find the first snapshot in the buffer. This is a synonym for
6765 @code{tfind 0} (since 0 is the number of the first snapshot).
6768 Stop debugging trace snapshots, resume @emph{live} debugging.
6771 Same as @samp{tfind none}.
6774 No argument means find the next trace snapshot.
6777 Find the previous trace snapshot before the current one. This permits
6778 retracing earlier steps.
6780 @item tfind tracepoint @var{num}
6781 Find the next snapshot associated with tracepoint @var{num}. Search
6782 proceeds forward from the last examined trace snapshot. If no
6783 argument @var{num} is given, it means find the next snapshot collected
6784 for the same tracepoint as the current snapshot.
6786 @item tfind pc @var{addr}
6787 Find the next snapshot associated with the value @var{addr} of the
6788 program counter. Search proceeds forward from the last examined trace
6789 snapshot. If no argument @var{addr} is given, it means find the next
6790 snapshot with the same value of PC as the current snapshot.
6792 @item tfind outside @var{addr1}, @var{addr2}
6793 Find the next snapshot whose PC is outside the given range of
6796 @item tfind range @var{addr1}, @var{addr2}
6797 Find the next snapshot whose PC is between @var{addr1} and
6798 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6800 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6801 Find the next snapshot associated with the source line @var{n}. If
6802 the optional argument @var{file} is given, refer to line @var{n} in
6803 that source file. Search proceeds forward from the last examined
6804 trace snapshot. If no argument @var{n} is given, it means find the
6805 next line other than the one currently being examined; thus saying
6806 @code{tfind line} repeatedly can appear to have the same effect as
6807 stepping from line to line in a @emph{live} debugging session.
6810 The default arguments for the @code{tfind} commands are specifically
6811 designed to make it easy to scan through the trace buffer. For
6812 instance, @code{tfind} with no argument selects the next trace
6813 snapshot, and @code{tfind -} with no argument selects the previous
6814 trace snapshot. So, by giving one @code{tfind} command, and then
6815 simply hitting @key{RET} repeatedly you can examine all the trace
6816 snapshots in order. Or, by saying @code{tfind -} and then hitting
6817 @key{RET} repeatedly you can examine the snapshots in reverse order.
6818 The @code{tfind line} command with no argument selects the snapshot
6819 for the next source line executed. The @code{tfind pc} command with
6820 no argument selects the next snapshot with the same program counter
6821 (PC) as the current frame. The @code{tfind tracepoint} command with
6822 no argument selects the next trace snapshot collected by the same
6823 tracepoint as the current one.
6825 In addition to letting you scan through the trace buffer manually,
6826 these commands make it easy to construct @value{GDBN} scripts that
6827 scan through the trace buffer and print out whatever collected data
6828 you are interested in. Thus, if we want to examine the PC, FP, and SP
6829 registers from each trace frame in the buffer, we can say this:
6832 (@value{GDBP}) @b{tfind start}
6833 (@value{GDBP}) @b{while ($trace_frame != -1)}
6834 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6835 $trace_frame, $pc, $sp, $fp
6839 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6840 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6841 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6842 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6843 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6844 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6845 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6846 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6847 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6848 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6849 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6852 Or, if we want to examine the variable @code{X} at each source line in
6856 (@value{GDBP}) @b{tfind start}
6857 (@value{GDBP}) @b{while ($trace_frame != -1)}
6858 > printf "Frame %d, X == %d\n", $trace_frame, X
6868 @subsection @code{tdump}
6870 @cindex dump all data collected at tracepoint
6871 @cindex tracepoint data, display
6873 This command takes no arguments. It prints all the data collected at
6874 the current trace snapshot.
6877 (@value{GDBP}) @b{trace 444}
6878 (@value{GDBP}) @b{actions}
6879 Enter actions for tracepoint #2, one per line:
6880 > collect $regs, $locals, $args, gdb_long_test
6883 (@value{GDBP}) @b{tstart}
6885 (@value{GDBP}) @b{tfind line 444}
6886 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6888 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6890 (@value{GDBP}) @b{tdump}
6891 Data collected at tracepoint 2, trace frame 1:
6892 d0 0xc4aa0085 -995491707
6896 d4 0x71aea3d 119204413
6901 a1 0x3000668 50333288
6904 a4 0x3000698 50333336
6906 fp 0x30bf3c 0x30bf3c
6907 sp 0x30bf34 0x30bf34
6909 pc 0x20b2c8 0x20b2c8
6913 p = 0x20e5b4 "gdb-test"
6920 gdb_long_test = 17 '\021'
6925 @node save-tracepoints
6926 @subsection @code{save-tracepoints @var{filename}}
6927 @kindex save-tracepoints
6928 @cindex save tracepoints for future sessions
6930 This command saves all current tracepoint definitions together with
6931 their actions and passcounts, into a file @file{@var{filename}}
6932 suitable for use in a later debugging session. To read the saved
6933 tracepoint definitions, use the @code{source} command (@pxref{Command
6936 @node Tracepoint Variables
6937 @section Convenience Variables for Tracepoints
6938 @cindex tracepoint variables
6939 @cindex convenience variables for tracepoints
6942 @vindex $trace_frame
6943 @item (int) $trace_frame
6944 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6945 snapshot is selected.
6948 @item (int) $tracepoint
6949 The tracepoint for the current trace snapshot.
6952 @item (int) $trace_line
6953 The line number for the current trace snapshot.
6956 @item (char []) $trace_file
6957 The source file for the current trace snapshot.
6960 @item (char []) $trace_func
6961 The name of the function containing @code{$tracepoint}.
6964 Note: @code{$trace_file} is not suitable for use in @code{printf},
6965 use @code{output} instead.
6967 Here's a simple example of using these convenience variables for
6968 stepping through all the trace snapshots and printing some of their
6972 (@value{GDBP}) @b{tfind start}
6974 (@value{GDBP}) @b{while $trace_frame != -1}
6975 > output $trace_file
6976 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
6982 @chapter Debugging Programs That Use Overlays
6985 If your program is too large to fit completely in your target system's
6986 memory, you can sometimes use @dfn{overlays} to work around this
6987 problem. @value{GDBN} provides some support for debugging programs that
6991 * How Overlays Work:: A general explanation of overlays.
6992 * Overlay Commands:: Managing overlays in @value{GDBN}.
6993 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
6994 mapped by asking the inferior.
6995 * Overlay Sample Program:: A sample program using overlays.
6998 @node How Overlays Work
6999 @section How Overlays Work
7000 @cindex mapped overlays
7001 @cindex unmapped overlays
7002 @cindex load address, overlay's
7003 @cindex mapped address
7004 @cindex overlay area
7006 Suppose you have a computer whose instruction address space is only 64
7007 kilobytes long, but which has much more memory which can be accessed by
7008 other means: special instructions, segment registers, or memory
7009 management hardware, for example. Suppose further that you want to
7010 adapt a program which is larger than 64 kilobytes to run on this system.
7012 One solution is to identify modules of your program which are relatively
7013 independent, and need not call each other directly; call these modules
7014 @dfn{overlays}. Separate the overlays from the main program, and place
7015 their machine code in the larger memory. Place your main program in
7016 instruction memory, but leave at least enough space there to hold the
7017 largest overlay as well.
7019 Now, to call a function located in an overlay, you must first copy that
7020 overlay's machine code from the large memory into the space set aside
7021 for it in the instruction memory, and then jump to its entry point
7024 @c NB: In the below the mapped area's size is greater or equal to the
7025 @c size of all overlays. This is intentional to remind the developer
7026 @c that overlays don't necessarily need to be the same size.
7030 Data Instruction Larger
7031 Address Space Address Space Address Space
7032 +-----------+ +-----------+ +-----------+
7034 +-----------+ +-----------+ +-----------+<-- overlay 1
7035 | program | | main | .----| overlay 1 | load address
7036 | variables | | program | | +-----------+
7037 | and heap | | | | | |
7038 +-----------+ | | | +-----------+<-- overlay 2
7039 | | +-----------+ | | | load address
7040 +-----------+ | | | .-| overlay 2 |
7042 mapped --->+-----------+ | | +-----------+
7044 | overlay | <-' | | |
7045 | area | <---' +-----------+<-- overlay 3
7046 | | <---. | | load address
7047 +-----------+ `--| overlay 3 |
7054 @anchor{A code overlay}A code overlay
7058 The diagram (@pxref{A code overlay}) shows a system with separate data
7059 and instruction address spaces. To map an overlay, the program copies
7060 its code from the larger address space to the instruction address space.
7061 Since the overlays shown here all use the same mapped address, only one
7062 may be mapped at a time. For a system with a single address space for
7063 data and instructions, the diagram would be similar, except that the
7064 program variables and heap would share an address space with the main
7065 program and the overlay area.
7067 An overlay loaded into instruction memory and ready for use is called a
7068 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7069 instruction memory. An overlay not present (or only partially present)
7070 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7071 is its address in the larger memory. The mapped address is also called
7072 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7073 called the @dfn{load memory address}, or @dfn{LMA}.
7075 Unfortunately, overlays are not a completely transparent way to adapt a
7076 program to limited instruction memory. They introduce a new set of
7077 global constraints you must keep in mind as you design your program:
7082 Before calling or returning to a function in an overlay, your program
7083 must make sure that overlay is actually mapped. Otherwise, the call or
7084 return will transfer control to the right address, but in the wrong
7085 overlay, and your program will probably crash.
7088 If the process of mapping an overlay is expensive on your system, you
7089 will need to choose your overlays carefully to minimize their effect on
7090 your program's performance.
7093 The executable file you load onto your system must contain each
7094 overlay's instructions, appearing at the overlay's load address, not its
7095 mapped address. However, each overlay's instructions must be relocated
7096 and its symbols defined as if the overlay were at its mapped address.
7097 You can use GNU linker scripts to specify different load and relocation
7098 addresses for pieces of your program; see @ref{Overlay Description,,,
7099 ld.info, Using ld: the GNU linker}.
7102 The procedure for loading executable files onto your system must be able
7103 to load their contents into the larger address space as well as the
7104 instruction and data spaces.
7108 The overlay system described above is rather simple, and could be
7109 improved in many ways:
7114 If your system has suitable bank switch registers or memory management
7115 hardware, you could use those facilities to make an overlay's load area
7116 contents simply appear at their mapped address in instruction space.
7117 This would probably be faster than copying the overlay to its mapped
7118 area in the usual way.
7121 If your overlays are small enough, you could set aside more than one
7122 overlay area, and have more than one overlay mapped at a time.
7125 You can use overlays to manage data, as well as instructions. In
7126 general, data overlays are even less transparent to your design than
7127 code overlays: whereas code overlays only require care when you call or
7128 return to functions, data overlays require care every time you access
7129 the data. Also, if you change the contents of a data overlay, you
7130 must copy its contents back out to its load address before you can copy a
7131 different data overlay into the same mapped area.
7136 @node Overlay Commands
7137 @section Overlay Commands
7139 To use @value{GDBN}'s overlay support, each overlay in your program must
7140 correspond to a separate section of the executable file. The section's
7141 virtual memory address and load memory address must be the overlay's
7142 mapped and load addresses. Identifying overlays with sections allows
7143 @value{GDBN} to determine the appropriate address of a function or
7144 variable, depending on whether the overlay is mapped or not.
7146 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7147 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7152 Disable @value{GDBN}'s overlay support. When overlay support is
7153 disabled, @value{GDBN} assumes that all functions and variables are
7154 always present at their mapped addresses. By default, @value{GDBN}'s
7155 overlay support is disabled.
7157 @item overlay manual
7158 @kindex overlay manual
7159 @cindex manual overlay debugging
7160 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7161 relies on you to tell it which overlays are mapped, and which are not,
7162 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7163 commands described below.
7165 @item overlay map-overlay @var{overlay}
7166 @itemx overlay map @var{overlay}
7167 @kindex overlay map-overlay
7168 @cindex map an overlay
7169 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7170 be the name of the object file section containing the overlay. When an
7171 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7172 functions and variables at their mapped addresses. @value{GDBN} assumes
7173 that any other overlays whose mapped ranges overlap that of
7174 @var{overlay} are now unmapped.
7176 @item overlay unmap-overlay @var{overlay}
7177 @itemx overlay unmap @var{overlay}
7178 @kindex overlay unmap-overlay
7179 @cindex unmap an overlay
7180 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7181 must be the name of the object file section containing the overlay.
7182 When an overlay is unmapped, @value{GDBN} assumes it can find the
7183 overlay's functions and variables at their load addresses.
7186 @kindex overlay auto
7187 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7188 consults a data structure the overlay manager maintains in the inferior
7189 to see which overlays are mapped. For details, see @ref{Automatic
7192 @item overlay load-target
7194 @kindex overlay load-target
7195 @cindex reloading the overlay table
7196 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7197 re-reads the table @value{GDBN} automatically each time the inferior
7198 stops, so this command should only be necessary if you have changed the
7199 overlay mapping yourself using @value{GDBN}. This command is only
7200 useful when using automatic overlay debugging.
7202 @item overlay list-overlays
7204 @cindex listing mapped overlays
7205 Display a list of the overlays currently mapped, along with their mapped
7206 addresses, load addresses, and sizes.
7210 Normally, when @value{GDBN} prints a code address, it includes the name
7211 of the function the address falls in:
7215 $3 = @{int ()@} 0x11a0 <main>
7218 When overlay debugging is enabled, @value{GDBN} recognizes code in
7219 unmapped overlays, and prints the names of unmapped functions with
7220 asterisks around them. For example, if @code{foo} is a function in an
7221 unmapped overlay, @value{GDBN} prints it this way:
7225 No sections are mapped.
7227 $5 = @{int (int)@} 0x100000 <*foo*>
7230 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7235 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7236 mapped at 0x1016 - 0x104a
7238 $6 = @{int (int)@} 0x1016 <foo>
7241 When overlay debugging is enabled, @value{GDBN} can find the correct
7242 address for functions and variables in an overlay, whether or not the
7243 overlay is mapped. This allows most @value{GDBN} commands, like
7244 @code{break} and @code{disassemble}, to work normally, even on unmapped
7245 code. However, @value{GDBN}'s breakpoint support has some limitations:
7249 @cindex breakpoints in overlays
7250 @cindex overlays, setting breakpoints in
7251 You can set breakpoints in functions in unmapped overlays, as long as
7252 @value{GDBN} can write to the overlay at its load address.
7254 @value{GDBN} can not set hardware or simulator-based breakpoints in
7255 unmapped overlays. However, if you set a breakpoint at the end of your
7256 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7257 you are using manual overlay management), @value{GDBN} will re-set its
7258 breakpoints properly.
7262 @node Automatic Overlay Debugging
7263 @section Automatic Overlay Debugging
7264 @cindex automatic overlay debugging
7266 @value{GDBN} can automatically track which overlays are mapped and which
7267 are not, given some simple co-operation from the overlay manager in the
7268 inferior. If you enable automatic overlay debugging with the
7269 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7270 looks in the inferior's memory for certain variables describing the
7271 current state of the overlays.
7273 Here are the variables your overlay manager must define to support
7274 @value{GDBN}'s automatic overlay debugging:
7278 @item @code{_ovly_table}:
7279 This variable must be an array of the following structures:
7284 /* The overlay's mapped address. */
7287 /* The size of the overlay, in bytes. */
7290 /* The overlay's load address. */
7293 /* Non-zero if the overlay is currently mapped;
7295 unsigned long mapped;
7299 @item @code{_novlys}:
7300 This variable must be a four-byte signed integer, holding the total
7301 number of elements in @code{_ovly_table}.
7305 To decide whether a particular overlay is mapped or not, @value{GDBN}
7306 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7307 @code{lma} members equal the VMA and LMA of the overlay's section in the
7308 executable file. When @value{GDBN} finds a matching entry, it consults
7309 the entry's @code{mapped} member to determine whether the overlay is
7312 In addition, your overlay manager may define a function called
7313 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7314 will silently set a breakpoint there. If the overlay manager then
7315 calls this function whenever it has changed the overlay table, this
7316 will enable @value{GDBN} to accurately keep track of which overlays
7317 are in program memory, and update any breakpoints that may be set
7318 in overlays. This will allow breakpoints to work even if the
7319 overlays are kept in ROM or other non-writable memory while they
7320 are not being executed.
7322 @node Overlay Sample Program
7323 @section Overlay Sample Program
7324 @cindex overlay example program
7326 When linking a program which uses overlays, you must place the overlays
7327 at their load addresses, while relocating them to run at their mapped
7328 addresses. To do this, you must write a linker script (@pxref{Overlay
7329 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7330 since linker scripts are specific to a particular host system, target
7331 architecture, and target memory layout, this manual cannot provide
7332 portable sample code demonstrating @value{GDBN}'s overlay support.
7334 However, the @value{GDBN} source distribution does contain an overlaid
7335 program, with linker scripts for a few systems, as part of its test
7336 suite. The program consists of the following files from
7337 @file{gdb/testsuite/gdb.base}:
7341 The main program file.
7343 A simple overlay manager, used by @file{overlays.c}.
7348 Overlay modules, loaded and used by @file{overlays.c}.
7351 Linker scripts for linking the test program on the @code{d10v-elf}
7352 and @code{m32r-elf} targets.
7355 You can build the test program using the @code{d10v-elf} GCC
7356 cross-compiler like this:
7359 $ d10v-elf-gcc -g -c overlays.c
7360 $ d10v-elf-gcc -g -c ovlymgr.c
7361 $ d10v-elf-gcc -g -c foo.c
7362 $ d10v-elf-gcc -g -c bar.c
7363 $ d10v-elf-gcc -g -c baz.c
7364 $ d10v-elf-gcc -g -c grbx.c
7365 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7366 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7369 The build process is identical for any other architecture, except that
7370 you must substitute the appropriate compiler and linker script for the
7371 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7375 @chapter Using @value{GDBN} with Different Languages
7378 Although programming languages generally have common aspects, they are
7379 rarely expressed in the same manner. For instance, in ANSI C,
7380 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7381 Modula-2, it is accomplished by @code{p^}. Values can also be
7382 represented (and displayed) differently. Hex numbers in C appear as
7383 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7385 @cindex working language
7386 Language-specific information is built into @value{GDBN} for some languages,
7387 allowing you to express operations like the above in your program's
7388 native language, and allowing @value{GDBN} to output values in a manner
7389 consistent with the syntax of your program's native language. The
7390 language you use to build expressions is called the @dfn{working
7394 * Setting:: Switching between source languages
7395 * Show:: Displaying the language
7396 * Checks:: Type and range checks
7397 * Support:: Supported languages
7401 @section Switching between source languages
7403 There are two ways to control the working language---either have @value{GDBN}
7404 set it automatically, or select it manually yourself. You can use the
7405 @code{set language} command for either purpose. On startup, @value{GDBN}
7406 defaults to setting the language automatically. The working language is
7407 used to determine how expressions you type are interpreted, how values
7410 In addition to the working language, every source file that
7411 @value{GDBN} knows about has its own working language. For some object
7412 file formats, the compiler might indicate which language a particular
7413 source file is in. However, most of the time @value{GDBN} infers the
7414 language from the name of the file. The language of a source file
7415 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7416 show each frame appropriately for its own language. There is no way to
7417 set the language of a source file from within @value{GDBN}, but you can
7418 set the language associated with a filename extension. @xref{Show, ,
7419 Displaying the language}.
7421 This is most commonly a problem when you use a program, such
7422 as @code{cfront} or @code{f2c}, that generates C but is written in
7423 another language. In that case, make the
7424 program use @code{#line} directives in its C output; that way
7425 @value{GDBN} will know the correct language of the source code of the original
7426 program, and will display that source code, not the generated C code.
7429 * Filenames:: Filename extensions and languages.
7430 * Manually:: Setting the working language manually
7431 * Automatically:: Having @value{GDBN} infer the source language
7435 @subsection List of filename extensions and languages
7437 If a source file name ends in one of the following extensions, then
7438 @value{GDBN} infers that its language is the one indicated.
7457 @c OBSOLETE @item .ch
7458 @c OBSOLETE @itemx .c186
7459 @c OBSOLETE @itemx .c286
7460 @c OBSOLETE CHILL source file
7463 Modula-2 source file
7467 Assembler source file. This actually behaves almost like C, but
7468 @value{GDBN} does not skip over function prologues when stepping.
7471 In addition, you may set the language associated with a filename
7472 extension. @xref{Show, , Displaying the language}.
7475 @subsection Setting the working language
7477 If you allow @value{GDBN} to set the language automatically,
7478 expressions are interpreted the same way in your debugging session and
7481 @kindex set language
7482 If you wish, you may set the language manually. To do this, issue the
7483 command @samp{set language @var{lang}}, where @var{lang} is the name of
7485 @code{c} or @code{modula-2}.
7486 For a list of the supported languages, type @samp{set language}.
7488 Setting the language manually prevents @value{GDBN} from updating the working
7489 language automatically. This can lead to confusion if you try
7490 to debug a program when the working language is not the same as the
7491 source language, when an expression is acceptable to both
7492 languages---but means different things. For instance, if the current
7493 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7501 might not have the effect you intended. In C, this means to add
7502 @code{b} and @code{c} and place the result in @code{a}. The result
7503 printed would be the value of @code{a}. In Modula-2, this means to compare
7504 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7507 @subsection Having @value{GDBN} infer the source language
7509 To have @value{GDBN} set the working language automatically, use
7510 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7511 then infers the working language. That is, when your program stops in a
7512 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7513 working language to the language recorded for the function in that
7514 frame. If the language for a frame is unknown (that is, if the function
7515 or block corresponding to the frame was defined in a source file that
7516 does not have a recognized extension), the current working language is
7517 not changed, and @value{GDBN} issues a warning.
7519 This may not seem necessary for most programs, which are written
7520 entirely in one source language. However, program modules and libraries
7521 written in one source language can be used by a main program written in
7522 a different source language. Using @samp{set language auto} in this
7523 case frees you from having to set the working language manually.
7526 @section Displaying the language
7528 The following commands help you find out which language is the
7529 working language, and also what language source files were written in.
7531 @kindex show language
7532 @kindex info frame@r{, show the source language}
7533 @kindex info source@r{, show the source language}
7536 Display the current working language. This is the
7537 language you can use with commands such as @code{print} to
7538 build and compute expressions that may involve variables in your program.
7541 Display the source language for this frame. This language becomes the
7542 working language if you use an identifier from this frame.
7543 @xref{Frame Info, ,Information about a frame}, to identify the other
7544 information listed here.
7547 Display the source language of this source file.
7548 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7549 information listed here.
7552 In unusual circumstances, you may have source files with extensions
7553 not in the standard list. You can then set the extension associated
7554 with a language explicitly:
7556 @kindex set extension-language
7557 @kindex info extensions
7559 @item set extension-language @var{.ext} @var{language}
7560 Set source files with extension @var{.ext} to be assumed to be in
7561 the source language @var{language}.
7563 @item info extensions
7564 List all the filename extensions and the associated languages.
7568 @section Type and range checking
7571 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7572 checking are included, but they do not yet have any effect. This
7573 section documents the intended facilities.
7575 @c FIXME remove warning when type/range code added
7577 Some languages are designed to guard you against making seemingly common
7578 errors through a series of compile- and run-time checks. These include
7579 checking the type of arguments to functions and operators, and making
7580 sure mathematical overflows are caught at run time. Checks such as
7581 these help to ensure a program's correctness once it has been compiled
7582 by eliminating type mismatches, and providing active checks for range
7583 errors when your program is running.
7585 @value{GDBN} can check for conditions like the above if you wish.
7586 Although @value{GDBN} does not check the statements in your program, it
7587 can check expressions entered directly into @value{GDBN} for evaluation via
7588 the @code{print} command, for example. As with the working language,
7589 @value{GDBN} can also decide whether or not to check automatically based on
7590 your program's source language. @xref{Support, ,Supported languages},
7591 for the default settings of supported languages.
7594 * Type Checking:: An overview of type checking
7595 * Range Checking:: An overview of range checking
7598 @cindex type checking
7599 @cindex checks, type
7601 @subsection An overview of type checking
7603 Some languages, such as Modula-2, are strongly typed, meaning that the
7604 arguments to operators and functions have to be of the correct type,
7605 otherwise an error occurs. These checks prevent type mismatch
7606 errors from ever causing any run-time problems. For example,
7614 The second example fails because the @code{CARDINAL} 1 is not
7615 type-compatible with the @code{REAL} 2.3.
7617 For the expressions you use in @value{GDBN} commands, you can tell the
7618 @value{GDBN} type checker to skip checking;
7619 to treat any mismatches as errors and abandon the expression;
7620 or to only issue warnings when type mismatches occur,
7621 but evaluate the expression anyway. When you choose the last of
7622 these, @value{GDBN} evaluates expressions like the second example above, but
7623 also issues a warning.
7625 Even if you turn type checking off, there may be other reasons
7626 related to type that prevent @value{GDBN} from evaluating an expression.
7627 For instance, @value{GDBN} does not know how to add an @code{int} and
7628 a @code{struct foo}. These particular type errors have nothing to do
7629 with the language in use, and usually arise from expressions, such as
7630 the one described above, which make little sense to evaluate anyway.
7632 Each language defines to what degree it is strict about type. For
7633 instance, both Modula-2 and C require the arguments to arithmetical
7634 operators to be numbers. In C, enumerated types and pointers can be
7635 represented as numbers, so that they are valid arguments to mathematical
7636 operators. @xref{Support, ,Supported languages}, for further
7637 details on specific languages.
7639 @value{GDBN} provides some additional commands for controlling the type checker:
7641 @kindex set check@r{, type}
7642 @kindex set check type
7643 @kindex show check type
7645 @item set check type auto
7646 Set type checking on or off based on the current working language.
7647 @xref{Support, ,Supported languages}, for the default settings for
7650 @item set check type on
7651 @itemx set check type off
7652 Set type checking on or off, overriding the default setting for the
7653 current working language. Issue a warning if the setting does not
7654 match the language default. If any type mismatches occur in
7655 evaluating an expression while type checking is on, @value{GDBN} prints a
7656 message and aborts evaluation of the expression.
7658 @item set check type warn
7659 Cause the type checker to issue warnings, but to always attempt to
7660 evaluate the expression. Evaluating the expression may still
7661 be impossible for other reasons. For example, @value{GDBN} cannot add
7662 numbers and structures.
7665 Show the current setting of the type checker, and whether or not @value{GDBN}
7666 is setting it automatically.
7669 @cindex range checking
7670 @cindex checks, range
7671 @node Range Checking
7672 @subsection An overview of range checking
7674 In some languages (such as Modula-2), it is an error to exceed the
7675 bounds of a type; this is enforced with run-time checks. Such range
7676 checking is meant to ensure program correctness by making sure
7677 computations do not overflow, or indices on an array element access do
7678 not exceed the bounds of the array.
7680 For expressions you use in @value{GDBN} commands, you can tell
7681 @value{GDBN} to treat range errors in one of three ways: ignore them,
7682 always treat them as errors and abandon the expression, or issue
7683 warnings but evaluate the expression anyway.
7685 A range error can result from numerical overflow, from exceeding an
7686 array index bound, or when you type a constant that is not a member
7687 of any type. Some languages, however, do not treat overflows as an
7688 error. In many implementations of C, mathematical overflow causes the
7689 result to ``wrap around'' to lower values---for example, if @var{m} is
7690 the largest integer value, and @var{s} is the smallest, then
7693 @var{m} + 1 @result{} @var{s}
7696 This, too, is specific to individual languages, and in some cases
7697 specific to individual compilers or machines. @xref{Support, ,
7698 Supported languages}, for further details on specific languages.
7700 @value{GDBN} provides some additional commands for controlling the range checker:
7702 @kindex set check@r{, range}
7703 @kindex set check range
7704 @kindex show check range
7706 @item set check range auto
7707 Set range checking on or off based on the current working language.
7708 @xref{Support, ,Supported languages}, for the default settings for
7711 @item set check range on
7712 @itemx set check range off
7713 Set range checking on or off, overriding the default setting for the
7714 current working language. A warning is issued if the setting does not
7715 match the language default. If a range error occurs and range checking is on,
7716 then a message is printed and evaluation of the expression is aborted.
7718 @item set check range warn
7719 Output messages when the @value{GDBN} range checker detects a range error,
7720 but attempt to evaluate the expression anyway. Evaluating the
7721 expression may still be impossible for other reasons, such as accessing
7722 memory that the process does not own (a typical example from many Unix
7726 Show the current setting of the range checker, and whether or not it is
7727 being set automatically by @value{GDBN}.
7731 @section Supported languages
7733 @value{GDBN} supports C, C@t{++}, Fortran, Java,
7735 assembly, and Modula-2.
7736 @c This is false ...
7737 Some @value{GDBN} features may be used in expressions regardless of the
7738 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7739 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7740 ,Expressions}) can be used with the constructs of any supported
7743 The following sections detail to what degree each source language is
7744 supported by @value{GDBN}. These sections are not meant to be language
7745 tutorials or references, but serve only as a reference guide to what the
7746 @value{GDBN} expression parser accepts, and what input and output
7747 formats should look like for different languages. There are many good
7748 books written on each of these languages; please look to these for a
7749 language reference or tutorial.
7753 * Modula-2:: Modula-2
7754 @c OBSOLETE * Chill:: Chill
7758 @subsection C and C@t{++}
7760 @cindex C and C@t{++}
7761 @cindex expressions in C or C@t{++}
7763 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7764 to both languages. Whenever this is the case, we discuss those languages
7768 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7769 @cindex @sc{gnu} C@t{++}
7770 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7771 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7772 effectively, you must compile your C@t{++} programs with a supported
7773 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7774 compiler (@code{aCC}).
7776 For best results when using @sc{gnu} C@t{++}, use the stabs debugging
7777 format. You can select that format explicitly with the @code{g++}
7778 command-line options @samp{-gstabs} or @samp{-gstabs+}. See
7779 @ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7780 CC, gcc.info, Using @sc{gnu} CC}, for more information.
7783 * C Operators:: C and C@t{++} operators
7784 * C Constants:: C and C@t{++} constants
7785 * C plus plus expressions:: C@t{++} expressions
7786 * C Defaults:: Default settings for C and C@t{++}
7787 * C Checks:: C and C@t{++} type and range checks
7788 * Debugging C:: @value{GDBN} and C
7789 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7793 @subsubsection C and C@t{++} operators
7795 @cindex C and C@t{++} operators
7797 Operators must be defined on values of specific types. For instance,
7798 @code{+} is defined on numbers, but not on structures. Operators are
7799 often defined on groups of types.
7801 For the purposes of C and C@t{++}, the following definitions hold:
7806 @emph{Integral types} include @code{int} with any of its storage-class
7807 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7810 @emph{Floating-point types} include @code{float}, @code{double}, and
7811 @code{long double} (if supported by the target platform).
7814 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7817 @emph{Scalar types} include all of the above.
7822 The following operators are supported. They are listed here
7823 in order of increasing precedence:
7827 The comma or sequencing operator. Expressions in a comma-separated list
7828 are evaluated from left to right, with the result of the entire
7829 expression being the last expression evaluated.
7832 Assignment. The value of an assignment expression is the value
7833 assigned. Defined on scalar types.
7836 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7837 and translated to @w{@code{@var{a} = @var{a op b}}}.
7838 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7839 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7840 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7843 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7844 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7848 Logical @sc{or}. Defined on integral types.
7851 Logical @sc{and}. Defined on integral types.
7854 Bitwise @sc{or}. Defined on integral types.
7857 Bitwise exclusive-@sc{or}. Defined on integral types.
7860 Bitwise @sc{and}. Defined on integral types.
7863 Equality and inequality. Defined on scalar types. The value of these
7864 expressions is 0 for false and non-zero for true.
7866 @item <@r{, }>@r{, }<=@r{, }>=
7867 Less than, greater than, less than or equal, greater than or equal.
7868 Defined on scalar types. The value of these expressions is 0 for false
7869 and non-zero for true.
7872 left shift, and right shift. Defined on integral types.
7875 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7878 Addition and subtraction. Defined on integral types, floating-point types and
7881 @item *@r{, }/@r{, }%
7882 Multiplication, division, and modulus. Multiplication and division are
7883 defined on integral and floating-point types. Modulus is defined on
7887 Increment and decrement. When appearing before a variable, the
7888 operation is performed before the variable is used in an expression;
7889 when appearing after it, the variable's value is used before the
7890 operation takes place.
7893 Pointer dereferencing. Defined on pointer types. Same precedence as
7897 Address operator. Defined on variables. Same precedence as @code{++}.
7899 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7900 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7901 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7902 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7906 Negative. Defined on integral and floating-point types. Same
7907 precedence as @code{++}.
7910 Logical negation. Defined on integral types. Same precedence as
7914 Bitwise complement operator. Defined on integral types. Same precedence as
7919 Structure member, and pointer-to-structure member. For convenience,
7920 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7921 pointer based on the stored type information.
7922 Defined on @code{struct} and @code{union} data.
7925 Dereferences of pointers to members.
7928 Array indexing. @code{@var{a}[@var{i}]} is defined as
7929 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7932 Function parameter list. Same precedence as @code{->}.
7935 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7936 and @code{class} types.
7939 Doubled colons also represent the @value{GDBN} scope operator
7940 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7944 If an operator is redefined in the user code, @value{GDBN} usually
7945 attempts to invoke the redefined version instead of using the operator's
7953 @subsubsection C and C@t{++} constants
7955 @cindex C and C@t{++} constants
7957 @value{GDBN} allows you to express the constants of C and C@t{++} in the
7962 Integer constants are a sequence of digits. Octal constants are
7963 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
7964 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
7965 @samp{l}, specifying that the constant should be treated as a
7969 Floating point constants are a sequence of digits, followed by a decimal
7970 point, followed by a sequence of digits, and optionally followed by an
7971 exponent. An exponent is of the form:
7972 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
7973 sequence of digits. The @samp{+} is optional for positive exponents.
7974 A floating-point constant may also end with a letter @samp{f} or
7975 @samp{F}, specifying that the constant should be treated as being of
7976 the @code{float} (as opposed to the default @code{double}) type; or with
7977 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
7981 Enumerated constants consist of enumerated identifiers, or their
7982 integral equivalents.
7985 Character constants are a single character surrounded by single quotes
7986 (@code{'}), or a number---the ordinal value of the corresponding character
7987 (usually its @sc{ascii} value). Within quotes, the single character may
7988 be represented by a letter or by @dfn{escape sequences}, which are of
7989 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
7990 of the character's ordinal value; or of the form @samp{\@var{x}}, where
7991 @samp{@var{x}} is a predefined special character---for example,
7992 @samp{\n} for newline.
7995 String constants are a sequence of character constants surrounded by
7996 double quotes (@code{"}). Any valid character constant (as described
7997 above) may appear. Double quotes within the string must be preceded by
7998 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8002 Pointer constants are an integral value. You can also write pointers
8003 to constants using the C operator @samp{&}.
8006 Array constants are comma-separated lists surrounded by braces @samp{@{}
8007 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8008 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8009 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8013 * C plus plus expressions::
8020 @node C plus plus expressions
8021 @subsubsection C@t{++} expressions
8023 @cindex expressions in C@t{++}
8024 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8026 @cindex C@t{++} support, not in @sc{coff}
8027 @cindex @sc{coff} versus C@t{++}
8028 @cindex C@t{++} and object formats
8029 @cindex object formats and C@t{++}
8030 @cindex a.out and C@t{++}
8031 @cindex @sc{ecoff} and C@t{++}
8032 @cindex @sc{xcoff} and C@t{++}
8033 @cindex @sc{elf}/stabs and C@t{++}
8034 @cindex @sc{elf}/@sc{dwarf} and C@t{++}
8035 @c FIXME!! GDB may eventually be able to debug C++ using DWARF; check
8036 @c periodically whether this has happened...
8038 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8039 proper compiler. Typically, C@t{++} debugging depends on the use of
8040 additional debugging information in the symbol table, and thus requires
8041 special support. In particular, if your compiler generates a.out, MIPS
8042 @sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the
8043 symbol table, these facilities are all available. (With @sc{gnu} CC,
8044 you can use the @samp{-gstabs} option to request stabs debugging
8045 extensions explicitly.) Where the object code format is standard
8046 @sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++}
8047 support in @value{GDBN} does @emph{not} work.
8052 @cindex member functions
8054 Member function calls are allowed; you can use expressions like
8057 count = aml->GetOriginal(x, y)
8060 @vindex this@r{, inside C@t{++} member functions}
8061 @cindex namespace in C@t{++}
8063 While a member function is active (in the selected stack frame), your
8064 expressions have the same namespace available as the member function;
8065 that is, @value{GDBN} allows implicit references to the class instance
8066 pointer @code{this} following the same rules as C@t{++}.
8068 @cindex call overloaded functions
8069 @cindex overloaded functions, calling
8070 @cindex type conversions in C@t{++}
8072 You can call overloaded functions; @value{GDBN} resolves the function
8073 call to the right definition, with some restrictions. @value{GDBN} does not
8074 perform overload resolution involving user-defined type conversions,
8075 calls to constructors, or instantiations of templates that do not exist
8076 in the program. It also cannot handle ellipsis argument lists or
8079 It does perform integral conversions and promotions, floating-point
8080 promotions, arithmetic conversions, pointer conversions, conversions of
8081 class objects to base classes, and standard conversions such as those of
8082 functions or arrays to pointers; it requires an exact match on the
8083 number of function arguments.
8085 Overload resolution is always performed, unless you have specified
8086 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8087 ,@value{GDBN} features for C@t{++}}.
8089 You must specify @code{set overload-resolution off} in order to use an
8090 explicit function signature to call an overloaded function, as in
8092 p 'foo(char,int)'('x', 13)
8095 The @value{GDBN} command-completion facility can simplify this;
8096 see @ref{Completion, ,Command completion}.
8098 @cindex reference declarations
8100 @value{GDBN} understands variables declared as C@t{++} references; you can use
8101 them in expressions just as you do in C@t{++} source---they are automatically
8104 In the parameter list shown when @value{GDBN} displays a frame, the values of
8105 reference variables are not displayed (unlike other variables); this
8106 avoids clutter, since references are often used for large structures.
8107 The @emph{address} of a reference variable is always shown, unless
8108 you have specified @samp{set print address off}.
8111 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8112 expressions can use it just as expressions in your program do. Since
8113 one scope may be defined in another, you can use @code{::} repeatedly if
8114 necessary, for example in an expression like
8115 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8116 resolving name scope by reference to source files, in both C and C@t{++}
8117 debugging (@pxref{Variables, ,Program variables}).
8120 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8121 calling virtual functions correctly, printing out virtual bases of
8122 objects, calling functions in a base subobject, casting objects, and
8123 invoking user-defined operators.
8126 @subsubsection C and C@t{++} defaults
8128 @cindex C and C@t{++} defaults
8130 If you allow @value{GDBN} to set type and range checking automatically, they
8131 both default to @code{off} whenever the working language changes to
8132 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8133 selects the working language.
8135 If you allow @value{GDBN} to set the language automatically, it
8136 recognizes source files whose names end with @file{.c}, @file{.C}, or
8137 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8138 these files, it sets the working language to C or C@t{++}.
8139 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8140 for further details.
8142 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8143 @c unimplemented. If (b) changes, it might make sense to let this node
8144 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8147 @subsubsection C and C@t{++} type and range checks
8149 @cindex C and C@t{++} checks
8151 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8152 is not used. However, if you turn type checking on, @value{GDBN}
8153 considers two variables type equivalent if:
8157 The two variables are structured and have the same structure, union, or
8161 The two variables have the same type name, or types that have been
8162 declared equivalent through @code{typedef}.
8165 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8168 The two @code{struct}, @code{union}, or @code{enum} variables are
8169 declared in the same declaration. (Note: this may not be true for all C
8174 Range checking, if turned on, is done on mathematical operations. Array
8175 indices are not checked, since they are often used to index a pointer
8176 that is not itself an array.
8179 @subsubsection @value{GDBN} and C
8181 The @code{set print union} and @code{show print union} commands apply to
8182 the @code{union} type. When set to @samp{on}, any @code{union} that is
8183 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8184 appears as @samp{@{...@}}.
8186 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8187 with pointers and a memory allocation function. @xref{Expressions,
8191 * Debugging C plus plus::
8194 @node Debugging C plus plus
8195 @subsubsection @value{GDBN} features for C@t{++}
8197 @cindex commands for C@t{++}
8199 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8200 designed specifically for use with C@t{++}. Here is a summary:
8203 @cindex break in overloaded functions
8204 @item @r{breakpoint menus}
8205 When you want a breakpoint in a function whose name is overloaded,
8206 @value{GDBN} breakpoint menus help you specify which function definition
8207 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8209 @cindex overloading in C@t{++}
8210 @item rbreak @var{regex}
8211 Setting breakpoints using regular expressions is helpful for setting
8212 breakpoints on overloaded functions that are not members of any special
8214 @xref{Set Breaks, ,Setting breakpoints}.
8216 @cindex C@t{++} exception handling
8219 Debug C@t{++} exception handling using these commands. @xref{Set
8220 Catchpoints, , Setting catchpoints}.
8223 @item ptype @var{typename}
8224 Print inheritance relationships as well as other information for type
8226 @xref{Symbols, ,Examining the Symbol Table}.
8228 @cindex C@t{++} symbol display
8229 @item set print demangle
8230 @itemx show print demangle
8231 @itemx set print asm-demangle
8232 @itemx show print asm-demangle
8233 Control whether C@t{++} symbols display in their source form, both when
8234 displaying code as C@t{++} source and when displaying disassemblies.
8235 @xref{Print Settings, ,Print settings}.
8237 @item set print object
8238 @itemx show print object
8239 Choose whether to print derived (actual) or declared types of objects.
8240 @xref{Print Settings, ,Print settings}.
8242 @item set print vtbl
8243 @itemx show print vtbl
8244 Control the format for printing virtual function tables.
8245 @xref{Print Settings, ,Print settings}.
8246 (The @code{vtbl} commands do not work on programs compiled with the HP
8247 ANSI C@t{++} compiler (@code{aCC}).)
8249 @kindex set overload-resolution
8250 @cindex overloaded functions, overload resolution
8251 @item set overload-resolution on
8252 Enable overload resolution for C@t{++} expression evaluation. The default
8253 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8254 and searches for a function whose signature matches the argument types,
8255 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8256 expressions}, for details). If it cannot find a match, it emits a
8259 @item set overload-resolution off
8260 Disable overload resolution for C@t{++} expression evaluation. For
8261 overloaded functions that are not class member functions, @value{GDBN}
8262 chooses the first function of the specified name that it finds in the
8263 symbol table, whether or not its arguments are of the correct type. For
8264 overloaded functions that are class member functions, @value{GDBN}
8265 searches for a function whose signature @emph{exactly} matches the
8268 @item @r{Overloaded symbol names}
8269 You can specify a particular definition of an overloaded symbol, using
8270 the same notation that is used to declare such symbols in C@t{++}: type
8271 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8272 also use the @value{GDBN} command-line word completion facilities to list the
8273 available choices, or to finish the type list for you.
8274 @xref{Completion,, Command completion}, for details on how to do this.
8278 @subsection Modula-2
8280 @cindex Modula-2, @value{GDBN} support
8282 The extensions made to @value{GDBN} to support Modula-2 only support
8283 output from the @sc{gnu} Modula-2 compiler (which is currently being
8284 developed). Other Modula-2 compilers are not currently supported, and
8285 attempting to debug executables produced by them is most likely
8286 to give an error as @value{GDBN} reads in the executable's symbol
8289 @cindex expressions in Modula-2
8291 * M2 Operators:: Built-in operators
8292 * Built-In Func/Proc:: Built-in functions and procedures
8293 * M2 Constants:: Modula-2 constants
8294 * M2 Defaults:: Default settings for Modula-2
8295 * Deviations:: Deviations from standard Modula-2
8296 * M2 Checks:: Modula-2 type and range checks
8297 * M2 Scope:: The scope operators @code{::} and @code{.}
8298 * GDB/M2:: @value{GDBN} and Modula-2
8302 @subsubsection Operators
8303 @cindex Modula-2 operators
8305 Operators must be defined on values of specific types. For instance,
8306 @code{+} is defined on numbers, but not on structures. Operators are
8307 often defined on groups of types. For the purposes of Modula-2, the
8308 following definitions hold:
8313 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8317 @emph{Character types} consist of @code{CHAR} and its subranges.
8320 @emph{Floating-point types} consist of @code{REAL}.
8323 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8327 @emph{Scalar types} consist of all of the above.
8330 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8333 @emph{Boolean types} consist of @code{BOOLEAN}.
8337 The following operators are supported, and appear in order of
8338 increasing precedence:
8342 Function argument or array index separator.
8345 Assignment. The value of @var{var} @code{:=} @var{value} is
8349 Less than, greater than on integral, floating-point, or enumerated
8353 Less than or equal to, greater than or equal to
8354 on integral, floating-point and enumerated types, or set inclusion on
8355 set types. Same precedence as @code{<}.
8357 @item =@r{, }<>@r{, }#
8358 Equality and two ways of expressing inequality, valid on scalar types.
8359 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8360 available for inequality, since @code{#} conflicts with the script
8364 Set membership. Defined on set types and the types of their members.
8365 Same precedence as @code{<}.
8368 Boolean disjunction. Defined on boolean types.
8371 Boolean conjunction. Defined on boolean types.
8374 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8377 Addition and subtraction on integral and floating-point types, or union
8378 and difference on set types.
8381 Multiplication on integral and floating-point types, or set intersection
8385 Division on floating-point types, or symmetric set difference on set
8386 types. Same precedence as @code{*}.
8389 Integer division and remainder. Defined on integral types. Same
8390 precedence as @code{*}.
8393 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8396 Pointer dereferencing. Defined on pointer types.
8399 Boolean negation. Defined on boolean types. Same precedence as
8403 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8404 precedence as @code{^}.
8407 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8410 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8414 @value{GDBN} and Modula-2 scope operators.
8418 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8419 treats the use of the operator @code{IN}, or the use of operators
8420 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8421 @code{<=}, and @code{>=} on sets as an error.
8425 @node Built-In Func/Proc
8426 @subsubsection Built-in functions and procedures
8427 @cindex Modula-2 built-ins
8429 Modula-2 also makes available several built-in procedures and functions.
8430 In describing these, the following metavariables are used:
8435 represents an @code{ARRAY} variable.
8438 represents a @code{CHAR} constant or variable.
8441 represents a variable or constant of integral type.
8444 represents an identifier that belongs to a set. Generally used in the
8445 same function with the metavariable @var{s}. The type of @var{s} should
8446 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8449 represents a variable or constant of integral or floating-point type.
8452 represents a variable or constant of floating-point type.
8458 represents a variable.
8461 represents a variable or constant of one of many types. See the
8462 explanation of the function for details.
8465 All Modula-2 built-in procedures also return a result, described below.
8469 Returns the absolute value of @var{n}.
8472 If @var{c} is a lower case letter, it returns its upper case
8473 equivalent, otherwise it returns its argument.
8476 Returns the character whose ordinal value is @var{i}.
8479 Decrements the value in the variable @var{v} by one. Returns the new value.
8481 @item DEC(@var{v},@var{i})
8482 Decrements the value in the variable @var{v} by @var{i}. Returns the
8485 @item EXCL(@var{m},@var{s})
8486 Removes the element @var{m} from the set @var{s}. Returns the new
8489 @item FLOAT(@var{i})
8490 Returns the floating point equivalent of the integer @var{i}.
8493 Returns the index of the last member of @var{a}.
8496 Increments the value in the variable @var{v} by one. Returns the new value.
8498 @item INC(@var{v},@var{i})
8499 Increments the value in the variable @var{v} by @var{i}. Returns the
8502 @item INCL(@var{m},@var{s})
8503 Adds the element @var{m} to the set @var{s} if it is not already
8504 there. Returns the new set.
8507 Returns the maximum value of the type @var{t}.
8510 Returns the minimum value of the type @var{t}.
8513 Returns boolean TRUE if @var{i} is an odd number.
8516 Returns the ordinal value of its argument. For example, the ordinal
8517 value of a character is its @sc{ascii} value (on machines supporting the
8518 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8519 integral, character and enumerated types.
8522 Returns the size of its argument. @var{x} can be a variable or a type.
8524 @item TRUNC(@var{r})
8525 Returns the integral part of @var{r}.
8527 @item VAL(@var{t},@var{i})
8528 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8532 @emph{Warning:} Sets and their operations are not yet supported, so
8533 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8537 @cindex Modula-2 constants
8539 @subsubsection Constants
8541 @value{GDBN} allows you to express the constants of Modula-2 in the following
8547 Integer constants are simply a sequence of digits. When used in an
8548 expression, a constant is interpreted to be type-compatible with the
8549 rest of the expression. Hexadecimal integers are specified by a
8550 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8553 Floating point constants appear as a sequence of digits, followed by a
8554 decimal point and another sequence of digits. An optional exponent can
8555 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8556 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8557 digits of the floating point constant must be valid decimal (base 10)
8561 Character constants consist of a single character enclosed by a pair of
8562 like quotes, either single (@code{'}) or double (@code{"}). They may
8563 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8564 followed by a @samp{C}.
8567 String constants consist of a sequence of characters enclosed by a
8568 pair of like quotes, either single (@code{'}) or double (@code{"}).
8569 Escape sequences in the style of C are also allowed. @xref{C
8570 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8574 Enumerated constants consist of an enumerated identifier.
8577 Boolean constants consist of the identifiers @code{TRUE} and
8581 Pointer constants consist of integral values only.
8584 Set constants are not yet supported.
8588 @subsubsection Modula-2 defaults
8589 @cindex Modula-2 defaults
8591 If type and range checking are set automatically by @value{GDBN}, they
8592 both default to @code{on} whenever the working language changes to
8593 Modula-2. This happens regardless of whether you or @value{GDBN}
8594 selected the working language.
8596 If you allow @value{GDBN} to set the language automatically, then entering
8597 code compiled from a file whose name ends with @file{.mod} sets the
8598 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8599 the language automatically}, for further details.
8602 @subsubsection Deviations from standard Modula-2
8603 @cindex Modula-2, deviations from
8605 A few changes have been made to make Modula-2 programs easier to debug.
8606 This is done primarily via loosening its type strictness:
8610 Unlike in standard Modula-2, pointer constants can be formed by
8611 integers. This allows you to modify pointer variables during
8612 debugging. (In standard Modula-2, the actual address contained in a
8613 pointer variable is hidden from you; it can only be modified
8614 through direct assignment to another pointer variable or expression that
8615 returned a pointer.)
8618 C escape sequences can be used in strings and characters to represent
8619 non-printable characters. @value{GDBN} prints out strings with these
8620 escape sequences embedded. Single non-printable characters are
8621 printed using the @samp{CHR(@var{nnn})} format.
8624 The assignment operator (@code{:=}) returns the value of its right-hand
8628 All built-in procedures both modify @emph{and} return their argument.
8632 @subsubsection Modula-2 type and range checks
8633 @cindex Modula-2 checks
8636 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8639 @c FIXME remove warning when type/range checks added
8641 @value{GDBN} considers two Modula-2 variables type equivalent if:
8645 They are of types that have been declared equivalent via a @code{TYPE
8646 @var{t1} = @var{t2}} statement
8649 They have been declared on the same line. (Note: This is true of the
8650 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8653 As long as type checking is enabled, any attempt to combine variables
8654 whose types are not equivalent is an error.
8656 Range checking is done on all mathematical operations, assignment, array
8657 index bounds, and all built-in functions and procedures.
8660 @subsubsection The scope operators @code{::} and @code{.}
8662 @cindex @code{.}, Modula-2 scope operator
8663 @cindex colon, doubled as scope operator
8665 @vindex colon-colon@r{, in Modula-2}
8666 @c Info cannot handle :: but TeX can.
8669 @vindex ::@r{, in Modula-2}
8672 There are a few subtle differences between the Modula-2 scope operator
8673 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8678 @var{module} . @var{id}
8679 @var{scope} :: @var{id}
8683 where @var{scope} is the name of a module or a procedure,
8684 @var{module} the name of a module, and @var{id} is any declared
8685 identifier within your program, except another module.
8687 Using the @code{::} operator makes @value{GDBN} search the scope
8688 specified by @var{scope} for the identifier @var{id}. If it is not
8689 found in the specified scope, then @value{GDBN} searches all scopes
8690 enclosing the one specified by @var{scope}.
8692 Using the @code{.} operator makes @value{GDBN} search the current scope for
8693 the identifier specified by @var{id} that was imported from the
8694 definition module specified by @var{module}. With this operator, it is
8695 an error if the identifier @var{id} was not imported from definition
8696 module @var{module}, or if @var{id} is not an identifier in
8700 @subsubsection @value{GDBN} and Modula-2
8702 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8703 Five subcommands of @code{set print} and @code{show print} apply
8704 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8705 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8706 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8707 analogue in Modula-2.
8709 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8710 with any language, is not useful with Modula-2. Its
8711 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8712 created in Modula-2 as they can in C or C@t{++}. However, because an
8713 address can be specified by an integral constant, the construct
8714 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8716 @cindex @code{#} in Modula-2
8717 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8718 interpreted as the beginning of a comment. Use @code{<>} instead.
8720 @c OBSOLETE @node Chill
8721 @c OBSOLETE @subsection Chill
8723 @c OBSOLETE The extensions made to @value{GDBN} to support Chill only support output
8724 @c OBSOLETE from the @sc{gnu} Chill compiler. Other Chill compilers are not currently
8725 @c OBSOLETE supported, and attempting to debug executables produced by them is most
8726 @c OBSOLETE likely to give an error as @value{GDBN} reads in the executable's symbol
8729 @c OBSOLETE @c This used to say "... following Chill related topics ...", but since
8730 @c OBSOLETE @c menus are not shown in the printed manual, it would look awkward.
8731 @c OBSOLETE This section covers the Chill related topics and the features
8732 @c OBSOLETE of @value{GDBN} which support these topics.
8735 @c OBSOLETE * How modes are displayed:: How modes are displayed
8736 @c OBSOLETE * Locations:: Locations and their accesses
8737 @c OBSOLETE * Values and their Operations:: Values and their Operations
8738 @c OBSOLETE * Chill type and range checks::
8739 @c OBSOLETE * Chill defaults::
8740 @c OBSOLETE @end menu
8742 @c OBSOLETE @node How modes are displayed
8743 @c OBSOLETE @subsubsection How modes are displayed
8745 @c OBSOLETE The Chill Datatype- (Mode) support of @value{GDBN} is directly related
8746 @c OBSOLETE with the functionality of the @sc{gnu} Chill compiler, and therefore deviates
8747 @c OBSOLETE slightly from the standard specification of the Chill language. The
8748 @c OBSOLETE provided modes are:
8750 @c OBSOLETE @c FIXME: this @table's contents effectively disable @code by using @r
8751 @c OBSOLETE @c on every @item. So why does it need @code?
8752 @c OBSOLETE @table @code
8753 @c OBSOLETE @item @r{@emph{Discrete modes:}}
8754 @c OBSOLETE @itemize @bullet
8756 @c OBSOLETE @emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT,
8757 @c OBSOLETE UINT, LONG, ULONG},
8759 @c OBSOLETE @emph{Boolean Mode} which is predefined by @code{BOOL},
8761 @c OBSOLETE @emph{Character Mode} which is predefined by @code{CHAR},
8763 @c OBSOLETE @emph{Set Mode} which is displayed by the keyword @code{SET}.
8764 @c OBSOLETE @smallexample
8765 @c OBSOLETE (@value{GDBP}) ptype x
8766 @c OBSOLETE type = SET (karli = 10, susi = 20, fritzi = 100)
8767 @c OBSOLETE @end smallexample
8768 @c OBSOLETE If the type is an unnumbered set the set element values are omitted.
8770 @c OBSOLETE @emph{Range Mode} which is displayed by
8771 @c OBSOLETE @smallexample
8772 @c OBSOLETE @code{type = <basemode>(<lower bound> : <upper bound>)}
8773 @c OBSOLETE @end smallexample
8774 @c OBSOLETE where @code{<lower bound>, <upper bound>} can be of any discrete literal
8775 @c OBSOLETE expression (e.g. set element names).
8776 @c OBSOLETE @end itemize
8778 @c OBSOLETE @item @r{@emph{Powerset Mode:}}
8779 @c OBSOLETE A Powerset Mode is displayed by the keyword @code{POWERSET} followed by
8780 @c OBSOLETE the member mode of the powerset. The member mode can be any discrete mode.
8781 @c OBSOLETE @smallexample
8782 @c OBSOLETE (@value{GDBP}) ptype x
8783 @c OBSOLETE type = POWERSET SET (egon, hugo, otto)
8784 @c OBSOLETE @end smallexample
8786 @c OBSOLETE @item @r{@emph{Reference Modes:}}
8787 @c OBSOLETE @itemize @bullet
8789 @c OBSOLETE @emph{Bound Reference Mode} which is displayed by the keyword @code{REF}
8790 @c OBSOLETE followed by the mode name to which the reference is bound.
8792 @c OBSOLETE @emph{Free Reference Mode} which is displayed by the keyword @code{PTR}.
8793 @c OBSOLETE @end itemize
8795 @c OBSOLETE @item @r{@emph{Procedure mode}}
8796 @c OBSOLETE The procedure mode is displayed by @code{type = PROC(<parameter list>)
8797 @c OBSOLETE <return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter
8798 @c OBSOLETE list>} is a list of the parameter modes. @code{<return mode>} indicates
8799 @c OBSOLETE the mode of the result of the procedure if any. The exceptionlist lists
8800 @c OBSOLETE all possible exceptions which can be raised by the procedure.
8803 @c OBSOLETE @item @r{@emph{Instance mode}}
8804 @c OBSOLETE The instance mode is represented by a structure, which has a static
8805 @c OBSOLETE type, and is therefore not really of interest.
8806 @c OBSOLETE @end ignore
8808 @c OBSOLETE @item @r{@emph{Synchronization Modes:}}
8809 @c OBSOLETE @itemize @bullet
8811 @c OBSOLETE @emph{Event Mode} which is displayed by
8812 @c OBSOLETE @smallexample
8813 @c OBSOLETE @code{EVENT (<event length>)}
8814 @c OBSOLETE @end smallexample
8815 @c OBSOLETE where @code{(<event length>)} is optional.
8817 @c OBSOLETE @emph{Buffer Mode} which is displayed by
8818 @c OBSOLETE @smallexample
8819 @c OBSOLETE @code{BUFFER (<buffer length>)<buffer element mode>}
8820 @c OBSOLETE @end smallexample
8821 @c OBSOLETE where @code{(<buffer length>)} is optional.
8822 @c OBSOLETE @end itemize
8824 @c OBSOLETE @item @r{@emph{Timing Modes:}}
8825 @c OBSOLETE @itemize @bullet
8827 @c OBSOLETE @emph{Duration Mode} which is predefined by @code{DURATION}
8829 @c OBSOLETE @emph{Absolute Time Mode} which is predefined by @code{TIME}
8830 @c OBSOLETE @end itemize
8832 @c OBSOLETE @item @r{@emph{Real Modes:}}
8833 @c OBSOLETE Real Modes are predefined with @code{REAL} and @code{LONG_REAL}.
8835 @c OBSOLETE @item @r{@emph{String Modes:}}
8836 @c OBSOLETE @itemize @bullet
8838 @c OBSOLETE @emph{Character String Mode} which is displayed by
8839 @c OBSOLETE @smallexample
8840 @c OBSOLETE @code{CHARS(<string length>)}
8841 @c OBSOLETE @end smallexample
8842 @c OBSOLETE followed by the keyword @code{VARYING} if the String Mode is a varying
8845 @c OBSOLETE @emph{Bit String Mode} which is displayed by
8846 @c OBSOLETE @smallexample
8847 @c OBSOLETE @code{BOOLS(<string
8848 @c OBSOLETE length>)}
8849 @c OBSOLETE @end smallexample
8850 @c OBSOLETE @end itemize
8852 @c OBSOLETE @item @r{@emph{Array Mode:}}
8853 @c OBSOLETE The Array Mode is displayed by the keyword @code{ARRAY(<range>)}
8854 @c OBSOLETE followed by the element mode (which may in turn be an array mode).
8855 @c OBSOLETE @smallexample
8856 @c OBSOLETE (@value{GDBP}) ptype x
8857 @c OBSOLETE type = ARRAY (1:42)
8858 @c OBSOLETE ARRAY (1:20)
8859 @c OBSOLETE SET (karli = 10, susi = 20, fritzi = 100)
8860 @c OBSOLETE @end smallexample
8862 @c OBSOLETE @item @r{@emph{Structure Mode}}
8863 @c OBSOLETE The Structure mode is displayed by the keyword @code{STRUCT(<field
8864 @c OBSOLETE list>)}. The @code{<field list>} consists of names and modes of fields
8865 @c OBSOLETE of the structure. Variant structures have the keyword @code{CASE <field>
8866 @c OBSOLETE OF <variant fields> ESAC} in their field list. Since the current version
8867 @c OBSOLETE of the GNU Chill compiler doesn't implement tag processing (no runtime
8868 @c OBSOLETE checks of variant fields, and therefore no debugging info), the output
8869 @c OBSOLETE always displays all variant fields.
8870 @c OBSOLETE @smallexample
8871 @c OBSOLETE (@value{GDBP}) ptype str
8872 @c OBSOLETE type = STRUCT (
8875 @c OBSOLETE CASE bs OF
8876 @c OBSOLETE (karli):
8882 @c OBSOLETE @end smallexample
8883 @c OBSOLETE @end table
8885 @c OBSOLETE @node Locations
8886 @c OBSOLETE @subsubsection Locations and their accesses
8888 @c OBSOLETE A location in Chill is an object which can contain values.
8890 @c OBSOLETE A value of a location is generally accessed by the (declared) name of
8891 @c OBSOLETE the location. The output conforms to the specification of values in
8892 @c OBSOLETE Chill programs. How values are specified
8893 @c OBSOLETE is the topic of the next section, @ref{Values and their Operations}.
8895 @c OBSOLETE The pseudo-location @code{RESULT} (or @code{result}) can be used to
8896 @c OBSOLETE display or change the result of a currently-active procedure:
8898 @c OBSOLETE @smallexample
8899 @c OBSOLETE set result := EXPR
8900 @c OBSOLETE @end smallexample
8902 @c OBSOLETE @noindent
8903 @c OBSOLETE This does the same as the Chill action @code{RESULT EXPR} (which
8904 @c OBSOLETE is not available in @value{GDBN}).
8906 @c OBSOLETE Values of reference mode locations are printed by @code{PTR(<hex
8907 @c OBSOLETE value>)} in case of a free reference mode, and by @code{(REF <reference
8908 @c OBSOLETE mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>}
8909 @c OBSOLETE represents the address where the reference points to. To access the
8910 @c OBSOLETE value of the location referenced by the pointer, use the dereference
8911 @c OBSOLETE operator @samp{->}.
8913 @c OBSOLETE Values of procedure mode locations are displayed by
8914 @c OBSOLETE @smallexample
8915 @c OBSOLETE @code{@{ PROC
8916 @c OBSOLETE (<argument modes> ) <return mode> @} <address> <name of procedure
8917 @c OBSOLETE location>}
8918 @c OBSOLETE @end smallexample
8919 @c OBSOLETE @code{<argument modes>} is a list of modes according to the parameter
8920 @c OBSOLETE specification of the procedure and @code{<address>} shows the address of
8921 @c OBSOLETE the entry point.
8924 @c OBSOLETE Locations of instance modes are displayed just like a structure with two
8925 @c OBSOLETE fields specifying the @emph{process type} and the @emph{copy number} of
8926 @c OBSOLETE the investigated instance location@footnote{This comes from the current
8927 @c OBSOLETE implementation of instances. They are implemented as a structure (no
8928 @c OBSOLETE na). The output should be something like @code{[<name of the process>;
8929 @c OBSOLETE <instance number>]}.}. The field names are @code{__proc_type} and
8930 @c OBSOLETE @code{__proc_copy}.
8932 @c OBSOLETE Locations of synchronization modes are displayed like a structure with
8933 @c OBSOLETE the field name @code{__event_data} in case of a event mode location, and
8934 @c OBSOLETE like a structure with the field @code{__buffer_data} in case of a buffer
8935 @c OBSOLETE mode location (refer to previous paragraph).
8937 @c OBSOLETE Structure Mode locations are printed by @code{[.<field name>: <value>,
8938 @c OBSOLETE ...]}. The @code{<field name>} corresponds to the structure mode
8939 @c OBSOLETE definition and the layout of @code{<value>} varies depending of the mode
8940 @c OBSOLETE of the field. If the investigated structure mode location is of variant
8941 @c OBSOLETE structure mode, the variant parts of the structure are enclosed in curled
8942 @c OBSOLETE braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing
8943 @c OBSOLETE on the same memory location and represent the current values of the
8944 @c OBSOLETE memory location in their specific modes. Since no tag processing is done
8945 @c OBSOLETE all variants are displayed. A variant field is printed by
8946 @c OBSOLETE @code{(<variant name>) = .<field name>: <value>}. (who implements the
8947 @c OBSOLETE stuff ???)
8948 @c OBSOLETE @smallexample
8949 @c OBSOLETE (@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) =
8950 @c OBSOLETE [.cs: []], (susi) = [.ds: susi]}]
8951 @c OBSOLETE @end smallexample
8952 @c OBSOLETE @end ignore
8954 @c OBSOLETE Substructures of string mode-, array mode- or structure mode-values
8955 @c OBSOLETE (e.g. array slices, fields of structure locations) are accessed using
8956 @c OBSOLETE certain operations which are described in the next section, @ref{Values
8957 @c OBSOLETE and their Operations}.
8959 @c OBSOLETE A location value may be interpreted as having a different mode using the
8960 @c OBSOLETE location conversion. This mode conversion is written as @code{<mode
8961 @c OBSOLETE name>(<location>)}. The user has to consider that the sizes of the modes
8962 @c OBSOLETE have to be equal otherwise an error occurs. Furthermore, no range
8963 @c OBSOLETE checking of the location against the destination mode is performed, and
8964 @c OBSOLETE therefore the result can be quite confusing.
8966 @c OBSOLETE @smallexample
8967 @c OBSOLETE (@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX
8968 @c OBSOLETE @end smallexample
8970 @c OBSOLETE @node Values and their Operations
8971 @c OBSOLETE @subsubsection Values and their Operations
8973 @c OBSOLETE Values are used to alter locations, to investigate complex structures in
8974 @c OBSOLETE more detail or to filter relevant information out of a large amount of
8975 @c OBSOLETE data. There are several (mode dependent) operations defined which enable
8976 @c OBSOLETE such investigations. These operations are not only applicable to
8977 @c OBSOLETE constant values but also to locations, which can become quite useful
8978 @c OBSOLETE when debugging complex structures. During parsing the command line
8979 @c OBSOLETE (e.g. evaluating an expression) @value{GDBN} treats location names as
8980 @c OBSOLETE the values behind these locations.
8982 @c OBSOLETE This section describes how values have to be specified and which
8983 @c OBSOLETE operations are legal to be used with such values.
8985 @c OBSOLETE @table @code
8986 @c OBSOLETE @item Literal Values
8987 @c OBSOLETE Literal values are specified in the same manner as in @sc{gnu} Chill programs.
8988 @c OBSOLETE For detailed specification refer to the @sc{gnu} Chill implementation Manual
8989 @c OBSOLETE chapter 1.5.
8990 @c OBSOLETE @c FIXME: if the Chill Manual is a Texinfo documents, the above should
8991 @c OBSOLETE @c be converted to a @ref.
8994 @c OBSOLETE @itemize @bullet
8996 @c OBSOLETE @emph{Integer Literals} are specified in the same manner as in Chill
8997 @c OBSOLETE programs (refer to the Chill Standard z200/88 chpt 5.2.4.2)
8999 @c OBSOLETE @emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}.
9001 @c OBSOLETE @emph{Character Literals} are defined by @code{'<character>'}. (e.g.
9002 @c OBSOLETE @code{'M'})
9004 @c OBSOLETE @emph{Set Literals} are defined by a name which was specified in a set
9005 @c OBSOLETE mode. The value delivered by a Set Literal is the set value. This is
9006 @c OBSOLETE comparable to an enumeration in C/C@t{++} language.
9008 @c OBSOLETE @emph{Emptiness Literal} is predefined by @code{NULL}. The value of the
9009 @c OBSOLETE emptiness literal delivers either the empty reference value, the empty
9010 @c OBSOLETE procedure value or the empty instance value.
9013 @c OBSOLETE @emph{Character String Literals} are defined by a sequence of characters
9014 @c OBSOLETE enclosed in single- or double quotes. If a single- or double quote has
9015 @c OBSOLETE to be part of the string literal it has to be stuffed (specified twice).
9017 @c OBSOLETE @emph{Bitstring Literals} are specified in the same manner as in Chill
9018 @c OBSOLETE programs (refer z200/88 chpt 5.2.4.8).
9020 @c OBSOLETE @emph{Floating point literals} are specified in the same manner as in
9021 @c OBSOLETE (gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5).
9022 @c OBSOLETE @end itemize
9023 @c OBSOLETE @end ignore
9025 @c OBSOLETE @item Tuple Values
9026 @c OBSOLETE A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode
9027 @c OBSOLETE name>} can be omitted if the mode of the tuple is unambiguous. This
9028 @c OBSOLETE unambiguity is derived from the context of a evaluated expression.
9029 @c OBSOLETE @code{<tuple>} can be one of the following:
9031 @c OBSOLETE @itemize @bullet
9032 @c OBSOLETE @item @emph{Powerset Tuple}
9033 @c OBSOLETE @item @emph{Array Tuple}
9034 @c OBSOLETE @item @emph{Structure Tuple}
9035 @c OBSOLETE Powerset tuples, array tuples and structure tuples are specified in the
9036 @c OBSOLETE same manner as in Chill programs refer to z200/88 chpt 5.2.5.
9037 @c OBSOLETE @end itemize
9039 @c OBSOLETE @item String Element Value
9040 @c OBSOLETE A string element value is specified by
9041 @c OBSOLETE @smallexample
9042 @c OBSOLETE @code{<string value>(<index>)}
9043 @c OBSOLETE @end smallexample
9044 @c OBSOLETE where @code{<index>} is a integer expression. It delivers a character
9045 @c OBSOLETE value which is equivalent to the character indexed by @code{<index>} in
9046 @c OBSOLETE the string.
9048 @c OBSOLETE @item String Slice Value
9049 @c OBSOLETE A string slice value is specified by @code{<string value>(<slice
9050 @c OBSOLETE spec>)}, where @code{<slice spec>} can be either a range of integer
9051 @c OBSOLETE expressions or specified by @code{<start expr> up <size>}.
9052 @c OBSOLETE @code{<size>} denotes the number of elements which the slice contains.
9053 @c OBSOLETE The delivered value is a string value, which is part of the specified
9056 @c OBSOLETE @item Array Element Values
9057 @c OBSOLETE An array element value is specified by @code{<array value>(<expr>)} and
9058 @c OBSOLETE delivers a array element value of the mode of the specified array.
9060 @c OBSOLETE @item Array Slice Values
9061 @c OBSOLETE An array slice is specified by @code{<array value>(<slice spec>)}, where
9062 @c OBSOLETE @code{<slice spec>} can be either a range specified by expressions or by
9063 @c OBSOLETE @code{<start expr> up <size>}. @code{<size>} denotes the number of
9064 @c OBSOLETE arrayelements the slice contains. The delivered value is an array value
9065 @c OBSOLETE which is part of the specified array.
9067 @c OBSOLETE @item Structure Field Values
9068 @c OBSOLETE A structure field value is derived by @code{<structure value>.<field
9069 @c OBSOLETE name>}, where @code{<field name>} indicates the name of a field specified
9070 @c OBSOLETE in the mode definition of the structure. The mode of the delivered value
9071 @c OBSOLETE corresponds to this mode definition in the structure definition.
9073 @c OBSOLETE @item Procedure Call Value
9074 @c OBSOLETE The procedure call value is derived from the return value of the
9075 @c OBSOLETE procedure@footnote{If a procedure call is used for instance in an
9076 @c OBSOLETE expression, then this procedure is called with all its side
9077 @c OBSOLETE effects. This can lead to confusing results if used carelessly.}.
9079 @c OBSOLETE Values of duration mode locations are represented by @code{ULONG} literals.
9081 @c OBSOLETE Values of time mode locations appear as
9082 @c OBSOLETE @smallexample
9083 @c OBSOLETE @code{TIME(<secs>:<nsecs>)}
9084 @c OBSOLETE @end smallexample
9088 @c OBSOLETE This is not implemented yet:
9089 @c OBSOLETE @item Built-in Value
9090 @c OBSOLETE @noindent
9091 @c OBSOLETE The following built in functions are provided:
9093 @c OBSOLETE @table @code
9094 @c OBSOLETE @item @code{ADDR()}
9095 @c OBSOLETE @item @code{NUM()}
9096 @c OBSOLETE @item @code{PRED()}
9097 @c OBSOLETE @item @code{SUCC()}
9098 @c OBSOLETE @item @code{ABS()}
9099 @c OBSOLETE @item @code{CARD()}
9100 @c OBSOLETE @item @code{MAX()}
9101 @c OBSOLETE @item @code{MIN()}
9102 @c OBSOLETE @item @code{SIZE()}
9103 @c OBSOLETE @item @code{UPPER()}
9104 @c OBSOLETE @item @code{LOWER()}
9105 @c OBSOLETE @item @code{LENGTH()}
9106 @c OBSOLETE @item @code{SIN()}
9107 @c OBSOLETE @item @code{COS()}
9108 @c OBSOLETE @item @code{TAN()}
9109 @c OBSOLETE @item @code{ARCSIN()}
9110 @c OBSOLETE @item @code{ARCCOS()}
9111 @c OBSOLETE @item @code{ARCTAN()}
9112 @c OBSOLETE @item @code{EXP()}
9113 @c OBSOLETE @item @code{LN()}
9114 @c OBSOLETE @item @code{LOG()}
9115 @c OBSOLETE @item @code{SQRT()}
9116 @c OBSOLETE @end table
9118 @c OBSOLETE For a detailed description refer to the GNU Chill implementation manual
9119 @c OBSOLETE chapter 1.6.
9120 @c OBSOLETE @end ignore
9122 @c OBSOLETE @item Zero-adic Operator Value
9123 @c OBSOLETE The zero-adic operator value is derived from the instance value for the
9124 @c OBSOLETE current active process.
9126 @c OBSOLETE @item Expression Values
9127 @c OBSOLETE The value delivered by an expression is the result of the evaluation of
9128 @c OBSOLETE the specified expression. If there are error conditions (mode
9129 @c OBSOLETE incompatibility, etc.) the evaluation of expressions is aborted with a
9130 @c OBSOLETE corresponding error message. Expressions may be parenthesised which
9131 @c OBSOLETE causes the evaluation of this expression before any other expression
9132 @c OBSOLETE which uses the result of the parenthesised expression. The following
9133 @c OBSOLETE operators are supported by @value{GDBN}:
9135 @c OBSOLETE @table @code
9136 @c OBSOLETE @item @code{OR, ORIF, XOR}
9137 @c OBSOLETE @itemx @code{AND, ANDIF}
9138 @c OBSOLETE @itemx @code{NOT}
9139 @c OBSOLETE Logical operators defined over operands of boolean mode.
9141 @c OBSOLETE @item @code{=, /=}
9142 @c OBSOLETE Equality and inequality operators defined over all modes.
9144 @c OBSOLETE @item @code{>, >=}
9145 @c OBSOLETE @itemx @code{<, <=}
9146 @c OBSOLETE Relational operators defined over predefined modes.
9148 @c OBSOLETE @item @code{+, -}
9149 @c OBSOLETE @itemx @code{*, /, MOD, REM}
9150 @c OBSOLETE Arithmetic operators defined over predefined modes.
9152 @c OBSOLETE @item @code{-}
9153 @c OBSOLETE Change sign operator.
9155 @c OBSOLETE @item @code{//}
9156 @c OBSOLETE String concatenation operator.
9158 @c OBSOLETE @item @code{()}
9159 @c OBSOLETE String repetition operator.
9161 @c OBSOLETE @item @code{->}
9162 @c OBSOLETE Referenced location operator which can be used either to take the
9163 @c OBSOLETE address of a location (@code{->loc}), or to dereference a reference
9164 @c OBSOLETE location (@code{loc->}).
9166 @c OBSOLETE @item @code{OR, XOR}
9167 @c OBSOLETE @itemx @code{AND}
9168 @c OBSOLETE @itemx @code{NOT}
9169 @c OBSOLETE Powerset and bitstring operators.
9171 @c OBSOLETE @item @code{>, >=}
9172 @c OBSOLETE @itemx @code{<, <=}
9173 @c OBSOLETE Powerset inclusion operators.
9175 @c OBSOLETE @item @code{IN}
9176 @c OBSOLETE Membership operator.
9177 @c OBSOLETE @end table
9178 @c OBSOLETE @end table
9180 @c OBSOLETE @node Chill type and range checks
9181 @c OBSOLETE @subsubsection Chill type and range checks
9183 @c OBSOLETE @value{GDBN} considers two Chill variables mode equivalent if the sizes
9184 @c OBSOLETE of the two modes are equal. This rule applies recursively to more
9185 @c OBSOLETE complex datatypes which means that complex modes are treated
9186 @c OBSOLETE equivalent if all element modes (which also can be complex modes like
9187 @c OBSOLETE structures, arrays, etc.) have the same size.
9189 @c OBSOLETE Range checking is done on all mathematical operations, assignment, array
9190 @c OBSOLETE index bounds and all built in procedures.
9192 @c OBSOLETE Strong type checks are forced using the @value{GDBN} command @code{set
9193 @c OBSOLETE check strong}. This enforces strong type and range checks on all
9194 @c OBSOLETE operations where Chill constructs are used (expressions, built in
9195 @c OBSOLETE functions, etc.) in respect to the semantics as defined in the z.200
9196 @c OBSOLETE language specification.
9198 @c OBSOLETE All checks can be disabled by the @value{GDBN} command @code{set check
9202 @c OBSOLETE @c Deviations from the Chill Standard Z200/88
9203 @c OBSOLETE see last paragraph ?
9204 @c OBSOLETE @end ignore
9206 @c OBSOLETE @node Chill defaults
9207 @c OBSOLETE @subsubsection Chill defaults
9209 @c OBSOLETE If type and range checking are set automatically by @value{GDBN}, they
9210 @c OBSOLETE both default to @code{on} whenever the working language changes to
9211 @c OBSOLETE Chill. This happens regardless of whether you or @value{GDBN}
9212 @c OBSOLETE selected the working language.
9214 @c OBSOLETE If you allow @value{GDBN} to set the language automatically, then entering
9215 @c OBSOLETE code compiled from a file whose name ends with @file{.ch} sets the
9216 @c OBSOLETE working language to Chill. @xref{Automatically, ,Having @value{GDBN} set
9217 @c OBSOLETE the language automatically}, for further details.
9220 @chapter Examining the Symbol Table
9222 The commands described in this chapter allow you to inquire about the
9223 symbols (names of variables, functions and types) defined in your
9224 program. This information is inherent in the text of your program and
9225 does not change as your program executes. @value{GDBN} finds it in your
9226 program's symbol table, in the file indicated when you started @value{GDBN}
9227 (@pxref{File Options, ,Choosing files}), or by one of the
9228 file-management commands (@pxref{Files, ,Commands to specify files}).
9230 @cindex symbol names
9231 @cindex names of symbols
9232 @cindex quoting names
9233 Occasionally, you may need to refer to symbols that contain unusual
9234 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9235 most frequent case is in referring to static variables in other
9236 source files (@pxref{Variables,,Program variables}). File names
9237 are recorded in object files as debugging symbols, but @value{GDBN} would
9238 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9239 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9240 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9247 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9250 @kindex info address
9251 @cindex address of a symbol
9252 @item info address @var{symbol}
9253 Describe where the data for @var{symbol} is stored. For a register
9254 variable, this says which register it is kept in. For a non-register
9255 local variable, this prints the stack-frame offset at which the variable
9258 Note the contrast with @samp{print &@var{symbol}}, which does not work
9259 at all for a register variable, and for a stack local variable prints
9260 the exact address of the current instantiation of the variable.
9263 @cindex symbol from address
9264 @item info symbol @var{addr}
9265 Print the name of a symbol which is stored at the address @var{addr}.
9266 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9267 nearest symbol and an offset from it:
9270 (@value{GDBP}) info symbol 0x54320
9271 _initialize_vx + 396 in section .text
9275 This is the opposite of the @code{info address} command. You can use
9276 it to find out the name of a variable or a function given its address.
9279 @item whatis @var{expr}
9280 Print the data type of expression @var{expr}. @var{expr} is not
9281 actually evaluated, and any side-effecting operations (such as
9282 assignments or function calls) inside it do not take place.
9283 @xref{Expressions, ,Expressions}.
9286 Print the data type of @code{$}, the last value in the value history.
9289 @item ptype @var{typename}
9290 Print a description of data type @var{typename}. @var{typename} may be
9291 the name of a type, or for C code it may have the form @samp{class
9292 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9293 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9295 @item ptype @var{expr}
9297 Print a description of the type of expression @var{expr}. @code{ptype}
9298 differs from @code{whatis} by printing a detailed description, instead
9299 of just the name of the type.
9301 For example, for this variable declaration:
9304 struct complex @{double real; double imag;@} v;
9308 the two commands give this output:
9312 (@value{GDBP}) whatis v
9313 type = struct complex
9314 (@value{GDBP}) ptype v
9315 type = struct complex @{
9323 As with @code{whatis}, using @code{ptype} without an argument refers to
9324 the type of @code{$}, the last value in the value history.
9327 @item info types @var{regexp}
9329 Print a brief description of all types whose names match @var{regexp}
9330 (or all types in your program, if you supply no argument). Each
9331 complete typename is matched as though it were a complete line; thus,
9332 @samp{i type value} gives information on all types in your program whose
9333 names include the string @code{value}, but @samp{i type ^value$} gives
9334 information only on types whose complete name is @code{value}.
9336 This command differs from @code{ptype} in two ways: first, like
9337 @code{whatis}, it does not print a detailed description; second, it
9338 lists all source files where a type is defined.
9341 @cindex local variables
9342 @item info scope @var{addr}
9343 List all the variables local to a particular scope. This command
9344 accepts a location---a function name, a source line, or an address
9345 preceded by a @samp{*}, and prints all the variables local to the
9346 scope defined by that location. For example:
9349 (@value{GDBP}) @b{info scope command_line_handler}
9350 Scope for command_line_handler:
9351 Symbol rl is an argument at stack/frame offset 8, length 4.
9352 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9353 Symbol linelength is in static storage at address 0x150a1c, length 4.
9354 Symbol p is a local variable in register $esi, length 4.
9355 Symbol p1 is a local variable in register $ebx, length 4.
9356 Symbol nline is a local variable in register $edx, length 4.
9357 Symbol repeat is a local variable at frame offset -8, length 4.
9361 This command is especially useful for determining what data to collect
9362 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9367 Show information about the current source file---that is, the source file for
9368 the function containing the current point of execution:
9371 the name of the source file, and the directory containing it,
9373 the directory it was compiled in,
9375 its length, in lines,
9377 which programming language it is written in,
9379 whether the executable includes debugging information for that file, and
9380 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9382 whether the debugging information includes information about
9383 preprocessor macros.
9387 @kindex info sources
9389 Print the names of all source files in your program for which there is
9390 debugging information, organized into two lists: files whose symbols
9391 have already been read, and files whose symbols will be read when needed.
9393 @kindex info functions
9394 @item info functions
9395 Print the names and data types of all defined functions.
9397 @item info functions @var{regexp}
9398 Print the names and data types of all defined functions
9399 whose names contain a match for regular expression @var{regexp}.
9400 Thus, @samp{info fun step} finds all functions whose names
9401 include @code{step}; @samp{info fun ^step} finds those whose names
9402 start with @code{step}. If a function name contains characters
9403 that conflict with the regular expression language (eg.
9404 @samp{operator*()}), they may be quoted with a backslash.
9406 @kindex info variables
9407 @item info variables
9408 Print the names and data types of all variables that are declared
9409 outside of functions (i.e.@: excluding local variables).
9411 @item info variables @var{regexp}
9412 Print the names and data types of all variables (except for local
9413 variables) whose names contain a match for regular expression
9417 This was never implemented.
9418 @kindex info methods
9420 @itemx info methods @var{regexp}
9421 The @code{info methods} command permits the user to examine all defined
9422 methods within C@t{++} program, or (with the @var{regexp} argument) a
9423 specific set of methods found in the various C@t{++} classes. Many
9424 C@t{++} classes provide a large number of methods. Thus, the output
9425 from the @code{ptype} command can be overwhelming and hard to use. The
9426 @code{info-methods} command filters the methods, printing only those
9427 which match the regular-expression @var{regexp}.
9430 @cindex reloading symbols
9431 Some systems allow individual object files that make up your program to
9432 be replaced without stopping and restarting your program. For example,
9433 in VxWorks you can simply recompile a defective object file and keep on
9434 running. If you are running on one of these systems, you can allow
9435 @value{GDBN} to reload the symbols for automatically relinked modules:
9438 @kindex set symbol-reloading
9439 @item set symbol-reloading on
9440 Replace symbol definitions for the corresponding source file when an
9441 object file with a particular name is seen again.
9443 @item set symbol-reloading off
9444 Do not replace symbol definitions when encountering object files of the
9445 same name more than once. This is the default state; if you are not
9446 running on a system that permits automatic relinking of modules, you
9447 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9448 may discard symbols when linking large programs, that may contain
9449 several modules (from different directories or libraries) with the same
9452 @kindex show symbol-reloading
9453 @item show symbol-reloading
9454 Show the current @code{on} or @code{off} setting.
9457 @kindex set opaque-type-resolution
9458 @item set opaque-type-resolution on
9459 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9460 declared as a pointer to a @code{struct}, @code{class}, or
9461 @code{union}---for example, @code{struct MyType *}---that is used in one
9462 source file although the full declaration of @code{struct MyType} is in
9463 another source file. The default is on.
9465 A change in the setting of this subcommand will not take effect until
9466 the next time symbols for a file are loaded.
9468 @item set opaque-type-resolution off
9469 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9470 is printed as follows:
9472 @{<no data fields>@}
9475 @kindex show opaque-type-resolution
9476 @item show opaque-type-resolution
9477 Show whether opaque types are resolved or not.
9479 @kindex maint print symbols
9481 @kindex maint print psymbols
9482 @cindex partial symbol dump
9483 @item maint print symbols @var{filename}
9484 @itemx maint print psymbols @var{filename}
9485 @itemx maint print msymbols @var{filename}
9486 Write a dump of debugging symbol data into the file @var{filename}.
9487 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9488 symbols with debugging data are included. If you use @samp{maint print
9489 symbols}, @value{GDBN} includes all the symbols for which it has already
9490 collected full details: that is, @var{filename} reflects symbols for
9491 only those files whose symbols @value{GDBN} has read. You can use the
9492 command @code{info sources} to find out which files these are. If you
9493 use @samp{maint print psymbols} instead, the dump shows information about
9494 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9495 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9496 @samp{maint print msymbols} dumps just the minimal symbol information
9497 required for each object file from which @value{GDBN} has read some symbols.
9498 @xref{Files, ,Commands to specify files}, for a discussion of how
9499 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9503 @chapter Altering Execution
9505 Once you think you have found an error in your program, you might want to
9506 find out for certain whether correcting the apparent error would lead to
9507 correct results in the rest of the run. You can find the answer by
9508 experiment, using the @value{GDBN} features for altering execution of the
9511 For example, you can store new values into variables or memory
9512 locations, give your program a signal, restart it at a different
9513 address, or even return prematurely from a function.
9516 * Assignment:: Assignment to variables
9517 * Jumping:: Continuing at a different address
9518 * Signaling:: Giving your program a signal
9519 * Returning:: Returning from a function
9520 * Calling:: Calling your program's functions
9521 * Patching:: Patching your program
9525 @section Assignment to variables
9528 @cindex setting variables
9529 To alter the value of a variable, evaluate an assignment expression.
9530 @xref{Expressions, ,Expressions}. For example,
9537 stores the value 4 into the variable @code{x}, and then prints the
9538 value of the assignment expression (which is 4).
9539 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9540 information on operators in supported languages.
9542 @kindex set variable
9543 @cindex variables, setting
9544 If you are not interested in seeing the value of the assignment, use the
9545 @code{set} command instead of the @code{print} command. @code{set} is
9546 really the same as @code{print} except that the expression's value is
9547 not printed and is not put in the value history (@pxref{Value History,
9548 ,Value history}). The expression is evaluated only for its effects.
9550 If the beginning of the argument string of the @code{set} command
9551 appears identical to a @code{set} subcommand, use the @code{set
9552 variable} command instead of just @code{set}. This command is identical
9553 to @code{set} except for its lack of subcommands. For example, if your
9554 program has a variable @code{width}, you get an error if you try to set
9555 a new value with just @samp{set width=13}, because @value{GDBN} has the
9556 command @code{set width}:
9559 (@value{GDBP}) whatis width
9561 (@value{GDBP}) p width
9563 (@value{GDBP}) set width=47
9564 Invalid syntax in expression.
9568 The invalid expression, of course, is @samp{=47}. In
9569 order to actually set the program's variable @code{width}, use
9572 (@value{GDBP}) set var width=47
9575 Because the @code{set} command has many subcommands that can conflict
9576 with the names of program variables, it is a good idea to use the
9577 @code{set variable} command instead of just @code{set}. For example, if
9578 your program has a variable @code{g}, you run into problems if you try
9579 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9580 the command @code{set gnutarget}, abbreviated @code{set g}:
9584 (@value{GDBP}) whatis g
9588 (@value{GDBP}) set g=4
9592 The program being debugged has been started already.
9593 Start it from the beginning? (y or n) y
9594 Starting program: /home/smith/cc_progs/a.out
9595 "/home/smith/cc_progs/a.out": can't open to read symbols:
9597 (@value{GDBP}) show g
9598 The current BFD target is "=4".
9603 The program variable @code{g} did not change, and you silently set the
9604 @code{gnutarget} to an invalid value. In order to set the variable
9608 (@value{GDBP}) set var g=4
9611 @value{GDBN} allows more implicit conversions in assignments than C; you can
9612 freely store an integer value into a pointer variable or vice versa,
9613 and you can convert any structure to any other structure that is the
9614 same length or shorter.
9615 @comment FIXME: how do structs align/pad in these conversions?
9616 @comment /doc@cygnus.com 18dec1990
9618 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9619 construct to generate a value of specified type at a specified address
9620 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9621 to memory location @code{0x83040} as an integer (which implies a certain size
9622 and representation in memory), and
9625 set @{int@}0x83040 = 4
9629 stores the value 4 into that memory location.
9632 @section Continuing at a different address
9634 Ordinarily, when you continue your program, you do so at the place where
9635 it stopped, with the @code{continue} command. You can instead continue at
9636 an address of your own choosing, with the following commands:
9640 @item jump @var{linespec}
9641 Resume execution at line @var{linespec}. Execution stops again
9642 immediately if there is a breakpoint there. @xref{List, ,Printing
9643 source lines}, for a description of the different forms of
9644 @var{linespec}. It is common practice to use the @code{tbreak} command
9645 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9648 The @code{jump} command does not change the current stack frame, or
9649 the stack pointer, or the contents of any memory location or any
9650 register other than the program counter. If line @var{linespec} is in
9651 a different function from the one currently executing, the results may
9652 be bizarre if the two functions expect different patterns of arguments or
9653 of local variables. For this reason, the @code{jump} command requests
9654 confirmation if the specified line is not in the function currently
9655 executing. However, even bizarre results are predictable if you are
9656 well acquainted with the machine-language code of your program.
9658 @item jump *@var{address}
9659 Resume execution at the instruction at address @var{address}.
9662 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9663 On many systems, you can get much the same effect as the @code{jump}
9664 command by storing a new value into the register @code{$pc}. The
9665 difference is that this does not start your program running; it only
9666 changes the address of where it @emph{will} run when you continue. For
9674 makes the next @code{continue} command or stepping command execute at
9675 address @code{0x485}, rather than at the address where your program stopped.
9676 @xref{Continuing and Stepping, ,Continuing and stepping}.
9678 The most common occasion to use the @code{jump} command is to back
9679 up---perhaps with more breakpoints set---over a portion of a program
9680 that has already executed, in order to examine its execution in more
9685 @section Giving your program a signal
9689 @item signal @var{signal}
9690 Resume execution where your program stopped, but immediately give it the
9691 signal @var{signal}. @var{signal} can be the name or the number of a
9692 signal. For example, on many systems @code{signal 2} and @code{signal
9693 SIGINT} are both ways of sending an interrupt signal.
9695 Alternatively, if @var{signal} is zero, continue execution without
9696 giving a signal. This is useful when your program stopped on account of
9697 a signal and would ordinary see the signal when resumed with the
9698 @code{continue} command; @samp{signal 0} causes it to resume without a
9701 @code{signal} does not repeat when you press @key{RET} a second time
9702 after executing the command.
9706 Invoking the @code{signal} command is not the same as invoking the
9707 @code{kill} utility from the shell. Sending a signal with @code{kill}
9708 causes @value{GDBN} to decide what to do with the signal depending on
9709 the signal handling tables (@pxref{Signals}). The @code{signal} command
9710 passes the signal directly to your program.
9714 @section Returning from a function
9717 @cindex returning from a function
9720 @itemx return @var{expression}
9721 You can cancel execution of a function call with the @code{return}
9722 command. If you give an
9723 @var{expression} argument, its value is used as the function's return
9727 When you use @code{return}, @value{GDBN} discards the selected stack frame
9728 (and all frames within it). You can think of this as making the
9729 discarded frame return prematurely. If you wish to specify a value to
9730 be returned, give that value as the argument to @code{return}.
9732 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9733 frame}), and any other frames inside of it, leaving its caller as the
9734 innermost remaining frame. That frame becomes selected. The
9735 specified value is stored in the registers used for returning values
9738 The @code{return} command does not resume execution; it leaves the
9739 program stopped in the state that would exist if the function had just
9740 returned. In contrast, the @code{finish} command (@pxref{Continuing
9741 and Stepping, ,Continuing and stepping}) resumes execution until the
9742 selected stack frame returns naturally.
9745 @section Calling program functions
9747 @cindex calling functions
9750 @item call @var{expr}
9751 Evaluate the expression @var{expr} without displaying @code{void}
9755 You can use this variant of the @code{print} command if you want to
9756 execute a function from your program, but without cluttering the output
9757 with @code{void} returned values. If the result is not void, it
9758 is printed and saved in the value history.
9761 @section Patching programs
9763 @cindex patching binaries
9764 @cindex writing into executables
9765 @cindex writing into corefiles
9767 By default, @value{GDBN} opens the file containing your program's
9768 executable code (or the corefile) read-only. This prevents accidental
9769 alterations to machine code; but it also prevents you from intentionally
9770 patching your program's binary.
9772 If you'd like to be able to patch the binary, you can specify that
9773 explicitly with the @code{set write} command. For example, you might
9774 want to turn on internal debugging flags, or even to make emergency
9780 @itemx set write off
9781 If you specify @samp{set write on}, @value{GDBN} opens executable and
9782 core files for both reading and writing; if you specify @samp{set write
9783 off} (the default), @value{GDBN} opens them read-only.
9785 If you have already loaded a file, you must load it again (using the
9786 @code{exec-file} or @code{core-file} command) after changing @code{set
9787 write}, for your new setting to take effect.
9791 Display whether executable files and core files are opened for writing
9796 @chapter @value{GDBN} Files
9798 @value{GDBN} needs to know the file name of the program to be debugged,
9799 both in order to read its symbol table and in order to start your
9800 program. To debug a core dump of a previous run, you must also tell
9801 @value{GDBN} the name of the core dump file.
9804 * Files:: Commands to specify files
9805 * Symbol Errors:: Errors reading symbol files
9809 @section Commands to specify files
9811 @cindex symbol table
9812 @cindex core dump file
9814 You may want to specify executable and core dump file names. The usual
9815 way to do this is at start-up time, using the arguments to
9816 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9817 Out of @value{GDBN}}).
9819 Occasionally it is necessary to change to a different file during a
9820 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9821 a file you want to use. In these situations the @value{GDBN} commands
9822 to specify new files are useful.
9825 @cindex executable file
9827 @item file @var{filename}
9828 Use @var{filename} as the program to be debugged. It is read for its
9829 symbols and for the contents of pure memory. It is also the program
9830 executed when you use the @code{run} command. If you do not specify a
9831 directory and the file is not found in the @value{GDBN} working directory,
9832 @value{GDBN} uses the environment variable @code{PATH} as a list of
9833 directories to search, just as the shell does when looking for a program
9834 to run. You can change the value of this variable, for both @value{GDBN}
9835 and your program, using the @code{path} command.
9837 On systems with memory-mapped files, an auxiliary file named
9838 @file{@var{filename}.syms} may hold symbol table information for
9839 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9840 @file{@var{filename}.syms}, starting up more quickly. See the
9841 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9842 (available on the command line, and with the commands @code{file},
9843 @code{symbol-file}, or @code{add-symbol-file}, described below),
9844 for more information.
9847 @code{file} with no argument makes @value{GDBN} discard any information it
9848 has on both executable file and the symbol table.
9851 @item exec-file @r{[} @var{filename} @r{]}
9852 Specify that the program to be run (but not the symbol table) is found
9853 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9854 if necessary to locate your program. Omitting @var{filename} means to
9855 discard information on the executable file.
9858 @item symbol-file @r{[} @var{filename} @r{]}
9859 Read symbol table information from file @var{filename}. @code{PATH} is
9860 searched when necessary. Use the @code{file} command to get both symbol
9861 table and program to run from the same file.
9863 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9864 program's symbol table.
9866 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9867 of its convenience variables, the value history, and all breakpoints and
9868 auto-display expressions. This is because they may contain pointers to
9869 the internal data recording symbols and data types, which are part of
9870 the old symbol table data being discarded inside @value{GDBN}.
9872 @code{symbol-file} does not repeat if you press @key{RET} again after
9875 When @value{GDBN} is configured for a particular environment, it
9876 understands debugging information in whatever format is the standard
9877 generated for that environment; you may use either a @sc{gnu} compiler, or
9878 other compilers that adhere to the local conventions.
9879 Best results are usually obtained from @sc{gnu} compilers; for example,
9880 using @code{@value{GCC}} you can generate debugging information for
9883 For most kinds of object files, with the exception of old SVR3 systems
9884 using COFF, the @code{symbol-file} command does not normally read the
9885 symbol table in full right away. Instead, it scans the symbol table
9886 quickly to find which source files and which symbols are present. The
9887 details are read later, one source file at a time, as they are needed.
9889 The purpose of this two-stage reading strategy is to make @value{GDBN}
9890 start up faster. For the most part, it is invisible except for
9891 occasional pauses while the symbol table details for a particular source
9892 file are being read. (The @code{set verbose} command can turn these
9893 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9894 warnings and messages}.)
9896 We have not implemented the two-stage strategy for COFF yet. When the
9897 symbol table is stored in COFF format, @code{symbol-file} reads the
9898 symbol table data in full right away. Note that ``stabs-in-COFF''
9899 still does the two-stage strategy, since the debug info is actually
9903 @cindex reading symbols immediately
9904 @cindex symbols, reading immediately
9906 @cindex memory-mapped symbol file
9907 @cindex saving symbol table
9908 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9909 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9910 You can override the @value{GDBN} two-stage strategy for reading symbol
9911 tables by using the @samp{-readnow} option with any of the commands that
9912 load symbol table information, if you want to be sure @value{GDBN} has the
9913 entire symbol table available.
9915 If memory-mapped files are available on your system through the
9916 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9917 cause @value{GDBN} to write the symbols for your program into a reusable
9918 file. Future @value{GDBN} debugging sessions map in symbol information
9919 from this auxiliary symbol file (if the program has not changed), rather
9920 than spending time reading the symbol table from the executable
9921 program. Using the @samp{-mapped} option has the same effect as
9922 starting @value{GDBN} with the @samp{-mapped} command-line option.
9924 You can use both options together, to make sure the auxiliary symbol
9925 file has all the symbol information for your program.
9927 The auxiliary symbol file for a program called @var{myprog} is called
9928 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9929 than the corresponding executable), @value{GDBN} always attempts to use
9930 it when you debug @var{myprog}; no special options or commands are
9933 The @file{.syms} file is specific to the host machine where you run
9934 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9935 symbol table. It cannot be shared across multiple host platforms.
9937 @c FIXME: for now no mention of directories, since this seems to be in
9938 @c flux. 13mar1992 status is that in theory GDB would look either in
9939 @c current dir or in same dir as myprog; but issues like competing
9940 @c GDB's, or clutter in system dirs, mean that in practice right now
9941 @c only current dir is used. FFish says maybe a special GDB hierarchy
9942 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9947 @item core-file @r{[} @var{filename} @r{]}
9948 Specify the whereabouts of a core dump file to be used as the ``contents
9949 of memory''. Traditionally, core files contain only some parts of the
9950 address space of the process that generated them; @value{GDBN} can access the
9951 executable file itself for other parts.
9953 @code{core-file} with no argument specifies that no core file is
9956 Note that the core file is ignored when your program is actually running
9957 under @value{GDBN}. So, if you have been running your program and you
9958 wish to debug a core file instead, you must kill the subprocess in which
9959 the program is running. To do this, use the @code{kill} command
9960 (@pxref{Kill Process, ,Killing the child process}).
9962 @kindex add-symbol-file
9963 @cindex dynamic linking
9964 @item add-symbol-file @var{filename} @var{address}
9965 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9966 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9967 The @code{add-symbol-file} command reads additional symbol table
9968 information from the file @var{filename}. You would use this command
9969 when @var{filename} has been dynamically loaded (by some other means)
9970 into the program that is running. @var{address} should be the memory
9971 address at which the file has been loaded; @value{GDBN} cannot figure
9972 this out for itself. You can additionally specify an arbitrary number
9973 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9974 section name and base address for that section. You can specify any
9975 @var{address} as an expression.
9977 The symbol table of the file @var{filename} is added to the symbol table
9978 originally read with the @code{symbol-file} command. You can use the
9979 @code{add-symbol-file} command any number of times; the new symbol data
9980 thus read keeps adding to the old. To discard all old symbol data
9981 instead, use the @code{symbol-file} command without any arguments.
9983 @cindex relocatable object files, reading symbols from
9984 @cindex object files, relocatable, reading symbols from
9985 @cindex reading symbols from relocatable object files
9986 @cindex symbols, reading from relocatable object files
9987 @cindex @file{.o} files, reading symbols from
9988 Although @var{filename} is typically a shared library file, an
9989 executable file, or some other object file which has been fully
9990 relocated for loading into a process, you can also load symbolic
9991 information from relocatable @file{.o} files, as long as:
9995 the file's symbolic information refers only to linker symbols defined in
9996 that file, not to symbols defined by other object files,
9998 every section the file's symbolic information refers to has actually
9999 been loaded into the inferior, as it appears in the file, and
10001 you can determine the address at which every section was loaded, and
10002 provide these to the @code{add-symbol-file} command.
10006 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10007 relocatable files into an already running program; such systems
10008 typically make the requirements above easy to meet. However, it's
10009 important to recognize that many native systems use complex link
10010 procedures (@code{.linkonce} section factoring and C++ constructor table
10011 assembly, for example) that make the requirements difficult to meet. In
10012 general, one cannot assume that using @code{add-symbol-file} to read a
10013 relocatable object file's symbolic information will have the same effect
10014 as linking the relocatable object file into the program in the normal
10017 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10019 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10020 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10021 table information for @var{filename}.
10023 @kindex add-shared-symbol-file
10024 @item add-shared-symbol-file
10025 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10026 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10027 shared libraries, however if @value{GDBN} does not find yours, you can run
10028 @code{add-shared-symbol-file}. It takes no arguments.
10032 The @code{section} command changes the base address of section SECTION of
10033 the exec file to ADDR. This can be used if the exec file does not contain
10034 section addresses, (such as in the a.out format), or when the addresses
10035 specified in the file itself are wrong. Each section must be changed
10036 separately. The @code{info files} command, described below, lists all
10037 the sections and their addresses.
10040 @kindex info target
10043 @code{info files} and @code{info target} are synonymous; both print the
10044 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10045 including the names of the executable and core dump files currently in
10046 use by @value{GDBN}, and the files from which symbols were loaded. The
10047 command @code{help target} lists all possible targets rather than
10050 @kindex maint info sections
10051 @item maint info sections
10052 Another command that can give you extra information about program sections
10053 is @code{maint info sections}. In addition to the section information
10054 displayed by @code{info files}, this command displays the flags and file
10055 offset of each section in the executable and core dump files. In addition,
10056 @code{maint info sections} provides the following command options (which
10057 may be arbitrarily combined):
10061 Display sections for all loaded object files, including shared libraries.
10062 @item @var{sections}
10063 Display info only for named @var{sections}.
10064 @item @var{section-flags}
10065 Display info only for sections for which @var{section-flags} are true.
10066 The section flags that @value{GDBN} currently knows about are:
10069 Section will have space allocated in the process when loaded.
10070 Set for all sections except those containing debug information.
10072 Section will be loaded from the file into the child process memory.
10073 Set for pre-initialized code and data, clear for @code{.bss} sections.
10075 Section needs to be relocated before loading.
10077 Section cannot be modified by the child process.
10079 Section contains executable code only.
10081 Section contains data only (no executable code).
10083 Section will reside in ROM.
10085 Section contains data for constructor/destructor lists.
10087 Section is not empty.
10089 An instruction to the linker to not output the section.
10090 @item COFF_SHARED_LIBRARY
10091 A notification to the linker that the section contains
10092 COFF shared library information.
10094 Section contains common symbols.
10097 @kindex set trust-readonly-sections
10098 @item set trust-readonly-sections on
10099 Tell @value{GDBN} that readonly sections in your object file
10100 really are read-only (i.e.@: that their contents will not change).
10101 In that case, @value{GDBN} can fetch values from these sections
10102 out of the object file, rather than from the target program.
10103 For some targets (notably embedded ones), this can be a significant
10104 enhancement to debugging performance.
10106 The default is off.
10108 @item set trust-readonly-sections off
10109 Tell @value{GDBN} not to trust readonly sections. This means that
10110 the contents of the section might change while the program is running,
10111 and must therefore be fetched from the target when needed.
10114 All file-specifying commands allow both absolute and relative file names
10115 as arguments. @value{GDBN} always converts the file name to an absolute file
10116 name and remembers it that way.
10118 @cindex shared libraries
10119 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10122 @value{GDBN} automatically loads symbol definitions from shared libraries
10123 when you use the @code{run} command, or when you examine a core file.
10124 (Before you issue the @code{run} command, @value{GDBN} does not understand
10125 references to a function in a shared library, however---unless you are
10126 debugging a core file).
10128 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10129 automatically loads the symbols at the time of the @code{shl_load} call.
10131 @c FIXME: some @value{GDBN} release may permit some refs to undef
10132 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10133 @c FIXME...lib; check this from time to time when updating manual
10135 There are times, however, when you may wish to not automatically load
10136 symbol definitions from shared libraries, such as when they are
10137 particularly large or there are many of them.
10139 To control the automatic loading of shared library symbols, use the
10143 @kindex set auto-solib-add
10144 @item set auto-solib-add @var{mode}
10145 If @var{mode} is @code{on}, symbols from all shared object libraries
10146 will be loaded automatically when the inferior begins execution, you
10147 attach to an independently started inferior, or when the dynamic linker
10148 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10149 is @code{off}, symbols must be loaded manually, using the
10150 @code{sharedlibrary} command. The default value is @code{on}.
10152 @kindex show auto-solib-add
10153 @item show auto-solib-add
10154 Display the current autoloading mode.
10157 To explicitly load shared library symbols, use the @code{sharedlibrary}
10161 @kindex info sharedlibrary
10164 @itemx info sharedlibrary
10165 Print the names of the shared libraries which are currently loaded.
10167 @kindex sharedlibrary
10169 @item sharedlibrary @var{regex}
10170 @itemx share @var{regex}
10171 Load shared object library symbols for files matching a
10172 Unix regular expression.
10173 As with files loaded automatically, it only loads shared libraries
10174 required by your program for a core file or after typing @code{run}. If
10175 @var{regex} is omitted all shared libraries required by your program are
10179 On some systems, such as HP-UX systems, @value{GDBN} supports
10180 autoloading shared library symbols until a limiting threshold size is
10181 reached. This provides the benefit of allowing autoloading to remain on
10182 by default, but avoids autoloading excessively large shared libraries,
10183 up to a threshold that is initially set, but which you can modify if you
10186 Beyond that threshold, symbols from shared libraries must be explicitly
10187 loaded. To load these symbols, use the command @code{sharedlibrary
10188 @var{filename}}. The base address of the shared library is determined
10189 automatically by @value{GDBN} and need not be specified.
10191 To display or set the threshold, use the commands:
10194 @kindex set auto-solib-limit
10195 @item set auto-solib-limit @var{threshold}
10196 Set the autoloading size threshold, in an integral number of megabytes.
10197 If @var{threshold} is nonzero and shared library autoloading is enabled,
10198 symbols from all shared object libraries will be loaded until the total
10199 size of the loaded shared library symbols exceeds this threshold.
10200 Otherwise, symbols must be loaded manually, using the
10201 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10204 @kindex show auto-solib-limit
10205 @item show auto-solib-limit
10206 Display the current autoloading size threshold, in megabytes.
10209 @node Symbol Errors
10210 @section Errors reading symbol files
10212 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10213 such as symbol types it does not recognize, or known bugs in compiler
10214 output. By default, @value{GDBN} does not notify you of such problems, since
10215 they are relatively common and primarily of interest to people
10216 debugging compilers. If you are interested in seeing information
10217 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10218 only one message about each such type of problem, no matter how many
10219 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10220 to see how many times the problems occur, with the @code{set
10221 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10224 The messages currently printed, and their meanings, include:
10227 @item inner block not inside outer block in @var{symbol}
10229 The symbol information shows where symbol scopes begin and end
10230 (such as at the start of a function or a block of statements). This
10231 error indicates that an inner scope block is not fully contained
10232 in its outer scope blocks.
10234 @value{GDBN} circumvents the problem by treating the inner block as if it had
10235 the same scope as the outer block. In the error message, @var{symbol}
10236 may be shown as ``@code{(don't know)}'' if the outer block is not a
10239 @item block at @var{address} out of order
10241 The symbol information for symbol scope blocks should occur in
10242 order of increasing addresses. This error indicates that it does not
10245 @value{GDBN} does not circumvent this problem, and has trouble
10246 locating symbols in the source file whose symbols it is reading. (You
10247 can often determine what source file is affected by specifying
10248 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10251 @item bad block start address patched
10253 The symbol information for a symbol scope block has a start address
10254 smaller than the address of the preceding source line. This is known
10255 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10257 @value{GDBN} circumvents the problem by treating the symbol scope block as
10258 starting on the previous source line.
10260 @item bad string table offset in symbol @var{n}
10263 Symbol number @var{n} contains a pointer into the string table which is
10264 larger than the size of the string table.
10266 @value{GDBN} circumvents the problem by considering the symbol to have the
10267 name @code{foo}, which may cause other problems if many symbols end up
10270 @item unknown symbol type @code{0x@var{nn}}
10272 The symbol information contains new data types that @value{GDBN} does
10273 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10274 uncomprehended information, in hexadecimal.
10276 @value{GDBN} circumvents the error by ignoring this symbol information.
10277 This usually allows you to debug your program, though certain symbols
10278 are not accessible. If you encounter such a problem and feel like
10279 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10280 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10281 and examine @code{*bufp} to see the symbol.
10283 @item stub type has NULL name
10285 @value{GDBN} could not find the full definition for a struct or class.
10287 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10288 The symbol information for a C@t{++} member function is missing some
10289 information that recent versions of the compiler should have output for
10292 @item info mismatch between compiler and debugger
10294 @value{GDBN} could not parse a type specification output by the compiler.
10299 @chapter Specifying a Debugging Target
10301 @cindex debugging target
10304 A @dfn{target} is the execution environment occupied by your program.
10306 Often, @value{GDBN} runs in the same host environment as your program;
10307 in that case, the debugging target is specified as a side effect when
10308 you use the @code{file} or @code{core} commands. When you need more
10309 flexibility---for example, running @value{GDBN} on a physically separate
10310 host, or controlling a standalone system over a serial port or a
10311 realtime system over a TCP/IP connection---you can use the @code{target}
10312 command to specify one of the target types configured for @value{GDBN}
10313 (@pxref{Target Commands, ,Commands for managing targets}).
10316 * Active Targets:: Active targets
10317 * Target Commands:: Commands for managing targets
10318 * Byte Order:: Choosing target byte order
10319 * Remote:: Remote debugging
10320 * KOD:: Kernel Object Display
10324 @node Active Targets
10325 @section Active targets
10327 @cindex stacking targets
10328 @cindex active targets
10329 @cindex multiple targets
10331 There are three classes of targets: processes, core files, and
10332 executable files. @value{GDBN} can work concurrently on up to three
10333 active targets, one in each class. This allows you to (for example)
10334 start a process and inspect its activity without abandoning your work on
10337 For example, if you execute @samp{gdb a.out}, then the executable file
10338 @code{a.out} is the only active target. If you designate a core file as
10339 well---presumably from a prior run that crashed and coredumped---then
10340 @value{GDBN} has two active targets and uses them in tandem, looking
10341 first in the corefile target, then in the executable file, to satisfy
10342 requests for memory addresses. (Typically, these two classes of target
10343 are complementary, since core files contain only a program's
10344 read-write memory---variables and so on---plus machine status, while
10345 executable files contain only the program text and initialized data.)
10347 When you type @code{run}, your executable file becomes an active process
10348 target as well. When a process target is active, all @value{GDBN}
10349 commands requesting memory addresses refer to that target; addresses in
10350 an active core file or executable file target are obscured while the
10351 process target is active.
10353 Use the @code{core-file} and @code{exec-file} commands to select a new
10354 core file or executable target (@pxref{Files, ,Commands to specify
10355 files}). To specify as a target a process that is already running, use
10356 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10359 @node Target Commands
10360 @section Commands for managing targets
10363 @item target @var{type} @var{parameters}
10364 Connects the @value{GDBN} host environment to a target machine or
10365 process. A target is typically a protocol for talking to debugging
10366 facilities. You use the argument @var{type} to specify the type or
10367 protocol of the target machine.
10369 Further @var{parameters} are interpreted by the target protocol, but
10370 typically include things like device names or host names to connect
10371 with, process numbers, and baud rates.
10373 The @code{target} command does not repeat if you press @key{RET} again
10374 after executing the command.
10376 @kindex help target
10378 Displays the names of all targets available. To display targets
10379 currently selected, use either @code{info target} or @code{info files}
10380 (@pxref{Files, ,Commands to specify files}).
10382 @item help target @var{name}
10383 Describe a particular target, including any parameters necessary to
10386 @kindex set gnutarget
10387 @item set gnutarget @var{args}
10388 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10389 knows whether it is reading an @dfn{executable},
10390 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10391 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10392 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10395 @emph{Warning:} To specify a file format with @code{set gnutarget},
10396 you must know the actual BFD name.
10400 @xref{Files, , Commands to specify files}.
10402 @kindex show gnutarget
10403 @item show gnutarget
10404 Use the @code{show gnutarget} command to display what file format
10405 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10406 @value{GDBN} will determine the file format for each file automatically,
10407 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10410 Here are some common targets (available, or not, depending on the GDB
10414 @kindex target exec
10415 @item target exec @var{program}
10416 An executable file. @samp{target exec @var{program}} is the same as
10417 @samp{exec-file @var{program}}.
10419 @kindex target core
10420 @item target core @var{filename}
10421 A core dump file. @samp{target core @var{filename}} is the same as
10422 @samp{core-file @var{filename}}.
10424 @kindex target remote
10425 @item target remote @var{dev}
10426 Remote serial target in GDB-specific protocol. The argument @var{dev}
10427 specifies what serial device to use for the connection (e.g.
10428 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10429 supports the @code{load} command. This is only useful if you have
10430 some other way of getting the stub to the target system, and you can put
10431 it somewhere in memory where it won't get clobbered by the download.
10435 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10443 works; however, you cannot assume that a specific memory map, device
10444 drivers, or even basic I/O is available, although some simulators do
10445 provide these. For info about any processor-specific simulator details,
10446 see the appropriate section in @ref{Embedded Processors, ,Embedded
10451 Some configurations may include these targets as well:
10455 @kindex target nrom
10456 @item target nrom @var{dev}
10457 NetROM ROM emulator. This target only supports downloading.
10461 Different targets are available on different configurations of @value{GDBN};
10462 your configuration may have more or fewer targets.
10464 Many remote targets require you to download the executable's code
10465 once you've successfully established a connection.
10469 @kindex load @var{filename}
10470 @item load @var{filename}
10471 Depending on what remote debugging facilities are configured into
10472 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10473 is meant to make @var{filename} (an executable) available for debugging
10474 on the remote system---by downloading, or dynamic linking, for example.
10475 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10476 the @code{add-symbol-file} command.
10478 If your @value{GDBN} does not have a @code{load} command, attempting to
10479 execute it gets the error message ``@code{You can't do that when your
10480 target is @dots{}}''
10482 The file is loaded at whatever address is specified in the executable.
10483 For some object file formats, you can specify the load address when you
10484 link the program; for other formats, like a.out, the object file format
10485 specifies a fixed address.
10486 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10488 @code{load} does not repeat if you press @key{RET} again after using it.
10492 @section Choosing target byte order
10494 @cindex choosing target byte order
10495 @cindex target byte order
10497 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10498 offer the ability to run either big-endian or little-endian byte
10499 orders. Usually the executable or symbol will include a bit to
10500 designate the endian-ness, and you will not need to worry about
10501 which to use. However, you may still find it useful to adjust
10502 @value{GDBN}'s idea of processor endian-ness manually.
10505 @kindex set endian big
10506 @item set endian big
10507 Instruct @value{GDBN} to assume the target is big-endian.
10509 @kindex set endian little
10510 @item set endian little
10511 Instruct @value{GDBN} to assume the target is little-endian.
10513 @kindex set endian auto
10514 @item set endian auto
10515 Instruct @value{GDBN} to use the byte order associated with the
10519 Display @value{GDBN}'s current idea of the target byte order.
10523 Note that these commands merely adjust interpretation of symbolic
10524 data on the host, and that they have absolutely no effect on the
10528 @section Remote debugging
10529 @cindex remote debugging
10531 If you are trying to debug a program running on a machine that cannot run
10532 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10533 For example, you might use remote debugging on an operating system kernel,
10534 or on a small system which does not have a general purpose operating system
10535 powerful enough to run a full-featured debugger.
10537 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10538 to make this work with particular debugging targets. In addition,
10539 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10540 but not specific to any particular target system) which you can use if you
10541 write the remote stubs---the code that runs on the remote system to
10542 communicate with @value{GDBN}.
10544 Other remote targets may be available in your
10545 configuration of @value{GDBN}; use @code{help target} to list them.
10548 @section Kernel Object Display
10550 @cindex kernel object display
10551 @cindex kernel object
10554 Some targets support kernel object display. Using this facility,
10555 @value{GDBN} communicates specially with the underlying operating system
10556 and can display information about operating system-level objects such as
10557 mutexes and other synchronization objects. Exactly which objects can be
10558 displayed is determined on a per-OS basis.
10560 Use the @code{set os} command to set the operating system. This tells
10561 @value{GDBN} which kernel object display module to initialize:
10564 (@value{GDBP}) set os cisco
10567 If @code{set os} succeeds, @value{GDBN} will display some information
10568 about the operating system, and will create a new @code{info} command
10569 which can be used to query the target. The @code{info} command is named
10570 after the operating system:
10573 (@value{GDBP}) info cisco
10574 List of Cisco Kernel Objects
10576 any Any and all objects
10579 Further subcommands can be used to query about particular objects known
10582 There is currently no way to determine whether a given operating system
10583 is supported other than to try it.
10586 @node Remote Debugging
10587 @chapter Debugging remote programs
10590 * Server:: Using the gdbserver program
10591 * NetWare:: Using the gdbserve.nlm program
10592 * remote stub:: Implementing a remote stub
10596 @section Using the @code{gdbserver} program
10599 @cindex remote connection without stubs
10600 @code{gdbserver} is a control program for Unix-like systems, which
10601 allows you to connect your program with a remote @value{GDBN} via
10602 @code{target remote}---but without linking in the usual debugging stub.
10604 @code{gdbserver} is not a complete replacement for the debugging stubs,
10605 because it requires essentially the same operating-system facilities
10606 that @value{GDBN} itself does. In fact, a system that can run
10607 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10608 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10609 because it is a much smaller program than @value{GDBN} itself. It is
10610 also easier to port than all of @value{GDBN}, so you may be able to get
10611 started more quickly on a new system by using @code{gdbserver}.
10612 Finally, if you develop code for real-time systems, you may find that
10613 the tradeoffs involved in real-time operation make it more convenient to
10614 do as much development work as possible on another system, for example
10615 by cross-compiling. You can use @code{gdbserver} to make a similar
10616 choice for debugging.
10618 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10619 or a TCP connection, using the standard @value{GDBN} remote serial
10623 @item On the target machine,
10624 you need to have a copy of the program you want to debug.
10625 @code{gdbserver} does not need your program's symbol table, so you can
10626 strip the program if necessary to save space. @value{GDBN} on the host
10627 system does all the symbol handling.
10629 To use the server, you must tell it how to communicate with @value{GDBN};
10630 the name of your program; and the arguments for your program. The usual
10634 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10637 @var{comm} is either a device name (to use a serial line) or a TCP
10638 hostname and portnumber. For example, to debug Emacs with the argument
10639 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10643 target> gdbserver /dev/com1 emacs foo.txt
10646 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10649 To use a TCP connection instead of a serial line:
10652 target> gdbserver host:2345 emacs foo.txt
10655 The only difference from the previous example is the first argument,
10656 specifying that you are communicating with the host @value{GDBN} via
10657 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10658 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10659 (Currently, the @samp{host} part is ignored.) You can choose any number
10660 you want for the port number as long as it does not conflict with any
10661 TCP ports already in use on the target system (for example, @code{23} is
10662 reserved for @code{telnet}).@footnote{If you choose a port number that
10663 conflicts with another service, @code{gdbserver} prints an error message
10664 and exits.} You must use the same port number with the host @value{GDBN}
10665 @code{target remote} command.
10667 On some targets, @code{gdbserver} can also attach to running programs.
10668 This is accomplished via the @code{--attach} argument. The syntax is:
10671 target> gdbserver @var{comm} --attach @var{pid}
10674 @var{pid} is the process ID of a currently running process. It isn't necessary
10675 to point @code{gdbserver} at a binary for the running process.
10677 @item On the @value{GDBN} host machine,
10678 you need an unstripped copy of your program, since @value{GDBN} needs
10679 symbols and debugging information. Start up @value{GDBN} as usual,
10680 using the name of the local copy of your program as the first argument.
10681 (You may also need the @w{@samp{--baud}} option if the serial line is
10682 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10683 remote} to establish communications with @code{gdbserver}. Its argument
10684 is either a device name (usually a serial device, like
10685 @file{/dev/ttyb}), or a TCP port descriptor in the form
10686 @code{@var{host}:@var{PORT}}. For example:
10689 (@value{GDBP}) target remote /dev/ttyb
10693 communicates with the server via serial line @file{/dev/ttyb}, and
10696 (@value{GDBP}) target remote the-target:2345
10700 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10701 For TCP connections, you must start up @code{gdbserver} prior to using
10702 the @code{target remote} command. Otherwise you may get an error whose
10703 text depends on the host system, but which usually looks something like
10704 @samp{Connection refused}.
10708 @section Using the @code{gdbserve.nlm} program
10710 @kindex gdbserve.nlm
10711 @code{gdbserve.nlm} is a control program for NetWare systems, which
10712 allows you to connect your program with a remote @value{GDBN} via
10713 @code{target remote}.
10715 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10716 using the standard @value{GDBN} remote serial protocol.
10719 @item On the target machine,
10720 you need to have a copy of the program you want to debug.
10721 @code{gdbserve.nlm} does not need your program's symbol table, so you
10722 can strip the program if necessary to save space. @value{GDBN} on the
10723 host system does all the symbol handling.
10725 To use the server, you must tell it how to communicate with
10726 @value{GDBN}; the name of your program; and the arguments for your
10727 program. The syntax is:
10730 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10731 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10734 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10735 the baud rate used by the connection. @var{port} and @var{node} default
10736 to 0, @var{baud} defaults to 9600@dmn{bps}.
10738 For example, to debug Emacs with the argument @samp{foo.txt}and
10739 communicate with @value{GDBN} over serial port number 2 or board 1
10740 using a 19200@dmn{bps} connection:
10743 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10746 @item On the @value{GDBN} host machine,
10747 you need an unstripped copy of your program, since @value{GDBN} needs
10748 symbols and debugging information. Start up @value{GDBN} as usual,
10749 using the name of the local copy of your program as the first argument.
10750 (You may also need the @w{@samp{--baud}} option if the serial line is
10751 running at anything other than 9600@dmn{bps}. After that, use @code{target
10752 remote} to establish communications with @code{gdbserve.nlm}. Its
10753 argument is a device name (usually a serial device, like
10754 @file{/dev/ttyb}). For example:
10757 (@value{GDBP}) target remote /dev/ttyb
10761 communications with the server via serial line @file{/dev/ttyb}.
10765 @section Implementing a remote stub
10767 @cindex debugging stub, example
10768 @cindex remote stub, example
10769 @cindex stub example, remote debugging
10770 The stub files provided with @value{GDBN} implement the target side of the
10771 communication protocol, and the @value{GDBN} side is implemented in the
10772 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10773 these subroutines to communicate, and ignore the details. (If you're
10774 implementing your own stub file, you can still ignore the details: start
10775 with one of the existing stub files. @file{sparc-stub.c} is the best
10776 organized, and therefore the easiest to read.)
10778 @cindex remote serial debugging, overview
10779 To debug a program running on another machine (the debugging
10780 @dfn{target} machine), you must first arrange for all the usual
10781 prerequisites for the program to run by itself. For example, for a C
10786 A startup routine to set up the C runtime environment; these usually
10787 have a name like @file{crt0}. The startup routine may be supplied by
10788 your hardware supplier, or you may have to write your own.
10791 A C subroutine library to support your program's
10792 subroutine calls, notably managing input and output.
10795 A way of getting your program to the other machine---for example, a
10796 download program. These are often supplied by the hardware
10797 manufacturer, but you may have to write your own from hardware
10801 The next step is to arrange for your program to use a serial port to
10802 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10803 machine). In general terms, the scheme looks like this:
10807 @value{GDBN} already understands how to use this protocol; when everything
10808 else is set up, you can simply use the @samp{target remote} command
10809 (@pxref{Targets,,Specifying a Debugging Target}).
10811 @item On the target,
10812 you must link with your program a few special-purpose subroutines that
10813 implement the @value{GDBN} remote serial protocol. The file containing these
10814 subroutines is called a @dfn{debugging stub}.
10816 On certain remote targets, you can use an auxiliary program
10817 @code{gdbserver} instead of linking a stub into your program.
10818 @xref{Server,,Using the @code{gdbserver} program}, for details.
10821 The debugging stub is specific to the architecture of the remote
10822 machine; for example, use @file{sparc-stub.c} to debug programs on
10825 @cindex remote serial stub list
10826 These working remote stubs are distributed with @value{GDBN}:
10831 @cindex @file{i386-stub.c}
10834 For Intel 386 and compatible architectures.
10837 @cindex @file{m68k-stub.c}
10838 @cindex Motorola 680x0
10840 For Motorola 680x0 architectures.
10843 @cindex @file{sh-stub.c}
10846 For Hitachi SH architectures.
10849 @cindex @file{sparc-stub.c}
10851 For @sc{sparc} architectures.
10853 @item sparcl-stub.c
10854 @cindex @file{sparcl-stub.c}
10857 For Fujitsu @sc{sparclite} architectures.
10861 The @file{README} file in the @value{GDBN} distribution may list other
10862 recently added stubs.
10865 * Stub Contents:: What the stub can do for you
10866 * Bootstrapping:: What you must do for the stub
10867 * Debug Session:: Putting it all together
10870 @node Stub Contents
10871 @subsection What the stub can do for you
10873 @cindex remote serial stub
10874 The debugging stub for your architecture supplies these three
10878 @item set_debug_traps
10879 @kindex set_debug_traps
10880 @cindex remote serial stub, initialization
10881 This routine arranges for @code{handle_exception} to run when your
10882 program stops. You must call this subroutine explicitly near the
10883 beginning of your program.
10885 @item handle_exception
10886 @kindex handle_exception
10887 @cindex remote serial stub, main routine
10888 This is the central workhorse, but your program never calls it
10889 explicitly---the setup code arranges for @code{handle_exception} to
10890 run when a trap is triggered.
10892 @code{handle_exception} takes control when your program stops during
10893 execution (for example, on a breakpoint), and mediates communications
10894 with @value{GDBN} on the host machine. This is where the communications
10895 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10896 representative on the target machine. It begins by sending summary
10897 information on the state of your program, then continues to execute,
10898 retrieving and transmitting any information @value{GDBN} needs, until you
10899 execute a @value{GDBN} command that makes your program resume; at that point,
10900 @code{handle_exception} returns control to your own code on the target
10904 @cindex @code{breakpoint} subroutine, remote
10905 Use this auxiliary subroutine to make your program contain a
10906 breakpoint. Depending on the particular situation, this may be the only
10907 way for @value{GDBN} to get control. For instance, if your target
10908 machine has some sort of interrupt button, you won't need to call this;
10909 pressing the interrupt button transfers control to
10910 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10911 simply receiving characters on the serial port may also trigger a trap;
10912 again, in that situation, you don't need to call @code{breakpoint} from
10913 your own program---simply running @samp{target remote} from the host
10914 @value{GDBN} session gets control.
10916 Call @code{breakpoint} if none of these is true, or if you simply want
10917 to make certain your program stops at a predetermined point for the
10918 start of your debugging session.
10921 @node Bootstrapping
10922 @subsection What you must do for the stub
10924 @cindex remote stub, support routines
10925 The debugging stubs that come with @value{GDBN} are set up for a particular
10926 chip architecture, but they have no information about the rest of your
10927 debugging target machine.
10929 First of all you need to tell the stub how to communicate with the
10933 @item int getDebugChar()
10934 @kindex getDebugChar
10935 Write this subroutine to read a single character from the serial port.
10936 It may be identical to @code{getchar} for your target system; a
10937 different name is used to allow you to distinguish the two if you wish.
10939 @item void putDebugChar(int)
10940 @kindex putDebugChar
10941 Write this subroutine to write a single character to the serial port.
10942 It may be identical to @code{putchar} for your target system; a
10943 different name is used to allow you to distinguish the two if you wish.
10946 @cindex control C, and remote debugging
10947 @cindex interrupting remote targets
10948 If you want @value{GDBN} to be able to stop your program while it is
10949 running, you need to use an interrupt-driven serial driver, and arrange
10950 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10951 character). That is the character which @value{GDBN} uses to tell the
10952 remote system to stop.
10954 Getting the debugging target to return the proper status to @value{GDBN}
10955 probably requires changes to the standard stub; one quick and dirty way
10956 is to just execute a breakpoint instruction (the ``dirty'' part is that
10957 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10959 Other routines you need to supply are:
10962 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10963 @kindex exceptionHandler
10964 Write this function to install @var{exception_address} in the exception
10965 handling tables. You need to do this because the stub does not have any
10966 way of knowing what the exception handling tables on your target system
10967 are like (for example, the processor's table might be in @sc{rom},
10968 containing entries which point to a table in @sc{ram}).
10969 @var{exception_number} is the exception number which should be changed;
10970 its meaning is architecture-dependent (for example, different numbers
10971 might represent divide by zero, misaligned access, etc). When this
10972 exception occurs, control should be transferred directly to
10973 @var{exception_address}, and the processor state (stack, registers,
10974 and so on) should be just as it is when a processor exception occurs. So if
10975 you want to use a jump instruction to reach @var{exception_address}, it
10976 should be a simple jump, not a jump to subroutine.
10978 For the 386, @var{exception_address} should be installed as an interrupt
10979 gate so that interrupts are masked while the handler runs. The gate
10980 should be at privilege level 0 (the most privileged level). The
10981 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10982 help from @code{exceptionHandler}.
10984 @item void flush_i_cache()
10985 @kindex flush_i_cache
10986 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10987 instruction cache, if any, on your target machine. If there is no
10988 instruction cache, this subroutine may be a no-op.
10990 On target machines that have instruction caches, @value{GDBN} requires this
10991 function to make certain that the state of your program is stable.
10995 You must also make sure this library routine is available:
10998 @item void *memset(void *, int, int)
11000 This is the standard library function @code{memset} that sets an area of
11001 memory to a known value. If you have one of the free versions of
11002 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11003 either obtain it from your hardware manufacturer, or write your own.
11006 If you do not use the GNU C compiler, you may need other standard
11007 library subroutines as well; this varies from one stub to another,
11008 but in general the stubs are likely to use any of the common library
11009 subroutines which @code{@value{GCC}} generates as inline code.
11012 @node Debug Session
11013 @subsection Putting it all together
11015 @cindex remote serial debugging summary
11016 In summary, when your program is ready to debug, you must follow these
11021 Make sure you have defined the supporting low-level routines
11022 (@pxref{Bootstrapping,,What you must do for the stub}):
11024 @code{getDebugChar}, @code{putDebugChar},
11025 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11029 Insert these lines near the top of your program:
11037 For the 680x0 stub only, you need to provide a variable called
11038 @code{exceptionHook}. Normally you just use:
11041 void (*exceptionHook)() = 0;
11045 but if before calling @code{set_debug_traps}, you set it to point to a
11046 function in your program, that function is called when
11047 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11048 error). The function indicated by @code{exceptionHook} is called with
11049 one parameter: an @code{int} which is the exception number.
11052 Compile and link together: your program, the @value{GDBN} debugging stub for
11053 your target architecture, and the supporting subroutines.
11056 Make sure you have a serial connection between your target machine and
11057 the @value{GDBN} host, and identify the serial port on the host.
11060 @c The "remote" target now provides a `load' command, so we should
11061 @c document that. FIXME.
11062 Download your program to your target machine (or get it there by
11063 whatever means the manufacturer provides), and start it.
11066 To start remote debugging, run @value{GDBN} on the host machine, and specify
11067 as an executable file the program that is running in the remote machine.
11068 This tells @value{GDBN} how to find your program's symbols and the contents
11072 @cindex serial line, @code{target remote}
11073 Establish communication using the @code{target remote} command.
11074 Its argument specifies how to communicate with the target
11075 machine---either via a devicename attached to a direct serial line, or a
11076 TCP or UDP port (usually to a terminal server which in turn has a serial line
11077 to the target). For example, to use a serial line connected to the
11078 device named @file{/dev/ttyb}:
11081 target remote /dev/ttyb
11084 @cindex TCP port, @code{target remote}
11085 To use a TCP connection, use an argument of the form
11086 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11087 For example, to connect to port 2828 on a
11088 terminal server named @code{manyfarms}:
11091 target remote manyfarms:2828
11094 If your remote target is actually running on the same machine as
11095 your debugger session (e.g.@: a simulator of your target running on
11096 the same host), you can omit the hostname. For example, to connect
11097 to port 1234 on your local machine:
11100 target remote :1234
11104 Note that the colon is still required here.
11106 @cindex UDP port, @code{target remote}
11107 To use a UDP connection, use an argument of the form
11108 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11109 on a terminal server named @code{manyfarms}:
11112 target remote udp:manyfarms:2828
11115 When using a UDP connection for remote debugging, you should keep in mind
11116 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11117 busy or unreliable networks, which will cause havoc with your debugging
11122 Now you can use all the usual commands to examine and change data and to
11123 step and continue the remote program.
11125 To resume the remote program and stop debugging it, use the @code{detach}
11128 @cindex interrupting remote programs
11129 @cindex remote programs, interrupting
11130 Whenever @value{GDBN} is waiting for the remote program, if you type the
11131 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11132 program. This may or may not succeed, depending in part on the hardware
11133 and the serial drivers the remote system uses. If you type the
11134 interrupt character once again, @value{GDBN} displays this prompt:
11137 Interrupted while waiting for the program.
11138 Give up (and stop debugging it)? (y or n)
11141 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11142 (If you decide you want to try again later, you can use @samp{target
11143 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11144 goes back to waiting.
11147 @node Configurations
11148 @chapter Configuration-Specific Information
11150 While nearly all @value{GDBN} commands are available for all native and
11151 cross versions of the debugger, there are some exceptions. This chapter
11152 describes things that are only available in certain configurations.
11154 There are three major categories of configurations: native
11155 configurations, where the host and target are the same, embedded
11156 operating system configurations, which are usually the same for several
11157 different processor architectures, and bare embedded processors, which
11158 are quite different from each other.
11163 * Embedded Processors::
11170 This section describes details specific to particular native
11175 * SVR4 Process Information:: SVR4 process information
11176 * DJGPP Native:: Features specific to the DJGPP port
11177 * Cygwin Native:: Features specific to the Cygwin port
11183 On HP-UX systems, if you refer to a function or variable name that
11184 begins with a dollar sign, @value{GDBN} searches for a user or system
11185 name first, before it searches for a convenience variable.
11187 @node SVR4 Process Information
11188 @subsection SVR4 process information
11191 @cindex process image
11193 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11194 used to examine the image of a running process using file-system
11195 subroutines. If @value{GDBN} is configured for an operating system with
11196 this facility, the command @code{info proc} is available to report on
11197 several kinds of information about the process running your program.
11198 @code{info proc} works only on SVR4 systems that include the
11199 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11200 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11205 Summarize available information about the process.
11207 @kindex info proc mappings
11208 @item info proc mappings
11209 Report on the address ranges accessible in the program, with information
11210 on whether your program may read, write, or execute each range.
11212 @comment These sub-options of 'info proc' were not included when
11213 @comment procfs.c was re-written. Keep their descriptions around
11214 @comment against the day when someone finds the time to put them back in.
11215 @kindex info proc times
11216 @item info proc times
11217 Starting time, user CPU time, and system CPU time for your program and
11220 @kindex info proc id
11222 Report on the process IDs related to your program: its own process ID,
11223 the ID of its parent, the process group ID, and the session ID.
11225 @kindex info proc status
11226 @item info proc status
11227 General information on the state of the process. If the process is
11228 stopped, this report includes the reason for stopping, and any signal
11231 @item info proc all
11232 Show all the above information about the process.
11237 @subsection Features for Debugging @sc{djgpp} Programs
11238 @cindex @sc{djgpp} debugging
11239 @cindex native @sc{djgpp} debugging
11240 @cindex MS-DOS-specific commands
11242 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11243 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11244 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11245 top of real-mode DOS systems and their emulations.
11247 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11248 defines a few commands specific to the @sc{djgpp} port. This
11249 subsection describes those commands.
11254 This is a prefix of @sc{djgpp}-specific commands which print
11255 information about the target system and important OS structures.
11258 @cindex MS-DOS system info
11259 @cindex free memory information (MS-DOS)
11260 @item info dos sysinfo
11261 This command displays assorted information about the underlying
11262 platform: the CPU type and features, the OS version and flavor, the
11263 DPMI version, and the available conventional and DPMI memory.
11268 @cindex segment descriptor tables
11269 @cindex descriptor tables display
11271 @itemx info dos ldt
11272 @itemx info dos idt
11273 These 3 commands display entries from, respectively, Global, Local,
11274 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11275 tables are data structures which store a descriptor for each segment
11276 that is currently in use. The segment's selector is an index into a
11277 descriptor table; the table entry for that index holds the
11278 descriptor's base address and limit, and its attributes and access
11281 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11282 segment (used for both data and the stack), and a DOS segment (which
11283 allows access to DOS/BIOS data structures and absolute addresses in
11284 conventional memory). However, the DPMI host will usually define
11285 additional segments in order to support the DPMI environment.
11287 @cindex garbled pointers
11288 These commands allow to display entries from the descriptor tables.
11289 Without an argument, all entries from the specified table are
11290 displayed. An argument, which should be an integer expression, means
11291 display a single entry whose index is given by the argument. For
11292 example, here's a convenient way to display information about the
11293 debugged program's data segment:
11296 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11297 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11301 This comes in handy when you want to see whether a pointer is outside
11302 the data segment's limit (i.e.@: @dfn{garbled}).
11304 @cindex page tables display (MS-DOS)
11306 @itemx info dos pte
11307 These two commands display entries from, respectively, the Page
11308 Directory and the Page Tables. Page Directories and Page Tables are
11309 data structures which control how virtual memory addresses are mapped
11310 into physical addresses. A Page Table includes an entry for every
11311 page of memory that is mapped into the program's address space; there
11312 may be several Page Tables, each one holding up to 4096 entries. A
11313 Page Directory has up to 4096 entries, one each for every Page Table
11314 that is currently in use.
11316 Without an argument, @kbd{info dos pde} displays the entire Page
11317 Directory, and @kbd{info dos pte} displays all the entries in all of
11318 the Page Tables. An argument, an integer expression, given to the
11319 @kbd{info dos pde} command means display only that entry from the Page
11320 Directory table. An argument given to the @kbd{info dos pte} command
11321 means display entries from a single Page Table, the one pointed to by
11322 the specified entry in the Page Directory.
11324 @cindex direct memory access (DMA) on MS-DOS
11325 These commands are useful when your program uses @dfn{DMA} (Direct
11326 Memory Access), which needs physical addresses to program the DMA
11329 These commands are supported only with some DPMI servers.
11331 @cindex physical address from linear address
11332 @item info dos address-pte @var{addr}
11333 This command displays the Page Table entry for a specified linear
11334 address. The argument linear address @var{addr} should already have the
11335 appropriate segment's base address added to it, because this command
11336 accepts addresses which may belong to @emph{any} segment. For
11337 example, here's how to display the Page Table entry for the page where
11338 the variable @code{i} is stored:
11341 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11342 @exdent @code{Page Table entry for address 0x11a00d30:}
11343 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11347 This says that @code{i} is stored at offset @code{0xd30} from the page
11348 whose physical base address is @code{0x02698000}, and prints all the
11349 attributes of that page.
11351 Note that you must cast the addresses of variables to a @code{char *},
11352 since otherwise the value of @code{__djgpp_base_address}, the base
11353 address of all variables and functions in a @sc{djgpp} program, will
11354 be added using the rules of C pointer arithmetics: if @code{i} is
11355 declared an @code{int}, @value{GDBN} will add 4 times the value of
11356 @code{__djgpp_base_address} to the address of @code{i}.
11358 Here's another example, it displays the Page Table entry for the
11362 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11363 @exdent @code{Page Table entry for address 0x29110:}
11364 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11368 (The @code{+ 3} offset is because the transfer buffer's address is the
11369 3rd member of the @code{_go32_info_block} structure.) The output of
11370 this command clearly shows that addresses in conventional memory are
11371 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11373 This command is supported only with some DPMI servers.
11376 @node Cygwin Native
11377 @subsection Features for Debugging MS Windows PE executables
11378 @cindex MS Windows debugging
11379 @cindex native Cygwin debugging
11380 @cindex Cygwin-specific commands
11382 @value{GDBN} supports native debugging of MS Windows programs, and
11383 defines a few commands specific to the Cygwin port. This
11384 subsection describes those commands.
11389 This is a prefix of MS Windows specific commands which print
11390 information about the target system and important OS structures.
11392 @item info w32 selector
11393 This command displays information returned by
11394 the Win32 API @code{GetThreadSelectorEntry} function.
11395 It takes an optional argument that is evaluated to
11396 a long value to give the information about this given selector.
11397 Without argument, this command displays information
11398 about the the six segment registers.
11402 This is a Cygwin specific alias of info shared.
11404 @kindex dll-symbols
11406 This command loads symbols from a dll similarly to
11407 add-sym command but without the need to specify a base address.
11409 @kindex set new-console
11410 @item set new-console @var{mode}
11411 If @var{mode} is @code{on} the debuggee will
11412 be started in a new console on next start.
11413 If @var{mode} is @code{off}i, the debuggee will
11414 be started in the same console as the debugger.
11416 @kindex show new-console
11417 @item show new-console
11418 Displays whether a new console is used
11419 when the debuggee is started.
11421 @kindex set new-group
11422 @item set new-group @var{mode}
11423 This boolean value controls whether the debuggee should
11424 start a new group or stay in the same group as the debugger.
11425 This affects the way the Windows OS handles
11428 @kindex show new-group
11429 @item show new-group
11430 Displays current value of new-group boolean.
11432 @kindex set debugevents
11433 @item set debugevents
11434 This boolean value adds debug output concerning events seen by the debugger.
11436 @kindex set debugexec
11437 @item set debugexec
11438 This boolean value adds debug output concerning execute events
11439 seen by the debugger.
11441 @kindex set debugexceptions
11442 @item set debugexceptions
11443 This boolean value adds debug ouptut concerning exception events
11444 seen by the debugger.
11446 @kindex set debugmemory
11447 @item set debugmemory
11448 This boolean value adds debug ouptut concerning memory events
11449 seen by the debugger.
11453 This boolean values specifies whether the debuggee is called
11454 via a shell or directly (default value is on).
11458 Displays if the debuggee will be started with a shell.
11463 @section Embedded Operating Systems
11465 This section describes configurations involving the debugging of
11466 embedded operating systems that are available for several different
11470 * VxWorks:: Using @value{GDBN} with VxWorks
11473 @value{GDBN} includes the ability to debug programs running on
11474 various real-time operating systems.
11477 @subsection Using @value{GDBN} with VxWorks
11483 @kindex target vxworks
11484 @item target vxworks @var{machinename}
11485 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11486 is the target system's machine name or IP address.
11490 On VxWorks, @code{load} links @var{filename} dynamically on the
11491 current target system as well as adding its symbols in @value{GDBN}.
11493 @value{GDBN} enables developers to spawn and debug tasks running on networked
11494 VxWorks targets from a Unix host. Already-running tasks spawned from
11495 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11496 both the Unix host and on the VxWorks target. The program
11497 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11498 installed with the name @code{vxgdb}, to distinguish it from a
11499 @value{GDBN} for debugging programs on the host itself.)
11502 @item VxWorks-timeout @var{args}
11503 @kindex vxworks-timeout
11504 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11505 This option is set by the user, and @var{args} represents the number of
11506 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11507 your VxWorks target is a slow software simulator or is on the far side
11508 of a thin network line.
11511 The following information on connecting to VxWorks was current when
11512 this manual was produced; newer releases of VxWorks may use revised
11515 @kindex INCLUDE_RDB
11516 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11517 to include the remote debugging interface routines in the VxWorks
11518 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11519 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11520 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11521 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11522 information on configuring and remaking VxWorks, see the manufacturer's
11524 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11526 Once you have included @file{rdb.a} in your VxWorks system image and set
11527 your Unix execution search path to find @value{GDBN}, you are ready to
11528 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11529 @code{vxgdb}, depending on your installation).
11531 @value{GDBN} comes up showing the prompt:
11538 * VxWorks Connection:: Connecting to VxWorks
11539 * VxWorks Download:: VxWorks download
11540 * VxWorks Attach:: Running tasks
11543 @node VxWorks Connection
11544 @subsubsection Connecting to VxWorks
11546 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11547 network. To connect to a target whose host name is ``@code{tt}'', type:
11550 (vxgdb) target vxworks tt
11554 @value{GDBN} displays messages like these:
11557 Attaching remote machine across net...
11562 @value{GDBN} then attempts to read the symbol tables of any object modules
11563 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11564 these files by searching the directories listed in the command search
11565 path (@pxref{Environment, ,Your program's environment}); if it fails
11566 to find an object file, it displays a message such as:
11569 prog.o: No such file or directory.
11572 When this happens, add the appropriate directory to the search path with
11573 the @value{GDBN} command @code{path}, and execute the @code{target}
11576 @node VxWorks Download
11577 @subsubsection VxWorks download
11579 @cindex download to VxWorks
11580 If you have connected to the VxWorks target and you want to debug an
11581 object that has not yet been loaded, you can use the @value{GDBN}
11582 @code{load} command to download a file from Unix to VxWorks
11583 incrementally. The object file given as an argument to the @code{load}
11584 command is actually opened twice: first by the VxWorks target in order
11585 to download the code, then by @value{GDBN} in order to read the symbol
11586 table. This can lead to problems if the current working directories on
11587 the two systems differ. If both systems have NFS mounted the same
11588 filesystems, you can avoid these problems by using absolute paths.
11589 Otherwise, it is simplest to set the working directory on both systems
11590 to the directory in which the object file resides, and then to reference
11591 the file by its name, without any path. For instance, a program
11592 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11593 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11594 program, type this on VxWorks:
11597 -> cd "@var{vxpath}/vw/demo/rdb"
11601 Then, in @value{GDBN}, type:
11604 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11605 (vxgdb) load prog.o
11608 @value{GDBN} displays a response similar to this:
11611 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11614 You can also use the @code{load} command to reload an object module
11615 after editing and recompiling the corresponding source file. Note that
11616 this makes @value{GDBN} delete all currently-defined breakpoints,
11617 auto-displays, and convenience variables, and to clear the value
11618 history. (This is necessary in order to preserve the integrity of
11619 debugger's data structures that reference the target system's symbol
11622 @node VxWorks Attach
11623 @subsubsection Running tasks
11625 @cindex running VxWorks tasks
11626 You can also attach to an existing task using the @code{attach} command as
11630 (vxgdb) attach @var{task}
11634 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11635 or suspended when you attach to it. Running tasks are suspended at
11636 the time of attachment.
11638 @node Embedded Processors
11639 @section Embedded Processors
11641 This section goes into details specific to particular embedded
11647 * H8/300:: Hitachi H8/300
11648 * H8/500:: Hitachi H8/500
11649 * i960:: Intel i960
11650 * M32R/D:: Mitsubishi M32R/D
11651 * M68K:: Motorola M68K
11652 @c OBSOLETE * M88K:: Motorola M88K
11653 * MIPS Embedded:: MIPS Embedded
11654 * OpenRISC 1000:: OpenRisc 1000
11655 * PA:: HP PA Embedded
11658 * Sparclet:: Tsqware Sparclet
11659 * Sparclite:: Fujitsu Sparclite
11660 * ST2000:: Tandem ST2000
11661 * Z8000:: Zilog Z8000
11670 @item target rdi @var{dev}
11671 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11672 use this target to communicate with both boards running the Angel
11673 monitor, or with the EmbeddedICE JTAG debug device.
11676 @item target rdp @var{dev}
11682 @subsection Hitachi H8/300
11686 @kindex target hms@r{, with H8/300}
11687 @item target hms @var{dev}
11688 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11689 Use special commands @code{device} and @code{speed} to control the serial
11690 line and the communications speed used.
11692 @kindex target e7000@r{, with H8/300}
11693 @item target e7000 @var{dev}
11694 E7000 emulator for Hitachi H8 and SH.
11696 @kindex target sh3@r{, with H8/300}
11697 @kindex target sh3e@r{, with H8/300}
11698 @item target sh3 @var{dev}
11699 @itemx target sh3e @var{dev}
11700 Hitachi SH-3 and SH-3E target systems.
11704 @cindex download to H8/300 or H8/500
11705 @cindex H8/300 or H8/500 download
11706 @cindex download to Hitachi SH
11707 @cindex Hitachi SH download
11708 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11709 board, the @code{load} command downloads your program to the Hitachi
11710 board and also opens it as the current executable target for
11711 @value{GDBN} on your host (like the @code{file} command).
11713 @value{GDBN} needs to know these things to talk to your
11714 Hitachi SH, H8/300, or H8/500:
11718 that you want to use @samp{target hms}, the remote debugging interface
11719 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11720 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11721 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11722 H8/300, or H8/500.)
11725 what serial device connects your host to your Hitachi board (the first
11726 serial device available on your host is the default).
11729 what speed to use over the serial device.
11733 * Hitachi Boards:: Connecting to Hitachi boards.
11734 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11735 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11738 @node Hitachi Boards
11739 @subsubsection Connecting to Hitachi boards
11741 @c only for Unix hosts
11743 @cindex serial device, Hitachi micros
11744 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11745 need to explicitly set the serial device. The default @var{port} is the
11746 first available port on your host. This is only necessary on Unix
11747 hosts, where it is typically something like @file{/dev/ttya}.
11750 @cindex serial line speed, Hitachi micros
11751 @code{@value{GDBN}} has another special command to set the communications
11752 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11753 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11754 the DOS @code{mode} command (for instance,
11755 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11757 The @samp{device} and @samp{speed} commands are available only when you
11758 use a Unix host to debug your Hitachi microprocessor programs. If you
11760 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11761 called @code{asynctsr} to communicate with the development board
11762 through a PC serial port. You must also use the DOS @code{mode} command
11763 to set up the serial port on the DOS side.
11765 The following sample session illustrates the steps needed to start a
11766 program under @value{GDBN} control on an H8/300. The example uses a
11767 sample H8/300 program called @file{t.x}. The procedure is the same for
11768 the Hitachi SH and the H8/500.
11770 First hook up your development board. In this example, we use a
11771 board attached to serial port @code{COM2}; if you use a different serial
11772 port, substitute its name in the argument of the @code{mode} command.
11773 When you call @code{asynctsr}, the auxiliary comms program used by the
11774 debugger, you give it just the numeric part of the serial port's name;
11775 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11779 C:\H8300\TEST> asynctsr 2
11780 C:\H8300\TEST> mode com2:9600,n,8,1,p
11782 Resident portion of MODE loaded
11784 COM2: 9600, n, 8, 1, p
11789 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11790 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11791 disable it, or even boot without it, to use @code{asynctsr} to control
11792 your development board.
11795 @kindex target hms@r{, and serial protocol}
11796 Now that serial communications are set up, and the development board is
11797 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11798 the name of your program as the argument. @code{@value{GDBN}} prompts
11799 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11800 commands to begin your debugging session: @samp{target hms} to specify
11801 cross-debugging to the Hitachi board, and the @code{load} command to
11802 download your program to the board. @code{load} displays the names of
11803 the program's sections, and a @samp{*} for each 2K of data downloaded.
11804 (If you want to refresh @value{GDBN} data on symbols or on the
11805 executable file without downloading, use the @value{GDBN} commands
11806 @code{file} or @code{symbol-file}. These commands, and @code{load}
11807 itself, are described in @ref{Files,,Commands to specify files}.)
11810 (eg-C:\H8300\TEST) @value{GDBP} t.x
11811 @value{GDBN} is free software and you are welcome to distribute copies
11812 of it under certain conditions; type "show copying" to see
11814 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11816 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11817 (@value{GDBP}) target hms
11818 Connected to remote H8/300 HMS system.
11819 (@value{GDBP}) load t.x
11820 .text : 0x8000 .. 0xabde ***********
11821 .data : 0xabde .. 0xad30 *
11822 .stack : 0xf000 .. 0xf014 *
11825 At this point, you're ready to run or debug your program. From here on,
11826 you can use all the usual @value{GDBN} commands. The @code{break} command
11827 sets breakpoints; the @code{run} command starts your program;
11828 @code{print} or @code{x} display data; the @code{continue} command
11829 resumes execution after stopping at a breakpoint. You can use the
11830 @code{help} command at any time to find out more about @value{GDBN} commands.
11832 Remember, however, that @emph{operating system} facilities aren't
11833 available on your development board; for example, if your program hangs,
11834 you can't send an interrupt---but you can press the @sc{reset} switch!
11836 Use the @sc{reset} button on the development board
11839 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11840 no way to pass an interrupt signal to the development board); and
11843 to return to the @value{GDBN} command prompt after your program finishes
11844 normally. The communications protocol provides no other way for @value{GDBN}
11845 to detect program completion.
11848 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11849 development board as a ``normal exit'' of your program.
11852 @subsubsection Using the E7000 in-circuit emulator
11854 @kindex target e7000@r{, with Hitachi ICE}
11855 You can use the E7000 in-circuit emulator to develop code for either the
11856 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11857 e7000} command to connect @value{GDBN} to your E7000:
11860 @item target e7000 @var{port} @var{speed}
11861 Use this form if your E7000 is connected to a serial port. The
11862 @var{port} argument identifies what serial port to use (for example,
11863 @samp{com2}). The third argument is the line speed in bits per second
11864 (for example, @samp{9600}).
11866 @item target e7000 @var{hostname}
11867 If your E7000 is installed as a host on a TCP/IP network, you can just
11868 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11871 @node Hitachi Special
11872 @subsubsection Special @value{GDBN} commands for Hitachi micros
11874 Some @value{GDBN} commands are available only for the H8/300:
11878 @kindex set machine
11879 @kindex show machine
11880 @item set machine h8300
11881 @itemx set machine h8300h
11882 Condition @value{GDBN} for one of the two variants of the H8/300
11883 architecture with @samp{set machine}. You can use @samp{show machine}
11884 to check which variant is currently in effect.
11893 @kindex set memory @var{mod}
11894 @cindex memory models, H8/500
11895 @item set memory @var{mod}
11897 Specify which H8/500 memory model (@var{mod}) you are using with
11898 @samp{set memory}; check which memory model is in effect with @samp{show
11899 memory}. The accepted values for @var{mod} are @code{small},
11900 @code{big}, @code{medium}, and @code{compact}.
11905 @subsection Intel i960
11909 @kindex target mon960
11910 @item target mon960 @var{dev}
11911 MON960 monitor for Intel i960.
11913 @kindex target nindy
11914 @item target nindy @var{devicename}
11915 An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
11916 the name of the serial device to use for the connection, e.g.
11923 @dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
11924 @value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
11925 tell @value{GDBN} how to connect to the 960 in several ways:
11929 Through command line options specifying serial port, version of the
11930 Nindy protocol, and communications speed;
11933 By responding to a prompt on startup;
11936 By using the @code{target} command at any point during your @value{GDBN}
11937 session. @xref{Target Commands, ,Commands for managing targets}.
11941 @cindex download to Nindy-960
11942 With the Nindy interface to an Intel 960 board, @code{load}
11943 downloads @var{filename} to the 960 as well as adding its symbols in
11947 * Nindy Startup:: Startup with Nindy
11948 * Nindy Options:: Options for Nindy
11949 * Nindy Reset:: Nindy reset command
11952 @node Nindy Startup
11953 @subsubsection Startup with Nindy
11955 If you simply start @code{@value{GDBP}} without using any command-line
11956 options, you are prompted for what serial port to use, @emph{before} you
11957 reach the ordinary @value{GDBN} prompt:
11960 Attach /dev/ttyNN -- specify NN, or "quit" to quit:
11964 Respond to the prompt with whatever suffix (after @samp{/dev/tty})
11965 identifies the serial port you want to use. You can, if you choose,
11966 simply start up with no Nindy connection by responding to the prompt
11967 with an empty line. If you do this and later wish to attach to Nindy,
11968 use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
11970 @node Nindy Options
11971 @subsubsection Options for Nindy
11973 These are the startup options for beginning your @value{GDBN} session with a
11974 Nindy-960 board attached:
11977 @item -r @var{port}
11978 Specify the serial port name of a serial interface to be used to connect
11979 to the target system. This option is only available when @value{GDBN} is
11980 configured for the Intel 960 target architecture. You may specify
11981 @var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
11982 device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
11983 suffix for a specific @code{tty} (e.g. @samp{-r a}).
11986 (An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
11987 the ``old'' Nindy monitor protocol to connect to the target system.
11988 This option is only available when @value{GDBN} is configured for the Intel 960
11989 target architecture.
11992 @emph{Warning:} if you specify @samp{-O}, but are actually trying to
11993 connect to a target system that expects the newer protocol, the connection
11994 fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
11995 attempts to reconnect at several different line speeds. You can abort
11996 this process with an interrupt.
12000 Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
12001 system, in an attempt to reset it, before connecting to a Nindy target.
12004 @emph{Warning:} Many target systems do not have the hardware that this
12005 requires; it only works with a few boards.
12009 The standard @samp{-b} option controls the line speed used on the serial
12014 @subsubsection Nindy reset command
12019 For a Nindy target, this command sends a ``break'' to the remote target
12020 system; this is only useful if the target has been equipped with a
12021 circuit to perform a hard reset (or some other interesting action) when
12022 a break is detected.
12027 @subsection Mitsubishi M32R/D
12031 @kindex target m32r
12032 @item target m32r @var{dev}
12033 Mitsubishi M32R/D ROM monitor.
12040 The Motorola m68k configuration includes ColdFire support, and
12041 target command for the following ROM monitors.
12045 @kindex target abug
12046 @item target abug @var{dev}
12047 ABug ROM monitor for M68K.
12049 @kindex target cpu32bug
12050 @item target cpu32bug @var{dev}
12051 CPU32BUG monitor, running on a CPU32 (M68K) board.
12053 @kindex target dbug
12054 @item target dbug @var{dev}
12055 dBUG ROM monitor for Motorola ColdFire.
12058 @item target est @var{dev}
12059 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12061 @kindex target rom68k
12062 @item target rom68k @var{dev}
12063 ROM 68K monitor, running on an M68K IDP board.
12067 If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will
12068 instead have only a single special target command:
12072 @kindex target es1800
12073 @item target es1800 @var{dev}
12074 ES-1800 emulator for M68K.
12082 @kindex target rombug
12083 @item target rombug @var{dev}
12084 ROMBUG ROM monitor for OS/9000.
12088 @c OBSOLETE @node M88K
12089 @c OBSOLETE @subsection M88K
12091 @c OBSOLETE @table @code
12093 @c OBSOLETE @kindex target bug
12094 @c OBSOLETE @item target bug @var{dev}
12095 @c OBSOLETE BUG monitor, running on a MVME187 (m88k) board.
12097 @c OBSOLETE @end table
12099 @node MIPS Embedded
12100 @subsection MIPS Embedded
12102 @cindex MIPS boards
12103 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12104 MIPS board attached to a serial line. This is available when
12105 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12108 Use these @value{GDBN} commands to specify the connection to your target board:
12111 @item target mips @var{port}
12112 @kindex target mips @var{port}
12113 To run a program on the board, start up @code{@value{GDBP}} with the
12114 name of your program as the argument. To connect to the board, use the
12115 command @samp{target mips @var{port}}, where @var{port} is the name of
12116 the serial port connected to the board. If the program has not already
12117 been downloaded to the board, you may use the @code{load} command to
12118 download it. You can then use all the usual @value{GDBN} commands.
12120 For example, this sequence connects to the target board through a serial
12121 port, and loads and runs a program called @var{prog} through the
12125 host$ @value{GDBP} @var{prog}
12126 @value{GDBN} is free software and @dots{}
12127 (@value{GDBP}) target mips /dev/ttyb
12128 (@value{GDBP}) load @var{prog}
12132 @item target mips @var{hostname}:@var{portnumber}
12133 On some @value{GDBN} host configurations, you can specify a TCP
12134 connection (for instance, to a serial line managed by a terminal
12135 concentrator) instead of a serial port, using the syntax
12136 @samp{@var{hostname}:@var{portnumber}}.
12138 @item target pmon @var{port}
12139 @kindex target pmon @var{port}
12142 @item target ddb @var{port}
12143 @kindex target ddb @var{port}
12144 NEC's DDB variant of PMON for Vr4300.
12146 @item target lsi @var{port}
12147 @kindex target lsi @var{port}
12148 LSI variant of PMON.
12150 @kindex target r3900
12151 @item target r3900 @var{dev}
12152 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12154 @kindex target array
12155 @item target array @var{dev}
12156 Array Tech LSI33K RAID controller board.
12162 @value{GDBN} also supports these special commands for MIPS targets:
12165 @item set processor @var{args}
12166 @itemx show processor
12167 @kindex set processor @var{args}
12168 @kindex show processor
12169 Use the @code{set processor} command to set the type of MIPS
12170 processor when you want to access processor-type-specific registers.
12171 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12172 to use the CPU registers appropriate for the 3041 chip.
12173 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12174 is using. Use the @code{info reg} command to see what registers
12175 @value{GDBN} is using.
12177 @item set mipsfpu double
12178 @itemx set mipsfpu single
12179 @itemx set mipsfpu none
12180 @itemx show mipsfpu
12181 @kindex set mipsfpu
12182 @kindex show mipsfpu
12183 @cindex MIPS remote floating point
12184 @cindex floating point, MIPS remote
12185 If your target board does not support the MIPS floating point
12186 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12187 need this, you may wish to put the command in your @value{GDBN} init
12188 file). This tells @value{GDBN} how to find the return value of
12189 functions which return floating point values. It also allows
12190 @value{GDBN} to avoid saving the floating point registers when calling
12191 functions on the board. If you are using a floating point coprocessor
12192 with only single precision floating point support, as on the @sc{r4650}
12193 processor, use the command @samp{set mipsfpu single}. The default
12194 double precision floating point coprocessor may be selected using
12195 @samp{set mipsfpu double}.
12197 In previous versions the only choices were double precision or no
12198 floating point, so @samp{set mipsfpu on} will select double precision
12199 and @samp{set mipsfpu off} will select no floating point.
12201 As usual, you can inquire about the @code{mipsfpu} variable with
12202 @samp{show mipsfpu}.
12204 @item set remotedebug @var{n}
12205 @itemx show remotedebug
12206 @kindex set remotedebug@r{, MIPS protocol}
12207 @kindex show remotedebug@r{, MIPS protocol}
12208 @cindex @code{remotedebug}, MIPS protocol
12209 @cindex MIPS @code{remotedebug} protocol
12210 @c FIXME! For this to be useful, you must know something about the MIPS
12211 @c FIXME...protocol. Where is it described?
12212 You can see some debugging information about communications with the board
12213 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12214 @samp{set remotedebug 1}, every packet is displayed. If you set it
12215 to @code{2}, every character is displayed. You can check the current value
12216 at any time with the command @samp{show remotedebug}.
12218 @item set timeout @var{seconds}
12219 @itemx set retransmit-timeout @var{seconds}
12220 @itemx show timeout
12221 @itemx show retransmit-timeout
12222 @cindex @code{timeout}, MIPS protocol
12223 @cindex @code{retransmit-timeout}, MIPS protocol
12224 @kindex set timeout
12225 @kindex show timeout
12226 @kindex set retransmit-timeout
12227 @kindex show retransmit-timeout
12228 You can control the timeout used while waiting for a packet, in the MIPS
12229 remote protocol, with the @code{set timeout @var{seconds}} command. The
12230 default is 5 seconds. Similarly, you can control the timeout used while
12231 waiting for an acknowledgement of a packet with the @code{set
12232 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12233 You can inspect both values with @code{show timeout} and @code{show
12234 retransmit-timeout}. (These commands are @emph{only} available when
12235 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12237 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12238 is waiting for your program to stop. In that case, @value{GDBN} waits
12239 forever because it has no way of knowing how long the program is going
12240 to run before stopping.
12243 @node OpenRISC 1000
12244 @subsection OpenRISC 1000
12245 @cindex OpenRISC 1000
12247 @cindex or1k boards
12248 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12249 about platform and commands.
12253 @kindex target jtag
12254 @item target jtag jtag://@var{host}:@var{port}
12256 Connects to remote JTAG server.
12257 JTAG remote server can be either an or1ksim or JTAG server,
12258 connected via parallel port to the board.
12260 Example: @code{target jtag jtag://localhost:9999}
12263 @item or1ksim @var{command}
12264 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12265 Simulator, proprietary commands can be executed.
12267 @kindex info or1k spr
12268 @item info or1k spr
12269 Displays spr groups.
12271 @item info or1k spr @var{group}
12272 @itemx info or1k spr @var{groupno}
12273 Displays register names in selected group.
12275 @item info or1k spr @var{group} @var{register}
12276 @itemx info or1k spr @var{register}
12277 @itemx info or1k spr @var{groupno} @var{registerno}
12278 @itemx info or1k spr @var{registerno}
12279 Shows information about specified spr register.
12282 @item spr @var{group} @var{register} @var{value}
12283 @itemx spr @var{register @var{value}}
12284 @itemx spr @var{groupno} @var{registerno @var{value}}
12285 @itemx spr @var{registerno @var{value}}
12286 Writes @var{value} to specified spr register.
12289 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12290 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12291 program execution and is thus much faster. Hardware breakpoints/watchpoint
12292 triggers can be set using:
12295 Load effective address/data
12297 Store effective address/data
12299 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12304 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12305 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12307 @code{htrace} commands:
12308 @cindex OpenRISC 1000 htrace
12311 @item hwatch @var{conditional}
12312 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12313 or Data. For example:
12315 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12317 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12319 @kindex htrace info
12321 Display information about current HW trace configuration.
12323 @kindex htrace trigger
12324 @item htrace trigger @var{conditional}
12325 Set starting criteria for HW trace.
12327 @kindex htrace qualifier
12328 @item htrace qualifier @var{conditional}
12329 Set acquisition qualifier for HW trace.
12331 @kindex htrace stop
12332 @item htrace stop @var{conditional}
12333 Set HW trace stopping criteria.
12335 @kindex htrace record
12336 @item htrace record @var{[data]*}
12337 Selects the data to be recorded, when qualifier is met and HW trace was
12340 @kindex htrace enable
12341 @item htrace enable
12342 @kindex htrace disable
12343 @itemx htrace disable
12344 Enables/disables the HW trace.
12346 @kindex htrace rewind
12347 @item htrace rewind @var{[filename]}
12348 Clears currently recorded trace data.
12350 If filename is specified, new trace file is made and any newly collected data
12351 will be written there.
12353 @kindex htrace print
12354 @item htrace print @var{[start [len]]}
12355 Prints trace buffer, using current record configuration.
12357 @kindex htrace mode continuous
12358 @item htrace mode continuous
12359 Set continuous trace mode.
12361 @kindex htrace mode suspend
12362 @item htrace mode suspend
12363 Set suspend trace mode.
12368 @subsection PowerPC
12372 @kindex target dink32
12373 @item target dink32 @var{dev}
12374 DINK32 ROM monitor.
12376 @kindex target ppcbug
12377 @item target ppcbug @var{dev}
12378 @kindex target ppcbug1
12379 @item target ppcbug1 @var{dev}
12380 PPCBUG ROM monitor for PowerPC.
12383 @item target sds @var{dev}
12384 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12389 @subsection HP PA Embedded
12393 @kindex target op50n
12394 @item target op50n @var{dev}
12395 OP50N monitor, running on an OKI HPPA board.
12397 @kindex target w89k
12398 @item target w89k @var{dev}
12399 W89K monitor, running on a Winbond HPPA board.
12404 @subsection Hitachi SH
12408 @kindex target hms@r{, with Hitachi SH}
12409 @item target hms @var{dev}
12410 A Hitachi SH board attached via serial line to your host. Use special
12411 commands @code{device} and @code{speed} to control the serial line and
12412 the communications speed used.
12414 @kindex target e7000@r{, with Hitachi SH}
12415 @item target e7000 @var{dev}
12416 E7000 emulator for Hitachi SH.
12418 @kindex target sh3@r{, with SH}
12419 @kindex target sh3e@r{, with SH}
12420 @item target sh3 @var{dev}
12421 @item target sh3e @var{dev}
12422 Hitachi SH-3 and SH-3E target systems.
12427 @subsection Tsqware Sparclet
12431 @value{GDBN} enables developers to debug tasks running on
12432 Sparclet targets from a Unix host.
12433 @value{GDBN} uses code that runs on
12434 both the Unix host and on the Sparclet target. The program
12435 @code{@value{GDBP}} is installed and executed on the Unix host.
12438 @item remotetimeout @var{args}
12439 @kindex remotetimeout
12440 @value{GDBN} supports the option @code{remotetimeout}.
12441 This option is set by the user, and @var{args} represents the number of
12442 seconds @value{GDBN} waits for responses.
12445 @cindex compiling, on Sparclet
12446 When compiling for debugging, include the options @samp{-g} to get debug
12447 information and @samp{-Ttext} to relocate the program to where you wish to
12448 load it on the target. You may also want to add the options @samp{-n} or
12449 @samp{-N} in order to reduce the size of the sections. Example:
12452 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12455 You can use @code{objdump} to verify that the addresses are what you intended:
12458 sparclet-aout-objdump --headers --syms prog
12461 @cindex running, on Sparclet
12463 your Unix execution search path to find @value{GDBN}, you are ready to
12464 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12465 (or @code{sparclet-aout-gdb}, depending on your installation).
12467 @value{GDBN} comes up showing the prompt:
12474 * Sparclet File:: Setting the file to debug
12475 * Sparclet Connection:: Connecting to Sparclet
12476 * Sparclet Download:: Sparclet download
12477 * Sparclet Execution:: Running and debugging
12480 @node Sparclet File
12481 @subsubsection Setting file to debug
12483 The @value{GDBN} command @code{file} lets you choose with program to debug.
12486 (gdbslet) file prog
12490 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12491 @value{GDBN} locates
12492 the file by searching the directories listed in the command search
12494 If the file was compiled with debug information (option "-g"), source
12495 files will be searched as well.
12496 @value{GDBN} locates
12497 the source files by searching the directories listed in the directory search
12498 path (@pxref{Environment, ,Your program's environment}).
12500 to find a file, it displays a message such as:
12503 prog: No such file or directory.
12506 When this happens, add the appropriate directories to the search paths with
12507 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12508 @code{target} command again.
12510 @node Sparclet Connection
12511 @subsubsection Connecting to Sparclet
12513 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12514 To connect to a target on serial port ``@code{ttya}'', type:
12517 (gdbslet) target sparclet /dev/ttya
12518 Remote target sparclet connected to /dev/ttya
12519 main () at ../prog.c:3
12523 @value{GDBN} displays messages like these:
12529 @node Sparclet Download
12530 @subsubsection Sparclet download
12532 @cindex download to Sparclet
12533 Once connected to the Sparclet target,
12534 you can use the @value{GDBN}
12535 @code{load} command to download the file from the host to the target.
12536 The file name and load offset should be given as arguments to the @code{load}
12538 Since the file format is aout, the program must be loaded to the starting
12539 address. You can use @code{objdump} to find out what this value is. The load
12540 offset is an offset which is added to the VMA (virtual memory address)
12541 of each of the file's sections.
12542 For instance, if the program
12543 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12544 and bss at 0x12010170, in @value{GDBN}, type:
12547 (gdbslet) load prog 0x12010000
12548 Loading section .text, size 0xdb0 vma 0x12010000
12551 If the code is loaded at a different address then what the program was linked
12552 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12553 to tell @value{GDBN} where to map the symbol table.
12555 @node Sparclet Execution
12556 @subsubsection Running and debugging
12558 @cindex running and debugging Sparclet programs
12559 You can now begin debugging the task using @value{GDBN}'s execution control
12560 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12561 manual for the list of commands.
12565 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12567 Starting program: prog
12568 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12569 3 char *symarg = 0;
12571 4 char *execarg = "hello!";
12576 @subsection Fujitsu Sparclite
12580 @kindex target sparclite
12581 @item target sparclite @var{dev}
12582 Fujitsu sparclite boards, used only for the purpose of loading.
12583 You must use an additional command to debug the program.
12584 For example: target remote @var{dev} using @value{GDBN} standard
12590 @subsection Tandem ST2000
12592 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12595 To connect your ST2000 to the host system, see the manufacturer's
12596 manual. Once the ST2000 is physically attached, you can run:
12599 target st2000 @var{dev} @var{speed}
12603 to establish it as your debugging environment. @var{dev} is normally
12604 the name of a serial device, such as @file{/dev/ttya}, connected to the
12605 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12606 connection (for example, to a serial line attached via a terminal
12607 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12609 The @code{load} and @code{attach} commands are @emph{not} defined for
12610 this target; you must load your program into the ST2000 as you normally
12611 would for standalone operation. @value{GDBN} reads debugging information
12612 (such as symbols) from a separate, debugging version of the program
12613 available on your host computer.
12614 @c FIXME!! This is terribly vague; what little content is here is
12615 @c basically hearsay.
12617 @cindex ST2000 auxiliary commands
12618 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12622 @item st2000 @var{command}
12623 @kindex st2000 @var{cmd}
12624 @cindex STDBUG commands (ST2000)
12625 @cindex commands to STDBUG (ST2000)
12626 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12627 manual for available commands.
12630 @cindex connect (to STDBUG)
12631 Connect the controlling terminal to the STDBUG command monitor. When
12632 you are done interacting with STDBUG, typing either of two character
12633 sequences gets you back to the @value{GDBN} command prompt:
12634 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12635 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12639 @subsection Zilog Z8000
12642 @cindex simulator, Z8000
12643 @cindex Zilog Z8000 simulator
12645 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12648 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12649 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12650 segmented variant). The simulator recognizes which architecture is
12651 appropriate by inspecting the object code.
12654 @item target sim @var{args}
12656 @kindex target sim@r{, with Z8000}
12657 Debug programs on a simulated CPU. If the simulator supports setup
12658 options, specify them via @var{args}.
12662 After specifying this target, you can debug programs for the simulated
12663 CPU in the same style as programs for your host computer; use the
12664 @code{file} command to load a new program image, the @code{run} command
12665 to run your program, and so on.
12667 As well as making available all the usual machine registers
12668 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12669 additional items of information as specially named registers:
12674 Counts clock-ticks in the simulator.
12677 Counts instructions run in the simulator.
12680 Execution time in 60ths of a second.
12684 You can refer to these values in @value{GDBN} expressions with the usual
12685 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12686 conditional breakpoint that suspends only after at least 5000
12687 simulated clock ticks.
12689 @node Architectures
12690 @section Architectures
12692 This section describes characteristics of architectures that affect
12693 all uses of @value{GDBN} with the architecture, both native and cross.
12706 @kindex set rstack_high_address
12707 @cindex AMD 29K register stack
12708 @cindex register stack, AMD29K
12709 @item set rstack_high_address @var{address}
12710 On AMD 29000 family processors, registers are saved in a separate
12711 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12712 extent of this stack. Normally, @value{GDBN} just assumes that the
12713 stack is ``large enough''. This may result in @value{GDBN} referencing
12714 memory locations that do not exist. If necessary, you can get around
12715 this problem by specifying the ending address of the register stack with
12716 the @code{set rstack_high_address} command. The argument should be an
12717 address, which you probably want to precede with @samp{0x} to specify in
12720 @kindex show rstack_high_address
12721 @item show rstack_high_address
12722 Display the current limit of the register stack, on AMD 29000 family
12730 See the following section.
12735 @cindex stack on Alpha
12736 @cindex stack on MIPS
12737 @cindex Alpha stack
12739 Alpha- and MIPS-based computers use an unusual stack frame, which
12740 sometimes requires @value{GDBN} to search backward in the object code to
12741 find the beginning of a function.
12743 @cindex response time, MIPS debugging
12744 To improve response time (especially for embedded applications, where
12745 @value{GDBN} may be restricted to a slow serial line for this search)
12746 you may want to limit the size of this search, using one of these
12750 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12751 @item set heuristic-fence-post @var{limit}
12752 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12753 search for the beginning of a function. A value of @var{0} (the
12754 default) means there is no limit. However, except for @var{0}, the
12755 larger the limit the more bytes @code{heuristic-fence-post} must search
12756 and therefore the longer it takes to run.
12758 @item show heuristic-fence-post
12759 Display the current limit.
12763 These commands are available @emph{only} when @value{GDBN} is configured
12764 for debugging programs on Alpha or MIPS processors.
12767 @node Controlling GDB
12768 @chapter Controlling @value{GDBN}
12770 You can alter the way @value{GDBN} interacts with you by using the
12771 @code{set} command. For commands controlling how @value{GDBN} displays
12772 data, see @ref{Print Settings, ,Print settings}. Other settings are
12777 * Editing:: Command editing
12778 * History:: Command history
12779 * Screen Size:: Screen size
12780 * Numbers:: Numbers
12781 * Messages/Warnings:: Optional warnings and messages
12782 * Debugging Output:: Optional messages about internal happenings
12790 @value{GDBN} indicates its readiness to read a command by printing a string
12791 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12792 can change the prompt string with the @code{set prompt} command. For
12793 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12794 the prompt in one of the @value{GDBN} sessions so that you can always tell
12795 which one you are talking to.
12797 @emph{Note:} @code{set prompt} does not add a space for you after the
12798 prompt you set. This allows you to set a prompt which ends in a space
12799 or a prompt that does not.
12803 @item set prompt @var{newprompt}
12804 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12806 @kindex show prompt
12808 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12812 @section Command editing
12814 @cindex command line editing
12816 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12817 @sc{gnu} library provides consistent behavior for programs which provide a
12818 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12819 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12820 substitution, and a storage and recall of command history across
12821 debugging sessions.
12823 You may control the behavior of command line editing in @value{GDBN} with the
12824 command @code{set}.
12827 @kindex set editing
12830 @itemx set editing on
12831 Enable command line editing (enabled by default).
12833 @item set editing off
12834 Disable command line editing.
12836 @kindex show editing
12838 Show whether command line editing is enabled.
12842 @section Command history
12844 @value{GDBN} can keep track of the commands you type during your
12845 debugging sessions, so that you can be certain of precisely what
12846 happened. Use these commands to manage the @value{GDBN} command
12850 @cindex history substitution
12851 @cindex history file
12852 @kindex set history filename
12853 @kindex GDBHISTFILE
12854 @item set history filename @var{fname}
12855 Set the name of the @value{GDBN} command history file to @var{fname}.
12856 This is the file where @value{GDBN} reads an initial command history
12857 list, and where it writes the command history from this session when it
12858 exits. You can access this list through history expansion or through
12859 the history command editing characters listed below. This file defaults
12860 to the value of the environment variable @code{GDBHISTFILE}, or to
12861 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12864 @cindex history save
12865 @kindex set history save
12866 @item set history save
12867 @itemx set history save on
12868 Record command history in a file, whose name may be specified with the
12869 @code{set history filename} command. By default, this option is disabled.
12871 @item set history save off
12872 Stop recording command history in a file.
12874 @cindex history size
12875 @kindex set history size
12876 @item set history size @var{size}
12877 Set the number of commands which @value{GDBN} keeps in its history list.
12878 This defaults to the value of the environment variable
12879 @code{HISTSIZE}, or to 256 if this variable is not set.
12882 @cindex history expansion
12883 History expansion assigns special meaning to the character @kbd{!}.
12884 @ifset have-readline-appendices
12885 @xref{Event Designators}.
12888 Since @kbd{!} is also the logical not operator in C, history expansion
12889 is off by default. If you decide to enable history expansion with the
12890 @code{set history expansion on} command, you may sometimes need to
12891 follow @kbd{!} (when it is used as logical not, in an expression) with
12892 a space or a tab to prevent it from being expanded. The readline
12893 history facilities do not attempt substitution on the strings
12894 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12896 The commands to control history expansion are:
12899 @kindex set history expansion
12900 @item set history expansion on
12901 @itemx set history expansion
12902 Enable history expansion. History expansion is off by default.
12904 @item set history expansion off
12905 Disable history expansion.
12907 The readline code comes with more complete documentation of
12908 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12909 or @code{vi} may wish to read it.
12910 @ifset have-readline-appendices
12911 @xref{Command Line Editing}.
12915 @kindex show history
12917 @itemx show history filename
12918 @itemx show history save
12919 @itemx show history size
12920 @itemx show history expansion
12921 These commands display the state of the @value{GDBN} history parameters.
12922 @code{show history} by itself displays all four states.
12928 @item show commands
12929 Display the last ten commands in the command history.
12931 @item show commands @var{n}
12932 Print ten commands centered on command number @var{n}.
12934 @item show commands +
12935 Print ten commands just after the commands last printed.
12939 @section Screen size
12940 @cindex size of screen
12941 @cindex pauses in output
12943 Certain commands to @value{GDBN} may produce large amounts of
12944 information output to the screen. To help you read all of it,
12945 @value{GDBN} pauses and asks you for input at the end of each page of
12946 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12947 to discard the remaining output. Also, the screen width setting
12948 determines when to wrap lines of output. Depending on what is being
12949 printed, @value{GDBN} tries to break the line at a readable place,
12950 rather than simply letting it overflow onto the following line.
12952 Normally @value{GDBN} knows the size of the screen from the terminal
12953 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12954 together with the value of the @code{TERM} environment variable and the
12955 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12956 you can override it with the @code{set height} and @code{set
12963 @kindex show height
12964 @item set height @var{lpp}
12966 @itemx set width @var{cpl}
12968 These @code{set} commands specify a screen height of @var{lpp} lines and
12969 a screen width of @var{cpl} characters. The associated @code{show}
12970 commands display the current settings.
12972 If you specify a height of zero lines, @value{GDBN} does not pause during
12973 output no matter how long the output is. This is useful if output is to a
12974 file or to an editor buffer.
12976 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12977 from wrapping its output.
12982 @cindex number representation
12983 @cindex entering numbers
12985 You can always enter numbers in octal, decimal, or hexadecimal in
12986 @value{GDBN} by the usual conventions: octal numbers begin with
12987 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12988 begin with @samp{0x}. Numbers that begin with none of these are, by
12989 default, entered in base 10; likewise, the default display for
12990 numbers---when no particular format is specified---is base 10. You can
12991 change the default base for both input and output with the @code{set
12995 @kindex set input-radix
12996 @item set input-radix @var{base}
12997 Set the default base for numeric input. Supported choices
12998 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12999 specified either unambiguously or using the current default radix; for
13009 sets the base to decimal. On the other hand, @samp{set radix 10}
13010 leaves the radix unchanged no matter what it was.
13012 @kindex set output-radix
13013 @item set output-radix @var{base}
13014 Set the default base for numeric display. Supported choices
13015 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13016 specified either unambiguously or using the current default radix.
13018 @kindex show input-radix
13019 @item show input-radix
13020 Display the current default base for numeric input.
13022 @kindex show output-radix
13023 @item show output-radix
13024 Display the current default base for numeric display.
13027 @node Messages/Warnings
13028 @section Optional warnings and messages
13030 By default, @value{GDBN} is silent about its inner workings. If you are
13031 running on a slow machine, you may want to use the @code{set verbose}
13032 command. This makes @value{GDBN} tell you when it does a lengthy
13033 internal operation, so you will not think it has crashed.
13035 Currently, the messages controlled by @code{set verbose} are those
13036 which announce that the symbol table for a source file is being read;
13037 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13040 @kindex set verbose
13041 @item set verbose on
13042 Enables @value{GDBN} output of certain informational messages.
13044 @item set verbose off
13045 Disables @value{GDBN} output of certain informational messages.
13047 @kindex show verbose
13049 Displays whether @code{set verbose} is on or off.
13052 By default, if @value{GDBN} encounters bugs in the symbol table of an
13053 object file, it is silent; but if you are debugging a compiler, you may
13054 find this information useful (@pxref{Symbol Errors, ,Errors reading
13059 @kindex set complaints
13060 @item set complaints @var{limit}
13061 Permits @value{GDBN} to output @var{limit} complaints about each type of
13062 unusual symbols before becoming silent about the problem. Set
13063 @var{limit} to zero to suppress all complaints; set it to a large number
13064 to prevent complaints from being suppressed.
13066 @kindex show complaints
13067 @item show complaints
13068 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13072 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13073 lot of stupid questions to confirm certain commands. For example, if
13074 you try to run a program which is already running:
13078 The program being debugged has been started already.
13079 Start it from the beginning? (y or n)
13082 If you are willing to unflinchingly face the consequences of your own
13083 commands, you can disable this ``feature'':
13087 @kindex set confirm
13089 @cindex confirmation
13090 @cindex stupid questions
13091 @item set confirm off
13092 Disables confirmation requests.
13094 @item set confirm on
13095 Enables confirmation requests (the default).
13097 @kindex show confirm
13099 Displays state of confirmation requests.
13103 @node Debugging Output
13104 @section Optional messages about internal happenings
13106 @kindex set debug arch
13107 @item set debug arch
13108 Turns on or off display of gdbarch debugging info. The default is off
13109 @kindex show debug arch
13110 @item show debug arch
13111 Displays the current state of displaying gdbarch debugging info.
13112 @kindex set debug event
13113 @item set debug event
13114 Turns on or off display of @value{GDBN} event debugging info. The
13116 @kindex show debug event
13117 @item show debug event
13118 Displays the current state of displaying @value{GDBN} event debugging
13120 @kindex set debug expression
13121 @item set debug expression
13122 Turns on or off display of @value{GDBN} expression debugging info. The
13124 @kindex show debug expression
13125 @item show debug expression
13126 Displays the current state of displaying @value{GDBN} expression
13128 @kindex set debug overload
13129 @item set debug overload
13130 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13131 info. This includes info such as ranking of functions, etc. The default
13133 @kindex show debug overload
13134 @item show debug overload
13135 Displays the current state of displaying @value{GDBN} C@t{++} overload
13137 @kindex set debug remote
13138 @cindex packets, reporting on stdout
13139 @cindex serial connections, debugging
13140 @item set debug remote
13141 Turns on or off display of reports on all packets sent back and forth across
13142 the serial line to the remote machine. The info is printed on the
13143 @value{GDBN} standard output stream. The default is off.
13144 @kindex show debug remote
13145 @item show debug remote
13146 Displays the state of display of remote packets.
13147 @kindex set debug serial
13148 @item set debug serial
13149 Turns on or off display of @value{GDBN} serial debugging info. The
13151 @kindex show debug serial
13152 @item show debug serial
13153 Displays the current state of displaying @value{GDBN} serial debugging
13155 @kindex set debug target
13156 @item set debug target
13157 Turns on or off display of @value{GDBN} target debugging info. This info
13158 includes what is going on at the target level of GDB, as it happens. The
13160 @kindex show debug target
13161 @item show debug target
13162 Displays the current state of displaying @value{GDBN} target debugging
13164 @kindex set debug varobj
13165 @item set debug varobj
13166 Turns on or off display of @value{GDBN} variable object debugging
13167 info. The default is off.
13168 @kindex show debug varobj
13169 @item show debug varobj
13170 Displays the current state of displaying @value{GDBN} variable object
13175 @chapter Canned Sequences of Commands
13177 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13178 command lists}), @value{GDBN} provides two ways to store sequences of
13179 commands for execution as a unit: user-defined commands and command
13183 * Define:: User-defined commands
13184 * Hooks:: User-defined command hooks
13185 * Command Files:: Command files
13186 * Output:: Commands for controlled output
13190 @section User-defined commands
13192 @cindex user-defined command
13193 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13194 which you assign a new name as a command. This is done with the
13195 @code{define} command. User commands may accept up to 10 arguments
13196 separated by whitespace. Arguments are accessed within the user command
13197 via @var{$arg0@dots{}$arg9}. A trivial example:
13201 print $arg0 + $arg1 + $arg2
13205 To execute the command use:
13212 This defines the command @code{adder}, which prints the sum of
13213 its three arguments. Note the arguments are text substitutions, so they may
13214 reference variables, use complex expressions, or even perform inferior
13220 @item define @var{commandname}
13221 Define a command named @var{commandname}. If there is already a command
13222 by that name, you are asked to confirm that you want to redefine it.
13224 The definition of the command is made up of other @value{GDBN} command lines,
13225 which are given following the @code{define} command. The end of these
13226 commands is marked by a line containing @code{end}.
13231 Takes a single argument, which is an expression to evaluate.
13232 It is followed by a series of commands that are executed
13233 only if the expression is true (nonzero).
13234 There can then optionally be a line @code{else}, followed
13235 by a series of commands that are only executed if the expression
13236 was false. The end of the list is marked by a line containing @code{end}.
13240 The syntax is similar to @code{if}: the command takes a single argument,
13241 which is an expression to evaluate, and must be followed by the commands to
13242 execute, one per line, terminated by an @code{end}.
13243 The commands are executed repeatedly as long as the expression
13247 @item document @var{commandname}
13248 Document the user-defined command @var{commandname}, so that it can be
13249 accessed by @code{help}. The command @var{commandname} must already be
13250 defined. This command reads lines of documentation just as @code{define}
13251 reads the lines of the command definition, ending with @code{end}.
13252 After the @code{document} command is finished, @code{help} on command
13253 @var{commandname} displays the documentation you have written.
13255 You may use the @code{document} command again to change the
13256 documentation of a command. Redefining the command with @code{define}
13257 does not change the documentation.
13259 @kindex help user-defined
13260 @item help user-defined
13261 List all user-defined commands, with the first line of the documentation
13266 @itemx show user @var{commandname}
13267 Display the @value{GDBN} commands used to define @var{commandname} (but
13268 not its documentation). If no @var{commandname} is given, display the
13269 definitions for all user-defined commands.
13271 @kindex show max-user-call-depth
13272 @kindex set max-user-call-depth
13273 @item show max-user-call-depth
13274 @itemx set max-user-call-depth
13275 The value of @code{max-user-call-depth} controls how many recursion
13276 levels are allowed in user-defined commands before GDB suspects an
13277 infinite recursion and aborts the command.
13281 When user-defined commands are executed, the
13282 commands of the definition are not printed. An error in any command
13283 stops execution of the user-defined command.
13285 If used interactively, commands that would ask for confirmation proceed
13286 without asking when used inside a user-defined command. Many @value{GDBN}
13287 commands that normally print messages to say what they are doing omit the
13288 messages when used in a user-defined command.
13291 @section User-defined command hooks
13292 @cindex command hooks
13293 @cindex hooks, for commands
13294 @cindex hooks, pre-command
13298 You may define @dfn{hooks}, which are a special kind of user-defined
13299 command. Whenever you run the command @samp{foo}, if the user-defined
13300 command @samp{hook-foo} exists, it is executed (with no arguments)
13301 before that command.
13303 @cindex hooks, post-command
13306 A hook may also be defined which is run after the command you executed.
13307 Whenever you run the command @samp{foo}, if the user-defined command
13308 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13309 that command. Post-execution hooks may exist simultaneously with
13310 pre-execution hooks, for the same command.
13312 It is valid for a hook to call the command which it hooks. If this
13313 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13315 @c It would be nice if hookpost could be passed a parameter indicating
13316 @c if the command it hooks executed properly or not. FIXME!
13318 @kindex stop@r{, a pseudo-command}
13319 In addition, a pseudo-command, @samp{stop} exists. Defining
13320 (@samp{hook-stop}) makes the associated commands execute every time
13321 execution stops in your program: before breakpoint commands are run,
13322 displays are printed, or the stack frame is printed.
13324 For example, to ignore @code{SIGALRM} signals while
13325 single-stepping, but treat them normally during normal execution,
13330 handle SIGALRM nopass
13334 handle SIGALRM pass
13337 define hook-continue
13338 handle SIGLARM pass
13342 As a further example, to hook at the begining and end of the @code{echo}
13343 command, and to add extra text to the beginning and end of the message,
13351 define hookpost-echo
13355 (@value{GDBP}) echo Hello World
13356 <<<---Hello World--->>>
13361 You can define a hook for any single-word command in @value{GDBN}, but
13362 not for command aliases; you should define a hook for the basic command
13363 name, e.g. @code{backtrace} rather than @code{bt}.
13364 @c FIXME! So how does Joe User discover whether a command is an alias
13366 If an error occurs during the execution of your hook, execution of
13367 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13368 (before the command that you actually typed had a chance to run).
13370 If you try to define a hook which does not match any known command, you
13371 get a warning from the @code{define} command.
13373 @node Command Files
13374 @section Command files
13376 @cindex command files
13377 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13378 commands. Comments (lines starting with @kbd{#}) may also be included.
13379 An empty line in a command file does nothing; it does not mean to repeat
13380 the last command, as it would from the terminal.
13383 @cindex @file{.gdbinit}
13384 @cindex @file{gdb.ini}
13385 When you start @value{GDBN}, it automatically executes commands from its
13386 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13387 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13388 limitations of file names imposed by DOS filesystems.}.
13389 During startup, @value{GDBN} does the following:
13393 Reads the init file (if any) in your home directory@footnote{On
13394 DOS/Windows systems, the home directory is the one pointed to by the
13395 @code{HOME} environment variable.}.
13398 Processes command line options and operands.
13401 Reads the init file (if any) in the current working directory.
13404 Reads command files specified by the @samp{-x} option.
13407 The init file in your home directory can set options (such as @samp{set
13408 complaints}) that affect subsequent processing of command line options
13409 and operands. Init files are not executed if you use the @samp{-nx}
13410 option (@pxref{Mode Options, ,Choosing modes}).
13412 @cindex init file name
13413 On some configurations of @value{GDBN}, the init file is known by a
13414 different name (these are typically environments where a specialized
13415 form of @value{GDBN} may need to coexist with other forms, hence a
13416 different name for the specialized version's init file). These are the
13417 environments with special init file names:
13419 @cindex @file{.vxgdbinit}
13422 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13424 @cindex @file{.os68gdbinit}
13426 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13428 @cindex @file{.esgdbinit}
13430 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13433 You can also request the execution of a command file with the
13434 @code{source} command:
13438 @item source @var{filename}
13439 Execute the command file @var{filename}.
13442 The lines in a command file are executed sequentially. They are not
13443 printed as they are executed. An error in any command terminates
13444 execution of the command file and control is returned to the console.
13446 Commands that would ask for confirmation if used interactively proceed
13447 without asking when used in a command file. Many @value{GDBN} commands that
13448 normally print messages to say what they are doing omit the messages
13449 when called from command files.
13451 @value{GDBN} also accepts command input from standard input. In this
13452 mode, normal output goes to standard output and error output goes to
13453 standard error. Errors in a command file supplied on standard input do
13454 not terminate execution of the command file --- execution continues with
13458 gdb < cmds > log 2>&1
13461 (The syntax above will vary depending on the shell used.) This example
13462 will execute commands from the file @file{cmds}. All output and errors
13463 would be directed to @file{log}.
13466 @section Commands for controlled output
13468 During the execution of a command file or a user-defined command, normal
13469 @value{GDBN} output is suppressed; the only output that appears is what is
13470 explicitly printed by the commands in the definition. This section
13471 describes three commands useful for generating exactly the output you
13476 @item echo @var{text}
13477 @c I do not consider backslash-space a standard C escape sequence
13478 @c because it is not in ANSI.
13479 Print @var{text}. Nonprinting characters can be included in
13480 @var{text} using C escape sequences, such as @samp{\n} to print a
13481 newline. @strong{No newline is printed unless you specify one.}
13482 In addition to the standard C escape sequences, a backslash followed
13483 by a space stands for a space. This is useful for displaying a
13484 string with spaces at the beginning or the end, since leading and
13485 trailing spaces are otherwise trimmed from all arguments.
13486 To print @samp{@w{ }and foo =@w{ }}, use the command
13487 @samp{echo \@w{ }and foo = \@w{ }}.
13489 A backslash at the end of @var{text} can be used, as in C, to continue
13490 the command onto subsequent lines. For example,
13493 echo This is some text\n\
13494 which is continued\n\
13495 onto several lines.\n
13498 produces the same output as
13501 echo This is some text\n
13502 echo which is continued\n
13503 echo onto several lines.\n
13507 @item output @var{expression}
13508 Print the value of @var{expression} and nothing but that value: no
13509 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13510 value history either. @xref{Expressions, ,Expressions}, for more information
13513 @item output/@var{fmt} @var{expression}
13514 Print the value of @var{expression} in format @var{fmt}. You can use
13515 the same formats as for @code{print}. @xref{Output Formats,,Output
13516 formats}, for more information.
13519 @item printf @var{string}, @var{expressions}@dots{}
13520 Print the values of the @var{expressions} under the control of
13521 @var{string}. The @var{expressions} are separated by commas and may be
13522 either numbers or pointers. Their values are printed as specified by
13523 @var{string}, exactly as if your program were to execute the C
13525 @c FIXME: the above implies that at least all ANSI C formats are
13526 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13527 @c Either this is a bug, or the manual should document what formats are
13531 printf (@var{string}, @var{expressions}@dots{});
13534 For example, you can print two values in hex like this:
13537 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13540 The only backslash-escape sequences that you can use in the format
13541 string are the simple ones that consist of backslash followed by a
13546 @chapter @value{GDBN} Text User Interface
13550 * TUI Overview:: TUI overview
13551 * TUI Keys:: TUI key bindings
13552 * TUI Single Key Mode:: TUI single key mode
13553 * TUI Commands:: TUI specific commands
13554 * TUI Configuration:: TUI configuration variables
13557 The @value{GDBN} Text User Interface, TUI in short,
13558 is a terminal interface which uses the @code{curses} library
13559 to show the source file, the assembly output, the program registers
13560 and @value{GDBN} commands in separate text windows.
13561 The TUI is available only when @value{GDBN} is configured
13562 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13565 @section TUI overview
13567 The TUI has two display modes that can be switched while
13572 A curses (or TUI) mode in which it displays several text
13573 windows on the terminal.
13576 A standard mode which corresponds to the @value{GDBN} configured without
13580 In the TUI mode, @value{GDBN} can display several text window
13585 This window is the @value{GDBN} command window with the @value{GDBN}
13586 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13587 managed using readline but through the TUI. The @emph{command}
13588 window is always visible.
13591 The source window shows the source file of the program. The current
13592 line as well as active breakpoints are displayed in this window.
13595 The assembly window shows the disassembly output of the program.
13598 This window shows the processor registers. It detects when
13599 a register is changed and when this is the case, registers that have
13600 changed are highlighted.
13604 The source and assembly windows show the current program position
13605 by highlighting the current line and marking them with the @samp{>} marker.
13606 Breakpoints are also indicated with two markers. A first one
13607 indicates the breakpoint type:
13611 Breakpoint which was hit at least once.
13614 Breakpoint which was never hit.
13617 Hardware breakpoint which was hit at least once.
13620 Hardware breakpoint which was never hit.
13624 The second marker indicates whether the breakpoint is enabled or not:
13628 Breakpoint is enabled.
13631 Breakpoint is disabled.
13635 The source, assembly and register windows are attached to the thread
13636 and the frame position. They are updated when the current thread
13637 changes, when the frame changes or when the program counter changes.
13638 These three windows are arranged by the TUI according to several
13639 layouts. The layout defines which of these three windows are visible.
13640 The following layouts are available:
13650 source and assembly
13653 source and registers
13656 assembly and registers
13660 On top of the command window a status line gives various information
13661 concerning the current process begin debugged. The status line is
13662 updated when the information it shows changes. The following fields
13667 Indicates the current gdb target
13668 (@pxref{Targets, ,Specifying a Debugging Target}).
13671 Gives information about the current process or thread number.
13672 When no process is being debugged, this field is set to @code{No process}.
13675 Gives the current function name for the selected frame.
13676 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13677 When there is no symbol corresponding to the current program counter
13678 the string @code{??} is displayed.
13681 Indicates the current line number for the selected frame.
13682 When the current line number is not known the string @code{??} is displayed.
13685 Indicates the current program counter address.
13690 @section TUI Key Bindings
13691 @cindex TUI key bindings
13693 The TUI installs several key bindings in the readline keymaps
13694 (@pxref{Command Line Editing}).
13695 They allow to leave or enter in the TUI mode or they operate
13696 directly on the TUI layout and windows. The TUI also provides
13697 a @emph{SingleKey} keymap which binds several keys directly to
13698 @value{GDBN} commands. The following key bindings
13699 are installed for both TUI mode and the @value{GDBN} standard mode.
13708 Enter or leave the TUI mode. When the TUI mode is left,
13709 the curses window management is left and @value{GDBN} operates using
13710 its standard mode writing on the terminal directly. When the TUI
13711 mode is entered, the control is given back to the curses windows.
13712 The screen is then refreshed.
13716 Use a TUI layout with only one window. The layout will
13717 either be @samp{source} or @samp{assembly}. When the TUI mode
13718 is not active, it will switch to the TUI mode.
13720 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13724 Use a TUI layout with at least two windows. When the current
13725 layout shows already two windows, a next layout with two windows is used.
13726 When a new layout is chosen, one window will always be common to the
13727 previous layout and the new one.
13729 Think of it as the Emacs @kbd{C-x 2} binding.
13733 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13734 (@pxref{TUI Single Key Mode}).
13738 The following key bindings are handled only by the TUI mode:
13743 Scroll the active window one page up.
13747 Scroll the active window one page down.
13751 Scroll the active window one line up.
13755 Scroll the active window one line down.
13759 Scroll the active window one column left.
13763 Scroll the active window one column right.
13767 Refresh the screen.
13771 In the TUI mode, the arrow keys are used by the active window
13772 for scrolling. This means they are not available for readline. It is
13773 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13774 @key{C-b} and @key{C-f}.
13776 @node TUI Single Key Mode
13777 @section TUI Single Key Mode
13778 @cindex TUI single key mode
13780 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13781 key binding in the readline keymaps to connect single keys to
13785 @kindex c @r{(SingleKey TUI key)}
13789 @kindex d @r{(SingleKey TUI key)}
13793 @kindex f @r{(SingleKey TUI key)}
13797 @kindex n @r{(SingleKey TUI key)}
13801 @kindex q @r{(SingleKey TUI key)}
13803 exit the @emph{SingleKey} mode.
13805 @kindex r @r{(SingleKey TUI key)}
13809 @kindex s @r{(SingleKey TUI key)}
13813 @kindex u @r{(SingleKey TUI key)}
13817 @kindex v @r{(SingleKey TUI key)}
13821 @kindex w @r{(SingleKey TUI key)}
13827 Other keys temporarily switch to the @value{GDBN} command prompt.
13828 The key that was pressed is inserted in the editing buffer so that
13829 it is possible to type most @value{GDBN} commands without interaction
13830 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13831 @emph{SingleKey} mode is restored. The only way to permanently leave
13832 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13836 @section TUI specific commands
13837 @cindex TUI commands
13839 The TUI has specific commands to control the text windows.
13840 These commands are always available, that is they do not depend on
13841 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13842 is in the standard mode, using these commands will automatically switch
13848 List and give the size of all displayed windows.
13851 @kindex layout next
13852 Display the next layout.
13855 @kindex layout prev
13856 Display the previous layout.
13860 Display the source window only.
13864 Display the assembly window only.
13867 @kindex layout split
13868 Display the source and assembly window.
13871 @kindex layout regs
13872 Display the register window together with the source or assembly window.
13874 @item focus next | prev | src | asm | regs | split
13876 Set the focus to the named window.
13877 This command allows to change the active window so that scrolling keys
13878 can be affected to another window.
13882 Refresh the screen. This is similar to using @key{C-L} key.
13886 Update the source window and the current execution point.
13888 @item winheight @var{name} +@var{count}
13889 @itemx winheight @var{name} -@var{count}
13891 Change the height of the window @var{name} by @var{count}
13892 lines. Positive counts increase the height, while negative counts
13897 @node TUI Configuration
13898 @section TUI configuration variables
13899 @cindex TUI configuration variables
13901 The TUI has several configuration variables that control the
13902 appearance of windows on the terminal.
13905 @item set tui border-kind @var{kind}
13906 @kindex set tui border-kind
13907 Select the border appearance for the source, assembly and register windows.
13908 The possible values are the following:
13911 Use a space character to draw the border.
13914 Use ascii characters + - and | to draw the border.
13917 Use the Alternate Character Set to draw the border. The border is
13918 drawn using character line graphics if the terminal supports them.
13922 @item set tui active-border-mode @var{mode}
13923 @kindex set tui active-border-mode
13924 Select the attributes to display the border of the active window.
13925 The possible values are @code{normal}, @code{standout}, @code{reverse},
13926 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13928 @item set tui border-mode @var{mode}
13929 @kindex set tui border-mode
13930 Select the attributes to display the border of other windows.
13931 The @var{mode} can be one of the following:
13934 Use normal attributes to display the border.
13940 Use reverse video mode.
13943 Use half bright mode.
13945 @item half-standout
13946 Use half bright and standout mode.
13949 Use extra bright or bold mode.
13951 @item bold-standout
13952 Use extra bright or bold and standout mode.
13959 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13962 @cindex @sc{gnu} Emacs
13963 A special interface allows you to use @sc{gnu} Emacs to view (and
13964 edit) the source files for the program you are debugging with
13967 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13968 executable file you want to debug as an argument. This command starts
13969 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13970 created Emacs buffer.
13971 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13973 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13978 All ``terminal'' input and output goes through the Emacs buffer.
13981 This applies both to @value{GDBN} commands and their output, and to the input
13982 and output done by the program you are debugging.
13984 This is useful because it means that you can copy the text of previous
13985 commands and input them again; you can even use parts of the output
13988 All the facilities of Emacs' Shell mode are available for interacting
13989 with your program. In particular, you can send signals the usual
13990 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13995 @value{GDBN} displays source code through Emacs.
13998 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13999 source file for that frame and puts an arrow (@samp{=>}) at the
14000 left margin of the current line. Emacs uses a separate buffer for
14001 source display, and splits the screen to show both your @value{GDBN} session
14004 Explicit @value{GDBN} @code{list} or search commands still produce output as
14005 usual, but you probably have no reason to use them from Emacs.
14008 @emph{Warning:} If the directory where your program resides is not your
14009 current directory, it can be easy to confuse Emacs about the location of
14010 the source files, in which case the auxiliary display buffer does not
14011 appear to show your source. @value{GDBN} can find programs by searching your
14012 environment's @code{PATH} variable, so the @value{GDBN} input and output
14013 session proceeds normally; but Emacs does not get enough information
14014 back from @value{GDBN} to locate the source files in this situation. To
14015 avoid this problem, either start @value{GDBN} mode from the directory where
14016 your program resides, or specify an absolute file name when prompted for the
14017 @kbd{M-x gdb} argument.
14019 A similar confusion can result if you use the @value{GDBN} @code{file} command to
14020 switch to debugging a program in some other location, from an existing
14021 @value{GDBN} buffer in Emacs.
14024 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
14025 you need to call @value{GDBN} by a different name (for example, if you keep
14026 several configurations around, with different names) you can set the
14027 Emacs variable @code{gdb-command-name}; for example,
14030 (setq gdb-command-name "mygdb")
14034 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
14035 in your @file{.emacs} file) makes Emacs call the program named
14036 ``@code{mygdb}'' instead.
14038 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14039 addition to the standard Shell mode commands:
14043 Describe the features of Emacs' @value{GDBN} Mode.
14046 Execute to another source line, like the @value{GDBN} @code{step} command; also
14047 update the display window to show the current file and location.
14050 Execute to next source line in this function, skipping all function
14051 calls, like the @value{GDBN} @code{next} command. Then update the display window
14052 to show the current file and location.
14055 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14056 display window accordingly.
14058 @item M-x gdb-nexti
14059 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
14060 display window accordingly.
14063 Execute until exit from the selected stack frame, like the @value{GDBN}
14064 @code{finish} command.
14067 Continue execution of your program, like the @value{GDBN} @code{continue}
14070 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
14073 Go up the number of frames indicated by the numeric argument
14074 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14075 like the @value{GDBN} @code{up} command.
14077 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
14080 Go down the number of frames indicated by the numeric argument, like the
14081 @value{GDBN} @code{down} command.
14083 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14086 Read the number where the cursor is positioned, and insert it at the end
14087 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14088 around an address that was displayed earlier, type @kbd{disassemble};
14089 then move the cursor to the address display, and pick up the
14090 argument for @code{disassemble} by typing @kbd{C-x &}.
14092 You can customize this further by defining elements of the list
14093 @code{gdb-print-command}; once it is defined, you can format or
14094 otherwise process numbers picked up by @kbd{C-x &} before they are
14095 inserted. A numeric argument to @kbd{C-x &} indicates that you
14096 wish special formatting, and also acts as an index to pick an element of the
14097 list. If the list element is a string, the number to be inserted is
14098 formatted using the Emacs function @code{format}; otherwise the number
14099 is passed as an argument to the corresponding list element.
14102 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14103 tells @value{GDBN} to set a breakpoint on the source line point is on.
14105 If you accidentally delete the source-display buffer, an easy way to get
14106 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14107 request a frame display; when you run under Emacs, this recreates
14108 the source buffer if necessary to show you the context of the current
14111 The source files displayed in Emacs are in ordinary Emacs buffers
14112 which are visiting the source files in the usual way. You can edit
14113 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14114 communicates with Emacs in terms of line numbers. If you add or
14115 delete lines from the text, the line numbers that @value{GDBN} knows cease
14116 to correspond properly with the code.
14118 @c The following dropped because Epoch is nonstandard. Reactivate
14119 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14121 @kindex Emacs Epoch environment
14125 Version 18 of @sc{gnu} Emacs has a built-in window system
14126 called the @code{epoch}
14127 environment. Users of this environment can use a new command,
14128 @code{inspect} which performs identically to @code{print} except that
14129 each value is printed in its own window.
14132 @include annotate.texi
14133 @include gdbmi.texinfo
14136 @chapter Reporting Bugs in @value{GDBN}
14137 @cindex bugs in @value{GDBN}
14138 @cindex reporting bugs in @value{GDBN}
14140 Your bug reports play an essential role in making @value{GDBN} reliable.
14142 Reporting a bug may help you by bringing a solution to your problem, or it
14143 may not. But in any case the principal function of a bug report is to help
14144 the entire community by making the next version of @value{GDBN} work better. Bug
14145 reports are your contribution to the maintenance of @value{GDBN}.
14147 In order for a bug report to serve its purpose, you must include the
14148 information that enables us to fix the bug.
14151 * Bug Criteria:: Have you found a bug?
14152 * Bug Reporting:: How to report bugs
14156 @section Have you found a bug?
14157 @cindex bug criteria
14159 If you are not sure whether you have found a bug, here are some guidelines:
14162 @cindex fatal signal
14163 @cindex debugger crash
14164 @cindex crash of debugger
14166 If the debugger gets a fatal signal, for any input whatever, that is a
14167 @value{GDBN} bug. Reliable debuggers never crash.
14169 @cindex error on valid input
14171 If @value{GDBN} produces an error message for valid input, that is a
14172 bug. (Note that if you're cross debugging, the problem may also be
14173 somewhere in the connection to the target.)
14175 @cindex invalid input
14177 If @value{GDBN} does not produce an error message for invalid input,
14178 that is a bug. However, you should note that your idea of
14179 ``invalid input'' might be our idea of ``an extension'' or ``support
14180 for traditional practice''.
14183 If you are an experienced user of debugging tools, your suggestions
14184 for improvement of @value{GDBN} are welcome in any case.
14187 @node Bug Reporting
14188 @section How to report bugs
14189 @cindex bug reports
14190 @cindex @value{GDBN} bugs, reporting
14192 A number of companies and individuals offer support for @sc{gnu} products.
14193 If you obtained @value{GDBN} from a support organization, we recommend you
14194 contact that organization first.
14196 You can find contact information for many support companies and
14197 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
14199 @c should add a web page ref...
14201 In any event, we also recommend that you submit bug reports for
14202 @value{GDBN}. The prefered method is to submit them directly using
14203 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
14204 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
14207 @strong{Do not send bug reports to @samp{info-gdb}, or to
14208 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
14209 not want to receive bug reports. Those that do have arranged to receive
14212 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
14213 serves as a repeater. The mailing list and the newsgroup carry exactly
14214 the same messages. Often people think of posting bug reports to the
14215 newsgroup instead of mailing them. This appears to work, but it has one
14216 problem which can be crucial: a newsgroup posting often lacks a mail
14217 path back to the sender. Thus, if we need to ask for more information,
14218 we may be unable to reach you. For this reason, it is better to send
14219 bug reports to the mailing list.
14221 The fundamental principle of reporting bugs usefully is this:
14222 @strong{report all the facts}. If you are not sure whether to state a
14223 fact or leave it out, state it!
14225 Often people omit facts because they think they know what causes the
14226 problem and assume that some details do not matter. Thus, you might
14227 assume that the name of the variable you use in an example does not matter.
14228 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
14229 stray memory reference which happens to fetch from the location where that
14230 name is stored in memory; perhaps, if the name were different, the contents
14231 of that location would fool the debugger into doing the right thing despite
14232 the bug. Play it safe and give a specific, complete example. That is the
14233 easiest thing for you to do, and the most helpful.
14235 Keep in mind that the purpose of a bug report is to enable us to fix the
14236 bug. It may be that the bug has been reported previously, but neither
14237 you nor we can know that unless your bug report is complete and
14240 Sometimes people give a few sketchy facts and ask, ``Does this ring a
14241 bell?'' Those bug reports are useless, and we urge everyone to
14242 @emph{refuse to respond to them} except to chide the sender to report
14245 To enable us to fix the bug, you should include all these things:
14249 The version of @value{GDBN}. @value{GDBN} announces it if you start
14250 with no arguments; you can also print it at any time using @code{show
14253 Without this, we will not know whether there is any point in looking for
14254 the bug in the current version of @value{GDBN}.
14257 The type of machine you are using, and the operating system name and
14261 What compiler (and its version) was used to compile @value{GDBN}---e.g.
14262 ``@value{GCC}--2.8.1''.
14265 What compiler (and its version) was used to compile the program you are
14266 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
14267 C Compiler''. For GCC, you can say @code{gcc --version} to get this
14268 information; for other compilers, see the documentation for those
14272 The command arguments you gave the compiler to compile your example and
14273 observe the bug. For example, did you use @samp{-O}? To guarantee
14274 you will not omit something important, list them all. A copy of the
14275 Makefile (or the output from make) is sufficient.
14277 If we were to try to guess the arguments, we would probably guess wrong
14278 and then we might not encounter the bug.
14281 A complete input script, and all necessary source files, that will
14285 A description of what behavior you observe that you believe is
14286 incorrect. For example, ``It gets a fatal signal.''
14288 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
14289 will certainly notice it. But if the bug is incorrect output, we might
14290 not notice unless it is glaringly wrong. You might as well not give us
14291 a chance to make a mistake.
14293 Even if the problem you experience is a fatal signal, you should still
14294 say so explicitly. Suppose something strange is going on, such as, your
14295 copy of @value{GDBN} is out of synch, or you have encountered a bug in
14296 the C library on your system. (This has happened!) Your copy might
14297 crash and ours would not. If you told us to expect a crash, then when
14298 ours fails to crash, we would know that the bug was not happening for
14299 us. If you had not told us to expect a crash, then we would not be able
14300 to draw any conclusion from our observations.
14303 If you wish to suggest changes to the @value{GDBN} source, send us context
14304 diffs. If you even discuss something in the @value{GDBN} source, refer to
14305 it by context, not by line number.
14307 The line numbers in our development sources will not match those in your
14308 sources. Your line numbers would convey no useful information to us.
14312 Here are some things that are not necessary:
14316 A description of the envelope of the bug.
14318 Often people who encounter a bug spend a lot of time investigating
14319 which changes to the input file will make the bug go away and which
14320 changes will not affect it.
14322 This is often time consuming and not very useful, because the way we
14323 will find the bug is by running a single example under the debugger
14324 with breakpoints, not by pure deduction from a series of examples.
14325 We recommend that you save your time for something else.
14327 Of course, if you can find a simpler example to report @emph{instead}
14328 of the original one, that is a convenience for us. Errors in the
14329 output will be easier to spot, running under the debugger will take
14330 less time, and so on.
14332 However, simplification is not vital; if you do not want to do this,
14333 report the bug anyway and send us the entire test case you used.
14336 A patch for the bug.
14338 A patch for the bug does help us if it is a good one. But do not omit
14339 the necessary information, such as the test case, on the assumption that
14340 a patch is all we need. We might see problems with your patch and decide
14341 to fix the problem another way, or we might not understand it at all.
14343 Sometimes with a program as complicated as @value{GDBN} it is very hard to
14344 construct an example that will make the program follow a certain path
14345 through the code. If you do not send us the example, we will not be able
14346 to construct one, so we will not be able to verify that the bug is fixed.
14348 And if we cannot understand what bug you are trying to fix, or why your
14349 patch should be an improvement, we will not install it. A test case will
14350 help us to understand.
14353 A guess about what the bug is or what it depends on.
14355 Such guesses are usually wrong. Even we cannot guess right about such
14356 things without first using the debugger to find the facts.
14359 @c The readline documentation is distributed with the readline code
14360 @c and consists of the two following files:
14362 @c inc-hist.texinfo
14363 @c Use -I with makeinfo to point to the appropriate directory,
14364 @c environment var TEXINPUTS with TeX.
14365 @include rluser.texinfo
14366 @include inc-hist.texinfo
14369 @node Formatting Documentation
14370 @appendix Formatting Documentation
14372 @cindex @value{GDBN} reference card
14373 @cindex reference card
14374 The @value{GDBN} 4 release includes an already-formatted reference card, ready
14375 for printing with PostScript or Ghostscript, in the @file{gdb}
14376 subdirectory of the main source directory@footnote{In
14377 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
14378 release.}. If you can use PostScript or Ghostscript with your printer,
14379 you can print the reference card immediately with @file{refcard.ps}.
14381 The release also includes the source for the reference card. You
14382 can format it, using @TeX{}, by typing:
14388 The @value{GDBN} reference card is designed to print in @dfn{landscape}
14389 mode on US ``letter'' size paper;
14390 that is, on a sheet 11 inches wide by 8.5 inches
14391 high. You will need to specify this form of printing as an option to
14392 your @sc{dvi} output program.
14394 @cindex documentation
14396 All the documentation for @value{GDBN} comes as part of the machine-readable
14397 distribution. The documentation is written in Texinfo format, which is
14398 a documentation system that uses a single source file to produce both
14399 on-line information and a printed manual. You can use one of the Info
14400 formatting commands to create the on-line version of the documentation
14401 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
14403 @value{GDBN} includes an already formatted copy of the on-line Info
14404 version of this manual in the @file{gdb} subdirectory. The main Info
14405 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
14406 subordinate files matching @samp{gdb.info*} in the same directory. If
14407 necessary, you can print out these files, or read them with any editor;
14408 but they are easier to read using the @code{info} subsystem in @sc{gnu}
14409 Emacs or the standalone @code{info} program, available as part of the
14410 @sc{gnu} Texinfo distribution.
14412 If you want to format these Info files yourself, you need one of the
14413 Info formatting programs, such as @code{texinfo-format-buffer} or
14416 If you have @code{makeinfo} installed, and are in the top level
14417 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
14418 version @value{GDBVN}), you can make the Info file by typing:
14425 If you want to typeset and print copies of this manual, you need @TeX{},
14426 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
14427 Texinfo definitions file.
14429 @TeX{} is a typesetting program; it does not print files directly, but
14430 produces output files called @sc{dvi} files. To print a typeset
14431 document, you need a program to print @sc{dvi} files. If your system
14432 has @TeX{} installed, chances are it has such a program. The precise
14433 command to use depends on your system; @kbd{lpr -d} is common; another
14434 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
14435 require a file name without any extension or a @samp{.dvi} extension.
14437 @TeX{} also requires a macro definitions file called
14438 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
14439 written in Texinfo format. On its own, @TeX{} cannot either read or
14440 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
14441 and is located in the @file{gdb-@var{version-number}/texinfo}
14444 If you have @TeX{} and a @sc{dvi} printer program installed, you can
14445 typeset and print this manual. First switch to the the @file{gdb}
14446 subdirectory of the main source directory (for example, to
14447 @file{gdb-@value{GDBVN}/gdb}) and type:
14453 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
14455 @node Installing GDB
14456 @appendix Installing @value{GDBN}
14457 @cindex configuring @value{GDBN}
14458 @cindex installation
14460 @value{GDBN} comes with a @code{configure} script that automates the process
14461 of preparing @value{GDBN} for installation; you can then use @code{make} to
14462 build the @code{gdb} program.
14464 @c irrelevant in info file; it's as current as the code it lives with.
14465 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
14466 look at the @file{README} file in the sources; we may have improved the
14467 installation procedures since publishing this manual.}
14470 The @value{GDBN} distribution includes all the source code you need for
14471 @value{GDBN} in a single directory, whose name is usually composed by
14472 appending the version number to @samp{gdb}.
14474 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
14475 @file{gdb-@value{GDBVN}} directory. That directory contains:
14478 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
14479 script for configuring @value{GDBN} and all its supporting libraries
14481 @item gdb-@value{GDBVN}/gdb
14482 the source specific to @value{GDBN} itself
14484 @item gdb-@value{GDBVN}/bfd
14485 source for the Binary File Descriptor library
14487 @item gdb-@value{GDBVN}/include
14488 @sc{gnu} include files
14490 @item gdb-@value{GDBVN}/libiberty
14491 source for the @samp{-liberty} free software library
14493 @item gdb-@value{GDBVN}/opcodes
14494 source for the library of opcode tables and disassemblers
14496 @item gdb-@value{GDBVN}/readline
14497 source for the @sc{gnu} command-line interface
14499 @item gdb-@value{GDBVN}/glob
14500 source for the @sc{gnu} filename pattern-matching subroutine
14502 @item gdb-@value{GDBVN}/mmalloc
14503 source for the @sc{gnu} memory-mapped malloc package
14506 The simplest way to configure and build @value{GDBN} is to run @code{configure}
14507 from the @file{gdb-@var{version-number}} source directory, which in
14508 this example is the @file{gdb-@value{GDBVN}} directory.
14510 First switch to the @file{gdb-@var{version-number}} source directory
14511 if you are not already in it; then run @code{configure}. Pass the
14512 identifier for the platform on which @value{GDBN} will run as an
14518 cd gdb-@value{GDBVN}
14519 ./configure @var{host}
14524 where @var{host} is an identifier such as @samp{sun4} or
14525 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
14526 (You can often leave off @var{host}; @code{configure} tries to guess the
14527 correct value by examining your system.)
14529 Running @samp{configure @var{host}} and then running @code{make} builds the
14530 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
14531 libraries, then @code{gdb} itself. The configured source files, and the
14532 binaries, are left in the corresponding source directories.
14535 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
14536 system does not recognize this automatically when you run a different
14537 shell, you may need to run @code{sh} on it explicitly:
14540 sh configure @var{host}
14543 If you run @code{configure} from a directory that contains source
14544 directories for multiple libraries or programs, such as the
14545 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
14546 creates configuration files for every directory level underneath (unless
14547 you tell it not to, with the @samp{--norecursion} option).
14549 You can run the @code{configure} script from any of the
14550 subordinate directories in the @value{GDBN} distribution if you only want to
14551 configure that subdirectory, but be sure to specify a path to it.
14553 For example, with version @value{GDBVN}, type the following to configure only
14554 the @code{bfd} subdirectory:
14558 cd gdb-@value{GDBVN}/bfd
14559 ../configure @var{host}
14563 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
14564 However, you should make sure that the shell on your path (named by
14565 the @samp{SHELL} environment variable) is publicly readable. Remember
14566 that @value{GDBN} uses the shell to start your program---some systems refuse to
14567 let @value{GDBN} debug child processes whose programs are not readable.
14570 * Separate Objdir:: Compiling @value{GDBN} in another directory
14571 * Config Names:: Specifying names for hosts and targets
14572 * Configure Options:: Summary of options for configure
14575 @node Separate Objdir
14576 @section Compiling @value{GDBN} in another directory
14578 If you want to run @value{GDBN} versions for several host or target machines,
14579 you need a different @code{gdb} compiled for each combination of
14580 host and target. @code{configure} is designed to make this easy by
14581 allowing you to generate each configuration in a separate subdirectory,
14582 rather than in the source directory. If your @code{make} program
14583 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
14584 @code{make} in each of these directories builds the @code{gdb}
14585 program specified there.
14587 To build @code{gdb} in a separate directory, run @code{configure}
14588 with the @samp{--srcdir} option to specify where to find the source.
14589 (You also need to specify a path to find @code{configure}
14590 itself from your working directory. If the path to @code{configure}
14591 would be the same as the argument to @samp{--srcdir}, you can leave out
14592 the @samp{--srcdir} option; it is assumed.)
14594 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
14595 separate directory for a Sun 4 like this:
14599 cd gdb-@value{GDBVN}
14602 ../gdb-@value{GDBVN}/configure sun4
14607 When @code{configure} builds a configuration using a remote source
14608 directory, it creates a tree for the binaries with the same structure
14609 (and using the same names) as the tree under the source directory. In
14610 the example, you'd find the Sun 4 library @file{libiberty.a} in the
14611 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
14612 @file{gdb-sun4/gdb}.
14614 One popular reason to build several @value{GDBN} configurations in separate
14615 directories is to configure @value{GDBN} for cross-compiling (where
14616 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
14617 programs that run on another machine---the @dfn{target}).
14618 You specify a cross-debugging target by
14619 giving the @samp{--target=@var{target}} option to @code{configure}.
14621 When you run @code{make} to build a program or library, you must run
14622 it in a configured directory---whatever directory you were in when you
14623 called @code{configure} (or one of its subdirectories).
14625 The @code{Makefile} that @code{configure} generates in each source
14626 directory also runs recursively. If you type @code{make} in a source
14627 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
14628 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
14629 will build all the required libraries, and then build GDB.
14631 When you have multiple hosts or targets configured in separate
14632 directories, you can run @code{make} on them in parallel (for example,
14633 if they are NFS-mounted on each of the hosts); they will not interfere
14637 @section Specifying names for hosts and targets
14639 The specifications used for hosts and targets in the @code{configure}
14640 script are based on a three-part naming scheme, but some short predefined
14641 aliases are also supported. The full naming scheme encodes three pieces
14642 of information in the following pattern:
14645 @var{architecture}-@var{vendor}-@var{os}
14648 For example, you can use the alias @code{sun4} as a @var{host} argument,
14649 or as the value for @var{target} in a @code{--target=@var{target}}
14650 option. The equivalent full name is @samp{sparc-sun-sunos4}.
14652 The @code{configure} script accompanying @value{GDBN} does not provide
14653 any query facility to list all supported host and target names or
14654 aliases. @code{configure} calls the Bourne shell script
14655 @code{config.sub} to map abbreviations to full names; you can read the
14656 script, if you wish, or you can use it to test your guesses on
14657 abbreviations---for example:
14660 % sh config.sub i386-linux
14662 % sh config.sub alpha-linux
14663 alpha-unknown-linux-gnu
14664 % sh config.sub hp9k700
14666 % sh config.sub sun4
14667 sparc-sun-sunos4.1.1
14668 % sh config.sub sun3
14669 m68k-sun-sunos4.1.1
14670 % sh config.sub i986v
14671 Invalid configuration `i986v': machine `i986v' not recognized
14675 @code{config.sub} is also distributed in the @value{GDBN} source
14676 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
14678 @node Configure Options
14679 @section @code{configure} options
14681 Here is a summary of the @code{configure} options and arguments that
14682 are most often useful for building @value{GDBN}. @code{configure} also has
14683 several other options not listed here. @inforef{What Configure
14684 Does,,configure.info}, for a full explanation of @code{configure}.
14687 configure @r{[}--help@r{]}
14688 @r{[}--prefix=@var{dir}@r{]}
14689 @r{[}--exec-prefix=@var{dir}@r{]}
14690 @r{[}--srcdir=@var{dirname}@r{]}
14691 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
14692 @r{[}--target=@var{target}@r{]}
14697 You may introduce options with a single @samp{-} rather than
14698 @samp{--} if you prefer; but you may abbreviate option names if you use
14703 Display a quick summary of how to invoke @code{configure}.
14705 @item --prefix=@var{dir}
14706 Configure the source to install programs and files under directory
14709 @item --exec-prefix=@var{dir}
14710 Configure the source to install programs under directory
14713 @c avoid splitting the warning from the explanation:
14715 @item --srcdir=@var{dirname}
14716 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
14717 @code{make} that implements the @code{VPATH} feature.}@*
14718 Use this option to make configurations in directories separate from the
14719 @value{GDBN} source directories. Among other things, you can use this to
14720 build (or maintain) several configurations simultaneously, in separate
14721 directories. @code{configure} writes configuration specific files in
14722 the current directory, but arranges for them to use the source in the
14723 directory @var{dirname}. @code{configure} creates directories under
14724 the working directory in parallel to the source directories below
14727 @item --norecursion
14728 Configure only the directory level where @code{configure} is executed; do not
14729 propagate configuration to subdirectories.
14731 @item --target=@var{target}
14732 Configure @value{GDBN} for cross-debugging programs running on the specified
14733 @var{target}. Without this option, @value{GDBN} is configured to debug
14734 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
14736 There is no convenient way to generate a list of all available targets.
14738 @item @var{host} @dots{}
14739 Configure @value{GDBN} to run on the specified @var{host}.
14741 There is no convenient way to generate a list of all available hosts.
14744 There are many other options available as well, but they are generally
14745 needed for special purposes only.
14747 @node Maintenance Commands
14748 @appendix Maintenance Commands
14749 @cindex maintenance commands
14750 @cindex internal commands
14752 In addition to commands intended for @value{GDBN} users, @value{GDBN}
14753 includes a number of commands intended for @value{GDBN} developers.
14754 These commands are provided here for reference.
14757 @kindex maint info breakpoints
14758 @item @anchor{maint info breakpoints}maint info breakpoints
14759 Using the same format as @samp{info breakpoints}, display both the
14760 breakpoints you've set explicitly, and those @value{GDBN} is using for
14761 internal purposes. Internal breakpoints are shown with negative
14762 breakpoint numbers. The type column identifies what kind of breakpoint
14767 Normal, explicitly set breakpoint.
14770 Normal, explicitly set watchpoint.
14773 Internal breakpoint, used to handle correctly stepping through
14774 @code{longjmp} calls.
14776 @item longjmp resume
14777 Internal breakpoint at the target of a @code{longjmp}.
14780 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
14783 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
14786 Shared library events.
14790 @kindex maint internal-error
14791 @kindex maint internal-warning
14792 @item maint internal-error
14793 @itemx maint internal-warning
14794 Cause @value{GDBN} to call the internal function @code{internal_error}
14795 or @code{internal_warning} and hence behave as though an internal error
14796 or internal warning has been detected. In addition to reporting the
14797 internal problem, these functions give the user the opportunity to
14798 either quit @value{GDBN} or create a core file of the current
14799 @value{GDBN} session.
14802 (gdb) @kbd{maint internal-error testing, 1, 2}
14803 @dots{}/maint.c:121: internal-error: testing, 1, 2
14804 A problem internal to GDB has been detected. Further
14805 debugging may prove unreliable.
14806 Quit this debugging session? (y or n) @kbd{n}
14807 Create a core file? (y or n) @kbd{n}
14811 Takes an optional parameter that is used as the text of the error or
14814 @kindex maint print registers
14815 @kindex maint print raw-registers
14816 @kindex maint print cooked-registers
14817 @item maint print registers
14818 @itemx maint print raw-registers
14819 @itemx maint print cooked-registers
14820 Print @value{GDBN}'s internal register data structures.
14822 The command @samp{maint print raw-registers} includes the contents of
14823 the raw register cache; and the command @samp{maint print
14824 cooked-registers} includes the (cooked) value of all registers.
14825 @xref{Registers,, Registers, gdbint, @value{GDBN} Internals}.
14827 Takes an optional file parameter.
14832 @node Remote Protocol
14833 @appendix @value{GDBN} Remote Serial Protocol
14838 * Stop Reply Packets::
14839 * General Query Packets::
14840 * Register Packet Format::
14847 There may be occasions when you need to know something about the
14848 protocol---for example, if there is only one serial port to your target
14849 machine, you might want your program to do something special if it
14850 recognizes a packet meant for @value{GDBN}.
14852 In the examples below, @samp{->} and @samp{<-} are used to indicate
14853 transmitted and received data respectfully.
14855 @cindex protocol, @value{GDBN} remote serial
14856 @cindex serial protocol, @value{GDBN} remote
14857 @cindex remote serial protocol
14858 All @value{GDBN} commands and responses (other than acknowledgments) are
14859 sent as a @var{packet}. A @var{packet} is introduced with the character
14860 @samp{$}, the actual @var{packet-data}, and the terminating character
14861 @samp{#} followed by a two-digit @var{checksum}:
14864 @code{$}@var{packet-data}@code{#}@var{checksum}
14868 @cindex checksum, for @value{GDBN} remote
14870 The two-digit @var{checksum} is computed as the modulo 256 sum of all
14871 characters between the leading @samp{$} and the trailing @samp{#} (an
14872 eight bit unsigned checksum).
14874 Implementors should note that prior to @value{GDBN} 5.0 the protocol
14875 specification also included an optional two-digit @var{sequence-id}:
14878 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
14881 @cindex sequence-id, for @value{GDBN} remote
14883 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
14884 has never output @var{sequence-id}s. Stubs that handle packets added
14885 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
14887 @cindex acknowledgment, for @value{GDBN} remote
14888 When either the host or the target machine receives a packet, the first
14889 response expected is an acknowledgment: either @samp{+} (to indicate
14890 the package was received correctly) or @samp{-} (to request
14894 -> @code{$}@var{packet-data}@code{#}@var{checksum}
14899 The host (@value{GDBN}) sends @var{command}s, and the target (the
14900 debugging stub incorporated in your program) sends a @var{response}. In
14901 the case of step and continue @var{command}s, the response is only sent
14902 when the operation has completed (the target has again stopped).
14904 @var{packet-data} consists of a sequence of characters with the
14905 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
14908 Fields within the packet should be separated using @samp{,} @samp{;} or
14909 @cindex remote protocol, field separator
14910 @samp{:}. Except where otherwise noted all numbers are represented in
14911 @sc{hex} with leading zeros suppressed.
14913 Implementors should note that prior to @value{GDBN} 5.0, the character
14914 @samp{:} could not appear as the third character in a packet (as it
14915 would potentially conflict with the @var{sequence-id}).
14917 Response @var{data} can be run-length encoded to save space. A @samp{*}
14918 means that the next character is an @sc{ascii} encoding giving a repeat count
14919 which stands for that many repetitions of the character preceding the
14920 @samp{*}. The encoding is @code{n+29}, yielding a printable character
14921 where @code{n >=3} (which is where rle starts to win). The printable
14922 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
14923 value greater than 126 should not be used.
14925 Some remote systems have used a different run-length encoding mechanism
14926 loosely refered to as the cisco encoding. Following the @samp{*}
14927 character are two hex digits that indicate the size of the packet.
14934 means the same as "0000".
14936 The error response returned for some packets includes a two character
14937 error number. That number is not well defined.
14939 For any @var{command} not supported by the stub, an empty response
14940 (@samp{$#00}) should be returned. That way it is possible to extend the
14941 protocol. A newer @value{GDBN} can tell if a packet is supported based
14944 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
14945 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
14951 The following table provides a complete list of all currently defined
14952 @var{command}s and their corresponding response @var{data}.
14956 @item @code{!} --- extended mode
14957 @cindex @code{!} packet
14959 Enable extended mode. In extended mode, the remote server is made
14960 persistent. The @samp{R} packet is used to restart the program being
14966 The remote target both supports and has enabled extended mode.
14969 @item @code{?} --- last signal
14970 @cindex @code{?} packet
14972 Indicate the reason the target halted. The reply is the same as for
14976 @xref{Stop Reply Packets}, for the reply specifications.
14978 @item @code{a} --- reserved
14980 Reserved for future use.
14982 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
14983 @cindex @code{A} packet
14985 Initialized @samp{argv[]} array passed into program. @var{arglen}
14986 specifies the number of bytes in the hex encoded byte stream @var{arg}.
14987 See @code{gdbserver} for more details.
14995 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
14996 @cindex @code{b} packet
14998 Change the serial line speed to @var{baud}.
15000 JTC: @emph{When does the transport layer state change? When it's
15001 received, or after the ACK is transmitted. In either case, there are
15002 problems if the command or the acknowledgment packet is dropped.}
15004 Stan: @emph{If people really wanted to add something like this, and get
15005 it working for the first time, they ought to modify ser-unix.c to send
15006 some kind of out-of-band message to a specially-setup stub and have the
15007 switch happen "in between" packets, so that from remote protocol's point
15008 of view, nothing actually happened.}
15010 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
15011 @cindex @code{B} packet
15013 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
15014 breakpoint at @var{addr}.
15016 This packet has been replaced by the @samp{Z} and @samp{z} packets
15017 (@pxref{insert breakpoint or watchpoint packet}).
15019 @item @code{c}@var{addr} --- continue
15020 @cindex @code{c} packet
15022 @var{addr} is address to resume. If @var{addr} is omitted, resume at
15026 @xref{Stop Reply Packets}, for the reply specifications.
15028 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
15029 @cindex @code{C} packet
15031 Continue with signal @var{sig} (hex signal number). If
15032 @code{;}@var{addr} is omitted, resume at same address.
15035 @xref{Stop Reply Packets}, for the reply specifications.
15037 @item @code{d} --- toggle debug @strong{(deprecated)}
15038 @cindex @code{d} packet
15042 @item @code{D} --- detach
15043 @cindex @code{D} packet
15045 Detach @value{GDBN} from the remote system. Sent to the remote target
15046 before @value{GDBN} disconnects.
15050 @item @emph{no response}
15051 @value{GDBN} does not check for any response after sending this packet.
15054 @item @code{e} --- reserved
15056 Reserved for future use.
15058 @item @code{E} --- reserved
15060 Reserved for future use.
15062 @item @code{f} --- reserved
15064 Reserved for future use.
15066 @item @code{F} --- reserved
15068 Reserved for future use.
15070 @item @code{g} --- read registers
15071 @anchor{read registers packet}
15072 @cindex @code{g} packet
15074 Read general registers.
15078 @item @var{XX@dots{}}
15079 Each byte of register data is described by two hex digits. The bytes
15080 with the register are transmitted in target byte order. The size of
15081 each register and their position within the @samp{g} @var{packet} are
15082 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
15083 and @var{REGISTER_NAME} macros. The specification of several standard
15084 @code{g} packets is specified below.
15089 @item @code{G}@var{XX@dots{}} --- write regs
15090 @cindex @code{G} packet
15092 @xref{read registers packet}, for a description of the @var{XX@dots{}}
15103 @item @code{h} --- reserved
15105 Reserved for future use.
15107 @item @code{H}@var{c}@var{t@dots{}} --- set thread
15108 @cindex @code{H} packet
15110 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
15111 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
15112 should be @samp{c} for step and continue operations, @samp{g} for other
15113 operations. The thread designator @var{t@dots{}} may be -1, meaning all
15114 the threads, a thread number, or zero which means pick any thread.
15125 @c 'H': How restrictive (or permissive) is the thread model. If a
15126 @c thread is selected and stopped, are other threads allowed
15127 @c to continue to execute? As I mentioned above, I think the
15128 @c semantics of each command when a thread is selected must be
15129 @c described. For example:
15131 @c 'g': If the stub supports threads and a specific thread is
15132 @c selected, returns the register block from that thread;
15133 @c otherwise returns current registers.
15135 @c 'G' If the stub supports threads and a specific thread is
15136 @c selected, sets the registers of the register block of
15137 @c that thread; otherwise sets current registers.
15139 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
15140 @anchor{cycle step packet}
15141 @cindex @code{i} packet
15143 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
15144 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
15145 step starting at that address.
15147 @item @code{I} --- signal then cycle step @strong{(reserved)}
15148 @cindex @code{I} packet
15150 @xref{step with signal packet}. @xref{cycle step packet}.
15152 @item @code{j} --- reserved
15154 Reserved for future use.
15156 @item @code{J} --- reserved
15158 Reserved for future use.
15160 @item @code{k} --- kill request
15161 @cindex @code{k} packet
15163 FIXME: @emph{There is no description of how to operate when a specific
15164 thread context has been selected (i.e.@: does 'k' kill only that
15167 @item @code{K} --- reserved
15169 Reserved for future use.
15171 @item @code{l} --- reserved
15173 Reserved for future use.
15175 @item @code{L} --- reserved
15177 Reserved for future use.
15179 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
15180 @cindex @code{m} packet
15182 Read @var{length} bytes of memory starting at address @var{addr}.
15183 Neither @value{GDBN} nor the stub assume that sized memory transfers are
15184 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
15185 transfer mechanism is needed.}
15189 @item @var{XX@dots{}}
15190 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
15191 to read only part of the data. Neither @value{GDBN} nor the stub assume
15192 that sized memory transfers are assumed using word aligned
15193 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
15199 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
15200 @cindex @code{M} packet
15202 Write @var{length} bytes of memory starting at address @var{addr}.
15203 @var{XX@dots{}} is the data.
15210 for an error (this includes the case where only part of the data was
15214 @item @code{n} --- reserved
15216 Reserved for future use.
15218 @item @code{N} --- reserved
15220 Reserved for future use.
15222 @item @code{o} --- reserved
15224 Reserved for future use.
15226 @item @code{O} --- reserved
15228 Reserved for future use.
15230 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
15231 @cindex @code{p} packet
15233 @xref{write register packet}.
15237 @item @var{r@dots{}.}
15238 The hex encoded value of the register in target byte order.
15241 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
15242 @anchor{write register packet}
15243 @cindex @code{P} packet
15245 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
15246 digits for each byte in the register (target byte order).
15256 @item @code{q}@var{query} --- general query
15257 @anchor{general query packet}
15258 @cindex @code{q} packet
15260 Request info about @var{query}. In general @value{GDBN} queries have a
15261 leading upper case letter. Custom vendor queries should use a company
15262 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
15263 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
15264 that they match the full @var{query} name.
15268 @item @var{XX@dots{}}
15269 Hex encoded data from query. The reply can not be empty.
15273 Indicating an unrecognized @var{query}.
15276 @item @code{Q}@var{var}@code{=}@var{val} --- general set
15277 @cindex @code{Q} packet
15279 Set value of @var{var} to @var{val}.
15281 @xref{general query packet}, for a discussion of naming conventions.
15283 @item @code{r} --- reset @strong{(deprecated)}
15284 @cindex @code{r} packet
15286 Reset the entire system.
15288 @item @code{R}@var{XX} --- remote restart
15289 @cindex @code{R} packet
15291 Restart the program being debugged. @var{XX}, while needed, is ignored.
15292 This packet is only available in extended mode.
15296 @item @emph{no reply}
15297 The @samp{R} packet has no reply.
15300 @item @code{s}@var{addr} --- step
15301 @cindex @code{s} packet
15303 @var{addr} is address to resume. If @var{addr} is omitted, resume at
15307 @xref{Stop Reply Packets}, for the reply specifications.
15309 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
15310 @anchor{step with signal packet}
15311 @cindex @code{S} packet
15313 Like @samp{C} but step not continue.
15316 @xref{Stop Reply Packets}, for the reply specifications.
15318 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
15319 @cindex @code{t} packet
15321 Search backwards starting at address @var{addr} for a match with pattern
15322 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
15323 @var{addr} must be at least 3 digits.
15325 @item @code{T}@var{XX} --- thread alive
15326 @cindex @code{T} packet
15328 Find out if the thread XX is alive.
15333 thread is still alive
15338 @item @code{u} --- reserved
15340 Reserved for future use.
15342 @item @code{U} --- reserved
15344 Reserved for future use.
15346 @item @code{v} --- reserved
15348 Reserved for future use.
15350 @item @code{V} --- reserved
15352 Reserved for future use.
15354 @item @code{w} --- reserved
15356 Reserved for future use.
15358 @item @code{W} --- reserved
15360 Reserved for future use.
15362 @item @code{x} --- reserved
15364 Reserved for future use.
15366 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
15367 @cindex @code{X} packet
15369 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
15370 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
15371 escaped using @code{0x7d}.
15381 @item @code{y} --- reserved
15383 Reserved for future use.
15385 @item @code{Y} reserved
15387 Reserved for future use.
15389 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
15390 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
15391 @anchor{insert breakpoint or watchpoint packet}
15392 @cindex @code{z} packet
15393 @cindex @code{Z} packets
15395 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
15396 watchpoint starting at address @var{address} and covering the next
15397 @var{length} bytes.
15399 Each breakpoint and watchpoint packet @var{type} is documented
15402 @emph{Implementation notes: A remote target shall return an empty string
15403 for an unrecognized breakpoint or watchpoint packet @var{type}. A
15404 remote target shall support either both or neither of a given
15405 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
15406 avoid potential problems with duplicate packets, the operations should
15407 be implemented in an idempotent way.}
15409 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
15410 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
15411 @cindex @code{z0} packet
15412 @cindex @code{Z0} packet
15414 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
15415 @code{addr} of size @code{length}.
15417 A memory breakpoint is implemented by replacing the instruction at
15418 @var{addr} with a software breakpoint or trap instruction. The
15419 @code{length} is used by targets that indicates the size of the
15420 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
15421 @sc{mips} can insert either a 2 or 4 byte breakpoint).
15423 @emph{Implementation note: It is possible for a target to copy or move
15424 code that contains memory breakpoints (e.g., when implementing
15425 overlays). The behavior of this packet, in the presence of such a
15426 target, is not defined.}
15438 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
15439 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
15440 @cindex @code{z1} packet
15441 @cindex @code{Z1} packet
15443 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
15444 address @code{addr} of size @code{length}.
15446 A hardware breakpoint is implemented using a mechanism that is not
15447 dependant on being able to modify the target's memory.
15449 @emph{Implementation note: A hardware breakpoint is not affected by code
15462 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
15463 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
15464 @cindex @code{z2} packet
15465 @cindex @code{Z2} packet
15467 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
15479 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
15480 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
15481 @cindex @code{z3} packet
15482 @cindex @code{Z3} packet
15484 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
15496 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
15497 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
15498 @cindex @code{z4} packet
15499 @cindex @code{Z4} packet
15501 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
15515 @node Stop Reply Packets
15516 @section Stop Reply Packets
15517 @cindex stop reply packets
15519 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
15520 receive any of the below as a reply. In the case of the @samp{C},
15521 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
15522 when the target halts. In the below the exact meaning of @samp{signal
15523 number} is poorly defined. In general one of the UNIX signal numbering
15524 conventions is used.
15529 @var{AA} is the signal number
15531 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
15532 @cindex @code{T} packet reply
15534 @var{AA} = two hex digit signal number; @var{n...} = register number
15535 (hex), @var{r...} = target byte ordered register contents, size defined
15536 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
15537 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
15538 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
15539 integer; @var{n...} = other string not starting with valid hex digit.
15540 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
15541 to the next. This way we can extend the protocol.
15545 The process exited, and @var{AA} is the exit status. This is only
15546 applicable to certain targets.
15550 The process terminated with signal @var{AA}.
15552 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
15554 @var{AA} = signal number; @var{t@dots{}} = address of symbol
15555 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
15556 base of bss section. @emph{Note: only used by Cisco Systems targets.
15557 The difference between this reply and the @samp{qOffsets} query is that
15558 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
15559 is a query initiated by the host debugger.}
15561 @item O@var{XX@dots{}}
15563 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
15564 any time while the program is running and the debugger should continue
15565 to wait for @samp{W}, @samp{T}, etc.
15569 @node General Query Packets
15570 @section General Query Packets
15572 The following set and query packets have already been defined.
15576 @item @code{q}@code{C} --- current thread
15578 Return the current thread id.
15582 @item @code{QC}@var{pid}
15583 Where @var{pid} is a HEX encoded 16 bit process id.
15585 Any other reply implies the old pid.
15588 @item @code{q}@code{fThreadInfo} -- all thread ids
15590 @code{q}@code{sThreadInfo}
15592 Obtain a list of active thread ids from the target (OS). Since there
15593 may be too many active threads to fit into one reply packet, this query
15594 works iteratively: it may require more than one query/reply sequence to
15595 obtain the entire list of threads. The first query of the sequence will
15596 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
15597 sequence will be the @code{qs}@code{ThreadInfo} query.
15599 NOTE: replaces the @code{qL} query (see below).
15603 @item @code{m}@var{id}
15605 @item @code{m}@var{id},@var{id}@dots{}
15606 a comma-separated list of thread ids
15608 (lower case 'el') denotes end of list.
15611 In response to each query, the target will reply with a list of one or
15612 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
15613 will respond to each reply with a request for more thread ids (using the
15614 @code{qs} form of the query), until the target responds with @code{l}
15615 (lower-case el, for @code{'last'}).
15617 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
15619 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
15620 string description of a thread's attributes from the target OS. This
15621 string may contain anything that the target OS thinks is interesting for
15622 @value{GDBN} to tell the user about the thread. The string is displayed
15623 in @value{GDBN}'s @samp{info threads} display. Some examples of
15624 possible thread extra info strings are ``Runnable'', or ``Blocked on
15629 @item @var{XX@dots{}}
15630 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
15631 the printable string containing the extra information about the thread's
15635 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
15637 Obtain thread information from RTOS. Where: @var{startflag} (one hex
15638 digit) is one to indicate the first query and zero to indicate a
15639 subsequent query; @var{threadcount} (two hex digits) is the maximum
15640 number of threads the response packet can contain; and @var{nextthread}
15641 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
15642 returned in the response as @var{argthread}.
15644 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
15649 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
15650 Where: @var{count} (two hex digits) is the number of threads being
15651 returned; @var{done} (one hex digit) is zero to indicate more threads
15652 and one indicates no further threads; @var{argthreadid} (eight hex
15653 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
15654 is a sequence of thread IDs from the target. @var{threadid} (eight hex
15655 digits). See @code{remote.c:parse_threadlist_response()}.
15658 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
15662 @item @code{E}@var{NN}
15663 An error (such as memory fault)
15664 @item @code{C}@var{CRC32}
15665 A 32 bit cyclic redundancy check of the specified memory region.
15668 @item @code{q}@code{Offsets} --- query sect offs
15670 Get section offsets that the target used when re-locating the downloaded
15671 image. @emph{Note: while a @code{Bss} offset is included in the
15672 response, @value{GDBN} ignores this and instead applies the @code{Data}
15673 offset to the @code{Bss} section.}
15677 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
15680 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
15682 Returns information on @var{threadid}. Where: @var{mode} is a hex
15683 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
15690 See @code{remote.c:remote_unpack_thread_info_response()}.
15692 @item @code{q}@code{Rcmd,}@var{command} --- remote command
15694 @var{command} (hex encoded) is passed to the local interpreter for
15695 execution. Invalid commands should be reported using the output string.
15696 Before the final result packet, the target may also respond with a
15697 number of intermediate @code{O}@var{output} console output packets.
15698 @emph{Implementors should note that providing access to a stubs's
15699 interpreter may have security implications}.
15704 A command response with no output.
15706 A command response with the hex encoded output string @var{OUTPUT}.
15707 @item @code{E}@var{NN}
15708 Indicate a badly formed request.
15710 When @samp{q}@samp{Rcmd} is not recognized.
15713 @item @code{qSymbol::} --- symbol lookup
15715 Notify the target that @value{GDBN} is prepared to serve symbol lookup
15716 requests. Accept requests from the target for the values of symbols.
15721 The target does not need to look up any (more) symbols.
15722 @item @code{qSymbol:}@var{sym_name}
15723 The target requests the value of symbol @var{sym_name} (hex encoded).
15724 @value{GDBN} may provide the value by using the
15725 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
15728 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
15730 Set the value of @var{sym_name} to @var{sym_value}.
15732 @var{sym_name} (hex encoded) is the name of a symbol whose value the
15733 target has previously requested.
15735 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
15736 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
15742 The target does not need to look up any (more) symbols.
15743 @item @code{qSymbol:}@var{sym_name}
15744 The target requests the value of a new symbol @var{sym_name} (hex
15745 encoded). @value{GDBN} will continue to supply the values of symbols
15746 (if available), until the target ceases to request them.
15751 @node Register Packet Format
15752 @section Register Packet Format
15754 The following @samp{g}/@samp{G} packets have previously been defined.
15755 In the below, some thirty-two bit registers are transferred as
15756 sixty-four bits. Those registers should be zero/sign extended (which?)
15757 to fill the space allocated. Register bytes are transfered in target
15758 byte order. The two nibbles within a register byte are transfered
15759 most-significant - least-significant.
15765 All registers are transfered as thirty-two bit quantities in the order:
15766 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
15767 registers; fsr; fir; fp.
15771 All registers are transfered as sixty-four bit quantities (including
15772 thirty-two bit registers such as @code{sr}). The ordering is the same
15780 Example sequence of a target being re-started. Notice how the restart
15781 does not get any direct output:
15786 @emph{target restarts}
15789 <- @code{T001:1234123412341234}
15793 Example sequence of a target being stepped by a single instruction:
15796 -> @code{G1445@dots{}}
15801 <- @code{T001:1234123412341234}
15805 <- @code{1455@dots{}}
15819 % I think something like @colophon should be in texinfo. In the
15821 \long\def\colophon{\hbox to0pt{}\vfill
15822 \centerline{The body of this manual is set in}
15823 \centerline{\fontname\tenrm,}
15824 \centerline{with headings in {\bf\fontname\tenbf}}
15825 \centerline{and examples in {\tt\fontname\tentt}.}
15826 \centerline{{\it\fontname\tenit\/},}
15827 \centerline{{\bf\fontname\tenbf}, and}
15828 \centerline{{\sl\fontname\tensl\/}}
15829 \centerline{are used for emphasis.}\vfill}
15831 % Blame: doc@cygnus.com, 1991.