1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 @ifset VERSION_PACKAGE
53 @value{VERSION_PACKAGE}
55 Version @value{GDBVN}.
57 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
58 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
59 Free Software Foundation, Inc.
61 Permission is granted to copy, distribute and/or modify this document
62 under the terms of the GNU Free Documentation License, Version 1.1 or
63 any later version published by the Free Software Foundation; with the
64 Invariant Sections being ``Free Software'' and ``Free Software Needs
65 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
66 and with the Back-Cover Texts as in (a) below.
68 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
69 this GNU Manual. Buying copies from GNU Press supports the FSF in
70 developing GNU and promoting software freedom.''
74 @title Debugging with @value{GDBN}
75 @subtitle The @sc{gnu} Source-Level Debugger
77 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
78 @ifset VERSION_PACKAGE
80 @subtitle @value{VERSION_PACKAGE}
82 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
86 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
87 \hfill {\it Debugging with @value{GDBN}}\par
88 \hfill \TeX{}info \texinfoversion\par
92 @vskip 0pt plus 1filll
93 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
94 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
95 Free Software Foundation, Inc.
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.1 or
104 any later version published by the Free Software Foundation; with the
105 Invariant Sections being ``Free Software'' and ``Free Software Needs
106 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
107 and with the Back-Cover Texts as in (a) below.
109 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
110 this GNU Manual. Buying copies from GNU Press supports the FSF in
111 developing GNU and promoting software freedom.''
113 This edition of the GDB manual is dedicated to the memory of Fred
114 Fish. Fred was a long-standing contributor to GDB and to Free
115 software in general. We will miss him.
120 @node Top, Summary, (dir), (dir)
122 @top Debugging with @value{GDBN}
124 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
126 This is the @value{EDITION} Edition, for @value{GDBN}
127 @ifset VERSION_PACKAGE
128 @value{VERSION_PACKAGE}
130 Version @value{GDBVN}.
132 Copyright (C) 1988-2006 Free Software Foundation, Inc.
134 This edition of the GDB manual is dedicated to the memory of Fred
135 Fish. Fred was a long-standing contributor to GDB and to Free
136 software in general. We will miss him.
139 * Summary:: Summary of @value{GDBN}
140 * Sample Session:: A sample @value{GDBN} session
142 * Invocation:: Getting in and out of @value{GDBN}
143 * Commands:: @value{GDBN} commands
144 * Running:: Running programs under @value{GDBN}
145 * Stopping:: Stopping and continuing
146 * Reverse Execution:: Running programs backward
147 * Stack:: Examining the stack
148 * Source:: Examining source files
149 * Data:: Examining data
150 * Macros:: Preprocessor Macros
151 * Tracepoints:: Debugging remote targets non-intrusively
152 * Overlays:: Debugging programs that use overlays
154 * Languages:: Using @value{GDBN} with different languages
156 * Symbols:: Examining the symbol table
157 * Altering:: Altering execution
158 * GDB Files:: @value{GDBN} files
159 * Targets:: Specifying a debugging target
160 * Remote Debugging:: Debugging remote programs
161 * Configurations:: Configuration-specific information
162 * Controlling GDB:: Controlling @value{GDBN}
163 * Extending GDB:: Extending @value{GDBN}
164 * Interpreters:: Command Interpreters
165 * TUI:: @value{GDBN} Text User Interface
166 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
167 * GDB/MI:: @value{GDBN}'s Machine Interface.
168 * Annotations:: @value{GDBN}'s annotation interface.
170 * GDB Bugs:: Reporting bugs in @value{GDBN}
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
174 * Formatting Documentation:: How to format and print @value{GDBN} documentation
175 * Installing GDB:: Installing GDB
176 * Maintenance Commands:: Maintenance Commands
177 * Remote Protocol:: GDB Remote Serial Protocol
178 * Agent Expressions:: The GDB Agent Expression Mechanism
179 * Target Descriptions:: How targets can describe themselves to
181 * Copying:: GNU General Public License says
182 how you can copy and share GDB
183 * GNU Free Documentation License:: The license for this documentation
192 @unnumbered Summary of @value{GDBN}
194 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
195 going on ``inside'' another program while it executes---or what another
196 program was doing at the moment it crashed.
198 @value{GDBN} can do four main kinds of things (plus other things in support of
199 these) to help you catch bugs in the act:
203 Start your program, specifying anything that might affect its behavior.
206 Make your program stop on specified conditions.
209 Examine what has happened, when your program has stopped.
212 Change things in your program, so you can experiment with correcting the
213 effects of one bug and go on to learn about another.
216 You can use @value{GDBN} to debug programs written in C and C@t{++}.
217 For more information, see @ref{Supported Languages,,Supported Languages}.
218 For more information, see @ref{C,,C and C++}.
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
525 @chapter A Sample @value{GDBN} Session
527 You can use this manual at your leisure to read all about @value{GDBN}.
528 However, a handful of commands are enough to get started using the
529 debugger. This chapter illustrates those commands.
532 In this sample session, we emphasize user input like this: @b{input},
533 to make it easier to pick out from the surrounding output.
536 @c FIXME: this example may not be appropriate for some configs, where
537 @c FIXME...primary interest is in remote use.
539 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
540 processor) exhibits the following bug: sometimes, when we change its
541 quote strings from the default, the commands used to capture one macro
542 definition within another stop working. In the following short @code{m4}
543 session, we define a macro @code{foo} which expands to @code{0000}; we
544 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
545 same thing. However, when we change the open quote string to
546 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
547 procedure fails to define a new synonym @code{baz}:
556 @b{define(bar,defn(`foo'))}
560 @b{changequote(<QUOTE>,<UNQUOTE>)}
562 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
565 m4: End of input: 0: fatal error: EOF in string
569 Let us use @value{GDBN} to try to see what is going on.
572 $ @b{@value{GDBP} m4}
573 @c FIXME: this falsifies the exact text played out, to permit smallbook
574 @c FIXME... format to come out better.
575 @value{GDBN} is free software and you are welcome to distribute copies
576 of it under certain conditions; type "show copying" to see
578 There is absolutely no warranty for @value{GDBN}; type "show warranty"
581 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
586 @value{GDBN} reads only enough symbol data to know where to find the
587 rest when needed; as a result, the first prompt comes up very quickly.
588 We now tell @value{GDBN} to use a narrower display width than usual, so
589 that examples fit in this manual.
592 (@value{GDBP}) @b{set width 70}
596 We need to see how the @code{m4} built-in @code{changequote} works.
597 Having looked at the source, we know the relevant subroutine is
598 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
599 @code{break} command.
602 (@value{GDBP}) @b{break m4_changequote}
603 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
607 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
608 control; as long as control does not reach the @code{m4_changequote}
609 subroutine, the program runs as usual:
612 (@value{GDBP}) @b{run}
613 Starting program: /work/Editorial/gdb/gnu/m4/m4
621 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
622 suspends execution of @code{m4}, displaying information about the
623 context where it stops.
626 @b{changequote(<QUOTE>,<UNQUOTE>)}
628 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
630 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
634 Now we use the command @code{n} (@code{next}) to advance execution to
635 the next line of the current function.
639 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
644 @code{set_quotes} looks like a promising subroutine. We can go into it
645 by using the command @code{s} (@code{step}) instead of @code{next}.
646 @code{step} goes to the next line to be executed in @emph{any}
647 subroutine, so it steps into @code{set_quotes}.
651 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
653 530 if (lquote != def_lquote)
657 The display that shows the subroutine where @code{m4} is now
658 suspended (and its arguments) is called a stack frame display. It
659 shows a summary of the stack. We can use the @code{backtrace}
660 command (which can also be spelled @code{bt}), to see where we are
661 in the stack as a whole: the @code{backtrace} command displays a
662 stack frame for each active subroutine.
665 (@value{GDBP}) @b{bt}
666 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
668 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
670 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
671 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
673 #4 0x79dc in expand_input () at macro.c:40
674 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
678 We step through a few more lines to see what happens. The first two
679 times, we can use @samp{s}; the next two times we use @code{n} to avoid
680 falling into the @code{xstrdup} subroutine.
684 0x3b5c 532 if (rquote != def_rquote)
686 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
687 def_lquote : xstrdup(lq);
689 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
692 538 len_lquote = strlen(rquote);
696 The last line displayed looks a little odd; we can examine the variables
697 @code{lquote} and @code{rquote} to see if they are in fact the new left
698 and right quotes we specified. We use the command @code{p}
699 (@code{print}) to see their values.
702 (@value{GDBP}) @b{p lquote}
703 $1 = 0x35d40 "<QUOTE>"
704 (@value{GDBP}) @b{p rquote}
705 $2 = 0x35d50 "<UNQUOTE>"
709 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
710 To look at some context, we can display ten lines of source
711 surrounding the current line with the @code{l} (@code{list}) command.
717 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
723 539 len_rquote = strlen(lquote);
730 Let us step past the two lines that set @code{len_lquote} and
731 @code{len_rquote}, and then examine the values of those variables.
735 539 len_rquote = strlen(lquote);
738 (@value{GDBP}) @b{p len_lquote}
740 (@value{GDBP}) @b{p len_rquote}
745 That certainly looks wrong, assuming @code{len_lquote} and
746 @code{len_rquote} are meant to be the lengths of @code{lquote} and
747 @code{rquote} respectively. We can set them to better values using
748 the @code{p} command, since it can print the value of
749 any expression---and that expression can include subroutine calls and
753 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
755 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
760 Is that enough to fix the problem of using the new quotes with the
761 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
762 executing with the @code{c} (@code{continue}) command, and then try the
763 example that caused trouble initially:
769 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
776 Success! The new quotes now work just as well as the default ones. The
777 problem seems to have been just the two typos defining the wrong
778 lengths. We allow @code{m4} exit by giving it an EOF as input:
782 Program exited normally.
786 The message @samp{Program exited normally.} is from @value{GDBN}; it
787 indicates @code{m4} has finished executing. We can end our @value{GDBN}
788 session with the @value{GDBN} @code{quit} command.
791 (@value{GDBP}) @b{quit}
795 @chapter Getting In and Out of @value{GDBN}
797 This chapter discusses how to start @value{GDBN}, and how to get out of it.
801 type @samp{@value{GDBP}} to start @value{GDBN}.
803 type @kbd{quit} or @kbd{Ctrl-d} to exit.
807 * Invoking GDB:: How to start @value{GDBN}
808 * Quitting GDB:: How to quit @value{GDBN}
809 * Shell Commands:: How to use shell commands inside @value{GDBN}
810 * Logging Output:: How to log @value{GDBN}'s output to a file
814 @section Invoking @value{GDBN}
816 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
817 @value{GDBN} reads commands from the terminal until you tell it to exit.
819 You can also run @code{@value{GDBP}} with a variety of arguments and options,
820 to specify more of your debugging environment at the outset.
822 The command-line options described here are designed
823 to cover a variety of situations; in some environments, some of these
824 options may effectively be unavailable.
826 The most usual way to start @value{GDBN} is with one argument,
827 specifying an executable program:
830 @value{GDBP} @var{program}
834 You can also start with both an executable program and a core file
838 @value{GDBP} @var{program} @var{core}
841 You can, instead, specify a process ID as a second argument, if you want
842 to debug a running process:
845 @value{GDBP} @var{program} 1234
849 would attach @value{GDBN} to process @code{1234} (unless you also have a file
850 named @file{1234}; @value{GDBN} does check for a core file first).
852 Taking advantage of the second command-line argument requires a fairly
853 complete operating system; when you use @value{GDBN} as a remote
854 debugger attached to a bare board, there may not be any notion of
855 ``process'', and there is often no way to get a core dump. @value{GDBN}
856 will warn you if it is unable to attach or to read core dumps.
858 You can optionally have @code{@value{GDBP}} pass any arguments after the
859 executable file to the inferior using @code{--args}. This option stops
862 @value{GDBP} --args gcc -O2 -c foo.c
864 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
865 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
867 You can run @code{@value{GDBP}} without printing the front material, which describes
868 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
875 You can further control how @value{GDBN} starts up by using command-line
876 options. @value{GDBN} itself can remind you of the options available.
886 to display all available options and briefly describe their use
887 (@samp{@value{GDBP} -h} is a shorter equivalent).
889 All options and command line arguments you give are processed
890 in sequential order. The order makes a difference when the
891 @samp{-x} option is used.
895 * File Options:: Choosing files
896 * Mode Options:: Choosing modes
897 * Startup:: What @value{GDBN} does during startup
901 @subsection Choosing Files
903 When @value{GDBN} starts, it reads any arguments other than options as
904 specifying an executable file and core file (or process ID). This is
905 the same as if the arguments were specified by the @samp{-se} and
906 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
907 first argument that does not have an associated option flag as
908 equivalent to the @samp{-se} option followed by that argument; and the
909 second argument that does not have an associated option flag, if any, as
910 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
911 If the second argument begins with a decimal digit, @value{GDBN} will
912 first attempt to attach to it as a process, and if that fails, attempt
913 to open it as a corefile. If you have a corefile whose name begins with
914 a digit, you can prevent @value{GDBN} from treating it as a pid by
915 prefixing it with @file{./}, e.g.@: @file{./12345}.
917 If @value{GDBN} has not been configured to included core file support,
918 such as for most embedded targets, then it will complain about a second
919 argument and ignore it.
921 Many options have both long and short forms; both are shown in the
922 following list. @value{GDBN} also recognizes the long forms if you truncate
923 them, so long as enough of the option is present to be unambiguous.
924 (If you prefer, you can flag option arguments with @samp{--} rather
925 than @samp{-}, though we illustrate the more usual convention.)
927 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
928 @c way, both those who look for -foo and --foo in the index, will find
932 @item -symbols @var{file}
934 @cindex @code{--symbols}
936 Read symbol table from file @var{file}.
938 @item -exec @var{file}
940 @cindex @code{--exec}
942 Use file @var{file} as the executable file to execute when appropriate,
943 and for examining pure data in conjunction with a core dump.
947 Read symbol table from file @var{file} and use it as the executable
950 @item -core @var{file}
952 @cindex @code{--core}
954 Use file @var{file} as a core dump to examine.
956 @item -pid @var{number}
957 @itemx -p @var{number}
960 Connect to process ID @var{number}, as with the @code{attach} command.
962 @item -command @var{file}
964 @cindex @code{--command}
966 Execute @value{GDBN} commands from file @var{file}. @xref{Command
967 Files,, Command files}.
969 @item -eval-command @var{command}
970 @itemx -ex @var{command}
971 @cindex @code{--eval-command}
973 Execute a single @value{GDBN} command.
975 This option may be used multiple times to call multiple commands. It may
976 also be interleaved with @samp{-command} as required.
979 @value{GDBP} -ex 'target sim' -ex 'load' \
980 -x setbreakpoints -ex 'run' a.out
983 @item -directory @var{directory}
984 @itemx -d @var{directory}
985 @cindex @code{--directory}
987 Add @var{directory} to the path to search for source and script files.
991 @cindex @code{--readnow}
993 Read each symbol file's entire symbol table immediately, rather than
994 the default, which is to read it incrementally as it is needed.
995 This makes startup slower, but makes future operations faster.
1000 @subsection Choosing Modes
1002 You can run @value{GDBN} in various alternative modes---for example, in
1003 batch mode or quiet mode.
1010 Do not execute commands found in any initialization files. Normally,
1011 @value{GDBN} executes the commands in these files after all the command
1012 options and arguments have been processed. @xref{Command Files,,Command
1018 @cindex @code{--quiet}
1019 @cindex @code{--silent}
1021 ``Quiet''. Do not print the introductory and copyright messages. These
1022 messages are also suppressed in batch mode.
1025 @cindex @code{--batch}
1026 Run in batch mode. Exit with status @code{0} after processing all the
1027 command files specified with @samp{-x} (and all commands from
1028 initialization files, if not inhibited with @samp{-n}). Exit with
1029 nonzero status if an error occurs in executing the @value{GDBN} commands
1030 in the command files.
1032 Batch mode may be useful for running @value{GDBN} as a filter, for
1033 example to download and run a program on another computer; in order to
1034 make this more useful, the message
1037 Program exited normally.
1041 (which is ordinarily issued whenever a program running under
1042 @value{GDBN} control terminates) is not issued when running in batch
1046 @cindex @code{--batch-silent}
1047 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1048 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1049 unaffected). This is much quieter than @samp{-silent} and would be useless
1050 for an interactive session.
1052 This is particularly useful when using targets that give @samp{Loading section}
1053 messages, for example.
1055 Note that targets that give their output via @value{GDBN}, as opposed to
1056 writing directly to @code{stdout}, will also be made silent.
1058 @item -return-child-result
1059 @cindex @code{--return-child-result}
1060 The return code from @value{GDBN} will be the return code from the child
1061 process (the process being debugged), with the following exceptions:
1065 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1066 internal error. In this case the exit code is the same as it would have been
1067 without @samp{-return-child-result}.
1069 The user quits with an explicit value. E.g., @samp{quit 1}.
1071 The child process never runs, or is not allowed to terminate, in which case
1072 the exit code will be -1.
1075 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1076 when @value{GDBN} is being used as a remote program loader or simulator
1081 @cindex @code{--nowindows}
1083 ``No windows''. If @value{GDBN} comes with a graphical user interface
1084 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1085 interface. If no GUI is available, this option has no effect.
1089 @cindex @code{--windows}
1091 If @value{GDBN} includes a GUI, then this option requires it to be
1094 @item -cd @var{directory}
1096 Run @value{GDBN} using @var{directory} as its working directory,
1097 instead of the current directory.
1101 @cindex @code{--fullname}
1103 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1104 subprocess. It tells @value{GDBN} to output the full file name and line
1105 number in a standard, recognizable fashion each time a stack frame is
1106 displayed (which includes each time your program stops). This
1107 recognizable format looks like two @samp{\032} characters, followed by
1108 the file name, line number and character position separated by colons,
1109 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1110 @samp{\032} characters as a signal to display the source code for the
1114 @cindex @code{--epoch}
1115 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1116 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1117 routines so as to allow Epoch to display values of expressions in a
1120 @item -annotate @var{level}
1121 @cindex @code{--annotate}
1122 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1123 effect is identical to using @samp{set annotate @var{level}}
1124 (@pxref{Annotations}). The annotation @var{level} controls how much
1125 information @value{GDBN} prints together with its prompt, values of
1126 expressions, source lines, and other types of output. Level 0 is the
1127 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1128 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1129 that control @value{GDBN}, and level 2 has been deprecated.
1131 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1135 @cindex @code{--args}
1136 Change interpretation of command line so that arguments following the
1137 executable file are passed as command line arguments to the inferior.
1138 This option stops option processing.
1140 @item -baud @var{bps}
1142 @cindex @code{--baud}
1144 Set the line speed (baud rate or bits per second) of any serial
1145 interface used by @value{GDBN} for remote debugging.
1147 @item -l @var{timeout}
1149 Set the timeout (in seconds) of any communication used by @value{GDBN}
1150 for remote debugging.
1152 @item -tty @var{device}
1153 @itemx -t @var{device}
1154 @cindex @code{--tty}
1156 Run using @var{device} for your program's standard input and output.
1157 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1159 @c resolve the situation of these eventually
1161 @cindex @code{--tui}
1162 Activate the @dfn{Text User Interface} when starting. The Text User
1163 Interface manages several text windows on the terminal, showing
1164 source, assembly, registers and @value{GDBN} command outputs
1165 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1166 Text User Interface can be enabled by invoking the program
1167 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1168 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1171 @c @cindex @code{--xdb}
1172 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1173 @c For information, see the file @file{xdb_trans.html}, which is usually
1174 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1177 @item -interpreter @var{interp}
1178 @cindex @code{--interpreter}
1179 Use the interpreter @var{interp} for interface with the controlling
1180 program or device. This option is meant to be set by programs which
1181 communicate with @value{GDBN} using it as a back end.
1182 @xref{Interpreters, , Command Interpreters}.
1184 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1185 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1186 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1187 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1188 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1189 @sc{gdb/mi} interfaces are no longer supported.
1192 @cindex @code{--write}
1193 Open the executable and core files for both reading and writing. This
1194 is equivalent to the @samp{set write on} command inside @value{GDBN}
1198 @cindex @code{--statistics}
1199 This option causes @value{GDBN} to print statistics about time and
1200 memory usage after it completes each command and returns to the prompt.
1203 @cindex @code{--version}
1204 This option causes @value{GDBN} to print its version number and
1205 no-warranty blurb, and exit.
1210 @subsection What @value{GDBN} Does During Startup
1211 @cindex @value{GDBN} startup
1213 Here's the description of what @value{GDBN} does during session startup:
1217 Sets up the command interpreter as specified by the command line
1218 (@pxref{Mode Options, interpreter}).
1222 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1223 DOS/Windows systems, the home directory is the one pointed to by the
1224 @code{HOME} environment variable.} and executes all the commands in
1228 Processes command line options and operands.
1231 Reads and executes the commands from init file (if any) in the current
1232 working directory. This is only done if the current directory is
1233 different from your home directory. Thus, you can have more than one
1234 init file, one generic in your home directory, and another, specific
1235 to the program you are debugging, in the directory where you invoke
1239 Reads command files specified by the @samp{-x} option. @xref{Command
1240 Files}, for more details about @value{GDBN} command files.
1243 Reads the command history recorded in the @dfn{history file}.
1244 @xref{Command History}, for more details about the command history and the
1245 files where @value{GDBN} records it.
1248 Init files use the same syntax as @dfn{command files} (@pxref{Command
1249 Files}) and are processed by @value{GDBN} in the same way. The init
1250 file in your home directory can set options (such as @samp{set
1251 complaints}) that affect subsequent processing of command line options
1252 and operands. Init files are not executed if you use the @samp{-nx}
1253 option (@pxref{Mode Options, ,Choosing Modes}).
1255 @cindex init file name
1256 @cindex @file{.gdbinit}
1257 @cindex @file{gdb.ini}
1258 The @value{GDBN} init files are normally called @file{.gdbinit}.
1259 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1260 the limitations of file names imposed by DOS filesystems. The Windows
1261 ports of @value{GDBN} use the standard name, but if they find a
1262 @file{gdb.ini} file, they warn you about that and suggest to rename
1263 the file to the standard name.
1267 @section Quitting @value{GDBN}
1268 @cindex exiting @value{GDBN}
1269 @cindex leaving @value{GDBN}
1272 @kindex quit @r{[}@var{expression}@r{]}
1273 @kindex q @r{(@code{quit})}
1274 @item quit @r{[}@var{expression}@r{]}
1276 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1277 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1278 do not supply @var{expression}, @value{GDBN} will terminate normally;
1279 otherwise it will terminate using the result of @var{expression} as the
1284 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1285 terminates the action of any @value{GDBN} command that is in progress and
1286 returns to @value{GDBN} command level. It is safe to type the interrupt
1287 character at any time because @value{GDBN} does not allow it to take effect
1288 until a time when it is safe.
1290 If you have been using @value{GDBN} to control an attached process or
1291 device, you can release it with the @code{detach} command
1292 (@pxref{Attach, ,Debugging an Already-running Process}).
1294 @node Shell Commands
1295 @section Shell Commands
1297 If you need to execute occasional shell commands during your
1298 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1299 just use the @code{shell} command.
1303 @cindex shell escape
1304 @item shell @var{command string}
1305 Invoke a standard shell to execute @var{command string}.
1306 If it exists, the environment variable @code{SHELL} determines which
1307 shell to run. Otherwise @value{GDBN} uses the default shell
1308 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1311 The utility @code{make} is often needed in development environments.
1312 You do not have to use the @code{shell} command for this purpose in
1317 @cindex calling make
1318 @item make @var{make-args}
1319 Execute the @code{make} program with the specified
1320 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1323 @node Logging Output
1324 @section Logging Output
1325 @cindex logging @value{GDBN} output
1326 @cindex save @value{GDBN} output to a file
1328 You may want to save the output of @value{GDBN} commands to a file.
1329 There are several commands to control @value{GDBN}'s logging.
1333 @item set logging on
1335 @item set logging off
1337 @cindex logging file name
1338 @item set logging file @var{file}
1339 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1340 @item set logging overwrite [on|off]
1341 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1342 you want @code{set logging on} to overwrite the logfile instead.
1343 @item set logging redirect [on|off]
1344 By default, @value{GDBN} output will go to both the terminal and the logfile.
1345 Set @code{redirect} if you want output to go only to the log file.
1346 @kindex show logging
1348 Show the current values of the logging settings.
1352 @chapter @value{GDBN} Commands
1354 You can abbreviate a @value{GDBN} command to the first few letters of the command
1355 name, if that abbreviation is unambiguous; and you can repeat certain
1356 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1357 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1358 show you the alternatives available, if there is more than one possibility).
1361 * Command Syntax:: How to give commands to @value{GDBN}
1362 * Completion:: Command completion
1363 * Help:: How to ask @value{GDBN} for help
1366 @node Command Syntax
1367 @section Command Syntax
1369 A @value{GDBN} command is a single line of input. There is no limit on
1370 how long it can be. It starts with a command name, which is followed by
1371 arguments whose meaning depends on the command name. For example, the
1372 command @code{step} accepts an argument which is the number of times to
1373 step, as in @samp{step 5}. You can also use the @code{step} command
1374 with no arguments. Some commands do not allow any arguments.
1376 @cindex abbreviation
1377 @value{GDBN} command names may always be truncated if that abbreviation is
1378 unambiguous. Other possible command abbreviations are listed in the
1379 documentation for individual commands. In some cases, even ambiguous
1380 abbreviations are allowed; for example, @code{s} is specially defined as
1381 equivalent to @code{step} even though there are other commands whose
1382 names start with @code{s}. You can test abbreviations by using them as
1383 arguments to the @code{help} command.
1385 @cindex repeating commands
1386 @kindex RET @r{(repeat last command)}
1387 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1388 repeat the previous command. Certain commands (for example, @code{run})
1389 will not repeat this way; these are commands whose unintentional
1390 repetition might cause trouble and which you are unlikely to want to
1391 repeat. User-defined commands can disable this feature; see
1392 @ref{Define, dont-repeat}.
1394 The @code{list} and @code{x} commands, when you repeat them with
1395 @key{RET}, construct new arguments rather than repeating
1396 exactly as typed. This permits easy scanning of source or memory.
1398 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1399 output, in a way similar to the common utility @code{more}
1400 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1401 @key{RET} too many in this situation, @value{GDBN} disables command
1402 repetition after any command that generates this sort of display.
1404 @kindex # @r{(a comment)}
1406 Any text from a @kbd{#} to the end of the line is a comment; it does
1407 nothing. This is useful mainly in command files (@pxref{Command
1408 Files,,Command Files}).
1410 @cindex repeating command sequences
1411 @kindex Ctrl-o @r{(operate-and-get-next)}
1412 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1413 commands. This command accepts the current line, like @key{RET}, and
1414 then fetches the next line relative to the current line from the history
1418 @section Command Completion
1421 @cindex word completion
1422 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1423 only one possibility; it can also show you what the valid possibilities
1424 are for the next word in a command, at any time. This works for @value{GDBN}
1425 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1427 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1428 of a word. If there is only one possibility, @value{GDBN} fills in the
1429 word, and waits for you to finish the command (or press @key{RET} to
1430 enter it). For example, if you type
1432 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1433 @c complete accuracy in these examples; space introduced for clarity.
1434 @c If texinfo enhancements make it unnecessary, it would be nice to
1435 @c replace " @key" by "@key" in the following...
1437 (@value{GDBP}) info bre @key{TAB}
1441 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1442 the only @code{info} subcommand beginning with @samp{bre}:
1445 (@value{GDBP}) info breakpoints
1449 You can either press @key{RET} at this point, to run the @code{info
1450 breakpoints} command, or backspace and enter something else, if
1451 @samp{breakpoints} does not look like the command you expected. (If you
1452 were sure you wanted @code{info breakpoints} in the first place, you
1453 might as well just type @key{RET} immediately after @samp{info bre},
1454 to exploit command abbreviations rather than command completion).
1456 If there is more than one possibility for the next word when you press
1457 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1458 characters and try again, or just press @key{TAB} a second time;
1459 @value{GDBN} displays all the possible completions for that word. For
1460 example, you might want to set a breakpoint on a subroutine whose name
1461 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1462 just sounds the bell. Typing @key{TAB} again displays all the
1463 function names in your program that begin with those characters, for
1467 (@value{GDBP}) b make_ @key{TAB}
1468 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1469 make_a_section_from_file make_environ
1470 make_abs_section make_function_type
1471 make_blockvector make_pointer_type
1472 make_cleanup make_reference_type
1473 make_command make_symbol_completion_list
1474 (@value{GDBP}) b make_
1478 After displaying the available possibilities, @value{GDBN} copies your
1479 partial input (@samp{b make_} in the example) so you can finish the
1482 If you just want to see the list of alternatives in the first place, you
1483 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1484 means @kbd{@key{META} ?}. You can type this either by holding down a
1485 key designated as the @key{META} shift on your keyboard (if there is
1486 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1488 @cindex quotes in commands
1489 @cindex completion of quoted strings
1490 Sometimes the string you need, while logically a ``word'', may contain
1491 parentheses or other characters that @value{GDBN} normally excludes from
1492 its notion of a word. To permit word completion to work in this
1493 situation, you may enclose words in @code{'} (single quote marks) in
1494 @value{GDBN} commands.
1496 The most likely situation where you might need this is in typing the
1497 name of a C@t{++} function. This is because C@t{++} allows function
1498 overloading (multiple definitions of the same function, distinguished
1499 by argument type). For example, when you want to set a breakpoint you
1500 may need to distinguish whether you mean the version of @code{name}
1501 that takes an @code{int} parameter, @code{name(int)}, or the version
1502 that takes a @code{float} parameter, @code{name(float)}. To use the
1503 word-completion facilities in this situation, type a single quote
1504 @code{'} at the beginning of the function name. This alerts
1505 @value{GDBN} that it may need to consider more information than usual
1506 when you press @key{TAB} or @kbd{M-?} to request word completion:
1509 (@value{GDBP}) b 'bubble( @kbd{M-?}
1510 bubble(double,double) bubble(int,int)
1511 (@value{GDBP}) b 'bubble(
1514 In some cases, @value{GDBN} can tell that completing a name requires using
1515 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1516 completing as much as it can) if you do not type the quote in the first
1520 (@value{GDBP}) b bub @key{TAB}
1521 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1522 (@value{GDBP}) b 'bubble(
1526 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1527 you have not yet started typing the argument list when you ask for
1528 completion on an overloaded symbol.
1530 For more information about overloaded functions, see @ref{C Plus Plus
1531 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1532 overload-resolution off} to disable overload resolution;
1533 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1535 @cindex completion of structure field names
1536 @cindex structure field name completion
1537 @cindex completion of union field names
1538 @cindex union field name completion
1539 When completing in an expression which looks up a field in a
1540 structure, @value{GDBN} also tries@footnote{The completer can be
1541 confused by certain kinds of invalid expressions. Also, it only
1542 examines the static type of the expression, not the dynamic type.} to
1543 limit completions to the field names available in the type of the
1547 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1548 magic to_delete to_fputs to_put to_rewind
1549 to_data to_flush to_isatty to_read to_write
1553 This is because the @code{gdb_stdout} is a variable of the type
1554 @code{struct ui_file} that is defined in @value{GDBN} sources as
1561 ui_file_flush_ftype *to_flush;
1562 ui_file_write_ftype *to_write;
1563 ui_file_fputs_ftype *to_fputs;
1564 ui_file_read_ftype *to_read;
1565 ui_file_delete_ftype *to_delete;
1566 ui_file_isatty_ftype *to_isatty;
1567 ui_file_rewind_ftype *to_rewind;
1568 ui_file_put_ftype *to_put;
1575 @section Getting Help
1576 @cindex online documentation
1579 You can always ask @value{GDBN} itself for information on its commands,
1580 using the command @code{help}.
1583 @kindex h @r{(@code{help})}
1586 You can use @code{help} (abbreviated @code{h}) with no arguments to
1587 display a short list of named classes of commands:
1591 List of classes of commands:
1593 aliases -- Aliases of other commands
1594 breakpoints -- Making program stop at certain points
1595 data -- Examining data
1596 files -- Specifying and examining files
1597 internals -- Maintenance commands
1598 obscure -- Obscure features
1599 running -- Running the program
1600 stack -- Examining the stack
1601 status -- Status inquiries
1602 support -- Support facilities
1603 tracepoints -- Tracing of program execution without
1604 stopping the program
1605 user-defined -- User-defined commands
1607 Type "help" followed by a class name for a list of
1608 commands in that class.
1609 Type "help" followed by command name for full
1611 Command name abbreviations are allowed if unambiguous.
1614 @c the above line break eliminates huge line overfull...
1616 @item help @var{class}
1617 Using one of the general help classes as an argument, you can get a
1618 list of the individual commands in that class. For example, here is the
1619 help display for the class @code{status}:
1622 (@value{GDBP}) help status
1627 @c Line break in "show" line falsifies real output, but needed
1628 @c to fit in smallbook page size.
1629 info -- Generic command for showing things
1630 about the program being debugged
1631 show -- Generic command for showing things
1634 Type "help" followed by command name for full
1636 Command name abbreviations are allowed if unambiguous.
1640 @item help @var{command}
1641 With a command name as @code{help} argument, @value{GDBN} displays a
1642 short paragraph on how to use that command.
1645 @item apropos @var{args}
1646 The @code{apropos} command searches through all of the @value{GDBN}
1647 commands, and their documentation, for the regular expression specified in
1648 @var{args}. It prints out all matches found. For example:
1659 set symbol-reloading -- Set dynamic symbol table reloading
1660 multiple times in one run
1661 show symbol-reloading -- Show dynamic symbol table reloading
1662 multiple times in one run
1667 @item complete @var{args}
1668 The @code{complete @var{args}} command lists all the possible completions
1669 for the beginning of a command. Use @var{args} to specify the beginning of the
1670 command you want completed. For example:
1676 @noindent results in:
1687 @noindent This is intended for use by @sc{gnu} Emacs.
1690 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1691 and @code{show} to inquire about the state of your program, or the state
1692 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1693 manual introduces each of them in the appropriate context. The listings
1694 under @code{info} and under @code{show} in the Index point to
1695 all the sub-commands. @xref{Index}.
1700 @kindex i @r{(@code{info})}
1702 This command (abbreviated @code{i}) is for describing the state of your
1703 program. For example, you can show the arguments passed to a function
1704 with @code{info args}, list the registers currently in use with @code{info
1705 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1706 You can get a complete list of the @code{info} sub-commands with
1707 @w{@code{help info}}.
1711 You can assign the result of an expression to an environment variable with
1712 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1713 @code{set prompt $}.
1717 In contrast to @code{info}, @code{show} is for describing the state of
1718 @value{GDBN} itself.
1719 You can change most of the things you can @code{show}, by using the
1720 related command @code{set}; for example, you can control what number
1721 system is used for displays with @code{set radix}, or simply inquire
1722 which is currently in use with @code{show radix}.
1725 To display all the settable parameters and their current
1726 values, you can use @code{show} with no arguments; you may also use
1727 @code{info set}. Both commands produce the same display.
1728 @c FIXME: "info set" violates the rule that "info" is for state of
1729 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1730 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1734 Here are three miscellaneous @code{show} subcommands, all of which are
1735 exceptional in lacking corresponding @code{set} commands:
1738 @kindex show version
1739 @cindex @value{GDBN} version number
1741 Show what version of @value{GDBN} is running. You should include this
1742 information in @value{GDBN} bug-reports. If multiple versions of
1743 @value{GDBN} are in use at your site, you may need to determine which
1744 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1745 commands are introduced, and old ones may wither away. Also, many
1746 system vendors ship variant versions of @value{GDBN}, and there are
1747 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1748 The version number is the same as the one announced when you start
1751 @kindex show copying
1752 @kindex info copying
1753 @cindex display @value{GDBN} copyright
1756 Display information about permission for copying @value{GDBN}.
1758 @kindex show warranty
1759 @kindex info warranty
1761 @itemx info warranty
1762 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1763 if your version of @value{GDBN} comes with one.
1768 @chapter Running Programs Under @value{GDBN}
1770 When you run a program under @value{GDBN}, you must first generate
1771 debugging information when you compile it.
1773 You may start @value{GDBN} with its arguments, if any, in an environment
1774 of your choice. If you are doing native debugging, you may redirect
1775 your program's input and output, debug an already running process, or
1776 kill a child process.
1779 * Compilation:: Compiling for debugging
1780 * Starting:: Starting your program
1781 * Arguments:: Your program's arguments
1782 * Environment:: Your program's environment
1784 * Working Directory:: Your program's working directory
1785 * Input/Output:: Your program's input and output
1786 * Attach:: Debugging an already-running process
1787 * Kill Process:: Killing the child process
1789 * Inferiors:: Debugging multiple inferiors
1790 * Threads:: Debugging programs with multiple threads
1791 * Processes:: Debugging programs with multiple processes
1792 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1796 @section Compiling for Debugging
1798 In order to debug a program effectively, you need to generate
1799 debugging information when you compile it. This debugging information
1800 is stored in the object file; it describes the data type of each
1801 variable or function and the correspondence between source line numbers
1802 and addresses in the executable code.
1804 To request debugging information, specify the @samp{-g} option when you run
1807 Programs that are to be shipped to your customers are compiled with
1808 optimizations, using the @samp{-O} compiler option. However, many
1809 compilers are unable to handle the @samp{-g} and @samp{-O} options
1810 together. Using those compilers, you cannot generate optimized
1811 executables containing debugging information.
1813 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1814 without @samp{-O}, making it possible to debug optimized code. We
1815 recommend that you @emph{always} use @samp{-g} whenever you compile a
1816 program. You may think your program is correct, but there is no sense
1817 in pushing your luck.
1819 @cindex optimized code, debugging
1820 @cindex debugging optimized code
1821 When you debug a program compiled with @samp{-g -O}, remember that the
1822 optimizer is rearranging your code; the debugger shows you what is
1823 really there. Do not be too surprised when the execution path does not
1824 exactly match your source file! An extreme example: if you define a
1825 variable, but never use it, @value{GDBN} never sees that
1826 variable---because the compiler optimizes it out of existence.
1828 Some things do not work as well with @samp{-g -O} as with just
1829 @samp{-g}, particularly on machines with instruction scheduling. If in
1830 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1831 please report it to us as a bug (including a test case!).
1832 @xref{Variables}, for more information about debugging optimized code.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2360 @section Debugging Multiple Inferiors
2362 Some @value{GDBN} targets are able to run multiple processes created
2363 from a single executable. This can happen, for instance, with an
2364 embedded system reporting back several processes via the remote
2368 @value{GDBN} represents the state of each program execution with an
2369 object called an @dfn{inferior}. An inferior typically corresponds to
2370 a process, but is more general and applies also to targets that do not
2371 have processes. Inferiors may be created before a process runs, and
2372 may (in future) be retained after a process exits. Each run of an
2373 executable creates a new inferior, as does each attachment to an
2374 existing process. Inferiors have unique identifiers that are
2375 different from process ids, and may optionally be named as well.
2376 Usually each inferior will also have its own distinct address space,
2377 although some embedded targets may have several inferiors running in
2378 different parts of a single space.
2380 Each inferior may in turn have multiple threads running in it.
2382 To find out what inferiors exist at any moment, use @code{info inferiors}:
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @kindex set print inferior-events
2390 @cindex print messages on inferior start and exit
2391 @item set print inferior-events
2392 @itemx set print inferior-events on
2393 @itemx set print inferior-events off
2394 The @code{set print inferior-events} command allows you to enable or
2395 disable printing of messages when @value{GDBN} notices that new
2396 inferiors have started or that inferiors have exited or have been
2397 detached. By default, these messages will not be printed.
2399 @kindex show print inferior-events
2400 @item show print inferior-events
2401 Show whether messages will be printed when @value{GDBN} detects that
2402 inferiors have started, exited or have been detached.
2406 @section Debugging Programs with Multiple Threads
2408 @cindex threads of execution
2409 @cindex multiple threads
2410 @cindex switching threads
2411 In some operating systems, such as HP-UX and Solaris, a single program
2412 may have more than one @dfn{thread} of execution. The precise semantics
2413 of threads differ from one operating system to another, but in general
2414 the threads of a single program are akin to multiple processes---except
2415 that they share one address space (that is, they can all examine and
2416 modify the same variables). On the other hand, each thread has its own
2417 registers and execution stack, and perhaps private memory.
2419 @value{GDBN} provides these facilities for debugging multi-thread
2423 @item automatic notification of new threads
2424 @item @samp{thread @var{threadno}}, a command to switch among threads
2425 @item @samp{info threads}, a command to inquire about existing threads
2426 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2427 a command to apply a command to a list of threads
2428 @item thread-specific breakpoints
2429 @item @samp{set print thread-events}, which controls printing of
2430 messages on thread start and exit.
2434 @emph{Warning:} These facilities are not yet available on every
2435 @value{GDBN} configuration where the operating system supports threads.
2436 If your @value{GDBN} does not support threads, these commands have no
2437 effect. For example, a system without thread support shows no output
2438 from @samp{info threads}, and always rejects the @code{thread} command,
2442 (@value{GDBP}) info threads
2443 (@value{GDBP}) thread 1
2444 Thread ID 1 not known. Use the "info threads" command to
2445 see the IDs of currently known threads.
2447 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2448 @c doesn't support threads"?
2451 @cindex focus of debugging
2452 @cindex current thread
2453 The @value{GDBN} thread debugging facility allows you to observe all
2454 threads while your program runs---but whenever @value{GDBN} takes
2455 control, one thread in particular is always the focus of debugging.
2456 This thread is called the @dfn{current thread}. Debugging commands show
2457 program information from the perspective of the current thread.
2459 @cindex @code{New} @var{systag} message
2460 @cindex thread identifier (system)
2461 @c FIXME-implementors!! It would be more helpful if the [New...] message
2462 @c included GDB's numeric thread handle, so you could just go to that
2463 @c thread without first checking `info threads'.
2464 Whenever @value{GDBN} detects a new thread in your program, it displays
2465 the target system's identification for the thread with a message in the
2466 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2467 whose form varies depending on the particular system. For example, on
2468 @sc{gnu}/Linux, you might see
2471 [New Thread 46912507313328 (LWP 25582)]
2475 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2476 the @var{systag} is simply something like @samp{process 368}, with no
2479 @c FIXME!! (1) Does the [New...] message appear even for the very first
2480 @c thread of a program, or does it only appear for the
2481 @c second---i.e.@: when it becomes obvious we have a multithread
2483 @c (2) *Is* there necessarily a first thread always? Or do some
2484 @c multithread systems permit starting a program with multiple
2485 @c threads ab initio?
2487 @cindex thread number
2488 @cindex thread identifier (GDB)
2489 For debugging purposes, @value{GDBN} associates its own thread
2490 number---always a single integer---with each thread in your program.
2493 @kindex info threads
2495 Display a summary of all threads currently in your
2496 program. @value{GDBN} displays for each thread (in this order):
2500 the thread number assigned by @value{GDBN}
2503 the target system's thread identifier (@var{systag})
2506 the current stack frame summary for that thread
2510 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2511 indicates the current thread.
2515 @c end table here to get a little more width for example
2518 (@value{GDBP}) info threads
2519 3 process 35 thread 27 0x34e5 in sigpause ()
2520 2 process 35 thread 23 0x34e5 in sigpause ()
2521 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2527 @cindex debugging multithreaded programs (on HP-UX)
2528 @cindex thread identifier (GDB), on HP-UX
2529 For debugging purposes, @value{GDBN} associates its own thread
2530 number---a small integer assigned in thread-creation order---with each
2531 thread in your program.
2533 @cindex @code{New} @var{systag} message, on HP-UX
2534 @cindex thread identifier (system), on HP-UX
2535 @c FIXME-implementors!! It would be more helpful if the [New...] message
2536 @c included GDB's numeric thread handle, so you could just go to that
2537 @c thread without first checking `info threads'.
2538 Whenever @value{GDBN} detects a new thread in your program, it displays
2539 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2540 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2541 whose form varies depending on the particular system. For example, on
2545 [New thread 2 (system thread 26594)]
2549 when @value{GDBN} notices a new thread.
2552 @kindex info threads (HP-UX)
2554 Display a summary of all threads currently in your
2555 program. @value{GDBN} displays for each thread (in this order):
2558 @item the thread number assigned by @value{GDBN}
2560 @item the target system's thread identifier (@var{systag})
2562 @item the current stack frame summary for that thread
2566 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2567 indicates the current thread.
2571 @c end table here to get a little more width for example
2574 (@value{GDBP}) info threads
2575 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2577 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2578 from /usr/lib/libc.2
2579 1 system thread 27905 0x7b003498 in _brk () \@*
2580 from /usr/lib/libc.2
2583 On Solaris, you can display more information about user threads with a
2584 Solaris-specific command:
2587 @item maint info sol-threads
2588 @kindex maint info sol-threads
2589 @cindex thread info (Solaris)
2590 Display info on Solaris user threads.
2594 @kindex thread @var{threadno}
2595 @item thread @var{threadno}
2596 Make thread number @var{threadno} the current thread. The command
2597 argument @var{threadno} is the internal @value{GDBN} thread number, as
2598 shown in the first field of the @samp{info threads} display.
2599 @value{GDBN} responds by displaying the system identifier of the thread
2600 you selected, and its current stack frame summary:
2603 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2604 (@value{GDBP}) thread 2
2605 [Switching to process 35 thread 23]
2606 0x34e5 in sigpause ()
2610 As with the @samp{[New @dots{}]} message, the form of the text after
2611 @samp{Switching to} depends on your system's conventions for identifying
2614 @kindex thread apply
2615 @cindex apply command to several threads
2616 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2617 The @code{thread apply} command allows you to apply the named
2618 @var{command} to one or more threads. Specify the numbers of the
2619 threads that you want affected with the command argument
2620 @var{threadno}. It can be a single thread number, one of the numbers
2621 shown in the first field of the @samp{info threads} display; or it
2622 could be a range of thread numbers, as in @code{2-4}. To apply a
2623 command to all threads, type @kbd{thread apply all @var{command}}.
2625 @kindex set print thread-events
2626 @cindex print messages on thread start and exit
2627 @item set print thread-events
2628 @itemx set print thread-events on
2629 @itemx set print thread-events off
2630 The @code{set print thread-events} command allows you to enable or
2631 disable printing of messages when @value{GDBN} notices that new threads have
2632 started or that threads have exited. By default, these messages will
2633 be printed if detection of these events is supported by the target.
2634 Note that these messages cannot be disabled on all targets.
2636 @kindex show print thread-events
2637 @item show print thread-events
2638 Show whether messages will be printed when @value{GDBN} detects that threads
2639 have started and exited.
2642 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2643 more information about how @value{GDBN} behaves when you stop and start
2644 programs with multiple threads.
2646 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2647 watchpoints in programs with multiple threads.
2650 @section Debugging Programs with Multiple Processes
2652 @cindex fork, debugging programs which call
2653 @cindex multiple processes
2654 @cindex processes, multiple
2655 On most systems, @value{GDBN} has no special support for debugging
2656 programs which create additional processes using the @code{fork}
2657 function. When a program forks, @value{GDBN} will continue to debug the
2658 parent process and the child process will run unimpeded. If you have
2659 set a breakpoint in any code which the child then executes, the child
2660 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2661 will cause it to terminate.
2663 However, if you want to debug the child process there is a workaround
2664 which isn't too painful. Put a call to @code{sleep} in the code which
2665 the child process executes after the fork. It may be useful to sleep
2666 only if a certain environment variable is set, or a certain file exists,
2667 so that the delay need not occur when you don't want to run @value{GDBN}
2668 on the child. While the child is sleeping, use the @code{ps} program to
2669 get its process ID. Then tell @value{GDBN} (a new invocation of
2670 @value{GDBN} if you are also debugging the parent process) to attach to
2671 the child process (@pxref{Attach}). From that point on you can debug
2672 the child process just like any other process which you attached to.
2674 On some systems, @value{GDBN} provides support for debugging programs that
2675 create additional processes using the @code{fork} or @code{vfork} functions.
2676 Currently, the only platforms with this feature are HP-UX (11.x and later
2677 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2679 By default, when a program forks, @value{GDBN} will continue to debug
2680 the parent process and the child process will run unimpeded.
2682 If you want to follow the child process instead of the parent process,
2683 use the command @w{@code{set follow-fork-mode}}.
2686 @kindex set follow-fork-mode
2687 @item set follow-fork-mode @var{mode}
2688 Set the debugger response to a program call of @code{fork} or
2689 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2690 process. The @var{mode} argument can be:
2694 The original process is debugged after a fork. The child process runs
2695 unimpeded. This is the default.
2698 The new process is debugged after a fork. The parent process runs
2703 @kindex show follow-fork-mode
2704 @item show follow-fork-mode
2705 Display the current debugger response to a @code{fork} or @code{vfork} call.
2708 @cindex debugging multiple processes
2709 On Linux, if you want to debug both the parent and child processes, use the
2710 command @w{@code{set detach-on-fork}}.
2713 @kindex set detach-on-fork
2714 @item set detach-on-fork @var{mode}
2715 Tells gdb whether to detach one of the processes after a fork, or
2716 retain debugger control over them both.
2720 The child process (or parent process, depending on the value of
2721 @code{follow-fork-mode}) will be detached and allowed to run
2722 independently. This is the default.
2725 Both processes will be held under the control of @value{GDBN}.
2726 One process (child or parent, depending on the value of
2727 @code{follow-fork-mode}) is debugged as usual, while the other
2732 @kindex show detach-on-fork
2733 @item show detach-on-fork
2734 Show whether detach-on-fork mode is on/off.
2737 If you choose to set @samp{detach-on-fork} mode off, then
2738 @value{GDBN} will retain control of all forked processes (including
2739 nested forks). You can list the forked processes under the control of
2740 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2741 from one fork to another by using the @w{@code{fork}} command.
2746 Print a list of all forked processes under the control of @value{GDBN}.
2747 The listing will include a fork id, a process id, and the current
2748 position (program counter) of the process.
2750 @kindex fork @var{fork-id}
2751 @item fork @var{fork-id}
2752 Make fork number @var{fork-id} the current process. The argument
2753 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2754 as shown in the first field of the @samp{info forks} display.
2756 @kindex process @var{process-id}
2757 @item process @var{process-id}
2758 Make process number @var{process-id} the current process. The
2759 argument @var{process-id} must be one that is listed in the output of
2764 To quit debugging one of the forked processes, you can either detach
2765 from it by using the @w{@code{detach fork}} command (allowing it to
2766 run independently), or delete (and kill) it using the
2767 @w{@code{delete fork}} command.
2770 @kindex detach fork @var{fork-id}
2771 @item detach fork @var{fork-id}
2772 Detach from the process identified by @value{GDBN} fork number
2773 @var{fork-id}, and remove it from the fork list. The process will be
2774 allowed to run independently.
2776 @kindex delete fork @var{fork-id}
2777 @item delete fork @var{fork-id}
2778 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2779 and remove it from the fork list.
2783 If you ask to debug a child process and a @code{vfork} is followed by an
2784 @code{exec}, @value{GDBN} executes the new target up to the first
2785 breakpoint in the new target. If you have a breakpoint set on
2786 @code{main} in your original program, the breakpoint will also be set on
2787 the child process's @code{main}.
2789 When a child process is spawned by @code{vfork}, you cannot debug the
2790 child or parent until an @code{exec} call completes.
2792 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2793 call executes, the new target restarts. To restart the parent process,
2794 use the @code{file} command with the parent executable name as its
2797 You can use the @code{catch} command to make @value{GDBN} stop whenever
2798 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2799 Catchpoints, ,Setting Catchpoints}.
2801 @node Checkpoint/Restart
2802 @section Setting a @emph{Bookmark} to Return to Later
2807 @cindex snapshot of a process
2808 @cindex rewind program state
2810 On certain operating systems@footnote{Currently, only
2811 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2812 program's state, called a @dfn{checkpoint}, and come back to it
2815 Returning to a checkpoint effectively undoes everything that has
2816 happened in the program since the @code{checkpoint} was saved. This
2817 includes changes in memory, registers, and even (within some limits)
2818 system state. Effectively, it is like going back in time to the
2819 moment when the checkpoint was saved.
2821 Thus, if you're stepping thru a program and you think you're
2822 getting close to the point where things go wrong, you can save
2823 a checkpoint. Then, if you accidentally go too far and miss
2824 the critical statement, instead of having to restart your program
2825 from the beginning, you can just go back to the checkpoint and
2826 start again from there.
2828 This can be especially useful if it takes a lot of time or
2829 steps to reach the point where you think the bug occurs.
2831 To use the @code{checkpoint}/@code{restart} method of debugging:
2836 Save a snapshot of the debugged program's current execution state.
2837 The @code{checkpoint} command takes no arguments, but each checkpoint
2838 is assigned a small integer id, similar to a breakpoint id.
2840 @kindex info checkpoints
2841 @item info checkpoints
2842 List the checkpoints that have been saved in the current debugging
2843 session. For each checkpoint, the following information will be
2850 @item Source line, or label
2853 @kindex restart @var{checkpoint-id}
2854 @item restart @var{checkpoint-id}
2855 Restore the program state that was saved as checkpoint number
2856 @var{checkpoint-id}. All program variables, registers, stack frames
2857 etc.@: will be returned to the values that they had when the checkpoint
2858 was saved. In essence, gdb will ``wind back the clock'' to the point
2859 in time when the checkpoint was saved.
2861 Note that breakpoints, @value{GDBN} variables, command history etc.
2862 are not affected by restoring a checkpoint. In general, a checkpoint
2863 only restores things that reside in the program being debugged, not in
2866 @kindex delete checkpoint @var{checkpoint-id}
2867 @item delete checkpoint @var{checkpoint-id}
2868 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2872 Returning to a previously saved checkpoint will restore the user state
2873 of the program being debugged, plus a significant subset of the system
2874 (OS) state, including file pointers. It won't ``un-write'' data from
2875 a file, but it will rewind the file pointer to the previous location,
2876 so that the previously written data can be overwritten. For files
2877 opened in read mode, the pointer will also be restored so that the
2878 previously read data can be read again.
2880 Of course, characters that have been sent to a printer (or other
2881 external device) cannot be ``snatched back'', and characters received
2882 from eg.@: a serial device can be removed from internal program buffers,
2883 but they cannot be ``pushed back'' into the serial pipeline, ready to
2884 be received again. Similarly, the actual contents of files that have
2885 been changed cannot be restored (at this time).
2887 However, within those constraints, you actually can ``rewind'' your
2888 program to a previously saved point in time, and begin debugging it
2889 again --- and you can change the course of events so as to debug a
2890 different execution path this time.
2892 @cindex checkpoints and process id
2893 Finally, there is one bit of internal program state that will be
2894 different when you return to a checkpoint --- the program's process
2895 id. Each checkpoint will have a unique process id (or @var{pid}),
2896 and each will be different from the program's original @var{pid}.
2897 If your program has saved a local copy of its process id, this could
2898 potentially pose a problem.
2900 @subsection A Non-obvious Benefit of Using Checkpoints
2902 On some systems such as @sc{gnu}/Linux, address space randomization
2903 is performed on new processes for security reasons. This makes it
2904 difficult or impossible to set a breakpoint, or watchpoint, on an
2905 absolute address if you have to restart the program, since the
2906 absolute location of a symbol will change from one execution to the
2909 A checkpoint, however, is an @emph{identical} copy of a process.
2910 Therefore if you create a checkpoint at (eg.@:) the start of main,
2911 and simply return to that checkpoint instead of restarting the
2912 process, you can avoid the effects of address randomization and
2913 your symbols will all stay in the same place.
2916 @chapter Stopping and Continuing
2918 The principal purposes of using a debugger are so that you can stop your
2919 program before it terminates; or so that, if your program runs into
2920 trouble, you can investigate and find out why.
2922 Inside @value{GDBN}, your program may stop for any of several reasons,
2923 such as a signal, a breakpoint, or reaching a new line after a
2924 @value{GDBN} command such as @code{step}. You may then examine and
2925 change variables, set new breakpoints or remove old ones, and then
2926 continue execution. Usually, the messages shown by @value{GDBN} provide
2927 ample explanation of the status of your program---but you can also
2928 explicitly request this information at any time.
2931 @kindex info program
2933 Display information about the status of your program: whether it is
2934 running or not, what process it is, and why it stopped.
2938 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2939 * Continuing and Stepping:: Resuming execution
2941 * Thread Stops:: Stopping and starting multi-thread programs
2945 @section Breakpoints, Watchpoints, and Catchpoints
2948 A @dfn{breakpoint} makes your program stop whenever a certain point in
2949 the program is reached. For each breakpoint, you can add conditions to
2950 control in finer detail whether your program stops. You can set
2951 breakpoints with the @code{break} command and its variants (@pxref{Set
2952 Breaks, ,Setting Breakpoints}), to specify the place where your program
2953 should stop by line number, function name or exact address in the
2956 On some systems, you can set breakpoints in shared libraries before
2957 the executable is run. There is a minor limitation on HP-UX systems:
2958 you must wait until the executable is run in order to set breakpoints
2959 in shared library routines that are not called directly by the program
2960 (for example, routines that are arguments in a @code{pthread_create}
2964 @cindex data breakpoints
2965 @cindex memory tracing
2966 @cindex breakpoint on memory address
2967 @cindex breakpoint on variable modification
2968 A @dfn{watchpoint} is a special breakpoint that stops your program
2969 when the value of an expression changes. The expression may be a value
2970 of a variable, or it could involve values of one or more variables
2971 combined by operators, such as @samp{a + b}. This is sometimes called
2972 @dfn{data breakpoints}. You must use a different command to set
2973 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2974 from that, you can manage a watchpoint like any other breakpoint: you
2975 enable, disable, and delete both breakpoints and watchpoints using the
2978 You can arrange to have values from your program displayed automatically
2979 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2983 @cindex breakpoint on events
2984 A @dfn{catchpoint} is another special breakpoint that stops your program
2985 when a certain kind of event occurs, such as the throwing of a C@t{++}
2986 exception or the loading of a library. As with watchpoints, you use a
2987 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2988 Catchpoints}), but aside from that, you can manage a catchpoint like any
2989 other breakpoint. (To stop when your program receives a signal, use the
2990 @code{handle} command; see @ref{Signals, ,Signals}.)
2992 @cindex breakpoint numbers
2993 @cindex numbers for breakpoints
2994 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2995 catchpoint when you create it; these numbers are successive integers
2996 starting with one. In many of the commands for controlling various
2997 features of breakpoints you use the breakpoint number to say which
2998 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2999 @dfn{disabled}; if disabled, it has no effect on your program until you
3002 @cindex breakpoint ranges
3003 @cindex ranges of breakpoints
3004 Some @value{GDBN} commands accept a range of breakpoints on which to
3005 operate. A breakpoint range is either a single breakpoint number, like
3006 @samp{5}, or two such numbers, in increasing order, separated by a
3007 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3008 all breakpoints in that range are operated on.
3011 * Set Breaks:: Setting breakpoints
3012 * Set Watchpoints:: Setting watchpoints
3013 * Set Catchpoints:: Setting catchpoints
3014 * Delete Breaks:: Deleting breakpoints
3015 * Disabling:: Disabling breakpoints
3016 * Conditions:: Break conditions
3017 * Break Commands:: Breakpoint command lists
3018 * Error in Breakpoints:: ``Cannot insert breakpoints''
3019 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3023 @subsection Setting Breakpoints
3025 @c FIXME LMB what does GDB do if no code on line of breakpt?
3026 @c consider in particular declaration with/without initialization.
3028 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3031 @kindex b @r{(@code{break})}
3032 @vindex $bpnum@r{, convenience variable}
3033 @cindex latest breakpoint
3034 Breakpoints are set with the @code{break} command (abbreviated
3035 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3036 number of the breakpoint you've set most recently; see @ref{Convenience
3037 Vars,, Convenience Variables}, for a discussion of what you can do with
3038 convenience variables.
3041 @item break @var{location}
3042 Set a breakpoint at the given @var{location}, which can specify a
3043 function name, a line number, or an address of an instruction.
3044 (@xref{Specify Location}, for a list of all the possible ways to
3045 specify a @var{location}.) The breakpoint will stop your program just
3046 before it executes any of the code in the specified @var{location}.
3048 When using source languages that permit overloading of symbols, such as
3049 C@t{++}, a function name may refer to more than one possible place to break.
3050 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3054 When called without any arguments, @code{break} sets a breakpoint at
3055 the next instruction to be executed in the selected stack frame
3056 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3057 innermost, this makes your program stop as soon as control
3058 returns to that frame. This is similar to the effect of a
3059 @code{finish} command in the frame inside the selected frame---except
3060 that @code{finish} does not leave an active breakpoint. If you use
3061 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3062 the next time it reaches the current location; this may be useful
3065 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3066 least one instruction has been executed. If it did not do this, you
3067 would be unable to proceed past a breakpoint without first disabling the
3068 breakpoint. This rule applies whether or not the breakpoint already
3069 existed when your program stopped.
3071 @item break @dots{} if @var{cond}
3072 Set a breakpoint with condition @var{cond}; evaluate the expression
3073 @var{cond} each time the breakpoint is reached, and stop only if the
3074 value is nonzero---that is, if @var{cond} evaluates as true.
3075 @samp{@dots{}} stands for one of the possible arguments described
3076 above (or no argument) specifying where to break. @xref{Conditions,
3077 ,Break Conditions}, for more information on breakpoint conditions.
3080 @item tbreak @var{args}
3081 Set a breakpoint enabled only for one stop. @var{args} are the
3082 same as for the @code{break} command, and the breakpoint is set in the same
3083 way, but the breakpoint is automatically deleted after the first time your
3084 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3087 @cindex hardware breakpoints
3088 @item hbreak @var{args}
3089 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3090 @code{break} command and the breakpoint is set in the same way, but the
3091 breakpoint requires hardware support and some target hardware may not
3092 have this support. The main purpose of this is EPROM/ROM code
3093 debugging, so you can set a breakpoint at an instruction without
3094 changing the instruction. This can be used with the new trap-generation
3095 provided by SPARClite DSU and most x86-based targets. These targets
3096 will generate traps when a program accesses some data or instruction
3097 address that is assigned to the debug registers. However the hardware
3098 breakpoint registers can take a limited number of breakpoints. For
3099 example, on the DSU, only two data breakpoints can be set at a time, and
3100 @value{GDBN} will reject this command if more than two are used. Delete
3101 or disable unused hardware breakpoints before setting new ones
3102 (@pxref{Disabling, ,Disabling Breakpoints}).
3103 @xref{Conditions, ,Break Conditions}.
3104 For remote targets, you can restrict the number of hardware
3105 breakpoints @value{GDBN} will use, see @ref{set remote
3106 hardware-breakpoint-limit}.
3109 @item thbreak @var{args}
3110 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3111 are the same as for the @code{hbreak} command and the breakpoint is set in
3112 the same way. However, like the @code{tbreak} command,
3113 the breakpoint is automatically deleted after the
3114 first time your program stops there. Also, like the @code{hbreak}
3115 command, the breakpoint requires hardware support and some target hardware
3116 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3117 See also @ref{Conditions, ,Break Conditions}.
3120 @cindex regular expression
3121 @cindex breakpoints in functions matching a regexp
3122 @cindex set breakpoints in many functions
3123 @item rbreak @var{regex}
3124 Set breakpoints on all functions matching the regular expression
3125 @var{regex}. This command sets an unconditional breakpoint on all
3126 matches, printing a list of all breakpoints it set. Once these
3127 breakpoints are set, they are treated just like the breakpoints set with
3128 the @code{break} command. You can delete them, disable them, or make
3129 them conditional the same way as any other breakpoint.
3131 The syntax of the regular expression is the standard one used with tools
3132 like @file{grep}. Note that this is different from the syntax used by
3133 shells, so for instance @code{foo*} matches all functions that include
3134 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3135 @code{.*} leading and trailing the regular expression you supply, so to
3136 match only functions that begin with @code{foo}, use @code{^foo}.
3138 @cindex non-member C@t{++} functions, set breakpoint in
3139 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3140 breakpoints on overloaded functions that are not members of any special
3143 @cindex set breakpoints on all functions
3144 The @code{rbreak} command can be used to set breakpoints in
3145 @strong{all} the functions in a program, like this:
3148 (@value{GDBP}) rbreak .
3151 @kindex info breakpoints
3152 @cindex @code{$_} and @code{info breakpoints}
3153 @item info breakpoints @r{[}@var{n}@r{]}
3154 @itemx info break @r{[}@var{n}@r{]}
3155 @itemx info watchpoints @r{[}@var{n}@r{]}
3156 Print a table of all breakpoints, watchpoints, and catchpoints set and
3157 not deleted. Optional argument @var{n} means print information only
3158 about the specified breakpoint (or watchpoint or catchpoint). For
3159 each breakpoint, following columns are printed:
3162 @item Breakpoint Numbers
3164 Breakpoint, watchpoint, or catchpoint.
3166 Whether the breakpoint is marked to be disabled or deleted when hit.
3167 @item Enabled or Disabled
3168 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3169 that are not enabled.
3171 Where the breakpoint is in your program, as a memory address. For a
3172 pending breakpoint whose address is not yet known, this field will
3173 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3174 library that has the symbol or line referred by breakpoint is loaded.
3175 See below for details. A breakpoint with several locations will
3176 have @samp{<MULTIPLE>} in this field---see below for details.
3178 Where the breakpoint is in the source for your program, as a file and
3179 line number. For a pending breakpoint, the original string passed to
3180 the breakpoint command will be listed as it cannot be resolved until
3181 the appropriate shared library is loaded in the future.
3185 If a breakpoint is conditional, @code{info break} shows the condition on
3186 the line following the affected breakpoint; breakpoint commands, if any,
3187 are listed after that. A pending breakpoint is allowed to have a condition
3188 specified for it. The condition is not parsed for validity until a shared
3189 library is loaded that allows the pending breakpoint to resolve to a
3193 @code{info break} with a breakpoint
3194 number @var{n} as argument lists only that breakpoint. The
3195 convenience variable @code{$_} and the default examining-address for
3196 the @code{x} command are set to the address of the last breakpoint
3197 listed (@pxref{Memory, ,Examining Memory}).
3200 @code{info break} displays a count of the number of times the breakpoint
3201 has been hit. This is especially useful in conjunction with the
3202 @code{ignore} command. You can ignore a large number of breakpoint
3203 hits, look at the breakpoint info to see how many times the breakpoint
3204 was hit, and then run again, ignoring one less than that number. This
3205 will get you quickly to the last hit of that breakpoint.
3208 @value{GDBN} allows you to set any number of breakpoints at the same place in
3209 your program. There is nothing silly or meaningless about this. When
3210 the breakpoints are conditional, this is even useful
3211 (@pxref{Conditions, ,Break Conditions}).
3213 @cindex multiple locations, breakpoints
3214 @cindex breakpoints, multiple locations
3215 It is possible that a breakpoint corresponds to several locations
3216 in your program. Examples of this situation are:
3220 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3221 instances of the function body, used in different cases.
3224 For a C@t{++} template function, a given line in the function can
3225 correspond to any number of instantiations.
3228 For an inlined function, a given source line can correspond to
3229 several places where that function is inlined.
3232 In all those cases, @value{GDBN} will insert a breakpoint at all
3233 the relevant locations@footnote{
3234 As of this writing, multiple-location breakpoints work only if there's
3235 line number information for all the locations. This means that they
3236 will generally not work in system libraries, unless you have debug
3237 info with line numbers for them.}.
3239 A breakpoint with multiple locations is displayed in the breakpoint
3240 table using several rows---one header row, followed by one row for
3241 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3242 address column. The rows for individual locations contain the actual
3243 addresses for locations, and show the functions to which those
3244 locations belong. The number column for a location is of the form
3245 @var{breakpoint-number}.@var{location-number}.
3250 Num Type Disp Enb Address What
3251 1 breakpoint keep y <MULTIPLE>
3253 breakpoint already hit 1 time
3254 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3255 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3258 Each location can be individually enabled or disabled by passing
3259 @var{breakpoint-number}.@var{location-number} as argument to the
3260 @code{enable} and @code{disable} commands. Note that you cannot
3261 delete the individual locations from the list, you can only delete the
3262 entire list of locations that belong to their parent breakpoint (with
3263 the @kbd{delete @var{num}} command, where @var{num} is the number of
3264 the parent breakpoint, 1 in the above example). Disabling or enabling
3265 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3266 that belong to that breakpoint.
3268 @cindex pending breakpoints
3269 It's quite common to have a breakpoint inside a shared library.
3270 Shared libraries can be loaded and unloaded explicitly,
3271 and possibly repeatedly, as the program is executed. To support
3272 this use case, @value{GDBN} updates breakpoint locations whenever
3273 any shared library is loaded or unloaded. Typically, you would
3274 set a breakpoint in a shared library at the beginning of your
3275 debugging session, when the library is not loaded, and when the
3276 symbols from the library are not available. When you try to set
3277 breakpoint, @value{GDBN} will ask you if you want to set
3278 a so called @dfn{pending breakpoint}---breakpoint whose address
3279 is not yet resolved.
3281 After the program is run, whenever a new shared library is loaded,
3282 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3283 shared library contains the symbol or line referred to by some
3284 pending breakpoint, that breakpoint is resolved and becomes an
3285 ordinary breakpoint. When a library is unloaded, all breakpoints
3286 that refer to its symbols or source lines become pending again.
3288 This logic works for breakpoints with multiple locations, too. For
3289 example, if you have a breakpoint in a C@t{++} template function, and
3290 a newly loaded shared library has an instantiation of that template,
3291 a new location is added to the list of locations for the breakpoint.
3293 Except for having unresolved address, pending breakpoints do not
3294 differ from regular breakpoints. You can set conditions or commands,
3295 enable and disable them and perform other breakpoint operations.
3297 @value{GDBN} provides some additional commands for controlling what
3298 happens when the @samp{break} command cannot resolve breakpoint
3299 address specification to an address:
3301 @kindex set breakpoint pending
3302 @kindex show breakpoint pending
3304 @item set breakpoint pending auto
3305 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3306 location, it queries you whether a pending breakpoint should be created.
3308 @item set breakpoint pending on
3309 This indicates that an unrecognized breakpoint location should automatically
3310 result in a pending breakpoint being created.
3312 @item set breakpoint pending off
3313 This indicates that pending breakpoints are not to be created. Any
3314 unrecognized breakpoint location results in an error. This setting does
3315 not affect any pending breakpoints previously created.
3317 @item show breakpoint pending
3318 Show the current behavior setting for creating pending breakpoints.
3321 The settings above only affect the @code{break} command and its
3322 variants. Once breakpoint is set, it will be automatically updated
3323 as shared libraries are loaded and unloaded.
3325 @cindex automatic hardware breakpoints
3326 For some targets, @value{GDBN} can automatically decide if hardware or
3327 software breakpoints should be used, depending on whether the
3328 breakpoint address is read-only or read-write. This applies to
3329 breakpoints set with the @code{break} command as well as to internal
3330 breakpoints set by commands like @code{next} and @code{finish}. For
3331 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3334 You can control this automatic behaviour with the following commands::
3336 @kindex set breakpoint auto-hw
3337 @kindex show breakpoint auto-hw
3339 @item set breakpoint auto-hw on
3340 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3341 will try to use the target memory map to decide if software or hardware
3342 breakpoint must be used.
3344 @item set breakpoint auto-hw off
3345 This indicates @value{GDBN} should not automatically select breakpoint
3346 type. If the target provides a memory map, @value{GDBN} will warn when
3347 trying to set software breakpoint at a read-only address.
3350 @value{GDBN} normally implements breakpoints by replacing the program code
3351 at the breakpoint address with a special instruction, which, when
3352 executed, given control to the debugger. By default, the program
3353 code is so modified only when the program is resumed. As soon as
3354 the program stops, @value{GDBN} restores the original instructions. This
3355 behaviour guards against leaving breakpoints inserted in the
3356 target should gdb abrubptly disconnect. However, with slow remote
3357 targets, inserting and removing breakpoint can reduce the performance.
3358 This behavior can be controlled with the following commands::
3360 @kindex set breakpoint always-inserted
3361 @kindex show breakpoint always-inserted
3363 @item set breakpoint always-inserted off
3364 All breakpoints, including newly added by the user, are inserted in
3365 the target only when the target is resumed. All breakpoints are
3366 removed from the target when it stops.
3368 @item set breakpoint always-inserted on
3369 Causes all breakpoints to be inserted in the target at all times. If
3370 the user adds a new breakpoint, or changes an existing breakpoint, the
3371 breakpoints in the target are updated immediately. A breakpoint is
3372 removed from the target only when breakpoint itself is removed.
3374 @cindex non-stop mode, and @code{breakpoint always-inserted}
3375 @item set breakpoint always-inserted auto
3376 This is the default mode. If @value{GDBN} is controlling the inferior
3377 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3378 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3379 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3380 @code{breakpoint always-inserted} mode is off.
3383 @cindex negative breakpoint numbers
3384 @cindex internal @value{GDBN} breakpoints
3385 @value{GDBN} itself sometimes sets breakpoints in your program for
3386 special purposes, such as proper handling of @code{longjmp} (in C
3387 programs). These internal breakpoints are assigned negative numbers,
3388 starting with @code{-1}; @samp{info breakpoints} does not display them.
3389 You can see these breakpoints with the @value{GDBN} maintenance command
3390 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3393 @node Set Watchpoints
3394 @subsection Setting Watchpoints
3396 @cindex setting watchpoints
3397 You can use a watchpoint to stop execution whenever the value of an
3398 expression changes, without having to predict a particular place where
3399 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3400 The expression may be as simple as the value of a single variable, or
3401 as complex as many variables combined by operators. Examples include:
3405 A reference to the value of a single variable.
3408 An address cast to an appropriate data type. For example,
3409 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3410 address (assuming an @code{int} occupies 4 bytes).
3413 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3414 expression can use any operators valid in the program's native
3415 language (@pxref{Languages}).
3418 You can set a watchpoint on an expression even if the expression can
3419 not be evaluated yet. For instance, you can set a watchpoint on
3420 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3421 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3422 the expression produces a valid value. If the expression becomes
3423 valid in some other way than changing a variable (e.g.@: if the memory
3424 pointed to by @samp{*global_ptr} becomes readable as the result of a
3425 @code{malloc} call), @value{GDBN} may not stop until the next time
3426 the expression changes.
3428 @cindex software watchpoints
3429 @cindex hardware watchpoints
3430 Depending on your system, watchpoints may be implemented in software or
3431 hardware. @value{GDBN} does software watchpointing by single-stepping your
3432 program and testing the variable's value each time, which is hundreds of
3433 times slower than normal execution. (But this may still be worth it, to
3434 catch errors where you have no clue what part of your program is the
3437 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3438 x86-based targets, @value{GDBN} includes support for hardware
3439 watchpoints, which do not slow down the running of your program.
3443 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3444 Set a watchpoint for an expression. @value{GDBN} will break when the
3445 expression @var{expr} is written into by the program and its value
3446 changes. The simplest (and the most popular) use of this command is
3447 to watch the value of a single variable:
3450 (@value{GDBP}) watch foo
3453 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3454 clause, @value{GDBN} breaks only when the thread identified by
3455 @var{threadnum} changes the value of @var{expr}. If any other threads
3456 change the value of @var{expr}, @value{GDBN} will not break. Note
3457 that watchpoints restricted to a single thread in this way only work
3458 with Hardware Watchpoints.
3461 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3462 Set a watchpoint that will break when the value of @var{expr} is read
3466 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3467 Set a watchpoint that will break when @var{expr} is either read from
3468 or written into by the program.
3470 @kindex info watchpoints @r{[}@var{n}@r{]}
3471 @item info watchpoints
3472 This command prints a list of watchpoints, breakpoints, and catchpoints;
3473 it is the same as @code{info break} (@pxref{Set Breaks}).
3476 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3477 watchpoints execute very quickly, and the debugger reports a change in
3478 value at the exact instruction where the change occurs. If @value{GDBN}
3479 cannot set a hardware watchpoint, it sets a software watchpoint, which
3480 executes more slowly and reports the change in value at the next
3481 @emph{statement}, not the instruction, after the change occurs.
3483 @cindex use only software watchpoints
3484 You can force @value{GDBN} to use only software watchpoints with the
3485 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3486 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3487 the underlying system supports them. (Note that hardware-assisted
3488 watchpoints that were set @emph{before} setting
3489 @code{can-use-hw-watchpoints} to zero will still use the hardware
3490 mechanism of watching expression values.)
3493 @item set can-use-hw-watchpoints
3494 @kindex set can-use-hw-watchpoints
3495 Set whether or not to use hardware watchpoints.
3497 @item show can-use-hw-watchpoints
3498 @kindex show can-use-hw-watchpoints
3499 Show the current mode of using hardware watchpoints.
3502 For remote targets, you can restrict the number of hardware
3503 watchpoints @value{GDBN} will use, see @ref{set remote
3504 hardware-breakpoint-limit}.
3506 When you issue the @code{watch} command, @value{GDBN} reports
3509 Hardware watchpoint @var{num}: @var{expr}
3513 if it was able to set a hardware watchpoint.
3515 Currently, the @code{awatch} and @code{rwatch} commands can only set
3516 hardware watchpoints, because accesses to data that don't change the
3517 value of the watched expression cannot be detected without examining
3518 every instruction as it is being executed, and @value{GDBN} does not do
3519 that currently. If @value{GDBN} finds that it is unable to set a
3520 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3521 will print a message like this:
3524 Expression cannot be implemented with read/access watchpoint.
3527 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3528 data type of the watched expression is wider than what a hardware
3529 watchpoint on the target machine can handle. For example, some systems
3530 can only watch regions that are up to 4 bytes wide; on such systems you
3531 cannot set hardware watchpoints for an expression that yields a
3532 double-precision floating-point number (which is typically 8 bytes
3533 wide). As a work-around, it might be possible to break the large region
3534 into a series of smaller ones and watch them with separate watchpoints.
3536 If you set too many hardware watchpoints, @value{GDBN} might be unable
3537 to insert all of them when you resume the execution of your program.
3538 Since the precise number of active watchpoints is unknown until such
3539 time as the program is about to be resumed, @value{GDBN} might not be
3540 able to warn you about this when you set the watchpoints, and the
3541 warning will be printed only when the program is resumed:
3544 Hardware watchpoint @var{num}: Could not insert watchpoint
3548 If this happens, delete or disable some of the watchpoints.
3550 Watching complex expressions that reference many variables can also
3551 exhaust the resources available for hardware-assisted watchpoints.
3552 That's because @value{GDBN} needs to watch every variable in the
3553 expression with separately allocated resources.
3555 If you call a function interactively using @code{print} or @code{call},
3556 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3557 kind of breakpoint or the call completes.
3559 @value{GDBN} automatically deletes watchpoints that watch local
3560 (automatic) variables, or expressions that involve such variables, when
3561 they go out of scope, that is, when the execution leaves the block in
3562 which these variables were defined. In particular, when the program
3563 being debugged terminates, @emph{all} local variables go out of scope,
3564 and so only watchpoints that watch global variables remain set. If you
3565 rerun the program, you will need to set all such watchpoints again. One
3566 way of doing that would be to set a code breakpoint at the entry to the
3567 @code{main} function and when it breaks, set all the watchpoints.
3569 @cindex watchpoints and threads
3570 @cindex threads and watchpoints
3571 In multi-threaded programs, watchpoints will detect changes to the
3572 watched expression from every thread.
3575 @emph{Warning:} In multi-threaded programs, software watchpoints
3576 have only limited usefulness. If @value{GDBN} creates a software
3577 watchpoint, it can only watch the value of an expression @emph{in a
3578 single thread}. If you are confident that the expression can only
3579 change due to the current thread's activity (and if you are also
3580 confident that no other thread can become current), then you can use
3581 software watchpoints as usual. However, @value{GDBN} may not notice
3582 when a non-current thread's activity changes the expression. (Hardware
3583 watchpoints, in contrast, watch an expression in all threads.)
3586 @xref{set remote hardware-watchpoint-limit}.
3588 @node Set Catchpoints
3589 @subsection Setting Catchpoints
3590 @cindex catchpoints, setting
3591 @cindex exception handlers
3592 @cindex event handling
3594 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3595 kinds of program events, such as C@t{++} exceptions or the loading of a
3596 shared library. Use the @code{catch} command to set a catchpoint.
3600 @item catch @var{event}
3601 Stop when @var{event} occurs. @var{event} can be any of the following:
3604 @cindex stop on C@t{++} exceptions
3605 The throwing of a C@t{++} exception.
3608 The catching of a C@t{++} exception.
3611 @cindex Ada exception catching
3612 @cindex catch Ada exceptions
3613 An Ada exception being raised. If an exception name is specified
3614 at the end of the command (eg @code{catch exception Program_Error}),
3615 the debugger will stop only when this specific exception is raised.
3616 Otherwise, the debugger stops execution when any Ada exception is raised.
3618 When inserting an exception catchpoint on a user-defined exception whose
3619 name is identical to one of the exceptions defined by the language, the
3620 fully qualified name must be used as the exception name. Otherwise,
3621 @value{GDBN} will assume that it should stop on the pre-defined exception
3622 rather than the user-defined one. For instance, assuming an exception
3623 called @code{Constraint_Error} is defined in package @code{Pck}, then
3624 the command to use to catch such exceptions is @kbd{catch exception
3625 Pck.Constraint_Error}.
3627 @item exception unhandled
3628 An exception that was raised but is not handled by the program.
3631 A failed Ada assertion.
3634 @cindex break on fork/exec
3635 A call to @code{exec}. This is currently only available for HP-UX
3639 A call to @code{fork}. This is currently only available for HP-UX
3643 A call to @code{vfork}. This is currently only available for HP-UX
3647 @itemx load @var{libname}
3648 @cindex break on load/unload of shared library
3649 The dynamic loading of any shared library, or the loading of the library
3650 @var{libname}. This is currently only available for HP-UX.
3653 @itemx unload @var{libname}
3654 The unloading of any dynamically loaded shared library, or the unloading
3655 of the library @var{libname}. This is currently only available for HP-UX.
3658 @item tcatch @var{event}
3659 Set a catchpoint that is enabled only for one stop. The catchpoint is
3660 automatically deleted after the first time the event is caught.
3664 Use the @code{info break} command to list the current catchpoints.
3666 There are currently some limitations to C@t{++} exception handling
3667 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3671 If you call a function interactively, @value{GDBN} normally returns
3672 control to you when the function has finished executing. If the call
3673 raises an exception, however, the call may bypass the mechanism that
3674 returns control to you and cause your program either to abort or to
3675 simply continue running until it hits a breakpoint, catches a signal
3676 that @value{GDBN} is listening for, or exits. This is the case even if
3677 you set a catchpoint for the exception; catchpoints on exceptions are
3678 disabled within interactive calls.
3681 You cannot raise an exception interactively.
3684 You cannot install an exception handler interactively.
3687 @cindex raise exceptions
3688 Sometimes @code{catch} is not the best way to debug exception handling:
3689 if you need to know exactly where an exception is raised, it is better to
3690 stop @emph{before} the exception handler is called, since that way you
3691 can see the stack before any unwinding takes place. If you set a
3692 breakpoint in an exception handler instead, it may not be easy to find
3693 out where the exception was raised.
3695 To stop just before an exception handler is called, you need some
3696 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3697 raised by calling a library function named @code{__raise_exception}
3698 which has the following ANSI C interface:
3701 /* @var{addr} is where the exception identifier is stored.
3702 @var{id} is the exception identifier. */
3703 void __raise_exception (void **addr, void *id);
3707 To make the debugger catch all exceptions before any stack
3708 unwinding takes place, set a breakpoint on @code{__raise_exception}
3709 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3711 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3712 that depends on the value of @var{id}, you can stop your program when
3713 a specific exception is raised. You can use multiple conditional
3714 breakpoints to stop your program when any of a number of exceptions are
3719 @subsection Deleting Breakpoints
3721 @cindex clearing breakpoints, watchpoints, catchpoints
3722 @cindex deleting breakpoints, watchpoints, catchpoints
3723 It is often necessary to eliminate a breakpoint, watchpoint, or
3724 catchpoint once it has done its job and you no longer want your program
3725 to stop there. This is called @dfn{deleting} the breakpoint. A
3726 breakpoint that has been deleted no longer exists; it is forgotten.
3728 With the @code{clear} command you can delete breakpoints according to
3729 where they are in your program. With the @code{delete} command you can
3730 delete individual breakpoints, watchpoints, or catchpoints by specifying
3731 their breakpoint numbers.
3733 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3734 automatically ignores breakpoints on the first instruction to be executed
3735 when you continue execution without changing the execution address.
3740 Delete any breakpoints at the next instruction to be executed in the
3741 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3742 the innermost frame is selected, this is a good way to delete a
3743 breakpoint where your program just stopped.
3745 @item clear @var{location}
3746 Delete any breakpoints set at the specified @var{location}.
3747 @xref{Specify Location}, for the various forms of @var{location}; the
3748 most useful ones are listed below:
3751 @item clear @var{function}
3752 @itemx clear @var{filename}:@var{function}
3753 Delete any breakpoints set at entry to the named @var{function}.
3755 @item clear @var{linenum}
3756 @itemx clear @var{filename}:@var{linenum}
3757 Delete any breakpoints set at or within the code of the specified
3758 @var{linenum} of the specified @var{filename}.
3761 @cindex delete breakpoints
3763 @kindex d @r{(@code{delete})}
3764 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3765 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3766 ranges specified as arguments. If no argument is specified, delete all
3767 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3768 confirm off}). You can abbreviate this command as @code{d}.
3772 @subsection Disabling Breakpoints
3774 @cindex enable/disable a breakpoint
3775 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3776 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3777 it had been deleted, but remembers the information on the breakpoint so
3778 that you can @dfn{enable} it again later.
3780 You disable and enable breakpoints, watchpoints, and catchpoints with
3781 the @code{enable} and @code{disable} commands, optionally specifying one
3782 or more breakpoint numbers as arguments. Use @code{info break} or
3783 @code{info watch} to print a list of breakpoints, watchpoints, and
3784 catchpoints if you do not know which numbers to use.
3786 Disabling and enabling a breakpoint that has multiple locations
3787 affects all of its locations.
3789 A breakpoint, watchpoint, or catchpoint can have any of four different
3790 states of enablement:
3794 Enabled. The breakpoint stops your program. A breakpoint set
3795 with the @code{break} command starts out in this state.
3797 Disabled. The breakpoint has no effect on your program.
3799 Enabled once. The breakpoint stops your program, but then becomes
3802 Enabled for deletion. The breakpoint stops your program, but
3803 immediately after it does so it is deleted permanently. A breakpoint
3804 set with the @code{tbreak} command starts out in this state.
3807 You can use the following commands to enable or disable breakpoints,
3808 watchpoints, and catchpoints:
3812 @kindex dis @r{(@code{disable})}
3813 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3814 Disable the specified breakpoints---or all breakpoints, if none are
3815 listed. A disabled breakpoint has no effect but is not forgotten. All
3816 options such as ignore-counts, conditions and commands are remembered in
3817 case the breakpoint is enabled again later. You may abbreviate
3818 @code{disable} as @code{dis}.
3821 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3822 Enable the specified breakpoints (or all defined breakpoints). They
3823 become effective once again in stopping your program.
3825 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3826 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3827 of these breakpoints immediately after stopping your program.
3829 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3830 Enable the specified breakpoints to work once, then die. @value{GDBN}
3831 deletes any of these breakpoints as soon as your program stops there.
3832 Breakpoints set by the @code{tbreak} command start out in this state.
3835 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3836 @c confusing: tbreak is also initially enabled.
3837 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3838 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3839 subsequently, they become disabled or enabled only when you use one of
3840 the commands above. (The command @code{until} can set and delete a
3841 breakpoint of its own, but it does not change the state of your other
3842 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3846 @subsection Break Conditions
3847 @cindex conditional breakpoints
3848 @cindex breakpoint conditions
3850 @c FIXME what is scope of break condition expr? Context where wanted?
3851 @c in particular for a watchpoint?
3852 The simplest sort of breakpoint breaks every time your program reaches a
3853 specified place. You can also specify a @dfn{condition} for a
3854 breakpoint. A condition is just a Boolean expression in your
3855 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3856 a condition evaluates the expression each time your program reaches it,
3857 and your program stops only if the condition is @emph{true}.
3859 This is the converse of using assertions for program validation; in that
3860 situation, you want to stop when the assertion is violated---that is,
3861 when the condition is false. In C, if you want to test an assertion expressed
3862 by the condition @var{assert}, you should set the condition
3863 @samp{! @var{assert}} on the appropriate breakpoint.
3865 Conditions are also accepted for watchpoints; you may not need them,
3866 since a watchpoint is inspecting the value of an expression anyhow---but
3867 it might be simpler, say, to just set a watchpoint on a variable name,
3868 and specify a condition that tests whether the new value is an interesting
3871 Break conditions can have side effects, and may even call functions in
3872 your program. This can be useful, for example, to activate functions
3873 that log program progress, or to use your own print functions to
3874 format special data structures. The effects are completely predictable
3875 unless there is another enabled breakpoint at the same address. (In
3876 that case, @value{GDBN} might see the other breakpoint first and stop your
3877 program without checking the condition of this one.) Note that
3878 breakpoint commands are usually more convenient and flexible than break
3880 purpose of performing side effects when a breakpoint is reached
3881 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3883 Break conditions can be specified when a breakpoint is set, by using
3884 @samp{if} in the arguments to the @code{break} command. @xref{Set
3885 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3886 with the @code{condition} command.
3888 You can also use the @code{if} keyword with the @code{watch} command.
3889 The @code{catch} command does not recognize the @code{if} keyword;
3890 @code{condition} is the only way to impose a further condition on a
3895 @item condition @var{bnum} @var{expression}
3896 Specify @var{expression} as the break condition for breakpoint,
3897 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3898 breakpoint @var{bnum} stops your program only if the value of
3899 @var{expression} is true (nonzero, in C). When you use
3900 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3901 syntactic correctness, and to determine whether symbols in it have
3902 referents in the context of your breakpoint. If @var{expression} uses
3903 symbols not referenced in the context of the breakpoint, @value{GDBN}
3904 prints an error message:
3907 No symbol "foo" in current context.
3912 not actually evaluate @var{expression} at the time the @code{condition}
3913 command (or a command that sets a breakpoint with a condition, like
3914 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3916 @item condition @var{bnum}
3917 Remove the condition from breakpoint number @var{bnum}. It becomes
3918 an ordinary unconditional breakpoint.
3921 @cindex ignore count (of breakpoint)
3922 A special case of a breakpoint condition is to stop only when the
3923 breakpoint has been reached a certain number of times. This is so
3924 useful that there is a special way to do it, using the @dfn{ignore
3925 count} of the breakpoint. Every breakpoint has an ignore count, which
3926 is an integer. Most of the time, the ignore count is zero, and
3927 therefore has no effect. But if your program reaches a breakpoint whose
3928 ignore count is positive, then instead of stopping, it just decrements
3929 the ignore count by one and continues. As a result, if the ignore count
3930 value is @var{n}, the breakpoint does not stop the next @var{n} times
3931 your program reaches it.
3935 @item ignore @var{bnum} @var{count}
3936 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3937 The next @var{count} times the breakpoint is reached, your program's
3938 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3941 To make the breakpoint stop the next time it is reached, specify
3944 When you use @code{continue} to resume execution of your program from a
3945 breakpoint, you can specify an ignore count directly as an argument to
3946 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3947 Stepping,,Continuing and Stepping}.
3949 If a breakpoint has a positive ignore count and a condition, the
3950 condition is not checked. Once the ignore count reaches zero,
3951 @value{GDBN} resumes checking the condition.
3953 You could achieve the effect of the ignore count with a condition such
3954 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3955 is decremented each time. @xref{Convenience Vars, ,Convenience
3959 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3962 @node Break Commands
3963 @subsection Breakpoint Command Lists
3965 @cindex breakpoint commands
3966 You can give any breakpoint (or watchpoint or catchpoint) a series of
3967 commands to execute when your program stops due to that breakpoint. For
3968 example, you might want to print the values of certain expressions, or
3969 enable other breakpoints.
3973 @kindex end@r{ (breakpoint commands)}
3974 @item commands @r{[}@var{bnum}@r{]}
3975 @itemx @dots{} @var{command-list} @dots{}
3977 Specify a list of commands for breakpoint number @var{bnum}. The commands
3978 themselves appear on the following lines. Type a line containing just
3979 @code{end} to terminate the commands.
3981 To remove all commands from a breakpoint, type @code{commands} and
3982 follow it immediately with @code{end}; that is, give no commands.
3984 With no @var{bnum} argument, @code{commands} refers to the last
3985 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3986 recently encountered).
3989 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3990 disabled within a @var{command-list}.
3992 You can use breakpoint commands to start your program up again. Simply
3993 use the @code{continue} command, or @code{step}, or any other command
3994 that resumes execution.
3996 Any other commands in the command list, after a command that resumes
3997 execution, are ignored. This is because any time you resume execution
3998 (even with a simple @code{next} or @code{step}), you may encounter
3999 another breakpoint---which could have its own command list, leading to
4000 ambiguities about which list to execute.
4003 If the first command you specify in a command list is @code{silent}, the
4004 usual message about stopping at a breakpoint is not printed. This may
4005 be desirable for breakpoints that are to print a specific message and
4006 then continue. If none of the remaining commands print anything, you
4007 see no sign that the breakpoint was reached. @code{silent} is
4008 meaningful only at the beginning of a breakpoint command list.
4010 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4011 print precisely controlled output, and are often useful in silent
4012 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4014 For example, here is how you could use breakpoint commands to print the
4015 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4021 printf "x is %d\n",x
4026 One application for breakpoint commands is to compensate for one bug so
4027 you can test for another. Put a breakpoint just after the erroneous line
4028 of code, give it a condition to detect the case in which something
4029 erroneous has been done, and give it commands to assign correct values
4030 to any variables that need them. End with the @code{continue} command
4031 so that your program does not stop, and start with the @code{silent}
4032 command so that no output is produced. Here is an example:
4043 @c @ifclear BARETARGET
4044 @node Error in Breakpoints
4045 @subsection ``Cannot insert breakpoints''
4047 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
4049 Under some operating systems, breakpoints cannot be used in a program if
4050 any other process is running that program. In this situation,
4051 attempting to run or continue a program with a breakpoint causes
4052 @value{GDBN} to print an error message:
4055 Cannot insert breakpoints.
4056 The same program may be running in another process.
4059 When this happens, you have three ways to proceed:
4063 Remove or disable the breakpoints, then continue.
4066 Suspend @value{GDBN}, and copy the file containing your program to a new
4067 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4068 that @value{GDBN} should run your program under that name.
4069 Then start your program again.
4072 Relink your program so that the text segment is nonsharable, using the
4073 linker option @samp{-N}. The operating system limitation may not apply
4074 to nonsharable executables.
4078 A similar message can be printed if you request too many active
4079 hardware-assisted breakpoints and watchpoints:
4081 @c FIXME: the precise wording of this message may change; the relevant
4082 @c source change is not committed yet (Sep 3, 1999).
4084 Stopped; cannot insert breakpoints.
4085 You may have requested too many hardware breakpoints and watchpoints.
4089 This message is printed when you attempt to resume the program, since
4090 only then @value{GDBN} knows exactly how many hardware breakpoints and
4091 watchpoints it needs to insert.
4093 When this message is printed, you need to disable or remove some of the
4094 hardware-assisted breakpoints and watchpoints, and then continue.
4096 @node Breakpoint-related Warnings
4097 @subsection ``Breakpoint address adjusted...''
4098 @cindex breakpoint address adjusted
4100 Some processor architectures place constraints on the addresses at
4101 which breakpoints may be placed. For architectures thus constrained,
4102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4103 with the constraints dictated by the architecture.
4105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4106 a VLIW architecture in which a number of RISC-like instructions may be
4107 bundled together for parallel execution. The FR-V architecture
4108 constrains the location of a breakpoint instruction within such a
4109 bundle to the instruction with the lowest address. @value{GDBN}
4110 honors this constraint by adjusting a breakpoint's address to the
4111 first in the bundle.
4113 It is not uncommon for optimized code to have bundles which contain
4114 instructions from different source statements, thus it may happen that
4115 a breakpoint's address will be adjusted from one source statement to
4116 another. Since this adjustment may significantly alter @value{GDBN}'s
4117 breakpoint related behavior from what the user expects, a warning is
4118 printed when the breakpoint is first set and also when the breakpoint
4121 A warning like the one below is printed when setting a breakpoint
4122 that's been subject to address adjustment:
4125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4128 Such warnings are printed both for user settable and @value{GDBN}'s
4129 internal breakpoints. If you see one of these warnings, you should
4130 verify that a breakpoint set at the adjusted address will have the
4131 desired affect. If not, the breakpoint in question may be removed and
4132 other breakpoints may be set which will have the desired behavior.
4133 E.g., it may be sufficient to place the breakpoint at a later
4134 instruction. A conditional breakpoint may also be useful in some
4135 cases to prevent the breakpoint from triggering too often.
4137 @value{GDBN} will also issue a warning when stopping at one of these
4138 adjusted breakpoints:
4141 warning: Breakpoint 1 address previously adjusted from 0x00010414
4145 When this warning is encountered, it may be too late to take remedial
4146 action except in cases where the breakpoint is hit earlier or more
4147 frequently than expected.
4149 @node Continuing and Stepping
4150 @section Continuing and Stepping
4154 @cindex resuming execution
4155 @dfn{Continuing} means resuming program execution until your program
4156 completes normally. In contrast, @dfn{stepping} means executing just
4157 one more ``step'' of your program, where ``step'' may mean either one
4158 line of source code, or one machine instruction (depending on what
4159 particular command you use). Either when continuing or when stepping,
4160 your program may stop even sooner, due to a breakpoint or a signal. (If
4161 it stops due to a signal, you may want to use @code{handle}, or use
4162 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4166 @kindex c @r{(@code{continue})}
4167 @kindex fg @r{(resume foreground execution)}
4168 @item continue @r{[}@var{ignore-count}@r{]}
4169 @itemx c @r{[}@var{ignore-count}@r{]}
4170 @itemx fg @r{[}@var{ignore-count}@r{]}
4171 Resume program execution, at the address where your program last stopped;
4172 any breakpoints set at that address are bypassed. The optional argument
4173 @var{ignore-count} allows you to specify a further number of times to
4174 ignore a breakpoint at this location; its effect is like that of
4175 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4177 The argument @var{ignore-count} is meaningful only when your program
4178 stopped due to a breakpoint. At other times, the argument to
4179 @code{continue} is ignored.
4181 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4182 debugged program is deemed to be the foreground program) are provided
4183 purely for convenience, and have exactly the same behavior as
4187 To resume execution at a different place, you can use @code{return}
4188 (@pxref{Returning, ,Returning from a Function}) to go back to the
4189 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4190 Different Address}) to go to an arbitrary location in your program.
4192 A typical technique for using stepping is to set a breakpoint
4193 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4194 beginning of the function or the section of your program where a problem
4195 is believed to lie, run your program until it stops at that breakpoint,
4196 and then step through the suspect area, examining the variables that are
4197 interesting, until you see the problem happen.
4201 @kindex s @r{(@code{step})}
4203 Continue running your program until control reaches a different source
4204 line, then stop it and return control to @value{GDBN}. This command is
4205 abbreviated @code{s}.
4208 @c "without debugging information" is imprecise; actually "without line
4209 @c numbers in the debugging information". (gcc -g1 has debugging info but
4210 @c not line numbers). But it seems complex to try to make that
4211 @c distinction here.
4212 @emph{Warning:} If you use the @code{step} command while control is
4213 within a function that was compiled without debugging information,
4214 execution proceeds until control reaches a function that does have
4215 debugging information. Likewise, it will not step into a function which
4216 is compiled without debugging information. To step through functions
4217 without debugging information, use the @code{stepi} command, described
4221 The @code{step} command only stops at the first instruction of a source
4222 line. This prevents the multiple stops that could otherwise occur in
4223 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4224 to stop if a function that has debugging information is called within
4225 the line. In other words, @code{step} @emph{steps inside} any functions
4226 called within the line.
4228 Also, the @code{step} command only enters a function if there is line
4229 number information for the function. Otherwise it acts like the
4230 @code{next} command. This avoids problems when using @code{cc -gl}
4231 on MIPS machines. Previously, @code{step} entered subroutines if there
4232 was any debugging information about the routine.
4234 @item step @var{count}
4235 Continue running as in @code{step}, but do so @var{count} times. If a
4236 breakpoint is reached, or a signal not related to stepping occurs before
4237 @var{count} steps, stepping stops right away.
4240 @kindex n @r{(@code{next})}
4241 @item next @r{[}@var{count}@r{]}
4242 Continue to the next source line in the current (innermost) stack frame.
4243 This is similar to @code{step}, but function calls that appear within
4244 the line of code are executed without stopping. Execution stops when
4245 control reaches a different line of code at the original stack level
4246 that was executing when you gave the @code{next} command. This command
4247 is abbreviated @code{n}.
4249 An argument @var{count} is a repeat count, as for @code{step}.
4252 @c FIX ME!! Do we delete this, or is there a way it fits in with
4253 @c the following paragraph? --- Vctoria
4255 @c @code{next} within a function that lacks debugging information acts like
4256 @c @code{step}, but any function calls appearing within the code of the
4257 @c function are executed without stopping.
4259 The @code{next} command only stops at the first instruction of a
4260 source line. This prevents multiple stops that could otherwise occur in
4261 @code{switch} statements, @code{for} loops, etc.
4263 @kindex set step-mode
4265 @cindex functions without line info, and stepping
4266 @cindex stepping into functions with no line info
4267 @itemx set step-mode on
4268 The @code{set step-mode on} command causes the @code{step} command to
4269 stop at the first instruction of a function which contains no debug line
4270 information rather than stepping over it.
4272 This is useful in cases where you may be interested in inspecting the
4273 machine instructions of a function which has no symbolic info and do not
4274 want @value{GDBN} to automatically skip over this function.
4276 @item set step-mode off
4277 Causes the @code{step} command to step over any functions which contains no
4278 debug information. This is the default.
4280 @item show step-mode
4281 Show whether @value{GDBN} will stop in or step over functions without
4282 source line debug information.
4285 @kindex fin @r{(@code{finish})}
4287 Continue running until just after function in the selected stack frame
4288 returns. Print the returned value (if any). This command can be
4289 abbreviated as @code{fin}.
4291 Contrast this with the @code{return} command (@pxref{Returning,
4292 ,Returning from a Function}).
4295 @kindex u @r{(@code{until})}
4296 @cindex run until specified location
4299 Continue running until a source line past the current line, in the
4300 current stack frame, is reached. This command is used to avoid single
4301 stepping through a loop more than once. It is like the @code{next}
4302 command, except that when @code{until} encounters a jump, it
4303 automatically continues execution until the program counter is greater
4304 than the address of the jump.
4306 This means that when you reach the end of a loop after single stepping
4307 though it, @code{until} makes your program continue execution until it
4308 exits the loop. In contrast, a @code{next} command at the end of a loop
4309 simply steps back to the beginning of the loop, which forces you to step
4310 through the next iteration.
4312 @code{until} always stops your program if it attempts to exit the current
4315 @code{until} may produce somewhat counterintuitive results if the order
4316 of machine code does not match the order of the source lines. For
4317 example, in the following excerpt from a debugging session, the @code{f}
4318 (@code{frame}) command shows that execution is stopped at line
4319 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4323 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4325 (@value{GDBP}) until
4326 195 for ( ; argc > 0; NEXTARG) @{
4329 This happened because, for execution efficiency, the compiler had
4330 generated code for the loop closure test at the end, rather than the
4331 start, of the loop---even though the test in a C @code{for}-loop is
4332 written before the body of the loop. The @code{until} command appeared
4333 to step back to the beginning of the loop when it advanced to this
4334 expression; however, it has not really gone to an earlier
4335 statement---not in terms of the actual machine code.
4337 @code{until} with no argument works by means of single
4338 instruction stepping, and hence is slower than @code{until} with an
4341 @item until @var{location}
4342 @itemx u @var{location}
4343 Continue running your program until either the specified location is
4344 reached, or the current stack frame returns. @var{location} is any of
4345 the forms described in @ref{Specify Location}.
4346 This form of the command uses temporary breakpoints, and
4347 hence is quicker than @code{until} without an argument. The specified
4348 location is actually reached only if it is in the current frame. This
4349 implies that @code{until} can be used to skip over recursive function
4350 invocations. For instance in the code below, if the current location is
4351 line @code{96}, issuing @code{until 99} will execute the program up to
4352 line @code{99} in the same invocation of factorial, i.e., after the inner
4353 invocations have returned.
4356 94 int factorial (int value)
4358 96 if (value > 1) @{
4359 97 value *= factorial (value - 1);
4366 @kindex advance @var{location}
4367 @itemx advance @var{location}
4368 Continue running the program up to the given @var{location}. An argument is
4369 required, which should be of one of the forms described in
4370 @ref{Specify Location}.
4371 Execution will also stop upon exit from the current stack
4372 frame. This command is similar to @code{until}, but @code{advance} will
4373 not skip over recursive function calls, and the target location doesn't
4374 have to be in the same frame as the current one.
4378 @kindex si @r{(@code{stepi})}
4380 @itemx stepi @var{arg}
4382 Execute one machine instruction, then stop and return to the debugger.
4384 It is often useful to do @samp{display/i $pc} when stepping by machine
4385 instructions. This makes @value{GDBN} automatically display the next
4386 instruction to be executed, each time your program stops. @xref{Auto
4387 Display,, Automatic Display}.
4389 An argument is a repeat count, as in @code{step}.
4393 @kindex ni @r{(@code{nexti})}
4395 @itemx nexti @var{arg}
4397 Execute one machine instruction, but if it is a function call,
4398 proceed until the function returns.
4400 An argument is a repeat count, as in @code{next}.
4407 A signal is an asynchronous event that can happen in a program. The
4408 operating system defines the possible kinds of signals, and gives each
4409 kind a name and a number. For example, in Unix @code{SIGINT} is the
4410 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4411 @code{SIGSEGV} is the signal a program gets from referencing a place in
4412 memory far away from all the areas in use; @code{SIGALRM} occurs when
4413 the alarm clock timer goes off (which happens only if your program has
4414 requested an alarm).
4416 @cindex fatal signals
4417 Some signals, including @code{SIGALRM}, are a normal part of the
4418 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4419 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4420 program has not specified in advance some other way to handle the signal.
4421 @code{SIGINT} does not indicate an error in your program, but it is normally
4422 fatal so it can carry out the purpose of the interrupt: to kill the program.
4424 @value{GDBN} has the ability to detect any occurrence of a signal in your
4425 program. You can tell @value{GDBN} in advance what to do for each kind of
4428 @cindex handling signals
4429 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4430 @code{SIGALRM} be silently passed to your program
4431 (so as not to interfere with their role in the program's functioning)
4432 but to stop your program immediately whenever an error signal happens.
4433 You can change these settings with the @code{handle} command.
4436 @kindex info signals
4440 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4441 handle each one. You can use this to see the signal numbers of all
4442 the defined types of signals.
4444 @item info signals @var{sig}
4445 Similar, but print information only about the specified signal number.
4447 @code{info handle} is an alias for @code{info signals}.
4450 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4451 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4452 can be the number of a signal or its name (with or without the
4453 @samp{SIG} at the beginning); a list of signal numbers of the form
4454 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4455 known signals. Optional arguments @var{keywords}, described below,
4456 say what change to make.
4460 The keywords allowed by the @code{handle} command can be abbreviated.
4461 Their full names are:
4465 @value{GDBN} should not stop your program when this signal happens. It may
4466 still print a message telling you that the signal has come in.
4469 @value{GDBN} should stop your program when this signal happens. This implies
4470 the @code{print} keyword as well.
4473 @value{GDBN} should print a message when this signal happens.
4476 @value{GDBN} should not mention the occurrence of the signal at all. This
4477 implies the @code{nostop} keyword as well.
4481 @value{GDBN} should allow your program to see this signal; your program
4482 can handle the signal, or else it may terminate if the signal is fatal
4483 and not handled. @code{pass} and @code{noignore} are synonyms.
4487 @value{GDBN} should not allow your program to see this signal.
4488 @code{nopass} and @code{ignore} are synonyms.
4492 When a signal stops your program, the signal is not visible to the
4494 continue. Your program sees the signal then, if @code{pass} is in
4495 effect for the signal in question @emph{at that time}. In other words,
4496 after @value{GDBN} reports a signal, you can use the @code{handle}
4497 command with @code{pass} or @code{nopass} to control whether your
4498 program sees that signal when you continue.
4500 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4501 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4502 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4505 You can also use the @code{signal} command to prevent your program from
4506 seeing a signal, or cause it to see a signal it normally would not see,
4507 or to give it any signal at any time. For example, if your program stopped
4508 due to some sort of memory reference error, you might store correct
4509 values into the erroneous variables and continue, hoping to see more
4510 execution; but your program would probably terminate immediately as
4511 a result of the fatal signal once it saw the signal. To prevent this,
4512 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4516 @section Stopping and Starting Multi-thread Programs
4518 @cindex stopped threads
4519 @cindex threads, stopped
4521 @cindex continuing threads
4522 @cindex threads, continuing
4524 @value{GDBN} supports debugging programs with multiple threads
4525 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4526 are two modes of controlling execution of your program within the
4527 debugger. In the default mode, referred to as @dfn{all-stop mode},
4528 when any thread in your program stops (for example, at a breakpoint
4529 or while being stepped), all other threads in the program are also stopped by
4530 @value{GDBN}. On some targets, @value{GDBN} also supports
4531 @dfn{non-stop mode}, in which other threads can continue to run freely while
4532 you examine the stopped thread in the debugger.
4535 * All-Stop Mode:: All threads stop when GDB takes control
4536 * Non-Stop Mode:: Other threads continue to execute
4537 * Background Execution:: Running your program asynchronously
4538 * Thread-Specific Breakpoints:: Controlling breakpoints
4539 * Interrupted System Calls:: GDB may interfere with system calls
4543 @subsection All-Stop Mode
4545 @cindex all-stop mode
4547 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4548 @emph{all} threads of execution stop, not just the current thread. This
4549 allows you to examine the overall state of the program, including
4550 switching between threads, without worrying that things may change
4553 Conversely, whenever you restart the program, @emph{all} threads start
4554 executing. @emph{This is true even when single-stepping} with commands
4555 like @code{step} or @code{next}.
4557 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4558 Since thread scheduling is up to your debugging target's operating
4559 system (not controlled by @value{GDBN}), other threads may
4560 execute more than one statement while the current thread completes a
4561 single step. Moreover, in general other threads stop in the middle of a
4562 statement, rather than at a clean statement boundary, when the program
4565 You might even find your program stopped in another thread after
4566 continuing or even single-stepping. This happens whenever some other
4567 thread runs into a breakpoint, a signal, or an exception before the
4568 first thread completes whatever you requested.
4570 @cindex automatic thread selection
4571 @cindex switching threads automatically
4572 @cindex threads, automatic switching
4573 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4574 signal, it automatically selects the thread where that breakpoint or
4575 signal happened. @value{GDBN} alerts you to the context switch with a
4576 message such as @samp{[Switching to Thread @var{n}]} to identify the
4579 On some OSes, you can modify @value{GDBN}'s default behavior by
4580 locking the OS scheduler to allow only a single thread to run.
4583 @item set scheduler-locking @var{mode}
4584 @cindex scheduler locking mode
4585 @cindex lock scheduler
4586 Set the scheduler locking mode. If it is @code{off}, then there is no
4587 locking and any thread may run at any time. If @code{on}, then only the
4588 current thread may run when the inferior is resumed. The @code{step}
4589 mode optimizes for single-stepping; it prevents other threads
4590 from preempting the current thread while you are stepping, so that
4591 the focus of debugging does not change unexpectedly.
4592 Other threads only rarely (or never) get a chance to run
4593 when you step. They are more likely to run when you @samp{next} over a
4594 function call, and they are completely free to run when you use commands
4595 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4596 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4597 the current thread away from the thread that you are debugging.
4599 @item show scheduler-locking
4600 Display the current scheduler locking mode.
4604 @subsection Non-Stop Mode
4606 @cindex non-stop mode
4608 @c This section is really only a place-holder, and needs to be expanded
4609 @c with more details.
4611 For some multi-threaded targets, @value{GDBN} supports an optional
4612 mode of operation in which you can examine stopped program threads in
4613 the debugger while other threads continue to execute freely. This
4614 minimizes intrusion when debugging live systems, such as programs
4615 where some threads have real-time constraints or must continue to
4616 respond to external events. This is referred to as @dfn{non-stop} mode.
4618 In non-stop mode, when a thread stops to report a debugging event,
4619 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4620 threads as well, in contrast to the all-stop mode behavior. Additionally,
4621 execution commands such as @code{continue} and @code{step} apply by default
4622 only to the current thread in non-stop mode, rather than all threads as
4623 in all-stop mode. This allows you to control threads explicitly in
4624 ways that are not possible in all-stop mode --- for example, stepping
4625 one thread while allowing others to run freely, stepping
4626 one thread while holding all others stopped, or stepping several threads
4627 independently and simultaneously.
4629 To enter non-stop mode, use this sequence of commands before you run
4630 or attach to your program:
4633 # Enable the async interface.
4636 # If using the CLI, pagination breaks non-stop.
4639 # Finally, turn it on!
4643 You can use these commands to manipulate the non-stop mode setting:
4646 @kindex set non-stop
4647 @item set non-stop on
4648 Enable selection of non-stop mode.
4649 @item set non-stop off
4650 Disable selection of non-stop mode.
4651 @kindex show non-stop
4653 Show the current non-stop enablement setting.
4656 Note these commands only reflect whether non-stop mode is enabled,
4657 not whether the currently-executing program is being run in non-stop mode.
4658 In particular, the @code{set non-stop} preference is only consulted when
4659 @value{GDBN} starts or connects to the target program, and it is generally
4660 not possible to switch modes once debugging has started. Furthermore,
4661 since not all targets support non-stop mode, even when you have enabled
4662 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4665 In non-stop mode, all execution commands apply only to the current thread
4666 by default. That is, @code{continue} only continues one thread.
4667 To continue all threads, issue @code{continue -a} or @code{c -a}.
4669 You can use @value{GDBN}'s background execution commands
4670 (@pxref{Background Execution}) to run some threads in the background
4671 while you continue to examine or step others from @value{GDBN}.
4672 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4673 always executed asynchronously in non-stop mode.
4675 Suspending execution is done with the @code{interrupt} command when
4676 running in the background, or @kbd{Ctrl-c} during foreground execution.
4677 In all-stop mode, this stops the whole process;
4678 but in non-stop mode the interrupt applies only to the current thread.
4679 To stop the whole program, use @code{interrupt -a}.
4681 Other execution commands do not currently support the @code{-a} option.
4683 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4684 that thread current, as it does in all-stop mode. This is because the
4685 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4686 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4687 changed to a different thread just as you entered a command to operate on the
4688 previously current thread.
4690 @node Background Execution
4691 @subsection Background Execution
4693 @cindex foreground execution
4694 @cindex background execution
4695 @cindex asynchronous execution
4696 @cindex execution, foreground, background and asynchronous
4698 @value{GDBN}'s execution commands have two variants: the normal
4699 foreground (synchronous) behavior, and a background
4700 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4701 the program to report that some thread has stopped before prompting for
4702 another command. In background execution, @value{GDBN} immediately gives
4703 a command prompt so that you can issue other commands while your program runs.
4705 To specify background execution, add a @code{&} to the command. For example,
4706 the background form of the @code{continue} command is @code{continue&}, or
4707 just @code{c&}. The execution commands that accept background execution
4713 @xref{Starting, , Starting your Program}.
4717 @xref{Attach, , Debugging an Already-running Process}.
4721 @xref{Continuing and Stepping, step}.
4725 @xref{Continuing and Stepping, stepi}.
4729 @xref{Continuing and Stepping, next}.
4733 @xref{Continuing and Stepping, continue}.
4737 @xref{Continuing and Stepping, finish}.
4741 @xref{Continuing and Stepping, until}.
4745 Background execution is especially useful in conjunction with non-stop
4746 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4747 However, you can also use these commands in the normal all-stop mode with
4748 the restriction that you cannot issue another execution command until the
4749 previous one finishes. Examples of commands that are valid in all-stop
4750 mode while the program is running include @code{help} and @code{info break}.
4752 You can interrupt your program while it is running in the background by
4753 using the @code{interrupt} command.
4760 Suspend execution of the running program. In all-stop mode,
4761 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4762 only the current thread. To stop the whole program in non-stop mode,
4763 use @code{interrupt -a}.
4766 You may need to explicitly enable async mode before you can use background
4767 execution commands, with the @code{set target-async 1} command. If the
4768 target doesn't support async mode, @value{GDBN} issues an error message
4769 if you attempt to use the background execution commands.
4771 @node Thread-Specific Breakpoints
4772 @subsection Thread-Specific Breakpoints
4774 When your program has multiple threads (@pxref{Threads,, Debugging
4775 Programs with Multiple Threads}), you can choose whether to set
4776 breakpoints on all threads, or on a particular thread.
4779 @cindex breakpoints and threads
4780 @cindex thread breakpoints
4781 @kindex break @dots{} thread @var{threadno}
4782 @item break @var{linespec} thread @var{threadno}
4783 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4784 @var{linespec} specifies source lines; there are several ways of
4785 writing them (@pxref{Specify Location}), but the effect is always to
4786 specify some source line.
4788 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4789 to specify that you only want @value{GDBN} to stop the program when a
4790 particular thread reaches this breakpoint. @var{threadno} is one of the
4791 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4792 column of the @samp{info threads} display.
4794 If you do not specify @samp{thread @var{threadno}} when you set a
4795 breakpoint, the breakpoint applies to @emph{all} threads of your
4798 You can use the @code{thread} qualifier on conditional breakpoints as
4799 well; in this case, place @samp{thread @var{threadno}} before the
4800 breakpoint condition, like this:
4803 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4808 @node Interrupted System Calls
4809 @subsection Interrupted System Calls
4811 @cindex thread breakpoints and system calls
4812 @cindex system calls and thread breakpoints
4813 @cindex premature return from system calls
4814 There is an unfortunate side effect when using @value{GDBN} to debug
4815 multi-threaded programs. If one thread stops for a
4816 breakpoint, or for some other reason, and another thread is blocked in a
4817 system call, then the system call may return prematurely. This is a
4818 consequence of the interaction between multiple threads and the signals
4819 that @value{GDBN} uses to implement breakpoints and other events that
4822 To handle this problem, your program should check the return value of
4823 each system call and react appropriately. This is good programming
4826 For example, do not write code like this:
4832 The call to @code{sleep} will return early if a different thread stops
4833 at a breakpoint or for some other reason.
4835 Instead, write this:
4840 unslept = sleep (unslept);
4843 A system call is allowed to return early, so the system is still
4844 conforming to its specification. But @value{GDBN} does cause your
4845 multi-threaded program to behave differently than it would without
4848 Also, @value{GDBN} uses internal breakpoints in the thread library to
4849 monitor certain events such as thread creation and thread destruction.
4850 When such an event happens, a system call in another thread may return
4851 prematurely, even though your program does not appear to stop.
4854 @node Reverse Execution
4855 @chapter Running programs backward
4856 @cindex reverse execution
4857 @cindex running programs backward
4859 When you are debugging a program, it is not unusual to realize that
4860 you have gone too far, and some event of interest has already happened.
4861 If the target environment supports it, @value{GDBN} can allow you to
4862 ``rewind'' the program by running it backward.
4864 A target environment that supports reverse execution should be able
4865 to ``undo'' the changes in machine state that have taken place as the
4866 program was executing normally. Variables, registers etc.@: should
4867 revert to their previous values. Obviously this requires a great
4868 deal of sophistication on the part of the target environment; not
4869 all target environments can support reverse execution.
4871 When a program is executed in reverse, the instructions that
4872 have most recently been executed are ``un-executed'', in reverse
4873 order. The program counter runs backward, following the previous
4874 thread of execution in reverse. As each instruction is ``un-executed'',
4875 the values of memory and/or registers that were changed by that
4876 instruction are reverted to their previous states. After executing
4877 a piece of source code in reverse, all side effects of that code
4878 should be ``undone'', and all variables should be returned to their
4879 prior values@footnote{
4880 Note that some side effects are easier to undo than others. For instance,
4881 memory and registers are relatively easy, but device I/O is hard. Some
4882 targets may be able undo things like device I/O, and some may not.
4884 The contract between @value{GDBN} and the reverse executing target
4885 requires only that the target do something reasonable when
4886 @value{GDBN} tells it to execute backwards, and then report the
4887 results back to @value{GDBN}. Whatever the target reports back to
4888 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4889 assumes that the memory and registers that the target reports are in a
4890 consistant state, but @value{GDBN} accepts whatever it is given.
4893 If you are debugging in a target environment that supports
4894 reverse execution, @value{GDBN} provides the following commands.
4897 @kindex reverse-continue
4898 @kindex rc @r{(@code{reverse-continue})}
4899 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4900 @itemx rc @r{[}@var{ignore-count}@r{]}
4901 Beginning at the point where your program last stopped, start executing
4902 in reverse. Reverse execution will stop for breakpoints and synchronous
4903 exceptions (signals), just like normal execution. Behavior of
4904 asynchronous signals depends on the target environment.
4906 @kindex reverse-step
4907 @kindex rs @r{(@code{step})}
4908 @item reverse-step @r{[}@var{count}@r{]}
4909 Run the program backward until control reaches the start of a
4910 different source line; then stop it, and return control to @value{GDBN}.
4912 Like the @code{step} command, @code{reverse-step} will only stop
4913 at the beginning of a source line. It ``un-executes'' the previously
4914 executed source line. If the previous source line included calls to
4915 debuggable functions, @code{reverse-step} will step (backward) into
4916 the called function, stopping at the beginning of the @emph{last}
4917 statement in the called function (typically a return statement).
4919 Also, as with the @code{step} command, if non-debuggable functions are
4920 called, @code{reverse-step} will run thru them backward without stopping.
4922 @kindex reverse-stepi
4923 @kindex rsi @r{(@code{reverse-stepi})}
4924 @item reverse-stepi @r{[}@var{count}@r{]}
4925 Reverse-execute one machine instruction. Note that the instruction
4926 to be reverse-executed is @emph{not} the one pointed to by the program
4927 counter, but the instruction executed prior to that one. For instance,
4928 if the last instruction was a jump, @code{reverse-stepi} will take you
4929 back from the destination of the jump to the jump instruction itself.
4931 @kindex reverse-next
4932 @kindex rn @r{(@code{reverse-next})}
4933 @item reverse-next @r{[}@var{count}@r{]}
4934 Run backward to the beginning of the previous line executed in
4935 the current (innermost) stack frame. If the line contains function
4936 calls, they will be ``un-executed'' without stopping. Starting from
4937 the first line of a function, @code{reverse-next} will take you back
4938 to the caller of that function, @emph{before} the function was called,
4939 just as the normal @code{next} command would take you from the last
4940 line of a function back to its return to its caller
4941 @footnote{Unles the code is too heavily optimized.}.
4943 @kindex reverse-nexti
4944 @kindex rni @r{(@code{reverse-nexti})}
4945 @item reverse-nexti @r{[}@var{count}@r{]}
4946 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4947 in reverse, except that called functions are ``un-executed'' atomically.
4948 That is, if the previously executed instruction was a return from
4949 another instruction, @code{reverse-nexti} will continue to execute
4950 in reverse until the call to that function (from the current stack
4953 @kindex reverse-finish
4954 @item reverse-finish
4955 Just as the @code{finish} command takes you to the point where the
4956 current function returns, @code{reverse-finish} takes you to the point
4957 where it was called. Instead of ending up at the end of the current
4958 function invocation, you end up at the beginning.
4960 @kindex set exec-direction
4961 @item set exec-direction
4962 Set the direction of target execution.
4963 @itemx set exec-direction reverse
4964 @cindex execute forward or backward in time
4965 @value{GDBN} will perform all execution commands in reverse, until the
4966 exec-direction mode is changed to ``forward''. Affected commands include
4967 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4968 command cannot be used in reverse mode.
4969 @item set exec-direction forward
4970 @value{GDBN} will perform all execution commands in the normal fashion.
4971 This is the default.
4976 @chapter Examining the Stack
4978 When your program has stopped, the first thing you need to know is where it
4979 stopped and how it got there.
4982 Each time your program performs a function call, information about the call
4984 That information includes the location of the call in your program,
4985 the arguments of the call,
4986 and the local variables of the function being called.
4987 The information is saved in a block of data called a @dfn{stack frame}.
4988 The stack frames are allocated in a region of memory called the @dfn{call
4991 When your program stops, the @value{GDBN} commands for examining the
4992 stack allow you to see all of this information.
4994 @cindex selected frame
4995 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4996 @value{GDBN} commands refer implicitly to the selected frame. In
4997 particular, whenever you ask @value{GDBN} for the value of a variable in
4998 your program, the value is found in the selected frame. There are
4999 special @value{GDBN} commands to select whichever frame you are
5000 interested in. @xref{Selection, ,Selecting a Frame}.
5002 When your program stops, @value{GDBN} automatically selects the
5003 currently executing frame and describes it briefly, similar to the
5004 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5007 * Frames:: Stack frames
5008 * Backtrace:: Backtraces
5009 * Selection:: Selecting a frame
5010 * Frame Info:: Information on a frame
5015 @section Stack Frames
5017 @cindex frame, definition
5019 The call stack is divided up into contiguous pieces called @dfn{stack
5020 frames}, or @dfn{frames} for short; each frame is the data associated
5021 with one call to one function. The frame contains the arguments given
5022 to the function, the function's local variables, and the address at
5023 which the function is executing.
5025 @cindex initial frame
5026 @cindex outermost frame
5027 @cindex innermost frame
5028 When your program is started, the stack has only one frame, that of the
5029 function @code{main}. This is called the @dfn{initial} frame or the
5030 @dfn{outermost} frame. Each time a function is called, a new frame is
5031 made. Each time a function returns, the frame for that function invocation
5032 is eliminated. If a function is recursive, there can be many frames for
5033 the same function. The frame for the function in which execution is
5034 actually occurring is called the @dfn{innermost} frame. This is the most
5035 recently created of all the stack frames that still exist.
5037 @cindex frame pointer
5038 Inside your program, stack frames are identified by their addresses. A
5039 stack frame consists of many bytes, each of which has its own address; each
5040 kind of computer has a convention for choosing one byte whose
5041 address serves as the address of the frame. Usually this address is kept
5042 in a register called the @dfn{frame pointer register}
5043 (@pxref{Registers, $fp}) while execution is going on in that frame.
5045 @cindex frame number
5046 @value{GDBN} assigns numbers to all existing stack frames, starting with
5047 zero for the innermost frame, one for the frame that called it,
5048 and so on upward. These numbers do not really exist in your program;
5049 they are assigned by @value{GDBN} to give you a way of designating stack
5050 frames in @value{GDBN} commands.
5052 @c The -fomit-frame-pointer below perennially causes hbox overflow
5053 @c underflow problems.
5054 @cindex frameless execution
5055 Some compilers provide a way to compile functions so that they operate
5056 without stack frames. (For example, the @value{NGCC} option
5058 @samp{-fomit-frame-pointer}
5060 generates functions without a frame.)
5061 This is occasionally done with heavily used library functions to save
5062 the frame setup time. @value{GDBN} has limited facilities for dealing
5063 with these function invocations. If the innermost function invocation
5064 has no stack frame, @value{GDBN} nevertheless regards it as though
5065 it had a separate frame, which is numbered zero as usual, allowing
5066 correct tracing of the function call chain. However, @value{GDBN} has
5067 no provision for frameless functions elsewhere in the stack.
5070 @kindex frame@r{, command}
5071 @cindex current stack frame
5072 @item frame @var{args}
5073 The @code{frame} command allows you to move from one stack frame to another,
5074 and to print the stack frame you select. @var{args} may be either the
5075 address of the frame or the stack frame number. Without an argument,
5076 @code{frame} prints the current stack frame.
5078 @kindex select-frame
5079 @cindex selecting frame silently
5081 The @code{select-frame} command allows you to move from one stack frame
5082 to another without printing the frame. This is the silent version of
5090 @cindex call stack traces
5091 A backtrace is a summary of how your program got where it is. It shows one
5092 line per frame, for many frames, starting with the currently executing
5093 frame (frame zero), followed by its caller (frame one), and on up the
5098 @kindex bt @r{(@code{backtrace})}
5101 Print a backtrace of the entire stack: one line per frame for all
5102 frames in the stack.
5104 You can stop the backtrace at any time by typing the system interrupt
5105 character, normally @kbd{Ctrl-c}.
5107 @item backtrace @var{n}
5109 Similar, but print only the innermost @var{n} frames.
5111 @item backtrace -@var{n}
5113 Similar, but print only the outermost @var{n} frames.
5115 @item backtrace full
5117 @itemx bt full @var{n}
5118 @itemx bt full -@var{n}
5119 Print the values of the local variables also. @var{n} specifies the
5120 number of frames to print, as described above.
5125 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5126 are additional aliases for @code{backtrace}.
5128 @cindex multiple threads, backtrace
5129 In a multi-threaded program, @value{GDBN} by default shows the
5130 backtrace only for the current thread. To display the backtrace for
5131 several or all of the threads, use the command @code{thread apply}
5132 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5133 apply all backtrace}, @value{GDBN} will display the backtrace for all
5134 the threads; this is handy when you debug a core dump of a
5135 multi-threaded program.
5137 Each line in the backtrace shows the frame number and the function name.
5138 The program counter value is also shown---unless you use @code{set
5139 print address off}. The backtrace also shows the source file name and
5140 line number, as well as the arguments to the function. The program
5141 counter value is omitted if it is at the beginning of the code for that
5144 Here is an example of a backtrace. It was made with the command
5145 @samp{bt 3}, so it shows the innermost three frames.
5149 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5151 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5152 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5154 (More stack frames follow...)
5159 The display for frame zero does not begin with a program counter
5160 value, indicating that your program has stopped at the beginning of the
5161 code for line @code{993} of @code{builtin.c}.
5163 @cindex value optimized out, in backtrace
5164 @cindex function call arguments, optimized out
5165 If your program was compiled with optimizations, some compilers will
5166 optimize away arguments passed to functions if those arguments are
5167 never used after the call. Such optimizations generate code that
5168 passes arguments through registers, but doesn't store those arguments
5169 in the stack frame. @value{GDBN} has no way of displaying such
5170 arguments in stack frames other than the innermost one. Here's what
5171 such a backtrace might look like:
5175 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5177 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5178 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5180 (More stack frames follow...)
5185 The values of arguments that were not saved in their stack frames are
5186 shown as @samp{<value optimized out>}.
5188 If you need to display the values of such optimized-out arguments,
5189 either deduce that from other variables whose values depend on the one
5190 you are interested in, or recompile without optimizations.
5192 @cindex backtrace beyond @code{main} function
5193 @cindex program entry point
5194 @cindex startup code, and backtrace
5195 Most programs have a standard user entry point---a place where system
5196 libraries and startup code transition into user code. For C this is
5197 @code{main}@footnote{
5198 Note that embedded programs (the so-called ``free-standing''
5199 environment) are not required to have a @code{main} function as the
5200 entry point. They could even have multiple entry points.}.
5201 When @value{GDBN} finds the entry function in a backtrace
5202 it will terminate the backtrace, to avoid tracing into highly
5203 system-specific (and generally uninteresting) code.
5205 If you need to examine the startup code, or limit the number of levels
5206 in a backtrace, you can change this behavior:
5209 @item set backtrace past-main
5210 @itemx set backtrace past-main on
5211 @kindex set backtrace
5212 Backtraces will continue past the user entry point.
5214 @item set backtrace past-main off
5215 Backtraces will stop when they encounter the user entry point. This is the
5218 @item show backtrace past-main
5219 @kindex show backtrace
5220 Display the current user entry point backtrace policy.
5222 @item set backtrace past-entry
5223 @itemx set backtrace past-entry on
5224 Backtraces will continue past the internal entry point of an application.
5225 This entry point is encoded by the linker when the application is built,
5226 and is likely before the user entry point @code{main} (or equivalent) is called.
5228 @item set backtrace past-entry off
5229 Backtraces will stop when they encounter the internal entry point of an
5230 application. This is the default.
5232 @item show backtrace past-entry
5233 Display the current internal entry point backtrace policy.
5235 @item set backtrace limit @var{n}
5236 @itemx set backtrace limit 0
5237 @cindex backtrace limit
5238 Limit the backtrace to @var{n} levels. A value of zero means
5241 @item show backtrace limit
5242 Display the current limit on backtrace levels.
5246 @section Selecting a Frame
5248 Most commands for examining the stack and other data in your program work on
5249 whichever stack frame is selected at the moment. Here are the commands for
5250 selecting a stack frame; all of them finish by printing a brief description
5251 of the stack frame just selected.
5254 @kindex frame@r{, selecting}
5255 @kindex f @r{(@code{frame})}
5258 Select frame number @var{n}. Recall that frame zero is the innermost
5259 (currently executing) frame, frame one is the frame that called the
5260 innermost one, and so on. The highest-numbered frame is the one for
5263 @item frame @var{addr}
5265 Select the frame at address @var{addr}. This is useful mainly if the
5266 chaining of stack frames has been damaged by a bug, making it
5267 impossible for @value{GDBN} to assign numbers properly to all frames. In
5268 addition, this can be useful when your program has multiple stacks and
5269 switches between them.
5271 On the SPARC architecture, @code{frame} needs two addresses to
5272 select an arbitrary frame: a frame pointer and a stack pointer.
5274 On the MIPS and Alpha architecture, it needs two addresses: a stack
5275 pointer and a program counter.
5277 On the 29k architecture, it needs three addresses: a register stack
5278 pointer, a program counter, and a memory stack pointer.
5282 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5283 advances toward the outermost frame, to higher frame numbers, to frames
5284 that have existed longer. @var{n} defaults to one.
5287 @kindex do @r{(@code{down})}
5289 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5290 advances toward the innermost frame, to lower frame numbers, to frames
5291 that were created more recently. @var{n} defaults to one. You may
5292 abbreviate @code{down} as @code{do}.
5295 All of these commands end by printing two lines of output describing the
5296 frame. The first line shows the frame number, the function name, the
5297 arguments, and the source file and line number of execution in that
5298 frame. The second line shows the text of that source line.
5306 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5308 10 read_input_file (argv[i]);
5312 After such a printout, the @code{list} command with no arguments
5313 prints ten lines centered on the point of execution in the frame.
5314 You can also edit the program at the point of execution with your favorite
5315 editing program by typing @code{edit}.
5316 @xref{List, ,Printing Source Lines},
5320 @kindex down-silently
5322 @item up-silently @var{n}
5323 @itemx down-silently @var{n}
5324 These two commands are variants of @code{up} and @code{down},
5325 respectively; they differ in that they do their work silently, without
5326 causing display of the new frame. They are intended primarily for use
5327 in @value{GDBN} command scripts, where the output might be unnecessary and
5332 @section Information About a Frame
5334 There are several other commands to print information about the selected
5340 When used without any argument, this command does not change which
5341 frame is selected, but prints a brief description of the currently
5342 selected stack frame. It can be abbreviated @code{f}. With an
5343 argument, this command is used to select a stack frame.
5344 @xref{Selection, ,Selecting a Frame}.
5347 @kindex info f @r{(@code{info frame})}
5350 This command prints a verbose description of the selected stack frame,
5355 the address of the frame
5357 the address of the next frame down (called by this frame)
5359 the address of the next frame up (caller of this frame)
5361 the language in which the source code corresponding to this frame is written
5363 the address of the frame's arguments
5365 the address of the frame's local variables
5367 the program counter saved in it (the address of execution in the caller frame)
5369 which registers were saved in the frame
5372 @noindent The verbose description is useful when
5373 something has gone wrong that has made the stack format fail to fit
5374 the usual conventions.
5376 @item info frame @var{addr}
5377 @itemx info f @var{addr}
5378 Print a verbose description of the frame at address @var{addr}, without
5379 selecting that frame. The selected frame remains unchanged by this
5380 command. This requires the same kind of address (more than one for some
5381 architectures) that you specify in the @code{frame} command.
5382 @xref{Selection, ,Selecting a Frame}.
5386 Print the arguments of the selected frame, each on a separate line.
5390 Print the local variables of the selected frame, each on a separate
5391 line. These are all variables (declared either static or automatic)
5392 accessible at the point of execution of the selected frame.
5395 @cindex catch exceptions, list active handlers
5396 @cindex exception handlers, how to list
5398 Print a list of all the exception handlers that are active in the
5399 current stack frame at the current point of execution. To see other
5400 exception handlers, visit the associated frame (using the @code{up},
5401 @code{down}, or @code{frame} commands); then type @code{info catch}.
5402 @xref{Set Catchpoints, , Setting Catchpoints}.
5408 @chapter Examining Source Files
5410 @value{GDBN} can print parts of your program's source, since the debugging
5411 information recorded in the program tells @value{GDBN} what source files were
5412 used to build it. When your program stops, @value{GDBN} spontaneously prints
5413 the line where it stopped. Likewise, when you select a stack frame
5414 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5415 execution in that frame has stopped. You can print other portions of
5416 source files by explicit command.
5418 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5419 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5420 @value{GDBN} under @sc{gnu} Emacs}.
5423 * List:: Printing source lines
5424 * Specify Location:: How to specify code locations
5425 * Edit:: Editing source files
5426 * Search:: Searching source files
5427 * Source Path:: Specifying source directories
5428 * Machine Code:: Source and machine code
5432 @section Printing Source Lines
5435 @kindex l @r{(@code{list})}
5436 To print lines from a source file, use the @code{list} command
5437 (abbreviated @code{l}). By default, ten lines are printed.
5438 There are several ways to specify what part of the file you want to
5439 print; see @ref{Specify Location}, for the full list.
5441 Here are the forms of the @code{list} command most commonly used:
5444 @item list @var{linenum}
5445 Print lines centered around line number @var{linenum} in the
5446 current source file.
5448 @item list @var{function}
5449 Print lines centered around the beginning of function
5453 Print more lines. If the last lines printed were printed with a
5454 @code{list} command, this prints lines following the last lines
5455 printed; however, if the last line printed was a solitary line printed
5456 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5457 Stack}), this prints lines centered around that line.
5460 Print lines just before the lines last printed.
5463 @cindex @code{list}, how many lines to display
5464 By default, @value{GDBN} prints ten source lines with any of these forms of
5465 the @code{list} command. You can change this using @code{set listsize}:
5468 @kindex set listsize
5469 @item set listsize @var{count}
5470 Make the @code{list} command display @var{count} source lines (unless
5471 the @code{list} argument explicitly specifies some other number).
5473 @kindex show listsize
5475 Display the number of lines that @code{list} prints.
5478 Repeating a @code{list} command with @key{RET} discards the argument,
5479 so it is equivalent to typing just @code{list}. This is more useful
5480 than listing the same lines again. An exception is made for an
5481 argument of @samp{-}; that argument is preserved in repetition so that
5482 each repetition moves up in the source file.
5484 In general, the @code{list} command expects you to supply zero, one or two
5485 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5486 of writing them (@pxref{Specify Location}), but the effect is always
5487 to specify some source line.
5489 Here is a complete description of the possible arguments for @code{list}:
5492 @item list @var{linespec}
5493 Print lines centered around the line specified by @var{linespec}.
5495 @item list @var{first},@var{last}
5496 Print lines from @var{first} to @var{last}. Both arguments are
5497 linespecs. When a @code{list} command has two linespecs, and the
5498 source file of the second linespec is omitted, this refers to
5499 the same source file as the first linespec.
5501 @item list ,@var{last}
5502 Print lines ending with @var{last}.
5504 @item list @var{first},
5505 Print lines starting with @var{first}.
5508 Print lines just after the lines last printed.
5511 Print lines just before the lines last printed.
5514 As described in the preceding table.
5517 @node Specify Location
5518 @section Specifying a Location
5519 @cindex specifying location
5522 Several @value{GDBN} commands accept arguments that specify a location
5523 of your program's code. Since @value{GDBN} is a source-level
5524 debugger, a location usually specifies some line in the source code;
5525 for that reason, locations are also known as @dfn{linespecs}.
5527 Here are all the different ways of specifying a code location that
5528 @value{GDBN} understands:
5532 Specifies the line number @var{linenum} of the current source file.
5535 @itemx +@var{offset}
5536 Specifies the line @var{offset} lines before or after the @dfn{current
5537 line}. For the @code{list} command, the current line is the last one
5538 printed; for the breakpoint commands, this is the line at which
5539 execution stopped in the currently selected @dfn{stack frame}
5540 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5541 used as the second of the two linespecs in a @code{list} command,
5542 this specifies the line @var{offset} lines up or down from the first
5545 @item @var{filename}:@var{linenum}
5546 Specifies the line @var{linenum} in the source file @var{filename}.
5548 @item @var{function}
5549 Specifies the line that begins the body of the function @var{function}.
5550 For example, in C, this is the line with the open brace.
5552 @item @var{filename}:@var{function}
5553 Specifies the line that begins the body of the function @var{function}
5554 in the file @var{filename}. You only need the file name with a
5555 function name to avoid ambiguity when there are identically named
5556 functions in different source files.
5558 @item *@var{address}
5559 Specifies the program address @var{address}. For line-oriented
5560 commands, such as @code{list} and @code{edit}, this specifies a source
5561 line that contains @var{address}. For @code{break} and other
5562 breakpoint oriented commands, this can be used to set breakpoints in
5563 parts of your program which do not have debugging information or
5566 Here @var{address} may be any expression valid in the current working
5567 language (@pxref{Languages, working language}) that specifies a code
5568 address. In addition, as a convenience, @value{GDBN} extends the
5569 semantics of expressions used in locations to cover the situations
5570 that frequently happen during debugging. Here are the various forms
5574 @item @var{expression}
5575 Any expression valid in the current working language.
5577 @item @var{funcaddr}
5578 An address of a function or procedure derived from its name. In C,
5579 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5580 simply the function's name @var{function} (and actually a special case
5581 of a valid expression). In Pascal and Modula-2, this is
5582 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5583 (although the Pascal form also works).
5585 This form specifies the address of the function's first instruction,
5586 before the stack frame and arguments have been set up.
5588 @item '@var{filename}'::@var{funcaddr}
5589 Like @var{funcaddr} above, but also specifies the name of the source
5590 file explicitly. This is useful if the name of the function does not
5591 specify the function unambiguously, e.g., if there are several
5592 functions with identical names in different source files.
5599 @section Editing Source Files
5600 @cindex editing source files
5603 @kindex e @r{(@code{edit})}
5604 To edit the lines in a source file, use the @code{edit} command.
5605 The editing program of your choice
5606 is invoked with the current line set to
5607 the active line in the program.
5608 Alternatively, there are several ways to specify what part of the file you
5609 want to print if you want to see other parts of the program:
5612 @item edit @var{location}
5613 Edit the source file specified by @code{location}. Editing starts at
5614 that @var{location}, e.g., at the specified source line of the
5615 specified file. @xref{Specify Location}, for all the possible forms
5616 of the @var{location} argument; here are the forms of the @code{edit}
5617 command most commonly used:
5620 @item edit @var{number}
5621 Edit the current source file with @var{number} as the active line number.
5623 @item edit @var{function}
5624 Edit the file containing @var{function} at the beginning of its definition.
5629 @subsection Choosing your Editor
5630 You can customize @value{GDBN} to use any editor you want
5632 The only restriction is that your editor (say @code{ex}), recognizes the
5633 following command-line syntax:
5635 ex +@var{number} file
5637 The optional numeric value +@var{number} specifies the number of the line in
5638 the file where to start editing.}.
5639 By default, it is @file{@value{EDITOR}}, but you can change this
5640 by setting the environment variable @code{EDITOR} before using
5641 @value{GDBN}. For example, to configure @value{GDBN} to use the
5642 @code{vi} editor, you could use these commands with the @code{sh} shell:
5648 or in the @code{csh} shell,
5650 setenv EDITOR /usr/bin/vi
5655 @section Searching Source Files
5656 @cindex searching source files
5658 There are two commands for searching through the current source file for a
5663 @kindex forward-search
5664 @item forward-search @var{regexp}
5665 @itemx search @var{regexp}
5666 The command @samp{forward-search @var{regexp}} checks each line,
5667 starting with the one following the last line listed, for a match for
5668 @var{regexp}. It lists the line that is found. You can use the
5669 synonym @samp{search @var{regexp}} or abbreviate the command name as
5672 @kindex reverse-search
5673 @item reverse-search @var{regexp}
5674 The command @samp{reverse-search @var{regexp}} checks each line, starting
5675 with the one before the last line listed and going backward, for a match
5676 for @var{regexp}. It lists the line that is found. You can abbreviate
5677 this command as @code{rev}.
5681 @section Specifying Source Directories
5684 @cindex directories for source files
5685 Executable programs sometimes do not record the directories of the source
5686 files from which they were compiled, just the names. Even when they do,
5687 the directories could be moved between the compilation and your debugging
5688 session. @value{GDBN} has a list of directories to search for source files;
5689 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5690 it tries all the directories in the list, in the order they are present
5691 in the list, until it finds a file with the desired name.
5693 For example, suppose an executable references the file
5694 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5695 @file{/mnt/cross}. The file is first looked up literally; if this
5696 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5697 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5698 message is printed. @value{GDBN} does not look up the parts of the
5699 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5700 Likewise, the subdirectories of the source path are not searched: if
5701 the source path is @file{/mnt/cross}, and the binary refers to
5702 @file{foo.c}, @value{GDBN} would not find it under
5703 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5705 Plain file names, relative file names with leading directories, file
5706 names containing dots, etc.@: are all treated as described above; for
5707 instance, if the source path is @file{/mnt/cross}, and the source file
5708 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5709 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5710 that---@file{/mnt/cross/foo.c}.
5712 Note that the executable search path is @emph{not} used to locate the
5715 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5716 any information it has cached about where source files are found and where
5717 each line is in the file.
5721 When you start @value{GDBN}, its source path includes only @samp{cdir}
5722 and @samp{cwd}, in that order.
5723 To add other directories, use the @code{directory} command.
5725 The search path is used to find both program source files and @value{GDBN}
5726 script files (read using the @samp{-command} option and @samp{source} command).
5728 In addition to the source path, @value{GDBN} provides a set of commands
5729 that manage a list of source path substitution rules. A @dfn{substitution
5730 rule} specifies how to rewrite source directories stored in the program's
5731 debug information in case the sources were moved to a different
5732 directory between compilation and debugging. A rule is made of
5733 two strings, the first specifying what needs to be rewritten in
5734 the path, and the second specifying how it should be rewritten.
5735 In @ref{set substitute-path}, we name these two parts @var{from} and
5736 @var{to} respectively. @value{GDBN} does a simple string replacement
5737 of @var{from} with @var{to} at the start of the directory part of the
5738 source file name, and uses that result instead of the original file
5739 name to look up the sources.
5741 Using the previous example, suppose the @file{foo-1.0} tree has been
5742 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5743 @value{GDBN} to replace @file{/usr/src} in all source path names with
5744 @file{/mnt/cross}. The first lookup will then be
5745 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5746 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5747 substitution rule, use the @code{set substitute-path} command
5748 (@pxref{set substitute-path}).
5750 To avoid unexpected substitution results, a rule is applied only if the
5751 @var{from} part of the directory name ends at a directory separator.
5752 For instance, a rule substituting @file{/usr/source} into
5753 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5754 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5755 is applied only at the beginning of the directory name, this rule will
5756 not be applied to @file{/root/usr/source/baz.c} either.
5758 In many cases, you can achieve the same result using the @code{directory}
5759 command. However, @code{set substitute-path} can be more efficient in
5760 the case where the sources are organized in a complex tree with multiple
5761 subdirectories. With the @code{directory} command, you need to add each
5762 subdirectory of your project. If you moved the entire tree while
5763 preserving its internal organization, then @code{set substitute-path}
5764 allows you to direct the debugger to all the sources with one single
5767 @code{set substitute-path} is also more than just a shortcut command.
5768 The source path is only used if the file at the original location no
5769 longer exists. On the other hand, @code{set substitute-path} modifies
5770 the debugger behavior to look at the rewritten location instead. So, if
5771 for any reason a source file that is not relevant to your executable is
5772 located at the original location, a substitution rule is the only
5773 method available to point @value{GDBN} at the new location.
5776 @item directory @var{dirname} @dots{}
5777 @item dir @var{dirname} @dots{}
5778 Add directory @var{dirname} to the front of the source path. Several
5779 directory names may be given to this command, separated by @samp{:}
5780 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5781 part of absolute file names) or
5782 whitespace. You may specify a directory that is already in the source
5783 path; this moves it forward, so @value{GDBN} searches it sooner.
5787 @vindex $cdir@r{, convenience variable}
5788 @vindex $cwd@r{, convenience variable}
5789 @cindex compilation directory
5790 @cindex current directory
5791 @cindex working directory
5792 @cindex directory, current
5793 @cindex directory, compilation
5794 You can use the string @samp{$cdir} to refer to the compilation
5795 directory (if one is recorded), and @samp{$cwd} to refer to the current
5796 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5797 tracks the current working directory as it changes during your @value{GDBN}
5798 session, while the latter is immediately expanded to the current
5799 directory at the time you add an entry to the source path.
5802 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5804 @c RET-repeat for @code{directory} is explicitly disabled, but since
5805 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5807 @item show directories
5808 @kindex show directories
5809 Print the source path: show which directories it contains.
5811 @anchor{set substitute-path}
5812 @item set substitute-path @var{from} @var{to}
5813 @kindex set substitute-path
5814 Define a source path substitution rule, and add it at the end of the
5815 current list of existing substitution rules. If a rule with the same
5816 @var{from} was already defined, then the old rule is also deleted.
5818 For example, if the file @file{/foo/bar/baz.c} was moved to
5819 @file{/mnt/cross/baz.c}, then the command
5822 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5826 will tell @value{GDBN} to replace @samp{/usr/src} with
5827 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5828 @file{baz.c} even though it was moved.
5830 In the case when more than one substitution rule have been defined,
5831 the rules are evaluated one by one in the order where they have been
5832 defined. The first one matching, if any, is selected to perform
5835 For instance, if we had entered the following commands:
5838 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5839 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5843 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5844 @file{/mnt/include/defs.h} by using the first rule. However, it would
5845 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5846 @file{/mnt/src/lib/foo.c}.
5849 @item unset substitute-path [path]
5850 @kindex unset substitute-path
5851 If a path is specified, search the current list of substitution rules
5852 for a rule that would rewrite that path. Delete that rule if found.
5853 A warning is emitted by the debugger if no rule could be found.
5855 If no path is specified, then all substitution rules are deleted.
5857 @item show substitute-path [path]
5858 @kindex show substitute-path
5859 If a path is specified, then print the source path substitution rule
5860 which would rewrite that path, if any.
5862 If no path is specified, then print all existing source path substitution
5867 If your source path is cluttered with directories that are no longer of
5868 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5869 versions of source. You can correct the situation as follows:
5873 Use @code{directory} with no argument to reset the source path to its default value.
5876 Use @code{directory} with suitable arguments to reinstall the
5877 directories you want in the source path. You can add all the
5878 directories in one command.
5882 @section Source and Machine Code
5883 @cindex source line and its code address
5885 You can use the command @code{info line} to map source lines to program
5886 addresses (and vice versa), and the command @code{disassemble} to display
5887 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5888 mode, the @code{info line} command causes the arrow to point to the
5889 line specified. Also, @code{info line} prints addresses in symbolic form as
5894 @item info line @var{linespec}
5895 Print the starting and ending addresses of the compiled code for
5896 source line @var{linespec}. You can specify source lines in any of
5897 the ways documented in @ref{Specify Location}.
5900 For example, we can use @code{info line} to discover the location of
5901 the object code for the first line of function
5902 @code{m4_changequote}:
5904 @c FIXME: I think this example should also show the addresses in
5905 @c symbolic form, as they usually would be displayed.
5907 (@value{GDBP}) info line m4_changequote
5908 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5912 @cindex code address and its source line
5913 We can also inquire (using @code{*@var{addr}} as the form for
5914 @var{linespec}) what source line covers a particular address:
5916 (@value{GDBP}) info line *0x63ff
5917 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5920 @cindex @code{$_} and @code{info line}
5921 @cindex @code{x} command, default address
5922 @kindex x@r{(examine), and} info line
5923 After @code{info line}, the default address for the @code{x} command
5924 is changed to the starting address of the line, so that @samp{x/i} is
5925 sufficient to begin examining the machine code (@pxref{Memory,
5926 ,Examining Memory}). Also, this address is saved as the value of the
5927 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5932 @cindex assembly instructions
5933 @cindex instructions, assembly
5934 @cindex machine instructions
5935 @cindex listing machine instructions
5937 @itemx disassemble /m
5938 This specialized command dumps a range of memory as machine
5939 instructions. It can also print mixed source+disassembly by specifying
5940 the @code{/m} modifier.
5941 The default memory range is the function surrounding the
5942 program counter of the selected frame. A single argument to this
5943 command is a program counter value; @value{GDBN} dumps the function
5944 surrounding this value. Two arguments specify a range of addresses
5945 (first inclusive, second exclusive) to dump.
5948 The following example shows the disassembly of a range of addresses of
5949 HP PA-RISC 2.0 code:
5952 (@value{GDBP}) disas 0x32c4 0x32e4
5953 Dump of assembler code from 0x32c4 to 0x32e4:
5954 0x32c4 <main+204>: addil 0,dp
5955 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5956 0x32cc <main+212>: ldil 0x3000,r31
5957 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5958 0x32d4 <main+220>: ldo 0(r31),rp
5959 0x32d8 <main+224>: addil -0x800,dp
5960 0x32dc <main+228>: ldo 0x588(r1),r26
5961 0x32e0 <main+232>: ldil 0x3000,r31
5962 End of assembler dump.
5965 Here is an example showing mixed source+assembly for Intel x86:
5968 (@value{GDBP}) disas /m main
5969 Dump of assembler code for function main:
5971 0x08048330 <main+0>: push %ebp
5972 0x08048331 <main+1>: mov %esp,%ebp
5973 0x08048333 <main+3>: sub $0x8,%esp
5974 0x08048336 <main+6>: and $0xfffffff0,%esp
5975 0x08048339 <main+9>: sub $0x10,%esp
5977 6 printf ("Hello.\n");
5978 0x0804833c <main+12>: movl $0x8048440,(%esp)
5979 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5983 0x08048348 <main+24>: mov $0x0,%eax
5984 0x0804834d <main+29>: leave
5985 0x0804834e <main+30>: ret
5987 End of assembler dump.
5990 Some architectures have more than one commonly-used set of instruction
5991 mnemonics or other syntax.
5993 For programs that were dynamically linked and use shared libraries,
5994 instructions that call functions or branch to locations in the shared
5995 libraries might show a seemingly bogus location---it's actually a
5996 location of the relocation table. On some architectures, @value{GDBN}
5997 might be able to resolve these to actual function names.
6000 @kindex set disassembly-flavor
6001 @cindex Intel disassembly flavor
6002 @cindex AT&T disassembly flavor
6003 @item set disassembly-flavor @var{instruction-set}
6004 Select the instruction set to use when disassembling the
6005 program via the @code{disassemble} or @code{x/i} commands.
6007 Currently this command is only defined for the Intel x86 family. You
6008 can set @var{instruction-set} to either @code{intel} or @code{att}.
6009 The default is @code{att}, the AT&T flavor used by default by Unix
6010 assemblers for x86-based targets.
6012 @kindex show disassembly-flavor
6013 @item show disassembly-flavor
6014 Show the current setting of the disassembly flavor.
6019 @chapter Examining Data
6021 @cindex printing data
6022 @cindex examining data
6025 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6026 @c document because it is nonstandard... Under Epoch it displays in a
6027 @c different window or something like that.
6028 The usual way to examine data in your program is with the @code{print}
6029 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6030 evaluates and prints the value of an expression of the language your
6031 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6032 Different Languages}).
6035 @item print @var{expr}
6036 @itemx print /@var{f} @var{expr}
6037 @var{expr} is an expression (in the source language). By default the
6038 value of @var{expr} is printed in a format appropriate to its data type;
6039 you can choose a different format by specifying @samp{/@var{f}}, where
6040 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6044 @itemx print /@var{f}
6045 @cindex reprint the last value
6046 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6047 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6048 conveniently inspect the same value in an alternative format.
6051 A more low-level way of examining data is with the @code{x} command.
6052 It examines data in memory at a specified address and prints it in a
6053 specified format. @xref{Memory, ,Examining Memory}.
6055 If you are interested in information about types, or about how the
6056 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6057 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6061 * Expressions:: Expressions
6062 * Ambiguous Expressions:: Ambiguous Expressions
6063 * Variables:: Program variables
6064 * Arrays:: Artificial arrays
6065 * Output Formats:: Output formats
6066 * Memory:: Examining memory
6067 * Auto Display:: Automatic display
6068 * Print Settings:: Print settings
6069 * Value History:: Value history
6070 * Convenience Vars:: Convenience variables
6071 * Registers:: Registers
6072 * Floating Point Hardware:: Floating point hardware
6073 * Vector Unit:: Vector Unit
6074 * OS Information:: Auxiliary data provided by operating system
6075 * Memory Region Attributes:: Memory region attributes
6076 * Dump/Restore Files:: Copy between memory and a file
6077 * Core File Generation:: Cause a program dump its core
6078 * Character Sets:: Debugging programs that use a different
6079 character set than GDB does
6080 * Caching Remote Data:: Data caching for remote targets
6081 * Searching Memory:: Searching memory for a sequence of bytes
6085 @section Expressions
6088 @code{print} and many other @value{GDBN} commands accept an expression and
6089 compute its value. Any kind of constant, variable or operator defined
6090 by the programming language you are using is valid in an expression in
6091 @value{GDBN}. This includes conditional expressions, function calls,
6092 casts, and string constants. It also includes preprocessor macros, if
6093 you compiled your program to include this information; see
6096 @cindex arrays in expressions
6097 @value{GDBN} supports array constants in expressions input by
6098 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6099 you can use the command @code{print @{1, 2, 3@}} to create an array
6100 of three integers. If you pass an array to a function or assign it
6101 to a program variable, @value{GDBN} copies the array to memory that
6102 is @code{malloc}ed in the target program.
6104 Because C is so widespread, most of the expressions shown in examples in
6105 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6106 Languages}, for information on how to use expressions in other
6109 In this section, we discuss operators that you can use in @value{GDBN}
6110 expressions regardless of your programming language.
6112 @cindex casts, in expressions
6113 Casts are supported in all languages, not just in C, because it is so
6114 useful to cast a number into a pointer in order to examine a structure
6115 at that address in memory.
6116 @c FIXME: casts supported---Mod2 true?
6118 @value{GDBN} supports these operators, in addition to those common
6119 to programming languages:
6123 @samp{@@} is a binary operator for treating parts of memory as arrays.
6124 @xref{Arrays, ,Artificial Arrays}, for more information.
6127 @samp{::} allows you to specify a variable in terms of the file or
6128 function where it is defined. @xref{Variables, ,Program Variables}.
6130 @cindex @{@var{type}@}
6131 @cindex type casting memory
6132 @cindex memory, viewing as typed object
6133 @cindex casts, to view memory
6134 @item @{@var{type}@} @var{addr}
6135 Refers to an object of type @var{type} stored at address @var{addr} in
6136 memory. @var{addr} may be any expression whose value is an integer or
6137 pointer (but parentheses are required around binary operators, just as in
6138 a cast). This construct is allowed regardless of what kind of data is
6139 normally supposed to reside at @var{addr}.
6142 @node Ambiguous Expressions
6143 @section Ambiguous Expressions
6144 @cindex ambiguous expressions
6146 Expressions can sometimes contain some ambiguous elements. For instance,
6147 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6148 a single function name to be defined several times, for application in
6149 different contexts. This is called @dfn{overloading}. Another example
6150 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6151 templates and is typically instantiated several times, resulting in
6152 the same function name being defined in different contexts.
6154 In some cases and depending on the language, it is possible to adjust
6155 the expression to remove the ambiguity. For instance in C@t{++}, you
6156 can specify the signature of the function you want to break on, as in
6157 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6158 qualified name of your function often makes the expression unambiguous
6161 When an ambiguity that needs to be resolved is detected, the debugger
6162 has the capability to display a menu of numbered choices for each
6163 possibility, and then waits for the selection with the prompt @samp{>}.
6164 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6165 aborts the current command. If the command in which the expression was
6166 used allows more than one choice to be selected, the next option in the
6167 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6170 For example, the following session excerpt shows an attempt to set a
6171 breakpoint at the overloaded symbol @code{String::after}.
6172 We choose three particular definitions of that function name:
6174 @c FIXME! This is likely to change to show arg type lists, at least
6177 (@value{GDBP}) b String::after
6180 [2] file:String.cc; line number:867
6181 [3] file:String.cc; line number:860
6182 [4] file:String.cc; line number:875
6183 [5] file:String.cc; line number:853
6184 [6] file:String.cc; line number:846
6185 [7] file:String.cc; line number:735
6187 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6188 Breakpoint 2 at 0xb344: file String.cc, line 875.
6189 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6190 Multiple breakpoints were set.
6191 Use the "delete" command to delete unwanted
6198 @kindex set multiple-symbols
6199 @item set multiple-symbols @var{mode}
6200 @cindex multiple-symbols menu
6202 This option allows you to adjust the debugger behavior when an expression
6205 By default, @var{mode} is set to @code{all}. If the command with which
6206 the expression is used allows more than one choice, then @value{GDBN}
6207 automatically selects all possible choices. For instance, inserting
6208 a breakpoint on a function using an ambiguous name results in a breakpoint
6209 inserted on each possible match. However, if a unique choice must be made,
6210 then @value{GDBN} uses the menu to help you disambiguate the expression.
6211 For instance, printing the address of an overloaded function will result
6212 in the use of the menu.
6214 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6215 when an ambiguity is detected.
6217 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6218 an error due to the ambiguity and the command is aborted.
6220 @kindex show multiple-symbols
6221 @item show multiple-symbols
6222 Show the current value of the @code{multiple-symbols} setting.
6226 @section Program Variables
6228 The most common kind of expression to use is the name of a variable
6231 Variables in expressions are understood in the selected stack frame
6232 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6236 global (or file-static)
6243 visible according to the scope rules of the
6244 programming language from the point of execution in that frame
6247 @noindent This means that in the function
6262 you can examine and use the variable @code{a} whenever your program is
6263 executing within the function @code{foo}, but you can only use or
6264 examine the variable @code{b} while your program is executing inside
6265 the block where @code{b} is declared.
6267 @cindex variable name conflict
6268 There is an exception: you can refer to a variable or function whose
6269 scope is a single source file even if the current execution point is not
6270 in this file. But it is possible to have more than one such variable or
6271 function with the same name (in different source files). If that
6272 happens, referring to that name has unpredictable effects. If you wish,
6273 you can specify a static variable in a particular function or file,
6274 using the colon-colon (@code{::}) notation:
6276 @cindex colon-colon, context for variables/functions
6278 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6279 @cindex @code{::}, context for variables/functions
6282 @var{file}::@var{variable}
6283 @var{function}::@var{variable}
6287 Here @var{file} or @var{function} is the name of the context for the
6288 static @var{variable}. In the case of file names, you can use quotes to
6289 make sure @value{GDBN} parses the file name as a single word---for example,
6290 to print a global value of @code{x} defined in @file{f2.c}:
6293 (@value{GDBP}) p 'f2.c'::x
6296 @cindex C@t{++} scope resolution
6297 This use of @samp{::} is very rarely in conflict with the very similar
6298 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6299 scope resolution operator in @value{GDBN} expressions.
6300 @c FIXME: Um, so what happens in one of those rare cases where it's in
6303 @cindex wrong values
6304 @cindex variable values, wrong
6305 @cindex function entry/exit, wrong values of variables
6306 @cindex optimized code, wrong values of variables
6308 @emph{Warning:} Occasionally, a local variable may appear to have the
6309 wrong value at certain points in a function---just after entry to a new
6310 scope, and just before exit.
6312 You may see this problem when you are stepping by machine instructions.
6313 This is because, on most machines, it takes more than one instruction to
6314 set up a stack frame (including local variable definitions); if you are
6315 stepping by machine instructions, variables may appear to have the wrong
6316 values until the stack frame is completely built. On exit, it usually
6317 also takes more than one machine instruction to destroy a stack frame;
6318 after you begin stepping through that group of instructions, local
6319 variable definitions may be gone.
6321 This may also happen when the compiler does significant optimizations.
6322 To be sure of always seeing accurate values, turn off all optimization
6325 @cindex ``No symbol "foo" in current context''
6326 Another possible effect of compiler optimizations is to optimize
6327 unused variables out of existence, or assign variables to registers (as
6328 opposed to memory addresses). Depending on the support for such cases
6329 offered by the debug info format used by the compiler, @value{GDBN}
6330 might not be able to display values for such local variables. If that
6331 happens, @value{GDBN} will print a message like this:
6334 No symbol "foo" in current context.
6337 To solve such problems, either recompile without optimizations, or use a
6338 different debug info format, if the compiler supports several such
6339 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6340 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6341 produces debug info in a format that is superior to formats such as
6342 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6343 an effective form for debug info. @xref{Debugging Options,,Options
6344 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6345 Compiler Collection (GCC)}.
6346 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6347 that are best suited to C@t{++} programs.
6349 If you ask to print an object whose contents are unknown to
6350 @value{GDBN}, e.g., because its data type is not completely specified
6351 by the debug information, @value{GDBN} will say @samp{<incomplete
6352 type>}. @xref{Symbols, incomplete type}, for more about this.
6354 Strings are identified as arrays of @code{char} values without specified
6355 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6356 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6357 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6358 defines literal string type @code{"char"} as @code{char} without a sign.
6363 signed char var1[] = "A";
6366 You get during debugging
6371 $2 = @{65 'A', 0 '\0'@}
6375 @section Artificial Arrays
6377 @cindex artificial array
6379 @kindex @@@r{, referencing memory as an array}
6380 It is often useful to print out several successive objects of the
6381 same type in memory; a section of an array, or an array of
6382 dynamically determined size for which only a pointer exists in the
6385 You can do this by referring to a contiguous span of memory as an
6386 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6387 operand of @samp{@@} should be the first element of the desired array
6388 and be an individual object. The right operand should be the desired length
6389 of the array. The result is an array value whose elements are all of
6390 the type of the left argument. The first element is actually the left
6391 argument; the second element comes from bytes of memory immediately
6392 following those that hold the first element, and so on. Here is an
6393 example. If a program says
6396 int *array = (int *) malloc (len * sizeof (int));
6400 you can print the contents of @code{array} with
6406 The left operand of @samp{@@} must reside in memory. Array values made
6407 with @samp{@@} in this way behave just like other arrays in terms of
6408 subscripting, and are coerced to pointers when used in expressions.
6409 Artificial arrays most often appear in expressions via the value history
6410 (@pxref{Value History, ,Value History}), after printing one out.
6412 Another way to create an artificial array is to use a cast.
6413 This re-interprets a value as if it were an array.
6414 The value need not be in memory:
6416 (@value{GDBP}) p/x (short[2])0x12345678
6417 $1 = @{0x1234, 0x5678@}
6420 As a convenience, if you leave the array length out (as in
6421 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6422 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6424 (@value{GDBP}) p/x (short[])0x12345678
6425 $2 = @{0x1234, 0x5678@}
6428 Sometimes the artificial array mechanism is not quite enough; in
6429 moderately complex data structures, the elements of interest may not
6430 actually be adjacent---for example, if you are interested in the values
6431 of pointers in an array. One useful work-around in this situation is
6432 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6433 Variables}) as a counter in an expression that prints the first
6434 interesting value, and then repeat that expression via @key{RET}. For
6435 instance, suppose you have an array @code{dtab} of pointers to
6436 structures, and you are interested in the values of a field @code{fv}
6437 in each structure. Here is an example of what you might type:
6447 @node Output Formats
6448 @section Output Formats
6450 @cindex formatted output
6451 @cindex output formats
6452 By default, @value{GDBN} prints a value according to its data type. Sometimes
6453 this is not what you want. For example, you might want to print a number
6454 in hex, or a pointer in decimal. Or you might want to view data in memory
6455 at a certain address as a character string or as an instruction. To do
6456 these things, specify an @dfn{output format} when you print a value.
6458 The simplest use of output formats is to say how to print a value
6459 already computed. This is done by starting the arguments of the
6460 @code{print} command with a slash and a format letter. The format
6461 letters supported are:
6465 Regard the bits of the value as an integer, and print the integer in
6469 Print as integer in signed decimal.
6472 Print as integer in unsigned decimal.
6475 Print as integer in octal.
6478 Print as integer in binary. The letter @samp{t} stands for ``two''.
6479 @footnote{@samp{b} cannot be used because these format letters are also
6480 used with the @code{x} command, where @samp{b} stands for ``byte'';
6481 see @ref{Memory,,Examining Memory}.}
6484 @cindex unknown address, locating
6485 @cindex locate address
6486 Print as an address, both absolute in hexadecimal and as an offset from
6487 the nearest preceding symbol. You can use this format used to discover
6488 where (in what function) an unknown address is located:
6491 (@value{GDBP}) p/a 0x54320
6492 $3 = 0x54320 <_initialize_vx+396>
6496 The command @code{info symbol 0x54320} yields similar results.
6497 @xref{Symbols, info symbol}.
6500 Regard as an integer and print it as a character constant. This
6501 prints both the numerical value and its character representation. The
6502 character representation is replaced with the octal escape @samp{\nnn}
6503 for characters outside the 7-bit @sc{ascii} range.
6505 Without this format, @value{GDBN} displays @code{char},
6506 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6507 constants. Single-byte members of vectors are displayed as integer
6511 Regard the bits of the value as a floating point number and print
6512 using typical floating point syntax.
6515 @cindex printing strings
6516 @cindex printing byte arrays
6517 Regard as a string, if possible. With this format, pointers to single-byte
6518 data are displayed as null-terminated strings and arrays of single-byte data
6519 are displayed as fixed-length strings. Other values are displayed in their
6522 Without this format, @value{GDBN} displays pointers to and arrays of
6523 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6524 strings. Single-byte members of a vector are displayed as an integer
6528 For example, to print the program counter in hex (@pxref{Registers}), type
6535 Note that no space is required before the slash; this is because command
6536 names in @value{GDBN} cannot contain a slash.
6538 To reprint the last value in the value history with a different format,
6539 you can use the @code{print} command with just a format and no
6540 expression. For example, @samp{p/x} reprints the last value in hex.
6543 @section Examining Memory
6545 You can use the command @code{x} (for ``examine'') to examine memory in
6546 any of several formats, independently of your program's data types.
6548 @cindex examining memory
6550 @kindex x @r{(examine memory)}
6551 @item x/@var{nfu} @var{addr}
6554 Use the @code{x} command to examine memory.
6557 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6558 much memory to display and how to format it; @var{addr} is an
6559 expression giving the address where you want to start displaying memory.
6560 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6561 Several commands set convenient defaults for @var{addr}.
6564 @item @var{n}, the repeat count
6565 The repeat count is a decimal integer; the default is 1. It specifies
6566 how much memory (counting by units @var{u}) to display.
6567 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6570 @item @var{f}, the display format
6571 The display format is one of the formats used by @code{print}
6572 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6573 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6574 The default is @samp{x} (hexadecimal) initially. The default changes
6575 each time you use either @code{x} or @code{print}.
6577 @item @var{u}, the unit size
6578 The unit size is any of
6584 Halfwords (two bytes).
6586 Words (four bytes). This is the initial default.
6588 Giant words (eight bytes).
6591 Each time you specify a unit size with @code{x}, that size becomes the
6592 default unit the next time you use @code{x}. (For the @samp{s} and
6593 @samp{i} formats, the unit size is ignored and is normally not written.)
6595 @item @var{addr}, starting display address
6596 @var{addr} is the address where you want @value{GDBN} to begin displaying
6597 memory. The expression need not have a pointer value (though it may);
6598 it is always interpreted as an integer address of a byte of memory.
6599 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6600 @var{addr} is usually just after the last address examined---but several
6601 other commands also set the default address: @code{info breakpoints} (to
6602 the address of the last breakpoint listed), @code{info line} (to the
6603 starting address of a line), and @code{print} (if you use it to display
6604 a value from memory).
6607 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6608 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6609 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6610 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6611 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6613 Since the letters indicating unit sizes are all distinct from the
6614 letters specifying output formats, you do not have to remember whether
6615 unit size or format comes first; either order works. The output
6616 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6617 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6619 Even though the unit size @var{u} is ignored for the formats @samp{s}
6620 and @samp{i}, you might still want to use a count @var{n}; for example,
6621 @samp{3i} specifies that you want to see three machine instructions,
6622 including any operands. For convenience, especially when used with
6623 the @code{display} command, the @samp{i} format also prints branch delay
6624 slot instructions, if any, beyond the count specified, which immediately
6625 follow the last instruction that is within the count. The command
6626 @code{disassemble} gives an alternative way of inspecting machine
6627 instructions; see @ref{Machine Code,,Source and Machine Code}.
6629 All the defaults for the arguments to @code{x} are designed to make it
6630 easy to continue scanning memory with minimal specifications each time
6631 you use @code{x}. For example, after you have inspected three machine
6632 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6633 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6634 the repeat count @var{n} is used again; the other arguments default as
6635 for successive uses of @code{x}.
6637 @cindex @code{$_}, @code{$__}, and value history
6638 The addresses and contents printed by the @code{x} command are not saved
6639 in the value history because there is often too much of them and they
6640 would get in the way. Instead, @value{GDBN} makes these values available for
6641 subsequent use in expressions as values of the convenience variables
6642 @code{$_} and @code{$__}. After an @code{x} command, the last address
6643 examined is available for use in expressions in the convenience variable
6644 @code{$_}. The contents of that address, as examined, are available in
6645 the convenience variable @code{$__}.
6647 If the @code{x} command has a repeat count, the address and contents saved
6648 are from the last memory unit printed; this is not the same as the last
6649 address printed if several units were printed on the last line of output.
6651 @cindex remote memory comparison
6652 @cindex verify remote memory image
6653 When you are debugging a program running on a remote target machine
6654 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6655 remote machine's memory against the executable file you downloaded to
6656 the target. The @code{compare-sections} command is provided for such
6660 @kindex compare-sections
6661 @item compare-sections @r{[}@var{section-name}@r{]}
6662 Compare the data of a loadable section @var{section-name} in the
6663 executable file of the program being debugged with the same section in
6664 the remote machine's memory, and report any mismatches. With no
6665 arguments, compares all loadable sections. This command's
6666 availability depends on the target's support for the @code{"qCRC"}
6671 @section Automatic Display
6672 @cindex automatic display
6673 @cindex display of expressions
6675 If you find that you want to print the value of an expression frequently
6676 (to see how it changes), you might want to add it to the @dfn{automatic
6677 display list} so that @value{GDBN} prints its value each time your program stops.
6678 Each expression added to the list is given a number to identify it;
6679 to remove an expression from the list, you specify that number.
6680 The automatic display looks like this:
6684 3: bar[5] = (struct hack *) 0x3804
6688 This display shows item numbers, expressions and their current values. As with
6689 displays you request manually using @code{x} or @code{print}, you can
6690 specify the output format you prefer; in fact, @code{display} decides
6691 whether to use @code{print} or @code{x} depending your format
6692 specification---it uses @code{x} if you specify either the @samp{i}
6693 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6697 @item display @var{expr}
6698 Add the expression @var{expr} to the list of expressions to display
6699 each time your program stops. @xref{Expressions, ,Expressions}.
6701 @code{display} does not repeat if you press @key{RET} again after using it.
6703 @item display/@var{fmt} @var{expr}
6704 For @var{fmt} specifying only a display format and not a size or
6705 count, add the expression @var{expr} to the auto-display list but
6706 arrange to display it each time in the specified format @var{fmt}.
6707 @xref{Output Formats,,Output Formats}.
6709 @item display/@var{fmt} @var{addr}
6710 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6711 number of units, add the expression @var{addr} as a memory address to
6712 be examined each time your program stops. Examining means in effect
6713 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6716 For example, @samp{display/i $pc} can be helpful, to see the machine
6717 instruction about to be executed each time execution stops (@samp{$pc}
6718 is a common name for the program counter; @pxref{Registers, ,Registers}).
6721 @kindex delete display
6723 @item undisplay @var{dnums}@dots{}
6724 @itemx delete display @var{dnums}@dots{}
6725 Remove item numbers @var{dnums} from the list of expressions to display.
6727 @code{undisplay} does not repeat if you press @key{RET} after using it.
6728 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6730 @kindex disable display
6731 @item disable display @var{dnums}@dots{}
6732 Disable the display of item numbers @var{dnums}. A disabled display
6733 item is not printed automatically, but is not forgotten. It may be
6734 enabled again later.
6736 @kindex enable display
6737 @item enable display @var{dnums}@dots{}
6738 Enable display of item numbers @var{dnums}. It becomes effective once
6739 again in auto display of its expression, until you specify otherwise.
6742 Display the current values of the expressions on the list, just as is
6743 done when your program stops.
6745 @kindex info display
6747 Print the list of expressions previously set up to display
6748 automatically, each one with its item number, but without showing the
6749 values. This includes disabled expressions, which are marked as such.
6750 It also includes expressions which would not be displayed right now
6751 because they refer to automatic variables not currently available.
6754 @cindex display disabled out of scope
6755 If a display expression refers to local variables, then it does not make
6756 sense outside the lexical context for which it was set up. Such an
6757 expression is disabled when execution enters a context where one of its
6758 variables is not defined. For example, if you give the command
6759 @code{display last_char} while inside a function with an argument
6760 @code{last_char}, @value{GDBN} displays this argument while your program
6761 continues to stop inside that function. When it stops elsewhere---where
6762 there is no variable @code{last_char}---the display is disabled
6763 automatically. The next time your program stops where @code{last_char}
6764 is meaningful, you can enable the display expression once again.
6766 @node Print Settings
6767 @section Print Settings
6769 @cindex format options
6770 @cindex print settings
6771 @value{GDBN} provides the following ways to control how arrays, structures,
6772 and symbols are printed.
6775 These settings are useful for debugging programs in any language:
6779 @item set print address
6780 @itemx set print address on
6781 @cindex print/don't print memory addresses
6782 @value{GDBN} prints memory addresses showing the location of stack
6783 traces, structure values, pointer values, breakpoints, and so forth,
6784 even when it also displays the contents of those addresses. The default
6785 is @code{on}. For example, this is what a stack frame display looks like with
6786 @code{set print address on}:
6791 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6793 530 if (lquote != def_lquote)
6797 @item set print address off
6798 Do not print addresses when displaying their contents. For example,
6799 this is the same stack frame displayed with @code{set print address off}:
6803 (@value{GDBP}) set print addr off
6805 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6806 530 if (lquote != def_lquote)
6810 You can use @samp{set print address off} to eliminate all machine
6811 dependent displays from the @value{GDBN} interface. For example, with
6812 @code{print address off}, you should get the same text for backtraces on
6813 all machines---whether or not they involve pointer arguments.
6816 @item show print address
6817 Show whether or not addresses are to be printed.
6820 When @value{GDBN} prints a symbolic address, it normally prints the
6821 closest earlier symbol plus an offset. If that symbol does not uniquely
6822 identify the address (for example, it is a name whose scope is a single
6823 source file), you may need to clarify. One way to do this is with
6824 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6825 you can set @value{GDBN} to print the source file and line number when
6826 it prints a symbolic address:
6829 @item set print symbol-filename on
6830 @cindex source file and line of a symbol
6831 @cindex symbol, source file and line
6832 Tell @value{GDBN} to print the source file name and line number of a
6833 symbol in the symbolic form of an address.
6835 @item set print symbol-filename off
6836 Do not print source file name and line number of a symbol. This is the
6839 @item show print symbol-filename
6840 Show whether or not @value{GDBN} will print the source file name and
6841 line number of a symbol in the symbolic form of an address.
6844 Another situation where it is helpful to show symbol filenames and line
6845 numbers is when disassembling code; @value{GDBN} shows you the line
6846 number and source file that corresponds to each instruction.
6848 Also, you may wish to see the symbolic form only if the address being
6849 printed is reasonably close to the closest earlier symbol:
6852 @item set print max-symbolic-offset @var{max-offset}
6853 @cindex maximum value for offset of closest symbol
6854 Tell @value{GDBN} to only display the symbolic form of an address if the
6855 offset between the closest earlier symbol and the address is less than
6856 @var{max-offset}. The default is 0, which tells @value{GDBN}
6857 to always print the symbolic form of an address if any symbol precedes it.
6859 @item show print max-symbolic-offset
6860 Ask how large the maximum offset is that @value{GDBN} prints in a
6864 @cindex wild pointer, interpreting
6865 @cindex pointer, finding referent
6866 If you have a pointer and you are not sure where it points, try
6867 @samp{set print symbol-filename on}. Then you can determine the name
6868 and source file location of the variable where it points, using
6869 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6870 For example, here @value{GDBN} shows that a variable @code{ptt} points
6871 at another variable @code{t}, defined in @file{hi2.c}:
6874 (@value{GDBP}) set print symbol-filename on
6875 (@value{GDBP}) p/a ptt
6876 $4 = 0xe008 <t in hi2.c>
6880 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6881 does not show the symbol name and filename of the referent, even with
6882 the appropriate @code{set print} options turned on.
6885 Other settings control how different kinds of objects are printed:
6888 @item set print array
6889 @itemx set print array on
6890 @cindex pretty print arrays
6891 Pretty print arrays. This format is more convenient to read,
6892 but uses more space. The default is off.
6894 @item set print array off
6895 Return to compressed format for arrays.
6897 @item show print array
6898 Show whether compressed or pretty format is selected for displaying
6901 @cindex print array indexes
6902 @item set print array-indexes
6903 @itemx set print array-indexes on
6904 Print the index of each element when displaying arrays. May be more
6905 convenient to locate a given element in the array or quickly find the
6906 index of a given element in that printed array. The default is off.
6908 @item set print array-indexes off
6909 Stop printing element indexes when displaying arrays.
6911 @item show print array-indexes
6912 Show whether the index of each element is printed when displaying
6915 @item set print elements @var{number-of-elements}
6916 @cindex number of array elements to print
6917 @cindex limit on number of printed array elements
6918 Set a limit on how many elements of an array @value{GDBN} will print.
6919 If @value{GDBN} is printing a large array, it stops printing after it has
6920 printed the number of elements set by the @code{set print elements} command.
6921 This limit also applies to the display of strings.
6922 When @value{GDBN} starts, this limit is set to 200.
6923 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6925 @item show print elements
6926 Display the number of elements of a large array that @value{GDBN} will print.
6927 If the number is 0, then the printing is unlimited.
6929 @item set print frame-arguments @var{value}
6930 @cindex printing frame argument values
6931 @cindex print all frame argument values
6932 @cindex print frame argument values for scalars only
6933 @cindex do not print frame argument values
6934 This command allows to control how the values of arguments are printed
6935 when the debugger prints a frame (@pxref{Frames}). The possible
6940 The values of all arguments are printed. This is the default.
6943 Print the value of an argument only if it is a scalar. The value of more
6944 complex arguments such as arrays, structures, unions, etc, is replaced
6945 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6948 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6953 None of the argument values are printed. Instead, the value of each argument
6954 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6957 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6962 By default, all argument values are always printed. But this command
6963 can be useful in several cases. For instance, it can be used to reduce
6964 the amount of information printed in each frame, making the backtrace
6965 more readable. Also, this command can be used to improve performance
6966 when displaying Ada frames, because the computation of large arguments
6967 can sometimes be CPU-intensive, especiallly in large applications.
6968 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6969 avoids this computation, thus speeding up the display of each Ada frame.
6971 @item show print frame-arguments
6972 Show how the value of arguments should be displayed when printing a frame.
6974 @item set print repeats
6975 @cindex repeated array elements
6976 Set the threshold for suppressing display of repeated array
6977 elements. When the number of consecutive identical elements of an
6978 array exceeds the threshold, @value{GDBN} prints the string
6979 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6980 identical repetitions, instead of displaying the identical elements
6981 themselves. Setting the threshold to zero will cause all elements to
6982 be individually printed. The default threshold is 10.
6984 @item show print repeats
6985 Display the current threshold for printing repeated identical
6988 @item set print null-stop
6989 @cindex @sc{null} elements in arrays
6990 Cause @value{GDBN} to stop printing the characters of an array when the first
6991 @sc{null} is encountered. This is useful when large arrays actually
6992 contain only short strings.
6995 @item show print null-stop
6996 Show whether @value{GDBN} stops printing an array on the first
6997 @sc{null} character.
6999 @item set print pretty on
7000 @cindex print structures in indented form
7001 @cindex indentation in structure display
7002 Cause @value{GDBN} to print structures in an indented format with one member
7003 per line, like this:
7018 @item set print pretty off
7019 Cause @value{GDBN} to print structures in a compact format, like this:
7023 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7024 meat = 0x54 "Pork"@}
7029 This is the default format.
7031 @item show print pretty
7032 Show which format @value{GDBN} is using to print structures.
7034 @item set print sevenbit-strings on
7035 @cindex eight-bit characters in strings
7036 @cindex octal escapes in strings
7037 Print using only seven-bit characters; if this option is set,
7038 @value{GDBN} displays any eight-bit characters (in strings or
7039 character values) using the notation @code{\}@var{nnn}. This setting is
7040 best if you are working in English (@sc{ascii}) and you use the
7041 high-order bit of characters as a marker or ``meta'' bit.
7043 @item set print sevenbit-strings off
7044 Print full eight-bit characters. This allows the use of more
7045 international character sets, and is the default.
7047 @item show print sevenbit-strings
7048 Show whether or not @value{GDBN} is printing only seven-bit characters.
7050 @item set print union on
7051 @cindex unions in structures, printing
7052 Tell @value{GDBN} to print unions which are contained in structures
7053 and other unions. This is the default setting.
7055 @item set print union off
7056 Tell @value{GDBN} not to print unions which are contained in
7057 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7060 @item show print union
7061 Ask @value{GDBN} whether or not it will print unions which are contained in
7062 structures and other unions.
7064 For example, given the declarations
7067 typedef enum @{Tree, Bug@} Species;
7068 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7069 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7080 struct thing foo = @{Tree, @{Acorn@}@};
7084 with @code{set print union on} in effect @samp{p foo} would print
7087 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7091 and with @code{set print union off} in effect it would print
7094 $1 = @{it = Tree, form = @{...@}@}
7098 @code{set print union} affects programs written in C-like languages
7104 These settings are of interest when debugging C@t{++} programs:
7107 @cindex demangling C@t{++} names
7108 @item set print demangle
7109 @itemx set print demangle on
7110 Print C@t{++} names in their source form rather than in the encoded
7111 (``mangled'') form passed to the assembler and linker for type-safe
7112 linkage. The default is on.
7114 @item show print demangle
7115 Show whether C@t{++} names are printed in mangled or demangled form.
7117 @item set print asm-demangle
7118 @itemx set print asm-demangle on
7119 Print C@t{++} names in their source form rather than their mangled form, even
7120 in assembler code printouts such as instruction disassemblies.
7123 @item show print asm-demangle
7124 Show whether C@t{++} names in assembly listings are printed in mangled
7127 @cindex C@t{++} symbol decoding style
7128 @cindex symbol decoding style, C@t{++}
7129 @kindex set demangle-style
7130 @item set demangle-style @var{style}
7131 Choose among several encoding schemes used by different compilers to
7132 represent C@t{++} names. The choices for @var{style} are currently:
7136 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7139 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7140 This is the default.
7143 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7146 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7149 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7150 @strong{Warning:} this setting alone is not sufficient to allow
7151 debugging @code{cfront}-generated executables. @value{GDBN} would
7152 require further enhancement to permit that.
7155 If you omit @var{style}, you will see a list of possible formats.
7157 @item show demangle-style
7158 Display the encoding style currently in use for decoding C@t{++} symbols.
7160 @item set print object
7161 @itemx set print object on
7162 @cindex derived type of an object, printing
7163 @cindex display derived types
7164 When displaying a pointer to an object, identify the @emph{actual}
7165 (derived) type of the object rather than the @emph{declared} type, using
7166 the virtual function table.
7168 @item set print object off
7169 Display only the declared type of objects, without reference to the
7170 virtual function table. This is the default setting.
7172 @item show print object
7173 Show whether actual, or declared, object types are displayed.
7175 @item set print static-members
7176 @itemx set print static-members on
7177 @cindex static members of C@t{++} objects
7178 Print static members when displaying a C@t{++} object. The default is on.
7180 @item set print static-members off
7181 Do not print static members when displaying a C@t{++} object.
7183 @item show print static-members
7184 Show whether C@t{++} static members are printed or not.
7186 @item set print pascal_static-members
7187 @itemx set print pascal_static-members on
7188 @cindex static members of Pascal objects
7189 @cindex Pascal objects, static members display
7190 Print static members when displaying a Pascal object. The default is on.
7192 @item set print pascal_static-members off
7193 Do not print static members when displaying a Pascal object.
7195 @item show print pascal_static-members
7196 Show whether Pascal static members are printed or not.
7198 @c These don't work with HP ANSI C++ yet.
7199 @item set print vtbl
7200 @itemx set print vtbl on
7201 @cindex pretty print C@t{++} virtual function tables
7202 @cindex virtual functions (C@t{++}) display
7203 @cindex VTBL display
7204 Pretty print C@t{++} virtual function tables. The default is off.
7205 (The @code{vtbl} commands do not work on programs compiled with the HP
7206 ANSI C@t{++} compiler (@code{aCC}).)
7208 @item set print vtbl off
7209 Do not pretty print C@t{++} virtual function tables.
7211 @item show print vtbl
7212 Show whether C@t{++} virtual function tables are pretty printed, or not.
7216 @section Value History
7218 @cindex value history
7219 @cindex history of values printed by @value{GDBN}
7220 Values printed by the @code{print} command are saved in the @value{GDBN}
7221 @dfn{value history}. This allows you to refer to them in other expressions.
7222 Values are kept until the symbol table is re-read or discarded
7223 (for example with the @code{file} or @code{symbol-file} commands).
7224 When the symbol table changes, the value history is discarded,
7225 since the values may contain pointers back to the types defined in the
7230 @cindex history number
7231 The values printed are given @dfn{history numbers} by which you can
7232 refer to them. These are successive integers starting with one.
7233 @code{print} shows you the history number assigned to a value by
7234 printing @samp{$@var{num} = } before the value; here @var{num} is the
7237 To refer to any previous value, use @samp{$} followed by the value's
7238 history number. The way @code{print} labels its output is designed to
7239 remind you of this. Just @code{$} refers to the most recent value in
7240 the history, and @code{$$} refers to the value before that.
7241 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7242 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7243 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7245 For example, suppose you have just printed a pointer to a structure and
7246 want to see the contents of the structure. It suffices to type
7252 If you have a chain of structures where the component @code{next} points
7253 to the next one, you can print the contents of the next one with this:
7260 You can print successive links in the chain by repeating this
7261 command---which you can do by just typing @key{RET}.
7263 Note that the history records values, not expressions. If the value of
7264 @code{x} is 4 and you type these commands:
7272 then the value recorded in the value history by the @code{print} command
7273 remains 4 even though the value of @code{x} has changed.
7278 Print the last ten values in the value history, with their item numbers.
7279 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7280 values} does not change the history.
7282 @item show values @var{n}
7283 Print ten history values centered on history item number @var{n}.
7286 Print ten history values just after the values last printed. If no more
7287 values are available, @code{show values +} produces no display.
7290 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7291 same effect as @samp{show values +}.
7293 @node Convenience Vars
7294 @section Convenience Variables
7296 @cindex convenience variables
7297 @cindex user-defined variables
7298 @value{GDBN} provides @dfn{convenience variables} that you can use within
7299 @value{GDBN} to hold on to a value and refer to it later. These variables
7300 exist entirely within @value{GDBN}; they are not part of your program, and
7301 setting a convenience variable has no direct effect on further execution
7302 of your program. That is why you can use them freely.
7304 Convenience variables are prefixed with @samp{$}. Any name preceded by
7305 @samp{$} can be used for a convenience variable, unless it is one of
7306 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7307 (Value history references, in contrast, are @emph{numbers} preceded
7308 by @samp{$}. @xref{Value History, ,Value History}.)
7310 You can save a value in a convenience variable with an assignment
7311 expression, just as you would set a variable in your program.
7315 set $foo = *object_ptr
7319 would save in @code{$foo} the value contained in the object pointed to by
7322 Using a convenience variable for the first time creates it, but its
7323 value is @code{void} until you assign a new value. You can alter the
7324 value with another assignment at any time.
7326 Convenience variables have no fixed types. You can assign a convenience
7327 variable any type of value, including structures and arrays, even if
7328 that variable already has a value of a different type. The convenience
7329 variable, when used as an expression, has the type of its current value.
7332 @kindex show convenience
7333 @cindex show all user variables
7334 @item show convenience
7335 Print a list of convenience variables used so far, and their values.
7336 Abbreviated @code{show conv}.
7338 @kindex init-if-undefined
7339 @cindex convenience variables, initializing
7340 @item init-if-undefined $@var{variable} = @var{expression}
7341 Set a convenience variable if it has not already been set. This is useful
7342 for user-defined commands that keep some state. It is similar, in concept,
7343 to using local static variables with initializers in C (except that
7344 convenience variables are global). It can also be used to allow users to
7345 override default values used in a command script.
7347 If the variable is already defined then the expression is not evaluated so
7348 any side-effects do not occur.
7351 One of the ways to use a convenience variable is as a counter to be
7352 incremented or a pointer to be advanced. For example, to print
7353 a field from successive elements of an array of structures:
7357 print bar[$i++]->contents
7361 Repeat that command by typing @key{RET}.
7363 Some convenience variables are created automatically by @value{GDBN} and given
7364 values likely to be useful.
7367 @vindex $_@r{, convenience variable}
7369 The variable @code{$_} is automatically set by the @code{x} command to
7370 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7371 commands which provide a default address for @code{x} to examine also
7372 set @code{$_} to that address; these commands include @code{info line}
7373 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7374 except when set by the @code{x} command, in which case it is a pointer
7375 to the type of @code{$__}.
7377 @vindex $__@r{, convenience variable}
7379 The variable @code{$__} is automatically set by the @code{x} command
7380 to the value found in the last address examined. Its type is chosen
7381 to match the format in which the data was printed.
7384 @vindex $_exitcode@r{, convenience variable}
7385 The variable @code{$_exitcode} is automatically set to the exit code when
7386 the program being debugged terminates.
7389 On HP-UX systems, if you refer to a function or variable name that
7390 begins with a dollar sign, @value{GDBN} searches for a user or system
7391 name first, before it searches for a convenience variable.
7397 You can refer to machine register contents, in expressions, as variables
7398 with names starting with @samp{$}. The names of registers are different
7399 for each machine; use @code{info registers} to see the names used on
7403 @kindex info registers
7404 @item info registers
7405 Print the names and values of all registers except floating-point
7406 and vector registers (in the selected stack frame).
7408 @kindex info all-registers
7409 @cindex floating point registers
7410 @item info all-registers
7411 Print the names and values of all registers, including floating-point
7412 and vector registers (in the selected stack frame).
7414 @item info registers @var{regname} @dots{}
7415 Print the @dfn{relativized} value of each specified register @var{regname}.
7416 As discussed in detail below, register values are normally relative to
7417 the selected stack frame. @var{regname} may be any register name valid on
7418 the machine you are using, with or without the initial @samp{$}.
7421 @cindex stack pointer register
7422 @cindex program counter register
7423 @cindex process status register
7424 @cindex frame pointer register
7425 @cindex standard registers
7426 @value{GDBN} has four ``standard'' register names that are available (in
7427 expressions) on most machines---whenever they do not conflict with an
7428 architecture's canonical mnemonics for registers. The register names
7429 @code{$pc} and @code{$sp} are used for the program counter register and
7430 the stack pointer. @code{$fp} is used for a register that contains a
7431 pointer to the current stack frame, and @code{$ps} is used for a
7432 register that contains the processor status. For example,
7433 you could print the program counter in hex with
7440 or print the instruction to be executed next with
7447 or add four to the stack pointer@footnote{This is a way of removing
7448 one word from the stack, on machines where stacks grow downward in
7449 memory (most machines, nowadays). This assumes that the innermost
7450 stack frame is selected; setting @code{$sp} is not allowed when other
7451 stack frames are selected. To pop entire frames off the stack,
7452 regardless of machine architecture, use @code{return};
7453 see @ref{Returning, ,Returning from a Function}.} with
7459 Whenever possible, these four standard register names are available on
7460 your machine even though the machine has different canonical mnemonics,
7461 so long as there is no conflict. The @code{info registers} command
7462 shows the canonical names. For example, on the SPARC, @code{info
7463 registers} displays the processor status register as @code{$psr} but you
7464 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7465 is an alias for the @sc{eflags} register.
7467 @value{GDBN} always considers the contents of an ordinary register as an
7468 integer when the register is examined in this way. Some machines have
7469 special registers which can hold nothing but floating point; these
7470 registers are considered to have floating point values. There is no way
7471 to refer to the contents of an ordinary register as floating point value
7472 (although you can @emph{print} it as a floating point value with
7473 @samp{print/f $@var{regname}}).
7475 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7476 means that the data format in which the register contents are saved by
7477 the operating system is not the same one that your program normally
7478 sees. For example, the registers of the 68881 floating point
7479 coprocessor are always saved in ``extended'' (raw) format, but all C
7480 programs expect to work with ``double'' (virtual) format. In such
7481 cases, @value{GDBN} normally works with the virtual format only (the format
7482 that makes sense for your program), but the @code{info registers} command
7483 prints the data in both formats.
7485 @cindex SSE registers (x86)
7486 @cindex MMX registers (x86)
7487 Some machines have special registers whose contents can be interpreted
7488 in several different ways. For example, modern x86-based machines
7489 have SSE and MMX registers that can hold several values packed
7490 together in several different formats. @value{GDBN} refers to such
7491 registers in @code{struct} notation:
7494 (@value{GDBP}) print $xmm1
7496 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7497 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7498 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7499 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7500 v4_int32 = @{0, 20657912, 11, 13@},
7501 v2_int64 = @{88725056443645952, 55834574859@},
7502 uint128 = 0x0000000d0000000b013b36f800000000
7507 To set values of such registers, you need to tell @value{GDBN} which
7508 view of the register you wish to change, as if you were assigning
7509 value to a @code{struct} member:
7512 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7515 Normally, register values are relative to the selected stack frame
7516 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7517 value that the register would contain if all stack frames farther in
7518 were exited and their saved registers restored. In order to see the
7519 true contents of hardware registers, you must select the innermost
7520 frame (with @samp{frame 0}).
7522 However, @value{GDBN} must deduce where registers are saved, from the machine
7523 code generated by your compiler. If some registers are not saved, or if
7524 @value{GDBN} is unable to locate the saved registers, the selected stack
7525 frame makes no difference.
7527 @node Floating Point Hardware
7528 @section Floating Point Hardware
7529 @cindex floating point
7531 Depending on the configuration, @value{GDBN} may be able to give
7532 you more information about the status of the floating point hardware.
7537 Display hardware-dependent information about the floating
7538 point unit. The exact contents and layout vary depending on the
7539 floating point chip. Currently, @samp{info float} is supported on
7540 the ARM and x86 machines.
7544 @section Vector Unit
7547 Depending on the configuration, @value{GDBN} may be able to give you
7548 more information about the status of the vector unit.
7553 Display information about the vector unit. The exact contents and
7554 layout vary depending on the hardware.
7557 @node OS Information
7558 @section Operating System Auxiliary Information
7559 @cindex OS information
7561 @value{GDBN} provides interfaces to useful OS facilities that can help
7562 you debug your program.
7564 @cindex @code{ptrace} system call
7565 @cindex @code{struct user} contents
7566 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7567 machines), it interfaces with the inferior via the @code{ptrace}
7568 system call. The operating system creates a special sata structure,
7569 called @code{struct user}, for this interface. You can use the
7570 command @code{info udot} to display the contents of this data
7576 Display the contents of the @code{struct user} maintained by the OS
7577 kernel for the program being debugged. @value{GDBN} displays the
7578 contents of @code{struct user} as a list of hex numbers, similar to
7579 the @code{examine} command.
7582 @cindex auxiliary vector
7583 @cindex vector, auxiliary
7584 Some operating systems supply an @dfn{auxiliary vector} to programs at
7585 startup. This is akin to the arguments and environment that you
7586 specify for a program, but contains a system-dependent variety of
7587 binary values that tell system libraries important details about the
7588 hardware, operating system, and process. Each value's purpose is
7589 identified by an integer tag; the meanings are well-known but system-specific.
7590 Depending on the configuration and operating system facilities,
7591 @value{GDBN} may be able to show you this information. For remote
7592 targets, this functionality may further depend on the remote stub's
7593 support of the @samp{qXfer:auxv:read} packet, see
7594 @ref{qXfer auxiliary vector read}.
7599 Display the auxiliary vector of the inferior, which can be either a
7600 live process or a core dump file. @value{GDBN} prints each tag value
7601 numerically, and also shows names and text descriptions for recognized
7602 tags. Some values in the vector are numbers, some bit masks, and some
7603 pointers to strings or other data. @value{GDBN} displays each value in the
7604 most appropriate form for a recognized tag, and in hexadecimal for
7605 an unrecognized tag.
7609 @node Memory Region Attributes
7610 @section Memory Region Attributes
7611 @cindex memory region attributes
7613 @dfn{Memory region attributes} allow you to describe special handling
7614 required by regions of your target's memory. @value{GDBN} uses
7615 attributes to determine whether to allow certain types of memory
7616 accesses; whether to use specific width accesses; and whether to cache
7617 target memory. By default the description of memory regions is
7618 fetched from the target (if the current target supports this), but the
7619 user can override the fetched regions.
7621 Defined memory regions can be individually enabled and disabled. When a
7622 memory region is disabled, @value{GDBN} uses the default attributes when
7623 accessing memory in that region. Similarly, if no memory regions have
7624 been defined, @value{GDBN} uses the default attributes when accessing
7627 When a memory region is defined, it is given a number to identify it;
7628 to enable, disable, or remove a memory region, you specify that number.
7632 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7633 Define a memory region bounded by @var{lower} and @var{upper} with
7634 attributes @var{attributes}@dots{}, and add it to the list of regions
7635 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7636 case: it is treated as the target's maximum memory address.
7637 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7640 Discard any user changes to the memory regions and use target-supplied
7641 regions, if available, or no regions if the target does not support.
7644 @item delete mem @var{nums}@dots{}
7645 Remove memory regions @var{nums}@dots{} from the list of regions
7646 monitored by @value{GDBN}.
7649 @item disable mem @var{nums}@dots{}
7650 Disable monitoring of memory regions @var{nums}@dots{}.
7651 A disabled memory region is not forgotten.
7652 It may be enabled again later.
7655 @item enable mem @var{nums}@dots{}
7656 Enable monitoring of memory regions @var{nums}@dots{}.
7660 Print a table of all defined memory regions, with the following columns
7664 @item Memory Region Number
7665 @item Enabled or Disabled.
7666 Enabled memory regions are marked with @samp{y}.
7667 Disabled memory regions are marked with @samp{n}.
7670 The address defining the inclusive lower bound of the memory region.
7673 The address defining the exclusive upper bound of the memory region.
7676 The list of attributes set for this memory region.
7681 @subsection Attributes
7683 @subsubsection Memory Access Mode
7684 The access mode attributes set whether @value{GDBN} may make read or
7685 write accesses to a memory region.
7687 While these attributes prevent @value{GDBN} from performing invalid
7688 memory accesses, they do nothing to prevent the target system, I/O DMA,
7689 etc.@: from accessing memory.
7693 Memory is read only.
7695 Memory is write only.
7697 Memory is read/write. This is the default.
7700 @subsubsection Memory Access Size
7701 The access size attribute tells @value{GDBN} to use specific sized
7702 accesses in the memory region. Often memory mapped device registers
7703 require specific sized accesses. If no access size attribute is
7704 specified, @value{GDBN} may use accesses of any size.
7708 Use 8 bit memory accesses.
7710 Use 16 bit memory accesses.
7712 Use 32 bit memory accesses.
7714 Use 64 bit memory accesses.
7717 @c @subsubsection Hardware/Software Breakpoints
7718 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7719 @c will use hardware or software breakpoints for the internal breakpoints
7720 @c used by the step, next, finish, until, etc. commands.
7724 @c Always use hardware breakpoints
7725 @c @item swbreak (default)
7728 @subsubsection Data Cache
7729 The data cache attributes set whether @value{GDBN} will cache target
7730 memory. While this generally improves performance by reducing debug
7731 protocol overhead, it can lead to incorrect results because @value{GDBN}
7732 does not know about volatile variables or memory mapped device
7737 Enable @value{GDBN} to cache target memory.
7739 Disable @value{GDBN} from caching target memory. This is the default.
7742 @subsection Memory Access Checking
7743 @value{GDBN} can be instructed to refuse accesses to memory that is
7744 not explicitly described. This can be useful if accessing such
7745 regions has undesired effects for a specific target, or to provide
7746 better error checking. The following commands control this behaviour.
7749 @kindex set mem inaccessible-by-default
7750 @item set mem inaccessible-by-default [on|off]
7751 If @code{on} is specified, make @value{GDBN} treat memory not
7752 explicitly described by the memory ranges as non-existent and refuse accesses
7753 to such memory. The checks are only performed if there's at least one
7754 memory range defined. If @code{off} is specified, make @value{GDBN}
7755 treat the memory not explicitly described by the memory ranges as RAM.
7756 The default value is @code{on}.
7757 @kindex show mem inaccessible-by-default
7758 @item show mem inaccessible-by-default
7759 Show the current handling of accesses to unknown memory.
7763 @c @subsubsection Memory Write Verification
7764 @c The memory write verification attributes set whether @value{GDBN}
7765 @c will re-reads data after each write to verify the write was successful.
7769 @c @item noverify (default)
7772 @node Dump/Restore Files
7773 @section Copy Between Memory and a File
7774 @cindex dump/restore files
7775 @cindex append data to a file
7776 @cindex dump data to a file
7777 @cindex restore data from a file
7779 You can use the commands @code{dump}, @code{append}, and
7780 @code{restore} to copy data between target memory and a file. The
7781 @code{dump} and @code{append} commands write data to a file, and the
7782 @code{restore} command reads data from a file back into the inferior's
7783 memory. Files may be in binary, Motorola S-record, Intel hex, or
7784 Tektronix Hex format; however, @value{GDBN} can only append to binary
7790 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7791 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7792 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7793 or the value of @var{expr}, to @var{filename} in the given format.
7795 The @var{format} parameter may be any one of:
7802 Motorola S-record format.
7804 Tektronix Hex format.
7807 @value{GDBN} uses the same definitions of these formats as the
7808 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7809 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7813 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7814 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7815 Append the contents of memory from @var{start_addr} to @var{end_addr},
7816 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7817 (@value{GDBN} can only append data to files in raw binary form.)
7820 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7821 Restore the contents of file @var{filename} into memory. The
7822 @code{restore} command can automatically recognize any known @sc{bfd}
7823 file format, except for raw binary. To restore a raw binary file you
7824 must specify the optional keyword @code{binary} after the filename.
7826 If @var{bias} is non-zero, its value will be added to the addresses
7827 contained in the file. Binary files always start at address zero, so
7828 they will be restored at address @var{bias}. Other bfd files have
7829 a built-in location; they will be restored at offset @var{bias}
7832 If @var{start} and/or @var{end} are non-zero, then only data between
7833 file offset @var{start} and file offset @var{end} will be restored.
7834 These offsets are relative to the addresses in the file, before
7835 the @var{bias} argument is applied.
7839 @node Core File Generation
7840 @section How to Produce a Core File from Your Program
7841 @cindex dump core from inferior
7843 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7844 image of a running process and its process status (register values
7845 etc.). Its primary use is post-mortem debugging of a program that
7846 crashed while it ran outside a debugger. A program that crashes
7847 automatically produces a core file, unless this feature is disabled by
7848 the user. @xref{Files}, for information on invoking @value{GDBN} in
7849 the post-mortem debugging mode.
7851 Occasionally, you may wish to produce a core file of the program you
7852 are debugging in order to preserve a snapshot of its state.
7853 @value{GDBN} has a special command for that.
7857 @kindex generate-core-file
7858 @item generate-core-file [@var{file}]
7859 @itemx gcore [@var{file}]
7860 Produce a core dump of the inferior process. The optional argument
7861 @var{file} specifies the file name where to put the core dump. If not
7862 specified, the file name defaults to @file{core.@var{pid}}, where
7863 @var{pid} is the inferior process ID.
7865 Note that this command is implemented only for some systems (as of
7866 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7869 @node Character Sets
7870 @section Character Sets
7871 @cindex character sets
7873 @cindex translating between character sets
7874 @cindex host character set
7875 @cindex target character set
7877 If the program you are debugging uses a different character set to
7878 represent characters and strings than the one @value{GDBN} uses itself,
7879 @value{GDBN} can automatically translate between the character sets for
7880 you. The character set @value{GDBN} uses we call the @dfn{host
7881 character set}; the one the inferior program uses we call the
7882 @dfn{target character set}.
7884 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7885 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7886 remote protocol (@pxref{Remote Debugging}) to debug a program
7887 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7888 then the host character set is Latin-1, and the target character set is
7889 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7890 target-charset EBCDIC-US}, then @value{GDBN} translates between
7891 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7892 character and string literals in expressions.
7894 @value{GDBN} has no way to automatically recognize which character set
7895 the inferior program uses; you must tell it, using the @code{set
7896 target-charset} command, described below.
7898 Here are the commands for controlling @value{GDBN}'s character set
7902 @item set target-charset @var{charset}
7903 @kindex set target-charset
7904 Set the current target character set to @var{charset}. We list the
7905 character set names @value{GDBN} recognizes below, but if you type
7906 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7907 list the target character sets it supports.
7911 @item set host-charset @var{charset}
7912 @kindex set host-charset
7913 Set the current host character set to @var{charset}.
7915 By default, @value{GDBN} uses a host character set appropriate to the
7916 system it is running on; you can override that default using the
7917 @code{set host-charset} command.
7919 @value{GDBN} can only use certain character sets as its host character
7920 set. We list the character set names @value{GDBN} recognizes below, and
7921 indicate which can be host character sets, but if you type
7922 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7923 list the host character sets it supports.
7925 @item set charset @var{charset}
7927 Set the current host and target character sets to @var{charset}. As
7928 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7929 @value{GDBN} will list the name of the character sets that can be used
7930 for both host and target.
7934 @kindex show charset
7935 Show the names of the current host and target charsets.
7937 @itemx show host-charset
7938 @kindex show host-charset
7939 Show the name of the current host charset.
7941 @itemx show target-charset
7942 @kindex show target-charset
7943 Show the name of the current target charset.
7947 @value{GDBN} currently includes support for the following character
7953 @cindex ASCII character set
7954 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7958 @cindex ISO 8859-1 character set
7959 @cindex ISO Latin 1 character set
7960 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7961 characters needed for French, German, and Spanish. @value{GDBN} can use
7962 this as its host character set.
7966 @cindex EBCDIC character set
7967 @cindex IBM1047 character set
7968 Variants of the @sc{ebcdic} character set, used on some of IBM's
7969 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7970 @value{GDBN} cannot use these as its host character set.
7974 Note that these are all single-byte character sets. More work inside
7975 @value{GDBN} is needed to support multi-byte or variable-width character
7976 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7978 Here is an example of @value{GDBN}'s character set support in action.
7979 Assume that the following source code has been placed in the file
7980 @file{charset-test.c}:
7986 = @{72, 101, 108, 108, 111, 44, 32, 119,
7987 111, 114, 108, 100, 33, 10, 0@};
7988 char ibm1047_hello[]
7989 = @{200, 133, 147, 147, 150, 107, 64, 166,
7990 150, 153, 147, 132, 90, 37, 0@};
7994 printf ("Hello, world!\n");
7998 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7999 containing the string @samp{Hello, world!} followed by a newline,
8000 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8002 We compile the program, and invoke the debugger on it:
8005 $ gcc -g charset-test.c -o charset-test
8006 $ gdb -nw charset-test
8007 GNU gdb 2001-12-19-cvs
8008 Copyright 2001 Free Software Foundation, Inc.
8013 We can use the @code{show charset} command to see what character sets
8014 @value{GDBN} is currently using to interpret and display characters and
8018 (@value{GDBP}) show charset
8019 The current host and target character set is `ISO-8859-1'.
8023 For the sake of printing this manual, let's use @sc{ascii} as our
8024 initial character set:
8026 (@value{GDBP}) set charset ASCII
8027 (@value{GDBP}) show charset
8028 The current host and target character set is `ASCII'.
8032 Let's assume that @sc{ascii} is indeed the correct character set for our
8033 host system --- in other words, let's assume that if @value{GDBN} prints
8034 characters using the @sc{ascii} character set, our terminal will display
8035 them properly. Since our current target character set is also
8036 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8039 (@value{GDBP}) print ascii_hello
8040 $1 = 0x401698 "Hello, world!\n"
8041 (@value{GDBP}) print ascii_hello[0]
8046 @value{GDBN} uses the target character set for character and string
8047 literals you use in expressions:
8050 (@value{GDBP}) print '+'
8055 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8058 @value{GDBN} relies on the user to tell it which character set the
8059 target program uses. If we print @code{ibm1047_hello} while our target
8060 character set is still @sc{ascii}, we get jibberish:
8063 (@value{GDBP}) print ibm1047_hello
8064 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8065 (@value{GDBP}) print ibm1047_hello[0]
8070 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8071 @value{GDBN} tells us the character sets it supports:
8074 (@value{GDBP}) set target-charset
8075 ASCII EBCDIC-US IBM1047 ISO-8859-1
8076 (@value{GDBP}) set target-charset
8079 We can select @sc{ibm1047} as our target character set, and examine the
8080 program's strings again. Now the @sc{ascii} string is wrong, but
8081 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8082 target character set, @sc{ibm1047}, to the host character set,
8083 @sc{ascii}, and they display correctly:
8086 (@value{GDBP}) set target-charset IBM1047
8087 (@value{GDBP}) show charset
8088 The current host character set is `ASCII'.
8089 The current target character set is `IBM1047'.
8090 (@value{GDBP}) print ascii_hello
8091 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8092 (@value{GDBP}) print ascii_hello[0]
8094 (@value{GDBP}) print ibm1047_hello
8095 $8 = 0x4016a8 "Hello, world!\n"
8096 (@value{GDBP}) print ibm1047_hello[0]
8101 As above, @value{GDBN} uses the target character set for character and
8102 string literals you use in expressions:
8105 (@value{GDBP}) print '+'
8110 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8113 @node Caching Remote Data
8114 @section Caching Data of Remote Targets
8115 @cindex caching data of remote targets
8117 @value{GDBN} can cache data exchanged between the debugger and a
8118 remote target (@pxref{Remote Debugging}). Such caching generally improves
8119 performance, because it reduces the overhead of the remote protocol by
8120 bundling memory reads and writes into large chunks. Unfortunately,
8121 @value{GDBN} does not currently know anything about volatile
8122 registers, and thus data caching will produce incorrect results when
8123 volatile registers are in use.
8126 @kindex set remotecache
8127 @item set remotecache on
8128 @itemx set remotecache off
8129 Set caching state for remote targets. When @code{ON}, use data
8130 caching. By default, this option is @code{OFF}.
8132 @kindex show remotecache
8133 @item show remotecache
8134 Show the current state of data caching for remote targets.
8138 Print the information about the data cache performance. The
8139 information displayed includes: the dcache width and depth; and for
8140 each cache line, how many times it was referenced, and its data and
8141 state (invalid, dirty, valid). This command is useful for debugging
8142 the data cache operation.
8145 @node Searching Memory
8146 @section Search Memory
8147 @cindex searching memory
8149 Memory can be searched for a particular sequence of bytes with the
8150 @code{find} command.
8154 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8155 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8156 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8157 etc. The search begins at address @var{start_addr} and continues for either
8158 @var{len} bytes or through to @var{end_addr} inclusive.
8161 @var{s} and @var{n} are optional parameters.
8162 They may be specified in either order, apart or together.
8165 @item @var{s}, search query size
8166 The size of each search query value.
8172 halfwords (two bytes)
8176 giant words (eight bytes)
8179 All values are interpreted in the current language.
8180 This means, for example, that if the current source language is C/C@t{++}
8181 then searching for the string ``hello'' includes the trailing '\0'.
8183 If the value size is not specified, it is taken from the
8184 value's type in the current language.
8185 This is useful when one wants to specify the search
8186 pattern as a mixture of types.
8187 Note that this means, for example, that in the case of C-like languages
8188 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8189 which is typically four bytes.
8191 @item @var{n}, maximum number of finds
8192 The maximum number of matches to print. The default is to print all finds.
8195 You can use strings as search values. Quote them with double-quotes
8197 The string value is copied into the search pattern byte by byte,
8198 regardless of the endianness of the target and the size specification.
8200 The address of each match found is printed as well as a count of the
8201 number of matches found.
8203 The address of the last value found is stored in convenience variable
8205 A count of the number of matches is stored in @samp{$numfound}.
8207 For example, if stopped at the @code{printf} in this function:
8213 static char hello[] = "hello-hello";
8214 static struct @{ char c; short s; int i; @}
8215 __attribute__ ((packed)) mixed
8216 = @{ 'c', 0x1234, 0x87654321 @};
8217 printf ("%s\n", hello);
8222 you get during debugging:
8225 (gdb) find &hello[0], +sizeof(hello), "hello"
8226 0x804956d <hello.1620+6>
8228 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8229 0x8049567 <hello.1620>
8230 0x804956d <hello.1620+6>
8232 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8233 0x8049567 <hello.1620>
8235 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8236 0x8049560 <mixed.1625>
8238 (gdb) print $numfound
8241 $2 = (void *) 0x8049560
8245 @chapter C Preprocessor Macros
8247 Some languages, such as C and C@t{++}, provide a way to define and invoke
8248 ``preprocessor macros'' which expand into strings of tokens.
8249 @value{GDBN} can evaluate expressions containing macro invocations, show
8250 the result of macro expansion, and show a macro's definition, including
8251 where it was defined.
8253 You may need to compile your program specially to provide @value{GDBN}
8254 with information about preprocessor macros. Most compilers do not
8255 include macros in their debugging information, even when you compile
8256 with the @option{-g} flag. @xref{Compilation}.
8258 A program may define a macro at one point, remove that definition later,
8259 and then provide a different definition after that. Thus, at different
8260 points in the program, a macro may have different definitions, or have
8261 no definition at all. If there is a current stack frame, @value{GDBN}
8262 uses the macros in scope at that frame's source code line. Otherwise,
8263 @value{GDBN} uses the macros in scope at the current listing location;
8266 Whenever @value{GDBN} evaluates an expression, it always expands any
8267 macro invocations present in the expression. @value{GDBN} also provides
8268 the following commands for working with macros explicitly.
8272 @kindex macro expand
8273 @cindex macro expansion, showing the results of preprocessor
8274 @cindex preprocessor macro expansion, showing the results of
8275 @cindex expanding preprocessor macros
8276 @item macro expand @var{expression}
8277 @itemx macro exp @var{expression}
8278 Show the results of expanding all preprocessor macro invocations in
8279 @var{expression}. Since @value{GDBN} simply expands macros, but does
8280 not parse the result, @var{expression} need not be a valid expression;
8281 it can be any string of tokens.
8284 @item macro expand-once @var{expression}
8285 @itemx macro exp1 @var{expression}
8286 @cindex expand macro once
8287 @i{(This command is not yet implemented.)} Show the results of
8288 expanding those preprocessor macro invocations that appear explicitly in
8289 @var{expression}. Macro invocations appearing in that expansion are
8290 left unchanged. This command allows you to see the effect of a
8291 particular macro more clearly, without being confused by further
8292 expansions. Since @value{GDBN} simply expands macros, but does not
8293 parse the result, @var{expression} need not be a valid expression; it
8294 can be any string of tokens.
8297 @cindex macro definition, showing
8298 @cindex definition, showing a macro's
8299 @item info macro @var{macro}
8300 Show the definition of the macro named @var{macro}, and describe the
8301 source location where that definition was established.
8303 @kindex macro define
8304 @cindex user-defined macros
8305 @cindex defining macros interactively
8306 @cindex macros, user-defined
8307 @item macro define @var{macro} @var{replacement-list}
8308 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8309 Introduce a definition for a preprocessor macro named @var{macro},
8310 invocations of which are replaced by the tokens given in
8311 @var{replacement-list}. The first form of this command defines an
8312 ``object-like'' macro, which takes no arguments; the second form
8313 defines a ``function-like'' macro, which takes the arguments given in
8316 A definition introduced by this command is in scope in every
8317 expression evaluated in @value{GDBN}, until it is removed with the
8318 @code{macro undef} command, described below. The definition overrides
8319 all definitions for @var{macro} present in the program being debugged,
8320 as well as any previous user-supplied definition.
8323 @item macro undef @var{macro}
8324 Remove any user-supplied definition for the macro named @var{macro}.
8325 This command only affects definitions provided with the @code{macro
8326 define} command, described above; it cannot remove definitions present
8327 in the program being debugged.
8331 List all the macros defined using the @code{macro define} command.
8334 @cindex macros, example of debugging with
8335 Here is a transcript showing the above commands in action. First, we
8336 show our source files:
8344 #define ADD(x) (M + x)
8349 printf ("Hello, world!\n");
8351 printf ("We're so creative.\n");
8353 printf ("Goodbye, world!\n");
8360 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8361 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8362 compiler includes information about preprocessor macros in the debugging
8366 $ gcc -gdwarf-2 -g3 sample.c -o sample
8370 Now, we start @value{GDBN} on our sample program:
8374 GNU gdb 2002-05-06-cvs
8375 Copyright 2002 Free Software Foundation, Inc.
8376 GDB is free software, @dots{}
8380 We can expand macros and examine their definitions, even when the
8381 program is not running. @value{GDBN} uses the current listing position
8382 to decide which macro definitions are in scope:
8385 (@value{GDBP}) list main
8388 5 #define ADD(x) (M + x)
8393 10 printf ("Hello, world!\n");
8395 12 printf ("We're so creative.\n");
8396 (@value{GDBP}) info macro ADD
8397 Defined at /home/jimb/gdb/macros/play/sample.c:5
8398 #define ADD(x) (M + x)
8399 (@value{GDBP}) info macro Q
8400 Defined at /home/jimb/gdb/macros/play/sample.h:1
8401 included at /home/jimb/gdb/macros/play/sample.c:2
8403 (@value{GDBP}) macro expand ADD(1)
8404 expands to: (42 + 1)
8405 (@value{GDBP}) macro expand-once ADD(1)
8406 expands to: once (M + 1)
8410 In the example above, note that @code{macro expand-once} expands only
8411 the macro invocation explicit in the original text --- the invocation of
8412 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8413 which was introduced by @code{ADD}.
8415 Once the program is running, @value{GDBN} uses the macro definitions in
8416 force at the source line of the current stack frame:
8419 (@value{GDBP}) break main
8420 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8422 Starting program: /home/jimb/gdb/macros/play/sample
8424 Breakpoint 1, main () at sample.c:10
8425 10 printf ("Hello, world!\n");
8429 At line 10, the definition of the macro @code{N} at line 9 is in force:
8432 (@value{GDBP}) info macro N
8433 Defined at /home/jimb/gdb/macros/play/sample.c:9
8435 (@value{GDBP}) macro expand N Q M
8437 (@value{GDBP}) print N Q M
8442 As we step over directives that remove @code{N}'s definition, and then
8443 give it a new definition, @value{GDBN} finds the definition (or lack
8444 thereof) in force at each point:
8449 12 printf ("We're so creative.\n");
8450 (@value{GDBP}) info macro N
8451 The symbol `N' has no definition as a C/C++ preprocessor macro
8452 at /home/jimb/gdb/macros/play/sample.c:12
8455 14 printf ("Goodbye, world!\n");
8456 (@value{GDBP}) info macro N
8457 Defined at /home/jimb/gdb/macros/play/sample.c:13
8459 (@value{GDBP}) macro expand N Q M
8460 expands to: 1729 < 42
8461 (@value{GDBP}) print N Q M
8468 @chapter Tracepoints
8469 @c This chapter is based on the documentation written by Michael
8470 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8473 In some applications, it is not feasible for the debugger to interrupt
8474 the program's execution long enough for the developer to learn
8475 anything helpful about its behavior. If the program's correctness
8476 depends on its real-time behavior, delays introduced by a debugger
8477 might cause the program to change its behavior drastically, or perhaps
8478 fail, even when the code itself is correct. It is useful to be able
8479 to observe the program's behavior without interrupting it.
8481 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8482 specify locations in the program, called @dfn{tracepoints}, and
8483 arbitrary expressions to evaluate when those tracepoints are reached.
8484 Later, using the @code{tfind} command, you can examine the values
8485 those expressions had when the program hit the tracepoints. The
8486 expressions may also denote objects in memory---structures or arrays,
8487 for example---whose values @value{GDBN} should record; while visiting
8488 a particular tracepoint, you may inspect those objects as if they were
8489 in memory at that moment. However, because @value{GDBN} records these
8490 values without interacting with you, it can do so quickly and
8491 unobtrusively, hopefully not disturbing the program's behavior.
8493 The tracepoint facility is currently available only for remote
8494 targets. @xref{Targets}. In addition, your remote target must know
8495 how to collect trace data. This functionality is implemented in the
8496 remote stub; however, none of the stubs distributed with @value{GDBN}
8497 support tracepoints as of this writing. The format of the remote
8498 packets used to implement tracepoints are described in @ref{Tracepoint
8501 This chapter describes the tracepoint commands and features.
8505 * Analyze Collected Data::
8506 * Tracepoint Variables::
8509 @node Set Tracepoints
8510 @section Commands to Set Tracepoints
8512 Before running such a @dfn{trace experiment}, an arbitrary number of
8513 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8514 tracepoint has a number assigned to it by @value{GDBN}. Like with
8515 breakpoints, tracepoint numbers are successive integers starting from
8516 one. Many of the commands associated with tracepoints take the
8517 tracepoint number as their argument, to identify which tracepoint to
8520 For each tracepoint, you can specify, in advance, some arbitrary set
8521 of data that you want the target to collect in the trace buffer when
8522 it hits that tracepoint. The collected data can include registers,
8523 local variables, or global data. Later, you can use @value{GDBN}
8524 commands to examine the values these data had at the time the
8527 This section describes commands to set tracepoints and associated
8528 conditions and actions.
8531 * Create and Delete Tracepoints::
8532 * Enable and Disable Tracepoints::
8533 * Tracepoint Passcounts::
8534 * Tracepoint Actions::
8535 * Listing Tracepoints::
8536 * Starting and Stopping Trace Experiments::
8539 @node Create and Delete Tracepoints
8540 @subsection Create and Delete Tracepoints
8543 @cindex set tracepoint
8546 The @code{trace} command is very similar to the @code{break} command.
8547 Its argument can be a source line, a function name, or an address in
8548 the target program. @xref{Set Breaks}. The @code{trace} command
8549 defines a tracepoint, which is a point in the target program where the
8550 debugger will briefly stop, collect some data, and then allow the
8551 program to continue. Setting a tracepoint or changing its commands
8552 doesn't take effect until the next @code{tstart} command; thus, you
8553 cannot change the tracepoint attributes once a trace experiment is
8556 Here are some examples of using the @code{trace} command:
8559 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8561 (@value{GDBP}) @b{trace +2} // 2 lines forward
8563 (@value{GDBP}) @b{trace my_function} // first source line of function
8565 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8567 (@value{GDBP}) @b{trace *0x2117c4} // an address
8571 You can abbreviate @code{trace} as @code{tr}.
8574 @cindex last tracepoint number
8575 @cindex recent tracepoint number
8576 @cindex tracepoint number
8577 The convenience variable @code{$tpnum} records the tracepoint number
8578 of the most recently set tracepoint.
8580 @kindex delete tracepoint
8581 @cindex tracepoint deletion
8582 @item delete tracepoint @r{[}@var{num}@r{]}
8583 Permanently delete one or more tracepoints. With no argument, the
8584 default is to delete all tracepoints.
8589 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8591 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8595 You can abbreviate this command as @code{del tr}.
8598 @node Enable and Disable Tracepoints
8599 @subsection Enable and Disable Tracepoints
8602 @kindex disable tracepoint
8603 @item disable tracepoint @r{[}@var{num}@r{]}
8604 Disable tracepoint @var{num}, or all tracepoints if no argument
8605 @var{num} is given. A disabled tracepoint will have no effect during
8606 the next trace experiment, but it is not forgotten. You can re-enable
8607 a disabled tracepoint using the @code{enable tracepoint} command.
8609 @kindex enable tracepoint
8610 @item enable tracepoint @r{[}@var{num}@r{]}
8611 Enable tracepoint @var{num}, or all tracepoints. The enabled
8612 tracepoints will become effective the next time a trace experiment is
8616 @node Tracepoint Passcounts
8617 @subsection Tracepoint Passcounts
8621 @cindex tracepoint pass count
8622 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8623 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8624 automatically stop a trace experiment. If a tracepoint's passcount is
8625 @var{n}, then the trace experiment will be automatically stopped on
8626 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8627 @var{num} is not specified, the @code{passcount} command sets the
8628 passcount of the most recently defined tracepoint. If no passcount is
8629 given, the trace experiment will run until stopped explicitly by the
8635 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8636 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8638 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8639 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8640 (@value{GDBP}) @b{trace foo}
8641 (@value{GDBP}) @b{pass 3}
8642 (@value{GDBP}) @b{trace bar}
8643 (@value{GDBP}) @b{pass 2}
8644 (@value{GDBP}) @b{trace baz}
8645 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8646 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8647 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8648 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8652 @node Tracepoint Actions
8653 @subsection Tracepoint Action Lists
8657 @cindex tracepoint actions
8658 @item actions @r{[}@var{num}@r{]}
8659 This command will prompt for a list of actions to be taken when the
8660 tracepoint is hit. If the tracepoint number @var{num} is not
8661 specified, this command sets the actions for the one that was most
8662 recently defined (so that you can define a tracepoint and then say
8663 @code{actions} without bothering about its number). You specify the
8664 actions themselves on the following lines, one action at a time, and
8665 terminate the actions list with a line containing just @code{end}. So
8666 far, the only defined actions are @code{collect} and
8667 @code{while-stepping}.
8669 @cindex remove actions from a tracepoint
8670 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8671 and follow it immediately with @samp{end}.
8674 (@value{GDBP}) @b{collect @var{data}} // collect some data
8676 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8678 (@value{GDBP}) @b{end} // signals the end of actions.
8681 In the following example, the action list begins with @code{collect}
8682 commands indicating the things to be collected when the tracepoint is
8683 hit. Then, in order to single-step and collect additional data
8684 following the tracepoint, a @code{while-stepping} command is used,
8685 followed by the list of things to be collected while stepping. The
8686 @code{while-stepping} command is terminated by its own separate
8687 @code{end} command. Lastly, the action list is terminated by an
8691 (@value{GDBP}) @b{trace foo}
8692 (@value{GDBP}) @b{actions}
8693 Enter actions for tracepoint 1, one per line:
8702 @kindex collect @r{(tracepoints)}
8703 @item collect @var{expr1}, @var{expr2}, @dots{}
8704 Collect values of the given expressions when the tracepoint is hit.
8705 This command accepts a comma-separated list of any valid expressions.
8706 In addition to global, static, or local variables, the following
8707 special arguments are supported:
8711 collect all registers
8714 collect all function arguments
8717 collect all local variables.
8720 You can give several consecutive @code{collect} commands, each one
8721 with a single argument, or one @code{collect} command with several
8722 arguments separated by commas: the effect is the same.
8724 The command @code{info scope} (@pxref{Symbols, info scope}) is
8725 particularly useful for figuring out what data to collect.
8727 @kindex while-stepping @r{(tracepoints)}
8728 @item while-stepping @var{n}
8729 Perform @var{n} single-step traces after the tracepoint, collecting
8730 new data at each step. The @code{while-stepping} command is
8731 followed by the list of what to collect while stepping (followed by
8732 its own @code{end} command):
8736 > collect $regs, myglobal
8742 You may abbreviate @code{while-stepping} as @code{ws} or
8746 @node Listing Tracepoints
8747 @subsection Listing Tracepoints
8750 @kindex info tracepoints
8752 @cindex information about tracepoints
8753 @item info tracepoints @r{[}@var{num}@r{]}
8754 Display information about the tracepoint @var{num}. If you don't specify
8755 a tracepoint number, displays information about all the tracepoints
8756 defined so far. For each tracepoint, the following information is
8763 whether it is enabled or disabled
8767 its passcount as given by the @code{passcount @var{n}} command
8769 its step count as given by the @code{while-stepping @var{n}} command
8771 where in the source files is the tracepoint set
8773 its action list as given by the @code{actions} command
8777 (@value{GDBP}) @b{info trace}
8778 Num Enb Address PassC StepC What
8779 1 y 0x002117c4 0 0 <gdb_asm>
8780 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8781 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8786 This command can be abbreviated @code{info tp}.
8789 @node Starting and Stopping Trace Experiments
8790 @subsection Starting and Stopping Trace Experiments
8794 @cindex start a new trace experiment
8795 @cindex collected data discarded
8797 This command takes no arguments. It starts the trace experiment, and
8798 begins collecting data. This has the side effect of discarding all
8799 the data collected in the trace buffer during the previous trace
8803 @cindex stop a running trace experiment
8805 This command takes no arguments. It ends the trace experiment, and
8806 stops collecting data.
8808 @strong{Note}: a trace experiment and data collection may stop
8809 automatically if any tracepoint's passcount is reached
8810 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8813 @cindex status of trace data collection
8814 @cindex trace experiment, status of
8816 This command displays the status of the current trace data
8820 Here is an example of the commands we described so far:
8823 (@value{GDBP}) @b{trace gdb_c_test}
8824 (@value{GDBP}) @b{actions}
8825 Enter actions for tracepoint #1, one per line.
8826 > collect $regs,$locals,$args
8831 (@value{GDBP}) @b{tstart}
8832 [time passes @dots{}]
8833 (@value{GDBP}) @b{tstop}
8837 @node Analyze Collected Data
8838 @section Using the Collected Data
8840 After the tracepoint experiment ends, you use @value{GDBN} commands
8841 for examining the trace data. The basic idea is that each tracepoint
8842 collects a trace @dfn{snapshot} every time it is hit and another
8843 snapshot every time it single-steps. All these snapshots are
8844 consecutively numbered from zero and go into a buffer, and you can
8845 examine them later. The way you examine them is to @dfn{focus} on a
8846 specific trace snapshot. When the remote stub is focused on a trace
8847 snapshot, it will respond to all @value{GDBN} requests for memory and
8848 registers by reading from the buffer which belongs to that snapshot,
8849 rather than from @emph{real} memory or registers of the program being
8850 debugged. This means that @strong{all} @value{GDBN} commands
8851 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8852 behave as if we were currently debugging the program state as it was
8853 when the tracepoint occurred. Any requests for data that are not in
8854 the buffer will fail.
8857 * tfind:: How to select a trace snapshot
8858 * tdump:: How to display all data for a snapshot
8859 * save-tracepoints:: How to save tracepoints for a future run
8863 @subsection @code{tfind @var{n}}
8866 @cindex select trace snapshot
8867 @cindex find trace snapshot
8868 The basic command for selecting a trace snapshot from the buffer is
8869 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8870 counting from zero. If no argument @var{n} is given, the next
8871 snapshot is selected.
8873 Here are the various forms of using the @code{tfind} command.
8877 Find the first snapshot in the buffer. This is a synonym for
8878 @code{tfind 0} (since 0 is the number of the first snapshot).
8881 Stop debugging trace snapshots, resume @emph{live} debugging.
8884 Same as @samp{tfind none}.
8887 No argument means find the next trace snapshot.
8890 Find the previous trace snapshot before the current one. This permits
8891 retracing earlier steps.
8893 @item tfind tracepoint @var{num}
8894 Find the next snapshot associated with tracepoint @var{num}. Search
8895 proceeds forward from the last examined trace snapshot. If no
8896 argument @var{num} is given, it means find the next snapshot collected
8897 for the same tracepoint as the current snapshot.
8899 @item tfind pc @var{addr}
8900 Find the next snapshot associated with the value @var{addr} of the
8901 program counter. Search proceeds forward from the last examined trace
8902 snapshot. If no argument @var{addr} is given, it means find the next
8903 snapshot with the same value of PC as the current snapshot.
8905 @item tfind outside @var{addr1}, @var{addr2}
8906 Find the next snapshot whose PC is outside the given range of
8909 @item tfind range @var{addr1}, @var{addr2}
8910 Find the next snapshot whose PC is between @var{addr1} and
8911 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8913 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8914 Find the next snapshot associated with the source line @var{n}. If
8915 the optional argument @var{file} is given, refer to line @var{n} in
8916 that source file. Search proceeds forward from the last examined
8917 trace snapshot. If no argument @var{n} is given, it means find the
8918 next line other than the one currently being examined; thus saying
8919 @code{tfind line} repeatedly can appear to have the same effect as
8920 stepping from line to line in a @emph{live} debugging session.
8923 The default arguments for the @code{tfind} commands are specifically
8924 designed to make it easy to scan through the trace buffer. For
8925 instance, @code{tfind} with no argument selects the next trace
8926 snapshot, and @code{tfind -} with no argument selects the previous
8927 trace snapshot. So, by giving one @code{tfind} command, and then
8928 simply hitting @key{RET} repeatedly you can examine all the trace
8929 snapshots in order. Or, by saying @code{tfind -} and then hitting
8930 @key{RET} repeatedly you can examine the snapshots in reverse order.
8931 The @code{tfind line} command with no argument selects the snapshot
8932 for the next source line executed. The @code{tfind pc} command with
8933 no argument selects the next snapshot with the same program counter
8934 (PC) as the current frame. The @code{tfind tracepoint} command with
8935 no argument selects the next trace snapshot collected by the same
8936 tracepoint as the current one.
8938 In addition to letting you scan through the trace buffer manually,
8939 these commands make it easy to construct @value{GDBN} scripts that
8940 scan through the trace buffer and print out whatever collected data
8941 you are interested in. Thus, if we want to examine the PC, FP, and SP
8942 registers from each trace frame in the buffer, we can say this:
8945 (@value{GDBP}) @b{tfind start}
8946 (@value{GDBP}) @b{while ($trace_frame != -1)}
8947 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8948 $trace_frame, $pc, $sp, $fp
8952 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8953 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8954 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8955 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8956 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8957 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8958 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8959 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8960 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8961 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8962 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8965 Or, if we want to examine the variable @code{X} at each source line in
8969 (@value{GDBP}) @b{tfind start}
8970 (@value{GDBP}) @b{while ($trace_frame != -1)}
8971 > printf "Frame %d, X == %d\n", $trace_frame, X
8981 @subsection @code{tdump}
8983 @cindex dump all data collected at tracepoint
8984 @cindex tracepoint data, display
8986 This command takes no arguments. It prints all the data collected at
8987 the current trace snapshot.
8990 (@value{GDBP}) @b{trace 444}
8991 (@value{GDBP}) @b{actions}
8992 Enter actions for tracepoint #2, one per line:
8993 > collect $regs, $locals, $args, gdb_long_test
8996 (@value{GDBP}) @b{tstart}
8998 (@value{GDBP}) @b{tfind line 444}
8999 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9001 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9003 (@value{GDBP}) @b{tdump}
9004 Data collected at tracepoint 2, trace frame 1:
9005 d0 0xc4aa0085 -995491707
9009 d4 0x71aea3d 119204413
9014 a1 0x3000668 50333288
9017 a4 0x3000698 50333336
9019 fp 0x30bf3c 0x30bf3c
9020 sp 0x30bf34 0x30bf34
9022 pc 0x20b2c8 0x20b2c8
9026 p = 0x20e5b4 "gdb-test"
9033 gdb_long_test = 17 '\021'
9038 @node save-tracepoints
9039 @subsection @code{save-tracepoints @var{filename}}
9040 @kindex save-tracepoints
9041 @cindex save tracepoints for future sessions
9043 This command saves all current tracepoint definitions together with
9044 their actions and passcounts, into a file @file{@var{filename}}
9045 suitable for use in a later debugging session. To read the saved
9046 tracepoint definitions, use the @code{source} command (@pxref{Command
9049 @node Tracepoint Variables
9050 @section Convenience Variables for Tracepoints
9051 @cindex tracepoint variables
9052 @cindex convenience variables for tracepoints
9055 @vindex $trace_frame
9056 @item (int) $trace_frame
9057 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9058 snapshot is selected.
9061 @item (int) $tracepoint
9062 The tracepoint for the current trace snapshot.
9065 @item (int) $trace_line
9066 The line number for the current trace snapshot.
9069 @item (char []) $trace_file
9070 The source file for the current trace snapshot.
9073 @item (char []) $trace_func
9074 The name of the function containing @code{$tracepoint}.
9077 Note: @code{$trace_file} is not suitable for use in @code{printf},
9078 use @code{output} instead.
9080 Here's a simple example of using these convenience variables for
9081 stepping through all the trace snapshots and printing some of their
9085 (@value{GDBP}) @b{tfind start}
9087 (@value{GDBP}) @b{while $trace_frame != -1}
9088 > output $trace_file
9089 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9095 @chapter Debugging Programs That Use Overlays
9098 If your program is too large to fit completely in your target system's
9099 memory, you can sometimes use @dfn{overlays} to work around this
9100 problem. @value{GDBN} provides some support for debugging programs that
9104 * How Overlays Work:: A general explanation of overlays.
9105 * Overlay Commands:: Managing overlays in @value{GDBN}.
9106 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9107 mapped by asking the inferior.
9108 * Overlay Sample Program:: A sample program using overlays.
9111 @node How Overlays Work
9112 @section How Overlays Work
9113 @cindex mapped overlays
9114 @cindex unmapped overlays
9115 @cindex load address, overlay's
9116 @cindex mapped address
9117 @cindex overlay area
9119 Suppose you have a computer whose instruction address space is only 64
9120 kilobytes long, but which has much more memory which can be accessed by
9121 other means: special instructions, segment registers, or memory
9122 management hardware, for example. Suppose further that you want to
9123 adapt a program which is larger than 64 kilobytes to run on this system.
9125 One solution is to identify modules of your program which are relatively
9126 independent, and need not call each other directly; call these modules
9127 @dfn{overlays}. Separate the overlays from the main program, and place
9128 their machine code in the larger memory. Place your main program in
9129 instruction memory, but leave at least enough space there to hold the
9130 largest overlay as well.
9132 Now, to call a function located in an overlay, you must first copy that
9133 overlay's machine code from the large memory into the space set aside
9134 for it in the instruction memory, and then jump to its entry point
9137 @c NB: In the below the mapped area's size is greater or equal to the
9138 @c size of all overlays. This is intentional to remind the developer
9139 @c that overlays don't necessarily need to be the same size.
9143 Data Instruction Larger
9144 Address Space Address Space Address Space
9145 +-----------+ +-----------+ +-----------+
9147 +-----------+ +-----------+ +-----------+<-- overlay 1
9148 | program | | main | .----| overlay 1 | load address
9149 | variables | | program | | +-----------+
9150 | and heap | | | | | |
9151 +-----------+ | | | +-----------+<-- overlay 2
9152 | | +-----------+ | | | load address
9153 +-----------+ | | | .-| overlay 2 |
9155 mapped --->+-----------+ | | +-----------+
9157 | overlay | <-' | | |
9158 | area | <---' +-----------+<-- overlay 3
9159 | | <---. | | load address
9160 +-----------+ `--| overlay 3 |
9167 @anchor{A code overlay}A code overlay
9171 The diagram (@pxref{A code overlay}) shows a system with separate data
9172 and instruction address spaces. To map an overlay, the program copies
9173 its code from the larger address space to the instruction address space.
9174 Since the overlays shown here all use the same mapped address, only one
9175 may be mapped at a time. For a system with a single address space for
9176 data and instructions, the diagram would be similar, except that the
9177 program variables and heap would share an address space with the main
9178 program and the overlay area.
9180 An overlay loaded into instruction memory and ready for use is called a
9181 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9182 instruction memory. An overlay not present (or only partially present)
9183 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9184 is its address in the larger memory. The mapped address is also called
9185 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9186 called the @dfn{load memory address}, or @dfn{LMA}.
9188 Unfortunately, overlays are not a completely transparent way to adapt a
9189 program to limited instruction memory. They introduce a new set of
9190 global constraints you must keep in mind as you design your program:
9195 Before calling or returning to a function in an overlay, your program
9196 must make sure that overlay is actually mapped. Otherwise, the call or
9197 return will transfer control to the right address, but in the wrong
9198 overlay, and your program will probably crash.
9201 If the process of mapping an overlay is expensive on your system, you
9202 will need to choose your overlays carefully to minimize their effect on
9203 your program's performance.
9206 The executable file you load onto your system must contain each
9207 overlay's instructions, appearing at the overlay's load address, not its
9208 mapped address. However, each overlay's instructions must be relocated
9209 and its symbols defined as if the overlay were at its mapped address.
9210 You can use GNU linker scripts to specify different load and relocation
9211 addresses for pieces of your program; see @ref{Overlay Description,,,
9212 ld.info, Using ld: the GNU linker}.
9215 The procedure for loading executable files onto your system must be able
9216 to load their contents into the larger address space as well as the
9217 instruction and data spaces.
9221 The overlay system described above is rather simple, and could be
9222 improved in many ways:
9227 If your system has suitable bank switch registers or memory management
9228 hardware, you could use those facilities to make an overlay's load area
9229 contents simply appear at their mapped address in instruction space.
9230 This would probably be faster than copying the overlay to its mapped
9231 area in the usual way.
9234 If your overlays are small enough, you could set aside more than one
9235 overlay area, and have more than one overlay mapped at a time.
9238 You can use overlays to manage data, as well as instructions. In
9239 general, data overlays are even less transparent to your design than
9240 code overlays: whereas code overlays only require care when you call or
9241 return to functions, data overlays require care every time you access
9242 the data. Also, if you change the contents of a data overlay, you
9243 must copy its contents back out to its load address before you can copy a
9244 different data overlay into the same mapped area.
9249 @node Overlay Commands
9250 @section Overlay Commands
9252 To use @value{GDBN}'s overlay support, each overlay in your program must
9253 correspond to a separate section of the executable file. The section's
9254 virtual memory address and load memory address must be the overlay's
9255 mapped and load addresses. Identifying overlays with sections allows
9256 @value{GDBN} to determine the appropriate address of a function or
9257 variable, depending on whether the overlay is mapped or not.
9259 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9260 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9265 Disable @value{GDBN}'s overlay support. When overlay support is
9266 disabled, @value{GDBN} assumes that all functions and variables are
9267 always present at their mapped addresses. By default, @value{GDBN}'s
9268 overlay support is disabled.
9270 @item overlay manual
9271 @cindex manual overlay debugging
9272 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9273 relies on you to tell it which overlays are mapped, and which are not,
9274 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9275 commands described below.
9277 @item overlay map-overlay @var{overlay}
9278 @itemx overlay map @var{overlay}
9279 @cindex map an overlay
9280 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9281 be the name of the object file section containing the overlay. When an
9282 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9283 functions and variables at their mapped addresses. @value{GDBN} assumes
9284 that any other overlays whose mapped ranges overlap that of
9285 @var{overlay} are now unmapped.
9287 @item overlay unmap-overlay @var{overlay}
9288 @itemx overlay unmap @var{overlay}
9289 @cindex unmap an overlay
9290 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9291 must be the name of the object file section containing the overlay.
9292 When an overlay is unmapped, @value{GDBN} assumes it can find the
9293 overlay's functions and variables at their load addresses.
9296 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9297 consults a data structure the overlay manager maintains in the inferior
9298 to see which overlays are mapped. For details, see @ref{Automatic
9301 @item overlay load-target
9303 @cindex reloading the overlay table
9304 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9305 re-reads the table @value{GDBN} automatically each time the inferior
9306 stops, so this command should only be necessary if you have changed the
9307 overlay mapping yourself using @value{GDBN}. This command is only
9308 useful when using automatic overlay debugging.
9310 @item overlay list-overlays
9312 @cindex listing mapped overlays
9313 Display a list of the overlays currently mapped, along with their mapped
9314 addresses, load addresses, and sizes.
9318 Normally, when @value{GDBN} prints a code address, it includes the name
9319 of the function the address falls in:
9322 (@value{GDBP}) print main
9323 $3 = @{int ()@} 0x11a0 <main>
9326 When overlay debugging is enabled, @value{GDBN} recognizes code in
9327 unmapped overlays, and prints the names of unmapped functions with
9328 asterisks around them. For example, if @code{foo} is a function in an
9329 unmapped overlay, @value{GDBN} prints it this way:
9332 (@value{GDBP}) overlay list
9333 No sections are mapped.
9334 (@value{GDBP}) print foo
9335 $5 = @{int (int)@} 0x100000 <*foo*>
9338 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9342 (@value{GDBP}) overlay list
9343 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9344 mapped at 0x1016 - 0x104a
9345 (@value{GDBP}) print foo
9346 $6 = @{int (int)@} 0x1016 <foo>
9349 When overlay debugging is enabled, @value{GDBN} can find the correct
9350 address for functions and variables in an overlay, whether or not the
9351 overlay is mapped. This allows most @value{GDBN} commands, like
9352 @code{break} and @code{disassemble}, to work normally, even on unmapped
9353 code. However, @value{GDBN}'s breakpoint support has some limitations:
9357 @cindex breakpoints in overlays
9358 @cindex overlays, setting breakpoints in
9359 You can set breakpoints in functions in unmapped overlays, as long as
9360 @value{GDBN} can write to the overlay at its load address.
9362 @value{GDBN} can not set hardware or simulator-based breakpoints in
9363 unmapped overlays. However, if you set a breakpoint at the end of your
9364 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9365 you are using manual overlay management), @value{GDBN} will re-set its
9366 breakpoints properly.
9370 @node Automatic Overlay Debugging
9371 @section Automatic Overlay Debugging
9372 @cindex automatic overlay debugging
9374 @value{GDBN} can automatically track which overlays are mapped and which
9375 are not, given some simple co-operation from the overlay manager in the
9376 inferior. If you enable automatic overlay debugging with the
9377 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9378 looks in the inferior's memory for certain variables describing the
9379 current state of the overlays.
9381 Here are the variables your overlay manager must define to support
9382 @value{GDBN}'s automatic overlay debugging:
9386 @item @code{_ovly_table}:
9387 This variable must be an array of the following structures:
9392 /* The overlay's mapped address. */
9395 /* The size of the overlay, in bytes. */
9398 /* The overlay's load address. */
9401 /* Non-zero if the overlay is currently mapped;
9403 unsigned long mapped;
9407 @item @code{_novlys}:
9408 This variable must be a four-byte signed integer, holding the total
9409 number of elements in @code{_ovly_table}.
9413 To decide whether a particular overlay is mapped or not, @value{GDBN}
9414 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9415 @code{lma} members equal the VMA and LMA of the overlay's section in the
9416 executable file. When @value{GDBN} finds a matching entry, it consults
9417 the entry's @code{mapped} member to determine whether the overlay is
9420 In addition, your overlay manager may define a function called
9421 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9422 will silently set a breakpoint there. If the overlay manager then
9423 calls this function whenever it has changed the overlay table, this
9424 will enable @value{GDBN} to accurately keep track of which overlays
9425 are in program memory, and update any breakpoints that may be set
9426 in overlays. This will allow breakpoints to work even if the
9427 overlays are kept in ROM or other non-writable memory while they
9428 are not being executed.
9430 @node Overlay Sample Program
9431 @section Overlay Sample Program
9432 @cindex overlay example program
9434 When linking a program which uses overlays, you must place the overlays
9435 at their load addresses, while relocating them to run at their mapped
9436 addresses. To do this, you must write a linker script (@pxref{Overlay
9437 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9438 since linker scripts are specific to a particular host system, target
9439 architecture, and target memory layout, this manual cannot provide
9440 portable sample code demonstrating @value{GDBN}'s overlay support.
9442 However, the @value{GDBN} source distribution does contain an overlaid
9443 program, with linker scripts for a few systems, as part of its test
9444 suite. The program consists of the following files from
9445 @file{gdb/testsuite/gdb.base}:
9449 The main program file.
9451 A simple overlay manager, used by @file{overlays.c}.
9456 Overlay modules, loaded and used by @file{overlays.c}.
9459 Linker scripts for linking the test program on the @code{d10v-elf}
9460 and @code{m32r-elf} targets.
9463 You can build the test program using the @code{d10v-elf} GCC
9464 cross-compiler like this:
9467 $ d10v-elf-gcc -g -c overlays.c
9468 $ d10v-elf-gcc -g -c ovlymgr.c
9469 $ d10v-elf-gcc -g -c foo.c
9470 $ d10v-elf-gcc -g -c bar.c
9471 $ d10v-elf-gcc -g -c baz.c
9472 $ d10v-elf-gcc -g -c grbx.c
9473 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9474 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9477 The build process is identical for any other architecture, except that
9478 you must substitute the appropriate compiler and linker script for the
9479 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9483 @chapter Using @value{GDBN} with Different Languages
9486 Although programming languages generally have common aspects, they are
9487 rarely expressed in the same manner. For instance, in ANSI C,
9488 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9489 Modula-2, it is accomplished by @code{p^}. Values can also be
9490 represented (and displayed) differently. Hex numbers in C appear as
9491 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9493 @cindex working language
9494 Language-specific information is built into @value{GDBN} for some languages,
9495 allowing you to express operations like the above in your program's
9496 native language, and allowing @value{GDBN} to output values in a manner
9497 consistent with the syntax of your program's native language. The
9498 language you use to build expressions is called the @dfn{working
9502 * Setting:: Switching between source languages
9503 * Show:: Displaying the language
9504 * Checks:: Type and range checks
9505 * Supported Languages:: Supported languages
9506 * Unsupported Languages:: Unsupported languages
9510 @section Switching Between Source Languages
9512 There are two ways to control the working language---either have @value{GDBN}
9513 set it automatically, or select it manually yourself. You can use the
9514 @code{set language} command for either purpose. On startup, @value{GDBN}
9515 defaults to setting the language automatically. The working language is
9516 used to determine how expressions you type are interpreted, how values
9519 In addition to the working language, every source file that
9520 @value{GDBN} knows about has its own working language. For some object
9521 file formats, the compiler might indicate which language a particular
9522 source file is in. However, most of the time @value{GDBN} infers the
9523 language from the name of the file. The language of a source file
9524 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9525 show each frame appropriately for its own language. There is no way to
9526 set the language of a source file from within @value{GDBN}, but you can
9527 set the language associated with a filename extension. @xref{Show, ,
9528 Displaying the Language}.
9530 This is most commonly a problem when you use a program, such
9531 as @code{cfront} or @code{f2c}, that generates C but is written in
9532 another language. In that case, make the
9533 program use @code{#line} directives in its C output; that way
9534 @value{GDBN} will know the correct language of the source code of the original
9535 program, and will display that source code, not the generated C code.
9538 * Filenames:: Filename extensions and languages.
9539 * Manually:: Setting the working language manually
9540 * Automatically:: Having @value{GDBN} infer the source language
9544 @subsection List of Filename Extensions and Languages
9546 If a source file name ends in one of the following extensions, then
9547 @value{GDBN} infers that its language is the one indicated.
9568 Objective-C source file
9575 Modula-2 source file
9579 Assembler source file. This actually behaves almost like C, but
9580 @value{GDBN} does not skip over function prologues when stepping.
9583 In addition, you may set the language associated with a filename
9584 extension. @xref{Show, , Displaying the Language}.
9587 @subsection Setting the Working Language
9589 If you allow @value{GDBN} to set the language automatically,
9590 expressions are interpreted the same way in your debugging session and
9593 @kindex set language
9594 If you wish, you may set the language manually. To do this, issue the
9595 command @samp{set language @var{lang}}, where @var{lang} is the name of
9597 @code{c} or @code{modula-2}.
9598 For a list of the supported languages, type @samp{set language}.
9600 Setting the language manually prevents @value{GDBN} from updating the working
9601 language automatically. This can lead to confusion if you try
9602 to debug a program when the working language is not the same as the
9603 source language, when an expression is acceptable to both
9604 languages---but means different things. For instance, if the current
9605 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9613 might not have the effect you intended. In C, this means to add
9614 @code{b} and @code{c} and place the result in @code{a}. The result
9615 printed would be the value of @code{a}. In Modula-2, this means to compare
9616 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9619 @subsection Having @value{GDBN} Infer the Source Language
9621 To have @value{GDBN} set the working language automatically, use
9622 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9623 then infers the working language. That is, when your program stops in a
9624 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9625 working language to the language recorded for the function in that
9626 frame. If the language for a frame is unknown (that is, if the function
9627 or block corresponding to the frame was defined in a source file that
9628 does not have a recognized extension), the current working language is
9629 not changed, and @value{GDBN} issues a warning.
9631 This may not seem necessary for most programs, which are written
9632 entirely in one source language. However, program modules and libraries
9633 written in one source language can be used by a main program written in
9634 a different source language. Using @samp{set language auto} in this
9635 case frees you from having to set the working language manually.
9638 @section Displaying the Language
9640 The following commands help you find out which language is the
9641 working language, and also what language source files were written in.
9645 @kindex show language
9646 Display the current working language. This is the
9647 language you can use with commands such as @code{print} to
9648 build and compute expressions that may involve variables in your program.
9651 @kindex info frame@r{, show the source language}
9652 Display the source language for this frame. This language becomes the
9653 working language if you use an identifier from this frame.
9654 @xref{Frame Info, ,Information about a Frame}, to identify the other
9655 information listed here.
9658 @kindex info source@r{, show the source language}
9659 Display the source language of this source file.
9660 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9661 information listed here.
9664 In unusual circumstances, you may have source files with extensions
9665 not in the standard list. You can then set the extension associated
9666 with a language explicitly:
9669 @item set extension-language @var{ext} @var{language}
9670 @kindex set extension-language
9671 Tell @value{GDBN} that source files with extension @var{ext} are to be
9672 assumed as written in the source language @var{language}.
9674 @item info extensions
9675 @kindex info extensions
9676 List all the filename extensions and the associated languages.
9680 @section Type and Range Checking
9683 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9684 checking are included, but they do not yet have any effect. This
9685 section documents the intended facilities.
9687 @c FIXME remove warning when type/range code added
9689 Some languages are designed to guard you against making seemingly common
9690 errors through a series of compile- and run-time checks. These include
9691 checking the type of arguments to functions and operators, and making
9692 sure mathematical overflows are caught at run time. Checks such as
9693 these help to ensure a program's correctness once it has been compiled
9694 by eliminating type mismatches, and providing active checks for range
9695 errors when your program is running.
9697 @value{GDBN} can check for conditions like the above if you wish.
9698 Although @value{GDBN} does not check the statements in your program,
9699 it can check expressions entered directly into @value{GDBN} for
9700 evaluation via the @code{print} command, for example. As with the
9701 working language, @value{GDBN} can also decide whether or not to check
9702 automatically based on your program's source language.
9703 @xref{Supported Languages, ,Supported Languages}, for the default
9704 settings of supported languages.
9707 * Type Checking:: An overview of type checking
9708 * Range Checking:: An overview of range checking
9711 @cindex type checking
9712 @cindex checks, type
9714 @subsection An Overview of Type Checking
9716 Some languages, such as Modula-2, are strongly typed, meaning that the
9717 arguments to operators and functions have to be of the correct type,
9718 otherwise an error occurs. These checks prevent type mismatch
9719 errors from ever causing any run-time problems. For example,
9727 The second example fails because the @code{CARDINAL} 1 is not
9728 type-compatible with the @code{REAL} 2.3.
9730 For the expressions you use in @value{GDBN} commands, you can tell the
9731 @value{GDBN} type checker to skip checking;
9732 to treat any mismatches as errors and abandon the expression;
9733 or to only issue warnings when type mismatches occur,
9734 but evaluate the expression anyway. When you choose the last of
9735 these, @value{GDBN} evaluates expressions like the second example above, but
9736 also issues a warning.
9738 Even if you turn type checking off, there may be other reasons
9739 related to type that prevent @value{GDBN} from evaluating an expression.
9740 For instance, @value{GDBN} does not know how to add an @code{int} and
9741 a @code{struct foo}. These particular type errors have nothing to do
9742 with the language in use, and usually arise from expressions, such as
9743 the one described above, which make little sense to evaluate anyway.
9745 Each language defines to what degree it is strict about type. For
9746 instance, both Modula-2 and C require the arguments to arithmetical
9747 operators to be numbers. In C, enumerated types and pointers can be
9748 represented as numbers, so that they are valid arguments to mathematical
9749 operators. @xref{Supported Languages, ,Supported Languages}, for further
9750 details on specific languages.
9752 @value{GDBN} provides some additional commands for controlling the type checker:
9754 @kindex set check type
9755 @kindex show check type
9757 @item set check type auto
9758 Set type checking on or off based on the current working language.
9759 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9762 @item set check type on
9763 @itemx set check type off
9764 Set type checking on or off, overriding the default setting for the
9765 current working language. Issue a warning if the setting does not
9766 match the language default. If any type mismatches occur in
9767 evaluating an expression while type checking is on, @value{GDBN} prints a
9768 message and aborts evaluation of the expression.
9770 @item set check type warn
9771 Cause the type checker to issue warnings, but to always attempt to
9772 evaluate the expression. Evaluating the expression may still
9773 be impossible for other reasons. For example, @value{GDBN} cannot add
9774 numbers and structures.
9777 Show the current setting of the type checker, and whether or not @value{GDBN}
9778 is setting it automatically.
9781 @cindex range checking
9782 @cindex checks, range
9783 @node Range Checking
9784 @subsection An Overview of Range Checking
9786 In some languages (such as Modula-2), it is an error to exceed the
9787 bounds of a type; this is enforced with run-time checks. Such range
9788 checking is meant to ensure program correctness by making sure
9789 computations do not overflow, or indices on an array element access do
9790 not exceed the bounds of the array.
9792 For expressions you use in @value{GDBN} commands, you can tell
9793 @value{GDBN} to treat range errors in one of three ways: ignore them,
9794 always treat them as errors and abandon the expression, or issue
9795 warnings but evaluate the expression anyway.
9797 A range error can result from numerical overflow, from exceeding an
9798 array index bound, or when you type a constant that is not a member
9799 of any type. Some languages, however, do not treat overflows as an
9800 error. In many implementations of C, mathematical overflow causes the
9801 result to ``wrap around'' to lower values---for example, if @var{m} is
9802 the largest integer value, and @var{s} is the smallest, then
9805 @var{m} + 1 @result{} @var{s}
9808 This, too, is specific to individual languages, and in some cases
9809 specific to individual compilers or machines. @xref{Supported Languages, ,
9810 Supported Languages}, for further details on specific languages.
9812 @value{GDBN} provides some additional commands for controlling the range checker:
9814 @kindex set check range
9815 @kindex show check range
9817 @item set check range auto
9818 Set range checking on or off based on the current working language.
9819 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9822 @item set check range on
9823 @itemx set check range off
9824 Set range checking on or off, overriding the default setting for the
9825 current working language. A warning is issued if the setting does not
9826 match the language default. If a range error occurs and range checking is on,
9827 then a message is printed and evaluation of the expression is aborted.
9829 @item set check range warn
9830 Output messages when the @value{GDBN} range checker detects a range error,
9831 but attempt to evaluate the expression anyway. Evaluating the
9832 expression may still be impossible for other reasons, such as accessing
9833 memory that the process does not own (a typical example from many Unix
9837 Show the current setting of the range checker, and whether or not it is
9838 being set automatically by @value{GDBN}.
9841 @node Supported Languages
9842 @section Supported Languages
9844 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9845 assembly, Modula-2, and Ada.
9846 @c This is false ...
9847 Some @value{GDBN} features may be used in expressions regardless of the
9848 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9849 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9850 ,Expressions}) can be used with the constructs of any supported
9853 The following sections detail to what degree each source language is
9854 supported by @value{GDBN}. These sections are not meant to be language
9855 tutorials or references, but serve only as a reference guide to what the
9856 @value{GDBN} expression parser accepts, and what input and output
9857 formats should look like for different languages. There are many good
9858 books written on each of these languages; please look to these for a
9859 language reference or tutorial.
9863 * Objective-C:: Objective-C
9866 * Modula-2:: Modula-2
9871 @subsection C and C@t{++}
9873 @cindex C and C@t{++}
9874 @cindex expressions in C or C@t{++}
9876 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9877 to both languages. Whenever this is the case, we discuss those languages
9881 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9882 @cindex @sc{gnu} C@t{++}
9883 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9884 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9885 effectively, you must compile your C@t{++} programs with a supported
9886 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9887 compiler (@code{aCC}).
9889 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9890 format; if it doesn't work on your system, try the stabs+ debugging
9891 format. You can select those formats explicitly with the @code{g++}
9892 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9893 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9894 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9897 * C Operators:: C and C@t{++} operators
9898 * C Constants:: C and C@t{++} constants
9899 * C Plus Plus Expressions:: C@t{++} expressions
9900 * C Defaults:: Default settings for C and C@t{++}
9901 * C Checks:: C and C@t{++} type and range checks
9902 * Debugging C:: @value{GDBN} and C
9903 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9904 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9908 @subsubsection C and C@t{++} Operators
9910 @cindex C and C@t{++} operators
9912 Operators must be defined on values of specific types. For instance,
9913 @code{+} is defined on numbers, but not on structures. Operators are
9914 often defined on groups of types.
9916 For the purposes of C and C@t{++}, the following definitions hold:
9921 @emph{Integral types} include @code{int} with any of its storage-class
9922 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9925 @emph{Floating-point types} include @code{float}, @code{double}, and
9926 @code{long double} (if supported by the target platform).
9929 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9932 @emph{Scalar types} include all of the above.
9937 The following operators are supported. They are listed here
9938 in order of increasing precedence:
9942 The comma or sequencing operator. Expressions in a comma-separated list
9943 are evaluated from left to right, with the result of the entire
9944 expression being the last expression evaluated.
9947 Assignment. The value of an assignment expression is the value
9948 assigned. Defined on scalar types.
9951 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9952 and translated to @w{@code{@var{a} = @var{a op b}}}.
9953 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9954 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9955 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9958 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9959 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9963 Logical @sc{or}. Defined on integral types.
9966 Logical @sc{and}. Defined on integral types.
9969 Bitwise @sc{or}. Defined on integral types.
9972 Bitwise exclusive-@sc{or}. Defined on integral types.
9975 Bitwise @sc{and}. Defined on integral types.
9978 Equality and inequality. Defined on scalar types. The value of these
9979 expressions is 0 for false and non-zero for true.
9981 @item <@r{, }>@r{, }<=@r{, }>=
9982 Less than, greater than, less than or equal, greater than or equal.
9983 Defined on scalar types. The value of these expressions is 0 for false
9984 and non-zero for true.
9987 left shift, and right shift. Defined on integral types.
9990 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9993 Addition and subtraction. Defined on integral types, floating-point types and
9996 @item *@r{, }/@r{, }%
9997 Multiplication, division, and modulus. Multiplication and division are
9998 defined on integral and floating-point types. Modulus is defined on
10002 Increment and decrement. When appearing before a variable, the
10003 operation is performed before the variable is used in an expression;
10004 when appearing after it, the variable's value is used before the
10005 operation takes place.
10008 Pointer dereferencing. Defined on pointer types. Same precedence as
10012 Address operator. Defined on variables. Same precedence as @code{++}.
10014 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10015 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10016 to examine the address
10017 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10021 Negative. Defined on integral and floating-point types. Same
10022 precedence as @code{++}.
10025 Logical negation. Defined on integral types. Same precedence as
10029 Bitwise complement operator. Defined on integral types. Same precedence as
10034 Structure member, and pointer-to-structure member. For convenience,
10035 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10036 pointer based on the stored type information.
10037 Defined on @code{struct} and @code{union} data.
10040 Dereferences of pointers to members.
10043 Array indexing. @code{@var{a}[@var{i}]} is defined as
10044 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10047 Function parameter list. Same precedence as @code{->}.
10050 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10051 and @code{class} types.
10054 Doubled colons also represent the @value{GDBN} scope operator
10055 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10059 If an operator is redefined in the user code, @value{GDBN} usually
10060 attempts to invoke the redefined version instead of using the operator's
10061 predefined meaning.
10064 @subsubsection C and C@t{++} Constants
10066 @cindex C and C@t{++} constants
10068 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10073 Integer constants are a sequence of digits. Octal constants are
10074 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10075 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10076 @samp{l}, specifying that the constant should be treated as a
10080 Floating point constants are a sequence of digits, followed by a decimal
10081 point, followed by a sequence of digits, and optionally followed by an
10082 exponent. An exponent is of the form:
10083 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10084 sequence of digits. The @samp{+} is optional for positive exponents.
10085 A floating-point constant may also end with a letter @samp{f} or
10086 @samp{F}, specifying that the constant should be treated as being of
10087 the @code{float} (as opposed to the default @code{double}) type; or with
10088 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10092 Enumerated constants consist of enumerated identifiers, or their
10093 integral equivalents.
10096 Character constants are a single character surrounded by single quotes
10097 (@code{'}), or a number---the ordinal value of the corresponding character
10098 (usually its @sc{ascii} value). Within quotes, the single character may
10099 be represented by a letter or by @dfn{escape sequences}, which are of
10100 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10101 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10102 @samp{@var{x}} is a predefined special character---for example,
10103 @samp{\n} for newline.
10106 String constants are a sequence of character constants surrounded by
10107 double quotes (@code{"}). Any valid character constant (as described
10108 above) may appear. Double quotes within the string must be preceded by
10109 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10113 Pointer constants are an integral value. You can also write pointers
10114 to constants using the C operator @samp{&}.
10117 Array constants are comma-separated lists surrounded by braces @samp{@{}
10118 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10119 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10120 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10123 @node C Plus Plus Expressions
10124 @subsubsection C@t{++} Expressions
10126 @cindex expressions in C@t{++}
10127 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10129 @cindex debugging C@t{++} programs
10130 @cindex C@t{++} compilers
10131 @cindex debug formats and C@t{++}
10132 @cindex @value{NGCC} and C@t{++}
10134 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10135 proper compiler and the proper debug format. Currently, @value{GDBN}
10136 works best when debugging C@t{++} code that is compiled with
10137 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10138 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10139 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10140 stabs+ as their default debug format, so you usually don't need to
10141 specify a debug format explicitly. Other compilers and/or debug formats
10142 are likely to work badly or not at all when using @value{GDBN} to debug
10148 @cindex member functions
10150 Member function calls are allowed; you can use expressions like
10153 count = aml->GetOriginal(x, y)
10156 @vindex this@r{, inside C@t{++} member functions}
10157 @cindex namespace in C@t{++}
10159 While a member function is active (in the selected stack frame), your
10160 expressions have the same namespace available as the member function;
10161 that is, @value{GDBN} allows implicit references to the class instance
10162 pointer @code{this} following the same rules as C@t{++}.
10164 @cindex call overloaded functions
10165 @cindex overloaded functions, calling
10166 @cindex type conversions in C@t{++}
10168 You can call overloaded functions; @value{GDBN} resolves the function
10169 call to the right definition, with some restrictions. @value{GDBN} does not
10170 perform overload resolution involving user-defined type conversions,
10171 calls to constructors, or instantiations of templates that do not exist
10172 in the program. It also cannot handle ellipsis argument lists or
10175 It does perform integral conversions and promotions, floating-point
10176 promotions, arithmetic conversions, pointer conversions, conversions of
10177 class objects to base classes, and standard conversions such as those of
10178 functions or arrays to pointers; it requires an exact match on the
10179 number of function arguments.
10181 Overload resolution is always performed, unless you have specified
10182 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10183 ,@value{GDBN} Features for C@t{++}}.
10185 You must specify @code{set overload-resolution off} in order to use an
10186 explicit function signature to call an overloaded function, as in
10188 p 'foo(char,int)'('x', 13)
10191 The @value{GDBN} command-completion facility can simplify this;
10192 see @ref{Completion, ,Command Completion}.
10194 @cindex reference declarations
10196 @value{GDBN} understands variables declared as C@t{++} references; you can use
10197 them in expressions just as you do in C@t{++} source---they are automatically
10200 In the parameter list shown when @value{GDBN} displays a frame, the values of
10201 reference variables are not displayed (unlike other variables); this
10202 avoids clutter, since references are often used for large structures.
10203 The @emph{address} of a reference variable is always shown, unless
10204 you have specified @samp{set print address off}.
10207 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10208 expressions can use it just as expressions in your program do. Since
10209 one scope may be defined in another, you can use @code{::} repeatedly if
10210 necessary, for example in an expression like
10211 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10212 resolving name scope by reference to source files, in both C and C@t{++}
10213 debugging (@pxref{Variables, ,Program Variables}).
10216 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10217 calling virtual functions correctly, printing out virtual bases of
10218 objects, calling functions in a base subobject, casting objects, and
10219 invoking user-defined operators.
10222 @subsubsection C and C@t{++} Defaults
10224 @cindex C and C@t{++} defaults
10226 If you allow @value{GDBN} to set type and range checking automatically, they
10227 both default to @code{off} whenever the working language changes to
10228 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10229 selects the working language.
10231 If you allow @value{GDBN} to set the language automatically, it
10232 recognizes source files whose names end with @file{.c}, @file{.C}, or
10233 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10234 these files, it sets the working language to C or C@t{++}.
10235 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10236 for further details.
10238 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10239 @c unimplemented. If (b) changes, it might make sense to let this node
10240 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10243 @subsubsection C and C@t{++} Type and Range Checks
10245 @cindex C and C@t{++} checks
10247 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10248 is not used. However, if you turn type checking on, @value{GDBN}
10249 considers two variables type equivalent if:
10253 The two variables are structured and have the same structure, union, or
10257 The two variables have the same type name, or types that have been
10258 declared equivalent through @code{typedef}.
10261 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10264 The two @code{struct}, @code{union}, or @code{enum} variables are
10265 declared in the same declaration. (Note: this may not be true for all C
10270 Range checking, if turned on, is done on mathematical operations. Array
10271 indices are not checked, since they are often used to index a pointer
10272 that is not itself an array.
10275 @subsubsection @value{GDBN} and C
10277 The @code{set print union} and @code{show print union} commands apply to
10278 the @code{union} type. When set to @samp{on}, any @code{union} that is
10279 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10280 appears as @samp{@{...@}}.
10282 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10283 with pointers and a memory allocation function. @xref{Expressions,
10286 @node Debugging C Plus Plus
10287 @subsubsection @value{GDBN} Features for C@t{++}
10289 @cindex commands for C@t{++}
10291 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10292 designed specifically for use with C@t{++}. Here is a summary:
10295 @cindex break in overloaded functions
10296 @item @r{breakpoint menus}
10297 When you want a breakpoint in a function whose name is overloaded,
10298 @value{GDBN} has the capability to display a menu of possible breakpoint
10299 locations to help you specify which function definition you want.
10300 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10302 @cindex overloading in C@t{++}
10303 @item rbreak @var{regex}
10304 Setting breakpoints using regular expressions is helpful for setting
10305 breakpoints on overloaded functions that are not members of any special
10307 @xref{Set Breaks, ,Setting Breakpoints}.
10309 @cindex C@t{++} exception handling
10312 Debug C@t{++} exception handling using these commands. @xref{Set
10313 Catchpoints, , Setting Catchpoints}.
10315 @cindex inheritance
10316 @item ptype @var{typename}
10317 Print inheritance relationships as well as other information for type
10319 @xref{Symbols, ,Examining the Symbol Table}.
10321 @cindex C@t{++} symbol display
10322 @item set print demangle
10323 @itemx show print demangle
10324 @itemx set print asm-demangle
10325 @itemx show print asm-demangle
10326 Control whether C@t{++} symbols display in their source form, both when
10327 displaying code as C@t{++} source and when displaying disassemblies.
10328 @xref{Print Settings, ,Print Settings}.
10330 @item set print object
10331 @itemx show print object
10332 Choose whether to print derived (actual) or declared types of objects.
10333 @xref{Print Settings, ,Print Settings}.
10335 @item set print vtbl
10336 @itemx show print vtbl
10337 Control the format for printing virtual function tables.
10338 @xref{Print Settings, ,Print Settings}.
10339 (The @code{vtbl} commands do not work on programs compiled with the HP
10340 ANSI C@t{++} compiler (@code{aCC}).)
10342 @kindex set overload-resolution
10343 @cindex overloaded functions, overload resolution
10344 @item set overload-resolution on
10345 Enable overload resolution for C@t{++} expression evaluation. The default
10346 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10347 and searches for a function whose signature matches the argument types,
10348 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10349 Expressions, ,C@t{++} Expressions}, for details).
10350 If it cannot find a match, it emits a message.
10352 @item set overload-resolution off
10353 Disable overload resolution for C@t{++} expression evaluation. For
10354 overloaded functions that are not class member functions, @value{GDBN}
10355 chooses the first function of the specified name that it finds in the
10356 symbol table, whether or not its arguments are of the correct type. For
10357 overloaded functions that are class member functions, @value{GDBN}
10358 searches for a function whose signature @emph{exactly} matches the
10361 @kindex show overload-resolution
10362 @item show overload-resolution
10363 Show the current setting of overload resolution.
10365 @item @r{Overloaded symbol names}
10366 You can specify a particular definition of an overloaded symbol, using
10367 the same notation that is used to declare such symbols in C@t{++}: type
10368 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10369 also use the @value{GDBN} command-line word completion facilities to list the
10370 available choices, or to finish the type list for you.
10371 @xref{Completion,, Command Completion}, for details on how to do this.
10374 @node Decimal Floating Point
10375 @subsubsection Decimal Floating Point format
10376 @cindex decimal floating point format
10378 @value{GDBN} can examine, set and perform computations with numbers in
10379 decimal floating point format, which in the C language correspond to the
10380 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10381 specified by the extension to support decimal floating-point arithmetic.
10383 There are two encodings in use, depending on the architecture: BID (Binary
10384 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10385 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10388 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10389 to manipulate decimal floating point numbers, it is not possible to convert
10390 (using a cast, for example) integers wider than 32-bit to decimal float.
10392 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10393 point computations, error checking in decimal float operations ignores
10394 underflow, overflow and divide by zero exceptions.
10396 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10397 to inspect @code{_Decimal128} values stored in floating point registers. See
10398 @ref{PowerPC,,PowerPC} for more details.
10401 @subsection Objective-C
10403 @cindex Objective-C
10404 This section provides information about some commands and command
10405 options that are useful for debugging Objective-C code. See also
10406 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10407 few more commands specific to Objective-C support.
10410 * Method Names in Commands::
10411 * The Print Command with Objective-C::
10414 @node Method Names in Commands
10415 @subsubsection Method Names in Commands
10417 The following commands have been extended to accept Objective-C method
10418 names as line specifications:
10420 @kindex clear@r{, and Objective-C}
10421 @kindex break@r{, and Objective-C}
10422 @kindex info line@r{, and Objective-C}
10423 @kindex jump@r{, and Objective-C}
10424 @kindex list@r{, and Objective-C}
10428 @item @code{info line}
10433 A fully qualified Objective-C method name is specified as
10436 -[@var{Class} @var{methodName}]
10439 where the minus sign is used to indicate an instance method and a
10440 plus sign (not shown) is used to indicate a class method. The class
10441 name @var{Class} and method name @var{methodName} are enclosed in
10442 brackets, similar to the way messages are specified in Objective-C
10443 source code. For example, to set a breakpoint at the @code{create}
10444 instance method of class @code{Fruit} in the program currently being
10448 break -[Fruit create]
10451 To list ten program lines around the @code{initialize} class method,
10455 list +[NSText initialize]
10458 In the current version of @value{GDBN}, the plus or minus sign is
10459 required. In future versions of @value{GDBN}, the plus or minus
10460 sign will be optional, but you can use it to narrow the search. It
10461 is also possible to specify just a method name:
10467 You must specify the complete method name, including any colons. If
10468 your program's source files contain more than one @code{create} method,
10469 you'll be presented with a numbered list of classes that implement that
10470 method. Indicate your choice by number, or type @samp{0} to exit if
10473 As another example, to clear a breakpoint established at the
10474 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10477 clear -[NSWindow makeKeyAndOrderFront:]
10480 @node The Print Command with Objective-C
10481 @subsubsection The Print Command With Objective-C
10482 @cindex Objective-C, print objects
10483 @kindex print-object
10484 @kindex po @r{(@code{print-object})}
10486 The print command has also been extended to accept methods. For example:
10489 print -[@var{object} hash]
10492 @cindex print an Objective-C object description
10493 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10495 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10496 and print the result. Also, an additional command has been added,
10497 @code{print-object} or @code{po} for short, which is meant to print
10498 the description of an object. However, this command may only work
10499 with certain Objective-C libraries that have a particular hook
10500 function, @code{_NSPrintForDebugger}, defined.
10503 @subsection Fortran
10504 @cindex Fortran-specific support in @value{GDBN}
10506 @value{GDBN} can be used to debug programs written in Fortran, but it
10507 currently supports only the features of Fortran 77 language.
10509 @cindex trailing underscore, in Fortran symbols
10510 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10511 among them) append an underscore to the names of variables and
10512 functions. When you debug programs compiled by those compilers, you
10513 will need to refer to variables and functions with a trailing
10517 * Fortran Operators:: Fortran operators and expressions
10518 * Fortran Defaults:: Default settings for Fortran
10519 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10522 @node Fortran Operators
10523 @subsubsection Fortran Operators and Expressions
10525 @cindex Fortran operators and expressions
10527 Operators must be defined on values of specific types. For instance,
10528 @code{+} is defined on numbers, but not on characters or other non-
10529 arithmetic types. Operators are often defined on groups of types.
10533 The exponentiation operator. It raises the first operand to the power
10537 The range operator. Normally used in the form of array(low:high) to
10538 represent a section of array.
10541 The access component operator. Normally used to access elements in derived
10542 types. Also suitable for unions. As unions aren't part of regular Fortran,
10543 this can only happen when accessing a register that uses a gdbarch-defined
10547 @node Fortran Defaults
10548 @subsubsection Fortran Defaults
10550 @cindex Fortran Defaults
10552 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10553 default uses case-insensitive matches for Fortran symbols. You can
10554 change that with the @samp{set case-insensitive} command, see
10555 @ref{Symbols}, for the details.
10557 @node Special Fortran Commands
10558 @subsubsection Special Fortran Commands
10560 @cindex Special Fortran commands
10562 @value{GDBN} has some commands to support Fortran-specific features,
10563 such as displaying common blocks.
10566 @cindex @code{COMMON} blocks, Fortran
10567 @kindex info common
10568 @item info common @r{[}@var{common-name}@r{]}
10569 This command prints the values contained in the Fortran @code{COMMON}
10570 block whose name is @var{common-name}. With no argument, the names of
10571 all @code{COMMON} blocks visible at the current program location are
10578 @cindex Pascal support in @value{GDBN}, limitations
10579 Debugging Pascal programs which use sets, subranges, file variables, or
10580 nested functions does not currently work. @value{GDBN} does not support
10581 entering expressions, printing values, or similar features using Pascal
10584 The Pascal-specific command @code{set print pascal_static-members}
10585 controls whether static members of Pascal objects are displayed.
10586 @xref{Print Settings, pascal_static-members}.
10589 @subsection Modula-2
10591 @cindex Modula-2, @value{GDBN} support
10593 The extensions made to @value{GDBN} to support Modula-2 only support
10594 output from the @sc{gnu} Modula-2 compiler (which is currently being
10595 developed). Other Modula-2 compilers are not currently supported, and
10596 attempting to debug executables produced by them is most likely
10597 to give an error as @value{GDBN} reads in the executable's symbol
10600 @cindex expressions in Modula-2
10602 * M2 Operators:: Built-in operators
10603 * Built-In Func/Proc:: Built-in functions and procedures
10604 * M2 Constants:: Modula-2 constants
10605 * M2 Types:: Modula-2 types
10606 * M2 Defaults:: Default settings for Modula-2
10607 * Deviations:: Deviations from standard Modula-2
10608 * M2 Checks:: Modula-2 type and range checks
10609 * M2 Scope:: The scope operators @code{::} and @code{.}
10610 * GDB/M2:: @value{GDBN} and Modula-2
10614 @subsubsection Operators
10615 @cindex Modula-2 operators
10617 Operators must be defined on values of specific types. For instance,
10618 @code{+} is defined on numbers, but not on structures. Operators are
10619 often defined on groups of types. For the purposes of Modula-2, the
10620 following definitions hold:
10625 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10629 @emph{Character types} consist of @code{CHAR} and its subranges.
10632 @emph{Floating-point types} consist of @code{REAL}.
10635 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10639 @emph{Scalar types} consist of all of the above.
10642 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10645 @emph{Boolean types} consist of @code{BOOLEAN}.
10649 The following operators are supported, and appear in order of
10650 increasing precedence:
10654 Function argument or array index separator.
10657 Assignment. The value of @var{var} @code{:=} @var{value} is
10661 Less than, greater than on integral, floating-point, or enumerated
10665 Less than or equal to, greater than or equal to
10666 on integral, floating-point and enumerated types, or set inclusion on
10667 set types. Same precedence as @code{<}.
10669 @item =@r{, }<>@r{, }#
10670 Equality and two ways of expressing inequality, valid on scalar types.
10671 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10672 available for inequality, since @code{#} conflicts with the script
10676 Set membership. Defined on set types and the types of their members.
10677 Same precedence as @code{<}.
10680 Boolean disjunction. Defined on boolean types.
10683 Boolean conjunction. Defined on boolean types.
10686 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10689 Addition and subtraction on integral and floating-point types, or union
10690 and difference on set types.
10693 Multiplication on integral and floating-point types, or set intersection
10697 Division on floating-point types, or symmetric set difference on set
10698 types. Same precedence as @code{*}.
10701 Integer division and remainder. Defined on integral types. Same
10702 precedence as @code{*}.
10705 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10708 Pointer dereferencing. Defined on pointer types.
10711 Boolean negation. Defined on boolean types. Same precedence as
10715 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10716 precedence as @code{^}.
10719 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10722 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10726 @value{GDBN} and Modula-2 scope operators.
10730 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10731 treats the use of the operator @code{IN}, or the use of operators
10732 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10733 @code{<=}, and @code{>=} on sets as an error.
10737 @node Built-In Func/Proc
10738 @subsubsection Built-in Functions and Procedures
10739 @cindex Modula-2 built-ins
10741 Modula-2 also makes available several built-in procedures and functions.
10742 In describing these, the following metavariables are used:
10747 represents an @code{ARRAY} variable.
10750 represents a @code{CHAR} constant or variable.
10753 represents a variable or constant of integral type.
10756 represents an identifier that belongs to a set. Generally used in the
10757 same function with the metavariable @var{s}. The type of @var{s} should
10758 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10761 represents a variable or constant of integral or floating-point type.
10764 represents a variable or constant of floating-point type.
10770 represents a variable.
10773 represents a variable or constant of one of many types. See the
10774 explanation of the function for details.
10777 All Modula-2 built-in procedures also return a result, described below.
10781 Returns the absolute value of @var{n}.
10784 If @var{c} is a lower case letter, it returns its upper case
10785 equivalent, otherwise it returns its argument.
10788 Returns the character whose ordinal value is @var{i}.
10791 Decrements the value in the variable @var{v} by one. Returns the new value.
10793 @item DEC(@var{v},@var{i})
10794 Decrements the value in the variable @var{v} by @var{i}. Returns the
10797 @item EXCL(@var{m},@var{s})
10798 Removes the element @var{m} from the set @var{s}. Returns the new
10801 @item FLOAT(@var{i})
10802 Returns the floating point equivalent of the integer @var{i}.
10804 @item HIGH(@var{a})
10805 Returns the index of the last member of @var{a}.
10808 Increments the value in the variable @var{v} by one. Returns the new value.
10810 @item INC(@var{v},@var{i})
10811 Increments the value in the variable @var{v} by @var{i}. Returns the
10814 @item INCL(@var{m},@var{s})
10815 Adds the element @var{m} to the set @var{s} if it is not already
10816 there. Returns the new set.
10819 Returns the maximum value of the type @var{t}.
10822 Returns the minimum value of the type @var{t}.
10825 Returns boolean TRUE if @var{i} is an odd number.
10828 Returns the ordinal value of its argument. For example, the ordinal
10829 value of a character is its @sc{ascii} value (on machines supporting the
10830 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10831 integral, character and enumerated types.
10833 @item SIZE(@var{x})
10834 Returns the size of its argument. @var{x} can be a variable or a type.
10836 @item TRUNC(@var{r})
10837 Returns the integral part of @var{r}.
10839 @item TSIZE(@var{x})
10840 Returns the size of its argument. @var{x} can be a variable or a type.
10842 @item VAL(@var{t},@var{i})
10843 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10847 @emph{Warning:} Sets and their operations are not yet supported, so
10848 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10852 @cindex Modula-2 constants
10854 @subsubsection Constants
10856 @value{GDBN} allows you to express the constants of Modula-2 in the following
10862 Integer constants are simply a sequence of digits. When used in an
10863 expression, a constant is interpreted to be type-compatible with the
10864 rest of the expression. Hexadecimal integers are specified by a
10865 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10868 Floating point constants appear as a sequence of digits, followed by a
10869 decimal point and another sequence of digits. An optional exponent can
10870 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10871 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10872 digits of the floating point constant must be valid decimal (base 10)
10876 Character constants consist of a single character enclosed by a pair of
10877 like quotes, either single (@code{'}) or double (@code{"}). They may
10878 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10879 followed by a @samp{C}.
10882 String constants consist of a sequence of characters enclosed by a
10883 pair of like quotes, either single (@code{'}) or double (@code{"}).
10884 Escape sequences in the style of C are also allowed. @xref{C
10885 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10889 Enumerated constants consist of an enumerated identifier.
10892 Boolean constants consist of the identifiers @code{TRUE} and
10896 Pointer constants consist of integral values only.
10899 Set constants are not yet supported.
10903 @subsubsection Modula-2 Types
10904 @cindex Modula-2 types
10906 Currently @value{GDBN} can print the following data types in Modula-2
10907 syntax: array types, record types, set types, pointer types, procedure
10908 types, enumerated types, subrange types and base types. You can also
10909 print the contents of variables declared using these type.
10910 This section gives a number of simple source code examples together with
10911 sample @value{GDBN} sessions.
10913 The first example contains the following section of code:
10922 and you can request @value{GDBN} to interrogate the type and value of
10923 @code{r} and @code{s}.
10926 (@value{GDBP}) print s
10928 (@value{GDBP}) ptype s
10930 (@value{GDBP}) print r
10932 (@value{GDBP}) ptype r
10937 Likewise if your source code declares @code{s} as:
10941 s: SET ['A'..'Z'] ;
10945 then you may query the type of @code{s} by:
10948 (@value{GDBP}) ptype s
10949 type = SET ['A'..'Z']
10953 Note that at present you cannot interactively manipulate set
10954 expressions using the debugger.
10956 The following example shows how you might declare an array in Modula-2
10957 and how you can interact with @value{GDBN} to print its type and contents:
10961 s: ARRAY [-10..10] OF CHAR ;
10965 (@value{GDBP}) ptype s
10966 ARRAY [-10..10] OF CHAR
10969 Note that the array handling is not yet complete and although the type
10970 is printed correctly, expression handling still assumes that all
10971 arrays have a lower bound of zero and not @code{-10} as in the example
10974 Here are some more type related Modula-2 examples:
10978 colour = (blue, red, yellow, green) ;
10979 t = [blue..yellow] ;
10987 The @value{GDBN} interaction shows how you can query the data type
10988 and value of a variable.
10991 (@value{GDBP}) print s
10993 (@value{GDBP}) ptype t
10994 type = [blue..yellow]
10998 In this example a Modula-2 array is declared and its contents
10999 displayed. Observe that the contents are written in the same way as
11000 their @code{C} counterparts.
11004 s: ARRAY [1..5] OF CARDINAL ;
11010 (@value{GDBP}) print s
11011 $1 = @{1, 0, 0, 0, 0@}
11012 (@value{GDBP}) ptype s
11013 type = ARRAY [1..5] OF CARDINAL
11016 The Modula-2 language interface to @value{GDBN} also understands
11017 pointer types as shown in this example:
11021 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11028 and you can request that @value{GDBN} describes the type of @code{s}.
11031 (@value{GDBP}) ptype s
11032 type = POINTER TO ARRAY [1..5] OF CARDINAL
11035 @value{GDBN} handles compound types as we can see in this example.
11036 Here we combine array types, record types, pointer types and subrange
11047 myarray = ARRAY myrange OF CARDINAL ;
11048 myrange = [-2..2] ;
11050 s: POINTER TO ARRAY myrange OF foo ;
11054 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11058 (@value{GDBP}) ptype s
11059 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11062 f3 : ARRAY [-2..2] OF CARDINAL;
11067 @subsubsection Modula-2 Defaults
11068 @cindex Modula-2 defaults
11070 If type and range checking are set automatically by @value{GDBN}, they
11071 both default to @code{on} whenever the working language changes to
11072 Modula-2. This happens regardless of whether you or @value{GDBN}
11073 selected the working language.
11075 If you allow @value{GDBN} to set the language automatically, then entering
11076 code compiled from a file whose name ends with @file{.mod} sets the
11077 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11078 Infer the Source Language}, for further details.
11081 @subsubsection Deviations from Standard Modula-2
11082 @cindex Modula-2, deviations from
11084 A few changes have been made to make Modula-2 programs easier to debug.
11085 This is done primarily via loosening its type strictness:
11089 Unlike in standard Modula-2, pointer constants can be formed by
11090 integers. This allows you to modify pointer variables during
11091 debugging. (In standard Modula-2, the actual address contained in a
11092 pointer variable is hidden from you; it can only be modified
11093 through direct assignment to another pointer variable or expression that
11094 returned a pointer.)
11097 C escape sequences can be used in strings and characters to represent
11098 non-printable characters. @value{GDBN} prints out strings with these
11099 escape sequences embedded. Single non-printable characters are
11100 printed using the @samp{CHR(@var{nnn})} format.
11103 The assignment operator (@code{:=}) returns the value of its right-hand
11107 All built-in procedures both modify @emph{and} return their argument.
11111 @subsubsection Modula-2 Type and Range Checks
11112 @cindex Modula-2 checks
11115 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11118 @c FIXME remove warning when type/range checks added
11120 @value{GDBN} considers two Modula-2 variables type equivalent if:
11124 They are of types that have been declared equivalent via a @code{TYPE
11125 @var{t1} = @var{t2}} statement
11128 They have been declared on the same line. (Note: This is true of the
11129 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11132 As long as type checking is enabled, any attempt to combine variables
11133 whose types are not equivalent is an error.
11135 Range checking is done on all mathematical operations, assignment, array
11136 index bounds, and all built-in functions and procedures.
11139 @subsubsection The Scope Operators @code{::} and @code{.}
11141 @cindex @code{.}, Modula-2 scope operator
11142 @cindex colon, doubled as scope operator
11144 @vindex colon-colon@r{, in Modula-2}
11145 @c Info cannot handle :: but TeX can.
11148 @vindex ::@r{, in Modula-2}
11151 There are a few subtle differences between the Modula-2 scope operator
11152 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11157 @var{module} . @var{id}
11158 @var{scope} :: @var{id}
11162 where @var{scope} is the name of a module or a procedure,
11163 @var{module} the name of a module, and @var{id} is any declared
11164 identifier within your program, except another module.
11166 Using the @code{::} operator makes @value{GDBN} search the scope
11167 specified by @var{scope} for the identifier @var{id}. If it is not
11168 found in the specified scope, then @value{GDBN} searches all scopes
11169 enclosing the one specified by @var{scope}.
11171 Using the @code{.} operator makes @value{GDBN} search the current scope for
11172 the identifier specified by @var{id} that was imported from the
11173 definition module specified by @var{module}. With this operator, it is
11174 an error if the identifier @var{id} was not imported from definition
11175 module @var{module}, or if @var{id} is not an identifier in
11179 @subsubsection @value{GDBN} and Modula-2
11181 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11182 Five subcommands of @code{set print} and @code{show print} apply
11183 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11184 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11185 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11186 analogue in Modula-2.
11188 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11189 with any language, is not useful with Modula-2. Its
11190 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11191 created in Modula-2 as they can in C or C@t{++}. However, because an
11192 address can be specified by an integral constant, the construct
11193 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11195 @cindex @code{#} in Modula-2
11196 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11197 interpreted as the beginning of a comment. Use @code{<>} instead.
11203 The extensions made to @value{GDBN} for Ada only support
11204 output from the @sc{gnu} Ada (GNAT) compiler.
11205 Other Ada compilers are not currently supported, and
11206 attempting to debug executables produced by them is most likely
11210 @cindex expressions in Ada
11212 * Ada Mode Intro:: General remarks on the Ada syntax
11213 and semantics supported by Ada mode
11215 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11216 * Additions to Ada:: Extensions of the Ada expression syntax.
11217 * Stopping Before Main Program:: Debugging the program during elaboration.
11218 * Ada Tasks:: Listing and setting breakpoints in tasks.
11219 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11220 * Ada Glitches:: Known peculiarities of Ada mode.
11223 @node Ada Mode Intro
11224 @subsubsection Introduction
11225 @cindex Ada mode, general
11227 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11228 syntax, with some extensions.
11229 The philosophy behind the design of this subset is
11233 That @value{GDBN} should provide basic literals and access to operations for
11234 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11235 leaving more sophisticated computations to subprograms written into the
11236 program (which therefore may be called from @value{GDBN}).
11239 That type safety and strict adherence to Ada language restrictions
11240 are not particularly important to the @value{GDBN} user.
11243 That brevity is important to the @value{GDBN} user.
11246 Thus, for brevity, the debugger acts as if all names declared in
11247 user-written packages are directly visible, even if they are not visible
11248 according to Ada rules, thus making it unnecessary to fully qualify most
11249 names with their packages, regardless of context. Where this causes
11250 ambiguity, @value{GDBN} asks the user's intent.
11252 The debugger will start in Ada mode if it detects an Ada main program.
11253 As for other languages, it will enter Ada mode when stopped in a program that
11254 was translated from an Ada source file.
11256 While in Ada mode, you may use `@t{--}' for comments. This is useful
11257 mostly for documenting command files. The standard @value{GDBN} comment
11258 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11259 middle (to allow based literals).
11261 The debugger supports limited overloading. Given a subprogram call in which
11262 the function symbol has multiple definitions, it will use the number of
11263 actual parameters and some information about their types to attempt to narrow
11264 the set of definitions. It also makes very limited use of context, preferring
11265 procedures to functions in the context of the @code{call} command, and
11266 functions to procedures elsewhere.
11268 @node Omissions from Ada
11269 @subsubsection Omissions from Ada
11270 @cindex Ada, omissions from
11272 Here are the notable omissions from the subset:
11276 Only a subset of the attributes are supported:
11280 @t{'First}, @t{'Last}, and @t{'Length}
11281 on array objects (not on types and subtypes).
11284 @t{'Min} and @t{'Max}.
11287 @t{'Pos} and @t{'Val}.
11293 @t{'Range} on array objects (not subtypes), but only as the right
11294 operand of the membership (@code{in}) operator.
11297 @t{'Access}, @t{'Unchecked_Access}, and
11298 @t{'Unrestricted_Access} (a GNAT extension).
11306 @code{Characters.Latin_1} are not available and
11307 concatenation is not implemented. Thus, escape characters in strings are
11308 not currently available.
11311 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11312 equality of representations. They will generally work correctly
11313 for strings and arrays whose elements have integer or enumeration types.
11314 They may not work correctly for arrays whose element
11315 types have user-defined equality, for arrays of real values
11316 (in particular, IEEE-conformant floating point, because of negative
11317 zeroes and NaNs), and for arrays whose elements contain unused bits with
11318 indeterminate values.
11321 The other component-by-component array operations (@code{and}, @code{or},
11322 @code{xor}, @code{not}, and relational tests other than equality)
11323 are not implemented.
11326 @cindex array aggregates (Ada)
11327 @cindex record aggregates (Ada)
11328 @cindex aggregates (Ada)
11329 There is limited support for array and record aggregates. They are
11330 permitted only on the right sides of assignments, as in these examples:
11333 set An_Array := (1, 2, 3, 4, 5, 6)
11334 set An_Array := (1, others => 0)
11335 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11336 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11337 set A_Record := (1, "Peter", True);
11338 set A_Record := (Name => "Peter", Id => 1, Alive => True)
11342 discriminant's value by assigning an aggregate has an
11343 undefined effect if that discriminant is used within the record.
11344 However, you can first modify discriminants by directly assigning to
11345 them (which normally would not be allowed in Ada), and then performing an
11346 aggregate assignment. For example, given a variable @code{A_Rec}
11347 declared to have a type such as:
11350 type Rec (Len : Small_Integer := 0) is record
11352 Vals : IntArray (1 .. Len);
11356 you can assign a value with a different size of @code{Vals} with two
11361 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11364 As this example also illustrates, @value{GDBN} is very loose about the usual
11365 rules concerning aggregates. You may leave out some of the
11366 components of an array or record aggregate (such as the @code{Len}
11367 component in the assignment to @code{A_Rec} above); they will retain their
11368 original values upon assignment. You may freely use dynamic values as
11369 indices in component associations. You may even use overlapping or
11370 redundant component associations, although which component values are
11371 assigned in such cases is not defined.
11374 Calls to dispatching subprograms are not implemented.
11377 The overloading algorithm is much more limited (i.e., less selective)
11378 than that of real Ada. It makes only limited use of the context in
11379 which a subexpression appears to resolve its meaning, and it is much
11380 looser in its rules for allowing type matches. As a result, some
11381 function calls will be ambiguous, and the user will be asked to choose
11382 the proper resolution.
11385 The @code{new} operator is not implemented.
11388 Entry calls are not implemented.
11391 Aside from printing, arithmetic operations on the native VAX floating-point
11392 formats are not supported.
11395 It is not possible to slice a packed array.
11398 The names @code{True} and @code{False}, when not part of a qualified name,
11399 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11401 Should your program
11402 redefine these names in a package or procedure (at best a dubious practice),
11403 you will have to use fully qualified names to access their new definitions.
11406 @node Additions to Ada
11407 @subsubsection Additions to Ada
11408 @cindex Ada, deviations from
11410 As it does for other languages, @value{GDBN} makes certain generic
11411 extensions to Ada (@pxref{Expressions}):
11415 If the expression @var{E} is a variable residing in memory (typically
11416 a local variable or array element) and @var{N} is a positive integer,
11417 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11418 @var{N}-1 adjacent variables following it in memory as an array. In
11419 Ada, this operator is generally not necessary, since its prime use is
11420 in displaying parts of an array, and slicing will usually do this in
11421 Ada. However, there are occasional uses when debugging programs in
11422 which certain debugging information has been optimized away.
11425 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11426 appears in function or file @var{B}.'' When @var{B} is a file name,
11427 you must typically surround it in single quotes.
11430 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11431 @var{type} that appears at address @var{addr}.''
11434 A name starting with @samp{$} is a convenience variable
11435 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11438 In addition, @value{GDBN} provides a few other shortcuts and outright
11439 additions specific to Ada:
11443 The assignment statement is allowed as an expression, returning
11444 its right-hand operand as its value. Thus, you may enter
11448 print A(tmp := y + 1)
11452 The semicolon is allowed as an ``operator,'' returning as its value
11453 the value of its right-hand operand.
11454 This allows, for example,
11455 complex conditional breaks:
11459 condition 1 (report(i); k += 1; A(k) > 100)
11463 Rather than use catenation and symbolic character names to introduce special
11464 characters into strings, one may instead use a special bracket notation,
11465 which is also used to print strings. A sequence of characters of the form
11466 @samp{["@var{XX}"]} within a string or character literal denotes the
11467 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11468 sequence of characters @samp{["""]} also denotes a single quotation mark
11469 in strings. For example,
11471 "One line.["0a"]Next line.["0a"]"
11474 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11478 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11479 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11487 When printing arrays, @value{GDBN} uses positional notation when the
11488 array has a lower bound of 1, and uses a modified named notation otherwise.
11489 For example, a one-dimensional array of three integers with a lower bound
11490 of 3 might print as
11497 That is, in contrast to valid Ada, only the first component has a @code{=>}
11501 You may abbreviate attributes in expressions with any unique,
11502 multi-character subsequence of
11503 their names (an exact match gets preference).
11504 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11505 in place of @t{a'length}.
11508 @cindex quoting Ada internal identifiers
11509 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11510 to lower case. The GNAT compiler uses upper-case characters for
11511 some of its internal identifiers, which are normally of no interest to users.
11512 For the rare occasions when you actually have to look at them,
11513 enclose them in angle brackets to avoid the lower-case mapping.
11516 @value{GDBP} print <JMPBUF_SAVE>[0]
11520 Printing an object of class-wide type or dereferencing an
11521 access-to-class-wide value will display all the components of the object's
11522 specific type (as indicated by its run-time tag). Likewise, component
11523 selection on such a value will operate on the specific type of the
11528 @node Stopping Before Main Program
11529 @subsubsection Stopping at the Very Beginning
11531 @cindex breakpointing Ada elaboration code
11532 It is sometimes necessary to debug the program during elaboration, and
11533 before reaching the main procedure.
11534 As defined in the Ada Reference
11535 Manual, the elaboration code is invoked from a procedure called
11536 @code{adainit}. To run your program up to the beginning of
11537 elaboration, simply use the following two commands:
11538 @code{tbreak adainit} and @code{run}.
11541 @subsubsection Extensions for Ada Tasks
11542 @cindex Ada, tasking
11544 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11545 @value{GDBN} provides the following task-related commands:
11550 This command shows a list of current Ada tasks, as in the following example:
11557 (@value{GDBP}) info tasks
11558 ID TID P-ID Pri State Name
11559 1 8088000 0 15 Child Activation Wait main_task
11560 2 80a4000 1 15 Accept Statement b
11561 3 809a800 1 15 Child Activation Wait a
11562 * 4 80ae800 3 15 Running c
11567 In this listing, the asterisk before the last task indicates it to be the
11568 task currently being inspected.
11572 Represents @value{GDBN}'s internal task number.
11578 The parent's task ID (@value{GDBN}'s internal task number).
11581 The base priority of the task.
11584 Current state of the task.
11588 The task has been created but has not been activated. It cannot be
11592 The task currently running.
11595 The task is not blocked for any reason known to Ada. (It may be waiting
11596 for a mutex, though.) It is conceptually "executing" in normal mode.
11599 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11600 that were waiting on terminate alternatives have been awakened and have
11601 terminated themselves.
11603 @item Child Activation Wait
11604 The task is waiting for created tasks to complete activation.
11606 @item Accept Statement
11607 The task is waiting on an accept or selective wait statement.
11609 @item Waiting on entry call
11610 The task is waiting on an entry call.
11612 @item Async Select Wait
11613 The task is waiting to start the abortable part of an asynchronous
11617 The task is waiting on a select statement with only a delay
11620 @item Child Termination Wait
11621 The task is sleeping having completed a master within itself, and is
11622 waiting for the tasks dependent on that master to become terminated or
11623 waiting on a terminate Phase.
11625 @item Wait Child in Term Alt
11626 The task is sleeping waiting for tasks on terminate alternatives to
11627 finish terminating.
11629 @item Accepting RV with @var{taskno}
11630 The task is accepting a rendez-vous with the task @var{taskno}.
11634 Name of the task in the program.
11638 @kindex info task @var{taskno}
11639 @item info task @var{taskno}
11640 This command shows detailled informations on the specified task, as in
11641 the following example:
11646 (@value{GDBP}) info tasks
11647 ID TID P-ID Pri State Name
11648 1 8077880 0 15 Child Activation Wait main_task
11649 * 2 807c468 1 15 Running task_1
11650 (@value{GDBP}) info task 2
11651 Ada Task: 0x807c468
11654 Parent: 1 (main_task)
11660 @kindex task@r{ (Ada)}
11661 @cindex current Ada task ID
11662 This command prints the ID of the current task.
11668 (@value{GDBP}) info tasks
11669 ID TID P-ID Pri State Name
11670 1 8077870 0 15 Child Activation Wait main_task
11671 * 2 807c458 1 15 Running t
11672 (@value{GDBP}) task
11673 [Current task is 2]
11676 @item task @var{taskno}
11677 @cindex Ada task switching
11678 This command is like the @code{thread @var{threadno}}
11679 command (@pxref{Threads}). It switches the context of debugging
11680 from the current task to the given task.
11686 (@value{GDBP}) info tasks
11687 ID TID P-ID Pri State Name
11688 1 8077870 0 15 Child Activation Wait main_task
11689 * 2 807c458 1 15 Running t
11690 (@value{GDBP}) task 1
11691 [Switching to task 1]
11692 #0 0x8067726 in pthread_cond_wait ()
11694 #0 0x8067726 in pthread_cond_wait ()
11695 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11696 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11697 #3 0x806153e in system.tasking.stages.activate_tasks ()
11698 #4 0x804aacc in un () at un.adb:5
11703 @node Ada Tasks and Core Files
11704 @subsubsection Tasking Support when Debugging Core Files
11705 @cindex Ada tasking and core file debugging
11707 When inspecting a core file, as opposed to debugging a live program,
11708 tasking support may be limited or even unavailable, depending on
11709 the platform being used.
11710 For instance, on x86-linux, the list of tasks is available, but task
11711 switching is not supported. On Tru64, however, task switching will work
11714 On certain platforms, including Tru64, the debugger needs to perform some
11715 memory writes in order to provide Ada tasking support. When inspecting
11716 a core file, this means that the core file must be opened with read-write
11717 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11718 Under these circumstances, you should make a backup copy of the core
11719 file before inspecting it with @value{GDBN}.
11722 @subsubsection Known Peculiarities of Ada Mode
11723 @cindex Ada, problems
11725 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11726 we know of several problems with and limitations of Ada mode in
11728 some of which will be fixed with planned future releases of the debugger
11729 and the GNU Ada compiler.
11733 Currently, the debugger
11734 has insufficient information to determine whether certain pointers represent
11735 pointers to objects or the objects themselves.
11736 Thus, the user may have to tack an extra @code{.all} after an expression
11737 to get it printed properly.
11740 Static constants that the compiler chooses not to materialize as objects in
11741 storage are invisible to the debugger.
11744 Named parameter associations in function argument lists are ignored (the
11745 argument lists are treated as positional).
11748 Many useful library packages are currently invisible to the debugger.
11751 Fixed-point arithmetic, conversions, input, and output is carried out using
11752 floating-point arithmetic, and may give results that only approximate those on
11756 The type of the @t{'Address} attribute may not be @code{System.Address}.
11759 The GNAT compiler never generates the prefix @code{Standard} for any of
11760 the standard symbols defined by the Ada language. @value{GDBN} knows about
11761 this: it will strip the prefix from names when you use it, and will never
11762 look for a name you have so qualified among local symbols, nor match against
11763 symbols in other packages or subprograms. If you have
11764 defined entities anywhere in your program other than parameters and
11765 local variables whose simple names match names in @code{Standard},
11766 GNAT's lack of qualification here can cause confusion. When this happens,
11767 you can usually resolve the confusion
11768 by qualifying the problematic names with package
11769 @code{Standard} explicitly.
11772 @node Unsupported Languages
11773 @section Unsupported Languages
11775 @cindex unsupported languages
11776 @cindex minimal language
11777 In addition to the other fully-supported programming languages,
11778 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11779 It does not represent a real programming language, but provides a set
11780 of capabilities close to what the C or assembly languages provide.
11781 This should allow most simple operations to be performed while debugging
11782 an application that uses a language currently not supported by @value{GDBN}.
11784 If the language is set to @code{auto}, @value{GDBN} will automatically
11785 select this language if the current frame corresponds to an unsupported
11789 @chapter Examining the Symbol Table
11791 The commands described in this chapter allow you to inquire about the
11792 symbols (names of variables, functions and types) defined in your
11793 program. This information is inherent in the text of your program and
11794 does not change as your program executes. @value{GDBN} finds it in your
11795 program's symbol table, in the file indicated when you started @value{GDBN}
11796 (@pxref{File Options, ,Choosing Files}), or by one of the
11797 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11799 @cindex symbol names
11800 @cindex names of symbols
11801 @cindex quoting names
11802 Occasionally, you may need to refer to symbols that contain unusual
11803 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11804 most frequent case is in referring to static variables in other
11805 source files (@pxref{Variables,,Program Variables}). File names
11806 are recorded in object files as debugging symbols, but @value{GDBN} would
11807 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11808 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11809 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11816 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11819 @cindex case-insensitive symbol names
11820 @cindex case sensitivity in symbol names
11821 @kindex set case-sensitive
11822 @item set case-sensitive on
11823 @itemx set case-sensitive off
11824 @itemx set case-sensitive auto
11825 Normally, when @value{GDBN} looks up symbols, it matches their names
11826 with case sensitivity determined by the current source language.
11827 Occasionally, you may wish to control that. The command @code{set
11828 case-sensitive} lets you do that by specifying @code{on} for
11829 case-sensitive matches or @code{off} for case-insensitive ones. If
11830 you specify @code{auto}, case sensitivity is reset to the default
11831 suitable for the source language. The default is case-sensitive
11832 matches for all languages except for Fortran, for which the default is
11833 case-insensitive matches.
11835 @kindex show case-sensitive
11836 @item show case-sensitive
11837 This command shows the current setting of case sensitivity for symbols
11840 @kindex info address
11841 @cindex address of a symbol
11842 @item info address @var{symbol}
11843 Describe where the data for @var{symbol} is stored. For a register
11844 variable, this says which register it is kept in. For a non-register
11845 local variable, this prints the stack-frame offset at which the variable
11848 Note the contrast with @samp{print &@var{symbol}}, which does not work
11849 at all for a register variable, and for a stack local variable prints
11850 the exact address of the current instantiation of the variable.
11852 @kindex info symbol
11853 @cindex symbol from address
11854 @cindex closest symbol and offset for an address
11855 @item info symbol @var{addr}
11856 Print the name of a symbol which is stored at the address @var{addr}.
11857 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11858 nearest symbol and an offset from it:
11861 (@value{GDBP}) info symbol 0x54320
11862 _initialize_vx + 396 in section .text
11866 This is the opposite of the @code{info address} command. You can use
11867 it to find out the name of a variable or a function given its address.
11870 @item whatis [@var{arg}]
11871 Print the data type of @var{arg}, which can be either an expression or
11872 a data type. With no argument, print the data type of @code{$}, the
11873 last value in the value history. If @var{arg} is an expression, it is
11874 not actually evaluated, and any side-effecting operations (such as
11875 assignments or function calls) inside it do not take place. If
11876 @var{arg} is a type name, it may be the name of a type or typedef, or
11877 for C code it may have the form @samp{class @var{class-name}},
11878 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11879 @samp{enum @var{enum-tag}}.
11880 @xref{Expressions, ,Expressions}.
11883 @item ptype [@var{arg}]
11884 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11885 detailed description of the type, instead of just the name of the type.
11886 @xref{Expressions, ,Expressions}.
11888 For example, for this variable declaration:
11891 struct complex @{double real; double imag;@} v;
11895 the two commands give this output:
11899 (@value{GDBP}) whatis v
11900 type = struct complex
11901 (@value{GDBP}) ptype v
11902 type = struct complex @{
11910 As with @code{whatis}, using @code{ptype} without an argument refers to
11911 the type of @code{$}, the last value in the value history.
11913 @cindex incomplete type
11914 Sometimes, programs use opaque data types or incomplete specifications
11915 of complex data structure. If the debug information included in the
11916 program does not allow @value{GDBN} to display a full declaration of
11917 the data type, it will say @samp{<incomplete type>}. For example,
11918 given these declarations:
11922 struct foo *fooptr;
11926 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11929 (@value{GDBP}) ptype foo
11930 $1 = <incomplete type>
11934 ``Incomplete type'' is C terminology for data types that are not
11935 completely specified.
11938 @item info types @var{regexp}
11940 Print a brief description of all types whose names match the regular
11941 expression @var{regexp} (or all types in your program, if you supply
11942 no argument). Each complete typename is matched as though it were a
11943 complete line; thus, @samp{i type value} gives information on all
11944 types in your program whose names include the string @code{value}, but
11945 @samp{i type ^value$} gives information only on types whose complete
11946 name is @code{value}.
11948 This command differs from @code{ptype} in two ways: first, like
11949 @code{whatis}, it does not print a detailed description; second, it
11950 lists all source files where a type is defined.
11953 @cindex local variables
11954 @item info scope @var{location}
11955 List all the variables local to a particular scope. This command
11956 accepts a @var{location} argument---a function name, a source line, or
11957 an address preceded by a @samp{*}, and prints all the variables local
11958 to the scope defined by that location. (@xref{Specify Location}, for
11959 details about supported forms of @var{location}.) For example:
11962 (@value{GDBP}) @b{info scope command_line_handler}
11963 Scope for command_line_handler:
11964 Symbol rl is an argument at stack/frame offset 8, length 4.
11965 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11966 Symbol linelength is in static storage at address 0x150a1c, length 4.
11967 Symbol p is a local variable in register $esi, length 4.
11968 Symbol p1 is a local variable in register $ebx, length 4.
11969 Symbol nline is a local variable in register $edx, length 4.
11970 Symbol repeat is a local variable at frame offset -8, length 4.
11974 This command is especially useful for determining what data to collect
11975 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11978 @kindex info source
11980 Show information about the current source file---that is, the source file for
11981 the function containing the current point of execution:
11984 the name of the source file, and the directory containing it,
11986 the directory it was compiled in,
11988 its length, in lines,
11990 which programming language it is written in,
11992 whether the executable includes debugging information for that file, and
11993 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11995 whether the debugging information includes information about
11996 preprocessor macros.
12000 @kindex info sources
12002 Print the names of all source files in your program for which there is
12003 debugging information, organized into two lists: files whose symbols
12004 have already been read, and files whose symbols will be read when needed.
12006 @kindex info functions
12007 @item info functions
12008 Print the names and data types of all defined functions.
12010 @item info functions @var{regexp}
12011 Print the names and data types of all defined functions
12012 whose names contain a match for regular expression @var{regexp}.
12013 Thus, @samp{info fun step} finds all functions whose names
12014 include @code{step}; @samp{info fun ^step} finds those whose names
12015 start with @code{step}. If a function name contains characters
12016 that conflict with the regular expression language (e.g.@:
12017 @samp{operator*()}), they may be quoted with a backslash.
12019 @kindex info variables
12020 @item info variables
12021 Print the names and data types of all variables that are declared
12022 outside of functions (i.e.@: excluding local variables).
12024 @item info variables @var{regexp}
12025 Print the names and data types of all variables (except for local
12026 variables) whose names contain a match for regular expression
12029 @kindex info classes
12030 @cindex Objective-C, classes and selectors
12032 @itemx info classes @var{regexp}
12033 Display all Objective-C classes in your program, or
12034 (with the @var{regexp} argument) all those matching a particular regular
12037 @kindex info selectors
12038 @item info selectors
12039 @itemx info selectors @var{regexp}
12040 Display all Objective-C selectors in your program, or
12041 (with the @var{regexp} argument) all those matching a particular regular
12045 This was never implemented.
12046 @kindex info methods
12048 @itemx info methods @var{regexp}
12049 The @code{info methods} command permits the user to examine all defined
12050 methods within C@t{++} program, or (with the @var{regexp} argument) a
12051 specific set of methods found in the various C@t{++} classes. Many
12052 C@t{++} classes provide a large number of methods. Thus, the output
12053 from the @code{ptype} command can be overwhelming and hard to use. The
12054 @code{info-methods} command filters the methods, printing only those
12055 which match the regular-expression @var{regexp}.
12058 @cindex reloading symbols
12059 Some systems allow individual object files that make up your program to
12060 be replaced without stopping and restarting your program. For example,
12061 in VxWorks you can simply recompile a defective object file and keep on
12062 running. If you are running on one of these systems, you can allow
12063 @value{GDBN} to reload the symbols for automatically relinked modules:
12066 @kindex set symbol-reloading
12067 @item set symbol-reloading on
12068 Replace symbol definitions for the corresponding source file when an
12069 object file with a particular name is seen again.
12071 @item set symbol-reloading off
12072 Do not replace symbol definitions when encountering object files of the
12073 same name more than once. This is the default state; if you are not
12074 running on a system that permits automatic relinking of modules, you
12075 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12076 may discard symbols when linking large programs, that may contain
12077 several modules (from different directories or libraries) with the same
12080 @kindex show symbol-reloading
12081 @item show symbol-reloading
12082 Show the current @code{on} or @code{off} setting.
12085 @cindex opaque data types
12086 @kindex set opaque-type-resolution
12087 @item set opaque-type-resolution on
12088 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12089 declared as a pointer to a @code{struct}, @code{class}, or
12090 @code{union}---for example, @code{struct MyType *}---that is used in one
12091 source file although the full declaration of @code{struct MyType} is in
12092 another source file. The default is on.
12094 A change in the setting of this subcommand will not take effect until
12095 the next time symbols for a file are loaded.
12097 @item set opaque-type-resolution off
12098 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12099 is printed as follows:
12101 @{<no data fields>@}
12104 @kindex show opaque-type-resolution
12105 @item show opaque-type-resolution
12106 Show whether opaque types are resolved or not.
12108 @kindex set print symbol-loading
12109 @cindex print messages when symbols are loaded
12110 @item set print symbol-loading
12111 @itemx set print symbol-loading on
12112 @itemx set print symbol-loading off
12113 The @code{set print symbol-loading} command allows you to enable or
12114 disable printing of messages when @value{GDBN} loads symbols.
12115 By default, these messages will be printed, and normally this is what
12116 you want. Disabling these messages is useful when debugging applications
12117 with lots of shared libraries where the quantity of output can be more
12118 annoying than useful.
12120 @kindex show print symbol-loading
12121 @item show print symbol-loading
12122 Show whether messages will be printed when @value{GDBN} loads symbols.
12124 @kindex maint print symbols
12125 @cindex symbol dump
12126 @kindex maint print psymbols
12127 @cindex partial symbol dump
12128 @item maint print symbols @var{filename}
12129 @itemx maint print psymbols @var{filename}
12130 @itemx maint print msymbols @var{filename}
12131 Write a dump of debugging symbol data into the file @var{filename}.
12132 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12133 symbols with debugging data are included. If you use @samp{maint print
12134 symbols}, @value{GDBN} includes all the symbols for which it has already
12135 collected full details: that is, @var{filename} reflects symbols for
12136 only those files whose symbols @value{GDBN} has read. You can use the
12137 command @code{info sources} to find out which files these are. If you
12138 use @samp{maint print psymbols} instead, the dump shows information about
12139 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12140 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12141 @samp{maint print msymbols} dumps just the minimal symbol information
12142 required for each object file from which @value{GDBN} has read some symbols.
12143 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12144 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12146 @kindex maint info symtabs
12147 @kindex maint info psymtabs
12148 @cindex listing @value{GDBN}'s internal symbol tables
12149 @cindex symbol tables, listing @value{GDBN}'s internal
12150 @cindex full symbol tables, listing @value{GDBN}'s internal
12151 @cindex partial symbol tables, listing @value{GDBN}'s internal
12152 @item maint info symtabs @r{[} @var{regexp} @r{]}
12153 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12155 List the @code{struct symtab} or @code{struct partial_symtab}
12156 structures whose names match @var{regexp}. If @var{regexp} is not
12157 given, list them all. The output includes expressions which you can
12158 copy into a @value{GDBN} debugging this one to examine a particular
12159 structure in more detail. For example:
12162 (@value{GDBP}) maint info psymtabs dwarf2read
12163 @{ objfile /home/gnu/build/gdb/gdb
12164 ((struct objfile *) 0x82e69d0)
12165 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12166 ((struct partial_symtab *) 0x8474b10)
12169 text addresses 0x814d3c8 -- 0x8158074
12170 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12171 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12172 dependencies (none)
12175 (@value{GDBP}) maint info symtabs
12179 We see that there is one partial symbol table whose filename contains
12180 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12181 and we see that @value{GDBN} has not read in any symtabs yet at all.
12182 If we set a breakpoint on a function, that will cause @value{GDBN} to
12183 read the symtab for the compilation unit containing that function:
12186 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12187 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12189 (@value{GDBP}) maint info symtabs
12190 @{ objfile /home/gnu/build/gdb/gdb
12191 ((struct objfile *) 0x82e69d0)
12192 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12193 ((struct symtab *) 0x86c1f38)
12196 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12197 linetable ((struct linetable *) 0x8370fa0)
12198 debugformat DWARF 2
12207 @chapter Altering Execution
12209 Once you think you have found an error in your program, you might want to
12210 find out for certain whether correcting the apparent error would lead to
12211 correct results in the rest of the run. You can find the answer by
12212 experiment, using the @value{GDBN} features for altering execution of the
12215 For example, you can store new values into variables or memory
12216 locations, give your program a signal, restart it at a different
12217 address, or even return prematurely from a function.
12220 * Assignment:: Assignment to variables
12221 * Jumping:: Continuing at a different address
12222 * Signaling:: Giving your program a signal
12223 * Returning:: Returning from a function
12224 * Calling:: Calling your program's functions
12225 * Patching:: Patching your program
12229 @section Assignment to Variables
12232 @cindex setting variables
12233 To alter the value of a variable, evaluate an assignment expression.
12234 @xref{Expressions, ,Expressions}. For example,
12241 stores the value 4 into the variable @code{x}, and then prints the
12242 value of the assignment expression (which is 4).
12243 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12244 information on operators in supported languages.
12246 @kindex set variable
12247 @cindex variables, setting
12248 If you are not interested in seeing the value of the assignment, use the
12249 @code{set} command instead of the @code{print} command. @code{set} is
12250 really the same as @code{print} except that the expression's value is
12251 not printed and is not put in the value history (@pxref{Value History,
12252 ,Value History}). The expression is evaluated only for its effects.
12254 If the beginning of the argument string of the @code{set} command
12255 appears identical to a @code{set} subcommand, use the @code{set
12256 variable} command instead of just @code{set}. This command is identical
12257 to @code{set} except for its lack of subcommands. For example, if your
12258 program has a variable @code{width}, you get an error if you try to set
12259 a new value with just @samp{set width=13}, because @value{GDBN} has the
12260 command @code{set width}:
12263 (@value{GDBP}) whatis width
12265 (@value{GDBP}) p width
12267 (@value{GDBP}) set width=47
12268 Invalid syntax in expression.
12272 The invalid expression, of course, is @samp{=47}. In
12273 order to actually set the program's variable @code{width}, use
12276 (@value{GDBP}) set var width=47
12279 Because the @code{set} command has many subcommands that can conflict
12280 with the names of program variables, it is a good idea to use the
12281 @code{set variable} command instead of just @code{set}. For example, if
12282 your program has a variable @code{g}, you run into problems if you try
12283 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12284 the command @code{set gnutarget}, abbreviated @code{set g}:
12288 (@value{GDBP}) whatis g
12292 (@value{GDBP}) set g=4
12296 The program being debugged has been started already.
12297 Start it from the beginning? (y or n) y
12298 Starting program: /home/smith/cc_progs/a.out
12299 "/home/smith/cc_progs/a.out": can't open to read symbols:
12300 Invalid bfd target.
12301 (@value{GDBP}) show g
12302 The current BFD target is "=4".
12307 The program variable @code{g} did not change, and you silently set the
12308 @code{gnutarget} to an invalid value. In order to set the variable
12312 (@value{GDBP}) set var g=4
12315 @value{GDBN} allows more implicit conversions in assignments than C; you can
12316 freely store an integer value into a pointer variable or vice versa,
12317 and you can convert any structure to any other structure that is the
12318 same length or shorter.
12319 @comment FIXME: how do structs align/pad in these conversions?
12320 @comment /doc@cygnus.com 18dec1990
12322 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12323 construct to generate a value of specified type at a specified address
12324 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12325 to memory location @code{0x83040} as an integer (which implies a certain size
12326 and representation in memory), and
12329 set @{int@}0x83040 = 4
12333 stores the value 4 into that memory location.
12336 @section Continuing at a Different Address
12338 Ordinarily, when you continue your program, you do so at the place where
12339 it stopped, with the @code{continue} command. You can instead continue at
12340 an address of your own choosing, with the following commands:
12344 @item jump @var{linespec}
12345 @itemx jump @var{location}
12346 Resume execution at line @var{linespec} or at address given by
12347 @var{location}. Execution stops again immediately if there is a
12348 breakpoint there. @xref{Specify Location}, for a description of the
12349 different forms of @var{linespec} and @var{location}. It is common
12350 practice to use the @code{tbreak} command in conjunction with
12351 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12353 The @code{jump} command does not change the current stack frame, or
12354 the stack pointer, or the contents of any memory location or any
12355 register other than the program counter. If line @var{linespec} is in
12356 a different function from the one currently executing, the results may
12357 be bizarre if the two functions expect different patterns of arguments or
12358 of local variables. For this reason, the @code{jump} command requests
12359 confirmation if the specified line is not in the function currently
12360 executing. However, even bizarre results are predictable if you are
12361 well acquainted with the machine-language code of your program.
12364 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12365 On many systems, you can get much the same effect as the @code{jump}
12366 command by storing a new value into the register @code{$pc}. The
12367 difference is that this does not start your program running; it only
12368 changes the address of where it @emph{will} run when you continue. For
12376 makes the next @code{continue} command or stepping command execute at
12377 address @code{0x485}, rather than at the address where your program stopped.
12378 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12380 The most common occasion to use the @code{jump} command is to back
12381 up---perhaps with more breakpoints set---over a portion of a program
12382 that has already executed, in order to examine its execution in more
12387 @section Giving your Program a Signal
12388 @cindex deliver a signal to a program
12392 @item signal @var{signal}
12393 Resume execution where your program stopped, but immediately give it the
12394 signal @var{signal}. @var{signal} can be the name or the number of a
12395 signal. For example, on many systems @code{signal 2} and @code{signal
12396 SIGINT} are both ways of sending an interrupt signal.
12398 Alternatively, if @var{signal} is zero, continue execution without
12399 giving a signal. This is useful when your program stopped on account of
12400 a signal and would ordinary see the signal when resumed with the
12401 @code{continue} command; @samp{signal 0} causes it to resume without a
12404 @code{signal} does not repeat when you press @key{RET} a second time
12405 after executing the command.
12409 Invoking the @code{signal} command is not the same as invoking the
12410 @code{kill} utility from the shell. Sending a signal with @code{kill}
12411 causes @value{GDBN} to decide what to do with the signal depending on
12412 the signal handling tables (@pxref{Signals}). The @code{signal} command
12413 passes the signal directly to your program.
12417 @section Returning from a Function
12420 @cindex returning from a function
12423 @itemx return @var{expression}
12424 You can cancel execution of a function call with the @code{return}
12425 command. If you give an
12426 @var{expression} argument, its value is used as the function's return
12430 When you use @code{return}, @value{GDBN} discards the selected stack frame
12431 (and all frames within it). You can think of this as making the
12432 discarded frame return prematurely. If you wish to specify a value to
12433 be returned, give that value as the argument to @code{return}.
12435 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12436 Frame}), and any other frames inside of it, leaving its caller as the
12437 innermost remaining frame. That frame becomes selected. The
12438 specified value is stored in the registers used for returning values
12441 The @code{return} command does not resume execution; it leaves the
12442 program stopped in the state that would exist if the function had just
12443 returned. In contrast, the @code{finish} command (@pxref{Continuing
12444 and Stepping, ,Continuing and Stepping}) resumes execution until the
12445 selected stack frame returns naturally.
12448 @section Calling Program Functions
12451 @cindex calling functions
12452 @cindex inferior functions, calling
12453 @item print @var{expr}
12454 Evaluate the expression @var{expr} and display the resulting value.
12455 @var{expr} may include calls to functions in the program being
12459 @item call @var{expr}
12460 Evaluate the expression @var{expr} without displaying @code{void}
12463 You can use this variant of the @code{print} command if you want to
12464 execute a function from your program that does not return anything
12465 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12466 with @code{void} returned values that @value{GDBN} will otherwise
12467 print. If the result is not void, it is printed and saved in the
12471 It is possible for the function you call via the @code{print} or
12472 @code{call} command to generate a signal (e.g., if there's a bug in
12473 the function, or if you passed it incorrect arguments). What happens
12474 in that case is controlled by the @code{set unwindonsignal} command.
12477 @item set unwindonsignal
12478 @kindex set unwindonsignal
12479 @cindex unwind stack in called functions
12480 @cindex call dummy stack unwinding
12481 Set unwinding of the stack if a signal is received while in a function
12482 that @value{GDBN} called in the program being debugged. If set to on,
12483 @value{GDBN} unwinds the stack it created for the call and restores
12484 the context to what it was before the call. If set to off (the
12485 default), @value{GDBN} stops in the frame where the signal was
12488 @item show unwindonsignal
12489 @kindex show unwindonsignal
12490 Show the current setting of stack unwinding in the functions called by
12494 @cindex weak alias functions
12495 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12496 for another function. In such case, @value{GDBN} might not pick up
12497 the type information, including the types of the function arguments,
12498 which causes @value{GDBN} to call the inferior function incorrectly.
12499 As a result, the called function will function erroneously and may
12500 even crash. A solution to that is to use the name of the aliased
12504 @section Patching Programs
12506 @cindex patching binaries
12507 @cindex writing into executables
12508 @cindex writing into corefiles
12510 By default, @value{GDBN} opens the file containing your program's
12511 executable code (or the corefile) read-only. This prevents accidental
12512 alterations to machine code; but it also prevents you from intentionally
12513 patching your program's binary.
12515 If you'd like to be able to patch the binary, you can specify that
12516 explicitly with the @code{set write} command. For example, you might
12517 want to turn on internal debugging flags, or even to make emergency
12523 @itemx set write off
12524 If you specify @samp{set write on}, @value{GDBN} opens executable and
12525 core files for both reading and writing; if you specify @kbd{set write
12526 off} (the default), @value{GDBN} opens them read-only.
12528 If you have already loaded a file, you must load it again (using the
12529 @code{exec-file} or @code{core-file} command) after changing @code{set
12530 write}, for your new setting to take effect.
12534 Display whether executable files and core files are opened for writing
12535 as well as reading.
12539 @chapter @value{GDBN} Files
12541 @value{GDBN} needs to know the file name of the program to be debugged,
12542 both in order to read its symbol table and in order to start your
12543 program. To debug a core dump of a previous run, you must also tell
12544 @value{GDBN} the name of the core dump file.
12547 * Files:: Commands to specify files
12548 * Separate Debug Files:: Debugging information in separate files
12549 * Symbol Errors:: Errors reading symbol files
12553 @section Commands to Specify Files
12555 @cindex symbol table
12556 @cindex core dump file
12558 You may want to specify executable and core dump file names. The usual
12559 way to do this is at start-up time, using the arguments to
12560 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12561 Out of @value{GDBN}}).
12563 Occasionally it is necessary to change to a different file during a
12564 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12565 specify a file you want to use. Or you are debugging a remote target
12566 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12567 Program}). In these situations the @value{GDBN} commands to specify
12568 new files are useful.
12571 @cindex executable file
12573 @item file @var{filename}
12574 Use @var{filename} as the program to be debugged. It is read for its
12575 symbols and for the contents of pure memory. It is also the program
12576 executed when you use the @code{run} command. If you do not specify a
12577 directory and the file is not found in the @value{GDBN} working directory,
12578 @value{GDBN} uses the environment variable @code{PATH} as a list of
12579 directories to search, just as the shell does when looking for a program
12580 to run. You can change the value of this variable, for both @value{GDBN}
12581 and your program, using the @code{path} command.
12583 @cindex unlinked object files
12584 @cindex patching object files
12585 You can load unlinked object @file{.o} files into @value{GDBN} using
12586 the @code{file} command. You will not be able to ``run'' an object
12587 file, but you can disassemble functions and inspect variables. Also,
12588 if the underlying BFD functionality supports it, you could use
12589 @kbd{gdb -write} to patch object files using this technique. Note
12590 that @value{GDBN} can neither interpret nor modify relocations in this
12591 case, so branches and some initialized variables will appear to go to
12592 the wrong place. But this feature is still handy from time to time.
12595 @code{file} with no argument makes @value{GDBN} discard any information it
12596 has on both executable file and the symbol table.
12599 @item exec-file @r{[} @var{filename} @r{]}
12600 Specify that the program to be run (but not the symbol table) is found
12601 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12602 if necessary to locate your program. Omitting @var{filename} means to
12603 discard information on the executable file.
12605 @kindex symbol-file
12606 @item symbol-file @r{[} @var{filename} @r{]}
12607 Read symbol table information from file @var{filename}. @code{PATH} is
12608 searched when necessary. Use the @code{file} command to get both symbol
12609 table and program to run from the same file.
12611 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12612 program's symbol table.
12614 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12615 some breakpoints and auto-display expressions. This is because they may
12616 contain pointers to the internal data recording symbols and data types,
12617 which are part of the old symbol table data being discarded inside
12620 @code{symbol-file} does not repeat if you press @key{RET} again after
12623 When @value{GDBN} is configured for a particular environment, it
12624 understands debugging information in whatever format is the standard
12625 generated for that environment; you may use either a @sc{gnu} compiler, or
12626 other compilers that adhere to the local conventions.
12627 Best results are usually obtained from @sc{gnu} compilers; for example,
12628 using @code{@value{NGCC}} you can generate debugging information for
12631 For most kinds of object files, with the exception of old SVR3 systems
12632 using COFF, the @code{symbol-file} command does not normally read the
12633 symbol table in full right away. Instead, it scans the symbol table
12634 quickly to find which source files and which symbols are present. The
12635 details are read later, one source file at a time, as they are needed.
12637 The purpose of this two-stage reading strategy is to make @value{GDBN}
12638 start up faster. For the most part, it is invisible except for
12639 occasional pauses while the symbol table details for a particular source
12640 file are being read. (The @code{set verbose} command can turn these
12641 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12642 Warnings and Messages}.)
12644 We have not implemented the two-stage strategy for COFF yet. When the
12645 symbol table is stored in COFF format, @code{symbol-file} reads the
12646 symbol table data in full right away. Note that ``stabs-in-COFF''
12647 still does the two-stage strategy, since the debug info is actually
12651 @cindex reading symbols immediately
12652 @cindex symbols, reading immediately
12653 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12654 @itemx file @var{filename} @r{[} -readnow @r{]}
12655 You can override the @value{GDBN} two-stage strategy for reading symbol
12656 tables by using the @samp{-readnow} option with any of the commands that
12657 load symbol table information, if you want to be sure @value{GDBN} has the
12658 entire symbol table available.
12660 @c FIXME: for now no mention of directories, since this seems to be in
12661 @c flux. 13mar1992 status is that in theory GDB would look either in
12662 @c current dir or in same dir as myprog; but issues like competing
12663 @c GDB's, or clutter in system dirs, mean that in practice right now
12664 @c only current dir is used. FFish says maybe a special GDB hierarchy
12665 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12669 @item core-file @r{[}@var{filename}@r{]}
12671 Specify the whereabouts of a core dump file to be used as the ``contents
12672 of memory''. Traditionally, core files contain only some parts of the
12673 address space of the process that generated them; @value{GDBN} can access the
12674 executable file itself for other parts.
12676 @code{core-file} with no argument specifies that no core file is
12679 Note that the core file is ignored when your program is actually running
12680 under @value{GDBN}. So, if you have been running your program and you
12681 wish to debug a core file instead, you must kill the subprocess in which
12682 the program is running. To do this, use the @code{kill} command
12683 (@pxref{Kill Process, ,Killing the Child Process}).
12685 @kindex add-symbol-file
12686 @cindex dynamic linking
12687 @item add-symbol-file @var{filename} @var{address}
12688 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12689 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12690 The @code{add-symbol-file} command reads additional symbol table
12691 information from the file @var{filename}. You would use this command
12692 when @var{filename} has been dynamically loaded (by some other means)
12693 into the program that is running. @var{address} should be the memory
12694 address at which the file has been loaded; @value{GDBN} cannot figure
12695 this out for itself. You can additionally specify an arbitrary number
12696 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12697 section name and base address for that section. You can specify any
12698 @var{address} as an expression.
12700 The symbol table of the file @var{filename} is added to the symbol table
12701 originally read with the @code{symbol-file} command. You can use the
12702 @code{add-symbol-file} command any number of times; the new symbol data
12703 thus read keeps adding to the old. To discard all old symbol data
12704 instead, use the @code{symbol-file} command without any arguments.
12706 @cindex relocatable object files, reading symbols from
12707 @cindex object files, relocatable, reading symbols from
12708 @cindex reading symbols from relocatable object files
12709 @cindex symbols, reading from relocatable object files
12710 @cindex @file{.o} files, reading symbols from
12711 Although @var{filename} is typically a shared library file, an
12712 executable file, or some other object file which has been fully
12713 relocated for loading into a process, you can also load symbolic
12714 information from relocatable @file{.o} files, as long as:
12718 the file's symbolic information refers only to linker symbols defined in
12719 that file, not to symbols defined by other object files,
12721 every section the file's symbolic information refers to has actually
12722 been loaded into the inferior, as it appears in the file, and
12724 you can determine the address at which every section was loaded, and
12725 provide these to the @code{add-symbol-file} command.
12729 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12730 relocatable files into an already running program; such systems
12731 typically make the requirements above easy to meet. However, it's
12732 important to recognize that many native systems use complex link
12733 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12734 assembly, for example) that make the requirements difficult to meet. In
12735 general, one cannot assume that using @code{add-symbol-file} to read a
12736 relocatable object file's symbolic information will have the same effect
12737 as linking the relocatable object file into the program in the normal
12740 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12742 @kindex add-symbol-file-from-memory
12743 @cindex @code{syscall DSO}
12744 @cindex load symbols from memory
12745 @item add-symbol-file-from-memory @var{address}
12746 Load symbols from the given @var{address} in a dynamically loaded
12747 object file whose image is mapped directly into the inferior's memory.
12748 For example, the Linux kernel maps a @code{syscall DSO} into each
12749 process's address space; this DSO provides kernel-specific code for
12750 some system calls. The argument can be any expression whose
12751 evaluation yields the address of the file's shared object file header.
12752 For this command to work, you must have used @code{symbol-file} or
12753 @code{exec-file} commands in advance.
12755 @kindex add-shared-symbol-files
12757 @item add-shared-symbol-files @var{library-file}
12758 @itemx assf @var{library-file}
12759 The @code{add-shared-symbol-files} command can currently be used only
12760 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12761 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12762 @value{GDBN} automatically looks for shared libraries, however if
12763 @value{GDBN} does not find yours, you can invoke
12764 @code{add-shared-symbol-files}. It takes one argument: the shared
12765 library's file name. @code{assf} is a shorthand alias for
12766 @code{add-shared-symbol-files}.
12769 @item section @var{section} @var{addr}
12770 The @code{section} command changes the base address of the named
12771 @var{section} of the exec file to @var{addr}. This can be used if the
12772 exec file does not contain section addresses, (such as in the
12773 @code{a.out} format), or when the addresses specified in the file
12774 itself are wrong. Each section must be changed separately. The
12775 @code{info files} command, described below, lists all the sections and
12779 @kindex info target
12782 @code{info files} and @code{info target} are synonymous; both print the
12783 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12784 including the names of the executable and core dump files currently in
12785 use by @value{GDBN}, and the files from which symbols were loaded. The
12786 command @code{help target} lists all possible targets rather than
12789 @kindex maint info sections
12790 @item maint info sections
12791 Another command that can give you extra information about program sections
12792 is @code{maint info sections}. In addition to the section information
12793 displayed by @code{info files}, this command displays the flags and file
12794 offset of each section in the executable and core dump files. In addition,
12795 @code{maint info sections} provides the following command options (which
12796 may be arbitrarily combined):
12800 Display sections for all loaded object files, including shared libraries.
12801 @item @var{sections}
12802 Display info only for named @var{sections}.
12803 @item @var{section-flags}
12804 Display info only for sections for which @var{section-flags} are true.
12805 The section flags that @value{GDBN} currently knows about are:
12808 Section will have space allocated in the process when loaded.
12809 Set for all sections except those containing debug information.
12811 Section will be loaded from the file into the child process memory.
12812 Set for pre-initialized code and data, clear for @code{.bss} sections.
12814 Section needs to be relocated before loading.
12816 Section cannot be modified by the child process.
12818 Section contains executable code only.
12820 Section contains data only (no executable code).
12822 Section will reside in ROM.
12824 Section contains data for constructor/destructor lists.
12826 Section is not empty.
12828 An instruction to the linker to not output the section.
12829 @item COFF_SHARED_LIBRARY
12830 A notification to the linker that the section contains
12831 COFF shared library information.
12833 Section contains common symbols.
12836 @kindex set trust-readonly-sections
12837 @cindex read-only sections
12838 @item set trust-readonly-sections on
12839 Tell @value{GDBN} that readonly sections in your object file
12840 really are read-only (i.e.@: that their contents will not change).
12841 In that case, @value{GDBN} can fetch values from these sections
12842 out of the object file, rather than from the target program.
12843 For some targets (notably embedded ones), this can be a significant
12844 enhancement to debugging performance.
12846 The default is off.
12848 @item set trust-readonly-sections off
12849 Tell @value{GDBN} not to trust readonly sections. This means that
12850 the contents of the section might change while the program is running,
12851 and must therefore be fetched from the target when needed.
12853 @item show trust-readonly-sections
12854 Show the current setting of trusting readonly sections.
12857 All file-specifying commands allow both absolute and relative file names
12858 as arguments. @value{GDBN} always converts the file name to an absolute file
12859 name and remembers it that way.
12861 @cindex shared libraries
12862 @anchor{Shared Libraries}
12863 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12864 and IBM RS/6000 AIX shared libraries.
12866 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12867 shared libraries. @xref{Expat}.
12869 @value{GDBN} automatically loads symbol definitions from shared libraries
12870 when you use the @code{run} command, or when you examine a core file.
12871 (Before you issue the @code{run} command, @value{GDBN} does not understand
12872 references to a function in a shared library, however---unless you are
12873 debugging a core file).
12875 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12876 automatically loads the symbols at the time of the @code{shl_load} call.
12878 @c FIXME: some @value{GDBN} release may permit some refs to undef
12879 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12880 @c FIXME...lib; check this from time to time when updating manual
12882 There are times, however, when you may wish to not automatically load
12883 symbol definitions from shared libraries, such as when they are
12884 particularly large or there are many of them.
12886 To control the automatic loading of shared library symbols, use the
12890 @kindex set auto-solib-add
12891 @item set auto-solib-add @var{mode}
12892 If @var{mode} is @code{on}, symbols from all shared object libraries
12893 will be loaded automatically when the inferior begins execution, you
12894 attach to an independently started inferior, or when the dynamic linker
12895 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12896 is @code{off}, symbols must be loaded manually, using the
12897 @code{sharedlibrary} command. The default value is @code{on}.
12899 @cindex memory used for symbol tables
12900 If your program uses lots of shared libraries with debug info that
12901 takes large amounts of memory, you can decrease the @value{GDBN}
12902 memory footprint by preventing it from automatically loading the
12903 symbols from shared libraries. To that end, type @kbd{set
12904 auto-solib-add off} before running the inferior, then load each
12905 library whose debug symbols you do need with @kbd{sharedlibrary
12906 @var{regexp}}, where @var{regexp} is a regular expression that matches
12907 the libraries whose symbols you want to be loaded.
12909 @kindex show auto-solib-add
12910 @item show auto-solib-add
12911 Display the current autoloading mode.
12914 @cindex load shared library
12915 To explicitly load shared library symbols, use the @code{sharedlibrary}
12919 @kindex info sharedlibrary
12922 @itemx info sharedlibrary
12923 Print the names of the shared libraries which are currently loaded.
12925 @kindex sharedlibrary
12927 @item sharedlibrary @var{regex}
12928 @itemx share @var{regex}
12929 Load shared object library symbols for files matching a
12930 Unix regular expression.
12931 As with files loaded automatically, it only loads shared libraries
12932 required by your program for a core file or after typing @code{run}. If
12933 @var{regex} is omitted all shared libraries required by your program are
12936 @item nosharedlibrary
12937 @kindex nosharedlibrary
12938 @cindex unload symbols from shared libraries
12939 Unload all shared object library symbols. This discards all symbols
12940 that have been loaded from all shared libraries. Symbols from shared
12941 libraries that were loaded by explicit user requests are not
12945 Sometimes you may wish that @value{GDBN} stops and gives you control
12946 when any of shared library events happen. Use the @code{set
12947 stop-on-solib-events} command for this:
12950 @item set stop-on-solib-events
12951 @kindex set stop-on-solib-events
12952 This command controls whether @value{GDBN} should give you control
12953 when the dynamic linker notifies it about some shared library event.
12954 The most common event of interest is loading or unloading of a new
12957 @item show stop-on-solib-events
12958 @kindex show stop-on-solib-events
12959 Show whether @value{GDBN} stops and gives you control when shared
12960 library events happen.
12963 Shared libraries are also supported in many cross or remote debugging
12964 configurations. @value{GDBN} needs to have access to the target's libraries;
12965 this can be accomplished either by providing copies of the libraries
12966 on the host system, or by asking @value{GDBN} to automatically retrieve the
12967 libraries from the target. If copies of the target libraries are
12968 provided, they need to be the same as the target libraries, although the
12969 copies on the target can be stripped as long as the copies on the host are
12972 @cindex where to look for shared libraries
12973 For remote debugging, you need to tell @value{GDBN} where the target
12974 libraries are, so that it can load the correct copies---otherwise, it
12975 may try to load the host's libraries. @value{GDBN} has two variables
12976 to specify the search directories for target libraries.
12979 @cindex prefix for shared library file names
12980 @cindex system root, alternate
12981 @kindex set solib-absolute-prefix
12982 @kindex set sysroot
12983 @item set sysroot @var{path}
12984 Use @var{path} as the system root for the program being debugged. Any
12985 absolute shared library paths will be prefixed with @var{path}; many
12986 runtime loaders store the absolute paths to the shared library in the
12987 target program's memory. If you use @code{set sysroot} to find shared
12988 libraries, they need to be laid out in the same way that they are on
12989 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12992 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
12993 retrieve the target libraries from the remote system. This is only
12994 supported when using a remote target that supports the @code{remote get}
12995 command (@pxref{File Transfer,,Sending files to a remote system}).
12996 The part of @var{path} following the initial @file{remote:}
12997 (if present) is used as system root prefix on the remote file system.
12998 @footnote{If you want to specify a local system root using a directory
12999 that happens to be named @file{remote:}, you need to use some equivalent
13000 variant of the name like @file{./remote:}.}
13002 The @code{set solib-absolute-prefix} command is an alias for @code{set
13005 @cindex default system root
13006 @cindex @samp{--with-sysroot}
13007 You can set the default system root by using the configure-time
13008 @samp{--with-sysroot} option. If the system root is inside
13009 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13010 @samp{--exec-prefix}), then the default system root will be updated
13011 automatically if the installed @value{GDBN} is moved to a new
13014 @kindex show sysroot
13016 Display the current shared library prefix.
13018 @kindex set solib-search-path
13019 @item set solib-search-path @var{path}
13020 If this variable is set, @var{path} is a colon-separated list of
13021 directories to search for shared libraries. @samp{solib-search-path}
13022 is used after @samp{sysroot} fails to locate the library, or if the
13023 path to the library is relative instead of absolute. If you want to
13024 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13025 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13026 finding your host's libraries. @samp{sysroot} is preferred; setting
13027 it to a nonexistent directory may interfere with automatic loading
13028 of shared library symbols.
13030 @kindex show solib-search-path
13031 @item show solib-search-path
13032 Display the current shared library search path.
13036 @node Separate Debug Files
13037 @section Debugging Information in Separate Files
13038 @cindex separate debugging information files
13039 @cindex debugging information in separate files
13040 @cindex @file{.debug} subdirectories
13041 @cindex debugging information directory, global
13042 @cindex global debugging information directory
13043 @cindex build ID, and separate debugging files
13044 @cindex @file{.build-id} directory
13046 @value{GDBN} allows you to put a program's debugging information in a
13047 file separate from the executable itself, in a way that allows
13048 @value{GDBN} to find and load the debugging information automatically.
13049 Since debugging information can be very large---sometimes larger
13050 than the executable code itself---some systems distribute debugging
13051 information for their executables in separate files, which users can
13052 install only when they need to debug a problem.
13054 @value{GDBN} supports two ways of specifying the separate debug info
13059 The executable contains a @dfn{debug link} that specifies the name of
13060 the separate debug info file. The separate debug file's name is
13061 usually @file{@var{executable}.debug}, where @var{executable} is the
13062 name of the corresponding executable file without leading directories
13063 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13064 debug link specifies a CRC32 checksum for the debug file, which
13065 @value{GDBN} uses to validate that the executable and the debug file
13066 came from the same build.
13069 The executable contains a @dfn{build ID}, a unique bit string that is
13070 also present in the corresponding debug info file. (This is supported
13071 only on some operating systems, notably those which use the ELF format
13072 for binary files and the @sc{gnu} Binutils.) For more details about
13073 this feature, see the description of the @option{--build-id}
13074 command-line option in @ref{Options, , Command Line Options, ld.info,
13075 The GNU Linker}. The debug info file's name is not specified
13076 explicitly by the build ID, but can be computed from the build ID, see
13080 Depending on the way the debug info file is specified, @value{GDBN}
13081 uses two different methods of looking for the debug file:
13085 For the ``debug link'' method, @value{GDBN} looks up the named file in
13086 the directory of the executable file, then in a subdirectory of that
13087 directory named @file{.debug}, and finally under the global debug
13088 directory, in a subdirectory whose name is identical to the leading
13089 directories of the executable's absolute file name.
13092 For the ``build ID'' method, @value{GDBN} looks in the
13093 @file{.build-id} subdirectory of the global debug directory for a file
13094 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13095 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13096 are the rest of the bit string. (Real build ID strings are 32 or more
13097 hex characters, not 10.)
13100 So, for example, suppose you ask @value{GDBN} to debug
13101 @file{/usr/bin/ls}, which has a debug link that specifies the
13102 file @file{ls.debug}, and a build ID whose value in hex is
13103 @code{abcdef1234}. If the global debug directory is
13104 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13105 debug information files, in the indicated order:
13109 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13111 @file{/usr/bin/ls.debug}
13113 @file{/usr/bin/.debug/ls.debug}
13115 @file{/usr/lib/debug/usr/bin/ls.debug}.
13118 You can set the global debugging info directory's name, and view the
13119 name @value{GDBN} is currently using.
13123 @kindex set debug-file-directory
13124 @item set debug-file-directory @var{directory}
13125 Set the directory which @value{GDBN} searches for separate debugging
13126 information files to @var{directory}.
13128 @kindex show debug-file-directory
13129 @item show debug-file-directory
13130 Show the directory @value{GDBN} searches for separate debugging
13135 @cindex @code{.gnu_debuglink} sections
13136 @cindex debug link sections
13137 A debug link is a special section of the executable file named
13138 @code{.gnu_debuglink}. The section must contain:
13142 A filename, with any leading directory components removed, followed by
13145 zero to three bytes of padding, as needed to reach the next four-byte
13146 boundary within the section, and
13148 a four-byte CRC checksum, stored in the same endianness used for the
13149 executable file itself. The checksum is computed on the debugging
13150 information file's full contents by the function given below, passing
13151 zero as the @var{crc} argument.
13154 Any executable file format can carry a debug link, as long as it can
13155 contain a section named @code{.gnu_debuglink} with the contents
13158 @cindex @code{.note.gnu.build-id} sections
13159 @cindex build ID sections
13160 The build ID is a special section in the executable file (and in other
13161 ELF binary files that @value{GDBN} may consider). This section is
13162 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13163 It contains unique identification for the built files---the ID remains
13164 the same across multiple builds of the same build tree. The default
13165 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13166 content for the build ID string. The same section with an identical
13167 value is present in the original built binary with symbols, in its
13168 stripped variant, and in the separate debugging information file.
13170 The debugging information file itself should be an ordinary
13171 executable, containing a full set of linker symbols, sections, and
13172 debugging information. The sections of the debugging information file
13173 should have the same names, addresses, and sizes as the original file,
13174 but they need not contain any data---much like a @code{.bss} section
13175 in an ordinary executable.
13177 The @sc{gnu} binary utilities (Binutils) package includes the
13178 @samp{objcopy} utility that can produce
13179 the separated executable / debugging information file pairs using the
13180 following commands:
13183 @kbd{objcopy --only-keep-debug foo foo.debug}
13188 These commands remove the debugging
13189 information from the executable file @file{foo} and place it in the file
13190 @file{foo.debug}. You can use the first, second or both methods to link the
13195 The debug link method needs the following additional command to also leave
13196 behind a debug link in @file{foo}:
13199 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13202 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13203 a version of the @code{strip} command such that the command @kbd{strip foo -f
13204 foo.debug} has the same functionality as the two @code{objcopy} commands and
13205 the @code{ln -s} command above, together.
13208 Build ID gets embedded into the main executable using @code{ld --build-id} or
13209 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13210 compatibility fixes for debug files separation are present in @sc{gnu} binary
13211 utilities (Binutils) package since version 2.18.
13216 Since there are many different ways to compute CRC's for the debug
13217 link (different polynomials, reversals, byte ordering, etc.), the
13218 simplest way to describe the CRC used in @code{.gnu_debuglink}
13219 sections is to give the complete code for a function that computes it:
13221 @kindex gnu_debuglink_crc32
13224 gnu_debuglink_crc32 (unsigned long crc,
13225 unsigned char *buf, size_t len)
13227 static const unsigned long crc32_table[256] =
13229 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13230 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13231 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13232 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13233 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13234 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13235 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13236 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13237 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13238 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13239 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13240 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13241 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13242 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13243 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13244 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13245 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13246 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13247 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13248 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13249 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13250 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13251 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13252 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13253 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13254 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13255 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13256 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13257 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13258 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13259 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13260 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13261 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13262 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13263 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13264 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13265 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13266 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13267 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13268 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13269 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13270 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13271 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13272 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13273 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13274 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13275 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13276 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13277 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13278 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13279 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13282 unsigned char *end;
13284 crc = ~crc & 0xffffffff;
13285 for (end = buf + len; buf < end; ++buf)
13286 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13287 return ~crc & 0xffffffff;
13292 This computation does not apply to the ``build ID'' method.
13295 @node Symbol Errors
13296 @section Errors Reading Symbol Files
13298 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13299 such as symbol types it does not recognize, or known bugs in compiler
13300 output. By default, @value{GDBN} does not notify you of such problems, since
13301 they are relatively common and primarily of interest to people
13302 debugging compilers. If you are interested in seeing information
13303 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13304 only one message about each such type of problem, no matter how many
13305 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13306 to see how many times the problems occur, with the @code{set
13307 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13310 The messages currently printed, and their meanings, include:
13313 @item inner block not inside outer block in @var{symbol}
13315 The symbol information shows where symbol scopes begin and end
13316 (such as at the start of a function or a block of statements). This
13317 error indicates that an inner scope block is not fully contained
13318 in its outer scope blocks.
13320 @value{GDBN} circumvents the problem by treating the inner block as if it had
13321 the same scope as the outer block. In the error message, @var{symbol}
13322 may be shown as ``@code{(don't know)}'' if the outer block is not a
13325 @item block at @var{address} out of order
13327 The symbol information for symbol scope blocks should occur in
13328 order of increasing addresses. This error indicates that it does not
13331 @value{GDBN} does not circumvent this problem, and has trouble
13332 locating symbols in the source file whose symbols it is reading. (You
13333 can often determine what source file is affected by specifying
13334 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13337 @item bad block start address patched
13339 The symbol information for a symbol scope block has a start address
13340 smaller than the address of the preceding source line. This is known
13341 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13343 @value{GDBN} circumvents the problem by treating the symbol scope block as
13344 starting on the previous source line.
13346 @item bad string table offset in symbol @var{n}
13349 Symbol number @var{n} contains a pointer into the string table which is
13350 larger than the size of the string table.
13352 @value{GDBN} circumvents the problem by considering the symbol to have the
13353 name @code{foo}, which may cause other problems if many symbols end up
13356 @item unknown symbol type @code{0x@var{nn}}
13358 The symbol information contains new data types that @value{GDBN} does
13359 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13360 uncomprehended information, in hexadecimal.
13362 @value{GDBN} circumvents the error by ignoring this symbol information.
13363 This usually allows you to debug your program, though certain symbols
13364 are not accessible. If you encounter such a problem and feel like
13365 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13366 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13367 and examine @code{*bufp} to see the symbol.
13369 @item stub type has NULL name
13371 @value{GDBN} could not find the full definition for a struct or class.
13373 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13374 The symbol information for a C@t{++} member function is missing some
13375 information that recent versions of the compiler should have output for
13378 @item info mismatch between compiler and debugger
13380 @value{GDBN} could not parse a type specification output by the compiler.
13385 @chapter Specifying a Debugging Target
13387 @cindex debugging target
13388 A @dfn{target} is the execution environment occupied by your program.
13390 Often, @value{GDBN} runs in the same host environment as your program;
13391 in that case, the debugging target is specified as a side effect when
13392 you use the @code{file} or @code{core} commands. When you need more
13393 flexibility---for example, running @value{GDBN} on a physically separate
13394 host, or controlling a standalone system over a serial port or a
13395 realtime system over a TCP/IP connection---you can use the @code{target}
13396 command to specify one of the target types configured for @value{GDBN}
13397 (@pxref{Target Commands, ,Commands for Managing Targets}).
13399 @cindex target architecture
13400 It is possible to build @value{GDBN} for several different @dfn{target
13401 architectures}. When @value{GDBN} is built like that, you can choose
13402 one of the available architectures with the @kbd{set architecture}
13406 @kindex set architecture
13407 @kindex show architecture
13408 @item set architecture @var{arch}
13409 This command sets the current target architecture to @var{arch}. The
13410 value of @var{arch} can be @code{"auto"}, in addition to one of the
13411 supported architectures.
13413 @item show architecture
13414 Show the current target architecture.
13416 @item set processor
13418 @kindex set processor
13419 @kindex show processor
13420 These are alias commands for, respectively, @code{set architecture}
13421 and @code{show architecture}.
13425 * Active Targets:: Active targets
13426 * Target Commands:: Commands for managing targets
13427 * Byte Order:: Choosing target byte order
13430 @node Active Targets
13431 @section Active Targets
13433 @cindex stacking targets
13434 @cindex active targets
13435 @cindex multiple targets
13437 There are three classes of targets: processes, core files, and
13438 executable files. @value{GDBN} can work concurrently on up to three
13439 active targets, one in each class. This allows you to (for example)
13440 start a process and inspect its activity without abandoning your work on
13443 For example, if you execute @samp{gdb a.out}, then the executable file
13444 @code{a.out} is the only active target. If you designate a core file as
13445 well---presumably from a prior run that crashed and coredumped---then
13446 @value{GDBN} has two active targets and uses them in tandem, looking
13447 first in the corefile target, then in the executable file, to satisfy
13448 requests for memory addresses. (Typically, these two classes of target
13449 are complementary, since core files contain only a program's
13450 read-write memory---variables and so on---plus machine status, while
13451 executable files contain only the program text and initialized data.)
13453 When you type @code{run}, your executable file becomes an active process
13454 target as well. When a process target is active, all @value{GDBN}
13455 commands requesting memory addresses refer to that target; addresses in
13456 an active core file or executable file target are obscured while the
13457 process target is active.
13459 Use the @code{core-file} and @code{exec-file} commands to select a new
13460 core file or executable target (@pxref{Files, ,Commands to Specify
13461 Files}). To specify as a target a process that is already running, use
13462 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13465 @node Target Commands
13466 @section Commands for Managing Targets
13469 @item target @var{type} @var{parameters}
13470 Connects the @value{GDBN} host environment to a target machine or
13471 process. A target is typically a protocol for talking to debugging
13472 facilities. You use the argument @var{type} to specify the type or
13473 protocol of the target machine.
13475 Further @var{parameters} are interpreted by the target protocol, but
13476 typically include things like device names or host names to connect
13477 with, process numbers, and baud rates.
13479 The @code{target} command does not repeat if you press @key{RET} again
13480 after executing the command.
13482 @kindex help target
13484 Displays the names of all targets available. To display targets
13485 currently selected, use either @code{info target} or @code{info files}
13486 (@pxref{Files, ,Commands to Specify Files}).
13488 @item help target @var{name}
13489 Describe a particular target, including any parameters necessary to
13492 @kindex set gnutarget
13493 @item set gnutarget @var{args}
13494 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13495 knows whether it is reading an @dfn{executable},
13496 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13497 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13498 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13501 @emph{Warning:} To specify a file format with @code{set gnutarget},
13502 you must know the actual BFD name.
13506 @xref{Files, , Commands to Specify Files}.
13508 @kindex show gnutarget
13509 @item show gnutarget
13510 Use the @code{show gnutarget} command to display what file format
13511 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13512 @value{GDBN} will determine the file format for each file automatically,
13513 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13516 @cindex common targets
13517 Here are some common targets (available, or not, depending on the GDB
13522 @item target exec @var{program}
13523 @cindex executable file target
13524 An executable file. @samp{target exec @var{program}} is the same as
13525 @samp{exec-file @var{program}}.
13527 @item target core @var{filename}
13528 @cindex core dump file target
13529 A core dump file. @samp{target core @var{filename}} is the same as
13530 @samp{core-file @var{filename}}.
13532 @item target remote @var{medium}
13533 @cindex remote target
13534 A remote system connected to @value{GDBN} via a serial line or network
13535 connection. This command tells @value{GDBN} to use its own remote
13536 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13538 For example, if you have a board connected to @file{/dev/ttya} on the
13539 machine running @value{GDBN}, you could say:
13542 target remote /dev/ttya
13545 @code{target remote} supports the @code{load} command. This is only
13546 useful if you have some other way of getting the stub to the target
13547 system, and you can put it somewhere in memory where it won't get
13548 clobbered by the download.
13551 @cindex built-in simulator target
13552 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13560 works; however, you cannot assume that a specific memory map, device
13561 drivers, or even basic I/O is available, although some simulators do
13562 provide these. For info about any processor-specific simulator details,
13563 see the appropriate section in @ref{Embedded Processors, ,Embedded
13568 Some configurations may include these targets as well:
13572 @item target nrom @var{dev}
13573 @cindex NetROM ROM emulator target
13574 NetROM ROM emulator. This target only supports downloading.
13578 Different targets are available on different configurations of @value{GDBN};
13579 your configuration may have more or fewer targets.
13581 Many remote targets require you to download the executable's code once
13582 you've successfully established a connection. You may wish to control
13583 various aspects of this process.
13588 @kindex set hash@r{, for remote monitors}
13589 @cindex hash mark while downloading
13590 This command controls whether a hash mark @samp{#} is displayed while
13591 downloading a file to the remote monitor. If on, a hash mark is
13592 displayed after each S-record is successfully downloaded to the
13596 @kindex show hash@r{, for remote monitors}
13597 Show the current status of displaying the hash mark.
13599 @item set debug monitor
13600 @kindex set debug monitor
13601 @cindex display remote monitor communications
13602 Enable or disable display of communications messages between
13603 @value{GDBN} and the remote monitor.
13605 @item show debug monitor
13606 @kindex show debug monitor
13607 Show the current status of displaying communications between
13608 @value{GDBN} and the remote monitor.
13613 @kindex load @var{filename}
13614 @item load @var{filename}
13616 Depending on what remote debugging facilities are configured into
13617 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13618 is meant to make @var{filename} (an executable) available for debugging
13619 on the remote system---by downloading, or dynamic linking, for example.
13620 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13621 the @code{add-symbol-file} command.
13623 If your @value{GDBN} does not have a @code{load} command, attempting to
13624 execute it gets the error message ``@code{You can't do that when your
13625 target is @dots{}}''
13627 The file is loaded at whatever address is specified in the executable.
13628 For some object file formats, you can specify the load address when you
13629 link the program; for other formats, like a.out, the object file format
13630 specifies a fixed address.
13631 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13633 Depending on the remote side capabilities, @value{GDBN} may be able to
13634 load programs into flash memory.
13636 @code{load} does not repeat if you press @key{RET} again after using it.
13640 @section Choosing Target Byte Order
13642 @cindex choosing target byte order
13643 @cindex target byte order
13645 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13646 offer the ability to run either big-endian or little-endian byte
13647 orders. Usually the executable or symbol will include a bit to
13648 designate the endian-ness, and you will not need to worry about
13649 which to use. However, you may still find it useful to adjust
13650 @value{GDBN}'s idea of processor endian-ness manually.
13654 @item set endian big
13655 Instruct @value{GDBN} to assume the target is big-endian.
13657 @item set endian little
13658 Instruct @value{GDBN} to assume the target is little-endian.
13660 @item set endian auto
13661 Instruct @value{GDBN} to use the byte order associated with the
13665 Display @value{GDBN}'s current idea of the target byte order.
13669 Note that these commands merely adjust interpretation of symbolic
13670 data on the host, and that they have absolutely no effect on the
13674 @node Remote Debugging
13675 @chapter Debugging Remote Programs
13676 @cindex remote debugging
13678 If you are trying to debug a program running on a machine that cannot run
13679 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13680 For example, you might use remote debugging on an operating system kernel,
13681 or on a small system which does not have a general purpose operating system
13682 powerful enough to run a full-featured debugger.
13684 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13685 to make this work with particular debugging targets. In addition,
13686 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13687 but not specific to any particular target system) which you can use if you
13688 write the remote stubs---the code that runs on the remote system to
13689 communicate with @value{GDBN}.
13691 Other remote targets may be available in your
13692 configuration of @value{GDBN}; use @code{help target} to list them.
13695 * Connecting:: Connecting to a remote target
13696 * File Transfer:: Sending files to a remote system
13697 * Server:: Using the gdbserver program
13698 * Remote Configuration:: Remote configuration
13699 * Remote Stub:: Implementing a remote stub
13703 @section Connecting to a Remote Target
13705 On the @value{GDBN} host machine, you will need an unstripped copy of
13706 your program, since @value{GDBN} needs symbol and debugging information.
13707 Start up @value{GDBN} as usual, using the name of the local copy of your
13708 program as the first argument.
13710 @cindex @code{target remote}
13711 @value{GDBN} can communicate with the target over a serial line, or
13712 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13713 each case, @value{GDBN} uses the same protocol for debugging your
13714 program; only the medium carrying the debugging packets varies. The
13715 @code{target remote} command establishes a connection to the target.
13716 Its arguments indicate which medium to use:
13720 @item target remote @var{serial-device}
13721 @cindex serial line, @code{target remote}
13722 Use @var{serial-device} to communicate with the target. For example,
13723 to use a serial line connected to the device named @file{/dev/ttyb}:
13726 target remote /dev/ttyb
13729 If you're using a serial line, you may want to give @value{GDBN} the
13730 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13731 (@pxref{Remote Configuration, set remotebaud}) before the
13732 @code{target} command.
13734 @item target remote @code{@var{host}:@var{port}}
13735 @itemx target remote @code{tcp:@var{host}:@var{port}}
13736 @cindex @acronym{TCP} port, @code{target remote}
13737 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13738 The @var{host} may be either a host name or a numeric @acronym{IP}
13739 address; @var{port} must be a decimal number. The @var{host} could be
13740 the target machine itself, if it is directly connected to the net, or
13741 it might be a terminal server which in turn has a serial line to the
13744 For example, to connect to port 2828 on a terminal server named
13748 target remote manyfarms:2828
13751 If your remote target is actually running on the same machine as your
13752 debugger session (e.g.@: a simulator for your target running on the
13753 same host), you can omit the hostname. For example, to connect to
13754 port 1234 on your local machine:
13757 target remote :1234
13761 Note that the colon is still required here.
13763 @item target remote @code{udp:@var{host}:@var{port}}
13764 @cindex @acronym{UDP} port, @code{target remote}
13765 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13766 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13769 target remote udp:manyfarms:2828
13772 When using a @acronym{UDP} connection for remote debugging, you should
13773 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13774 can silently drop packets on busy or unreliable networks, which will
13775 cause havoc with your debugging session.
13777 @item target remote | @var{command}
13778 @cindex pipe, @code{target remote} to
13779 Run @var{command} in the background and communicate with it using a
13780 pipe. The @var{command} is a shell command, to be parsed and expanded
13781 by the system's command shell, @code{/bin/sh}; it should expect remote
13782 protocol packets on its standard input, and send replies on its
13783 standard output. You could use this to run a stand-alone simulator
13784 that speaks the remote debugging protocol, to make net connections
13785 using programs like @code{ssh}, or for other similar tricks.
13787 If @var{command} closes its standard output (perhaps by exiting),
13788 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13789 program has already exited, this will have no effect.)
13793 Once the connection has been established, you can use all the usual
13794 commands to examine and change data. The remote program is already
13795 running; you can use @kbd{step} and @kbd{continue}, and you do not
13796 need to use @kbd{run}.
13798 @cindex interrupting remote programs
13799 @cindex remote programs, interrupting
13800 Whenever @value{GDBN} is waiting for the remote program, if you type the
13801 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13802 program. This may or may not succeed, depending in part on the hardware
13803 and the serial drivers the remote system uses. If you type the
13804 interrupt character once again, @value{GDBN} displays this prompt:
13807 Interrupted while waiting for the program.
13808 Give up (and stop debugging it)? (y or n)
13811 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13812 (If you decide you want to try again later, you can use @samp{target
13813 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13814 goes back to waiting.
13817 @kindex detach (remote)
13819 When you have finished debugging the remote program, you can use the
13820 @code{detach} command to release it from @value{GDBN} control.
13821 Detaching from the target normally resumes its execution, but the results
13822 will depend on your particular remote stub. After the @code{detach}
13823 command, @value{GDBN} is free to connect to another target.
13827 The @code{disconnect} command behaves like @code{detach}, except that
13828 the target is generally not resumed. It will wait for @value{GDBN}
13829 (this instance or another one) to connect and continue debugging. After
13830 the @code{disconnect} command, @value{GDBN} is again free to connect to
13833 @cindex send command to remote monitor
13834 @cindex extend @value{GDBN} for remote targets
13835 @cindex add new commands for external monitor
13837 @item monitor @var{cmd}
13838 This command allows you to send arbitrary commands directly to the
13839 remote monitor. Since @value{GDBN} doesn't care about the commands it
13840 sends like this, this command is the way to extend @value{GDBN}---you
13841 can add new commands that only the external monitor will understand
13845 @node File Transfer
13846 @section Sending files to a remote system
13847 @cindex remote target, file transfer
13848 @cindex file transfer
13849 @cindex sending files to remote systems
13851 Some remote targets offer the ability to transfer files over the same
13852 connection used to communicate with @value{GDBN}. This is convenient
13853 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13854 running @code{gdbserver} over a network interface. For other targets,
13855 e.g.@: embedded devices with only a single serial port, this may be
13856 the only way to upload or download files.
13858 Not all remote targets support these commands.
13862 @item remote put @var{hostfile} @var{targetfile}
13863 Copy file @var{hostfile} from the host system (the machine running
13864 @value{GDBN}) to @var{targetfile} on the target system.
13867 @item remote get @var{targetfile} @var{hostfile}
13868 Copy file @var{targetfile} from the target system to @var{hostfile}
13869 on the host system.
13871 @kindex remote delete
13872 @item remote delete @var{targetfile}
13873 Delete @var{targetfile} from the target system.
13878 @section Using the @code{gdbserver} Program
13881 @cindex remote connection without stubs
13882 @code{gdbserver} is a control program for Unix-like systems, which
13883 allows you to connect your program with a remote @value{GDBN} via
13884 @code{target remote}---but without linking in the usual debugging stub.
13886 @code{gdbserver} is not a complete replacement for the debugging stubs,
13887 because it requires essentially the same operating-system facilities
13888 that @value{GDBN} itself does. In fact, a system that can run
13889 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13890 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13891 because it is a much smaller program than @value{GDBN} itself. It is
13892 also easier to port than all of @value{GDBN}, so you may be able to get
13893 started more quickly on a new system by using @code{gdbserver}.
13894 Finally, if you develop code for real-time systems, you may find that
13895 the tradeoffs involved in real-time operation make it more convenient to
13896 do as much development work as possible on another system, for example
13897 by cross-compiling. You can use @code{gdbserver} to make a similar
13898 choice for debugging.
13900 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13901 or a TCP connection, using the standard @value{GDBN} remote serial
13905 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13906 Do not run @code{gdbserver} connected to any public network; a
13907 @value{GDBN} connection to @code{gdbserver} provides access to the
13908 target system with the same privileges as the user running
13912 @subsection Running @code{gdbserver}
13913 @cindex arguments, to @code{gdbserver}
13915 Run @code{gdbserver} on the target system. You need a copy of the
13916 program you want to debug, including any libraries it requires.
13917 @code{gdbserver} does not need your program's symbol table, so you can
13918 strip the program if necessary to save space. @value{GDBN} on the host
13919 system does all the symbol handling.
13921 To use the server, you must tell it how to communicate with @value{GDBN};
13922 the name of your program; and the arguments for your program. The usual
13926 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13929 @var{comm} is either a device name (to use a serial line) or a TCP
13930 hostname and portnumber. For example, to debug Emacs with the argument
13931 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13935 target> gdbserver /dev/com1 emacs foo.txt
13938 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13941 To use a TCP connection instead of a serial line:
13944 target> gdbserver host:2345 emacs foo.txt
13947 The only difference from the previous example is the first argument,
13948 specifying that you are communicating with the host @value{GDBN} via
13949 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13950 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13951 (Currently, the @samp{host} part is ignored.) You can choose any number
13952 you want for the port number as long as it does not conflict with any
13953 TCP ports already in use on the target system (for example, @code{23} is
13954 reserved for @code{telnet}).@footnote{If you choose a port number that
13955 conflicts with another service, @code{gdbserver} prints an error message
13956 and exits.} You must use the same port number with the host @value{GDBN}
13957 @code{target remote} command.
13959 @subsubsection Attaching to a Running Program
13961 On some targets, @code{gdbserver} can also attach to running programs.
13962 This is accomplished via the @code{--attach} argument. The syntax is:
13965 target> gdbserver --attach @var{comm} @var{pid}
13968 @var{pid} is the process ID of a currently running process. It isn't necessary
13969 to point @code{gdbserver} at a binary for the running process.
13972 @cindex attach to a program by name
13973 You can debug processes by name instead of process ID if your target has the
13974 @code{pidof} utility:
13977 target> gdbserver --attach @var{comm} `pidof @var{program}`
13980 In case more than one copy of @var{program} is running, or @var{program}
13981 has multiple threads, most versions of @code{pidof} support the
13982 @code{-s} option to only return the first process ID.
13984 @subsubsection Multi-Process Mode for @code{gdbserver}
13985 @cindex gdbserver, multiple processes
13986 @cindex multiple processes with gdbserver
13988 When you connect to @code{gdbserver} using @code{target remote},
13989 @code{gdbserver} debugs the specified program only once. When the
13990 program exits, or you detach from it, @value{GDBN} closes the connection
13991 and @code{gdbserver} exits.
13993 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13994 enters multi-process mode. When the debugged program exits, or you
13995 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13996 though no program is running. The @code{run} and @code{attach}
13997 commands instruct @code{gdbserver} to run or attach to a new program.
13998 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13999 remote exec-file}) to select the program to run. Command line
14000 arguments are supported, except for wildcard expansion and I/O
14001 redirection (@pxref{Arguments}).
14003 To start @code{gdbserver} without supplying an initial command to run
14004 or process ID to attach, use the @option{--multi} command line option.
14005 Then you can connect using @kbd{target extended-remote} and start
14006 the program you want to debug.
14008 @code{gdbserver} does not automatically exit in multi-process mode.
14009 You can terminate it by using @code{monitor exit}
14010 (@pxref{Monitor Commands for gdbserver}).
14012 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14014 You can include @option{--debug} on the @code{gdbserver} command line.
14015 @code{gdbserver} will display extra status information about the debugging
14016 process. This option is intended for @code{gdbserver} development and
14017 for bug reports to the developers.
14019 The @option{--wrapper} option specifies a wrapper to launch programs
14020 for debugging. The option should be followed by the name of the
14021 wrapper, then any command-line arguments to pass to the wrapper, then
14022 @kbd{--} indicating the end of the wrapper arguments.
14024 @code{gdbserver} runs the specified wrapper program with a combined
14025 command line including the wrapper arguments, then the name of the
14026 program to debug, then any arguments to the program. The wrapper
14027 runs until it executes your program, and then @value{GDBN} gains control.
14029 You can use any program that eventually calls @code{execve} with
14030 its arguments as a wrapper. Several standard Unix utilities do
14031 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14032 with @code{exec "$@@"} will also work.
14034 For example, you can use @code{env} to pass an environment variable to
14035 the debugged program, without setting the variable in @code{gdbserver}'s
14039 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14042 @subsection Connecting to @code{gdbserver}
14044 Run @value{GDBN} on the host system.
14046 First make sure you have the necessary symbol files. Load symbols for
14047 your application using the @code{file} command before you connect. Use
14048 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14049 was compiled with the correct sysroot using @code{--with-sysroot}).
14051 The symbol file and target libraries must exactly match the executable
14052 and libraries on the target, with one exception: the files on the host
14053 system should not be stripped, even if the files on the target system
14054 are. Mismatched or missing files will lead to confusing results
14055 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14056 files may also prevent @code{gdbserver} from debugging multi-threaded
14059 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14060 For TCP connections, you must start up @code{gdbserver} prior to using
14061 the @code{target remote} command. Otherwise you may get an error whose
14062 text depends on the host system, but which usually looks something like
14063 @samp{Connection refused}. Don't use the @code{load}
14064 command in @value{GDBN} when using @code{gdbserver}, since the program is
14065 already on the target.
14067 @subsection Monitor Commands for @code{gdbserver}
14068 @cindex monitor commands, for @code{gdbserver}
14069 @anchor{Monitor Commands for gdbserver}
14071 During a @value{GDBN} session using @code{gdbserver}, you can use the
14072 @code{monitor} command to send special requests to @code{gdbserver}.
14073 Here are the available commands.
14077 List the available monitor commands.
14079 @item monitor set debug 0
14080 @itemx monitor set debug 1
14081 Disable or enable general debugging messages.
14083 @item monitor set remote-debug 0
14084 @itemx monitor set remote-debug 1
14085 Disable or enable specific debugging messages associated with the remote
14086 protocol (@pxref{Remote Protocol}).
14089 Tell gdbserver to exit immediately. This command should be followed by
14090 @code{disconnect} to close the debugging session. @code{gdbserver} will
14091 detach from any attached processes and kill any processes it created.
14092 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14093 of a multi-process mode debug session.
14097 @node Remote Configuration
14098 @section Remote Configuration
14101 @kindex show remote
14102 This section documents the configuration options available when
14103 debugging remote programs. For the options related to the File I/O
14104 extensions of the remote protocol, see @ref{system,
14105 system-call-allowed}.
14108 @item set remoteaddresssize @var{bits}
14109 @cindex address size for remote targets
14110 @cindex bits in remote address
14111 Set the maximum size of address in a memory packet to the specified
14112 number of bits. @value{GDBN} will mask off the address bits above
14113 that number, when it passes addresses to the remote target. The
14114 default value is the number of bits in the target's address.
14116 @item show remoteaddresssize
14117 Show the current value of remote address size in bits.
14119 @item set remotebaud @var{n}
14120 @cindex baud rate for remote targets
14121 Set the baud rate for the remote serial I/O to @var{n} baud. The
14122 value is used to set the speed of the serial port used for debugging
14125 @item show remotebaud
14126 Show the current speed of the remote connection.
14128 @item set remotebreak
14129 @cindex interrupt remote programs
14130 @cindex BREAK signal instead of Ctrl-C
14131 @anchor{set remotebreak}
14132 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14133 when you type @kbd{Ctrl-c} to interrupt the program running
14134 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14135 character instead. The default is off, since most remote systems
14136 expect to see @samp{Ctrl-C} as the interrupt signal.
14138 @item show remotebreak
14139 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14140 interrupt the remote program.
14142 @item set remoteflow on
14143 @itemx set remoteflow off
14144 @kindex set remoteflow
14145 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14146 on the serial port used to communicate to the remote target.
14148 @item show remoteflow
14149 @kindex show remoteflow
14150 Show the current setting of hardware flow control.
14152 @item set remotelogbase @var{base}
14153 Set the base (a.k.a.@: radix) of logging serial protocol
14154 communications to @var{base}. Supported values of @var{base} are:
14155 @code{ascii}, @code{octal}, and @code{hex}. The default is
14158 @item show remotelogbase
14159 Show the current setting of the radix for logging remote serial
14162 @item set remotelogfile @var{file}
14163 @cindex record serial communications on file
14164 Record remote serial communications on the named @var{file}. The
14165 default is not to record at all.
14167 @item show remotelogfile.
14168 Show the current setting of the file name on which to record the
14169 serial communications.
14171 @item set remotetimeout @var{num}
14172 @cindex timeout for serial communications
14173 @cindex remote timeout
14174 Set the timeout limit to wait for the remote target to respond to
14175 @var{num} seconds. The default is 2 seconds.
14177 @item show remotetimeout
14178 Show the current number of seconds to wait for the remote target
14181 @cindex limit hardware breakpoints and watchpoints
14182 @cindex remote target, limit break- and watchpoints
14183 @anchor{set remote hardware-watchpoint-limit}
14184 @anchor{set remote hardware-breakpoint-limit}
14185 @item set remote hardware-watchpoint-limit @var{limit}
14186 @itemx set remote hardware-breakpoint-limit @var{limit}
14187 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14188 watchpoints. A limit of -1, the default, is treated as unlimited.
14190 @item set remote exec-file @var{filename}
14191 @itemx show remote exec-file
14192 @anchor{set remote exec-file}
14193 @cindex executable file, for remote target
14194 Select the file used for @code{run} with @code{target
14195 extended-remote}. This should be set to a filename valid on the
14196 target system. If it is not set, the target will use a default
14197 filename (e.g.@: the last program run).
14200 @cindex remote packets, enabling and disabling
14201 The @value{GDBN} remote protocol autodetects the packets supported by
14202 your debugging stub. If you need to override the autodetection, you
14203 can use these commands to enable or disable individual packets. Each
14204 packet can be set to @samp{on} (the remote target supports this
14205 packet), @samp{off} (the remote target does not support this packet),
14206 or @samp{auto} (detect remote target support for this packet). They
14207 all default to @samp{auto}. For more information about each packet,
14208 see @ref{Remote Protocol}.
14210 During normal use, you should not have to use any of these commands.
14211 If you do, that may be a bug in your remote debugging stub, or a bug
14212 in @value{GDBN}. You may want to report the problem to the
14213 @value{GDBN} developers.
14215 For each packet @var{name}, the command to enable or disable the
14216 packet is @code{set remote @var{name}-packet}. The available settings
14219 @multitable @columnfractions 0.28 0.32 0.25
14222 @tab Related Features
14224 @item @code{fetch-register}
14226 @tab @code{info registers}
14228 @item @code{set-register}
14232 @item @code{binary-download}
14234 @tab @code{load}, @code{set}
14236 @item @code{read-aux-vector}
14237 @tab @code{qXfer:auxv:read}
14238 @tab @code{info auxv}
14240 @item @code{symbol-lookup}
14241 @tab @code{qSymbol}
14242 @tab Detecting multiple threads
14244 @item @code{attach}
14245 @tab @code{vAttach}
14248 @item @code{verbose-resume}
14250 @tab Stepping or resuming multiple threads
14256 @item @code{software-breakpoint}
14260 @item @code{hardware-breakpoint}
14264 @item @code{write-watchpoint}
14268 @item @code{read-watchpoint}
14272 @item @code{access-watchpoint}
14276 @item @code{target-features}
14277 @tab @code{qXfer:features:read}
14278 @tab @code{set architecture}
14280 @item @code{library-info}
14281 @tab @code{qXfer:libraries:read}
14282 @tab @code{info sharedlibrary}
14284 @item @code{memory-map}
14285 @tab @code{qXfer:memory-map:read}
14286 @tab @code{info mem}
14288 @item @code{read-spu-object}
14289 @tab @code{qXfer:spu:read}
14290 @tab @code{info spu}
14292 @item @code{write-spu-object}
14293 @tab @code{qXfer:spu:write}
14294 @tab @code{info spu}
14296 @item @code{get-thread-local-@*storage-address}
14297 @tab @code{qGetTLSAddr}
14298 @tab Displaying @code{__thread} variables
14300 @item @code{search-memory}
14301 @tab @code{qSearch:memory}
14304 @item @code{supported-packets}
14305 @tab @code{qSupported}
14306 @tab Remote communications parameters
14308 @item @code{pass-signals}
14309 @tab @code{QPassSignals}
14310 @tab @code{handle @var{signal}}
14312 @item @code{hostio-close-packet}
14313 @tab @code{vFile:close}
14314 @tab @code{remote get}, @code{remote put}
14316 @item @code{hostio-open-packet}
14317 @tab @code{vFile:open}
14318 @tab @code{remote get}, @code{remote put}
14320 @item @code{hostio-pread-packet}
14321 @tab @code{vFile:pread}
14322 @tab @code{remote get}, @code{remote put}
14324 @item @code{hostio-pwrite-packet}
14325 @tab @code{vFile:pwrite}
14326 @tab @code{remote get}, @code{remote put}
14328 @item @code{hostio-unlink-packet}
14329 @tab @code{vFile:unlink}
14330 @tab @code{remote delete}
14332 @item @code{noack-packet}
14333 @tab @code{QStartNoAckMode}
14334 @tab Packet acknowledgment
14338 @section Implementing a Remote Stub
14340 @cindex debugging stub, example
14341 @cindex remote stub, example
14342 @cindex stub example, remote debugging
14343 The stub files provided with @value{GDBN} implement the target side of the
14344 communication protocol, and the @value{GDBN} side is implemented in the
14345 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14346 these subroutines to communicate, and ignore the details. (If you're
14347 implementing your own stub file, you can still ignore the details: start
14348 with one of the existing stub files. @file{sparc-stub.c} is the best
14349 organized, and therefore the easiest to read.)
14351 @cindex remote serial debugging, overview
14352 To debug a program running on another machine (the debugging
14353 @dfn{target} machine), you must first arrange for all the usual
14354 prerequisites for the program to run by itself. For example, for a C
14359 A startup routine to set up the C runtime environment; these usually
14360 have a name like @file{crt0}. The startup routine may be supplied by
14361 your hardware supplier, or you may have to write your own.
14364 A C subroutine library to support your program's
14365 subroutine calls, notably managing input and output.
14368 A way of getting your program to the other machine---for example, a
14369 download program. These are often supplied by the hardware
14370 manufacturer, but you may have to write your own from hardware
14374 The next step is to arrange for your program to use a serial port to
14375 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14376 machine). In general terms, the scheme looks like this:
14380 @value{GDBN} already understands how to use this protocol; when everything
14381 else is set up, you can simply use the @samp{target remote} command
14382 (@pxref{Targets,,Specifying a Debugging Target}).
14384 @item On the target,
14385 you must link with your program a few special-purpose subroutines that
14386 implement the @value{GDBN} remote serial protocol. The file containing these
14387 subroutines is called a @dfn{debugging stub}.
14389 On certain remote targets, you can use an auxiliary program
14390 @code{gdbserver} instead of linking a stub into your program.
14391 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14394 The debugging stub is specific to the architecture of the remote
14395 machine; for example, use @file{sparc-stub.c} to debug programs on
14398 @cindex remote serial stub list
14399 These working remote stubs are distributed with @value{GDBN}:
14404 @cindex @file{i386-stub.c}
14407 For Intel 386 and compatible architectures.
14410 @cindex @file{m68k-stub.c}
14411 @cindex Motorola 680x0
14413 For Motorola 680x0 architectures.
14416 @cindex @file{sh-stub.c}
14419 For Renesas SH architectures.
14422 @cindex @file{sparc-stub.c}
14424 For @sc{sparc} architectures.
14426 @item sparcl-stub.c
14427 @cindex @file{sparcl-stub.c}
14430 For Fujitsu @sc{sparclite} architectures.
14434 The @file{README} file in the @value{GDBN} distribution may list other
14435 recently added stubs.
14438 * Stub Contents:: What the stub can do for you
14439 * Bootstrapping:: What you must do for the stub
14440 * Debug Session:: Putting it all together
14443 @node Stub Contents
14444 @subsection What the Stub Can Do for You
14446 @cindex remote serial stub
14447 The debugging stub for your architecture supplies these three
14451 @item set_debug_traps
14452 @findex set_debug_traps
14453 @cindex remote serial stub, initialization
14454 This routine arranges for @code{handle_exception} to run when your
14455 program stops. You must call this subroutine explicitly near the
14456 beginning of your program.
14458 @item handle_exception
14459 @findex handle_exception
14460 @cindex remote serial stub, main routine
14461 This is the central workhorse, but your program never calls it
14462 explicitly---the setup code arranges for @code{handle_exception} to
14463 run when a trap is triggered.
14465 @code{handle_exception} takes control when your program stops during
14466 execution (for example, on a breakpoint), and mediates communications
14467 with @value{GDBN} on the host machine. This is where the communications
14468 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14469 representative on the target machine. It begins by sending summary
14470 information on the state of your program, then continues to execute,
14471 retrieving and transmitting any information @value{GDBN} needs, until you
14472 execute a @value{GDBN} command that makes your program resume; at that point,
14473 @code{handle_exception} returns control to your own code on the target
14477 @cindex @code{breakpoint} subroutine, remote
14478 Use this auxiliary subroutine to make your program contain a
14479 breakpoint. Depending on the particular situation, this may be the only
14480 way for @value{GDBN} to get control. For instance, if your target
14481 machine has some sort of interrupt button, you won't need to call this;
14482 pressing the interrupt button transfers control to
14483 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14484 simply receiving characters on the serial port may also trigger a trap;
14485 again, in that situation, you don't need to call @code{breakpoint} from
14486 your own program---simply running @samp{target remote} from the host
14487 @value{GDBN} session gets control.
14489 Call @code{breakpoint} if none of these is true, or if you simply want
14490 to make certain your program stops at a predetermined point for the
14491 start of your debugging session.
14494 @node Bootstrapping
14495 @subsection What You Must Do for the Stub
14497 @cindex remote stub, support routines
14498 The debugging stubs that come with @value{GDBN} are set up for a particular
14499 chip architecture, but they have no information about the rest of your
14500 debugging target machine.
14502 First of all you need to tell the stub how to communicate with the
14506 @item int getDebugChar()
14507 @findex getDebugChar
14508 Write this subroutine to read a single character from the serial port.
14509 It may be identical to @code{getchar} for your target system; a
14510 different name is used to allow you to distinguish the two if you wish.
14512 @item void putDebugChar(int)
14513 @findex putDebugChar
14514 Write this subroutine to write a single character to the serial port.
14515 It may be identical to @code{putchar} for your target system; a
14516 different name is used to allow you to distinguish the two if you wish.
14519 @cindex control C, and remote debugging
14520 @cindex interrupting remote targets
14521 If you want @value{GDBN} to be able to stop your program while it is
14522 running, you need to use an interrupt-driven serial driver, and arrange
14523 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14524 character). That is the character which @value{GDBN} uses to tell the
14525 remote system to stop.
14527 Getting the debugging target to return the proper status to @value{GDBN}
14528 probably requires changes to the standard stub; one quick and dirty way
14529 is to just execute a breakpoint instruction (the ``dirty'' part is that
14530 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14532 Other routines you need to supply are:
14535 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14536 @findex exceptionHandler
14537 Write this function to install @var{exception_address} in the exception
14538 handling tables. You need to do this because the stub does not have any
14539 way of knowing what the exception handling tables on your target system
14540 are like (for example, the processor's table might be in @sc{rom},
14541 containing entries which point to a table in @sc{ram}).
14542 @var{exception_number} is the exception number which should be changed;
14543 its meaning is architecture-dependent (for example, different numbers
14544 might represent divide by zero, misaligned access, etc). When this
14545 exception occurs, control should be transferred directly to
14546 @var{exception_address}, and the processor state (stack, registers,
14547 and so on) should be just as it is when a processor exception occurs. So if
14548 you want to use a jump instruction to reach @var{exception_address}, it
14549 should be a simple jump, not a jump to subroutine.
14551 For the 386, @var{exception_address} should be installed as an interrupt
14552 gate so that interrupts are masked while the handler runs. The gate
14553 should be at privilege level 0 (the most privileged level). The
14554 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14555 help from @code{exceptionHandler}.
14557 @item void flush_i_cache()
14558 @findex flush_i_cache
14559 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14560 instruction cache, if any, on your target machine. If there is no
14561 instruction cache, this subroutine may be a no-op.
14563 On target machines that have instruction caches, @value{GDBN} requires this
14564 function to make certain that the state of your program is stable.
14568 You must also make sure this library routine is available:
14571 @item void *memset(void *, int, int)
14573 This is the standard library function @code{memset} that sets an area of
14574 memory to a known value. If you have one of the free versions of
14575 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14576 either obtain it from your hardware manufacturer, or write your own.
14579 If you do not use the GNU C compiler, you may need other standard
14580 library subroutines as well; this varies from one stub to another,
14581 but in general the stubs are likely to use any of the common library
14582 subroutines which @code{@value{NGCC}} generates as inline code.
14585 @node Debug Session
14586 @subsection Putting it All Together
14588 @cindex remote serial debugging summary
14589 In summary, when your program is ready to debug, you must follow these
14594 Make sure you have defined the supporting low-level routines
14595 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14597 @code{getDebugChar}, @code{putDebugChar},
14598 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14602 Insert these lines near the top of your program:
14610 For the 680x0 stub only, you need to provide a variable called
14611 @code{exceptionHook}. Normally you just use:
14614 void (*exceptionHook)() = 0;
14618 but if before calling @code{set_debug_traps}, you set it to point to a
14619 function in your program, that function is called when
14620 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14621 error). The function indicated by @code{exceptionHook} is called with
14622 one parameter: an @code{int} which is the exception number.
14625 Compile and link together: your program, the @value{GDBN} debugging stub for
14626 your target architecture, and the supporting subroutines.
14629 Make sure you have a serial connection between your target machine and
14630 the @value{GDBN} host, and identify the serial port on the host.
14633 @c The "remote" target now provides a `load' command, so we should
14634 @c document that. FIXME.
14635 Download your program to your target machine (or get it there by
14636 whatever means the manufacturer provides), and start it.
14639 Start @value{GDBN} on the host, and connect to the target
14640 (@pxref{Connecting,,Connecting to a Remote Target}).
14644 @node Configurations
14645 @chapter Configuration-Specific Information
14647 While nearly all @value{GDBN} commands are available for all native and
14648 cross versions of the debugger, there are some exceptions. This chapter
14649 describes things that are only available in certain configurations.
14651 There are three major categories of configurations: native
14652 configurations, where the host and target are the same, embedded
14653 operating system configurations, which are usually the same for several
14654 different processor architectures, and bare embedded processors, which
14655 are quite different from each other.
14660 * Embedded Processors::
14667 This section describes details specific to particular native
14672 * BSD libkvm Interface:: Debugging BSD kernel memory images
14673 * SVR4 Process Information:: SVR4 process information
14674 * DJGPP Native:: Features specific to the DJGPP port
14675 * Cygwin Native:: Features specific to the Cygwin port
14676 * Hurd Native:: Features specific to @sc{gnu} Hurd
14677 * Neutrino:: Features specific to QNX Neutrino
14683 On HP-UX systems, if you refer to a function or variable name that
14684 begins with a dollar sign, @value{GDBN} searches for a user or system
14685 name first, before it searches for a convenience variable.
14688 @node BSD libkvm Interface
14689 @subsection BSD libkvm Interface
14692 @cindex kernel memory image
14693 @cindex kernel crash dump
14695 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14696 interface that provides a uniform interface for accessing kernel virtual
14697 memory images, including live systems and crash dumps. @value{GDBN}
14698 uses this interface to allow you to debug live kernels and kernel crash
14699 dumps on many native BSD configurations. This is implemented as a
14700 special @code{kvm} debugging target. For debugging a live system, load
14701 the currently running kernel into @value{GDBN} and connect to the
14705 (@value{GDBP}) @b{target kvm}
14708 For debugging crash dumps, provide the file name of the crash dump as an
14712 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14715 Once connected to the @code{kvm} target, the following commands are
14721 Set current context from the @dfn{Process Control Block} (PCB) address.
14724 Set current context from proc address. This command isn't available on
14725 modern FreeBSD systems.
14728 @node SVR4 Process Information
14729 @subsection SVR4 Process Information
14731 @cindex examine process image
14732 @cindex process info via @file{/proc}
14734 Many versions of SVR4 and compatible systems provide a facility called
14735 @samp{/proc} that can be used to examine the image of a running
14736 process using file-system subroutines. If @value{GDBN} is configured
14737 for an operating system with this facility, the command @code{info
14738 proc} is available to report information about the process running
14739 your program, or about any process running on your system. @code{info
14740 proc} works only on SVR4 systems that include the @code{procfs} code.
14741 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14742 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14748 @itemx info proc @var{process-id}
14749 Summarize available information about any running process. If a
14750 process ID is specified by @var{process-id}, display information about
14751 that process; otherwise display information about the program being
14752 debugged. The summary includes the debugged process ID, the command
14753 line used to invoke it, its current working directory, and its
14754 executable file's absolute file name.
14756 On some systems, @var{process-id} can be of the form
14757 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14758 within a process. If the optional @var{pid} part is missing, it means
14759 a thread from the process being debugged (the leading @samp{/} still
14760 needs to be present, or else @value{GDBN} will interpret the number as
14761 a process ID rather than a thread ID).
14763 @item info proc mappings
14764 @cindex memory address space mappings
14765 Report the memory address space ranges accessible in the program, with
14766 information on whether the process has read, write, or execute access
14767 rights to each range. On @sc{gnu}/Linux systems, each memory range
14768 includes the object file which is mapped to that range, instead of the
14769 memory access rights to that range.
14771 @item info proc stat
14772 @itemx info proc status
14773 @cindex process detailed status information
14774 These subcommands are specific to @sc{gnu}/Linux systems. They show
14775 the process-related information, including the user ID and group ID;
14776 how many threads are there in the process; its virtual memory usage;
14777 the signals that are pending, blocked, and ignored; its TTY; its
14778 consumption of system and user time; its stack size; its @samp{nice}
14779 value; etc. For more information, see the @samp{proc} man page
14780 (type @kbd{man 5 proc} from your shell prompt).
14782 @item info proc all
14783 Show all the information about the process described under all of the
14784 above @code{info proc} subcommands.
14787 @comment These sub-options of 'info proc' were not included when
14788 @comment procfs.c was re-written. Keep their descriptions around
14789 @comment against the day when someone finds the time to put them back in.
14790 @kindex info proc times
14791 @item info proc times
14792 Starting time, user CPU time, and system CPU time for your program and
14795 @kindex info proc id
14797 Report on the process IDs related to your program: its own process ID,
14798 the ID of its parent, the process group ID, and the session ID.
14801 @item set procfs-trace
14802 @kindex set procfs-trace
14803 @cindex @code{procfs} API calls
14804 This command enables and disables tracing of @code{procfs} API calls.
14806 @item show procfs-trace
14807 @kindex show procfs-trace
14808 Show the current state of @code{procfs} API call tracing.
14810 @item set procfs-file @var{file}
14811 @kindex set procfs-file
14812 Tell @value{GDBN} to write @code{procfs} API trace to the named
14813 @var{file}. @value{GDBN} appends the trace info to the previous
14814 contents of the file. The default is to display the trace on the
14817 @item show procfs-file
14818 @kindex show procfs-file
14819 Show the file to which @code{procfs} API trace is written.
14821 @item proc-trace-entry
14822 @itemx proc-trace-exit
14823 @itemx proc-untrace-entry
14824 @itemx proc-untrace-exit
14825 @kindex proc-trace-entry
14826 @kindex proc-trace-exit
14827 @kindex proc-untrace-entry
14828 @kindex proc-untrace-exit
14829 These commands enable and disable tracing of entries into and exits
14830 from the @code{syscall} interface.
14833 @kindex info pidlist
14834 @cindex process list, QNX Neutrino
14835 For QNX Neutrino only, this command displays the list of all the
14836 processes and all the threads within each process.
14839 @kindex info meminfo
14840 @cindex mapinfo list, QNX Neutrino
14841 For QNX Neutrino only, this command displays the list of all mapinfos.
14845 @subsection Features for Debugging @sc{djgpp} Programs
14846 @cindex @sc{djgpp} debugging
14847 @cindex native @sc{djgpp} debugging
14848 @cindex MS-DOS-specific commands
14851 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14852 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14853 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14854 top of real-mode DOS systems and their emulations.
14856 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14857 defines a few commands specific to the @sc{djgpp} port. This
14858 subsection describes those commands.
14863 This is a prefix of @sc{djgpp}-specific commands which print
14864 information about the target system and important OS structures.
14867 @cindex MS-DOS system info
14868 @cindex free memory information (MS-DOS)
14869 @item info dos sysinfo
14870 This command displays assorted information about the underlying
14871 platform: the CPU type and features, the OS version and flavor, the
14872 DPMI version, and the available conventional and DPMI memory.
14877 @cindex segment descriptor tables
14878 @cindex descriptor tables display
14880 @itemx info dos ldt
14881 @itemx info dos idt
14882 These 3 commands display entries from, respectively, Global, Local,
14883 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14884 tables are data structures which store a descriptor for each segment
14885 that is currently in use. The segment's selector is an index into a
14886 descriptor table; the table entry for that index holds the
14887 descriptor's base address and limit, and its attributes and access
14890 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14891 segment (used for both data and the stack), and a DOS segment (which
14892 allows access to DOS/BIOS data structures and absolute addresses in
14893 conventional memory). However, the DPMI host will usually define
14894 additional segments in order to support the DPMI environment.
14896 @cindex garbled pointers
14897 These commands allow to display entries from the descriptor tables.
14898 Without an argument, all entries from the specified table are
14899 displayed. An argument, which should be an integer expression, means
14900 display a single entry whose index is given by the argument. For
14901 example, here's a convenient way to display information about the
14902 debugged program's data segment:
14905 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14906 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14910 This comes in handy when you want to see whether a pointer is outside
14911 the data segment's limit (i.e.@: @dfn{garbled}).
14913 @cindex page tables display (MS-DOS)
14915 @itemx info dos pte
14916 These two commands display entries from, respectively, the Page
14917 Directory and the Page Tables. Page Directories and Page Tables are
14918 data structures which control how virtual memory addresses are mapped
14919 into physical addresses. A Page Table includes an entry for every
14920 page of memory that is mapped into the program's address space; there
14921 may be several Page Tables, each one holding up to 4096 entries. A
14922 Page Directory has up to 4096 entries, one each for every Page Table
14923 that is currently in use.
14925 Without an argument, @kbd{info dos pde} displays the entire Page
14926 Directory, and @kbd{info dos pte} displays all the entries in all of
14927 the Page Tables. An argument, an integer expression, given to the
14928 @kbd{info dos pde} command means display only that entry from the Page
14929 Directory table. An argument given to the @kbd{info dos pte} command
14930 means display entries from a single Page Table, the one pointed to by
14931 the specified entry in the Page Directory.
14933 @cindex direct memory access (DMA) on MS-DOS
14934 These commands are useful when your program uses @dfn{DMA} (Direct
14935 Memory Access), which needs physical addresses to program the DMA
14938 These commands are supported only with some DPMI servers.
14940 @cindex physical address from linear address
14941 @item info dos address-pte @var{addr}
14942 This command displays the Page Table entry for a specified linear
14943 address. The argument @var{addr} is a linear address which should
14944 already have the appropriate segment's base address added to it,
14945 because this command accepts addresses which may belong to @emph{any}
14946 segment. For example, here's how to display the Page Table entry for
14947 the page where a variable @code{i} is stored:
14950 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14951 @exdent @code{Page Table entry for address 0x11a00d30:}
14952 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14956 This says that @code{i} is stored at offset @code{0xd30} from the page
14957 whose physical base address is @code{0x02698000}, and shows all the
14958 attributes of that page.
14960 Note that you must cast the addresses of variables to a @code{char *},
14961 since otherwise the value of @code{__djgpp_base_address}, the base
14962 address of all variables and functions in a @sc{djgpp} program, will
14963 be added using the rules of C pointer arithmetics: if @code{i} is
14964 declared an @code{int}, @value{GDBN} will add 4 times the value of
14965 @code{__djgpp_base_address} to the address of @code{i}.
14967 Here's another example, it displays the Page Table entry for the
14971 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14972 @exdent @code{Page Table entry for address 0x29110:}
14973 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14977 (The @code{+ 3} offset is because the transfer buffer's address is the
14978 3rd member of the @code{_go32_info_block} structure.) The output
14979 clearly shows that this DPMI server maps the addresses in conventional
14980 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14981 linear (@code{0x29110}) addresses are identical.
14983 This command is supported only with some DPMI servers.
14986 @cindex DOS serial data link, remote debugging
14987 In addition to native debugging, the DJGPP port supports remote
14988 debugging via a serial data link. The following commands are specific
14989 to remote serial debugging in the DJGPP port of @value{GDBN}.
14992 @kindex set com1base
14993 @kindex set com1irq
14994 @kindex set com2base
14995 @kindex set com2irq
14996 @kindex set com3base
14997 @kindex set com3irq
14998 @kindex set com4base
14999 @kindex set com4irq
15000 @item set com1base @var{addr}
15001 This command sets the base I/O port address of the @file{COM1} serial
15004 @item set com1irq @var{irq}
15005 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15006 for the @file{COM1} serial port.
15008 There are similar commands @samp{set com2base}, @samp{set com3irq},
15009 etc.@: for setting the port address and the @code{IRQ} lines for the
15012 @kindex show com1base
15013 @kindex show com1irq
15014 @kindex show com2base
15015 @kindex show com2irq
15016 @kindex show com3base
15017 @kindex show com3irq
15018 @kindex show com4base
15019 @kindex show com4irq
15020 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15021 display the current settings of the base address and the @code{IRQ}
15022 lines used by the COM ports.
15025 @kindex info serial
15026 @cindex DOS serial port status
15027 This command prints the status of the 4 DOS serial ports. For each
15028 port, it prints whether it's active or not, its I/O base address and
15029 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15030 counts of various errors encountered so far.
15034 @node Cygwin Native
15035 @subsection Features for Debugging MS Windows PE Executables
15036 @cindex MS Windows debugging
15037 @cindex native Cygwin debugging
15038 @cindex Cygwin-specific commands
15040 @value{GDBN} supports native debugging of MS Windows programs, including
15041 DLLs with and without symbolic debugging information. There are various
15042 additional Cygwin-specific commands, described in this section.
15043 Working with DLLs that have no debugging symbols is described in
15044 @ref{Non-debug DLL Symbols}.
15049 This is a prefix of MS Windows-specific commands which print
15050 information about the target system and important OS structures.
15052 @item info w32 selector
15053 This command displays information returned by
15054 the Win32 API @code{GetThreadSelectorEntry} function.
15055 It takes an optional argument that is evaluated to
15056 a long value to give the information about this given selector.
15057 Without argument, this command displays information
15058 about the six segment registers.
15062 This is a Cygwin-specific alias of @code{info shared}.
15064 @kindex dll-symbols
15066 This command loads symbols from a dll similarly to
15067 add-sym command but without the need to specify a base address.
15069 @kindex set cygwin-exceptions
15070 @cindex debugging the Cygwin DLL
15071 @cindex Cygwin DLL, debugging
15072 @item set cygwin-exceptions @var{mode}
15073 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15074 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15075 @value{GDBN} will delay recognition of exceptions, and may ignore some
15076 exceptions which seem to be caused by internal Cygwin DLL
15077 ``bookkeeping''. This option is meant primarily for debugging the
15078 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15079 @value{GDBN} users with false @code{SIGSEGV} signals.
15081 @kindex show cygwin-exceptions
15082 @item show cygwin-exceptions
15083 Displays whether @value{GDBN} will break on exceptions that happen
15084 inside the Cygwin DLL itself.
15086 @kindex set new-console
15087 @item set new-console @var{mode}
15088 If @var{mode} is @code{on} the debuggee will
15089 be started in a new console on next start.
15090 If @var{mode} is @code{off}i, the debuggee will
15091 be started in the same console as the debugger.
15093 @kindex show new-console
15094 @item show new-console
15095 Displays whether a new console is used
15096 when the debuggee is started.
15098 @kindex set new-group
15099 @item set new-group @var{mode}
15100 This boolean value controls whether the debuggee should
15101 start a new group or stay in the same group as the debugger.
15102 This affects the way the Windows OS handles
15105 @kindex show new-group
15106 @item show new-group
15107 Displays current value of new-group boolean.
15109 @kindex set debugevents
15110 @item set debugevents
15111 This boolean value adds debug output concerning kernel events related
15112 to the debuggee seen by the debugger. This includes events that
15113 signal thread and process creation and exit, DLL loading and
15114 unloading, console interrupts, and debugging messages produced by the
15115 Windows @code{OutputDebugString} API call.
15117 @kindex set debugexec
15118 @item set debugexec
15119 This boolean value adds debug output concerning execute events
15120 (such as resume thread) seen by the debugger.
15122 @kindex set debugexceptions
15123 @item set debugexceptions
15124 This boolean value adds debug output concerning exceptions in the
15125 debuggee seen by the debugger.
15127 @kindex set debugmemory
15128 @item set debugmemory
15129 This boolean value adds debug output concerning debuggee memory reads
15130 and writes by the debugger.
15134 This boolean values specifies whether the debuggee is called
15135 via a shell or directly (default value is on).
15139 Displays if the debuggee will be started with a shell.
15144 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15147 @node Non-debug DLL Symbols
15148 @subsubsection Support for DLLs without Debugging Symbols
15149 @cindex DLLs with no debugging symbols
15150 @cindex Minimal symbols and DLLs
15152 Very often on windows, some of the DLLs that your program relies on do
15153 not include symbolic debugging information (for example,
15154 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15155 symbols in a DLL, it relies on the minimal amount of symbolic
15156 information contained in the DLL's export table. This section
15157 describes working with such symbols, known internally to @value{GDBN} as
15158 ``minimal symbols''.
15160 Note that before the debugged program has started execution, no DLLs
15161 will have been loaded. The easiest way around this problem is simply to
15162 start the program --- either by setting a breakpoint or letting the
15163 program run once to completion. It is also possible to force
15164 @value{GDBN} to load a particular DLL before starting the executable ---
15165 see the shared library information in @ref{Files}, or the
15166 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15167 explicitly loading symbols from a DLL with no debugging information will
15168 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15169 which may adversely affect symbol lookup performance.
15171 @subsubsection DLL Name Prefixes
15173 In keeping with the naming conventions used by the Microsoft debugging
15174 tools, DLL export symbols are made available with a prefix based on the
15175 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15176 also entered into the symbol table, so @code{CreateFileA} is often
15177 sufficient. In some cases there will be name clashes within a program
15178 (particularly if the executable itself includes full debugging symbols)
15179 necessitating the use of the fully qualified name when referring to the
15180 contents of the DLL. Use single-quotes around the name to avoid the
15181 exclamation mark (``!'') being interpreted as a language operator.
15183 Note that the internal name of the DLL may be all upper-case, even
15184 though the file name of the DLL is lower-case, or vice-versa. Since
15185 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15186 some confusion. If in doubt, try the @code{info functions} and
15187 @code{info variables} commands or even @code{maint print msymbols}
15188 (@pxref{Symbols}). Here's an example:
15191 (@value{GDBP}) info function CreateFileA
15192 All functions matching regular expression "CreateFileA":
15194 Non-debugging symbols:
15195 0x77e885f4 CreateFileA
15196 0x77e885f4 KERNEL32!CreateFileA
15200 (@value{GDBP}) info function !
15201 All functions matching regular expression "!":
15203 Non-debugging symbols:
15204 0x6100114c cygwin1!__assert
15205 0x61004034 cygwin1!_dll_crt0@@0
15206 0x61004240 cygwin1!dll_crt0(per_process *)
15210 @subsubsection Working with Minimal Symbols
15212 Symbols extracted from a DLL's export table do not contain very much
15213 type information. All that @value{GDBN} can do is guess whether a symbol
15214 refers to a function or variable depending on the linker section that
15215 contains the symbol. Also note that the actual contents of the memory
15216 contained in a DLL are not available unless the program is running. This
15217 means that you cannot examine the contents of a variable or disassemble
15218 a function within a DLL without a running program.
15220 Variables are generally treated as pointers and dereferenced
15221 automatically. For this reason, it is often necessary to prefix a
15222 variable name with the address-of operator (``&'') and provide explicit
15223 type information in the command. Here's an example of the type of
15227 (@value{GDBP}) print 'cygwin1!__argv'
15232 (@value{GDBP}) x 'cygwin1!__argv'
15233 0x10021610: "\230y\""
15236 And two possible solutions:
15239 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15240 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15244 (@value{GDBP}) x/2x &'cygwin1!__argv'
15245 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15246 (@value{GDBP}) x/x 0x10021608
15247 0x10021608: 0x0022fd98
15248 (@value{GDBP}) x/s 0x0022fd98
15249 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15252 Setting a break point within a DLL is possible even before the program
15253 starts execution. However, under these circumstances, @value{GDBN} can't
15254 examine the initial instructions of the function in order to skip the
15255 function's frame set-up code. You can work around this by using ``*&''
15256 to set the breakpoint at a raw memory address:
15259 (@value{GDBP}) break *&'python22!PyOS_Readline'
15260 Breakpoint 1 at 0x1e04eff0
15263 The author of these extensions is not entirely convinced that setting a
15264 break point within a shared DLL like @file{kernel32.dll} is completely
15268 @subsection Commands Specific to @sc{gnu} Hurd Systems
15269 @cindex @sc{gnu} Hurd debugging
15271 This subsection describes @value{GDBN} commands specific to the
15272 @sc{gnu} Hurd native debugging.
15277 @kindex set signals@r{, Hurd command}
15278 @kindex set sigs@r{, Hurd command}
15279 This command toggles the state of inferior signal interception by
15280 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15281 affected by this command. @code{sigs} is a shorthand alias for
15286 @kindex show signals@r{, Hurd command}
15287 @kindex show sigs@r{, Hurd command}
15288 Show the current state of intercepting inferior's signals.
15290 @item set signal-thread
15291 @itemx set sigthread
15292 @kindex set signal-thread
15293 @kindex set sigthread
15294 This command tells @value{GDBN} which thread is the @code{libc} signal
15295 thread. That thread is run when a signal is delivered to a running
15296 process. @code{set sigthread} is the shorthand alias of @code{set
15299 @item show signal-thread
15300 @itemx show sigthread
15301 @kindex show signal-thread
15302 @kindex show sigthread
15303 These two commands show which thread will run when the inferior is
15304 delivered a signal.
15307 @kindex set stopped@r{, Hurd command}
15308 This commands tells @value{GDBN} that the inferior process is stopped,
15309 as with the @code{SIGSTOP} signal. The stopped process can be
15310 continued by delivering a signal to it.
15313 @kindex show stopped@r{, Hurd command}
15314 This command shows whether @value{GDBN} thinks the debuggee is
15317 @item set exceptions
15318 @kindex set exceptions@r{, Hurd command}
15319 Use this command to turn off trapping of exceptions in the inferior.
15320 When exception trapping is off, neither breakpoints nor
15321 single-stepping will work. To restore the default, set exception
15324 @item show exceptions
15325 @kindex show exceptions@r{, Hurd command}
15326 Show the current state of trapping exceptions in the inferior.
15328 @item set task pause
15329 @kindex set task@r{, Hurd commands}
15330 @cindex task attributes (@sc{gnu} Hurd)
15331 @cindex pause current task (@sc{gnu} Hurd)
15332 This command toggles task suspension when @value{GDBN} has control.
15333 Setting it to on takes effect immediately, and the task is suspended
15334 whenever @value{GDBN} gets control. Setting it to off will take
15335 effect the next time the inferior is continued. If this option is set
15336 to off, you can use @code{set thread default pause on} or @code{set
15337 thread pause on} (see below) to pause individual threads.
15339 @item show task pause
15340 @kindex show task@r{, Hurd commands}
15341 Show the current state of task suspension.
15343 @item set task detach-suspend-count
15344 @cindex task suspend count
15345 @cindex detach from task, @sc{gnu} Hurd
15346 This command sets the suspend count the task will be left with when
15347 @value{GDBN} detaches from it.
15349 @item show task detach-suspend-count
15350 Show the suspend count the task will be left with when detaching.
15352 @item set task exception-port
15353 @itemx set task excp
15354 @cindex task exception port, @sc{gnu} Hurd
15355 This command sets the task exception port to which @value{GDBN} will
15356 forward exceptions. The argument should be the value of the @dfn{send
15357 rights} of the task. @code{set task excp} is a shorthand alias.
15359 @item set noninvasive
15360 @cindex noninvasive task options
15361 This command switches @value{GDBN} to a mode that is the least
15362 invasive as far as interfering with the inferior is concerned. This
15363 is the same as using @code{set task pause}, @code{set exceptions}, and
15364 @code{set signals} to values opposite to the defaults.
15366 @item info send-rights
15367 @itemx info receive-rights
15368 @itemx info port-rights
15369 @itemx info port-sets
15370 @itemx info dead-names
15373 @cindex send rights, @sc{gnu} Hurd
15374 @cindex receive rights, @sc{gnu} Hurd
15375 @cindex port rights, @sc{gnu} Hurd
15376 @cindex port sets, @sc{gnu} Hurd
15377 @cindex dead names, @sc{gnu} Hurd
15378 These commands display information about, respectively, send rights,
15379 receive rights, port rights, port sets, and dead names of a task.
15380 There are also shorthand aliases: @code{info ports} for @code{info
15381 port-rights} and @code{info psets} for @code{info port-sets}.
15383 @item set thread pause
15384 @kindex set thread@r{, Hurd command}
15385 @cindex thread properties, @sc{gnu} Hurd
15386 @cindex pause current thread (@sc{gnu} Hurd)
15387 This command toggles current thread suspension when @value{GDBN} has
15388 control. Setting it to on takes effect immediately, and the current
15389 thread is suspended whenever @value{GDBN} gets control. Setting it to
15390 off will take effect the next time the inferior is continued.
15391 Normally, this command has no effect, since when @value{GDBN} has
15392 control, the whole task is suspended. However, if you used @code{set
15393 task pause off} (see above), this command comes in handy to suspend
15394 only the current thread.
15396 @item show thread pause
15397 @kindex show thread@r{, Hurd command}
15398 This command shows the state of current thread suspension.
15400 @item set thread run
15401 This command sets whether the current thread is allowed to run.
15403 @item show thread run
15404 Show whether the current thread is allowed to run.
15406 @item set thread detach-suspend-count
15407 @cindex thread suspend count, @sc{gnu} Hurd
15408 @cindex detach from thread, @sc{gnu} Hurd
15409 This command sets the suspend count @value{GDBN} will leave on a
15410 thread when detaching. This number is relative to the suspend count
15411 found by @value{GDBN} when it notices the thread; use @code{set thread
15412 takeover-suspend-count} to force it to an absolute value.
15414 @item show thread detach-suspend-count
15415 Show the suspend count @value{GDBN} will leave on the thread when
15418 @item set thread exception-port
15419 @itemx set thread excp
15420 Set the thread exception port to which to forward exceptions. This
15421 overrides the port set by @code{set task exception-port} (see above).
15422 @code{set thread excp} is the shorthand alias.
15424 @item set thread takeover-suspend-count
15425 Normally, @value{GDBN}'s thread suspend counts are relative to the
15426 value @value{GDBN} finds when it notices each thread. This command
15427 changes the suspend counts to be absolute instead.
15429 @item set thread default
15430 @itemx show thread default
15431 @cindex thread default settings, @sc{gnu} Hurd
15432 Each of the above @code{set thread} commands has a @code{set thread
15433 default} counterpart (e.g., @code{set thread default pause}, @code{set
15434 thread default exception-port}, etc.). The @code{thread default}
15435 variety of commands sets the default thread properties for all
15436 threads; you can then change the properties of individual threads with
15437 the non-default commands.
15442 @subsection QNX Neutrino
15443 @cindex QNX Neutrino
15445 @value{GDBN} provides the following commands specific to the QNX
15449 @item set debug nto-debug
15450 @kindex set debug nto-debug
15451 When set to on, enables debugging messages specific to the QNX
15454 @item show debug nto-debug
15455 @kindex show debug nto-debug
15456 Show the current state of QNX Neutrino messages.
15461 @section Embedded Operating Systems
15463 This section describes configurations involving the debugging of
15464 embedded operating systems that are available for several different
15468 * VxWorks:: Using @value{GDBN} with VxWorks
15471 @value{GDBN} includes the ability to debug programs running on
15472 various real-time operating systems.
15475 @subsection Using @value{GDBN} with VxWorks
15481 @kindex target vxworks
15482 @item target vxworks @var{machinename}
15483 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15484 is the target system's machine name or IP address.
15488 On VxWorks, @code{load} links @var{filename} dynamically on the
15489 current target system as well as adding its symbols in @value{GDBN}.
15491 @value{GDBN} enables developers to spawn and debug tasks running on networked
15492 VxWorks targets from a Unix host. Already-running tasks spawned from
15493 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15494 both the Unix host and on the VxWorks target. The program
15495 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15496 installed with the name @code{vxgdb}, to distinguish it from a
15497 @value{GDBN} for debugging programs on the host itself.)
15500 @item VxWorks-timeout @var{args}
15501 @kindex vxworks-timeout
15502 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15503 This option is set by the user, and @var{args} represents the number of
15504 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15505 your VxWorks target is a slow software simulator or is on the far side
15506 of a thin network line.
15509 The following information on connecting to VxWorks was current when
15510 this manual was produced; newer releases of VxWorks may use revised
15513 @findex INCLUDE_RDB
15514 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15515 to include the remote debugging interface routines in the VxWorks
15516 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15517 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15518 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15519 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15520 information on configuring and remaking VxWorks, see the manufacturer's
15522 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15524 Once you have included @file{rdb.a} in your VxWorks system image and set
15525 your Unix execution search path to find @value{GDBN}, you are ready to
15526 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15527 @code{vxgdb}, depending on your installation).
15529 @value{GDBN} comes up showing the prompt:
15536 * VxWorks Connection:: Connecting to VxWorks
15537 * VxWorks Download:: VxWorks download
15538 * VxWorks Attach:: Running tasks
15541 @node VxWorks Connection
15542 @subsubsection Connecting to VxWorks
15544 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15545 network. To connect to a target whose host name is ``@code{tt}'', type:
15548 (vxgdb) target vxworks tt
15552 @value{GDBN} displays messages like these:
15555 Attaching remote machine across net...
15560 @value{GDBN} then attempts to read the symbol tables of any object modules
15561 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15562 these files by searching the directories listed in the command search
15563 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15564 to find an object file, it displays a message such as:
15567 prog.o: No such file or directory.
15570 When this happens, add the appropriate directory to the search path with
15571 the @value{GDBN} command @code{path}, and execute the @code{target}
15574 @node VxWorks Download
15575 @subsubsection VxWorks Download
15577 @cindex download to VxWorks
15578 If you have connected to the VxWorks target and you want to debug an
15579 object that has not yet been loaded, you can use the @value{GDBN}
15580 @code{load} command to download a file from Unix to VxWorks
15581 incrementally. The object file given as an argument to the @code{load}
15582 command is actually opened twice: first by the VxWorks target in order
15583 to download the code, then by @value{GDBN} in order to read the symbol
15584 table. This can lead to problems if the current working directories on
15585 the two systems differ. If both systems have NFS mounted the same
15586 filesystems, you can avoid these problems by using absolute paths.
15587 Otherwise, it is simplest to set the working directory on both systems
15588 to the directory in which the object file resides, and then to reference
15589 the file by its name, without any path. For instance, a program
15590 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15591 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15592 program, type this on VxWorks:
15595 -> cd "@var{vxpath}/vw/demo/rdb"
15599 Then, in @value{GDBN}, type:
15602 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15603 (vxgdb) load prog.o
15606 @value{GDBN} displays a response similar to this:
15609 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15612 You can also use the @code{load} command to reload an object module
15613 after editing and recompiling the corresponding source file. Note that
15614 this makes @value{GDBN} delete all currently-defined breakpoints,
15615 auto-displays, and convenience variables, and to clear the value
15616 history. (This is necessary in order to preserve the integrity of
15617 debugger's data structures that reference the target system's symbol
15620 @node VxWorks Attach
15621 @subsubsection Running Tasks
15623 @cindex running VxWorks tasks
15624 You can also attach to an existing task using the @code{attach} command as
15628 (vxgdb) attach @var{task}
15632 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15633 or suspended when you attach to it. Running tasks are suspended at
15634 the time of attachment.
15636 @node Embedded Processors
15637 @section Embedded Processors
15639 This section goes into details specific to particular embedded
15642 @cindex send command to simulator
15643 Whenever a specific embedded processor has a simulator, @value{GDBN}
15644 allows to send an arbitrary command to the simulator.
15647 @item sim @var{command}
15648 @kindex sim@r{, a command}
15649 Send an arbitrary @var{command} string to the simulator. Consult the
15650 documentation for the specific simulator in use for information about
15651 acceptable commands.
15657 * M32R/D:: Renesas M32R/D
15658 * M68K:: Motorola M68K
15659 * MIPS Embedded:: MIPS Embedded
15660 * OpenRISC 1000:: OpenRisc 1000
15661 * PA:: HP PA Embedded
15662 * PowerPC Embedded:: PowerPC Embedded
15663 * Sparclet:: Tsqware Sparclet
15664 * Sparclite:: Fujitsu Sparclite
15665 * Z8000:: Zilog Z8000
15668 * Super-H:: Renesas Super-H
15677 @item target rdi @var{dev}
15678 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15679 use this target to communicate with both boards running the Angel
15680 monitor, or with the EmbeddedICE JTAG debug device.
15683 @item target rdp @var{dev}
15688 @value{GDBN} provides the following ARM-specific commands:
15691 @item set arm disassembler
15693 This commands selects from a list of disassembly styles. The
15694 @code{"std"} style is the standard style.
15696 @item show arm disassembler
15698 Show the current disassembly style.
15700 @item set arm apcs32
15701 @cindex ARM 32-bit mode
15702 This command toggles ARM operation mode between 32-bit and 26-bit.
15704 @item show arm apcs32
15705 Display the current usage of the ARM 32-bit mode.
15707 @item set arm fpu @var{fputype}
15708 This command sets the ARM floating-point unit (FPU) type. The
15709 argument @var{fputype} can be one of these:
15713 Determine the FPU type by querying the OS ABI.
15715 Software FPU, with mixed-endian doubles on little-endian ARM
15718 GCC-compiled FPA co-processor.
15720 Software FPU with pure-endian doubles.
15726 Show the current type of the FPU.
15729 This command forces @value{GDBN} to use the specified ABI.
15732 Show the currently used ABI.
15734 @item set arm fallback-mode (arm|thumb|auto)
15735 @value{GDBN} uses the symbol table, when available, to determine
15736 whether instructions are ARM or Thumb. This command controls
15737 @value{GDBN}'s default behavior when the symbol table is not
15738 available. The default is @samp{auto}, which causes @value{GDBN} to
15739 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15742 @item show arm fallback-mode
15743 Show the current fallback instruction mode.
15745 @item set arm force-mode (arm|thumb|auto)
15746 This command overrides use of the symbol table to determine whether
15747 instructions are ARM or Thumb. The default is @samp{auto}, which
15748 causes @value{GDBN} to use the symbol table and then the setting
15749 of @samp{set arm fallback-mode}.
15751 @item show arm force-mode
15752 Show the current forced instruction mode.
15754 @item set debug arm
15755 Toggle whether to display ARM-specific debugging messages from the ARM
15756 target support subsystem.
15758 @item show debug arm
15759 Show whether ARM-specific debugging messages are enabled.
15762 The following commands are available when an ARM target is debugged
15763 using the RDI interface:
15766 @item rdilogfile @r{[}@var{file}@r{]}
15768 @cindex ADP (Angel Debugger Protocol) logging
15769 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15770 With an argument, sets the log file to the specified @var{file}. With
15771 no argument, show the current log file name. The default log file is
15774 @item rdilogenable @r{[}@var{arg}@r{]}
15775 @kindex rdilogenable
15776 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15777 enables logging, with an argument 0 or @code{"no"} disables it. With
15778 no arguments displays the current setting. When logging is enabled,
15779 ADP packets exchanged between @value{GDBN} and the RDI target device
15780 are logged to a file.
15782 @item set rdiromatzero
15783 @kindex set rdiromatzero
15784 @cindex ROM at zero address, RDI
15785 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15786 vector catching is disabled, so that zero address can be used. If off
15787 (the default), vector catching is enabled. For this command to take
15788 effect, it needs to be invoked prior to the @code{target rdi} command.
15790 @item show rdiromatzero
15791 @kindex show rdiromatzero
15792 Show the current setting of ROM at zero address.
15794 @item set rdiheartbeat
15795 @kindex set rdiheartbeat
15796 @cindex RDI heartbeat
15797 Enable or disable RDI heartbeat packets. It is not recommended to
15798 turn on this option, since it confuses ARM and EPI JTAG interface, as
15799 well as the Angel monitor.
15801 @item show rdiheartbeat
15802 @kindex show rdiheartbeat
15803 Show the setting of RDI heartbeat packets.
15808 @subsection Renesas M32R/D and M32R/SDI
15811 @kindex target m32r
15812 @item target m32r @var{dev}
15813 Renesas M32R/D ROM monitor.
15815 @kindex target m32rsdi
15816 @item target m32rsdi @var{dev}
15817 Renesas M32R SDI server, connected via parallel port to the board.
15820 The following @value{GDBN} commands are specific to the M32R monitor:
15823 @item set download-path @var{path}
15824 @kindex set download-path
15825 @cindex find downloadable @sc{srec} files (M32R)
15826 Set the default path for finding downloadable @sc{srec} files.
15828 @item show download-path
15829 @kindex show download-path
15830 Show the default path for downloadable @sc{srec} files.
15832 @item set board-address @var{addr}
15833 @kindex set board-address
15834 @cindex M32-EVA target board address
15835 Set the IP address for the M32R-EVA target board.
15837 @item show board-address
15838 @kindex show board-address
15839 Show the current IP address of the target board.
15841 @item set server-address @var{addr}
15842 @kindex set server-address
15843 @cindex download server address (M32R)
15844 Set the IP address for the download server, which is the @value{GDBN}'s
15847 @item show server-address
15848 @kindex show server-address
15849 Display the IP address of the download server.
15851 @item upload @r{[}@var{file}@r{]}
15852 @kindex upload@r{, M32R}
15853 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15854 upload capability. If no @var{file} argument is given, the current
15855 executable file is uploaded.
15857 @item tload @r{[}@var{file}@r{]}
15858 @kindex tload@r{, M32R}
15859 Test the @code{upload} command.
15862 The following commands are available for M32R/SDI:
15867 @cindex reset SDI connection, M32R
15868 This command resets the SDI connection.
15872 This command shows the SDI connection status.
15875 @kindex debug_chaos
15876 @cindex M32R/Chaos debugging
15877 Instructs the remote that M32R/Chaos debugging is to be used.
15879 @item use_debug_dma
15880 @kindex use_debug_dma
15881 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15884 @kindex use_mon_code
15885 Instructs the remote to use the MON_CODE method of accessing memory.
15888 @kindex use_ib_break
15889 Instructs the remote to set breakpoints by IB break.
15891 @item use_dbt_break
15892 @kindex use_dbt_break
15893 Instructs the remote to set breakpoints by DBT.
15899 The Motorola m68k configuration includes ColdFire support, and a
15900 target command for the following ROM monitor.
15904 @kindex target dbug
15905 @item target dbug @var{dev}
15906 dBUG ROM monitor for Motorola ColdFire.
15910 @node MIPS Embedded
15911 @subsection MIPS Embedded
15913 @cindex MIPS boards
15914 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15915 MIPS board attached to a serial line. This is available when
15916 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15919 Use these @value{GDBN} commands to specify the connection to your target board:
15922 @item target mips @var{port}
15923 @kindex target mips @var{port}
15924 To run a program on the board, start up @code{@value{GDBP}} with the
15925 name of your program as the argument. To connect to the board, use the
15926 command @samp{target mips @var{port}}, where @var{port} is the name of
15927 the serial port connected to the board. If the program has not already
15928 been downloaded to the board, you may use the @code{load} command to
15929 download it. You can then use all the usual @value{GDBN} commands.
15931 For example, this sequence connects to the target board through a serial
15932 port, and loads and runs a program called @var{prog} through the
15936 host$ @value{GDBP} @var{prog}
15937 @value{GDBN} is free software and @dots{}
15938 (@value{GDBP}) target mips /dev/ttyb
15939 (@value{GDBP}) load @var{prog}
15943 @item target mips @var{hostname}:@var{portnumber}
15944 On some @value{GDBN} host configurations, you can specify a TCP
15945 connection (for instance, to a serial line managed by a terminal
15946 concentrator) instead of a serial port, using the syntax
15947 @samp{@var{hostname}:@var{portnumber}}.
15949 @item target pmon @var{port}
15950 @kindex target pmon @var{port}
15953 @item target ddb @var{port}
15954 @kindex target ddb @var{port}
15955 NEC's DDB variant of PMON for Vr4300.
15957 @item target lsi @var{port}
15958 @kindex target lsi @var{port}
15959 LSI variant of PMON.
15961 @kindex target r3900
15962 @item target r3900 @var{dev}
15963 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15965 @kindex target array
15966 @item target array @var{dev}
15967 Array Tech LSI33K RAID controller board.
15973 @value{GDBN} also supports these special commands for MIPS targets:
15976 @item set mipsfpu double
15977 @itemx set mipsfpu single
15978 @itemx set mipsfpu none
15979 @itemx set mipsfpu auto
15980 @itemx show mipsfpu
15981 @kindex set mipsfpu
15982 @kindex show mipsfpu
15983 @cindex MIPS remote floating point
15984 @cindex floating point, MIPS remote
15985 If your target board does not support the MIPS floating point
15986 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15987 need this, you may wish to put the command in your @value{GDBN} init
15988 file). This tells @value{GDBN} how to find the return value of
15989 functions which return floating point values. It also allows
15990 @value{GDBN} to avoid saving the floating point registers when calling
15991 functions on the board. If you are using a floating point coprocessor
15992 with only single precision floating point support, as on the @sc{r4650}
15993 processor, use the command @samp{set mipsfpu single}. The default
15994 double precision floating point coprocessor may be selected using
15995 @samp{set mipsfpu double}.
15997 In previous versions the only choices were double precision or no
15998 floating point, so @samp{set mipsfpu on} will select double precision
15999 and @samp{set mipsfpu off} will select no floating point.
16001 As usual, you can inquire about the @code{mipsfpu} variable with
16002 @samp{show mipsfpu}.
16004 @item set timeout @var{seconds}
16005 @itemx set retransmit-timeout @var{seconds}
16006 @itemx show timeout
16007 @itemx show retransmit-timeout
16008 @cindex @code{timeout}, MIPS protocol
16009 @cindex @code{retransmit-timeout}, MIPS protocol
16010 @kindex set timeout
16011 @kindex show timeout
16012 @kindex set retransmit-timeout
16013 @kindex show retransmit-timeout
16014 You can control the timeout used while waiting for a packet, in the MIPS
16015 remote protocol, with the @code{set timeout @var{seconds}} command. The
16016 default is 5 seconds. Similarly, you can control the timeout used while
16017 waiting for an acknowledgment of a packet with the @code{set
16018 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16019 You can inspect both values with @code{show timeout} and @code{show
16020 retransmit-timeout}. (These commands are @emph{only} available when
16021 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16023 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16024 is waiting for your program to stop. In that case, @value{GDBN} waits
16025 forever because it has no way of knowing how long the program is going
16026 to run before stopping.
16028 @item set syn-garbage-limit @var{num}
16029 @kindex set syn-garbage-limit@r{, MIPS remote}
16030 @cindex synchronize with remote MIPS target
16031 Limit the maximum number of characters @value{GDBN} should ignore when
16032 it tries to synchronize with the remote target. The default is 10
16033 characters. Setting the limit to -1 means there's no limit.
16035 @item show syn-garbage-limit
16036 @kindex show syn-garbage-limit@r{, MIPS remote}
16037 Show the current limit on the number of characters to ignore when
16038 trying to synchronize with the remote system.
16040 @item set monitor-prompt @var{prompt}
16041 @kindex set monitor-prompt@r{, MIPS remote}
16042 @cindex remote monitor prompt
16043 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16044 remote monitor. The default depends on the target:
16054 @item show monitor-prompt
16055 @kindex show monitor-prompt@r{, MIPS remote}
16056 Show the current strings @value{GDBN} expects as the prompt from the
16059 @item set monitor-warnings
16060 @kindex set monitor-warnings@r{, MIPS remote}
16061 Enable or disable monitor warnings about hardware breakpoints. This
16062 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16063 display warning messages whose codes are returned by the @code{lsi}
16064 PMON monitor for breakpoint commands.
16066 @item show monitor-warnings
16067 @kindex show monitor-warnings@r{, MIPS remote}
16068 Show the current setting of printing monitor warnings.
16070 @item pmon @var{command}
16071 @kindex pmon@r{, MIPS remote}
16072 @cindex send PMON command
16073 This command allows sending an arbitrary @var{command} string to the
16074 monitor. The monitor must be in debug mode for this to work.
16077 @node OpenRISC 1000
16078 @subsection OpenRISC 1000
16079 @cindex OpenRISC 1000
16081 @cindex or1k boards
16082 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16083 about platform and commands.
16087 @kindex target jtag
16088 @item target jtag jtag://@var{host}:@var{port}
16090 Connects to remote JTAG server.
16091 JTAG remote server can be either an or1ksim or JTAG server,
16092 connected via parallel port to the board.
16094 Example: @code{target jtag jtag://localhost:9999}
16097 @item or1ksim @var{command}
16098 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16099 Simulator, proprietary commands can be executed.
16101 @kindex info or1k spr
16102 @item info or1k spr
16103 Displays spr groups.
16105 @item info or1k spr @var{group}
16106 @itemx info or1k spr @var{groupno}
16107 Displays register names in selected group.
16109 @item info or1k spr @var{group} @var{register}
16110 @itemx info or1k spr @var{register}
16111 @itemx info or1k spr @var{groupno} @var{registerno}
16112 @itemx info or1k spr @var{registerno}
16113 Shows information about specified spr register.
16116 @item spr @var{group} @var{register} @var{value}
16117 @itemx spr @var{register @var{value}}
16118 @itemx spr @var{groupno} @var{registerno @var{value}}
16119 @itemx spr @var{registerno @var{value}}
16120 Writes @var{value} to specified spr register.
16123 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16124 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16125 program execution and is thus much faster. Hardware breakpoints/watchpoint
16126 triggers can be set using:
16129 Load effective address/data
16131 Store effective address/data
16133 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16138 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16139 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16141 @code{htrace} commands:
16142 @cindex OpenRISC 1000 htrace
16145 @item hwatch @var{conditional}
16146 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16147 or Data. For example:
16149 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16151 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16155 Display information about current HW trace configuration.
16157 @item htrace trigger @var{conditional}
16158 Set starting criteria for HW trace.
16160 @item htrace qualifier @var{conditional}
16161 Set acquisition qualifier for HW trace.
16163 @item htrace stop @var{conditional}
16164 Set HW trace stopping criteria.
16166 @item htrace record [@var{data}]*
16167 Selects the data to be recorded, when qualifier is met and HW trace was
16170 @item htrace enable
16171 @itemx htrace disable
16172 Enables/disables the HW trace.
16174 @item htrace rewind [@var{filename}]
16175 Clears currently recorded trace data.
16177 If filename is specified, new trace file is made and any newly collected data
16178 will be written there.
16180 @item htrace print [@var{start} [@var{len}]]
16181 Prints trace buffer, using current record configuration.
16183 @item htrace mode continuous
16184 Set continuous trace mode.
16186 @item htrace mode suspend
16187 Set suspend trace mode.
16191 @node PowerPC Embedded
16192 @subsection PowerPC Embedded
16194 @value{GDBN} provides the following PowerPC-specific commands:
16197 @kindex set powerpc
16198 @item set powerpc soft-float
16199 @itemx show powerpc soft-float
16200 Force @value{GDBN} to use (or not use) a software floating point calling
16201 convention. By default, @value{GDBN} selects the calling convention based
16202 on the selected architecture and the provided executable file.
16204 @item set powerpc vector-abi
16205 @itemx show powerpc vector-abi
16206 Force @value{GDBN} to use the specified calling convention for vector
16207 arguments and return values. The valid options are @samp{auto};
16208 @samp{generic}, to avoid vector registers even if they are present;
16209 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16210 registers. By default, @value{GDBN} selects the calling convention
16211 based on the selected architecture and the provided executable file.
16213 @kindex target dink32
16214 @item target dink32 @var{dev}
16215 DINK32 ROM monitor.
16217 @kindex target ppcbug
16218 @item target ppcbug @var{dev}
16219 @kindex target ppcbug1
16220 @item target ppcbug1 @var{dev}
16221 PPCBUG ROM monitor for PowerPC.
16224 @item target sds @var{dev}
16225 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16228 @cindex SDS protocol
16229 The following commands specific to the SDS protocol are supported
16233 @item set sdstimeout @var{nsec}
16234 @kindex set sdstimeout
16235 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16236 default is 2 seconds.
16238 @item show sdstimeout
16239 @kindex show sdstimeout
16240 Show the current value of the SDS timeout.
16242 @item sds @var{command}
16243 @kindex sds@r{, a command}
16244 Send the specified @var{command} string to the SDS monitor.
16249 @subsection HP PA Embedded
16253 @kindex target op50n
16254 @item target op50n @var{dev}
16255 OP50N monitor, running on an OKI HPPA board.
16257 @kindex target w89k
16258 @item target w89k @var{dev}
16259 W89K monitor, running on a Winbond HPPA board.
16264 @subsection Tsqware Sparclet
16268 @value{GDBN} enables developers to debug tasks running on
16269 Sparclet targets from a Unix host.
16270 @value{GDBN} uses code that runs on
16271 both the Unix host and on the Sparclet target. The program
16272 @code{@value{GDBP}} is installed and executed on the Unix host.
16275 @item remotetimeout @var{args}
16276 @kindex remotetimeout
16277 @value{GDBN} supports the option @code{remotetimeout}.
16278 This option is set by the user, and @var{args} represents the number of
16279 seconds @value{GDBN} waits for responses.
16282 @cindex compiling, on Sparclet
16283 When compiling for debugging, include the options @samp{-g} to get debug
16284 information and @samp{-Ttext} to relocate the program to where you wish to
16285 load it on the target. You may also want to add the options @samp{-n} or
16286 @samp{-N} in order to reduce the size of the sections. Example:
16289 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16292 You can use @code{objdump} to verify that the addresses are what you intended:
16295 sparclet-aout-objdump --headers --syms prog
16298 @cindex running, on Sparclet
16300 your Unix execution search path to find @value{GDBN}, you are ready to
16301 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16302 (or @code{sparclet-aout-gdb}, depending on your installation).
16304 @value{GDBN} comes up showing the prompt:
16311 * Sparclet File:: Setting the file to debug
16312 * Sparclet Connection:: Connecting to Sparclet
16313 * Sparclet Download:: Sparclet download
16314 * Sparclet Execution:: Running and debugging
16317 @node Sparclet File
16318 @subsubsection Setting File to Debug
16320 The @value{GDBN} command @code{file} lets you choose with program to debug.
16323 (gdbslet) file prog
16327 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16328 @value{GDBN} locates
16329 the file by searching the directories listed in the command search
16331 If the file was compiled with debug information (option @samp{-g}), source
16332 files will be searched as well.
16333 @value{GDBN} locates
16334 the source files by searching the directories listed in the directory search
16335 path (@pxref{Environment, ,Your Program's Environment}).
16337 to find a file, it displays a message such as:
16340 prog: No such file or directory.
16343 When this happens, add the appropriate directories to the search paths with
16344 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16345 @code{target} command again.
16347 @node Sparclet Connection
16348 @subsubsection Connecting to Sparclet
16350 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16351 To connect to a target on serial port ``@code{ttya}'', type:
16354 (gdbslet) target sparclet /dev/ttya
16355 Remote target sparclet connected to /dev/ttya
16356 main () at ../prog.c:3
16360 @value{GDBN} displays messages like these:
16366 @node Sparclet Download
16367 @subsubsection Sparclet Download
16369 @cindex download to Sparclet
16370 Once connected to the Sparclet target,
16371 you can use the @value{GDBN}
16372 @code{load} command to download the file from the host to the target.
16373 The file name and load offset should be given as arguments to the @code{load}
16375 Since the file format is aout, the program must be loaded to the starting
16376 address. You can use @code{objdump} to find out what this value is. The load
16377 offset is an offset which is added to the VMA (virtual memory address)
16378 of each of the file's sections.
16379 For instance, if the program
16380 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16381 and bss at 0x12010170, in @value{GDBN}, type:
16384 (gdbslet) load prog 0x12010000
16385 Loading section .text, size 0xdb0 vma 0x12010000
16388 If the code is loaded at a different address then what the program was linked
16389 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16390 to tell @value{GDBN} where to map the symbol table.
16392 @node Sparclet Execution
16393 @subsubsection Running and Debugging
16395 @cindex running and debugging Sparclet programs
16396 You can now begin debugging the task using @value{GDBN}'s execution control
16397 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16398 manual for the list of commands.
16402 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16404 Starting program: prog
16405 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16406 3 char *symarg = 0;
16408 4 char *execarg = "hello!";
16413 @subsection Fujitsu Sparclite
16417 @kindex target sparclite
16418 @item target sparclite @var{dev}
16419 Fujitsu sparclite boards, used only for the purpose of loading.
16420 You must use an additional command to debug the program.
16421 For example: target remote @var{dev} using @value{GDBN} standard
16427 @subsection Zilog Z8000
16430 @cindex simulator, Z8000
16431 @cindex Zilog Z8000 simulator
16433 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16436 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16437 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16438 segmented variant). The simulator recognizes which architecture is
16439 appropriate by inspecting the object code.
16442 @item target sim @var{args}
16444 @kindex target sim@r{, with Z8000}
16445 Debug programs on a simulated CPU. If the simulator supports setup
16446 options, specify them via @var{args}.
16450 After specifying this target, you can debug programs for the simulated
16451 CPU in the same style as programs for your host computer; use the
16452 @code{file} command to load a new program image, the @code{run} command
16453 to run your program, and so on.
16455 As well as making available all the usual machine registers
16456 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16457 additional items of information as specially named registers:
16462 Counts clock-ticks in the simulator.
16465 Counts instructions run in the simulator.
16468 Execution time in 60ths of a second.
16472 You can refer to these values in @value{GDBN} expressions with the usual
16473 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16474 conditional breakpoint that suspends only after at least 5000
16475 simulated clock ticks.
16478 @subsection Atmel AVR
16481 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16482 following AVR-specific commands:
16485 @item info io_registers
16486 @kindex info io_registers@r{, AVR}
16487 @cindex I/O registers (Atmel AVR)
16488 This command displays information about the AVR I/O registers. For
16489 each register, @value{GDBN} prints its number and value.
16496 When configured for debugging CRIS, @value{GDBN} provides the
16497 following CRIS-specific commands:
16500 @item set cris-version @var{ver}
16501 @cindex CRIS version
16502 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16503 The CRIS version affects register names and sizes. This command is useful in
16504 case autodetection of the CRIS version fails.
16506 @item show cris-version
16507 Show the current CRIS version.
16509 @item set cris-dwarf2-cfi
16510 @cindex DWARF-2 CFI and CRIS
16511 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16512 Change to @samp{off} when using @code{gcc-cris} whose version is below
16515 @item show cris-dwarf2-cfi
16516 Show the current state of using DWARF-2 CFI.
16518 @item set cris-mode @var{mode}
16520 Set the current CRIS mode to @var{mode}. It should only be changed when
16521 debugging in guru mode, in which case it should be set to
16522 @samp{guru} (the default is @samp{normal}).
16524 @item show cris-mode
16525 Show the current CRIS mode.
16529 @subsection Renesas Super-H
16532 For the Renesas Super-H processor, @value{GDBN} provides these
16537 @kindex regs@r{, Super-H}
16538 Show the values of all Super-H registers.
16540 @item set sh calling-convention @var{convention}
16541 @kindex set sh calling-convention
16542 Set the calling-convention used when calling functions from @value{GDBN}.
16543 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16544 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16545 convention. If the DWARF-2 information of the called function specifies
16546 that the function follows the Renesas calling convention, the function
16547 is called using the Renesas calling convention. If the calling convention
16548 is set to @samp{renesas}, the Renesas calling convention is always used,
16549 regardless of the DWARF-2 information. This can be used to override the
16550 default of @samp{gcc} if debug information is missing, or the compiler
16551 does not emit the DWARF-2 calling convention entry for a function.
16553 @item show sh calling-convention
16554 @kindex show sh calling-convention
16555 Show the current calling convention setting.
16560 @node Architectures
16561 @section Architectures
16563 This section describes characteristics of architectures that affect
16564 all uses of @value{GDBN} with the architecture, both native and cross.
16571 * HPPA:: HP PA architecture
16572 * SPU:: Cell Broadband Engine SPU architecture
16577 @subsection x86 Architecture-specific Issues
16580 @item set struct-convention @var{mode}
16581 @kindex set struct-convention
16582 @cindex struct return convention
16583 @cindex struct/union returned in registers
16584 Set the convention used by the inferior to return @code{struct}s and
16585 @code{union}s from functions to @var{mode}. Possible values of
16586 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16587 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16588 are returned on the stack, while @code{"reg"} means that a
16589 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16590 be returned in a register.
16592 @item show struct-convention
16593 @kindex show struct-convention
16594 Show the current setting of the convention to return @code{struct}s
16603 @kindex set rstack_high_address
16604 @cindex AMD 29K register stack
16605 @cindex register stack, AMD29K
16606 @item set rstack_high_address @var{address}
16607 On AMD 29000 family processors, registers are saved in a separate
16608 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16609 extent of this stack. Normally, @value{GDBN} just assumes that the
16610 stack is ``large enough''. This may result in @value{GDBN} referencing
16611 memory locations that do not exist. If necessary, you can get around
16612 this problem by specifying the ending address of the register stack with
16613 the @code{set rstack_high_address} command. The argument should be an
16614 address, which you probably want to precede with @samp{0x} to specify in
16617 @kindex show rstack_high_address
16618 @item show rstack_high_address
16619 Display the current limit of the register stack, on AMD 29000 family
16627 See the following section.
16632 @cindex stack on Alpha
16633 @cindex stack on MIPS
16634 @cindex Alpha stack
16636 Alpha- and MIPS-based computers use an unusual stack frame, which
16637 sometimes requires @value{GDBN} to search backward in the object code to
16638 find the beginning of a function.
16640 @cindex response time, MIPS debugging
16641 To improve response time (especially for embedded applications, where
16642 @value{GDBN} may be restricted to a slow serial line for this search)
16643 you may want to limit the size of this search, using one of these
16647 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16648 @item set heuristic-fence-post @var{limit}
16649 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16650 search for the beginning of a function. A value of @var{0} (the
16651 default) means there is no limit. However, except for @var{0}, the
16652 larger the limit the more bytes @code{heuristic-fence-post} must search
16653 and therefore the longer it takes to run. You should only need to use
16654 this command when debugging a stripped executable.
16656 @item show heuristic-fence-post
16657 Display the current limit.
16661 These commands are available @emph{only} when @value{GDBN} is configured
16662 for debugging programs on Alpha or MIPS processors.
16664 Several MIPS-specific commands are available when debugging MIPS
16668 @item set mips abi @var{arg}
16669 @kindex set mips abi
16670 @cindex set ABI for MIPS
16671 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16672 values of @var{arg} are:
16676 The default ABI associated with the current binary (this is the
16687 @item show mips abi
16688 @kindex show mips abi
16689 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16692 @itemx show mipsfpu
16693 @xref{MIPS Embedded, set mipsfpu}.
16695 @item set mips mask-address @var{arg}
16696 @kindex set mips mask-address
16697 @cindex MIPS addresses, masking
16698 This command determines whether the most-significant 32 bits of 64-bit
16699 MIPS addresses are masked off. The argument @var{arg} can be
16700 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16701 setting, which lets @value{GDBN} determine the correct value.
16703 @item show mips mask-address
16704 @kindex show mips mask-address
16705 Show whether the upper 32 bits of MIPS addresses are masked off or
16708 @item set remote-mips64-transfers-32bit-regs
16709 @kindex set remote-mips64-transfers-32bit-regs
16710 This command controls compatibility with 64-bit MIPS targets that
16711 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16712 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16713 and 64 bits for other registers, set this option to @samp{on}.
16715 @item show remote-mips64-transfers-32bit-regs
16716 @kindex show remote-mips64-transfers-32bit-regs
16717 Show the current setting of compatibility with older MIPS 64 targets.
16719 @item set debug mips
16720 @kindex set debug mips
16721 This command turns on and off debugging messages for the MIPS-specific
16722 target code in @value{GDBN}.
16724 @item show debug mips
16725 @kindex show debug mips
16726 Show the current setting of MIPS debugging messages.
16732 @cindex HPPA support
16734 When @value{GDBN} is debugging the HP PA architecture, it provides the
16735 following special commands:
16738 @item set debug hppa
16739 @kindex set debug hppa
16740 This command determines whether HPPA architecture-specific debugging
16741 messages are to be displayed.
16743 @item show debug hppa
16744 Show whether HPPA debugging messages are displayed.
16746 @item maint print unwind @var{address}
16747 @kindex maint print unwind@r{, HPPA}
16748 This command displays the contents of the unwind table entry at the
16749 given @var{address}.
16755 @subsection Cell Broadband Engine SPU architecture
16756 @cindex Cell Broadband Engine
16759 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16760 it provides the following special commands:
16763 @item info spu event
16765 Display SPU event facility status. Shows current event mask
16766 and pending event status.
16768 @item info spu signal
16769 Display SPU signal notification facility status. Shows pending
16770 signal-control word and signal notification mode of both signal
16771 notification channels.
16773 @item info spu mailbox
16774 Display SPU mailbox facility status. Shows all pending entries,
16775 in order of processing, in each of the SPU Write Outbound,
16776 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16779 Display MFC DMA status. Shows all pending commands in the MFC
16780 DMA queue. For each entry, opcode, tag, class IDs, effective
16781 and local store addresses and transfer size are shown.
16783 @item info spu proxydma
16784 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16785 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16786 and local store addresses and transfer size are shown.
16791 @subsection PowerPC
16792 @cindex PowerPC architecture
16794 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16795 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16796 numbers stored in the floating point registers. These values must be stored
16797 in two consecutive registers, always starting at an even register like
16798 @code{f0} or @code{f2}.
16800 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16801 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16802 @code{f2} and @code{f3} for @code{$dl1} and so on.
16804 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16805 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16808 @node Controlling GDB
16809 @chapter Controlling @value{GDBN}
16811 You can alter the way @value{GDBN} interacts with you by using the
16812 @code{set} command. For commands controlling how @value{GDBN} displays
16813 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16818 * Editing:: Command editing
16819 * Command History:: Command history
16820 * Screen Size:: Screen size
16821 * Numbers:: Numbers
16822 * ABI:: Configuring the current ABI
16823 * Messages/Warnings:: Optional warnings and messages
16824 * Debugging Output:: Optional messages about internal happenings
16832 @value{GDBN} indicates its readiness to read a command by printing a string
16833 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16834 can change the prompt string with the @code{set prompt} command. For
16835 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16836 the prompt in one of the @value{GDBN} sessions so that you can always tell
16837 which one you are talking to.
16839 @emph{Note:} @code{set prompt} does not add a space for you after the
16840 prompt you set. This allows you to set a prompt which ends in a space
16841 or a prompt that does not.
16845 @item set prompt @var{newprompt}
16846 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16848 @kindex show prompt
16850 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16854 @section Command Editing
16856 @cindex command line editing
16858 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16859 @sc{gnu} library provides consistent behavior for programs which provide a
16860 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16861 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16862 substitution, and a storage and recall of command history across
16863 debugging sessions.
16865 You may control the behavior of command line editing in @value{GDBN} with the
16866 command @code{set}.
16869 @kindex set editing
16872 @itemx set editing on
16873 Enable command line editing (enabled by default).
16875 @item set editing off
16876 Disable command line editing.
16878 @kindex show editing
16880 Show whether command line editing is enabled.
16883 @xref{Command Line Editing}, for more details about the Readline
16884 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16885 encouraged to read that chapter.
16887 @node Command History
16888 @section Command History
16889 @cindex command history
16891 @value{GDBN} can keep track of the commands you type during your
16892 debugging sessions, so that you can be certain of precisely what
16893 happened. Use these commands to manage the @value{GDBN} command
16896 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16897 package, to provide the history facility. @xref{Using History
16898 Interactively}, for the detailed description of the History library.
16900 To issue a command to @value{GDBN} without affecting certain aspects of
16901 the state which is seen by users, prefix it with @samp{server }
16902 (@pxref{Server Prefix}). This
16903 means that this command will not affect the command history, nor will it
16904 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16905 pressed on a line by itself.
16907 @cindex @code{server}, command prefix
16908 The server prefix does not affect the recording of values into the value
16909 history; to print a value without recording it into the value history,
16910 use the @code{output} command instead of the @code{print} command.
16912 Here is the description of @value{GDBN} commands related to command
16916 @cindex history substitution
16917 @cindex history file
16918 @kindex set history filename
16919 @cindex @env{GDBHISTFILE}, environment variable
16920 @item set history filename @var{fname}
16921 Set the name of the @value{GDBN} command history file to @var{fname}.
16922 This is the file where @value{GDBN} reads an initial command history
16923 list, and where it writes the command history from this session when it
16924 exits. You can access this list through history expansion or through
16925 the history command editing characters listed below. This file defaults
16926 to the value of the environment variable @code{GDBHISTFILE}, or to
16927 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16930 @cindex save command history
16931 @kindex set history save
16932 @item set history save
16933 @itemx set history save on
16934 Record command history in a file, whose name may be specified with the
16935 @code{set history filename} command. By default, this option is disabled.
16937 @item set history save off
16938 Stop recording command history in a file.
16940 @cindex history size
16941 @kindex set history size
16942 @cindex @env{HISTSIZE}, environment variable
16943 @item set history size @var{size}
16944 Set the number of commands which @value{GDBN} keeps in its history list.
16945 This defaults to the value of the environment variable
16946 @code{HISTSIZE}, or to 256 if this variable is not set.
16949 History expansion assigns special meaning to the character @kbd{!}.
16950 @xref{Event Designators}, for more details.
16952 @cindex history expansion, turn on/off
16953 Since @kbd{!} is also the logical not operator in C, history expansion
16954 is off by default. If you decide to enable history expansion with the
16955 @code{set history expansion on} command, you may sometimes need to
16956 follow @kbd{!} (when it is used as logical not, in an expression) with
16957 a space or a tab to prevent it from being expanded. The readline
16958 history facilities do not attempt substitution on the strings
16959 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16961 The commands to control history expansion are:
16964 @item set history expansion on
16965 @itemx set history expansion
16966 @kindex set history expansion
16967 Enable history expansion. History expansion is off by default.
16969 @item set history expansion off
16970 Disable history expansion.
16973 @kindex show history
16975 @itemx show history filename
16976 @itemx show history save
16977 @itemx show history size
16978 @itemx show history expansion
16979 These commands display the state of the @value{GDBN} history parameters.
16980 @code{show history} by itself displays all four states.
16985 @kindex show commands
16986 @cindex show last commands
16987 @cindex display command history
16988 @item show commands
16989 Display the last ten commands in the command history.
16991 @item show commands @var{n}
16992 Print ten commands centered on command number @var{n}.
16994 @item show commands +
16995 Print ten commands just after the commands last printed.
16999 @section Screen Size
17000 @cindex size of screen
17001 @cindex pauses in output
17003 Certain commands to @value{GDBN} may produce large amounts of
17004 information output to the screen. To help you read all of it,
17005 @value{GDBN} pauses and asks you for input at the end of each page of
17006 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17007 to discard the remaining output. Also, the screen width setting
17008 determines when to wrap lines of output. Depending on what is being
17009 printed, @value{GDBN} tries to break the line at a readable place,
17010 rather than simply letting it overflow onto the following line.
17012 Normally @value{GDBN} knows the size of the screen from the terminal
17013 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17014 together with the value of the @code{TERM} environment variable and the
17015 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17016 you can override it with the @code{set height} and @code{set
17023 @kindex show height
17024 @item set height @var{lpp}
17026 @itemx set width @var{cpl}
17028 These @code{set} commands specify a screen height of @var{lpp} lines and
17029 a screen width of @var{cpl} characters. The associated @code{show}
17030 commands display the current settings.
17032 If you specify a height of zero lines, @value{GDBN} does not pause during
17033 output no matter how long the output is. This is useful if output is to a
17034 file or to an editor buffer.
17036 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17037 from wrapping its output.
17039 @item set pagination on
17040 @itemx set pagination off
17041 @kindex set pagination
17042 Turn the output pagination on or off; the default is on. Turning
17043 pagination off is the alternative to @code{set height 0}.
17045 @item show pagination
17046 @kindex show pagination
17047 Show the current pagination mode.
17052 @cindex number representation
17053 @cindex entering numbers
17055 You can always enter numbers in octal, decimal, or hexadecimal in
17056 @value{GDBN} by the usual conventions: octal numbers begin with
17057 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17058 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17059 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17060 10; likewise, the default display for numbers---when no particular
17061 format is specified---is base 10. You can change the default base for
17062 both input and output with the commands described below.
17065 @kindex set input-radix
17066 @item set input-radix @var{base}
17067 Set the default base for numeric input. Supported choices
17068 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17069 specified either unambiguously or using the current input radix; for
17073 set input-radix 012
17074 set input-radix 10.
17075 set input-radix 0xa
17079 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17080 leaves the input radix unchanged, no matter what it was, since
17081 @samp{10}, being without any leading or trailing signs of its base, is
17082 interpreted in the current radix. Thus, if the current radix is 16,
17083 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17086 @kindex set output-radix
17087 @item set output-radix @var{base}
17088 Set the default base for numeric display. Supported choices
17089 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17090 specified either unambiguously or using the current input radix.
17092 @kindex show input-radix
17093 @item show input-radix
17094 Display the current default base for numeric input.
17096 @kindex show output-radix
17097 @item show output-radix
17098 Display the current default base for numeric display.
17100 @item set radix @r{[}@var{base}@r{]}
17104 These commands set and show the default base for both input and output
17105 of numbers. @code{set radix} sets the radix of input and output to
17106 the same base; without an argument, it resets the radix back to its
17107 default value of 10.
17112 @section Configuring the Current ABI
17114 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17115 application automatically. However, sometimes you need to override its
17116 conclusions. Use these commands to manage @value{GDBN}'s view of the
17123 One @value{GDBN} configuration can debug binaries for multiple operating
17124 system targets, either via remote debugging or native emulation.
17125 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17126 but you can override its conclusion using the @code{set osabi} command.
17127 One example where this is useful is in debugging of binaries which use
17128 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17129 not have the same identifying marks that the standard C library for your
17134 Show the OS ABI currently in use.
17137 With no argument, show the list of registered available OS ABI's.
17139 @item set osabi @var{abi}
17140 Set the current OS ABI to @var{abi}.
17143 @cindex float promotion
17145 Generally, the way that an argument of type @code{float} is passed to a
17146 function depends on whether the function is prototyped. For a prototyped
17147 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17148 according to the architecture's convention for @code{float}. For unprototyped
17149 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17150 @code{double} and then passed.
17152 Unfortunately, some forms of debug information do not reliably indicate whether
17153 a function is prototyped. If @value{GDBN} calls a function that is not marked
17154 as prototyped, it consults @kbd{set coerce-float-to-double}.
17157 @kindex set coerce-float-to-double
17158 @item set coerce-float-to-double
17159 @itemx set coerce-float-to-double on
17160 Arguments of type @code{float} will be promoted to @code{double} when passed
17161 to an unprototyped function. This is the default setting.
17163 @item set coerce-float-to-double off
17164 Arguments of type @code{float} will be passed directly to unprototyped
17167 @kindex show coerce-float-to-double
17168 @item show coerce-float-to-double
17169 Show the current setting of promoting @code{float} to @code{double}.
17173 @kindex show cp-abi
17174 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17175 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17176 used to build your application. @value{GDBN} only fully supports
17177 programs with a single C@t{++} ABI; if your program contains code using
17178 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17179 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17180 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17181 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17182 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17183 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17188 Show the C@t{++} ABI currently in use.
17191 With no argument, show the list of supported C@t{++} ABI's.
17193 @item set cp-abi @var{abi}
17194 @itemx set cp-abi auto
17195 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17198 @node Messages/Warnings
17199 @section Optional Warnings and Messages
17201 @cindex verbose operation
17202 @cindex optional warnings
17203 By default, @value{GDBN} is silent about its inner workings. If you are
17204 running on a slow machine, you may want to use the @code{set verbose}
17205 command. This makes @value{GDBN} tell you when it does a lengthy
17206 internal operation, so you will not think it has crashed.
17208 Currently, the messages controlled by @code{set verbose} are those
17209 which announce that the symbol table for a source file is being read;
17210 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17213 @kindex set verbose
17214 @item set verbose on
17215 Enables @value{GDBN} output of certain informational messages.
17217 @item set verbose off
17218 Disables @value{GDBN} output of certain informational messages.
17220 @kindex show verbose
17222 Displays whether @code{set verbose} is on or off.
17225 By default, if @value{GDBN} encounters bugs in the symbol table of an
17226 object file, it is silent; but if you are debugging a compiler, you may
17227 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17232 @kindex set complaints
17233 @item set complaints @var{limit}
17234 Permits @value{GDBN} to output @var{limit} complaints about each type of
17235 unusual symbols before becoming silent about the problem. Set
17236 @var{limit} to zero to suppress all complaints; set it to a large number
17237 to prevent complaints from being suppressed.
17239 @kindex show complaints
17240 @item show complaints
17241 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17245 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17246 lot of stupid questions to confirm certain commands. For example, if
17247 you try to run a program which is already running:
17251 The program being debugged has been started already.
17252 Start it from the beginning? (y or n)
17255 If you are willing to unflinchingly face the consequences of your own
17256 commands, you can disable this ``feature'':
17260 @kindex set confirm
17262 @cindex confirmation
17263 @cindex stupid questions
17264 @item set confirm off
17265 Disables confirmation requests.
17267 @item set confirm on
17268 Enables confirmation requests (the default).
17270 @kindex show confirm
17272 Displays state of confirmation requests.
17276 @cindex command tracing
17277 If you need to debug user-defined commands or sourced files you may find it
17278 useful to enable @dfn{command tracing}. In this mode each command will be
17279 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17280 quantity denoting the call depth of each command.
17283 @kindex set trace-commands
17284 @cindex command scripts, debugging
17285 @item set trace-commands on
17286 Enable command tracing.
17287 @item set trace-commands off
17288 Disable command tracing.
17289 @item show trace-commands
17290 Display the current state of command tracing.
17293 @node Debugging Output
17294 @section Optional Messages about Internal Happenings
17295 @cindex optional debugging messages
17297 @value{GDBN} has commands that enable optional debugging messages from
17298 various @value{GDBN} subsystems; normally these commands are of
17299 interest to @value{GDBN} maintainers, or when reporting a bug. This
17300 section documents those commands.
17303 @kindex set exec-done-display
17304 @item set exec-done-display
17305 Turns on or off the notification of asynchronous commands'
17306 completion. When on, @value{GDBN} will print a message when an
17307 asynchronous command finishes its execution. The default is off.
17308 @kindex show exec-done-display
17309 @item show exec-done-display
17310 Displays the current setting of asynchronous command completion
17313 @cindex gdbarch debugging info
17314 @cindex architecture debugging info
17315 @item set debug arch
17316 Turns on or off display of gdbarch debugging info. The default is off
17318 @item show debug arch
17319 Displays the current state of displaying gdbarch debugging info.
17320 @item set debug aix-thread
17321 @cindex AIX threads
17322 Display debugging messages about inner workings of the AIX thread
17324 @item show debug aix-thread
17325 Show the current state of AIX thread debugging info display.
17326 @item set debug dwarf2-die
17327 @cindex DWARF2 DIEs
17328 Dump DWARF2 DIEs after they are read in.
17329 The value is the number of nesting levels to print.
17330 A value of zero turns off the display.
17331 @item show debug dwarf2-die
17332 Show the current state of DWARF2 DIE debugging.
17333 @item set debug displaced
17334 @cindex displaced stepping debugging info
17335 Turns on or off display of @value{GDBN} debugging info for the
17336 displaced stepping support. The default is off.
17337 @item show debug displaced
17338 Displays the current state of displaying @value{GDBN} debugging info
17339 related to displaced stepping.
17340 @item set debug event
17341 @cindex event debugging info
17342 Turns on or off display of @value{GDBN} event debugging info. The
17344 @item show debug event
17345 Displays the current state of displaying @value{GDBN} event debugging
17347 @item set debug expression
17348 @cindex expression debugging info
17349 Turns on or off display of debugging info about @value{GDBN}
17350 expression parsing. The default is off.
17351 @item show debug expression
17352 Displays the current state of displaying debugging info about
17353 @value{GDBN} expression parsing.
17354 @item set debug frame
17355 @cindex frame debugging info
17356 Turns on or off display of @value{GDBN} frame debugging info. The
17358 @item show debug frame
17359 Displays the current state of displaying @value{GDBN} frame debugging
17361 @item set debug infrun
17362 @cindex inferior debugging info
17363 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17364 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17365 for implementing operations such as single-stepping the inferior.
17366 @item show debug infrun
17367 Displays the current state of @value{GDBN} inferior debugging.
17368 @item set debug lin-lwp
17369 @cindex @sc{gnu}/Linux LWP debug messages
17370 @cindex Linux lightweight processes
17371 Turns on or off debugging messages from the Linux LWP debug support.
17372 @item show debug lin-lwp
17373 Show the current state of Linux LWP debugging messages.
17374 @item set debug lin-lwp-async
17375 @cindex @sc{gnu}/Linux LWP async debug messages
17376 @cindex Linux lightweight processes
17377 Turns on or off debugging messages from the Linux LWP async debug support.
17378 @item show debug lin-lwp-async
17379 Show the current state of Linux LWP async debugging messages.
17380 @item set debug observer
17381 @cindex observer debugging info
17382 Turns on or off display of @value{GDBN} observer debugging. This
17383 includes info such as the notification of observable events.
17384 @item show debug observer
17385 Displays the current state of observer debugging.
17386 @item set debug overload
17387 @cindex C@t{++} overload debugging info
17388 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17389 info. This includes info such as ranking of functions, etc. The default
17391 @item show debug overload
17392 Displays the current state of displaying @value{GDBN} C@t{++} overload
17394 @cindex packets, reporting on stdout
17395 @cindex serial connections, debugging
17396 @cindex debug remote protocol
17397 @cindex remote protocol debugging
17398 @cindex display remote packets
17399 @item set debug remote
17400 Turns on or off display of reports on all packets sent back and forth across
17401 the serial line to the remote machine. The info is printed on the
17402 @value{GDBN} standard output stream. The default is off.
17403 @item show debug remote
17404 Displays the state of display of remote packets.
17405 @item set debug serial
17406 Turns on or off display of @value{GDBN} serial debugging info. The
17408 @item show debug serial
17409 Displays the current state of displaying @value{GDBN} serial debugging
17411 @item set debug solib-frv
17412 @cindex FR-V shared-library debugging
17413 Turns on or off debugging messages for FR-V shared-library code.
17414 @item show debug solib-frv
17415 Display the current state of FR-V shared-library code debugging
17417 @item set debug target
17418 @cindex target debugging info
17419 Turns on or off display of @value{GDBN} target debugging info. This info
17420 includes what is going on at the target level of GDB, as it happens. The
17421 default is 0. Set it to 1 to track events, and to 2 to also track the
17422 value of large memory transfers. Changes to this flag do not take effect
17423 until the next time you connect to a target or use the @code{run} command.
17424 @item show debug target
17425 Displays the current state of displaying @value{GDBN} target debugging
17427 @item set debug timestamp
17428 @cindex timestampping debugging info
17429 Turns on or off display of timestamps with @value{GDBN} debugging info.
17430 When enabled, seconds and microseconds are displayed before each debugging
17432 @item show debug timestamp
17433 Displays the current state of displaying timestamps with @value{GDBN}
17435 @item set debugvarobj
17436 @cindex variable object debugging info
17437 Turns on or off display of @value{GDBN} variable object debugging
17438 info. The default is off.
17439 @item show debugvarobj
17440 Displays the current state of displaying @value{GDBN} variable object
17442 @item set debug xml
17443 @cindex XML parser debugging
17444 Turns on or off debugging messages for built-in XML parsers.
17445 @item show debug xml
17446 Displays the current state of XML debugging messages.
17449 @node Extending GDB
17450 @chapter Extending @value{GDBN}
17451 @cindex extending GDB
17453 @value{GDBN} provides two mechanisms for extension. The first is based
17454 on composition of @value{GDBN} commands, and the second is based on the
17455 Python scripting language.
17458 * Sequences:: Canned Sequences of Commands
17459 * Python:: Scripting @value{GDBN} using Python
17463 @section Canned Sequences of Commands
17465 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17466 Command Lists}), @value{GDBN} provides two ways to store sequences of
17467 commands for execution as a unit: user-defined commands and command
17471 * Define:: How to define your own commands
17472 * Hooks:: Hooks for user-defined commands
17473 * Command Files:: How to write scripts of commands to be stored in a file
17474 * Output:: Commands for controlled output
17478 @subsection User-defined Commands
17480 @cindex user-defined command
17481 @cindex arguments, to user-defined commands
17482 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17483 which you assign a new name as a command. This is done with the
17484 @code{define} command. User commands may accept up to 10 arguments
17485 separated by whitespace. Arguments are accessed within the user command
17486 via @code{$arg0@dots{}$arg9}. A trivial example:
17490 print $arg0 + $arg1 + $arg2
17495 To execute the command use:
17502 This defines the command @code{adder}, which prints the sum of
17503 its three arguments. Note the arguments are text substitutions, so they may
17504 reference variables, use complex expressions, or even perform inferior
17507 @cindex argument count in user-defined commands
17508 @cindex how many arguments (user-defined commands)
17509 In addition, @code{$argc} may be used to find out how many arguments have
17510 been passed. This expands to a number in the range 0@dots{}10.
17515 print $arg0 + $arg1
17518 print $arg0 + $arg1 + $arg2
17526 @item define @var{commandname}
17527 Define a command named @var{commandname}. If there is already a command
17528 by that name, you are asked to confirm that you want to redefine it.
17530 The definition of the command is made up of other @value{GDBN} command lines,
17531 which are given following the @code{define} command. The end of these
17532 commands is marked by a line containing @code{end}.
17535 @kindex end@r{ (user-defined commands)}
17536 @item document @var{commandname}
17537 Document the user-defined command @var{commandname}, so that it can be
17538 accessed by @code{help}. The command @var{commandname} must already be
17539 defined. This command reads lines of documentation just as @code{define}
17540 reads the lines of the command definition, ending with @code{end}.
17541 After the @code{document} command is finished, @code{help} on command
17542 @var{commandname} displays the documentation you have written.
17544 You may use the @code{document} command again to change the
17545 documentation of a command. Redefining the command with @code{define}
17546 does not change the documentation.
17548 @kindex dont-repeat
17549 @cindex don't repeat command
17551 Used inside a user-defined command, this tells @value{GDBN} that this
17552 command should not be repeated when the user hits @key{RET}
17553 (@pxref{Command Syntax, repeat last command}).
17555 @kindex help user-defined
17556 @item help user-defined
17557 List all user-defined commands, with the first line of the documentation
17562 @itemx show user @var{commandname}
17563 Display the @value{GDBN} commands used to define @var{commandname} (but
17564 not its documentation). If no @var{commandname} is given, display the
17565 definitions for all user-defined commands.
17567 @cindex infinite recursion in user-defined commands
17568 @kindex show max-user-call-depth
17569 @kindex set max-user-call-depth
17570 @item show max-user-call-depth
17571 @itemx set max-user-call-depth
17572 The value of @code{max-user-call-depth} controls how many recursion
17573 levels are allowed in user-defined commands before @value{GDBN} suspects an
17574 infinite recursion and aborts the command.
17577 In addition to the above commands, user-defined commands frequently
17578 use control flow commands, described in @ref{Command Files}.
17580 When user-defined commands are executed, the
17581 commands of the definition are not printed. An error in any command
17582 stops execution of the user-defined command.
17584 If used interactively, commands that would ask for confirmation proceed
17585 without asking when used inside a user-defined command. Many @value{GDBN}
17586 commands that normally print messages to say what they are doing omit the
17587 messages when used in a user-defined command.
17590 @subsection User-defined Command Hooks
17591 @cindex command hooks
17592 @cindex hooks, for commands
17593 @cindex hooks, pre-command
17596 You may define @dfn{hooks}, which are a special kind of user-defined
17597 command. Whenever you run the command @samp{foo}, if the user-defined
17598 command @samp{hook-foo} exists, it is executed (with no arguments)
17599 before that command.
17601 @cindex hooks, post-command
17603 A hook may also be defined which is run after the command you executed.
17604 Whenever you run the command @samp{foo}, if the user-defined command
17605 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17606 that command. Post-execution hooks may exist simultaneously with
17607 pre-execution hooks, for the same command.
17609 It is valid for a hook to call the command which it hooks. If this
17610 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17612 @c It would be nice if hookpost could be passed a parameter indicating
17613 @c if the command it hooks executed properly or not. FIXME!
17615 @kindex stop@r{, a pseudo-command}
17616 In addition, a pseudo-command, @samp{stop} exists. Defining
17617 (@samp{hook-stop}) makes the associated commands execute every time
17618 execution stops in your program: before breakpoint commands are run,
17619 displays are printed, or the stack frame is printed.
17621 For example, to ignore @code{SIGALRM} signals while
17622 single-stepping, but treat them normally during normal execution,
17627 handle SIGALRM nopass
17631 handle SIGALRM pass
17634 define hook-continue
17635 handle SIGALRM pass
17639 As a further example, to hook at the beginning and end of the @code{echo}
17640 command, and to add extra text to the beginning and end of the message,
17648 define hookpost-echo
17652 (@value{GDBP}) echo Hello World
17653 <<<---Hello World--->>>
17658 You can define a hook for any single-word command in @value{GDBN}, but
17659 not for command aliases; you should define a hook for the basic command
17660 name, e.g.@: @code{backtrace} rather than @code{bt}.
17661 @c FIXME! So how does Joe User discover whether a command is an alias
17663 If an error occurs during the execution of your hook, execution of
17664 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17665 (before the command that you actually typed had a chance to run).
17667 If you try to define a hook which does not match any known command, you
17668 get a warning from the @code{define} command.
17670 @node Command Files
17671 @subsection Command Files
17673 @cindex command files
17674 @cindex scripting commands
17675 A command file for @value{GDBN} is a text file made of lines that are
17676 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17677 also be included. An empty line in a command file does nothing; it
17678 does not mean to repeat the last command, as it would from the
17681 You can request the execution of a command file with the @code{source}
17686 @cindex execute commands from a file
17687 @item source [@code{-v}] @var{filename}
17688 Execute the command file @var{filename}.
17691 The lines in a command file are generally executed sequentially,
17692 unless the order of execution is changed by one of the
17693 @emph{flow-control commands} described below. The commands are not
17694 printed as they are executed. An error in any command terminates
17695 execution of the command file and control is returned to the console.
17697 @value{GDBN} searches for @var{filename} in the current directory and then
17698 on the search path (specified with the @samp{directory} command).
17700 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17701 each command as it is executed. The option must be given before
17702 @var{filename}, and is interpreted as part of the filename anywhere else.
17704 Commands that would ask for confirmation if used interactively proceed
17705 without asking when used in a command file. Many @value{GDBN} commands that
17706 normally print messages to say what they are doing omit the messages
17707 when called from command files.
17709 @value{GDBN} also accepts command input from standard input. In this
17710 mode, normal output goes to standard output and error output goes to
17711 standard error. Errors in a command file supplied on standard input do
17712 not terminate execution of the command file---execution continues with
17716 gdb < cmds > log 2>&1
17719 (The syntax above will vary depending on the shell used.) This example
17720 will execute commands from the file @file{cmds}. All output and errors
17721 would be directed to @file{log}.
17723 Since commands stored on command files tend to be more general than
17724 commands typed interactively, they frequently need to deal with
17725 complicated situations, such as different or unexpected values of
17726 variables and symbols, changes in how the program being debugged is
17727 built, etc. @value{GDBN} provides a set of flow-control commands to
17728 deal with these complexities. Using these commands, you can write
17729 complex scripts that loop over data structures, execute commands
17730 conditionally, etc.
17737 This command allows to include in your script conditionally executed
17738 commands. The @code{if} command takes a single argument, which is an
17739 expression to evaluate. It is followed by a series of commands that
17740 are executed only if the expression is true (its value is nonzero).
17741 There can then optionally be an @code{else} line, followed by a series
17742 of commands that are only executed if the expression was false. The
17743 end of the list is marked by a line containing @code{end}.
17747 This command allows to write loops. Its syntax is similar to
17748 @code{if}: the command takes a single argument, which is an expression
17749 to evaluate, and must be followed by the commands to execute, one per
17750 line, terminated by an @code{end}. These commands are called the
17751 @dfn{body} of the loop. The commands in the body of @code{while} are
17752 executed repeatedly as long as the expression evaluates to true.
17756 This command exits the @code{while} loop in whose body it is included.
17757 Execution of the script continues after that @code{while}s @code{end}
17760 @kindex loop_continue
17761 @item loop_continue
17762 This command skips the execution of the rest of the body of commands
17763 in the @code{while} loop in whose body it is included. Execution
17764 branches to the beginning of the @code{while} loop, where it evaluates
17765 the controlling expression.
17767 @kindex end@r{ (if/else/while commands)}
17769 Terminate the block of commands that are the body of @code{if},
17770 @code{else}, or @code{while} flow-control commands.
17775 @subsection Commands for Controlled Output
17777 During the execution of a command file or a user-defined command, normal
17778 @value{GDBN} output is suppressed; the only output that appears is what is
17779 explicitly printed by the commands in the definition. This section
17780 describes three commands useful for generating exactly the output you
17785 @item echo @var{text}
17786 @c I do not consider backslash-space a standard C escape sequence
17787 @c because it is not in ANSI.
17788 Print @var{text}. Nonprinting characters can be included in
17789 @var{text} using C escape sequences, such as @samp{\n} to print a
17790 newline. @strong{No newline is printed unless you specify one.}
17791 In addition to the standard C escape sequences, a backslash followed
17792 by a space stands for a space. This is useful for displaying a
17793 string with spaces at the beginning or the end, since leading and
17794 trailing spaces are otherwise trimmed from all arguments.
17795 To print @samp{@w{ }and foo =@w{ }}, use the command
17796 @samp{echo \@w{ }and foo = \@w{ }}.
17798 A backslash at the end of @var{text} can be used, as in C, to continue
17799 the command onto subsequent lines. For example,
17802 echo This is some text\n\
17803 which is continued\n\
17804 onto several lines.\n
17807 produces the same output as
17810 echo This is some text\n
17811 echo which is continued\n
17812 echo onto several lines.\n
17816 @item output @var{expression}
17817 Print the value of @var{expression} and nothing but that value: no
17818 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17819 value history either. @xref{Expressions, ,Expressions}, for more information
17822 @item output/@var{fmt} @var{expression}
17823 Print the value of @var{expression} in format @var{fmt}. You can use
17824 the same formats as for @code{print}. @xref{Output Formats,,Output
17825 Formats}, for more information.
17828 @item printf @var{template}, @var{expressions}@dots{}
17829 Print the values of one or more @var{expressions} under the control of
17830 the string @var{template}. To print several values, make
17831 @var{expressions} be a comma-separated list of individual expressions,
17832 which may be either numbers or pointers. Their values are printed as
17833 specified by @var{template}, exactly as a C program would do by
17834 executing the code below:
17837 printf (@var{template}, @var{expressions}@dots{});
17840 As in @code{C} @code{printf}, ordinary characters in @var{template}
17841 are printed verbatim, while @dfn{conversion specification} introduced
17842 by the @samp{%} character cause subsequent @var{expressions} to be
17843 evaluated, their values converted and formatted according to type and
17844 style information encoded in the conversion specifications, and then
17847 For example, you can print two values in hex like this:
17850 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17853 @code{printf} supports all the standard @code{C} conversion
17854 specifications, including the flags and modifiers between the @samp{%}
17855 character and the conversion letter, with the following exceptions:
17859 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17862 The modifier @samp{*} is not supported for specifying precision or
17866 The @samp{'} flag (for separation of digits into groups according to
17867 @code{LC_NUMERIC'}) is not supported.
17870 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17874 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17877 The conversion letters @samp{a} and @samp{A} are not supported.
17881 Note that the @samp{ll} type modifier is supported only if the
17882 underlying @code{C} implementation used to build @value{GDBN} supports
17883 the @code{long long int} type, and the @samp{L} type modifier is
17884 supported only if @code{long double} type is available.
17886 As in @code{C}, @code{printf} supports simple backslash-escape
17887 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17888 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17889 single character. Octal and hexadecimal escape sequences are not
17892 Additionally, @code{printf} supports conversion specifications for DFP
17893 (@dfn{Decimal Floating Point}) types using the following length modifiers
17894 together with a floating point specifier.
17899 @samp{H} for printing @code{Decimal32} types.
17902 @samp{D} for printing @code{Decimal64} types.
17905 @samp{DD} for printing @code{Decimal128} types.
17908 If the underlying @code{C} implementation used to build @value{GDBN} has
17909 support for the three length modifiers for DFP types, other modifiers
17910 such as width and precision will also be available for @value{GDBN} to use.
17912 In case there is no such @code{C} support, no additional modifiers will be
17913 available and the value will be printed in the standard way.
17915 Here's an example of printing DFP types using the above conversion letters:
17917 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17923 @section Scripting @value{GDBN} using Python
17924 @cindex python scripting
17925 @cindex scripting with python
17927 You can script @value{GDBN} using the @uref{http://www.python.org/,
17928 Python programming language}. This feature is available only if
17929 @value{GDBN} was configured using @option{--with-python}.
17932 * Python Commands:: Accessing Python from @value{GDBN}.
17933 * Python API:: Accessing @value{GDBN} from Python.
17936 @node Python Commands
17937 @subsection Python Commands
17938 @cindex python commands
17939 @cindex commands to access python
17941 @value{GDBN} provides one command for accessing the Python interpreter,
17942 and one related setting:
17946 @item python @r{[}@var{code}@r{]}
17947 The @code{python} command can be used to evaluate Python code.
17949 If given an argument, the @code{python} command will evaluate the
17950 argument as a Python command. For example:
17953 (@value{GDBP}) python print 23
17957 If you do not provide an argument to @code{python}, it will act as a
17958 multi-line command, like @code{define}. In this case, the Python
17959 script is made up of subsequent command lines, given after the
17960 @code{python} command. This command list is terminated using a line
17961 containing @code{end}. For example:
17964 (@value{GDBP}) python
17966 End with a line saying just "end".
17972 @kindex maint set python print-stack
17973 @item maint set python print-stack
17974 By default, @value{GDBN} will print a stack trace when an error occurs
17975 in a Python script. This can be controlled using @code{maint set
17976 python print-stack}: if @code{on}, the default, then Python stack
17977 printing is enabled; if @code{off}, then Python stack printing is
17982 @subsection Python API
17984 @cindex programming in python
17986 @cindex python stdout
17987 @cindex python pagination
17988 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
17989 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
17990 A Python program which outputs to one of these streams may have its
17991 output interrupted by the user (@pxref{Screen Size}). In this
17992 situation, a Python @code{KeyboardInterrupt} exception is thrown.
17995 * Basic Python:: Basic Python Functions.
17996 * Exception Handling::
17997 * Values From Inferior::
18001 @subsubsection Basic Python
18003 @cindex python functions
18004 @cindex python module
18006 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18007 methods and classes added by @value{GDBN} are placed in this module.
18008 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18009 use in all scripts evaluated by the @code{python} command.
18011 @findex gdb.execute
18012 @defun execute command
18013 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18014 If a GDB exception happens while @var{command} runs, it is
18015 translated as described in @ref{Exception Handling,,Exception Handling}.
18016 If no exceptions occur, this function returns @code{None}.
18019 @findex gdb.get_parameter
18020 @defun get_parameter parameter
18021 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18022 string naming the parameter to look up; @var{parameter} may contain
18023 spaces if the parameter has a multi-part name. For example,
18024 @samp{print object} is a valid parameter name.
18026 If the named parameter does not exist, this function throws a
18027 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18028 a Python value of the appropriate type, and returned.
18032 @defun write string
18033 Print a string to @value{GDBN}'s paginated standard output stream.
18034 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18035 call this function.
18040 Flush @value{GDBN}'s paginated standard output stream. Flushing
18041 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18045 @node Exception Handling
18046 @subsubsection Exception Handling
18047 @cindex python exceptions
18048 @cindex exceptions, python
18050 When executing the @code{python} command, Python exceptions
18051 uncaught within the Python code are translated to calls to
18052 @value{GDBN} error-reporting mechanism. If the command that called
18053 @code{python} does not handle the error, @value{GDBN} will
18054 terminate it and print an error message containing the Python
18055 exception name, the associated value, and the Python call stack
18056 backtrace at the point where the exception was raised. Example:
18059 (@value{GDBP}) python print foo
18060 Traceback (most recent call last):
18061 File "<string>", line 1, in <module>
18062 NameError: name 'foo' is not defined
18065 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18066 code are converted to Python @code{RuntimeError} exceptions. User
18067 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18068 prompt) is translated to a Python @code{KeyboardInterrupt}
18069 exception. If you catch these exceptions in your Python code, your
18070 exception handler will see @code{RuntimeError} or
18071 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18072 message as its value, and the Python call stack backtrace at the
18073 Python statement closest to where the @value{GDBN} error occured as the
18076 @node Values From Inferior
18077 @subsubsection Values From Inferior
18078 @cindex values from inferior, with Python
18079 @cindex python, working with values from inferior
18081 @cindex @code{gdb.Value}
18082 @value{GDBN} provides values it obtains from the inferior program in
18083 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18084 for its internal bookkeeping of the inferior's values, and for
18085 fetching values when necessary.
18087 Inferior values that are simple scalars can be used directly in
18088 Python expressions that are valid for the value's data type. Here's
18089 an example for an integer or floating-point value @code{some_val}:
18096 As result of this, @code{bar} will also be a @code{gdb.Value} object
18097 whose values are of the same type as those of @code{some_val}.
18099 Inferior values that are structures or instances of some class can
18100 be accessed using the Python @dfn{dictionary syntax}. For example, if
18101 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18102 can access its @code{foo} element with:
18105 bar = some_val['foo']
18108 Again, @code{bar} will also be a @code{gdb.Value} object.
18110 For pointer data types, @code{gdb.Value} provides a method for
18111 dereferencing the pointer to obtain the object it points to.
18113 @defmethod Value dereference
18114 This method returns a new @code{gdb.Value} object whose contents is
18115 the object pointed to by the pointer. For example, if @code{foo} is
18116 a C pointer to an @code{int}, declared in your C program as
18123 then you can use the corresponding @code{gdb.Value} to access what
18124 @code{foo} points to like this:
18127 bar = foo.dereference ()
18130 The result @code{bar} will be a @code{gdb.Value} object holding the
18131 value pointed to by @code{foo}.
18135 @chapter Command Interpreters
18136 @cindex command interpreters
18138 @value{GDBN} supports multiple command interpreters, and some command
18139 infrastructure to allow users or user interface writers to switch
18140 between interpreters or run commands in other interpreters.
18142 @value{GDBN} currently supports two command interpreters, the console
18143 interpreter (sometimes called the command-line interpreter or @sc{cli})
18144 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18145 describes both of these interfaces in great detail.
18147 By default, @value{GDBN} will start with the console interpreter.
18148 However, the user may choose to start @value{GDBN} with another
18149 interpreter by specifying the @option{-i} or @option{--interpreter}
18150 startup options. Defined interpreters include:
18154 @cindex console interpreter
18155 The traditional console or command-line interpreter. This is the most often
18156 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18157 @value{GDBN} will use this interpreter.
18160 @cindex mi interpreter
18161 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18162 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18163 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18167 @cindex mi2 interpreter
18168 The current @sc{gdb/mi} interface.
18171 @cindex mi1 interpreter
18172 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18176 @cindex invoke another interpreter
18177 The interpreter being used by @value{GDBN} may not be dynamically
18178 switched at runtime. Although possible, this could lead to a very
18179 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18180 enters the command "interpreter-set console" in a console view,
18181 @value{GDBN} would switch to using the console interpreter, rendering
18182 the IDE inoperable!
18184 @kindex interpreter-exec
18185 Although you may only choose a single interpreter at startup, you may execute
18186 commands in any interpreter from the current interpreter using the appropriate
18187 command. If you are running the console interpreter, simply use the
18188 @code{interpreter-exec} command:
18191 interpreter-exec mi "-data-list-register-names"
18194 @sc{gdb/mi} has a similar command, although it is only available in versions of
18195 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18198 @chapter @value{GDBN} Text User Interface
18200 @cindex Text User Interface
18203 * TUI Overview:: TUI overview
18204 * TUI Keys:: TUI key bindings
18205 * TUI Single Key Mode:: TUI single key mode
18206 * TUI Commands:: TUI-specific commands
18207 * TUI Configuration:: TUI configuration variables
18210 The @value{GDBN} Text User Interface (TUI) is a terminal
18211 interface which uses the @code{curses} library to show the source
18212 file, the assembly output, the program registers and @value{GDBN}
18213 commands in separate text windows. The TUI mode is supported only
18214 on platforms where a suitable version of the @code{curses} library
18217 @pindex @value{GDBTUI}
18218 The TUI mode is enabled by default when you invoke @value{GDBN} as
18219 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18220 You can also switch in and out of TUI mode while @value{GDBN} runs by
18221 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18222 @xref{TUI Keys, ,TUI Key Bindings}.
18225 @section TUI Overview
18227 In TUI mode, @value{GDBN} can display several text windows:
18231 This window is the @value{GDBN} command window with the @value{GDBN}
18232 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18233 managed using readline.
18236 The source window shows the source file of the program. The current
18237 line and active breakpoints are displayed in this window.
18240 The assembly window shows the disassembly output of the program.
18243 This window shows the processor registers. Registers are highlighted
18244 when their values change.
18247 The source and assembly windows show the current program position
18248 by highlighting the current line and marking it with a @samp{>} marker.
18249 Breakpoints are indicated with two markers. The first marker
18250 indicates the breakpoint type:
18254 Breakpoint which was hit at least once.
18257 Breakpoint which was never hit.
18260 Hardware breakpoint which was hit at least once.
18263 Hardware breakpoint which was never hit.
18266 The second marker indicates whether the breakpoint is enabled or not:
18270 Breakpoint is enabled.
18273 Breakpoint is disabled.
18276 The source, assembly and register windows are updated when the current
18277 thread changes, when the frame changes, or when the program counter
18280 These windows are not all visible at the same time. The command
18281 window is always visible. The others can be arranged in several
18292 source and assembly,
18295 source and registers, or
18298 assembly and registers.
18301 A status line above the command window shows the following information:
18305 Indicates the current @value{GDBN} target.
18306 (@pxref{Targets, ,Specifying a Debugging Target}).
18309 Gives the current process or thread number.
18310 When no process is being debugged, this field is set to @code{No process}.
18313 Gives the current function name for the selected frame.
18314 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18315 When there is no symbol corresponding to the current program counter,
18316 the string @code{??} is displayed.
18319 Indicates the current line number for the selected frame.
18320 When the current line number is not known, the string @code{??} is displayed.
18323 Indicates the current program counter address.
18327 @section TUI Key Bindings
18328 @cindex TUI key bindings
18330 The TUI installs several key bindings in the readline keymaps
18331 (@pxref{Command Line Editing}). The following key bindings
18332 are installed for both TUI mode and the @value{GDBN} standard mode.
18341 Enter or leave the TUI mode. When leaving the TUI mode,
18342 the curses window management stops and @value{GDBN} operates using
18343 its standard mode, writing on the terminal directly. When reentering
18344 the TUI mode, control is given back to the curses windows.
18345 The screen is then refreshed.
18349 Use a TUI layout with only one window. The layout will
18350 either be @samp{source} or @samp{assembly}. When the TUI mode
18351 is not active, it will switch to the TUI mode.
18353 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18357 Use a TUI layout with at least two windows. When the current
18358 layout already has two windows, the next layout with two windows is used.
18359 When a new layout is chosen, one window will always be common to the
18360 previous layout and the new one.
18362 Think of it as the Emacs @kbd{C-x 2} binding.
18366 Change the active window. The TUI associates several key bindings
18367 (like scrolling and arrow keys) with the active window. This command
18368 gives the focus to the next TUI window.
18370 Think of it as the Emacs @kbd{C-x o} binding.
18374 Switch in and out of the TUI SingleKey mode that binds single
18375 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18378 The following key bindings only work in the TUI mode:
18383 Scroll the active window one page up.
18387 Scroll the active window one page down.
18391 Scroll the active window one line up.
18395 Scroll the active window one line down.
18399 Scroll the active window one column left.
18403 Scroll the active window one column right.
18407 Refresh the screen.
18410 Because the arrow keys scroll the active window in the TUI mode, they
18411 are not available for their normal use by readline unless the command
18412 window has the focus. When another window is active, you must use
18413 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18414 and @kbd{C-f} to control the command window.
18416 @node TUI Single Key Mode
18417 @section TUI Single Key Mode
18418 @cindex TUI single key mode
18420 The TUI also provides a @dfn{SingleKey} mode, which binds several
18421 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18422 switch into this mode, where the following key bindings are used:
18425 @kindex c @r{(SingleKey TUI key)}
18429 @kindex d @r{(SingleKey TUI key)}
18433 @kindex f @r{(SingleKey TUI key)}
18437 @kindex n @r{(SingleKey TUI key)}
18441 @kindex q @r{(SingleKey TUI key)}
18443 exit the SingleKey mode.
18445 @kindex r @r{(SingleKey TUI key)}
18449 @kindex s @r{(SingleKey TUI key)}
18453 @kindex u @r{(SingleKey TUI key)}
18457 @kindex v @r{(SingleKey TUI key)}
18461 @kindex w @r{(SingleKey TUI key)}
18466 Other keys temporarily switch to the @value{GDBN} command prompt.
18467 The key that was pressed is inserted in the editing buffer so that
18468 it is possible to type most @value{GDBN} commands without interaction
18469 with the TUI SingleKey mode. Once the command is entered the TUI
18470 SingleKey mode is restored. The only way to permanently leave
18471 this mode is by typing @kbd{q} or @kbd{C-x s}.
18475 @section TUI-specific Commands
18476 @cindex TUI commands
18478 The TUI has specific commands to control the text windows.
18479 These commands are always available, even when @value{GDBN} is not in
18480 the TUI mode. When @value{GDBN} is in the standard mode, most
18481 of these commands will automatically switch to the TUI mode.
18486 List and give the size of all displayed windows.
18490 Display the next layout.
18493 Display the previous layout.
18496 Display the source window only.
18499 Display the assembly window only.
18502 Display the source and assembly window.
18505 Display the register window together with the source or assembly window.
18509 Make the next window active for scrolling.
18512 Make the previous window active for scrolling.
18515 Make the source window active for scrolling.
18518 Make the assembly window active for scrolling.
18521 Make the register window active for scrolling.
18524 Make the command window active for scrolling.
18528 Refresh the screen. This is similar to typing @kbd{C-L}.
18530 @item tui reg float
18532 Show the floating point registers in the register window.
18534 @item tui reg general
18535 Show the general registers in the register window.
18538 Show the next register group. The list of register groups as well as
18539 their order is target specific. The predefined register groups are the
18540 following: @code{general}, @code{float}, @code{system}, @code{vector},
18541 @code{all}, @code{save}, @code{restore}.
18543 @item tui reg system
18544 Show the system registers in the register window.
18548 Update the source window and the current execution point.
18550 @item winheight @var{name} +@var{count}
18551 @itemx winheight @var{name} -@var{count}
18553 Change the height of the window @var{name} by @var{count}
18554 lines. Positive counts increase the height, while negative counts
18557 @item tabset @var{nchars}
18559 Set the width of tab stops to be @var{nchars} characters.
18562 @node TUI Configuration
18563 @section TUI Configuration Variables
18564 @cindex TUI configuration variables
18566 Several configuration variables control the appearance of TUI windows.
18569 @item set tui border-kind @var{kind}
18570 @kindex set tui border-kind
18571 Select the border appearance for the source, assembly and register windows.
18572 The possible values are the following:
18575 Use a space character to draw the border.
18578 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18581 Use the Alternate Character Set to draw the border. The border is
18582 drawn using character line graphics if the terminal supports them.
18585 @item set tui border-mode @var{mode}
18586 @kindex set tui border-mode
18587 @itemx set tui active-border-mode @var{mode}
18588 @kindex set tui active-border-mode
18589 Select the display attributes for the borders of the inactive windows
18590 or the active window. The @var{mode} can be one of the following:
18593 Use normal attributes to display the border.
18599 Use reverse video mode.
18602 Use half bright mode.
18604 @item half-standout
18605 Use half bright and standout mode.
18608 Use extra bright or bold mode.
18610 @item bold-standout
18611 Use extra bright or bold and standout mode.
18616 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18619 @cindex @sc{gnu} Emacs
18620 A special interface allows you to use @sc{gnu} Emacs to view (and
18621 edit) the source files for the program you are debugging with
18624 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18625 executable file you want to debug as an argument. This command starts
18626 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18627 created Emacs buffer.
18628 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18630 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18635 All ``terminal'' input and output goes through an Emacs buffer, called
18638 This applies both to @value{GDBN} commands and their output, and to the input
18639 and output done by the program you are debugging.
18641 This is useful because it means that you can copy the text of previous
18642 commands and input them again; you can even use parts of the output
18645 All the facilities of Emacs' Shell mode are available for interacting
18646 with your program. In particular, you can send signals the usual
18647 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18651 @value{GDBN} displays source code through Emacs.
18653 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18654 source file for that frame and puts an arrow (@samp{=>}) at the
18655 left margin of the current line. Emacs uses a separate buffer for
18656 source display, and splits the screen to show both your @value{GDBN} session
18659 Explicit @value{GDBN} @code{list} or search commands still produce output as
18660 usual, but you probably have no reason to use them from Emacs.
18663 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18664 a graphical mode, enabled by default, which provides further buffers
18665 that can control the execution and describe the state of your program.
18666 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18668 If you specify an absolute file name when prompted for the @kbd{M-x
18669 gdb} argument, then Emacs sets your current working directory to where
18670 your program resides. If you only specify the file name, then Emacs
18671 sets your current working directory to to the directory associated
18672 with the previous buffer. In this case, @value{GDBN} may find your
18673 program by searching your environment's @code{PATH} variable, but on
18674 some operating systems it might not find the source. So, although the
18675 @value{GDBN} input and output session proceeds normally, the auxiliary
18676 buffer does not display the current source and line of execution.
18678 The initial working directory of @value{GDBN} is printed on the top
18679 line of the GUD buffer and this serves as a default for the commands
18680 that specify files for @value{GDBN} to operate on. @xref{Files,
18681 ,Commands to Specify Files}.
18683 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18684 need to call @value{GDBN} by a different name (for example, if you
18685 keep several configurations around, with different names) you can
18686 customize the Emacs variable @code{gud-gdb-command-name} to run the
18689 In the GUD buffer, you can use these special Emacs commands in
18690 addition to the standard Shell mode commands:
18694 Describe the features of Emacs' GUD Mode.
18697 Execute to another source line, like the @value{GDBN} @code{step} command; also
18698 update the display window to show the current file and location.
18701 Execute to next source line in this function, skipping all function
18702 calls, like the @value{GDBN} @code{next} command. Then update the display window
18703 to show the current file and location.
18706 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18707 display window accordingly.
18710 Execute until exit from the selected stack frame, like the @value{GDBN}
18711 @code{finish} command.
18714 Continue execution of your program, like the @value{GDBN} @code{continue}
18718 Go up the number of frames indicated by the numeric argument
18719 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18720 like the @value{GDBN} @code{up} command.
18723 Go down the number of frames indicated by the numeric argument, like the
18724 @value{GDBN} @code{down} command.
18727 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18728 tells @value{GDBN} to set a breakpoint on the source line point is on.
18730 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18731 separate frame which shows a backtrace when the GUD buffer is current.
18732 Move point to any frame in the stack and type @key{RET} to make it
18733 become the current frame and display the associated source in the
18734 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18735 selected frame become the current one. In graphical mode, the
18736 speedbar displays watch expressions.
18738 If you accidentally delete the source-display buffer, an easy way to get
18739 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18740 request a frame display; when you run under Emacs, this recreates
18741 the source buffer if necessary to show you the context of the current
18744 The source files displayed in Emacs are in ordinary Emacs buffers
18745 which are visiting the source files in the usual way. You can edit
18746 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18747 communicates with Emacs in terms of line numbers. If you add or
18748 delete lines from the text, the line numbers that @value{GDBN} knows cease
18749 to correspond properly with the code.
18751 A more detailed description of Emacs' interaction with @value{GDBN} is
18752 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18755 @c The following dropped because Epoch is nonstandard. Reactivate
18756 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18758 @kindex Emacs Epoch environment
18762 Version 18 of @sc{gnu} Emacs has a built-in window system
18763 called the @code{epoch}
18764 environment. Users of this environment can use a new command,
18765 @code{inspect} which performs identically to @code{print} except that
18766 each value is printed in its own window.
18771 @chapter The @sc{gdb/mi} Interface
18773 @unnumberedsec Function and Purpose
18775 @cindex @sc{gdb/mi}, its purpose
18776 @sc{gdb/mi} is a line based machine oriented text interface to
18777 @value{GDBN} and is activated by specifying using the
18778 @option{--interpreter} command line option (@pxref{Mode Options}). It
18779 is specifically intended to support the development of systems which
18780 use the debugger as just one small component of a larger system.
18782 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18783 in the form of a reference manual.
18785 Note that @sc{gdb/mi} is still under construction, so some of the
18786 features described below are incomplete and subject to change
18787 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18789 @unnumberedsec Notation and Terminology
18791 @cindex notational conventions, for @sc{gdb/mi}
18792 This chapter uses the following notation:
18796 @code{|} separates two alternatives.
18799 @code{[ @var{something} ]} indicates that @var{something} is optional:
18800 it may or may not be given.
18803 @code{( @var{group} )*} means that @var{group} inside the parentheses
18804 may repeat zero or more times.
18807 @code{( @var{group} )+} means that @var{group} inside the parentheses
18808 may repeat one or more times.
18811 @code{"@var{string}"} means a literal @var{string}.
18815 @heading Dependencies
18819 * GDB/MI Command Syntax::
18820 * GDB/MI Compatibility with CLI::
18821 * GDB/MI Development and Front Ends::
18822 * GDB/MI Output Records::
18823 * GDB/MI Simple Examples::
18824 * GDB/MI Command Description Format::
18825 * GDB/MI Breakpoint Commands::
18826 * GDB/MI Program Context::
18827 * GDB/MI Thread Commands::
18828 * GDB/MI Program Execution::
18829 * GDB/MI Stack Manipulation::
18830 * GDB/MI Variable Objects::
18831 * GDB/MI Data Manipulation::
18832 * GDB/MI Tracepoint Commands::
18833 * GDB/MI Symbol Query::
18834 * GDB/MI File Commands::
18836 * GDB/MI Kod Commands::
18837 * GDB/MI Memory Overlay Commands::
18838 * GDB/MI Signal Handling Commands::
18840 * GDB/MI Target Manipulation::
18841 * GDB/MI File Transfer Commands::
18842 * GDB/MI Miscellaneous Commands::
18845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18846 @node GDB/MI Command Syntax
18847 @section @sc{gdb/mi} Command Syntax
18850 * GDB/MI Input Syntax::
18851 * GDB/MI Output Syntax::
18854 @node GDB/MI Input Syntax
18855 @subsection @sc{gdb/mi} Input Syntax
18857 @cindex input syntax for @sc{gdb/mi}
18858 @cindex @sc{gdb/mi}, input syntax
18860 @item @var{command} @expansion{}
18861 @code{@var{cli-command} | @var{mi-command}}
18863 @item @var{cli-command} @expansion{}
18864 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18865 @var{cli-command} is any existing @value{GDBN} CLI command.
18867 @item @var{mi-command} @expansion{}
18868 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18869 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18871 @item @var{token} @expansion{}
18872 "any sequence of digits"
18874 @item @var{option} @expansion{}
18875 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18877 @item @var{parameter} @expansion{}
18878 @code{@var{non-blank-sequence} | @var{c-string}}
18880 @item @var{operation} @expansion{}
18881 @emph{any of the operations described in this chapter}
18883 @item @var{non-blank-sequence} @expansion{}
18884 @emph{anything, provided it doesn't contain special characters such as
18885 "-", @var{nl}, """ and of course " "}
18887 @item @var{c-string} @expansion{}
18888 @code{""" @var{seven-bit-iso-c-string-content} """}
18890 @item @var{nl} @expansion{}
18899 The CLI commands are still handled by the @sc{mi} interpreter; their
18900 output is described below.
18903 The @code{@var{token}}, when present, is passed back when the command
18907 Some @sc{mi} commands accept optional arguments as part of the parameter
18908 list. Each option is identified by a leading @samp{-} (dash) and may be
18909 followed by an optional argument parameter. Options occur first in the
18910 parameter list and can be delimited from normal parameters using
18911 @samp{--} (this is useful when some parameters begin with a dash).
18918 We want easy access to the existing CLI syntax (for debugging).
18921 We want it to be easy to spot a @sc{mi} operation.
18924 @node GDB/MI Output Syntax
18925 @subsection @sc{gdb/mi} Output Syntax
18927 @cindex output syntax of @sc{gdb/mi}
18928 @cindex @sc{gdb/mi}, output syntax
18929 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18930 followed, optionally, by a single result record. This result record
18931 is for the most recent command. The sequence of output records is
18932 terminated by @samp{(gdb)}.
18934 If an input command was prefixed with a @code{@var{token}} then the
18935 corresponding output for that command will also be prefixed by that same
18939 @item @var{output} @expansion{}
18940 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18942 @item @var{result-record} @expansion{}
18943 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18945 @item @var{out-of-band-record} @expansion{}
18946 @code{@var{async-record} | @var{stream-record}}
18948 @item @var{async-record} @expansion{}
18949 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18951 @item @var{exec-async-output} @expansion{}
18952 @code{[ @var{token} ] "*" @var{async-output}}
18954 @item @var{status-async-output} @expansion{}
18955 @code{[ @var{token} ] "+" @var{async-output}}
18957 @item @var{notify-async-output} @expansion{}
18958 @code{[ @var{token} ] "=" @var{async-output}}
18960 @item @var{async-output} @expansion{}
18961 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18963 @item @var{result-class} @expansion{}
18964 @code{"done" | "running" | "connected" | "error" | "exit"}
18966 @item @var{async-class} @expansion{}
18967 @code{"stopped" | @var{others}} (where @var{others} will be added
18968 depending on the needs---this is still in development).
18970 @item @var{result} @expansion{}
18971 @code{ @var{variable} "=" @var{value}}
18973 @item @var{variable} @expansion{}
18974 @code{ @var{string} }
18976 @item @var{value} @expansion{}
18977 @code{ @var{const} | @var{tuple} | @var{list} }
18979 @item @var{const} @expansion{}
18980 @code{@var{c-string}}
18982 @item @var{tuple} @expansion{}
18983 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18985 @item @var{list} @expansion{}
18986 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18987 @var{result} ( "," @var{result} )* "]" }
18989 @item @var{stream-record} @expansion{}
18990 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18992 @item @var{console-stream-output} @expansion{}
18993 @code{"~" @var{c-string}}
18995 @item @var{target-stream-output} @expansion{}
18996 @code{"@@" @var{c-string}}
18998 @item @var{log-stream-output} @expansion{}
18999 @code{"&" @var{c-string}}
19001 @item @var{nl} @expansion{}
19004 @item @var{token} @expansion{}
19005 @emph{any sequence of digits}.
19013 All output sequences end in a single line containing a period.
19016 The @code{@var{token}} is from the corresponding request. Note that
19017 for all async output, while the token is allowed by the grammar and
19018 may be output by future versions of @value{GDBN} for select async
19019 output messages, it is generally omitted. Frontends should treat
19020 all async output as reporting general changes in the state of the
19021 target and there should be no need to associate async output to any
19025 @cindex status output in @sc{gdb/mi}
19026 @var{status-async-output} contains on-going status information about the
19027 progress of a slow operation. It can be discarded. All status output is
19028 prefixed by @samp{+}.
19031 @cindex async output in @sc{gdb/mi}
19032 @var{exec-async-output} contains asynchronous state change on the target
19033 (stopped, started, disappeared). All async output is prefixed by
19037 @cindex notify output in @sc{gdb/mi}
19038 @var{notify-async-output} contains supplementary information that the
19039 client should handle (e.g., a new breakpoint information). All notify
19040 output is prefixed by @samp{=}.
19043 @cindex console output in @sc{gdb/mi}
19044 @var{console-stream-output} is output that should be displayed as is in the
19045 console. It is the textual response to a CLI command. All the console
19046 output is prefixed by @samp{~}.
19049 @cindex target output in @sc{gdb/mi}
19050 @var{target-stream-output} is the output produced by the target program.
19051 All the target output is prefixed by @samp{@@}.
19054 @cindex log output in @sc{gdb/mi}
19055 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19056 instance messages that should be displayed as part of an error log. All
19057 the log output is prefixed by @samp{&}.
19060 @cindex list output in @sc{gdb/mi}
19061 New @sc{gdb/mi} commands should only output @var{lists} containing
19067 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19068 details about the various output records.
19070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19071 @node GDB/MI Compatibility with CLI
19072 @section @sc{gdb/mi} Compatibility with CLI
19074 @cindex compatibility, @sc{gdb/mi} and CLI
19075 @cindex @sc{gdb/mi}, compatibility with CLI
19077 For the developers convenience CLI commands can be entered directly,
19078 but there may be some unexpected behaviour. For example, commands
19079 that query the user will behave as if the user replied yes, breakpoint
19080 command lists are not executed and some CLI commands, such as
19081 @code{if}, @code{when} and @code{define}, prompt for further input with
19082 @samp{>}, which is not valid MI output.
19084 This feature may be removed at some stage in the future and it is
19085 recommended that front ends use the @code{-interpreter-exec} command
19086 (@pxref{-interpreter-exec}).
19088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19089 @node GDB/MI Development and Front Ends
19090 @section @sc{gdb/mi} Development and Front Ends
19091 @cindex @sc{gdb/mi} development
19093 The application which takes the MI output and presents the state of the
19094 program being debugged to the user is called a @dfn{front end}.
19096 Although @sc{gdb/mi} is still incomplete, it is currently being used
19097 by a variety of front ends to @value{GDBN}. This makes it difficult
19098 to introduce new functionality without breaking existing usage. This
19099 section tries to minimize the problems by describing how the protocol
19102 Some changes in MI need not break a carefully designed front end, and
19103 for these the MI version will remain unchanged. The following is a
19104 list of changes that may occur within one level, so front ends should
19105 parse MI output in a way that can handle them:
19109 New MI commands may be added.
19112 New fields may be added to the output of any MI command.
19115 The range of values for fields with specified values, e.g.,
19116 @code{in_scope} (@pxref{-var-update}) may be extended.
19118 @c The format of field's content e.g type prefix, may change so parse it
19119 @c at your own risk. Yes, in general?
19121 @c The order of fields may change? Shouldn't really matter but it might
19122 @c resolve inconsistencies.
19125 If the changes are likely to break front ends, the MI version level
19126 will be increased by one. This will allow the front end to parse the
19127 output according to the MI version. Apart from mi0, new versions of
19128 @value{GDBN} will not support old versions of MI and it will be the
19129 responsibility of the front end to work with the new one.
19131 @c Starting with mi3, add a new command -mi-version that prints the MI
19134 The best way to avoid unexpected changes in MI that might break your front
19135 end is to make your project known to @value{GDBN} developers and
19136 follow development on @email{gdb@@sourceware.org} and
19137 @email{gdb-patches@@sourceware.org}.
19138 @cindex mailing lists
19140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19141 @node GDB/MI Output Records
19142 @section @sc{gdb/mi} Output Records
19145 * GDB/MI Result Records::
19146 * GDB/MI Stream Records::
19147 * GDB/MI Async Records::
19150 @node GDB/MI Result Records
19151 @subsection @sc{gdb/mi} Result Records
19153 @cindex result records in @sc{gdb/mi}
19154 @cindex @sc{gdb/mi}, result records
19155 In addition to a number of out-of-band notifications, the response to a
19156 @sc{gdb/mi} command includes one of the following result indications:
19160 @item "^done" [ "," @var{results} ]
19161 The synchronous operation was successful, @code{@var{results}} are the return
19166 @c Is this one correct? Should it be an out-of-band notification?
19167 The asynchronous operation was successfully started. The target is
19172 @value{GDBN} has connected to a remote target.
19174 @item "^error" "," @var{c-string}
19176 The operation failed. The @code{@var{c-string}} contains the corresponding
19181 @value{GDBN} has terminated.
19185 @node GDB/MI Stream Records
19186 @subsection @sc{gdb/mi} Stream Records
19188 @cindex @sc{gdb/mi}, stream records
19189 @cindex stream records in @sc{gdb/mi}
19190 @value{GDBN} internally maintains a number of output streams: the console, the
19191 target, and the log. The output intended for each of these streams is
19192 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19194 Each stream record begins with a unique @dfn{prefix character} which
19195 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19196 Syntax}). In addition to the prefix, each stream record contains a
19197 @code{@var{string-output}}. This is either raw text (with an implicit new
19198 line) or a quoted C string (which does not contain an implicit newline).
19201 @item "~" @var{string-output}
19202 The console output stream contains text that should be displayed in the
19203 CLI console window. It contains the textual responses to CLI commands.
19205 @item "@@" @var{string-output}
19206 The target output stream contains any textual output from the running
19207 target. This is only present when GDB's event loop is truly
19208 asynchronous, which is currently only the case for remote targets.
19210 @item "&" @var{string-output}
19211 The log stream contains debugging messages being produced by @value{GDBN}'s
19215 @node GDB/MI Async Records
19216 @subsection @sc{gdb/mi} Async Records
19218 @cindex async records in @sc{gdb/mi}
19219 @cindex @sc{gdb/mi}, async records
19220 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19221 additional changes that have occurred. Those changes can either be a
19222 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19223 target activity (e.g., target stopped).
19225 The following is the list of possible async records:
19229 @item *running,thread-id="@var{thread}"
19230 The target is now running. The @var{thread} field tells which
19231 specific thread is now running, and can be @samp{all} if all threads
19232 are running. The frontend should assume that no interaction with a
19233 running thread is possible after this notification is produced.
19234 The frontend should not assume that this notification is output
19235 only once for any command. @value{GDBN} may emit this notification
19236 several times, either for different threads, because it cannot resume
19237 all threads together, or even for a single thread, if the thread must
19238 be stepped though some code before letting it run freely.
19240 @item *stopped,reason="@var{reason}"
19241 The target has stopped. The @var{reason} field can have one of the
19245 @item breakpoint-hit
19246 A breakpoint was reached.
19247 @item watchpoint-trigger
19248 A watchpoint was triggered.
19249 @item read-watchpoint-trigger
19250 A read watchpoint was triggered.
19251 @item access-watchpoint-trigger
19252 An access watchpoint was triggered.
19253 @item function-finished
19254 An -exec-finish or similar CLI command was accomplished.
19255 @item location-reached
19256 An -exec-until or similar CLI command was accomplished.
19257 @item watchpoint-scope
19258 A watchpoint has gone out of scope.
19259 @item end-stepping-range
19260 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19261 similar CLI command was accomplished.
19262 @item exited-signalled
19263 The inferior exited because of a signal.
19265 The inferior exited.
19266 @item exited-normally
19267 The inferior exited normally.
19268 @item signal-received
19269 A signal was received by the inferior.
19272 @item =thread-created,id="@var{id}"
19273 @itemx =thread-exited,id="@var{id}"
19274 A thread either was created, or has exited. The @var{id} field
19275 contains the @value{GDBN} identifier of the thread.
19280 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19281 @node GDB/MI Simple Examples
19282 @section Simple Examples of @sc{gdb/mi} Interaction
19283 @cindex @sc{gdb/mi}, simple examples
19285 This subsection presents several simple examples of interaction using
19286 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
19287 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
19288 the output received from @sc{gdb/mi}.
19290 Note the line breaks shown in the examples are here only for
19291 readability, they don't appear in the real output.
19293 @subheading Setting a Breakpoint
19295 Setting a breakpoint generates synchronous output which contains detailed
19296 information of the breakpoint.
19299 -> -break-insert main
19300 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19301 enabled="y",addr="0x08048564",func="main",file="myprog.c",
19302 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
19306 @subheading Program Execution
19308 Program execution generates asynchronous records and MI gives the
19309 reason that execution stopped.
19315 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
19316 frame=@{addr="0x08048564",func="main",
19317 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
19318 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
19323 <- *stopped,reason="exited-normally"
19327 @subheading Quitting @value{GDBN}
19329 Quitting @value{GDBN} just prints the result class @samp{^exit}.
19337 @subheading A Bad Command
19339 Here's what happens if you pass a non-existent command:
19343 <- ^error,msg="Undefined MI command: rubbish"
19348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19349 @node GDB/MI Command Description Format
19350 @section @sc{gdb/mi} Command Description Format
19352 The remaining sections describe blocks of commands. Each block of
19353 commands is laid out in a fashion similar to this section.
19355 @subheading Motivation
19357 The motivation for this collection of commands.
19359 @subheading Introduction
19361 A brief introduction to this collection of commands as a whole.
19363 @subheading Commands
19365 For each command in the block, the following is described:
19367 @subsubheading Synopsis
19370 -command @var{args}@dots{}
19373 @subsubheading Result
19375 @subsubheading @value{GDBN} Command
19377 The corresponding @value{GDBN} CLI command(s), if any.
19379 @subsubheading Example
19381 Example(s) formatted for readability. Some of the described commands have
19382 not been implemented yet and these are labeled N.A.@: (not available).
19385 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19386 @node GDB/MI Breakpoint Commands
19387 @section @sc{gdb/mi} Breakpoint Commands
19389 @cindex breakpoint commands for @sc{gdb/mi}
19390 @cindex @sc{gdb/mi}, breakpoint commands
19391 This section documents @sc{gdb/mi} commands for manipulating
19394 @subheading The @code{-break-after} Command
19395 @findex -break-after
19397 @subsubheading Synopsis
19400 -break-after @var{number} @var{count}
19403 The breakpoint number @var{number} is not in effect until it has been
19404 hit @var{count} times. To see how this is reflected in the output of
19405 the @samp{-break-list} command, see the description of the
19406 @samp{-break-list} command below.
19408 @subsubheading @value{GDBN} Command
19410 The corresponding @value{GDBN} command is @samp{ignore}.
19412 @subsubheading Example
19417 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19418 enabled="y",addr="0x000100d0",func="main",file="hello.c",
19419 fullname="/home/foo/hello.c",line="5",times="0"@}
19426 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19427 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19428 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19429 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19430 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19431 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19432 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19433 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19434 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19435 line="5",times="0",ignore="3"@}]@}
19440 @subheading The @code{-break-catch} Command
19441 @findex -break-catch
19443 @subheading The @code{-break-commands} Command
19444 @findex -break-commands
19448 @subheading The @code{-break-condition} Command
19449 @findex -break-condition
19451 @subsubheading Synopsis
19454 -break-condition @var{number} @var{expr}
19457 Breakpoint @var{number} will stop the program only if the condition in
19458 @var{expr} is true. The condition becomes part of the
19459 @samp{-break-list} output (see the description of the @samp{-break-list}
19462 @subsubheading @value{GDBN} Command
19464 The corresponding @value{GDBN} command is @samp{condition}.
19466 @subsubheading Example
19470 -break-condition 1 1
19474 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19482 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19483 line="5",cond="1",times="0",ignore="3"@}]@}
19487 @subheading The @code{-break-delete} Command
19488 @findex -break-delete
19490 @subsubheading Synopsis
19493 -break-delete ( @var{breakpoint} )+
19496 Delete the breakpoint(s) whose number(s) are specified in the argument
19497 list. This is obviously reflected in the breakpoint list.
19499 @subsubheading @value{GDBN} Command
19501 The corresponding @value{GDBN} command is @samp{delete}.
19503 @subsubheading Example
19511 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19512 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19513 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19514 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19515 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19516 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19517 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19522 @subheading The @code{-break-disable} Command
19523 @findex -break-disable
19525 @subsubheading Synopsis
19528 -break-disable ( @var{breakpoint} )+
19531 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19532 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19534 @subsubheading @value{GDBN} Command
19536 The corresponding @value{GDBN} command is @samp{disable}.
19538 @subsubheading Example
19546 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19547 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19548 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19549 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19550 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19551 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19552 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19553 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19554 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19555 line="5",times="0"@}]@}
19559 @subheading The @code{-break-enable} Command
19560 @findex -break-enable
19562 @subsubheading Synopsis
19565 -break-enable ( @var{breakpoint} )+
19568 Enable (previously disabled) @var{breakpoint}(s).
19570 @subsubheading @value{GDBN} Command
19572 The corresponding @value{GDBN} command is @samp{enable}.
19574 @subsubheading Example
19582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19589 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19591 line="5",times="0"@}]@}
19595 @subheading The @code{-break-info} Command
19596 @findex -break-info
19598 @subsubheading Synopsis
19601 -break-info @var{breakpoint}
19605 Get information about a single breakpoint.
19607 @subsubheading @value{GDBN} Command
19609 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19611 @subsubheading Example
19614 @subheading The @code{-break-insert} Command
19615 @findex -break-insert
19617 @subsubheading Synopsis
19620 -break-insert [ -t ] [ -h ] [ -f ]
19621 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19622 [ -p @var{thread} ] [ @var{location} ]
19626 If specified, @var{location}, can be one of:
19633 @item filename:linenum
19634 @item filename:function
19638 The possible optional parameters of this command are:
19642 Insert a temporary breakpoint.
19644 Insert a hardware breakpoint.
19645 @item -c @var{condition}
19646 Make the breakpoint conditional on @var{condition}.
19647 @item -i @var{ignore-count}
19648 Initialize the @var{ignore-count}.
19650 If @var{location} cannot be parsed (for example if it
19651 refers to unknown files or functions), create a pending
19652 breakpoint. Without this flag, @value{GDBN} will report
19653 an error, and won't create a breakpoint, if @var{location}
19657 @subsubheading Result
19659 The result is in the form:
19662 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19663 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19664 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19665 times="@var{times}"@}
19669 where @var{number} is the @value{GDBN} number for this breakpoint,
19670 @var{funcname} is the name of the function where the breakpoint was
19671 inserted, @var{filename} is the name of the source file which contains
19672 this function, @var{lineno} is the source line number within that file
19673 and @var{times} the number of times that the breakpoint has been hit
19674 (always 0 for -break-insert but may be greater for -break-info or -break-list
19675 which use the same output).
19677 Note: this format is open to change.
19678 @c An out-of-band breakpoint instead of part of the result?
19680 @subsubheading @value{GDBN} Command
19682 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19683 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19685 @subsubheading Example
19690 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19691 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19693 -break-insert -t foo
19694 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19695 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19698 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19699 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19700 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19701 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19702 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19703 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19704 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19705 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19706 addr="0x0001072c", func="main",file="recursive2.c",
19707 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
19708 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
19709 addr="0x00010774",func="foo",file="recursive2.c",
19710 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
19712 -break-insert -r foo.*
19713 ~int foo(int, int);
19714 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
19715 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
19719 @subheading The @code{-break-list} Command
19720 @findex -break-list
19722 @subsubheading Synopsis
19728 Displays the list of inserted breakpoints, showing the following fields:
19732 number of the breakpoint
19734 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
19736 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
19739 is the breakpoint enabled or no: @samp{y} or @samp{n}
19741 memory location at which the breakpoint is set
19743 logical location of the breakpoint, expressed by function name, file
19746 number of times the breakpoint has been hit
19749 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
19750 @code{body} field is an empty list.
19752 @subsubheading @value{GDBN} Command
19754 The corresponding @value{GDBN} command is @samp{info break}.
19756 @subsubheading Example
19761 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19768 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19769 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
19770 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19771 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
19772 line="13",times="0"@}]@}
19776 Here's an example of the result when there are no breakpoints:
19781 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19782 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19783 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19784 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19785 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19786 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19787 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19792 @subheading The @code{-break-watch} Command
19793 @findex -break-watch
19795 @subsubheading Synopsis
19798 -break-watch [ -a | -r ]
19801 Create a watchpoint. With the @samp{-a} option it will create an
19802 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
19803 read from or on a write to the memory location. With the @samp{-r}
19804 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
19805 trigger only when the memory location is accessed for reading. Without
19806 either of the options, the watchpoint created is a regular watchpoint,
19807 i.e., it will trigger when the memory location is accessed for writing.
19808 @xref{Set Watchpoints, , Setting Watchpoints}.
19810 Note that @samp{-break-list} will report a single list of watchpoints and
19811 breakpoints inserted.
19813 @subsubheading @value{GDBN} Command
19815 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
19818 @subsubheading Example
19820 Setting a watchpoint on a variable in the @code{main} function:
19825 ^done,wpt=@{number="2",exp="x"@}
19830 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19831 value=@{old="-268439212",new="55"@},
19832 frame=@{func="main",args=[],file="recursive2.c",
19833 fullname="/home/foo/bar/recursive2.c",line="5"@}
19837 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19838 the program execution twice: first for the variable changing value, then
19839 for the watchpoint going out of scope.
19844 ^done,wpt=@{number="5",exp="C"@}
19849 *stopped,reason="watchpoint-trigger",
19850 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19851 frame=@{func="callee4",args=[],
19852 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19853 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19858 *stopped,reason="watchpoint-scope",wpnum="5",
19859 frame=@{func="callee3",args=[@{name="strarg",
19860 value="0x11940 \"A string argument.\""@}],
19861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19866 Listing breakpoints and watchpoints, at different points in the program
19867 execution. Note that once the watchpoint goes out of scope, it is
19873 ^done,wpt=@{number="2",exp="C"@}
19876 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19877 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19878 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19879 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19880 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19881 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19882 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19883 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19884 addr="0x00010734",func="callee4",
19885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19886 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19887 bkpt=@{number="2",type="watchpoint",disp="keep",
19888 enabled="y",addr="",what="C",times="0"@}]@}
19893 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19894 value=@{old="-276895068",new="3"@},
19895 frame=@{func="callee4",args=[],
19896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19897 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19900 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19901 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19902 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19903 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19904 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19905 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19906 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19907 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19908 addr="0x00010734",func="callee4",
19909 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19910 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19911 bkpt=@{number="2",type="watchpoint",disp="keep",
19912 enabled="y",addr="",what="C",times="-5"@}]@}
19916 ^done,reason="watchpoint-scope",wpnum="2",
19917 frame=@{func="callee3",args=[@{name="strarg",
19918 value="0x11940 \"A string argument.\""@}],
19919 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19920 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19923 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19924 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19925 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19926 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19927 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19928 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19929 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19930 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19931 addr="0x00010734",func="callee4",
19932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19933 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19938 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19939 @node GDB/MI Program Context
19940 @section @sc{gdb/mi} Program Context
19942 @subheading The @code{-exec-arguments} Command
19943 @findex -exec-arguments
19946 @subsubheading Synopsis
19949 -exec-arguments @var{args}
19952 Set the inferior program arguments, to be used in the next
19955 @subsubheading @value{GDBN} Command
19957 The corresponding @value{GDBN} command is @samp{set args}.
19959 @subsubheading Example
19963 -exec-arguments -v word
19969 @subheading The @code{-exec-show-arguments} Command
19970 @findex -exec-show-arguments
19972 @subsubheading Synopsis
19975 -exec-show-arguments
19978 Print the arguments of the program.
19980 @subsubheading @value{GDBN} Command
19982 The corresponding @value{GDBN} command is @samp{show args}.
19984 @subsubheading Example
19988 @subheading The @code{-environment-cd} Command
19989 @findex -environment-cd
19991 @subsubheading Synopsis
19994 -environment-cd @var{pathdir}
19997 Set @value{GDBN}'s working directory.
19999 @subsubheading @value{GDBN} Command
20001 The corresponding @value{GDBN} command is @samp{cd}.
20003 @subsubheading Example
20007 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20013 @subheading The @code{-environment-directory} Command
20014 @findex -environment-directory
20016 @subsubheading Synopsis
20019 -environment-directory [ -r ] [ @var{pathdir} ]+
20022 Add directories @var{pathdir} to beginning of search path for source files.
20023 If the @samp{-r} option is used, the search path is reset to the default
20024 search path. If directories @var{pathdir} are supplied in addition to the
20025 @samp{-r} option, the search path is first reset and then addition
20027 Multiple directories may be specified, separated by blanks. Specifying
20028 multiple directories in a single command
20029 results in the directories added to the beginning of the
20030 search path in the same order they were presented in the command.
20031 If blanks are needed as
20032 part of a directory name, double-quotes should be used around
20033 the name. In the command output, the path will show up separated
20034 by the system directory-separator character. The directory-separator
20035 character must not be used
20036 in any directory name.
20037 If no directories are specified, the current search path is displayed.
20039 @subsubheading @value{GDBN} Command
20041 The corresponding @value{GDBN} command is @samp{dir}.
20043 @subsubheading Example
20047 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20048 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20050 -environment-directory ""
20051 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20053 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20054 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20056 -environment-directory -r
20057 ^done,source-path="$cdir:$cwd"
20062 @subheading The @code{-environment-path} Command
20063 @findex -environment-path
20065 @subsubheading Synopsis
20068 -environment-path [ -r ] [ @var{pathdir} ]+
20071 Add directories @var{pathdir} to beginning of search path for object files.
20072 If the @samp{-r} option is used, the search path is reset to the original
20073 search path that existed at gdb start-up. If directories @var{pathdir} are
20074 supplied in addition to the
20075 @samp{-r} option, the search path is first reset and then addition
20077 Multiple directories may be specified, separated by blanks. Specifying
20078 multiple directories in a single command
20079 results in the directories added to the beginning of the
20080 search path in the same order they were presented in the command.
20081 If blanks are needed as
20082 part of a directory name, double-quotes should be used around
20083 the name. In the command output, the path will show up separated
20084 by the system directory-separator character. The directory-separator
20085 character must not be used
20086 in any directory name.
20087 If no directories are specified, the current path is displayed.
20090 @subsubheading @value{GDBN} Command
20092 The corresponding @value{GDBN} command is @samp{path}.
20094 @subsubheading Example
20099 ^done,path="/usr/bin"
20101 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20102 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20104 -environment-path -r /usr/local/bin
20105 ^done,path="/usr/local/bin:/usr/bin"
20110 @subheading The @code{-environment-pwd} Command
20111 @findex -environment-pwd
20113 @subsubheading Synopsis
20119 Show the current working directory.
20121 @subsubheading @value{GDBN} Command
20123 The corresponding @value{GDBN} command is @samp{pwd}.
20125 @subsubheading Example
20130 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20135 @node GDB/MI Thread Commands
20136 @section @sc{gdb/mi} Thread Commands
20139 @subheading The @code{-thread-info} Command
20140 @findex -thread-info
20142 @subsubheading Synopsis
20145 -thread-info [ @var{thread-id} ]
20148 Reports information about either a specific thread, if
20149 the @var{thread-id} parameter is present, or about all
20150 threads. When printing information about all threads,
20151 also reports the current thread.
20153 @subsubheading @value{GDBN} Command
20155 The @samp{info thread} command prints the same information
20158 @subsubheading Example
20163 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20164 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
20165 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20166 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20167 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
20168 current-thread-id="1"
20172 @subheading The @code{-thread-list-ids} Command
20173 @findex -thread-list-ids
20175 @subsubheading Synopsis
20181 Produces a list of the currently known @value{GDBN} thread ids. At the
20182 end of the list it also prints the total number of such threads.
20184 @subsubheading @value{GDBN} Command
20186 Part of @samp{info threads} supplies the same information.
20188 @subsubheading Example
20190 No threads present, besides the main process:
20195 ^done,thread-ids=@{@},number-of-threads="0"
20205 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20206 number-of-threads="3"
20211 @subheading The @code{-thread-select} Command
20212 @findex -thread-select
20214 @subsubheading Synopsis
20217 -thread-select @var{threadnum}
20220 Make @var{threadnum} the current thread. It prints the number of the new
20221 current thread, and the topmost frame for that thread.
20223 @subsubheading @value{GDBN} Command
20225 The corresponding @value{GDBN} command is @samp{thread}.
20227 @subsubheading Example
20234 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20235 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20239 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20240 number-of-threads="3"
20243 ^done,new-thread-id="3",
20244 frame=@{level="0",func="vprintf",
20245 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20246 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20251 @node GDB/MI Program Execution
20252 @section @sc{gdb/mi} Program Execution
20254 These are the asynchronous commands which generate the out-of-band
20255 record @samp{*stopped}. Currently @value{GDBN} only really executes
20256 asynchronously with remote targets and this interaction is mimicked in
20259 @subheading The @code{-exec-continue} Command
20260 @findex -exec-continue
20262 @subsubheading Synopsis
20268 Resumes the execution of the inferior program until a breakpoint is
20269 encountered, or until the inferior exits.
20271 @subsubheading @value{GDBN} Command
20273 The corresponding @value{GDBN} corresponding is @samp{continue}.
20275 @subsubheading Example
20282 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
20283 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
20289 @subheading The @code{-exec-finish} Command
20290 @findex -exec-finish
20292 @subsubheading Synopsis
20298 Resumes the execution of the inferior program until the current
20299 function is exited. Displays the results returned by the function.
20301 @subsubheading @value{GDBN} Command
20303 The corresponding @value{GDBN} command is @samp{finish}.
20305 @subsubheading Example
20307 Function returning @code{void}.
20314 *stopped,reason="function-finished",frame=@{func="main",args=[],
20315 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
20319 Function returning other than @code{void}. The name of the internal
20320 @value{GDBN} variable storing the result is printed, together with the
20327 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
20328 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
20329 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20330 gdb-result-var="$1",return-value="0"
20335 @subheading The @code{-exec-interrupt} Command
20336 @findex -exec-interrupt
20338 @subsubheading Synopsis
20344 Interrupts the background execution of the target. Note how the token
20345 associated with the stop message is the one for the execution command
20346 that has been interrupted. The token for the interrupt itself only
20347 appears in the @samp{^done} output. If the user is trying to
20348 interrupt a non-running program, an error message will be printed.
20350 @subsubheading @value{GDBN} Command
20352 The corresponding @value{GDBN} command is @samp{interrupt}.
20354 @subsubheading Example
20365 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
20366 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
20367 fullname="/home/foo/bar/try.c",line="13"@}
20372 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
20377 @subheading The @code{-exec-next} Command
20380 @subsubheading Synopsis
20386 Resumes execution of the inferior program, stopping when the beginning
20387 of the next source line is reached.
20389 @subsubheading @value{GDBN} Command
20391 The corresponding @value{GDBN} command is @samp{next}.
20393 @subsubheading Example
20399 *stopped,reason="end-stepping-range",line="8",file="hello.c"
20404 @subheading The @code{-exec-next-instruction} Command
20405 @findex -exec-next-instruction
20407 @subsubheading Synopsis
20410 -exec-next-instruction
20413 Executes one machine instruction. If the instruction is a function
20414 call, continues until the function returns. If the program stops at an
20415 instruction in the middle of a source line, the address will be
20418 @subsubheading @value{GDBN} Command
20420 The corresponding @value{GDBN} command is @samp{nexti}.
20422 @subsubheading Example
20426 -exec-next-instruction
20430 *stopped,reason="end-stepping-range",
20431 addr="0x000100d4",line="5",file="hello.c"
20436 @subheading The @code{-exec-return} Command
20437 @findex -exec-return
20439 @subsubheading Synopsis
20445 Makes current function return immediately. Doesn't execute the inferior.
20446 Displays the new current frame.
20448 @subsubheading @value{GDBN} Command
20450 The corresponding @value{GDBN} command is @samp{return}.
20452 @subsubheading Example
20456 200-break-insert callee4
20457 200^done,bkpt=@{number="1",addr="0x00010734",
20458 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20463 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20464 frame=@{func="callee4",args=[],
20465 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20466 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20472 111^done,frame=@{level="0",func="callee3",
20473 args=[@{name="strarg",
20474 value="0x11940 \"A string argument.\""@}],
20475 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20476 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20481 @subheading The @code{-exec-run} Command
20484 @subsubheading Synopsis
20490 Starts execution of the inferior from the beginning. The inferior
20491 executes until either a breakpoint is encountered or the program
20492 exits. In the latter case the output will include an exit code, if
20493 the program has exited exceptionally.
20495 @subsubheading @value{GDBN} Command
20497 The corresponding @value{GDBN} command is @samp{run}.
20499 @subsubheading Examples
20504 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20509 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20510 frame=@{func="main",args=[],file="recursive2.c",
20511 fullname="/home/foo/bar/recursive2.c",line="4"@}
20516 Program exited normally:
20524 *stopped,reason="exited-normally"
20529 Program exited exceptionally:
20537 *stopped,reason="exited",exit-code="01"
20541 Another way the program can terminate is if it receives a signal such as
20542 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20546 *stopped,reason="exited-signalled",signal-name="SIGINT",
20547 signal-meaning="Interrupt"
20551 @c @subheading -exec-signal
20554 @subheading The @code{-exec-step} Command
20557 @subsubheading Synopsis
20563 Resumes execution of the inferior program, stopping when the beginning
20564 of the next source line is reached, if the next source line is not a
20565 function call. If it is, stop at the first instruction of the called
20568 @subsubheading @value{GDBN} Command
20570 The corresponding @value{GDBN} command is @samp{step}.
20572 @subsubheading Example
20574 Stepping into a function:
20580 *stopped,reason="end-stepping-range",
20581 frame=@{func="foo",args=[@{name="a",value="10"@},
20582 @{name="b",value="0"@}],file="recursive2.c",
20583 fullname="/home/foo/bar/recursive2.c",line="11"@}
20593 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20598 @subheading The @code{-exec-step-instruction} Command
20599 @findex -exec-step-instruction
20601 @subsubheading Synopsis
20604 -exec-step-instruction
20607 Resumes the inferior which executes one machine instruction. The
20608 output, once @value{GDBN} has stopped, will vary depending on whether
20609 we have stopped in the middle of a source line or not. In the former
20610 case, the address at which the program stopped will be printed as
20613 @subsubheading @value{GDBN} Command
20615 The corresponding @value{GDBN} command is @samp{stepi}.
20617 @subsubheading Example
20621 -exec-step-instruction
20625 *stopped,reason="end-stepping-range",
20626 frame=@{func="foo",args=[],file="try.c",
20627 fullname="/home/foo/bar/try.c",line="10"@}
20629 -exec-step-instruction
20633 *stopped,reason="end-stepping-range",
20634 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20635 fullname="/home/foo/bar/try.c",line="10"@}
20640 @subheading The @code{-exec-until} Command
20641 @findex -exec-until
20643 @subsubheading Synopsis
20646 -exec-until [ @var{location} ]
20649 Executes the inferior until the @var{location} specified in the
20650 argument is reached. If there is no argument, the inferior executes
20651 until a source line greater than the current one is reached. The
20652 reason for stopping in this case will be @samp{location-reached}.
20654 @subsubheading @value{GDBN} Command
20656 The corresponding @value{GDBN} command is @samp{until}.
20658 @subsubheading Example
20662 -exec-until recursive2.c:6
20666 *stopped,reason="location-reached",frame=@{func="main",args=[],
20667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
20672 @subheading -file-clear
20673 Is this going away????
20676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20677 @node GDB/MI Stack Manipulation
20678 @section @sc{gdb/mi} Stack Manipulation Commands
20681 @subheading The @code{-stack-info-frame} Command
20682 @findex -stack-info-frame
20684 @subsubheading Synopsis
20690 Get info on the selected frame.
20692 @subsubheading @value{GDBN} Command
20694 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
20695 (without arguments).
20697 @subsubheading Example
20702 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
20703 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20704 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
20708 @subheading The @code{-stack-info-depth} Command
20709 @findex -stack-info-depth
20711 @subsubheading Synopsis
20714 -stack-info-depth [ @var{max-depth} ]
20717 Return the depth of the stack. If the integer argument @var{max-depth}
20718 is specified, do not count beyond @var{max-depth} frames.
20720 @subsubheading @value{GDBN} Command
20722 There's no equivalent @value{GDBN} command.
20724 @subsubheading Example
20726 For a stack with frame levels 0 through 11:
20733 -stack-info-depth 4
20736 -stack-info-depth 12
20739 -stack-info-depth 11
20742 -stack-info-depth 13
20747 @subheading The @code{-stack-list-arguments} Command
20748 @findex -stack-list-arguments
20750 @subsubheading Synopsis
20753 -stack-list-arguments @var{show-values}
20754 [ @var{low-frame} @var{high-frame} ]
20757 Display a list of the arguments for the frames between @var{low-frame}
20758 and @var{high-frame} (inclusive). If @var{low-frame} and
20759 @var{high-frame} are not provided, list the arguments for the whole
20760 call stack. If the two arguments are equal, show the single frame
20761 at the corresponding level. It is an error if @var{low-frame} is
20762 larger than the actual number of frames. On the other hand,
20763 @var{high-frame} may be larger than the actual number of frames, in
20764 which case only existing frames will be returned.
20766 The @var{show-values} argument must have a value of 0 or 1. A value of
20767 0 means that only the names of the arguments are listed, a value of 1
20768 means that both names and values of the arguments are printed.
20770 @subsubheading @value{GDBN} Command
20772 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
20773 @samp{gdb_get_args} command which partially overlaps with the
20774 functionality of @samp{-stack-list-arguments}.
20776 @subsubheading Example
20783 frame=@{level="0",addr="0x00010734",func="callee4",
20784 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20785 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
20786 frame=@{level="1",addr="0x0001076c",func="callee3",
20787 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20788 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
20789 frame=@{level="2",addr="0x0001078c",func="callee2",
20790 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20791 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
20792 frame=@{level="3",addr="0x000107b4",func="callee1",
20793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
20795 frame=@{level="4",addr="0x000107e0",func="main",
20796 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20797 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
20799 -stack-list-arguments 0
20802 frame=@{level="0",args=[]@},
20803 frame=@{level="1",args=[name="strarg"]@},
20804 frame=@{level="2",args=[name="intarg",name="strarg"]@},
20805 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
20806 frame=@{level="4",args=[]@}]
20808 -stack-list-arguments 1
20811 frame=@{level="0",args=[]@},
20813 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20814 frame=@{level="2",args=[
20815 @{name="intarg",value="2"@},
20816 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20817 @{frame=@{level="3",args=[
20818 @{name="intarg",value="2"@},
20819 @{name="strarg",value="0x11940 \"A string argument.\""@},
20820 @{name="fltarg",value="3.5"@}]@},
20821 frame=@{level="4",args=[]@}]
20823 -stack-list-arguments 0 2 2
20824 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20826 -stack-list-arguments 1 2 2
20827 ^done,stack-args=[frame=@{level="2",
20828 args=[@{name="intarg",value="2"@},
20829 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20833 @c @subheading -stack-list-exception-handlers
20836 @subheading The @code{-stack-list-frames} Command
20837 @findex -stack-list-frames
20839 @subsubheading Synopsis
20842 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20845 List the frames currently on the stack. For each frame it displays the
20850 The frame number, 0 being the topmost frame, i.e., the innermost function.
20852 The @code{$pc} value for that frame.
20856 File name of the source file where the function lives.
20858 Line number corresponding to the @code{$pc}.
20861 If invoked without arguments, this command prints a backtrace for the
20862 whole stack. If given two integer arguments, it shows the frames whose
20863 levels are between the two arguments (inclusive). If the two arguments
20864 are equal, it shows the single frame at the corresponding level. It is
20865 an error if @var{low-frame} is larger than the actual number of
20866 frames. On the other hand, @var{high-frame} may be larger than the
20867 actual number of frames, in which case only existing frames will be returned.
20869 @subsubheading @value{GDBN} Command
20871 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20873 @subsubheading Example
20875 Full stack backtrace:
20881 [frame=@{level="0",addr="0x0001076c",func="foo",
20882 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20883 frame=@{level="1",addr="0x000107a4",func="foo",
20884 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20885 frame=@{level="2",addr="0x000107a4",func="foo",
20886 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20887 frame=@{level="3",addr="0x000107a4",func="foo",
20888 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20889 frame=@{level="4",addr="0x000107a4",func="foo",
20890 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20891 frame=@{level="5",addr="0x000107a4",func="foo",
20892 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20893 frame=@{level="6",addr="0x000107a4",func="foo",
20894 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20895 frame=@{level="7",addr="0x000107a4",func="foo",
20896 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20897 frame=@{level="8",addr="0x000107a4",func="foo",
20898 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20899 frame=@{level="9",addr="0x000107a4",func="foo",
20900 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20901 frame=@{level="10",addr="0x000107a4",func="foo",
20902 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20903 frame=@{level="11",addr="0x00010738",func="main",
20904 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20908 Show frames between @var{low_frame} and @var{high_frame}:
20912 -stack-list-frames 3 5
20914 [frame=@{level="3",addr="0x000107a4",func="foo",
20915 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20916 frame=@{level="4",addr="0x000107a4",func="foo",
20917 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20918 frame=@{level="5",addr="0x000107a4",func="foo",
20919 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20923 Show a single frame:
20927 -stack-list-frames 3 3
20929 [frame=@{level="3",addr="0x000107a4",func="foo",
20930 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20935 @subheading The @code{-stack-list-locals} Command
20936 @findex -stack-list-locals
20938 @subsubheading Synopsis
20941 -stack-list-locals @var{print-values}
20944 Display the local variable names for the selected frame. If
20945 @var{print-values} is 0 or @code{--no-values}, print only the names of
20946 the variables; if it is 1 or @code{--all-values}, print also their
20947 values; and if it is 2 or @code{--simple-values}, print the name,
20948 type and value for simple data types and the name and type for arrays,
20949 structures and unions. In this last case, a frontend can immediately
20950 display the value of simple data types and create variable objects for
20951 other data types when the user wishes to explore their values in
20954 @subsubheading @value{GDBN} Command
20956 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20958 @subsubheading Example
20962 -stack-list-locals 0
20963 ^done,locals=[name="A",name="B",name="C"]
20965 -stack-list-locals --all-values
20966 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20967 @{name="C",value="@{1, 2, 3@}"@}]
20968 -stack-list-locals --simple-values
20969 ^done,locals=[@{name="A",type="int",value="1"@},
20970 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20975 @subheading The @code{-stack-select-frame} Command
20976 @findex -stack-select-frame
20978 @subsubheading Synopsis
20981 -stack-select-frame @var{framenum}
20984 Change the selected frame. Select a different frame @var{framenum} on
20987 @subsubheading @value{GDBN} Command
20989 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20990 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20992 @subsubheading Example
20996 -stack-select-frame 2
21001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21002 @node GDB/MI Variable Objects
21003 @section @sc{gdb/mi} Variable Objects
21007 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21009 For the implementation of a variable debugger window (locals, watched
21010 expressions, etc.), we are proposing the adaptation of the existing code
21011 used by @code{Insight}.
21013 The two main reasons for that are:
21017 It has been proven in practice (it is already on its second generation).
21020 It will shorten development time (needless to say how important it is
21024 The original interface was designed to be used by Tcl code, so it was
21025 slightly changed so it could be used through @sc{gdb/mi}. This section
21026 describes the @sc{gdb/mi} operations that will be available and gives some
21027 hints about their use.
21029 @emph{Note}: In addition to the set of operations described here, we
21030 expect the @sc{gui} implementation of a variable window to require, at
21031 least, the following operations:
21034 @item @code{-gdb-show} @code{output-radix}
21035 @item @code{-stack-list-arguments}
21036 @item @code{-stack-list-locals}
21037 @item @code{-stack-select-frame}
21042 @subheading Introduction to Variable Objects
21044 @cindex variable objects in @sc{gdb/mi}
21046 Variable objects are "object-oriented" MI interface for examining and
21047 changing values of expressions. Unlike some other MI interfaces that
21048 work with expressions, variable objects are specifically designed for
21049 simple and efficient presentation in the frontend. A variable object
21050 is identified by string name. When a variable object is created, the
21051 frontend specifies the expression for that variable object. The
21052 expression can be a simple variable, or it can be an arbitrary complex
21053 expression, and can even involve CPU registers. After creating a
21054 variable object, the frontend can invoke other variable object
21055 operations---for example to obtain or change the value of a variable
21056 object, or to change display format.
21058 Variable objects have hierarchical tree structure. Any variable object
21059 that corresponds to a composite type, such as structure in C, has
21060 a number of child variable objects, for example corresponding to each
21061 element of a structure. A child variable object can itself have
21062 children, recursively. Recursion ends when we reach
21063 leaf variable objects, which always have built-in types. Child variable
21064 objects are created only by explicit request, so if a frontend
21065 is not interested in the children of a particular variable object, no
21066 child will be created.
21068 For a leaf variable object it is possible to obtain its value as a
21069 string, or set the value from a string. String value can be also
21070 obtained for a non-leaf variable object, but it's generally a string
21071 that only indicates the type of the object, and does not list its
21072 contents. Assignment to a non-leaf variable object is not allowed.
21074 A frontend does not need to read the values of all variable objects each time
21075 the program stops. Instead, MI provides an update command that lists all
21076 variable objects whose values has changed since the last update
21077 operation. This considerably reduces the amount of data that must
21078 be transferred to the frontend. As noted above, children variable
21079 objects are created on demand, and only leaf variable objects have a
21080 real value. As result, gdb will read target memory only for leaf
21081 variables that frontend has created.
21083 The automatic update is not always desirable. For example, a frontend
21084 might want to keep a value of some expression for future reference,
21085 and never update it. For another example, fetching memory is
21086 relatively slow for embedded targets, so a frontend might want
21087 to disable automatic update for the variables that are either not
21088 visible on the screen, or ``closed''. This is possible using so
21089 called ``frozen variable objects''. Such variable objects are never
21090 implicitly updated.
21092 The following is the complete set of @sc{gdb/mi} operations defined to
21093 access this functionality:
21095 @multitable @columnfractions .4 .6
21096 @item @strong{Operation}
21097 @tab @strong{Description}
21099 @item @code{-var-create}
21100 @tab create a variable object
21101 @item @code{-var-delete}
21102 @tab delete the variable object and/or its children
21103 @item @code{-var-set-format}
21104 @tab set the display format of this variable
21105 @item @code{-var-show-format}
21106 @tab show the display format of this variable
21107 @item @code{-var-info-num-children}
21108 @tab tells how many children this object has
21109 @item @code{-var-list-children}
21110 @tab return a list of the object's children
21111 @item @code{-var-info-type}
21112 @tab show the type of this variable object
21113 @item @code{-var-info-expression}
21114 @tab print parent-relative expression that this variable object represents
21115 @item @code{-var-info-path-expression}
21116 @tab print full expression that this variable object represents
21117 @item @code{-var-show-attributes}
21118 @tab is this variable editable? does it exist here?
21119 @item @code{-var-evaluate-expression}
21120 @tab get the value of this variable
21121 @item @code{-var-assign}
21122 @tab set the value of this variable
21123 @item @code{-var-update}
21124 @tab update the variable and its children
21125 @item @code{-var-set-frozen}
21126 @tab set frozeness attribute
21129 In the next subsection we describe each operation in detail and suggest
21130 how it can be used.
21132 @subheading Description And Use of Operations on Variable Objects
21134 @subheading The @code{-var-create} Command
21135 @findex -var-create
21137 @subsubheading Synopsis
21140 -var-create @{@var{name} | "-"@}
21141 @{@var{frame-addr} | "*"@} @var{expression}
21144 This operation creates a variable object, which allows the monitoring of
21145 a variable, the result of an expression, a memory cell or a CPU
21148 The @var{name} parameter is the string by which the object can be
21149 referenced. It must be unique. If @samp{-} is specified, the varobj
21150 system will generate a string ``varNNNNNN'' automatically. It will be
21151 unique provided that one does not specify @var{name} on that format.
21152 The command fails if a duplicate name is found.
21154 The frame under which the expression should be evaluated can be
21155 specified by @var{frame-addr}. A @samp{*} indicates that the current
21156 frame should be used.
21158 @var{expression} is any expression valid on the current language set (must not
21159 begin with a @samp{*}), or one of the following:
21163 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21166 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21169 @samp{$@var{regname}} --- a CPU register name
21172 @subsubheading Result
21174 This operation returns the name, number of children and the type of the
21175 object created. Type is returned as a string as the ones generated by
21176 the @value{GDBN} CLI:
21179 name="@var{name}",numchild="N",type="@var{type}"
21183 @subheading The @code{-var-delete} Command
21184 @findex -var-delete
21186 @subsubheading Synopsis
21189 -var-delete [ -c ] @var{name}
21192 Deletes a previously created variable object and all of its children.
21193 With the @samp{-c} option, just deletes the children.
21195 Returns an error if the object @var{name} is not found.
21198 @subheading The @code{-var-set-format} Command
21199 @findex -var-set-format
21201 @subsubheading Synopsis
21204 -var-set-format @var{name} @var{format-spec}
21207 Sets the output format for the value of the object @var{name} to be
21210 @anchor{-var-set-format}
21211 The syntax for the @var{format-spec} is as follows:
21214 @var{format-spec} @expansion{}
21215 @{binary | decimal | hexadecimal | octal | natural@}
21218 The natural format is the default format choosen automatically
21219 based on the variable type (like decimal for an @code{int}, hex
21220 for pointers, etc.).
21222 For a variable with children, the format is set only on the
21223 variable itself, and the children are not affected.
21225 @subheading The @code{-var-show-format} Command
21226 @findex -var-show-format
21228 @subsubheading Synopsis
21231 -var-show-format @var{name}
21234 Returns the format used to display the value of the object @var{name}.
21237 @var{format} @expansion{}
21242 @subheading The @code{-var-info-num-children} Command
21243 @findex -var-info-num-children
21245 @subsubheading Synopsis
21248 -var-info-num-children @var{name}
21251 Returns the number of children of a variable object @var{name}:
21258 @subheading The @code{-var-list-children} Command
21259 @findex -var-list-children
21261 @subsubheading Synopsis
21264 -var-list-children [@var{print-values}] @var{name}
21266 @anchor{-var-list-children}
21268 Return a list of the children of the specified variable object and
21269 create variable objects for them, if they do not already exist. With
21270 a single argument or if @var{print-values} has a value for of 0 or
21271 @code{--no-values}, print only the names of the variables; if
21272 @var{print-values} is 1 or @code{--all-values}, also print their
21273 values; and if it is 2 or @code{--simple-values} print the name and
21274 value for simple data types and just the name for arrays, structures
21277 @subsubheading Example
21281 -var-list-children n
21282 ^done,numchild=@var{n},children=[@{name=@var{name},
21283 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
21285 -var-list-children --all-values n
21286 ^done,numchild=@var{n},children=[@{name=@var{name},
21287 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
21291 @subheading The @code{-var-info-type} Command
21292 @findex -var-info-type
21294 @subsubheading Synopsis
21297 -var-info-type @var{name}
21300 Returns the type of the specified variable @var{name}. The type is
21301 returned as a string in the same format as it is output by the
21305 type=@var{typename}
21309 @subheading The @code{-var-info-expression} Command
21310 @findex -var-info-expression
21312 @subsubheading Synopsis
21315 -var-info-expression @var{name}
21318 Returns a string that is suitable for presenting this
21319 variable object in user interface. The string is generally
21320 not valid expression in the current language, and cannot be evaluated.
21322 For example, if @code{a} is an array, and variable object
21323 @code{A} was created for @code{a}, then we'll get this output:
21326 (gdb) -var-info-expression A.1
21327 ^done,lang="C",exp="1"
21331 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
21333 Note that the output of the @code{-var-list-children} command also
21334 includes those expressions, so the @code{-var-info-expression} command
21337 @subheading The @code{-var-info-path-expression} Command
21338 @findex -var-info-path-expression
21340 @subsubheading Synopsis
21343 -var-info-path-expression @var{name}
21346 Returns an expression that can be evaluated in the current
21347 context and will yield the same value that a variable object has.
21348 Compare this with the @code{-var-info-expression} command, which
21349 result can be used only for UI presentation. Typical use of
21350 the @code{-var-info-path-expression} command is creating a
21351 watchpoint from a variable object.
21353 For example, suppose @code{C} is a C@t{++} class, derived from class
21354 @code{Base}, and that the @code{Base} class has a member called
21355 @code{m_size}. Assume a variable @code{c} is has the type of
21356 @code{C} and a variable object @code{C} was created for variable
21357 @code{c}. Then, we'll get this output:
21359 (gdb) -var-info-path-expression C.Base.public.m_size
21360 ^done,path_expr=((Base)c).m_size)
21363 @subheading The @code{-var-show-attributes} Command
21364 @findex -var-show-attributes
21366 @subsubheading Synopsis
21369 -var-show-attributes @var{name}
21372 List attributes of the specified variable object @var{name}:
21375 status=@var{attr} [ ( ,@var{attr} )* ]
21379 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21381 @subheading The @code{-var-evaluate-expression} Command
21382 @findex -var-evaluate-expression
21384 @subsubheading Synopsis
21387 -var-evaluate-expression [-f @var{format-spec}] @var{name}
21390 Evaluates the expression that is represented by the specified variable
21391 object and returns its value as a string. The format of the string
21392 can be specified with the @samp{-f} option. The possible values of
21393 this option are the same as for @code{-var-set-format}
21394 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
21395 the current display format will be used. The current display format
21396 can be changed using the @code{-var-set-format} command.
21402 Note that one must invoke @code{-var-list-children} for a variable
21403 before the value of a child variable can be evaluated.
21405 @subheading The @code{-var-assign} Command
21406 @findex -var-assign
21408 @subsubheading Synopsis
21411 -var-assign @var{name} @var{expression}
21414 Assigns the value of @var{expression} to the variable object specified
21415 by @var{name}. The object must be @samp{editable}. If the variable's
21416 value is altered by the assign, the variable will show up in any
21417 subsequent @code{-var-update} list.
21419 @subsubheading Example
21427 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21431 @subheading The @code{-var-update} Command
21432 @findex -var-update
21434 @subsubheading Synopsis
21437 -var-update [@var{print-values}] @{@var{name} | "*"@}
21440 Reevaluate the expressions corresponding to the variable object
21441 @var{name} and all its direct and indirect children, and return the
21442 list of variable objects whose values have changed; @var{name} must
21443 be a root variable object. Here, ``changed'' means that the result of
21444 @code{-var-evaluate-expression} before and after the
21445 @code{-var-update} is different. If @samp{*} is used as the variable
21446 object names, all existing variable objects are updated, except
21447 for frozen ones (@pxref{-var-set-frozen}). The option
21448 @var{print-values} determines whether both names and values, or just
21449 names are printed. The possible values of this option are the same
21450 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
21451 recommended to use the @samp{--all-values} option, to reduce the
21452 number of MI commands needed on each program stop.
21455 @subsubheading Example
21462 -var-update --all-values var1
21463 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21464 type_changed="false"@}]
21468 @anchor{-var-update}
21469 The field in_scope may take three values:
21473 The variable object's current value is valid.
21476 The variable object does not currently hold a valid value but it may
21477 hold one in the future if its associated expression comes back into
21481 The variable object no longer holds a valid value.
21482 This can occur when the executable file being debugged has changed,
21483 either through recompilation or by using the @value{GDBN} @code{file}
21484 command. The front end should normally choose to delete these variable
21488 In the future new values may be added to this list so the front should
21489 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21491 @subheading The @code{-var-set-frozen} Command
21492 @findex -var-set-frozen
21493 @anchor{-var-set-frozen}
21495 @subsubheading Synopsis
21498 -var-set-frozen @var{name} @var{flag}
21501 Set the frozenness flag on the variable object @var{name}. The
21502 @var{flag} parameter should be either @samp{1} to make the variable
21503 frozen or @samp{0} to make it unfrozen. If a variable object is
21504 frozen, then neither itself, nor any of its children, are
21505 implicitly updated by @code{-var-update} of
21506 a parent variable or by @code{-var-update *}. Only
21507 @code{-var-update} of the variable itself will update its value and
21508 values of its children. After a variable object is unfrozen, it is
21509 implicitly updated by all subsequent @code{-var-update} operations.
21510 Unfreezing a variable does not update it, only subsequent
21511 @code{-var-update} does.
21513 @subsubheading Example
21517 -var-set-frozen V 1
21523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21524 @node GDB/MI Data Manipulation
21525 @section @sc{gdb/mi} Data Manipulation
21527 @cindex data manipulation, in @sc{gdb/mi}
21528 @cindex @sc{gdb/mi}, data manipulation
21529 This section describes the @sc{gdb/mi} commands that manipulate data:
21530 examine memory and registers, evaluate expressions, etc.
21532 @c REMOVED FROM THE INTERFACE.
21533 @c @subheading -data-assign
21534 @c Change the value of a program variable. Plenty of side effects.
21535 @c @subsubheading GDB Command
21537 @c @subsubheading Example
21540 @subheading The @code{-data-disassemble} Command
21541 @findex -data-disassemble
21543 @subsubheading Synopsis
21547 [ -s @var{start-addr} -e @var{end-addr} ]
21548 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21556 @item @var{start-addr}
21557 is the beginning address (or @code{$pc})
21558 @item @var{end-addr}
21560 @item @var{filename}
21561 is the name of the file to disassemble
21562 @item @var{linenum}
21563 is the line number to disassemble around
21565 is the number of disassembly lines to be produced. If it is -1,
21566 the whole function will be disassembled, in case no @var{end-addr} is
21567 specified. If @var{end-addr} is specified as a non-zero value, and
21568 @var{lines} is lower than the number of disassembly lines between
21569 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21570 displayed; if @var{lines} is higher than the number of lines between
21571 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21574 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21578 @subsubheading Result
21580 The output for each instruction is composed of four fields:
21589 Note that whatever included in the instruction field, is not manipulated
21590 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21592 @subsubheading @value{GDBN} Command
21594 There's no direct mapping from this command to the CLI.
21596 @subsubheading Example
21598 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21602 -data-disassemble -s $pc -e "$pc + 20" -- 0
21605 @{address="0x000107c0",func-name="main",offset="4",
21606 inst="mov 2, %o0"@},
21607 @{address="0x000107c4",func-name="main",offset="8",
21608 inst="sethi %hi(0x11800), %o2"@},
21609 @{address="0x000107c8",func-name="main",offset="12",
21610 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21611 @{address="0x000107cc",func-name="main",offset="16",
21612 inst="sethi %hi(0x11800), %o2"@},
21613 @{address="0x000107d0",func-name="main",offset="20",
21614 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21618 Disassemble the whole @code{main} function. Line 32 is part of
21622 -data-disassemble -f basics.c -l 32 -- 0
21624 @{address="0x000107bc",func-name="main",offset="0",
21625 inst="save %sp, -112, %sp"@},
21626 @{address="0x000107c0",func-name="main",offset="4",
21627 inst="mov 2, %o0"@},
21628 @{address="0x000107c4",func-name="main",offset="8",
21629 inst="sethi %hi(0x11800), %o2"@},
21631 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
21632 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
21636 Disassemble 3 instructions from the start of @code{main}:
21640 -data-disassemble -f basics.c -l 32 -n 3 -- 0
21642 @{address="0x000107bc",func-name="main",offset="0",
21643 inst="save %sp, -112, %sp"@},
21644 @{address="0x000107c0",func-name="main",offset="4",
21645 inst="mov 2, %o0"@},
21646 @{address="0x000107c4",func-name="main",offset="8",
21647 inst="sethi %hi(0x11800), %o2"@}]
21651 Disassemble 3 instructions from the start of @code{main} in mixed mode:
21655 -data-disassemble -f basics.c -l 32 -n 3 -- 1
21657 src_and_asm_line=@{line="31",
21658 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21659 testsuite/gdb.mi/basics.c",line_asm_insn=[
21660 @{address="0x000107bc",func-name="main",offset="0",
21661 inst="save %sp, -112, %sp"@}]@},
21662 src_and_asm_line=@{line="32",
21663 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21664 testsuite/gdb.mi/basics.c",line_asm_insn=[
21665 @{address="0x000107c0",func-name="main",offset="4",
21666 inst="mov 2, %o0"@},
21667 @{address="0x000107c4",func-name="main",offset="8",
21668 inst="sethi %hi(0x11800), %o2"@}]@}]
21673 @subheading The @code{-data-evaluate-expression} Command
21674 @findex -data-evaluate-expression
21676 @subsubheading Synopsis
21679 -data-evaluate-expression @var{expr}
21682 Evaluate @var{expr} as an expression. The expression could contain an
21683 inferior function call. The function call will execute synchronously.
21684 If the expression contains spaces, it must be enclosed in double quotes.
21686 @subsubheading @value{GDBN} Command
21688 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
21689 @samp{call}. In @code{gdbtk} only, there's a corresponding
21690 @samp{gdb_eval} command.
21692 @subsubheading Example
21694 In the following example, the numbers that precede the commands are the
21695 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
21696 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
21700 211-data-evaluate-expression A
21703 311-data-evaluate-expression &A
21704 311^done,value="0xefffeb7c"
21706 411-data-evaluate-expression A+3
21709 511-data-evaluate-expression "A + 3"
21715 @subheading The @code{-data-list-changed-registers} Command
21716 @findex -data-list-changed-registers
21718 @subsubheading Synopsis
21721 -data-list-changed-registers
21724 Display a list of the registers that have changed.
21726 @subsubheading @value{GDBN} Command
21728 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
21729 has the corresponding command @samp{gdb_changed_register_list}.
21731 @subsubheading Example
21733 On a PPC MBX board:
21741 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
21742 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
21745 -data-list-changed-registers
21746 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
21747 "10","11","13","14","15","16","17","18","19","20","21","22","23",
21748 "24","25","26","27","28","30","31","64","65","66","67","69"]
21753 @subheading The @code{-data-list-register-names} Command
21754 @findex -data-list-register-names
21756 @subsubheading Synopsis
21759 -data-list-register-names [ ( @var{regno} )+ ]
21762 Show a list of register names for the current target. If no arguments
21763 are given, it shows a list of the names of all the registers. If
21764 integer numbers are given as arguments, it will print a list of the
21765 names of the registers corresponding to the arguments. To ensure
21766 consistency between a register name and its number, the output list may
21767 include empty register names.
21769 @subsubheading @value{GDBN} Command
21771 @value{GDBN} does not have a command which corresponds to
21772 @samp{-data-list-register-names}. In @code{gdbtk} there is a
21773 corresponding command @samp{gdb_regnames}.
21775 @subsubheading Example
21777 For the PPC MBX board:
21780 -data-list-register-names
21781 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
21782 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
21783 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
21784 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
21785 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
21786 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
21787 "", "pc","ps","cr","lr","ctr","xer"]
21789 -data-list-register-names 1 2 3
21790 ^done,register-names=["r1","r2","r3"]
21794 @subheading The @code{-data-list-register-values} Command
21795 @findex -data-list-register-values
21797 @subsubheading Synopsis
21800 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
21803 Display the registers' contents. @var{fmt} is the format according to
21804 which the registers' contents are to be returned, followed by an optional
21805 list of numbers specifying the registers to display. A missing list of
21806 numbers indicates that the contents of all the registers must be returned.
21808 Allowed formats for @var{fmt} are:
21825 @subsubheading @value{GDBN} Command
21827 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21828 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21830 @subsubheading Example
21832 For a PPC MBX board (note: line breaks are for readability only, they
21833 don't appear in the actual output):
21837 -data-list-register-values r 64 65
21838 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21839 @{number="65",value="0x00029002"@}]
21841 -data-list-register-values x
21842 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21843 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21844 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21845 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21846 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21847 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21848 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21849 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21850 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21851 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21852 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21853 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21854 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21855 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21856 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21857 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21858 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21859 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21860 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21861 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21862 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21863 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21864 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21865 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21866 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21867 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21868 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21869 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21870 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21871 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21872 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21873 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21874 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21875 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21876 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21877 @{number="69",value="0x20002b03"@}]
21882 @subheading The @code{-data-read-memory} Command
21883 @findex -data-read-memory
21885 @subsubheading Synopsis
21888 -data-read-memory [ -o @var{byte-offset} ]
21889 @var{address} @var{word-format} @var{word-size}
21890 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21897 @item @var{address}
21898 An expression specifying the address of the first memory word to be
21899 read. Complex expressions containing embedded white space should be
21900 quoted using the C convention.
21902 @item @var{word-format}
21903 The format to be used to print the memory words. The notation is the
21904 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21907 @item @var{word-size}
21908 The size of each memory word in bytes.
21910 @item @var{nr-rows}
21911 The number of rows in the output table.
21913 @item @var{nr-cols}
21914 The number of columns in the output table.
21917 If present, indicates that each row should include an @sc{ascii} dump. The
21918 value of @var{aschar} is used as a padding character when a byte is not a
21919 member of the printable @sc{ascii} character set (printable @sc{ascii}
21920 characters are those whose code is between 32 and 126, inclusively).
21922 @item @var{byte-offset}
21923 An offset to add to the @var{address} before fetching memory.
21926 This command displays memory contents as a table of @var{nr-rows} by
21927 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21928 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21929 (returned as @samp{total-bytes}). Should less than the requested number
21930 of bytes be returned by the target, the missing words are identified
21931 using @samp{N/A}. The number of bytes read from the target is returned
21932 in @samp{nr-bytes} and the starting address used to read memory in
21935 The address of the next/previous row or page is available in
21936 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21939 @subsubheading @value{GDBN} Command
21941 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21942 @samp{gdb_get_mem} memory read command.
21944 @subsubheading Example
21946 Read six bytes of memory starting at @code{bytes+6} but then offset by
21947 @code{-6} bytes. Format as three rows of two columns. One byte per
21948 word. Display each word in hex.
21952 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21953 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21954 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21955 prev-page="0x0000138a",memory=[
21956 @{addr="0x00001390",data=["0x00","0x01"]@},
21957 @{addr="0x00001392",data=["0x02","0x03"]@},
21958 @{addr="0x00001394",data=["0x04","0x05"]@}]
21962 Read two bytes of memory starting at address @code{shorts + 64} and
21963 display as a single word formatted in decimal.
21967 5-data-read-memory shorts+64 d 2 1 1
21968 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21969 next-row="0x00001512",prev-row="0x0000150e",
21970 next-page="0x00001512",prev-page="0x0000150e",memory=[
21971 @{addr="0x00001510",data=["128"]@}]
21975 Read thirty two bytes of memory starting at @code{bytes+16} and format
21976 as eight rows of four columns. Include a string encoding with @samp{x}
21977 used as the non-printable character.
21981 4-data-read-memory bytes+16 x 1 8 4 x
21982 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21983 next-row="0x000013c0",prev-row="0x0000139c",
21984 next-page="0x000013c0",prev-page="0x00001380",memory=[
21985 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21986 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21987 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21988 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21989 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21990 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21991 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21992 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21996 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21997 @node GDB/MI Tracepoint Commands
21998 @section @sc{gdb/mi} Tracepoint Commands
22000 The tracepoint commands are not yet implemented.
22002 @c @subheading -trace-actions
22004 @c @subheading -trace-delete
22006 @c @subheading -trace-disable
22008 @c @subheading -trace-dump
22010 @c @subheading -trace-enable
22012 @c @subheading -trace-exists
22014 @c @subheading -trace-find
22016 @c @subheading -trace-frame-number
22018 @c @subheading -trace-info
22020 @c @subheading -trace-insert
22022 @c @subheading -trace-list
22024 @c @subheading -trace-pass-count
22026 @c @subheading -trace-save
22028 @c @subheading -trace-start
22030 @c @subheading -trace-stop
22033 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22034 @node GDB/MI Symbol Query
22035 @section @sc{gdb/mi} Symbol Query Commands
22038 @subheading The @code{-symbol-info-address} Command
22039 @findex -symbol-info-address
22041 @subsubheading Synopsis
22044 -symbol-info-address @var{symbol}
22047 Describe where @var{symbol} is stored.
22049 @subsubheading @value{GDBN} Command
22051 The corresponding @value{GDBN} command is @samp{info address}.
22053 @subsubheading Example
22057 @subheading The @code{-symbol-info-file} Command
22058 @findex -symbol-info-file
22060 @subsubheading Synopsis
22066 Show the file for the symbol.
22068 @subsubheading @value{GDBN} Command
22070 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22071 @samp{gdb_find_file}.
22073 @subsubheading Example
22077 @subheading The @code{-symbol-info-function} Command
22078 @findex -symbol-info-function
22080 @subsubheading Synopsis
22083 -symbol-info-function
22086 Show which function the symbol lives in.
22088 @subsubheading @value{GDBN} Command
22090 @samp{gdb_get_function} in @code{gdbtk}.
22092 @subsubheading Example
22096 @subheading The @code{-symbol-info-line} Command
22097 @findex -symbol-info-line
22099 @subsubheading Synopsis
22105 Show the core addresses of the code for a source line.
22107 @subsubheading @value{GDBN} Command
22109 The corresponding @value{GDBN} command is @samp{info line}.
22110 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22112 @subsubheading Example
22116 @subheading The @code{-symbol-info-symbol} Command
22117 @findex -symbol-info-symbol
22119 @subsubheading Synopsis
22122 -symbol-info-symbol @var{addr}
22125 Describe what symbol is at location @var{addr}.
22127 @subsubheading @value{GDBN} Command
22129 The corresponding @value{GDBN} command is @samp{info symbol}.
22131 @subsubheading Example
22135 @subheading The @code{-symbol-list-functions} Command
22136 @findex -symbol-list-functions
22138 @subsubheading Synopsis
22141 -symbol-list-functions
22144 List the functions in the executable.
22146 @subsubheading @value{GDBN} Command
22148 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22149 @samp{gdb_search} in @code{gdbtk}.
22151 @subsubheading Example
22155 @subheading The @code{-symbol-list-lines} Command
22156 @findex -symbol-list-lines
22158 @subsubheading Synopsis
22161 -symbol-list-lines @var{filename}
22164 Print the list of lines that contain code and their associated program
22165 addresses for the given source filename. The entries are sorted in
22166 ascending PC order.
22168 @subsubheading @value{GDBN} Command
22170 There is no corresponding @value{GDBN} command.
22172 @subsubheading Example
22175 -symbol-list-lines basics.c
22176 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22181 @subheading The @code{-symbol-list-types} Command
22182 @findex -symbol-list-types
22184 @subsubheading Synopsis
22190 List all the type names.
22192 @subsubheading @value{GDBN} Command
22194 The corresponding commands are @samp{info types} in @value{GDBN},
22195 @samp{gdb_search} in @code{gdbtk}.
22197 @subsubheading Example
22201 @subheading The @code{-symbol-list-variables} Command
22202 @findex -symbol-list-variables
22204 @subsubheading Synopsis
22207 -symbol-list-variables
22210 List all the global and static variable names.
22212 @subsubheading @value{GDBN} Command
22214 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
22216 @subsubheading Example
22220 @subheading The @code{-symbol-locate} Command
22221 @findex -symbol-locate
22223 @subsubheading Synopsis
22229 @subsubheading @value{GDBN} Command
22231 @samp{gdb_loc} in @code{gdbtk}.
22233 @subsubheading Example
22237 @subheading The @code{-symbol-type} Command
22238 @findex -symbol-type
22240 @subsubheading Synopsis
22243 -symbol-type @var{variable}
22246 Show type of @var{variable}.
22248 @subsubheading @value{GDBN} Command
22250 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
22251 @samp{gdb_obj_variable}.
22253 @subsubheading Example
22257 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22258 @node GDB/MI File Commands
22259 @section @sc{gdb/mi} File Commands
22261 This section describes the GDB/MI commands to specify executable file names
22262 and to read in and obtain symbol table information.
22264 @subheading The @code{-file-exec-and-symbols} Command
22265 @findex -file-exec-and-symbols
22267 @subsubheading Synopsis
22270 -file-exec-and-symbols @var{file}
22273 Specify the executable file to be debugged. This file is the one from
22274 which the symbol table is also read. If no file is specified, the
22275 command clears the executable and symbol information. If breakpoints
22276 are set when using this command with no arguments, @value{GDBN} will produce
22277 error messages. Otherwise, no output is produced, except a completion
22280 @subsubheading @value{GDBN} Command
22282 The corresponding @value{GDBN} command is @samp{file}.
22284 @subsubheading Example
22288 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22294 @subheading The @code{-file-exec-file} Command
22295 @findex -file-exec-file
22297 @subsubheading Synopsis
22300 -file-exec-file @var{file}
22303 Specify the executable file to be debugged. Unlike
22304 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
22305 from this file. If used without argument, @value{GDBN} clears the information
22306 about the executable file. No output is produced, except a completion
22309 @subsubheading @value{GDBN} Command
22311 The corresponding @value{GDBN} command is @samp{exec-file}.
22313 @subsubheading Example
22317 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22323 @subheading The @code{-file-list-exec-sections} Command
22324 @findex -file-list-exec-sections
22326 @subsubheading Synopsis
22329 -file-list-exec-sections
22332 List the sections of the current executable file.
22334 @subsubheading @value{GDBN} Command
22336 The @value{GDBN} command @samp{info file} shows, among the rest, the same
22337 information as this command. @code{gdbtk} has a corresponding command
22338 @samp{gdb_load_info}.
22340 @subsubheading Example
22344 @subheading The @code{-file-list-exec-source-file} Command
22345 @findex -file-list-exec-source-file
22347 @subsubheading Synopsis
22350 -file-list-exec-source-file
22353 List the line number, the current source file, and the absolute path
22354 to the current source file for the current executable. The macro
22355 information field has a value of @samp{1} or @samp{0} depending on
22356 whether or not the file includes preprocessor macro information.
22358 @subsubheading @value{GDBN} Command
22360 The @value{GDBN} equivalent is @samp{info source}
22362 @subsubheading Example
22366 123-file-list-exec-source-file
22367 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
22372 @subheading The @code{-file-list-exec-source-files} Command
22373 @findex -file-list-exec-source-files
22375 @subsubheading Synopsis
22378 -file-list-exec-source-files
22381 List the source files for the current executable.
22383 It will always output the filename, but only when @value{GDBN} can find
22384 the absolute file name of a source file, will it output the fullname.
22386 @subsubheading @value{GDBN} Command
22388 The @value{GDBN} equivalent is @samp{info sources}.
22389 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
22391 @subsubheading Example
22394 -file-list-exec-source-files
22396 @{file=foo.c,fullname=/home/foo.c@},
22397 @{file=/home/bar.c,fullname=/home/bar.c@},
22398 @{file=gdb_could_not_find_fullpath.c@}]
22402 @subheading The @code{-file-list-shared-libraries} Command
22403 @findex -file-list-shared-libraries
22405 @subsubheading Synopsis
22408 -file-list-shared-libraries
22411 List the shared libraries in the program.
22413 @subsubheading @value{GDBN} Command
22415 The corresponding @value{GDBN} command is @samp{info shared}.
22417 @subsubheading Example
22421 @subheading The @code{-file-list-symbol-files} Command
22422 @findex -file-list-symbol-files
22424 @subsubheading Synopsis
22427 -file-list-symbol-files
22432 @subsubheading @value{GDBN} Command
22434 The corresponding @value{GDBN} command is @samp{info file} (part of it).
22436 @subsubheading Example
22440 @subheading The @code{-file-symbol-file} Command
22441 @findex -file-symbol-file
22443 @subsubheading Synopsis
22446 -file-symbol-file @var{file}
22449 Read symbol table info from the specified @var{file} argument. When
22450 used without arguments, clears @value{GDBN}'s symbol table info. No output is
22451 produced, except for a completion notification.
22453 @subsubheading @value{GDBN} Command
22455 The corresponding @value{GDBN} command is @samp{symbol-file}.
22457 @subsubheading Example
22461 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22467 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22468 @node GDB/MI Memory Overlay Commands
22469 @section @sc{gdb/mi} Memory Overlay Commands
22471 The memory overlay commands are not implemented.
22473 @c @subheading -overlay-auto
22475 @c @subheading -overlay-list-mapping-state
22477 @c @subheading -overlay-list-overlays
22479 @c @subheading -overlay-map
22481 @c @subheading -overlay-off
22483 @c @subheading -overlay-on
22485 @c @subheading -overlay-unmap
22487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22488 @node GDB/MI Signal Handling Commands
22489 @section @sc{gdb/mi} Signal Handling Commands
22491 Signal handling commands are not implemented.
22493 @c @subheading -signal-handle
22495 @c @subheading -signal-list-handle-actions
22497 @c @subheading -signal-list-signal-types
22501 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22502 @node GDB/MI Target Manipulation
22503 @section @sc{gdb/mi} Target Manipulation Commands
22506 @subheading The @code{-target-attach} Command
22507 @findex -target-attach
22509 @subsubheading Synopsis
22512 -target-attach @var{pid} | @var{file}
22515 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
22517 @subsubheading @value{GDBN} Command
22519 The corresponding @value{GDBN} command is @samp{attach}.
22521 @subsubheading Example
22525 =thread-created,id="1"
22526 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22531 @subheading The @code{-target-compare-sections} Command
22532 @findex -target-compare-sections
22534 @subsubheading Synopsis
22537 -target-compare-sections [ @var{section} ]
22540 Compare data of section @var{section} on target to the exec file.
22541 Without the argument, all sections are compared.
22543 @subsubheading @value{GDBN} Command
22545 The @value{GDBN} equivalent is @samp{compare-sections}.
22547 @subsubheading Example
22551 @subheading The @code{-target-detach} Command
22552 @findex -target-detach
22554 @subsubheading Synopsis
22560 Detach from the remote target which normally resumes its execution.
22563 @subsubheading @value{GDBN} Command
22565 The corresponding @value{GDBN} command is @samp{detach}.
22567 @subsubheading Example
22577 @subheading The @code{-target-disconnect} Command
22578 @findex -target-disconnect
22580 @subsubheading Synopsis
22586 Disconnect from the remote target. There's no output and the target is
22587 generally not resumed.
22589 @subsubheading @value{GDBN} Command
22591 The corresponding @value{GDBN} command is @samp{disconnect}.
22593 @subsubheading Example
22603 @subheading The @code{-target-download} Command
22604 @findex -target-download
22606 @subsubheading Synopsis
22612 Loads the executable onto the remote target.
22613 It prints out an update message every half second, which includes the fields:
22617 The name of the section.
22619 The size of what has been sent so far for that section.
22621 The size of the section.
22623 The total size of what was sent so far (the current and the previous sections).
22625 The size of the overall executable to download.
22629 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
22630 @sc{gdb/mi} Output Syntax}).
22632 In addition, it prints the name and size of the sections, as they are
22633 downloaded. These messages include the following fields:
22637 The name of the section.
22639 The size of the section.
22641 The size of the overall executable to download.
22645 At the end, a summary is printed.
22647 @subsubheading @value{GDBN} Command
22649 The corresponding @value{GDBN} command is @samp{load}.
22651 @subsubheading Example
22653 Note: each status message appears on a single line. Here the messages
22654 have been broken down so that they can fit onto a page.
22659 +download,@{section=".text",section-size="6668",total-size="9880"@}
22660 +download,@{section=".text",section-sent="512",section-size="6668",
22661 total-sent="512",total-size="9880"@}
22662 +download,@{section=".text",section-sent="1024",section-size="6668",
22663 total-sent="1024",total-size="9880"@}
22664 +download,@{section=".text",section-sent="1536",section-size="6668",
22665 total-sent="1536",total-size="9880"@}
22666 +download,@{section=".text",section-sent="2048",section-size="6668",
22667 total-sent="2048",total-size="9880"@}
22668 +download,@{section=".text",section-sent="2560",section-size="6668",
22669 total-sent="2560",total-size="9880"@}
22670 +download,@{section=".text",section-sent="3072",section-size="6668",
22671 total-sent="3072",total-size="9880"@}
22672 +download,@{section=".text",section-sent="3584",section-size="6668",
22673 total-sent="3584",total-size="9880"@}
22674 +download,@{section=".text",section-sent="4096",section-size="6668",
22675 total-sent="4096",total-size="9880"@}
22676 +download,@{section=".text",section-sent="4608",section-size="6668",
22677 total-sent="4608",total-size="9880"@}
22678 +download,@{section=".text",section-sent="5120",section-size="6668",
22679 total-sent="5120",total-size="9880"@}
22680 +download,@{section=".text",section-sent="5632",section-size="6668",
22681 total-sent="5632",total-size="9880"@}
22682 +download,@{section=".text",section-sent="6144",section-size="6668",
22683 total-sent="6144",total-size="9880"@}
22684 +download,@{section=".text",section-sent="6656",section-size="6668",
22685 total-sent="6656",total-size="9880"@}
22686 +download,@{section=".init",section-size="28",total-size="9880"@}
22687 +download,@{section=".fini",section-size="28",total-size="9880"@}
22688 +download,@{section=".data",section-size="3156",total-size="9880"@}
22689 +download,@{section=".data",section-sent="512",section-size="3156",
22690 total-sent="7236",total-size="9880"@}
22691 +download,@{section=".data",section-sent="1024",section-size="3156",
22692 total-sent="7748",total-size="9880"@}
22693 +download,@{section=".data",section-sent="1536",section-size="3156",
22694 total-sent="8260",total-size="9880"@}
22695 +download,@{section=".data",section-sent="2048",section-size="3156",
22696 total-sent="8772",total-size="9880"@}
22697 +download,@{section=".data",section-sent="2560",section-size="3156",
22698 total-sent="9284",total-size="9880"@}
22699 +download,@{section=".data",section-sent="3072",section-size="3156",
22700 total-sent="9796",total-size="9880"@}
22701 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
22707 @subheading The @code{-target-exec-status} Command
22708 @findex -target-exec-status
22710 @subsubheading Synopsis
22713 -target-exec-status
22716 Provide information on the state of the target (whether it is running or
22717 not, for instance).
22719 @subsubheading @value{GDBN} Command
22721 There's no equivalent @value{GDBN} command.
22723 @subsubheading Example
22727 @subheading The @code{-target-list-available-targets} Command
22728 @findex -target-list-available-targets
22730 @subsubheading Synopsis
22733 -target-list-available-targets
22736 List the possible targets to connect to.
22738 @subsubheading @value{GDBN} Command
22740 The corresponding @value{GDBN} command is @samp{help target}.
22742 @subsubheading Example
22746 @subheading The @code{-target-list-current-targets} Command
22747 @findex -target-list-current-targets
22749 @subsubheading Synopsis
22752 -target-list-current-targets
22755 Describe the current target.
22757 @subsubheading @value{GDBN} Command
22759 The corresponding information is printed by @samp{info file} (among
22762 @subsubheading Example
22766 @subheading The @code{-target-list-parameters} Command
22767 @findex -target-list-parameters
22769 @subsubheading Synopsis
22772 -target-list-parameters
22777 @subsubheading @value{GDBN} Command
22781 @subsubheading Example
22785 @subheading The @code{-target-select} Command
22786 @findex -target-select
22788 @subsubheading Synopsis
22791 -target-select @var{type} @var{parameters @dots{}}
22794 Connect @value{GDBN} to the remote target. This command takes two args:
22798 The type of target, for instance @samp{remote}, etc.
22799 @item @var{parameters}
22800 Device names, host names and the like. @xref{Target Commands, ,
22801 Commands for Managing Targets}, for more details.
22804 The output is a connection notification, followed by the address at
22805 which the target program is, in the following form:
22808 ^connected,addr="@var{address}",func="@var{function name}",
22809 args=[@var{arg list}]
22812 @subsubheading @value{GDBN} Command
22814 The corresponding @value{GDBN} command is @samp{target}.
22816 @subsubheading Example
22820 -target-select remote /dev/ttya
22821 ^connected,addr="0xfe00a300",func="??",args=[]
22825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22826 @node GDB/MI File Transfer Commands
22827 @section @sc{gdb/mi} File Transfer Commands
22830 @subheading The @code{-target-file-put} Command
22831 @findex -target-file-put
22833 @subsubheading Synopsis
22836 -target-file-put @var{hostfile} @var{targetfile}
22839 Copy file @var{hostfile} from the host system (the machine running
22840 @value{GDBN}) to @var{targetfile} on the target system.
22842 @subsubheading @value{GDBN} Command
22844 The corresponding @value{GDBN} command is @samp{remote put}.
22846 @subsubheading Example
22850 -target-file-put localfile remotefile
22856 @subheading The @code{-target-file-get} Command
22857 @findex -target-file-get
22859 @subsubheading Synopsis
22862 -target-file-get @var{targetfile} @var{hostfile}
22865 Copy file @var{targetfile} from the target system to @var{hostfile}
22866 on the host system.
22868 @subsubheading @value{GDBN} Command
22870 The corresponding @value{GDBN} command is @samp{remote get}.
22872 @subsubheading Example
22876 -target-file-get remotefile localfile
22882 @subheading The @code{-target-file-delete} Command
22883 @findex -target-file-delete
22885 @subsubheading Synopsis
22888 -target-file-delete @var{targetfile}
22891 Delete @var{targetfile} from the target system.
22893 @subsubheading @value{GDBN} Command
22895 The corresponding @value{GDBN} command is @samp{remote delete}.
22897 @subsubheading Example
22901 -target-file-delete remotefile
22907 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22908 @node GDB/MI Miscellaneous Commands
22909 @section Miscellaneous @sc{gdb/mi} Commands
22911 @c @subheading -gdb-complete
22913 @subheading The @code{-gdb-exit} Command
22916 @subsubheading Synopsis
22922 Exit @value{GDBN} immediately.
22924 @subsubheading @value{GDBN} Command
22926 Approximately corresponds to @samp{quit}.
22928 @subsubheading Example
22937 @subheading The @code{-exec-abort} Command
22938 @findex -exec-abort
22940 @subsubheading Synopsis
22946 Kill the inferior running program.
22948 @subsubheading @value{GDBN} Command
22950 The corresponding @value{GDBN} command is @samp{kill}.
22952 @subsubheading Example
22956 @subheading The @code{-gdb-set} Command
22959 @subsubheading Synopsis
22965 Set an internal @value{GDBN} variable.
22966 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22968 @subsubheading @value{GDBN} Command
22970 The corresponding @value{GDBN} command is @samp{set}.
22972 @subsubheading Example
22982 @subheading The @code{-gdb-show} Command
22985 @subsubheading Synopsis
22991 Show the current value of a @value{GDBN} variable.
22993 @subsubheading @value{GDBN} Command
22995 The corresponding @value{GDBN} command is @samp{show}.
22997 @subsubheading Example
23006 @c @subheading -gdb-source
23009 @subheading The @code{-gdb-version} Command
23010 @findex -gdb-version
23012 @subsubheading Synopsis
23018 Show version information for @value{GDBN}. Used mostly in testing.
23020 @subsubheading @value{GDBN} Command
23022 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23023 default shows this information when you start an interactive session.
23025 @subsubheading Example
23027 @c This example modifies the actual output from GDB to avoid overfull
23033 ~Copyright 2000 Free Software Foundation, Inc.
23034 ~GDB is free software, covered by the GNU General Public License, and
23035 ~you are welcome to change it and/or distribute copies of it under
23036 ~ certain conditions.
23037 ~Type "show copying" to see the conditions.
23038 ~There is absolutely no warranty for GDB. Type "show warranty" for
23040 ~This GDB was configured as
23041 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23046 @subheading The @code{-list-features} Command
23047 @findex -list-features
23049 Returns a list of particular features of the MI protocol that
23050 this version of gdb implements. A feature can be a command,
23051 or a new field in an output of some command, or even an
23052 important bugfix. While a frontend can sometimes detect presence
23053 of a feature at runtime, it is easier to perform detection at debugger
23056 The command returns a list of strings, with each string naming an
23057 available feature. Each returned string is just a name, it does not
23058 have any internal structure. The list of possible feature names
23064 (gdb) -list-features
23065 ^done,result=["feature1","feature2"]
23068 The current list of features is:
23071 @item frozen-varobjs
23072 Indicates presence of the @code{-var-set-frozen} command, as well
23073 as possible presense of the @code{frozen} field in the output
23074 of @code{-varobj-create}.
23075 @item pending-breakpoints
23076 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23078 Indicates presence of the @code{-thread-info} command.
23082 @subheading The @code{-list-target-features} Command
23083 @findex -list-target-features
23085 Returns a list of particular features that are supported by the
23086 target. Those features affect the permitted MI commands, but
23087 unlike the features reported by the @code{-list-features} command, the
23088 features depend on which target GDB is using at the moment. Whenever
23089 a target can change, due to commands such as @code{-target-select},
23090 @code{-target-attach} or @code{-exec-run}, the list of target features
23091 may change, and the frontend should obtain it again.
23095 (gdb) -list-features
23096 ^done,result=["async"]
23099 The current list of features is:
23103 Indicates that the target is capable of asynchronous command
23104 execution, which means that @value{GDBN} will accept further commands
23105 while the target is running.
23110 @subheading The @code{-interpreter-exec} Command
23111 @findex -interpreter-exec
23113 @subheading Synopsis
23116 -interpreter-exec @var{interpreter} @var{command}
23118 @anchor{-interpreter-exec}
23120 Execute the specified @var{command} in the given @var{interpreter}.
23122 @subheading @value{GDBN} Command
23124 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23126 @subheading Example
23130 -interpreter-exec console "break main"
23131 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23132 &"During symbol reading, bad structure-type format.\n"
23133 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23138 @subheading The @code{-inferior-tty-set} Command
23139 @findex -inferior-tty-set
23141 @subheading Synopsis
23144 -inferior-tty-set /dev/pts/1
23147 Set terminal for future runs of the program being debugged.
23149 @subheading @value{GDBN} Command
23151 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23153 @subheading Example
23157 -inferior-tty-set /dev/pts/1
23162 @subheading The @code{-inferior-tty-show} Command
23163 @findex -inferior-tty-show
23165 @subheading Synopsis
23171 Show terminal for future runs of program being debugged.
23173 @subheading @value{GDBN} Command
23175 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
23177 @subheading Example
23181 -inferior-tty-set /dev/pts/1
23185 ^done,inferior_tty_terminal="/dev/pts/1"
23189 @subheading The @code{-enable-timings} Command
23190 @findex -enable-timings
23192 @subheading Synopsis
23195 -enable-timings [yes | no]
23198 Toggle the printing of the wallclock, user and system times for an MI
23199 command as a field in its output. This command is to help frontend
23200 developers optimize the performance of their code. No argument is
23201 equivalent to @samp{yes}.
23203 @subheading @value{GDBN} Command
23207 @subheading Example
23215 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23216 addr="0x080484ed",func="main",file="myprog.c",
23217 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
23218 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
23226 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23227 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
23228 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
23229 fullname="/home/nickrob/myprog.c",line="73"@}
23234 @chapter @value{GDBN} Annotations
23236 This chapter describes annotations in @value{GDBN}. Annotations were
23237 designed to interface @value{GDBN} to graphical user interfaces or other
23238 similar programs which want to interact with @value{GDBN} at a
23239 relatively high level.
23241 The annotation mechanism has largely been superseded by @sc{gdb/mi}
23245 This is Edition @value{EDITION}, @value{DATE}.
23249 * Annotations Overview:: What annotations are; the general syntax.
23250 * Server Prefix:: Issuing a command without affecting user state.
23251 * Prompting:: Annotations marking @value{GDBN}'s need for input.
23252 * Errors:: Annotations for error messages.
23253 * Invalidation:: Some annotations describe things now invalid.
23254 * Annotations for Running::
23255 Whether the program is running, how it stopped, etc.
23256 * Source Annotations:: Annotations describing source code.
23259 @node Annotations Overview
23260 @section What is an Annotation?
23261 @cindex annotations
23263 Annotations start with a newline character, two @samp{control-z}
23264 characters, and the name of the annotation. If there is no additional
23265 information associated with this annotation, the name of the annotation
23266 is followed immediately by a newline. If there is additional
23267 information, the name of the annotation is followed by a space, the
23268 additional information, and a newline. The additional information
23269 cannot contain newline characters.
23271 Any output not beginning with a newline and two @samp{control-z}
23272 characters denotes literal output from @value{GDBN}. Currently there is
23273 no need for @value{GDBN} to output a newline followed by two
23274 @samp{control-z} characters, but if there was such a need, the
23275 annotations could be extended with an @samp{escape} annotation which
23276 means those three characters as output.
23278 The annotation @var{level}, which is specified using the
23279 @option{--annotate} command line option (@pxref{Mode Options}), controls
23280 how much information @value{GDBN} prints together with its prompt,
23281 values of expressions, source lines, and other types of output. Level 0
23282 is for no annotations, level 1 is for use when @value{GDBN} is run as a
23283 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
23284 for programs that control @value{GDBN}, and level 2 annotations have
23285 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
23286 Interface, annotate, GDB's Obsolete Annotations}).
23289 @kindex set annotate
23290 @item set annotate @var{level}
23291 The @value{GDBN} command @code{set annotate} sets the level of
23292 annotations to the specified @var{level}.
23294 @item show annotate
23295 @kindex show annotate
23296 Show the current annotation level.
23299 This chapter describes level 3 annotations.
23301 A simple example of starting up @value{GDBN} with annotations is:
23304 $ @kbd{gdb --annotate=3}
23306 Copyright 2003 Free Software Foundation, Inc.
23307 GDB is free software, covered by the GNU General Public License,
23308 and you are welcome to change it and/or distribute copies of it
23309 under certain conditions.
23310 Type "show copying" to see the conditions.
23311 There is absolutely no warranty for GDB. Type "show warranty"
23313 This GDB was configured as "i386-pc-linux-gnu"
23324 Here @samp{quit} is input to @value{GDBN}; the rest is output from
23325 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
23326 denotes a @samp{control-z} character) are annotations; the rest is
23327 output from @value{GDBN}.
23329 @node Server Prefix
23330 @section The Server Prefix
23331 @cindex server prefix
23333 If you prefix a command with @samp{server } then it will not affect
23334 the command history, nor will it affect @value{GDBN}'s notion of which
23335 command to repeat if @key{RET} is pressed on a line by itself. This
23336 means that commands can be run behind a user's back by a front-end in
23337 a transparent manner.
23339 The server prefix does not affect the recording of values into the value
23340 history; to print a value without recording it into the value history,
23341 use the @code{output} command instead of the @code{print} command.
23344 @section Annotation for @value{GDBN} Input
23346 @cindex annotations for prompts
23347 When @value{GDBN} prompts for input, it annotates this fact so it is possible
23348 to know when to send output, when the output from a given command is
23351 Different kinds of input each have a different @dfn{input type}. Each
23352 input type has three annotations: a @code{pre-} annotation, which
23353 denotes the beginning of any prompt which is being output, a plain
23354 annotation, which denotes the end of the prompt, and then a @code{post-}
23355 annotation which denotes the end of any echo which may (or may not) be
23356 associated with the input. For example, the @code{prompt} input type
23357 features the following annotations:
23365 The input types are
23368 @findex pre-prompt annotation
23369 @findex prompt annotation
23370 @findex post-prompt annotation
23372 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
23374 @findex pre-commands annotation
23375 @findex commands annotation
23376 @findex post-commands annotation
23378 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
23379 command. The annotations are repeated for each command which is input.
23381 @findex pre-overload-choice annotation
23382 @findex overload-choice annotation
23383 @findex post-overload-choice annotation
23384 @item overload-choice
23385 When @value{GDBN} wants the user to select between various overloaded functions.
23387 @findex pre-query annotation
23388 @findex query annotation
23389 @findex post-query annotation
23391 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
23393 @findex pre-prompt-for-continue annotation
23394 @findex prompt-for-continue annotation
23395 @findex post-prompt-for-continue annotation
23396 @item prompt-for-continue
23397 When @value{GDBN} is asking the user to press return to continue. Note: Don't
23398 expect this to work well; instead use @code{set height 0} to disable
23399 prompting. This is because the counting of lines is buggy in the
23400 presence of annotations.
23405 @cindex annotations for errors, warnings and interrupts
23407 @findex quit annotation
23412 This annotation occurs right before @value{GDBN} responds to an interrupt.
23414 @findex error annotation
23419 This annotation occurs right before @value{GDBN} responds to an error.
23421 Quit and error annotations indicate that any annotations which @value{GDBN} was
23422 in the middle of may end abruptly. For example, if a
23423 @code{value-history-begin} annotation is followed by a @code{error}, one
23424 cannot expect to receive the matching @code{value-history-end}. One
23425 cannot expect not to receive it either, however; an error annotation
23426 does not necessarily mean that @value{GDBN} is immediately returning all the way
23429 @findex error-begin annotation
23430 A quit or error annotation may be preceded by
23436 Any output between that and the quit or error annotation is the error
23439 Warning messages are not yet annotated.
23440 @c If we want to change that, need to fix warning(), type_error(),
23441 @c range_error(), and possibly other places.
23444 @section Invalidation Notices
23446 @cindex annotations for invalidation messages
23447 The following annotations say that certain pieces of state may have
23451 @findex frames-invalid annotation
23452 @item ^Z^Zframes-invalid
23454 The frames (for example, output from the @code{backtrace} command) may
23457 @findex breakpoints-invalid annotation
23458 @item ^Z^Zbreakpoints-invalid
23460 The breakpoints may have changed. For example, the user just added or
23461 deleted a breakpoint.
23464 @node Annotations for Running
23465 @section Running the Program
23466 @cindex annotations for running programs
23468 @findex starting annotation
23469 @findex stopping annotation
23470 When the program starts executing due to a @value{GDBN} command such as
23471 @code{step} or @code{continue},
23477 is output. When the program stops,
23483 is output. Before the @code{stopped} annotation, a variety of
23484 annotations describe how the program stopped.
23487 @findex exited annotation
23488 @item ^Z^Zexited @var{exit-status}
23489 The program exited, and @var{exit-status} is the exit status (zero for
23490 successful exit, otherwise nonzero).
23492 @findex signalled annotation
23493 @findex signal-name annotation
23494 @findex signal-name-end annotation
23495 @findex signal-string annotation
23496 @findex signal-string-end annotation
23497 @item ^Z^Zsignalled
23498 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23499 annotation continues:
23505 ^Z^Zsignal-name-end
23509 ^Z^Zsignal-string-end
23514 where @var{name} is the name of the signal, such as @code{SIGILL} or
23515 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23516 as @code{Illegal Instruction} or @code{Segmentation fault}.
23517 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23518 user's benefit and have no particular format.
23520 @findex signal annotation
23522 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23523 just saying that the program received the signal, not that it was
23524 terminated with it.
23526 @findex breakpoint annotation
23527 @item ^Z^Zbreakpoint @var{number}
23528 The program hit breakpoint number @var{number}.
23530 @findex watchpoint annotation
23531 @item ^Z^Zwatchpoint @var{number}
23532 The program hit watchpoint number @var{number}.
23535 @node Source Annotations
23536 @section Displaying Source
23537 @cindex annotations for source display
23539 @findex source annotation
23540 The following annotation is used instead of displaying source code:
23543 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23546 where @var{filename} is an absolute file name indicating which source
23547 file, @var{line} is the line number within that file (where 1 is the
23548 first line in the file), @var{character} is the character position
23549 within the file (where 0 is the first character in the file) (for most
23550 debug formats this will necessarily point to the beginning of a line),
23551 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23552 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23553 @var{addr} is the address in the target program associated with the
23554 source which is being displayed. @var{addr} is in the form @samp{0x}
23555 followed by one or more lowercase hex digits (note that this does not
23556 depend on the language).
23559 @chapter Reporting Bugs in @value{GDBN}
23560 @cindex bugs in @value{GDBN}
23561 @cindex reporting bugs in @value{GDBN}
23563 Your bug reports play an essential role in making @value{GDBN} reliable.
23565 Reporting a bug may help you by bringing a solution to your problem, or it
23566 may not. But in any case the principal function of a bug report is to help
23567 the entire community by making the next version of @value{GDBN} work better. Bug
23568 reports are your contribution to the maintenance of @value{GDBN}.
23570 In order for a bug report to serve its purpose, you must include the
23571 information that enables us to fix the bug.
23574 * Bug Criteria:: Have you found a bug?
23575 * Bug Reporting:: How to report bugs
23579 @section Have You Found a Bug?
23580 @cindex bug criteria
23582 If you are not sure whether you have found a bug, here are some guidelines:
23585 @cindex fatal signal
23586 @cindex debugger crash
23587 @cindex crash of debugger
23589 If the debugger gets a fatal signal, for any input whatever, that is a
23590 @value{GDBN} bug. Reliable debuggers never crash.
23592 @cindex error on valid input
23594 If @value{GDBN} produces an error message for valid input, that is a
23595 bug. (Note that if you're cross debugging, the problem may also be
23596 somewhere in the connection to the target.)
23598 @cindex invalid input
23600 If @value{GDBN} does not produce an error message for invalid input,
23601 that is a bug. However, you should note that your idea of
23602 ``invalid input'' might be our idea of ``an extension'' or ``support
23603 for traditional practice''.
23606 If you are an experienced user of debugging tools, your suggestions
23607 for improvement of @value{GDBN} are welcome in any case.
23610 @node Bug Reporting
23611 @section How to Report Bugs
23612 @cindex bug reports
23613 @cindex @value{GDBN} bugs, reporting
23615 A number of companies and individuals offer support for @sc{gnu} products.
23616 If you obtained @value{GDBN} from a support organization, we recommend you
23617 contact that organization first.
23619 You can find contact information for many support companies and
23620 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
23622 @c should add a web page ref...
23625 @ifset BUGURL_DEFAULT
23626 In any event, we also recommend that you submit bug reports for
23627 @value{GDBN}. The preferred method is to submit them directly using
23628 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
23629 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
23632 @strong{Do not send bug reports to @samp{info-gdb}, or to
23633 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
23634 not want to receive bug reports. Those that do have arranged to receive
23637 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
23638 serves as a repeater. The mailing list and the newsgroup carry exactly
23639 the same messages. Often people think of posting bug reports to the
23640 newsgroup instead of mailing them. This appears to work, but it has one
23641 problem which can be crucial: a newsgroup posting often lacks a mail
23642 path back to the sender. Thus, if we need to ask for more information,
23643 we may be unable to reach you. For this reason, it is better to send
23644 bug reports to the mailing list.
23646 @ifclear BUGURL_DEFAULT
23647 In any event, we also recommend that you submit bug reports for
23648 @value{GDBN} to @value{BUGURL}.
23652 The fundamental principle of reporting bugs usefully is this:
23653 @strong{report all the facts}. If you are not sure whether to state a
23654 fact or leave it out, state it!
23656 Often people omit facts because they think they know what causes the
23657 problem and assume that some details do not matter. Thus, you might
23658 assume that the name of the variable you use in an example does not matter.
23659 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
23660 stray memory reference which happens to fetch from the location where that
23661 name is stored in memory; perhaps, if the name were different, the contents
23662 of that location would fool the debugger into doing the right thing despite
23663 the bug. Play it safe and give a specific, complete example. That is the
23664 easiest thing for you to do, and the most helpful.
23666 Keep in mind that the purpose of a bug report is to enable us to fix the
23667 bug. It may be that the bug has been reported previously, but neither
23668 you nor we can know that unless your bug report is complete and
23671 Sometimes people give a few sketchy facts and ask, ``Does this ring a
23672 bell?'' Those bug reports are useless, and we urge everyone to
23673 @emph{refuse to respond to them} except to chide the sender to report
23676 To enable us to fix the bug, you should include all these things:
23680 The version of @value{GDBN}. @value{GDBN} announces it if you start
23681 with no arguments; you can also print it at any time using @code{show
23684 Without this, we will not know whether there is any point in looking for
23685 the bug in the current version of @value{GDBN}.
23688 The type of machine you are using, and the operating system name and
23692 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
23693 ``@value{GCC}--2.8.1''.
23696 What compiler (and its version) was used to compile the program you are
23697 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
23698 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
23699 to get this information; for other compilers, see the documentation for
23703 The command arguments you gave the compiler to compile your example and
23704 observe the bug. For example, did you use @samp{-O}? To guarantee
23705 you will not omit something important, list them all. A copy of the
23706 Makefile (or the output from make) is sufficient.
23708 If we were to try to guess the arguments, we would probably guess wrong
23709 and then we might not encounter the bug.
23712 A complete input script, and all necessary source files, that will
23716 A description of what behavior you observe that you believe is
23717 incorrect. For example, ``It gets a fatal signal.''
23719 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
23720 will certainly notice it. But if the bug is incorrect output, we might
23721 not notice unless it is glaringly wrong. You might as well not give us
23722 a chance to make a mistake.
23724 Even if the problem you experience is a fatal signal, you should still
23725 say so explicitly. Suppose something strange is going on, such as, your
23726 copy of @value{GDBN} is out of synch, or you have encountered a bug in
23727 the C library on your system. (This has happened!) Your copy might
23728 crash and ours would not. If you told us to expect a crash, then when
23729 ours fails to crash, we would know that the bug was not happening for
23730 us. If you had not told us to expect a crash, then we would not be able
23731 to draw any conclusion from our observations.
23734 @cindex recording a session script
23735 To collect all this information, you can use a session recording program
23736 such as @command{script}, which is available on many Unix systems.
23737 Just run your @value{GDBN} session inside @command{script} and then
23738 include the @file{typescript} file with your bug report.
23740 Another way to record a @value{GDBN} session is to run @value{GDBN}
23741 inside Emacs and then save the entire buffer to a file.
23744 If you wish to suggest changes to the @value{GDBN} source, send us context
23745 diffs. If you even discuss something in the @value{GDBN} source, refer to
23746 it by context, not by line number.
23748 The line numbers in our development sources will not match those in your
23749 sources. Your line numbers would convey no useful information to us.
23753 Here are some things that are not necessary:
23757 A description of the envelope of the bug.
23759 Often people who encounter a bug spend a lot of time investigating
23760 which changes to the input file will make the bug go away and which
23761 changes will not affect it.
23763 This is often time consuming and not very useful, because the way we
23764 will find the bug is by running a single example under the debugger
23765 with breakpoints, not by pure deduction from a series of examples.
23766 We recommend that you save your time for something else.
23768 Of course, if you can find a simpler example to report @emph{instead}
23769 of the original one, that is a convenience for us. Errors in the
23770 output will be easier to spot, running under the debugger will take
23771 less time, and so on.
23773 However, simplification is not vital; if you do not want to do this,
23774 report the bug anyway and send us the entire test case you used.
23777 A patch for the bug.
23779 A patch for the bug does help us if it is a good one. But do not omit
23780 the necessary information, such as the test case, on the assumption that
23781 a patch is all we need. We might see problems with your patch and decide
23782 to fix the problem another way, or we might not understand it at all.
23784 Sometimes with a program as complicated as @value{GDBN} it is very hard to
23785 construct an example that will make the program follow a certain path
23786 through the code. If you do not send us the example, we will not be able
23787 to construct one, so we will not be able to verify that the bug is fixed.
23789 And if we cannot understand what bug you are trying to fix, or why your
23790 patch should be an improvement, we will not install it. A test case will
23791 help us to understand.
23794 A guess about what the bug is or what it depends on.
23796 Such guesses are usually wrong. Even we cannot guess right about such
23797 things without first using the debugger to find the facts.
23800 @c The readline documentation is distributed with the readline code
23801 @c and consists of the two following files:
23803 @c inc-hist.texinfo
23804 @c Use -I with makeinfo to point to the appropriate directory,
23805 @c environment var TEXINPUTS with TeX.
23806 @include rluser.texi
23807 @include inc-hist.texinfo
23810 @node Formatting Documentation
23811 @appendix Formatting Documentation
23813 @cindex @value{GDBN} reference card
23814 @cindex reference card
23815 The @value{GDBN} 4 release includes an already-formatted reference card, ready
23816 for printing with PostScript or Ghostscript, in the @file{gdb}
23817 subdirectory of the main source directory@footnote{In
23818 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
23819 release.}. If you can use PostScript or Ghostscript with your printer,
23820 you can print the reference card immediately with @file{refcard.ps}.
23822 The release also includes the source for the reference card. You
23823 can format it, using @TeX{}, by typing:
23829 The @value{GDBN} reference card is designed to print in @dfn{landscape}
23830 mode on US ``letter'' size paper;
23831 that is, on a sheet 11 inches wide by 8.5 inches
23832 high. You will need to specify this form of printing as an option to
23833 your @sc{dvi} output program.
23835 @cindex documentation
23837 All the documentation for @value{GDBN} comes as part of the machine-readable
23838 distribution. The documentation is written in Texinfo format, which is
23839 a documentation system that uses a single source file to produce both
23840 on-line information and a printed manual. You can use one of the Info
23841 formatting commands to create the on-line version of the documentation
23842 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
23844 @value{GDBN} includes an already formatted copy of the on-line Info
23845 version of this manual in the @file{gdb} subdirectory. The main Info
23846 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
23847 subordinate files matching @samp{gdb.info*} in the same directory. If
23848 necessary, you can print out these files, or read them with any editor;
23849 but they are easier to read using the @code{info} subsystem in @sc{gnu}
23850 Emacs or the standalone @code{info} program, available as part of the
23851 @sc{gnu} Texinfo distribution.
23853 If you want to format these Info files yourself, you need one of the
23854 Info formatting programs, such as @code{texinfo-format-buffer} or
23857 If you have @code{makeinfo} installed, and are in the top level
23858 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23859 version @value{GDBVN}), you can make the Info file by typing:
23866 If you want to typeset and print copies of this manual, you need @TeX{},
23867 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23868 Texinfo definitions file.
23870 @TeX{} is a typesetting program; it does not print files directly, but
23871 produces output files called @sc{dvi} files. To print a typeset
23872 document, you need a program to print @sc{dvi} files. If your system
23873 has @TeX{} installed, chances are it has such a program. The precise
23874 command to use depends on your system; @kbd{lpr -d} is common; another
23875 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23876 require a file name without any extension or a @samp{.dvi} extension.
23878 @TeX{} also requires a macro definitions file called
23879 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23880 written in Texinfo format. On its own, @TeX{} cannot either read or
23881 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23882 and is located in the @file{gdb-@var{version-number}/texinfo}
23885 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23886 typeset and print this manual. First switch to the @file{gdb}
23887 subdirectory of the main source directory (for example, to
23888 @file{gdb-@value{GDBVN}/gdb}) and type:
23894 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23896 @node Installing GDB
23897 @appendix Installing @value{GDBN}
23898 @cindex installation
23901 * Requirements:: Requirements for building @value{GDBN}
23902 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23903 * Separate Objdir:: Compiling @value{GDBN} in another directory
23904 * Config Names:: Specifying names for hosts and targets
23905 * Configure Options:: Summary of options for configure
23909 @section Requirements for Building @value{GDBN}
23910 @cindex building @value{GDBN}, requirements for
23912 Building @value{GDBN} requires various tools and packages to be available.
23913 Other packages will be used only if they are found.
23915 @heading Tools/Packages Necessary for Building @value{GDBN}
23917 @item ISO C90 compiler
23918 @value{GDBN} is written in ISO C90. It should be buildable with any
23919 working C90 compiler, e.g.@: GCC.
23923 @heading Tools/Packages Optional for Building @value{GDBN}
23927 @value{GDBN} can use the Expat XML parsing library. This library may be
23928 included with your operating system distribution; if it is not, you
23929 can get the latest version from @url{http://expat.sourceforge.net}.
23930 The @file{configure} script will search for this library in several
23931 standard locations; if it is installed in an unusual path, you can
23932 use the @option{--with-libexpat-prefix} option to specify its location.
23938 Remote protocol memory maps (@pxref{Memory Map Format})
23940 Target descriptions (@pxref{Target Descriptions})
23942 Remote shared library lists (@pxref{Library List Format})
23944 MS-Windows shared libraries (@pxref{Shared Libraries})
23948 @cindex compressed debug sections
23949 @value{GDBN} will use the @samp{zlib} library, if available, to read
23950 compressed debug sections. Some linkers, such as GNU gold, are capable
23951 of producing binaries with compressed debug sections. If @value{GDBN}
23952 is compiled with @samp{zlib}, it will be able to read the debug
23953 information in such binaries.
23955 The @samp{zlib} library is likely included with your operating system
23956 distribution; if it is not, you can get the latest version from
23957 @url{http://zlib.net}.
23961 @node Running Configure
23962 @section Invoking the @value{GDBN} @file{configure} Script
23963 @cindex configuring @value{GDBN}
23964 @value{GDBN} comes with a @file{configure} script that automates the process
23965 of preparing @value{GDBN} for installation; you can then use @code{make} to
23966 build the @code{gdb} program.
23968 @c irrelevant in info file; it's as current as the code it lives with.
23969 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23970 look at the @file{README} file in the sources; we may have improved the
23971 installation procedures since publishing this manual.}
23974 The @value{GDBN} distribution includes all the source code you need for
23975 @value{GDBN} in a single directory, whose name is usually composed by
23976 appending the version number to @samp{gdb}.
23978 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23979 @file{gdb-@value{GDBVN}} directory. That directory contains:
23982 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23983 script for configuring @value{GDBN} and all its supporting libraries
23985 @item gdb-@value{GDBVN}/gdb
23986 the source specific to @value{GDBN} itself
23988 @item gdb-@value{GDBVN}/bfd
23989 source for the Binary File Descriptor library
23991 @item gdb-@value{GDBVN}/include
23992 @sc{gnu} include files
23994 @item gdb-@value{GDBVN}/libiberty
23995 source for the @samp{-liberty} free software library
23997 @item gdb-@value{GDBVN}/opcodes
23998 source for the library of opcode tables and disassemblers
24000 @item gdb-@value{GDBVN}/readline
24001 source for the @sc{gnu} command-line interface
24003 @item gdb-@value{GDBVN}/glob
24004 source for the @sc{gnu} filename pattern-matching subroutine
24006 @item gdb-@value{GDBVN}/mmalloc
24007 source for the @sc{gnu} memory-mapped malloc package
24010 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24011 from the @file{gdb-@var{version-number}} source directory, which in
24012 this example is the @file{gdb-@value{GDBVN}} directory.
24014 First switch to the @file{gdb-@var{version-number}} source directory
24015 if you are not already in it; then run @file{configure}. Pass the
24016 identifier for the platform on which @value{GDBN} will run as an
24022 cd gdb-@value{GDBVN}
24023 ./configure @var{host}
24028 where @var{host} is an identifier such as @samp{sun4} or
24029 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24030 (You can often leave off @var{host}; @file{configure} tries to guess the
24031 correct value by examining your system.)
24033 Running @samp{configure @var{host}} and then running @code{make} builds the
24034 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24035 libraries, then @code{gdb} itself. The configured source files, and the
24036 binaries, are left in the corresponding source directories.
24039 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24040 system does not recognize this automatically when you run a different
24041 shell, you may need to run @code{sh} on it explicitly:
24044 sh configure @var{host}
24047 If you run @file{configure} from a directory that contains source
24048 directories for multiple libraries or programs, such as the
24049 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24051 creates configuration files for every directory level underneath (unless
24052 you tell it not to, with the @samp{--norecursion} option).
24054 You should run the @file{configure} script from the top directory in the
24055 source tree, the @file{gdb-@var{version-number}} directory. If you run
24056 @file{configure} from one of the subdirectories, you will configure only
24057 that subdirectory. That is usually not what you want. In particular,
24058 if you run the first @file{configure} from the @file{gdb} subdirectory
24059 of the @file{gdb-@var{version-number}} directory, you will omit the
24060 configuration of @file{bfd}, @file{readline}, and other sibling
24061 directories of the @file{gdb} subdirectory. This leads to build errors
24062 about missing include files such as @file{bfd/bfd.h}.
24064 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24065 However, you should make sure that the shell on your path (named by
24066 the @samp{SHELL} environment variable) is publicly readable. Remember
24067 that @value{GDBN} uses the shell to start your program---some systems refuse to
24068 let @value{GDBN} debug child processes whose programs are not readable.
24070 @node Separate Objdir
24071 @section Compiling @value{GDBN} in Another Directory
24073 If you want to run @value{GDBN} versions for several host or target machines,
24074 you need a different @code{gdb} compiled for each combination of
24075 host and target. @file{configure} is designed to make this easy by
24076 allowing you to generate each configuration in a separate subdirectory,
24077 rather than in the source directory. If your @code{make} program
24078 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24079 @code{make} in each of these directories builds the @code{gdb}
24080 program specified there.
24082 To build @code{gdb} in a separate directory, run @file{configure}
24083 with the @samp{--srcdir} option to specify where to find the source.
24084 (You also need to specify a path to find @file{configure}
24085 itself from your working directory. If the path to @file{configure}
24086 would be the same as the argument to @samp{--srcdir}, you can leave out
24087 the @samp{--srcdir} option; it is assumed.)
24089 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24090 separate directory for a Sun 4 like this:
24094 cd gdb-@value{GDBVN}
24097 ../gdb-@value{GDBVN}/configure sun4
24102 When @file{configure} builds a configuration using a remote source
24103 directory, it creates a tree for the binaries with the same structure
24104 (and using the same names) as the tree under the source directory. In
24105 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24106 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24107 @file{gdb-sun4/gdb}.
24109 Make sure that your path to the @file{configure} script has just one
24110 instance of @file{gdb} in it. If your path to @file{configure} looks
24111 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24112 one subdirectory of @value{GDBN}, not the whole package. This leads to
24113 build errors about missing include files such as @file{bfd/bfd.h}.
24115 One popular reason to build several @value{GDBN} configurations in separate
24116 directories is to configure @value{GDBN} for cross-compiling (where
24117 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24118 programs that run on another machine---the @dfn{target}).
24119 You specify a cross-debugging target by
24120 giving the @samp{--target=@var{target}} option to @file{configure}.
24122 When you run @code{make} to build a program or library, you must run
24123 it in a configured directory---whatever directory you were in when you
24124 called @file{configure} (or one of its subdirectories).
24126 The @code{Makefile} that @file{configure} generates in each source
24127 directory also runs recursively. If you type @code{make} in a source
24128 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24129 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24130 will build all the required libraries, and then build GDB.
24132 When you have multiple hosts or targets configured in separate
24133 directories, you can run @code{make} on them in parallel (for example,
24134 if they are NFS-mounted on each of the hosts); they will not interfere
24138 @section Specifying Names for Hosts and Targets
24140 The specifications used for hosts and targets in the @file{configure}
24141 script are based on a three-part naming scheme, but some short predefined
24142 aliases are also supported. The full naming scheme encodes three pieces
24143 of information in the following pattern:
24146 @var{architecture}-@var{vendor}-@var{os}
24149 For example, you can use the alias @code{sun4} as a @var{host} argument,
24150 or as the value for @var{target} in a @code{--target=@var{target}}
24151 option. The equivalent full name is @samp{sparc-sun-sunos4}.
24153 The @file{configure} script accompanying @value{GDBN} does not provide
24154 any query facility to list all supported host and target names or
24155 aliases. @file{configure} calls the Bourne shell script
24156 @code{config.sub} to map abbreviations to full names; you can read the
24157 script, if you wish, or you can use it to test your guesses on
24158 abbreviations---for example:
24161 % sh config.sub i386-linux
24163 % sh config.sub alpha-linux
24164 alpha-unknown-linux-gnu
24165 % sh config.sub hp9k700
24167 % sh config.sub sun4
24168 sparc-sun-sunos4.1.1
24169 % sh config.sub sun3
24170 m68k-sun-sunos4.1.1
24171 % sh config.sub i986v
24172 Invalid configuration `i986v': machine `i986v' not recognized
24176 @code{config.sub} is also distributed in the @value{GDBN} source
24177 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
24179 @node Configure Options
24180 @section @file{configure} Options
24182 Here is a summary of the @file{configure} options and arguments that
24183 are most often useful for building @value{GDBN}. @file{configure} also has
24184 several other options not listed here. @inforef{What Configure
24185 Does,,configure.info}, for a full explanation of @file{configure}.
24188 configure @r{[}--help@r{]}
24189 @r{[}--prefix=@var{dir}@r{]}
24190 @r{[}--exec-prefix=@var{dir}@r{]}
24191 @r{[}--srcdir=@var{dirname}@r{]}
24192 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
24193 @r{[}--target=@var{target}@r{]}
24198 You may introduce options with a single @samp{-} rather than
24199 @samp{--} if you prefer; but you may abbreviate option names if you use
24204 Display a quick summary of how to invoke @file{configure}.
24206 @item --prefix=@var{dir}
24207 Configure the source to install programs and files under directory
24210 @item --exec-prefix=@var{dir}
24211 Configure the source to install programs under directory
24214 @c avoid splitting the warning from the explanation:
24216 @item --srcdir=@var{dirname}
24217 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
24218 @code{make} that implements the @code{VPATH} feature.}@*
24219 Use this option to make configurations in directories separate from the
24220 @value{GDBN} source directories. Among other things, you can use this to
24221 build (or maintain) several configurations simultaneously, in separate
24222 directories. @file{configure} writes configuration-specific files in
24223 the current directory, but arranges for them to use the source in the
24224 directory @var{dirname}. @file{configure} creates directories under
24225 the working directory in parallel to the source directories below
24228 @item --norecursion
24229 Configure only the directory level where @file{configure} is executed; do not
24230 propagate configuration to subdirectories.
24232 @item --target=@var{target}
24233 Configure @value{GDBN} for cross-debugging programs running on the specified
24234 @var{target}. Without this option, @value{GDBN} is configured to debug
24235 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
24237 There is no convenient way to generate a list of all available targets.
24239 @item @var{host} @dots{}
24240 Configure @value{GDBN} to run on the specified @var{host}.
24242 There is no convenient way to generate a list of all available hosts.
24245 There are many other options available as well, but they are generally
24246 needed for special purposes only.
24248 @node Maintenance Commands
24249 @appendix Maintenance Commands
24250 @cindex maintenance commands
24251 @cindex internal commands
24253 In addition to commands intended for @value{GDBN} users, @value{GDBN}
24254 includes a number of commands intended for @value{GDBN} developers,
24255 that are not documented elsewhere in this manual. These commands are
24256 provided here for reference. (For commands that turn on debugging
24257 messages, see @ref{Debugging Output}.)
24260 @kindex maint agent
24261 @item maint agent @var{expression}
24262 Translate the given @var{expression} into remote agent bytecodes.
24263 This command is useful for debugging the Agent Expression mechanism
24264 (@pxref{Agent Expressions}).
24266 @kindex maint info breakpoints
24267 @item @anchor{maint info breakpoints}maint info breakpoints
24268 Using the same format as @samp{info breakpoints}, display both the
24269 breakpoints you've set explicitly, and those @value{GDBN} is using for
24270 internal purposes. Internal breakpoints are shown with negative
24271 breakpoint numbers. The type column identifies what kind of breakpoint
24276 Normal, explicitly set breakpoint.
24279 Normal, explicitly set watchpoint.
24282 Internal breakpoint, used to handle correctly stepping through
24283 @code{longjmp} calls.
24285 @item longjmp resume
24286 Internal breakpoint at the target of a @code{longjmp}.
24289 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
24292 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
24295 Shared library events.
24299 @kindex set displaced-stepping
24300 @kindex show displaced-stepping
24301 @cindex displaced stepping support
24302 @cindex out-of-line single-stepping
24303 @item set displaced-stepping
24304 @itemx show displaced-stepping
24305 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
24306 if the target supports it. Displaced stepping is a way to single-step
24307 over breakpoints without removing them from the inferior, by executing
24308 an out-of-line copy of the instruction that was originally at the
24309 breakpoint location. It is also known as out-of-line single-stepping.
24312 @item set displaced-stepping on
24313 If the target architecture supports it, @value{GDBN} will use
24314 displaced stepping to step over breakpoints.
24316 @item set displaced-stepping off
24317 @value{GDBN} will not use displaced stepping to step over breakpoints,
24318 even if such is supported by the target architecture.
24320 @cindex non-stop mode, and @samp{set displaced-stepping}
24321 @item set displaced-stepping auto
24322 This is the default mode. @value{GDBN} will use displaced stepping
24323 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
24324 architecture supports displaced stepping.
24327 @kindex maint check-symtabs
24328 @item maint check-symtabs
24329 Check the consistency of psymtabs and symtabs.
24331 @kindex maint cplus first_component
24332 @item maint cplus first_component @var{name}
24333 Print the first C@t{++} class/namespace component of @var{name}.
24335 @kindex maint cplus namespace
24336 @item maint cplus namespace
24337 Print the list of possible C@t{++} namespaces.
24339 @kindex maint demangle
24340 @item maint demangle @var{name}
24341 Demangle a C@t{++} or Objective-C mangled @var{name}.
24343 @kindex maint deprecate
24344 @kindex maint undeprecate
24345 @cindex deprecated commands
24346 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
24347 @itemx maint undeprecate @var{command}
24348 Deprecate or undeprecate the named @var{command}. Deprecated commands
24349 cause @value{GDBN} to issue a warning when you use them. The optional
24350 argument @var{replacement} says which newer command should be used in
24351 favor of the deprecated one; if it is given, @value{GDBN} will mention
24352 the replacement as part of the warning.
24354 @kindex maint dump-me
24355 @item maint dump-me
24356 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
24357 Cause a fatal signal in the debugger and force it to dump its core.
24358 This is supported only on systems which support aborting a program
24359 with the @code{SIGQUIT} signal.
24361 @kindex maint internal-error
24362 @kindex maint internal-warning
24363 @item maint internal-error @r{[}@var{message-text}@r{]}
24364 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
24365 Cause @value{GDBN} to call the internal function @code{internal_error}
24366 or @code{internal_warning} and hence behave as though an internal error
24367 or internal warning has been detected. In addition to reporting the
24368 internal problem, these functions give the user the opportunity to
24369 either quit @value{GDBN} or create a core file of the current
24370 @value{GDBN} session.
24372 These commands take an optional parameter @var{message-text} that is
24373 used as the text of the error or warning message.
24375 Here's an example of using @code{internal-error}:
24378 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
24379 @dots{}/maint.c:121: internal-error: testing, 1, 2
24380 A problem internal to GDB has been detected. Further
24381 debugging may prove unreliable.
24382 Quit this debugging session? (y or n) @kbd{n}
24383 Create a core file? (y or n) @kbd{n}
24387 @kindex maint packet
24388 @item maint packet @var{text}
24389 If @value{GDBN} is talking to an inferior via the serial protocol,
24390 then this command sends the string @var{text} to the inferior, and
24391 displays the response packet. @value{GDBN} supplies the initial
24392 @samp{$} character, the terminating @samp{#} character, and the
24395 @kindex maint print architecture
24396 @item maint print architecture @r{[}@var{file}@r{]}
24397 Print the entire architecture configuration. The optional argument
24398 @var{file} names the file where the output goes.
24400 @kindex maint print c-tdesc
24401 @item maint print c-tdesc
24402 Print the current target description (@pxref{Target Descriptions}) as
24403 a C source file. The created source file can be used in @value{GDBN}
24404 when an XML parser is not available to parse the description.
24406 @kindex maint print dummy-frames
24407 @item maint print dummy-frames
24408 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
24411 (@value{GDBP}) @kbd{b add}
24413 (@value{GDBP}) @kbd{print add(2,3)}
24414 Breakpoint 2, add (a=2, b=3) at @dots{}
24416 The program being debugged stopped while in a function called from GDB.
24418 (@value{GDBP}) @kbd{maint print dummy-frames}
24419 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
24420 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
24421 call_lo=0x01014000 call_hi=0x01014001
24425 Takes an optional file parameter.
24427 @kindex maint print registers
24428 @kindex maint print raw-registers
24429 @kindex maint print cooked-registers
24430 @kindex maint print register-groups
24431 @item maint print registers @r{[}@var{file}@r{]}
24432 @itemx maint print raw-registers @r{[}@var{file}@r{]}
24433 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
24434 @itemx maint print register-groups @r{[}@var{file}@r{]}
24435 Print @value{GDBN}'s internal register data structures.
24437 The command @code{maint print raw-registers} includes the contents of
24438 the raw register cache; the command @code{maint print cooked-registers}
24439 includes the (cooked) value of all registers; and the command
24440 @code{maint print register-groups} includes the groups that each
24441 register is a member of. @xref{Registers,, Registers, gdbint,
24442 @value{GDBN} Internals}.
24444 These commands take an optional parameter, a file name to which to
24445 write the information.
24447 @kindex maint print reggroups
24448 @item maint print reggroups @r{[}@var{file}@r{]}
24449 Print @value{GDBN}'s internal register group data structures. The
24450 optional argument @var{file} tells to what file to write the
24453 The register groups info looks like this:
24456 (@value{GDBP}) @kbd{maint print reggroups}
24469 This command forces @value{GDBN} to flush its internal register cache.
24471 @kindex maint print objfiles
24472 @cindex info for known object files
24473 @item maint print objfiles
24474 Print a dump of all known object files. For each object file, this
24475 command prints its name, address in memory, and all of its psymtabs
24478 @kindex maint print statistics
24479 @cindex bcache statistics
24480 @item maint print statistics
24481 This command prints, for each object file in the program, various data
24482 about that object file followed by the byte cache (@dfn{bcache})
24483 statistics for the object file. The objfile data includes the number
24484 of minimal, partial, full, and stabs symbols, the number of types
24485 defined by the objfile, the number of as yet unexpanded psym tables,
24486 the number of line tables and string tables, and the amount of memory
24487 used by the various tables. The bcache statistics include the counts,
24488 sizes, and counts of duplicates of all and unique objects, max,
24489 average, and median entry size, total memory used and its overhead and
24490 savings, and various measures of the hash table size and chain
24493 @kindex maint print target-stack
24494 @cindex target stack description
24495 @item maint print target-stack
24496 A @dfn{target} is an interface between the debugger and a particular
24497 kind of file or process. Targets can be stacked in @dfn{strata},
24498 so that more than one target can potentially respond to a request.
24499 In particular, memory accesses will walk down the stack of targets
24500 until they find a target that is interested in handling that particular
24503 This command prints a short description of each layer that was pushed on
24504 the @dfn{target stack}, starting from the top layer down to the bottom one.
24506 @kindex maint print type
24507 @cindex type chain of a data type
24508 @item maint print type @var{expr}
24509 Print the type chain for a type specified by @var{expr}. The argument
24510 can be either a type name or a symbol. If it is a symbol, the type of
24511 that symbol is described. The type chain produced by this command is
24512 a recursive definition of the data type as stored in @value{GDBN}'s
24513 data structures, including its flags and contained types.
24515 @kindex maint set dwarf2 max-cache-age
24516 @kindex maint show dwarf2 max-cache-age
24517 @item maint set dwarf2 max-cache-age
24518 @itemx maint show dwarf2 max-cache-age
24519 Control the DWARF 2 compilation unit cache.
24521 @cindex DWARF 2 compilation units cache
24522 In object files with inter-compilation-unit references, such as those
24523 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24524 reader needs to frequently refer to previously read compilation units.
24525 This setting controls how long a compilation unit will remain in the
24526 cache if it is not referenced. A higher limit means that cached
24527 compilation units will be stored in memory longer, and more total
24528 memory will be used. Setting it to zero disables caching, which will
24529 slow down @value{GDBN} startup, but reduce memory consumption.
24531 @kindex maint set profile
24532 @kindex maint show profile
24533 @cindex profiling GDB
24534 @item maint set profile
24535 @itemx maint show profile
24536 Control profiling of @value{GDBN}.
24538 Profiling will be disabled until you use the @samp{maint set profile}
24539 command to enable it. When you enable profiling, the system will begin
24540 collecting timing and execution count data; when you disable profiling or
24541 exit @value{GDBN}, the results will be written to a log file. Remember that
24542 if you use profiling, @value{GDBN} will overwrite the profiling log file
24543 (often called @file{gmon.out}). If you have a record of important profiling
24544 data in a @file{gmon.out} file, be sure to move it to a safe location.
24546 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24547 compiled with the @samp{-pg} compiler option.
24549 @kindex maint set linux-async
24550 @kindex maint show linux-async
24551 @cindex asynchronous support
24552 @item maint set linux-async
24553 @itemx maint show linux-async
24554 Control the GNU/Linux native asynchronous support
24555 (@pxref{Background Execution}) of @value{GDBN}.
24557 GNU/Linux native asynchronous support will be disabled until you use
24558 the @samp{maint set linux-async} command to enable it.
24560 @kindex maint set remote-async
24561 @kindex maint show remote-async
24562 @cindex asynchronous support
24563 @item maint set remote-async
24564 @itemx maint show remote-async
24565 Control the remote asynchronous support
24566 (@pxref{Background Execution}) of @value{GDBN}.
24568 Remote asynchronous support will be disabled until you use
24569 the @samp{maint set remote-async} command to enable it.
24571 @kindex maint show-debug-regs
24572 @cindex x86 hardware debug registers
24573 @item maint show-debug-regs
24574 Control whether to show variables that mirror the x86 hardware debug
24575 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24576 enabled, the debug registers values are shown when @value{GDBN} inserts or
24577 removes a hardware breakpoint or watchpoint, and when the inferior
24578 triggers a hardware-assisted breakpoint or watchpoint.
24580 @kindex maint space
24581 @cindex memory used by commands
24583 Control whether to display memory usage for each command. If set to a
24584 nonzero value, @value{GDBN} will display how much memory each command
24585 took, following the command's own output. This can also be requested
24586 by invoking @value{GDBN} with the @option{--statistics} command-line
24587 switch (@pxref{Mode Options}).
24590 @cindex time of command execution
24592 Control whether to display the execution time for each command. If
24593 set to a nonzero value, @value{GDBN} will display how much time it
24594 took to execute each command, following the command's own output.
24595 The time is not printed for the commands that run the target, since
24596 there's no mechanism currently to compute how much time was spend
24597 by @value{GDBN} and how much time was spend by the program been debugged.
24598 it's not possibly currently
24599 This can also be requested by invoking @value{GDBN} with the
24600 @option{--statistics} command-line switch (@pxref{Mode Options}).
24602 @kindex maint translate-address
24603 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
24604 Find the symbol stored at the location specified by the address
24605 @var{addr} and an optional section name @var{section}. If found,
24606 @value{GDBN} prints the name of the closest symbol and an offset from
24607 the symbol's location to the specified address. This is similar to
24608 the @code{info address} command (@pxref{Symbols}), except that this
24609 command also allows to find symbols in other sections.
24613 The following command is useful for non-interactive invocations of
24614 @value{GDBN}, such as in the test suite.
24617 @item set watchdog @var{nsec}
24618 @kindex set watchdog
24619 @cindex watchdog timer
24620 @cindex timeout for commands
24621 Set the maximum number of seconds @value{GDBN} will wait for the
24622 target operation to finish. If this time expires, @value{GDBN}
24623 reports and error and the command is aborted.
24625 @item show watchdog
24626 Show the current setting of the target wait timeout.
24629 @node Remote Protocol
24630 @appendix @value{GDBN} Remote Serial Protocol
24635 * Stop Reply Packets::
24636 * General Query Packets::
24637 * Register Packet Format::
24638 * Tracepoint Packets::
24639 * Host I/O Packets::
24641 * Notification Packets::
24642 * Remote Non-Stop::
24643 * Packet Acknowledgment::
24645 * File-I/O Remote Protocol Extension::
24646 * Library List Format::
24647 * Memory Map Format::
24653 There may be occasions when you need to know something about the
24654 protocol---for example, if there is only one serial port to your target
24655 machine, you might want your program to do something special if it
24656 recognizes a packet meant for @value{GDBN}.
24658 In the examples below, @samp{->} and @samp{<-} are used to indicate
24659 transmitted and received data, respectively.
24661 @cindex protocol, @value{GDBN} remote serial
24662 @cindex serial protocol, @value{GDBN} remote
24663 @cindex remote serial protocol
24664 All @value{GDBN} commands and responses (other than acknowledgments
24665 and notifications, see @ref{Notification Packets}) are sent as a
24666 @var{packet}. A @var{packet} is introduced with the character
24667 @samp{$}, the actual @var{packet-data}, and the terminating character
24668 @samp{#} followed by a two-digit @var{checksum}:
24671 @code{$}@var{packet-data}@code{#}@var{checksum}
24675 @cindex checksum, for @value{GDBN} remote
24677 The two-digit @var{checksum} is computed as the modulo 256 sum of all
24678 characters between the leading @samp{$} and the trailing @samp{#} (an
24679 eight bit unsigned checksum).
24681 Implementors should note that prior to @value{GDBN} 5.0 the protocol
24682 specification also included an optional two-digit @var{sequence-id}:
24685 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
24688 @cindex sequence-id, for @value{GDBN} remote
24690 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
24691 has never output @var{sequence-id}s. Stubs that handle packets added
24692 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
24694 When either the host or the target machine receives a packet, the first
24695 response expected is an acknowledgment: either @samp{+} (to indicate
24696 the package was received correctly) or @samp{-} (to request
24700 -> @code{$}@var{packet-data}@code{#}@var{checksum}
24705 The @samp{+}/@samp{-} acknowledgments can be disabled
24706 once a connection is established.
24707 @xref{Packet Acknowledgment}, for details.
24709 The host (@value{GDBN}) sends @var{command}s, and the target (the
24710 debugging stub incorporated in your program) sends a @var{response}. In
24711 the case of step and continue @var{command}s, the response is only sent
24712 when the operation has completed, and the target has again stopped all
24713 threads in all attached processes. This is the default all-stop mode
24714 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
24715 execution mode; see @ref{Remote Non-Stop}, for details.
24717 @var{packet-data} consists of a sequence of characters with the
24718 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
24721 @cindex remote protocol, field separator
24722 Fields within the packet should be separated using @samp{,} @samp{;} or
24723 @samp{:}. Except where otherwise noted all numbers are represented in
24724 @sc{hex} with leading zeros suppressed.
24726 Implementors should note that prior to @value{GDBN} 5.0, the character
24727 @samp{:} could not appear as the third character in a packet (as it
24728 would potentially conflict with the @var{sequence-id}).
24730 @cindex remote protocol, binary data
24731 @anchor{Binary Data}
24732 Binary data in most packets is encoded either as two hexadecimal
24733 digits per byte of binary data. This allowed the traditional remote
24734 protocol to work over connections which were only seven-bit clean.
24735 Some packets designed more recently assume an eight-bit clean
24736 connection, and use a more efficient encoding to send and receive
24739 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
24740 as an escape character. Any escaped byte is transmitted as the escape
24741 character followed by the original character XORed with @code{0x20}.
24742 For example, the byte @code{0x7d} would be transmitted as the two
24743 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
24744 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
24745 @samp{@}}) must always be escaped. Responses sent by the stub
24746 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
24747 is not interpreted as the start of a run-length encoded sequence
24750 Response @var{data} can be run-length encoded to save space.
24751 Run-length encoding replaces runs of identical characters with one
24752 instance of the repeated character, followed by a @samp{*} and a
24753 repeat count. The repeat count is itself sent encoded, to avoid
24754 binary characters in @var{data}: a value of @var{n} is sent as
24755 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
24756 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
24757 code 32) for a repeat count of 3. (This is because run-length
24758 encoding starts to win for counts 3 or more.) Thus, for example,
24759 @samp{0* } is a run-length encoding of ``0000'': the space character
24760 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
24763 The printable characters @samp{#} and @samp{$} or with a numeric value
24764 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
24765 seven repeats (@samp{$}) can be expanded using a repeat count of only
24766 five (@samp{"}). For example, @samp{00000000} can be encoded as
24769 The error response returned for some packets includes a two character
24770 error number. That number is not well defined.
24772 @cindex empty response, for unsupported packets
24773 For any @var{command} not supported by the stub, an empty response
24774 (@samp{$#00}) should be returned. That way it is possible to extend the
24775 protocol. A newer @value{GDBN} can tell if a packet is supported based
24778 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
24779 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
24785 The following table provides a complete list of all currently defined
24786 @var{command}s and their corresponding response @var{data}.
24787 @xref{File-I/O Remote Protocol Extension}, for details about the File
24788 I/O extension of the remote protocol.
24790 Each packet's description has a template showing the packet's overall
24791 syntax, followed by an explanation of the packet's meaning. We
24792 include spaces in some of the templates for clarity; these are not
24793 part of the packet's syntax. No @value{GDBN} packet uses spaces to
24794 separate its components. For example, a template like @samp{foo
24795 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
24796 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
24797 @var{baz}. @value{GDBN} does not transmit a space character between the
24798 @samp{foo} and the @var{bar}, or between the @var{bar} and the
24801 @cindex @var{thread-id}, in remote protocol
24802 @anchor{thread-id syntax}
24803 Several packets and replies include a @var{thread-id} field to identify
24804 a thread. Normally these are positive numbers with a target-specific
24805 interpretation, formatted as big-endian hex strings. A @var{thread-id}
24806 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
24809 In addition, the remote protocol supports a multiprocess feature in
24810 which the @var{thread-id} syntax is extended to optionally include both
24811 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
24812 The @var{pid} (process) and @var{tid} (thread) components each have the
24813 format described above: a positive number with target-specific
24814 interpretation formatted as a big-endian hex string, literal @samp{-1}
24815 to indicate all processes or threads (respectively), or @samp{0} to
24816 indicate an arbitrary process or thread. Specifying just a process, as
24817 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
24818 error to specify all processes but a specific thread, such as
24819 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
24820 for those packets and replies explicitly documented to include a process
24821 ID, rather than a @var{thread-id}.
24823 The multiprocess @var{thread-id} syntax extensions are only used if both
24824 @value{GDBN} and the stub report support for the @samp{multiprocess}
24825 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
24828 Note that all packet forms beginning with an upper- or lower-case
24829 letter, other than those described here, are reserved for future use.
24831 Here are the packet descriptions.
24836 @cindex @samp{!} packet
24837 @anchor{extended mode}
24838 Enable extended mode. In extended mode, the remote server is made
24839 persistent. The @samp{R} packet is used to restart the program being
24845 The remote target both supports and has enabled extended mode.
24849 @cindex @samp{?} packet
24850 Indicate the reason the target halted. The reply is the same as for
24851 step and continue. This packet has a special interpretation when the
24852 target is in non-stop mode; see @ref{Remote Non-Stop}.
24855 @xref{Stop Reply Packets}, for the reply specifications.
24857 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
24858 @cindex @samp{A} packet
24859 Initialized @code{argv[]} array passed into program. @var{arglen}
24860 specifies the number of bytes in the hex encoded byte stream
24861 @var{arg}. See @code{gdbserver} for more details.
24866 The arguments were set.
24872 @cindex @samp{b} packet
24873 (Don't use this packet; its behavior is not well-defined.)
24874 Change the serial line speed to @var{baud}.
24876 JTC: @emph{When does the transport layer state change? When it's
24877 received, or after the ACK is transmitted. In either case, there are
24878 problems if the command or the acknowledgment packet is dropped.}
24880 Stan: @emph{If people really wanted to add something like this, and get
24881 it working for the first time, they ought to modify ser-unix.c to send
24882 some kind of out-of-band message to a specially-setup stub and have the
24883 switch happen "in between" packets, so that from remote protocol's point
24884 of view, nothing actually happened.}
24886 @item B @var{addr},@var{mode}
24887 @cindex @samp{B} packet
24888 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
24889 breakpoint at @var{addr}.
24891 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
24892 (@pxref{insert breakpoint or watchpoint packet}).
24895 @cindex @samp{bc} packet
24896 Backward continue. Execute the target system in reverse. No parameter.
24897 @xref{Reverse Execution}, for more information.
24900 @xref{Stop Reply Packets}, for the reply specifications.
24903 @cindex @samp{bs} packet
24904 Backward single step. Execute one instruction in reverse. No parameter.
24905 @xref{Reverse Execution}, for more information.
24908 @xref{Stop Reply Packets}, for the reply specifications.
24910 @item c @r{[}@var{addr}@r{]}
24911 @cindex @samp{c} packet
24912 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
24913 resume at current address.
24916 @xref{Stop Reply Packets}, for the reply specifications.
24918 @item C @var{sig}@r{[};@var{addr}@r{]}
24919 @cindex @samp{C} packet
24920 Continue with signal @var{sig} (hex signal number). If
24921 @samp{;@var{addr}} is omitted, resume at same address.
24924 @xref{Stop Reply Packets}, for the reply specifications.
24927 @cindex @samp{d} packet
24930 Don't use this packet; instead, define a general set packet
24931 (@pxref{General Query Packets}).
24935 @cindex @samp{D} packet
24936 The first form of the packet is used to detach @value{GDBN} from the
24937 remote system. It is sent to the remote target
24938 before @value{GDBN} disconnects via the @code{detach} command.
24940 The second form, including a process ID, is used when multiprocess
24941 protocol extensions are enabled (@pxref{multiprocess extensions}), to
24942 detach only a specific process. The @var{pid} is specified as a
24943 big-endian hex string.
24953 @item F @var{RC},@var{EE},@var{CF};@var{XX}
24954 @cindex @samp{F} packet
24955 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
24956 This is part of the File-I/O protocol extension. @xref{File-I/O
24957 Remote Protocol Extension}, for the specification.
24960 @anchor{read registers packet}
24961 @cindex @samp{g} packet
24962 Read general registers.
24966 @item @var{XX@dots{}}
24967 Each byte of register data is described by two hex digits. The bytes
24968 with the register are transmitted in target byte order. The size of
24969 each register and their position within the @samp{g} packet are
24970 determined by the @value{GDBN} internal gdbarch functions
24971 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
24972 specification of several standard @samp{g} packets is specified below.
24977 @item G @var{XX@dots{}}
24978 @cindex @samp{G} packet
24979 Write general registers. @xref{read registers packet}, for a
24980 description of the @var{XX@dots{}} data.
24990 @item H @var{c} @var{thread-id}
24991 @cindex @samp{H} packet
24992 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
24993 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
24994 should be @samp{c} for step and continue operations, @samp{g} for other
24995 operations. The thread designator @var{thread-id} has the format and
24996 interpretation described in @ref{thread-id syntax}.
25007 @c 'H': How restrictive (or permissive) is the thread model. If a
25008 @c thread is selected and stopped, are other threads allowed
25009 @c to continue to execute? As I mentioned above, I think the
25010 @c semantics of each command when a thread is selected must be
25011 @c described. For example:
25013 @c 'g': If the stub supports threads and a specific thread is
25014 @c selected, returns the register block from that thread;
25015 @c otherwise returns current registers.
25017 @c 'G' If the stub supports threads and a specific thread is
25018 @c selected, sets the registers of the register block of
25019 @c that thread; otherwise sets current registers.
25021 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25022 @anchor{cycle step packet}
25023 @cindex @samp{i} packet
25024 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25025 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25026 step starting at that address.
25029 @cindex @samp{I} packet
25030 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25034 @cindex @samp{k} packet
25037 FIXME: @emph{There is no description of how to operate when a specific
25038 thread context has been selected (i.e.@: does 'k' kill only that
25041 @item m @var{addr},@var{length}
25042 @cindex @samp{m} packet
25043 Read @var{length} bytes of memory starting at address @var{addr}.
25044 Note that @var{addr} may not be aligned to any particular boundary.
25046 The stub need not use any particular size or alignment when gathering
25047 data from memory for the response; even if @var{addr} is word-aligned
25048 and @var{length} is a multiple of the word size, the stub is free to
25049 use byte accesses, or not. For this reason, this packet may not be
25050 suitable for accessing memory-mapped I/O devices.
25051 @cindex alignment of remote memory accesses
25052 @cindex size of remote memory accesses
25053 @cindex memory, alignment and size of remote accesses
25057 @item @var{XX@dots{}}
25058 Memory contents; each byte is transmitted as a two-digit hexadecimal
25059 number. The reply may contain fewer bytes than requested if the
25060 server was able to read only part of the region of memory.
25065 @item M @var{addr},@var{length}:@var{XX@dots{}}
25066 @cindex @samp{M} packet
25067 Write @var{length} bytes of memory starting at address @var{addr}.
25068 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25069 hexadecimal number.
25076 for an error (this includes the case where only part of the data was
25081 @cindex @samp{p} packet
25082 Read the value of register @var{n}; @var{n} is in hex.
25083 @xref{read registers packet}, for a description of how the returned
25084 register value is encoded.
25088 @item @var{XX@dots{}}
25089 the register's value
25093 Indicating an unrecognized @var{query}.
25096 @item P @var{n@dots{}}=@var{r@dots{}}
25097 @anchor{write register packet}
25098 @cindex @samp{P} packet
25099 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
25100 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
25101 digits for each byte in the register (target byte order).
25111 @item q @var{name} @var{params}@dots{}
25112 @itemx Q @var{name} @var{params}@dots{}
25113 @cindex @samp{q} packet
25114 @cindex @samp{Q} packet
25115 General query (@samp{q}) and set (@samp{Q}). These packets are
25116 described fully in @ref{General Query Packets}.
25119 @cindex @samp{r} packet
25120 Reset the entire system.
25122 Don't use this packet; use the @samp{R} packet instead.
25125 @cindex @samp{R} packet
25126 Restart the program being debugged. @var{XX}, while needed, is ignored.
25127 This packet is only available in extended mode (@pxref{extended mode}).
25129 The @samp{R} packet has no reply.
25131 @item s @r{[}@var{addr}@r{]}
25132 @cindex @samp{s} packet
25133 Single step. @var{addr} is the address at which to resume. If
25134 @var{addr} is omitted, resume at same address.
25137 @xref{Stop Reply Packets}, for the reply specifications.
25139 @item S @var{sig}@r{[};@var{addr}@r{]}
25140 @anchor{step with signal packet}
25141 @cindex @samp{S} packet
25142 Step with signal. This is analogous to the @samp{C} packet, but
25143 requests a single-step, rather than a normal resumption of execution.
25146 @xref{Stop Reply Packets}, for the reply specifications.
25148 @item t @var{addr}:@var{PP},@var{MM}
25149 @cindex @samp{t} packet
25150 Search backwards starting at address @var{addr} for a match with pattern
25151 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
25152 @var{addr} must be at least 3 digits.
25154 @item T @var{thread-id}
25155 @cindex @samp{T} packet
25156 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
25161 thread is still alive
25167 Packets starting with @samp{v} are identified by a multi-letter name,
25168 up to the first @samp{;} or @samp{?} (or the end of the packet).
25170 @item vAttach;@var{pid}
25171 @cindex @samp{vAttach} packet
25172 Attach to a new process with the specified process ID @var{pid}.
25173 The process ID is a
25174 hexadecimal integer identifying the process. In all-stop mode, all
25175 threads in the attached process are stopped; in non-stop mode, it may be
25176 attached without being stopped if that is supported by the target.
25178 @c In non-stop mode, on a successful vAttach, the stub should set the
25179 @c current thread to a thread of the newly-attached process. After
25180 @c attaching, GDB queries for the attached process's thread ID with qC.
25181 @c Also note that, from a user perspective, whether or not the
25182 @c target is stopped on attach in non-stop mode depends on whether you
25183 @c use the foreground or background version of the attach command, not
25184 @c on what vAttach does; GDB does the right thing with respect to either
25185 @c stopping or restarting threads.
25187 This packet is only available in extended mode (@pxref{extended mode}).
25193 @item @r{Any stop packet}
25194 for success in all-stop mode (@pxref{Stop Reply Packets})
25196 for success in non-stop mode (@pxref{Remote Non-Stop})
25199 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
25200 @cindex @samp{vCont} packet
25201 Resume the inferior, specifying different actions for each thread.
25202 If an action is specified with no @var{thread-id}, then it is applied to any
25203 threads that don't have a specific action specified; if no default action is
25204 specified then other threads should remain stopped in all-stop mode and
25205 in their current state in non-stop mode.
25206 Specifying multiple
25207 default actions is an error; specifying no actions is also an error.
25208 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
25210 Currently supported actions are:
25216 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
25220 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
25224 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
25227 The optional argument @var{addr} normally associated with the
25228 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
25229 not supported in @samp{vCont}.
25231 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
25232 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
25233 A stop reply should be generated for any affected thread not already stopped.
25234 When a thread is stopped by means of a @samp{t} action,
25235 the corresponding stop reply should indicate that the thread has stopped with
25236 signal @samp{0}, regardless of whether the target uses some other signal
25237 as an implementation detail.
25240 @xref{Stop Reply Packets}, for the reply specifications.
25243 @cindex @samp{vCont?} packet
25244 Request a list of actions supported by the @samp{vCont} packet.
25248 @item vCont@r{[};@var{action}@dots{}@r{]}
25249 The @samp{vCont} packet is supported. Each @var{action} is a supported
25250 command in the @samp{vCont} packet.
25252 The @samp{vCont} packet is not supported.
25255 @item vFile:@var{operation}:@var{parameter}@dots{}
25256 @cindex @samp{vFile} packet
25257 Perform a file operation on the target system. For details,
25258 see @ref{Host I/O Packets}.
25260 @item vFlashErase:@var{addr},@var{length}
25261 @cindex @samp{vFlashErase} packet
25262 Direct the stub to erase @var{length} bytes of flash starting at
25263 @var{addr}. The region may enclose any number of flash blocks, but
25264 its start and end must fall on block boundaries, as indicated by the
25265 flash block size appearing in the memory map (@pxref{Memory Map
25266 Format}). @value{GDBN} groups flash memory programming operations
25267 together, and sends a @samp{vFlashDone} request after each group; the
25268 stub is allowed to delay erase operation until the @samp{vFlashDone}
25269 packet is received.
25271 The stub must support @samp{vCont} if it reports support for
25272 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
25273 this case @samp{vCont} actions can be specified to apply to all threads
25274 in a process by using the @samp{p@var{pid}.-1} form of the
25285 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
25286 @cindex @samp{vFlashWrite} packet
25287 Direct the stub to write data to flash address @var{addr}. The data
25288 is passed in binary form using the same encoding as for the @samp{X}
25289 packet (@pxref{Binary Data}). The memory ranges specified by
25290 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
25291 not overlap, and must appear in order of increasing addresses
25292 (although @samp{vFlashErase} packets for higher addresses may already
25293 have been received; the ordering is guaranteed only between
25294 @samp{vFlashWrite} packets). If a packet writes to an address that was
25295 neither erased by a preceding @samp{vFlashErase} packet nor by some other
25296 target-specific method, the results are unpredictable.
25304 for vFlashWrite addressing non-flash memory
25310 @cindex @samp{vFlashDone} packet
25311 Indicate to the stub that flash programming operation is finished.
25312 The stub is permitted to delay or batch the effects of a group of
25313 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
25314 @samp{vFlashDone} packet is received. The contents of the affected
25315 regions of flash memory are unpredictable until the @samp{vFlashDone}
25316 request is completed.
25318 @item vKill;@var{pid}
25319 @cindex @samp{vKill} packet
25320 Kill the process with the specified process ID. @var{pid} is a
25321 hexadecimal integer identifying the process. This packet is used in
25322 preference to @samp{k} when multiprocess protocol extensions are
25323 supported; see @ref{multiprocess extensions}.
25333 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
25334 @cindex @samp{vRun} packet
25335 Run the program @var{filename}, passing it each @var{argument} on its
25336 command line. The file and arguments are hex-encoded strings. If
25337 @var{filename} is an empty string, the stub may use a default program
25338 (e.g.@: the last program run). The program is created in the stopped
25341 @c FIXME: What about non-stop mode?
25343 This packet is only available in extended mode (@pxref{extended mode}).
25349 @item @r{Any stop packet}
25350 for success (@pxref{Stop Reply Packets})
25354 @anchor{vStopped packet}
25355 @cindex @samp{vStopped} packet
25357 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
25358 reply and prompt for the stub to report another one.
25362 @item @r{Any stop packet}
25363 if there is another unreported stop event (@pxref{Stop Reply Packets})
25365 if there are no unreported stop events
25368 @item X @var{addr},@var{length}:@var{XX@dots{}}
25370 @cindex @samp{X} packet
25371 Write data to memory, where the data is transmitted in binary.
25372 @var{addr} is address, @var{length} is number of bytes,
25373 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
25383 @item z @var{type},@var{addr},@var{length}
25384 @itemx Z @var{type},@var{addr},@var{length}
25385 @anchor{insert breakpoint or watchpoint packet}
25386 @cindex @samp{z} packet
25387 @cindex @samp{Z} packets
25388 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
25389 watchpoint starting at address @var{address} and covering the next
25390 @var{length} bytes.
25392 Each breakpoint and watchpoint packet @var{type} is documented
25395 @emph{Implementation notes: A remote target shall return an empty string
25396 for an unrecognized breakpoint or watchpoint packet @var{type}. A
25397 remote target shall support either both or neither of a given
25398 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
25399 avoid potential problems with duplicate packets, the operations should
25400 be implemented in an idempotent way.}
25402 @item z0,@var{addr},@var{length}
25403 @itemx Z0,@var{addr},@var{length}
25404 @cindex @samp{z0} packet
25405 @cindex @samp{Z0} packet
25406 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
25407 @var{addr} of size @var{length}.
25409 A memory breakpoint is implemented by replacing the instruction at
25410 @var{addr} with a software breakpoint or trap instruction. The
25411 @var{length} is used by targets that indicates the size of the
25412 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
25413 @sc{mips} can insert either a 2 or 4 byte breakpoint).
25415 @emph{Implementation note: It is possible for a target to copy or move
25416 code that contains memory breakpoints (e.g., when implementing
25417 overlays). The behavior of this packet, in the presence of such a
25418 target, is not defined.}
25430 @item z1,@var{addr},@var{length}
25431 @itemx Z1,@var{addr},@var{length}
25432 @cindex @samp{z1} packet
25433 @cindex @samp{Z1} packet
25434 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
25435 address @var{addr} of size @var{length}.
25437 A hardware breakpoint is implemented using a mechanism that is not
25438 dependant on being able to modify the target's memory.
25440 @emph{Implementation note: A hardware breakpoint is not affected by code
25453 @item z2,@var{addr},@var{length}
25454 @itemx Z2,@var{addr},@var{length}
25455 @cindex @samp{z2} packet
25456 @cindex @samp{Z2} packet
25457 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
25469 @item z3,@var{addr},@var{length}
25470 @itemx Z3,@var{addr},@var{length}
25471 @cindex @samp{z3} packet
25472 @cindex @samp{Z3} packet
25473 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
25485 @item z4,@var{addr},@var{length}
25486 @itemx Z4,@var{addr},@var{length}
25487 @cindex @samp{z4} packet
25488 @cindex @samp{Z4} packet
25489 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
25503 @node Stop Reply Packets
25504 @section Stop Reply Packets
25505 @cindex stop reply packets
25507 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
25508 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
25509 receive any of the below as a reply. Except for @samp{?}
25510 and @samp{vStopped}, that reply is only returned
25511 when the target halts. In the below the exact meaning of @dfn{signal
25512 number} is defined by the header @file{include/gdb/signals.h} in the
25513 @value{GDBN} source code.
25515 As in the description of request packets, we include spaces in the
25516 reply templates for clarity; these are not part of the reply packet's
25517 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
25523 The program received signal number @var{AA} (a two-digit hexadecimal
25524 number). This is equivalent to a @samp{T} response with no
25525 @var{n}:@var{r} pairs.
25527 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
25528 @cindex @samp{T} packet reply
25529 The program received signal number @var{AA} (a two-digit hexadecimal
25530 number). This is equivalent to an @samp{S} response, except that the
25531 @samp{@var{n}:@var{r}} pairs can carry values of important registers
25532 and other information directly in the stop reply packet, reducing
25533 round-trip latency. Single-step and breakpoint traps are reported
25534 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
25538 If @var{n} is a hexadecimal number, it is a register number, and the
25539 corresponding @var{r} gives that register's value. @var{r} is a
25540 series of bytes in target byte order, with each byte given by a
25541 two-digit hex number.
25544 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
25545 the stopped thread, as specified in @ref{thread-id syntax}.
25548 If @var{n} is a recognized @dfn{stop reason}, it describes a more
25549 specific event that stopped the target. The currently defined stop
25550 reasons are listed below. @var{aa} should be @samp{05}, the trap
25551 signal. At most one stop reason should be present.
25554 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
25555 and go on to the next; this allows us to extend the protocol in the
25559 The currently defined stop reasons are:
25565 The packet indicates a watchpoint hit, and @var{r} is the data address, in
25568 @cindex shared library events, remote reply
25570 The packet indicates that the loaded libraries have changed.
25571 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
25572 list of loaded libraries. @var{r} is ignored.
25574 @cindex replay log events, remote reply
25576 The packet indicates that the target cannot continue replaying
25577 logged execution events, because it has reached the end (or the
25578 beginning when executing backward) of the log. The value of @var{r}
25579 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
25580 for more information.
25586 @itemx W @var{AA} ; process:@var{pid}
25587 The process exited, and @var{AA} is the exit status. This is only
25588 applicable to certain targets.
25590 The second form of the response, including the process ID of the exited
25591 process, can be used only when @value{GDBN} has reported support for
25592 multiprocess protocol extensions; see @ref{multiprocess extensions}.
25593 The @var{pid} is formatted as a big-endian hex string.
25596 @itemx X @var{AA} ; process:@var{pid}
25597 The process terminated with signal @var{AA}.
25599 The second form of the response, including the process ID of the
25600 terminated process, can be used only when @value{GDBN} has reported
25601 support for multiprocess protocol extensions; see @ref{multiprocess
25602 extensions}. The @var{pid} is formatted as a big-endian hex string.
25604 @item O @var{XX}@dots{}
25605 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
25606 written as the program's console output. This can happen at any time
25607 while the program is running and the debugger should continue to wait
25608 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
25610 @item F @var{call-id},@var{parameter}@dots{}
25611 @var{call-id} is the identifier which says which host system call should
25612 be called. This is just the name of the function. Translation into the
25613 correct system call is only applicable as it's defined in @value{GDBN}.
25614 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
25617 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
25618 this very system call.
25620 The target replies with this packet when it expects @value{GDBN} to
25621 call a host system call on behalf of the target. @value{GDBN} replies
25622 with an appropriate @samp{F} packet and keeps up waiting for the next
25623 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
25624 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
25625 Protocol Extension}, for more details.
25629 @node General Query Packets
25630 @section General Query Packets
25631 @cindex remote query requests
25633 Packets starting with @samp{q} are @dfn{general query packets};
25634 packets starting with @samp{Q} are @dfn{general set packets}. General
25635 query and set packets are a semi-unified form for retrieving and
25636 sending information to and from the stub.
25638 The initial letter of a query or set packet is followed by a name
25639 indicating what sort of thing the packet applies to. For example,
25640 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
25641 definitions with the stub. These packet names follow some
25646 The name must not contain commas, colons or semicolons.
25648 Most @value{GDBN} query and set packets have a leading upper case
25651 The names of custom vendor packets should use a company prefix, in
25652 lower case, followed by a period. For example, packets designed at
25653 the Acme Corporation might begin with @samp{qacme.foo} (for querying
25654 foos) or @samp{Qacme.bar} (for setting bars).
25657 The name of a query or set packet should be separated from any
25658 parameters by a @samp{:}; the parameters themselves should be
25659 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
25660 full packet name, and check for a separator or the end of the packet,
25661 in case two packet names share a common prefix. New packets should not begin
25662 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
25663 packets predate these conventions, and have arguments without any terminator
25664 for the packet name; we suspect they are in widespread use in places that
25665 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
25666 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
25669 Like the descriptions of the other packets, each description here
25670 has a template showing the packet's overall syntax, followed by an
25671 explanation of the packet's meaning. We include spaces in some of the
25672 templates for clarity; these are not part of the packet's syntax. No
25673 @value{GDBN} packet uses spaces to separate its components.
25675 Here are the currently defined query and set packets:
25680 @cindex current thread, remote request
25681 @cindex @samp{qC} packet
25682 Return the current thread ID.
25686 @item QC @var{thread-id}
25687 Where @var{thread-id} is a thread ID as documented in
25688 @ref{thread-id syntax}.
25689 @item @r{(anything else)}
25690 Any other reply implies the old thread ID.
25693 @item qCRC:@var{addr},@var{length}
25694 @cindex CRC of memory block, remote request
25695 @cindex @samp{qCRC} packet
25696 Compute the CRC checksum of a block of memory.
25700 An error (such as memory fault)
25701 @item C @var{crc32}
25702 The specified memory region's checksum is @var{crc32}.
25706 @itemx qsThreadInfo
25707 @cindex list active threads, remote request
25708 @cindex @samp{qfThreadInfo} packet
25709 @cindex @samp{qsThreadInfo} packet
25710 Obtain a list of all active thread IDs from the target (OS). Since there
25711 may be too many active threads to fit into one reply packet, this query
25712 works iteratively: it may require more than one query/reply sequence to
25713 obtain the entire list of threads. The first query of the sequence will
25714 be the @samp{qfThreadInfo} query; subsequent queries in the
25715 sequence will be the @samp{qsThreadInfo} query.
25717 NOTE: This packet replaces the @samp{qL} query (see below).
25721 @item m @var{thread-id}
25723 @item m @var{thread-id},@var{thread-id}@dots{}
25724 a comma-separated list of thread IDs
25726 (lower case letter @samp{L}) denotes end of list.
25729 In response to each query, the target will reply with a list of one or
25730 more thread IDs, separated by commas.
25731 @value{GDBN} will respond to each reply with a request for more thread
25732 ids (using the @samp{qs} form of the query), until the target responds
25733 with @samp{l} (lower-case el, for @dfn{last}).
25734 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
25737 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
25738 @cindex get thread-local storage address, remote request
25739 @cindex @samp{qGetTLSAddr} packet
25740 Fetch the address associated with thread local storage specified
25741 by @var{thread-id}, @var{offset}, and @var{lm}.
25743 @var{thread-id} is the thread ID associated with the
25744 thread for which to fetch the TLS address. @xref{thread-id syntax}.
25746 @var{offset} is the (big endian, hex encoded) offset associated with the
25747 thread local variable. (This offset is obtained from the debug
25748 information associated with the variable.)
25750 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
25751 the load module associated with the thread local storage. For example,
25752 a @sc{gnu}/Linux system will pass the link map address of the shared
25753 object associated with the thread local storage under consideration.
25754 Other operating environments may choose to represent the load module
25755 differently, so the precise meaning of this parameter will vary.
25759 @item @var{XX}@dots{}
25760 Hex encoded (big endian) bytes representing the address of the thread
25761 local storage requested.
25764 An error occurred. @var{nn} are hex digits.
25767 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
25770 @item qL @var{startflag} @var{threadcount} @var{nextthread}
25771 Obtain thread information from RTOS. Where: @var{startflag} (one hex
25772 digit) is one to indicate the first query and zero to indicate a
25773 subsequent query; @var{threadcount} (two hex digits) is the maximum
25774 number of threads the response packet can contain; and @var{nextthread}
25775 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
25776 returned in the response as @var{argthread}.
25778 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
25782 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
25783 Where: @var{count} (two hex digits) is the number of threads being
25784 returned; @var{done} (one hex digit) is zero to indicate more threads
25785 and one indicates no further threads; @var{argthreadid} (eight hex
25786 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
25787 is a sequence of thread IDs from the target. @var{threadid} (eight hex
25788 digits). See @code{remote.c:parse_threadlist_response()}.
25792 @cindex section offsets, remote request
25793 @cindex @samp{qOffsets} packet
25794 Get section offsets that the target used when relocating the downloaded
25799 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
25800 Relocate the @code{Text} section by @var{xxx} from its original address.
25801 Relocate the @code{Data} section by @var{yyy} from its original address.
25802 If the object file format provides segment information (e.g.@: @sc{elf}
25803 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
25804 segments by the supplied offsets.
25806 @emph{Note: while a @code{Bss} offset may be included in the response,
25807 @value{GDBN} ignores this and instead applies the @code{Data} offset
25808 to the @code{Bss} section.}
25810 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
25811 Relocate the first segment of the object file, which conventionally
25812 contains program code, to a starting address of @var{xxx}. If
25813 @samp{DataSeg} is specified, relocate the second segment, which
25814 conventionally contains modifiable data, to a starting address of
25815 @var{yyy}. @value{GDBN} will report an error if the object file
25816 does not contain segment information, or does not contain at least
25817 as many segments as mentioned in the reply. Extra segments are
25818 kept at fixed offsets relative to the last relocated segment.
25821 @item qP @var{mode} @var{thread-id}
25822 @cindex thread information, remote request
25823 @cindex @samp{qP} packet
25824 Returns information on @var{thread-id}. Where: @var{mode} is a hex
25825 encoded 32 bit mode; @var{thread-id} is a thread ID
25826 (@pxref{thread-id syntax}).
25828 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
25831 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
25835 @cindex non-stop mode, remote request
25836 @cindex @samp{QNonStop} packet
25838 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
25839 @xref{Remote Non-Stop}, for more information.
25844 The request succeeded.
25847 An error occurred. @var{nn} are hex digits.
25850 An empty reply indicates that @samp{QNonStop} is not supported by
25854 This packet is not probed by default; the remote stub must request it,
25855 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25856 Use of this packet is controlled by the @code{set non-stop} command;
25857 @pxref{Non-Stop Mode}.
25859 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
25860 @cindex pass signals to inferior, remote request
25861 @cindex @samp{QPassSignals} packet
25862 @anchor{QPassSignals}
25863 Each listed @var{signal} should be passed directly to the inferior process.
25864 Signals are numbered identically to continue packets and stop replies
25865 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
25866 strictly greater than the previous item. These signals do not need to stop
25867 the inferior, or be reported to @value{GDBN}. All other signals should be
25868 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
25869 combine; any earlier @samp{QPassSignals} list is completely replaced by the
25870 new list. This packet improves performance when using @samp{handle
25871 @var{signal} nostop noprint pass}.
25876 The request succeeded.
25879 An error occurred. @var{nn} are hex digits.
25882 An empty reply indicates that @samp{QPassSignals} is not supported by
25886 Use of this packet is controlled by the @code{set remote pass-signals}
25887 command (@pxref{Remote Configuration, set remote pass-signals}).
25888 This packet is not probed by default; the remote stub must request it,
25889 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25891 @item qRcmd,@var{command}
25892 @cindex execute remote command, remote request
25893 @cindex @samp{qRcmd} packet
25894 @var{command} (hex encoded) is passed to the local interpreter for
25895 execution. Invalid commands should be reported using the output
25896 string. Before the final result packet, the target may also respond
25897 with a number of intermediate @samp{O@var{output}} console output
25898 packets. @emph{Implementors should note that providing access to a
25899 stubs's interpreter may have security implications}.
25904 A command response with no output.
25906 A command response with the hex encoded output string @var{OUTPUT}.
25908 Indicate a badly formed request.
25910 An empty reply indicates that @samp{qRcmd} is not recognized.
25913 (Note that the @code{qRcmd} packet's name is separated from the
25914 command by a @samp{,}, not a @samp{:}, contrary to the naming
25915 conventions above. Please don't use this packet as a model for new
25918 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
25919 @cindex searching memory, in remote debugging
25920 @cindex @samp{qSearch:memory} packet
25921 @anchor{qSearch memory}
25922 Search @var{length} bytes at @var{address} for @var{search-pattern}.
25923 @var{address} and @var{length} are encoded in hex.
25924 @var{search-pattern} is a sequence of bytes, hex encoded.
25929 The pattern was not found.
25931 The pattern was found at @var{address}.
25933 A badly formed request or an error was encountered while searching memory.
25935 An empty reply indicates that @samp{qSearch:memory} is not recognized.
25938 @item QStartNoAckMode
25939 @cindex @samp{QStartNoAckMode} packet
25940 @anchor{QStartNoAckMode}
25941 Request that the remote stub disable the normal @samp{+}/@samp{-}
25942 protocol acknowledgments (@pxref{Packet Acknowledgment}).
25947 The stub has switched to no-acknowledgment mode.
25948 @value{GDBN} acknowledges this reponse,
25949 but neither the stub nor @value{GDBN} shall send or expect further
25950 @samp{+}/@samp{-} acknowledgments in the current connection.
25952 An empty reply indicates that the stub does not support no-acknowledgment mode.
25955 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
25956 @cindex supported packets, remote query
25957 @cindex features of the remote protocol
25958 @cindex @samp{qSupported} packet
25959 @anchor{qSupported}
25960 Tell the remote stub about features supported by @value{GDBN}, and
25961 query the stub for features it supports. This packet allows
25962 @value{GDBN} and the remote stub to take advantage of each others'
25963 features. @samp{qSupported} also consolidates multiple feature probes
25964 at startup, to improve @value{GDBN} performance---a single larger
25965 packet performs better than multiple smaller probe packets on
25966 high-latency links. Some features may enable behavior which must not
25967 be on by default, e.g.@: because it would confuse older clients or
25968 stubs. Other features may describe packets which could be
25969 automatically probed for, but are not. These features must be
25970 reported before @value{GDBN} will use them. This ``default
25971 unsupported'' behavior is not appropriate for all packets, but it
25972 helps to keep the initial connection time under control with new
25973 versions of @value{GDBN} which support increasing numbers of packets.
25977 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
25978 The stub supports or does not support each returned @var{stubfeature},
25979 depending on the form of each @var{stubfeature} (see below for the
25982 An empty reply indicates that @samp{qSupported} is not recognized,
25983 or that no features needed to be reported to @value{GDBN}.
25986 The allowed forms for each feature (either a @var{gdbfeature} in the
25987 @samp{qSupported} packet, or a @var{stubfeature} in the response)
25991 @item @var{name}=@var{value}
25992 The remote protocol feature @var{name} is supported, and associated
25993 with the specified @var{value}. The format of @var{value} depends
25994 on the feature, but it must not include a semicolon.
25996 The remote protocol feature @var{name} is supported, and does not
25997 need an associated value.
25999 The remote protocol feature @var{name} is not supported.
26001 The remote protocol feature @var{name} may be supported, and
26002 @value{GDBN} should auto-detect support in some other way when it is
26003 needed. This form will not be used for @var{gdbfeature} notifications,
26004 but may be used for @var{stubfeature} responses.
26007 Whenever the stub receives a @samp{qSupported} request, the
26008 supplied set of @value{GDBN} features should override any previous
26009 request. This allows @value{GDBN} to put the stub in a known
26010 state, even if the stub had previously been communicating with
26011 a different version of @value{GDBN}.
26013 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26018 This feature indicates whether @value{GDBN} supports multiprocess
26019 extensions to the remote protocol. @value{GDBN} does not use such
26020 extensions unless the stub also reports that it supports them by
26021 including @samp{multiprocess+} in its @samp{qSupported} reply.
26022 @xref{multiprocess extensions}, for details.
26025 Stubs should ignore any unknown values for
26026 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26027 packet supports receiving packets of unlimited length (earlier
26028 versions of @value{GDBN} may reject overly long responses). Additional values
26029 for @var{gdbfeature} may be defined in the future to let the stub take
26030 advantage of new features in @value{GDBN}, e.g.@: incompatible
26031 improvements in the remote protocol---the @samp{multiprocess} feature is
26032 an example of such a feature. The stub's reply should be independent
26033 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26034 describes all the features it supports, and then the stub replies with
26035 all the features it supports.
26037 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26038 responses, as long as each response uses one of the standard forms.
26040 Some features are flags. A stub which supports a flag feature
26041 should respond with a @samp{+} form response. Other features
26042 require values, and the stub should respond with an @samp{=}
26045 Each feature has a default value, which @value{GDBN} will use if
26046 @samp{qSupported} is not available or if the feature is not mentioned
26047 in the @samp{qSupported} response. The default values are fixed; a
26048 stub is free to omit any feature responses that match the defaults.
26050 Not all features can be probed, but for those which can, the probing
26051 mechanism is useful: in some cases, a stub's internal
26052 architecture may not allow the protocol layer to know some information
26053 about the underlying target in advance. This is especially common in
26054 stubs which may be configured for multiple targets.
26056 These are the currently defined stub features and their properties:
26058 @multitable @columnfractions 0.35 0.2 0.12 0.2
26059 @c NOTE: The first row should be @headitem, but we do not yet require
26060 @c a new enough version of Texinfo (4.7) to use @headitem.
26062 @tab Value Required
26066 @item @samp{PacketSize}
26071 @item @samp{qXfer:auxv:read}
26076 @item @samp{qXfer:features:read}
26081 @item @samp{qXfer:libraries:read}
26086 @item @samp{qXfer:memory-map:read}
26091 @item @samp{qXfer:spu:read}
26096 @item @samp{qXfer:spu:write}
26101 @item @samp{QNonStop}
26106 @item @samp{QPassSignals}
26111 @item @samp{QStartNoAckMode}
26116 @item @samp{multiprocess}
26123 These are the currently defined stub features, in more detail:
26126 @cindex packet size, remote protocol
26127 @item PacketSize=@var{bytes}
26128 The remote stub can accept packets up to at least @var{bytes} in
26129 length. @value{GDBN} will send packets up to this size for bulk
26130 transfers, and will never send larger packets. This is a limit on the
26131 data characters in the packet, including the frame and checksum.
26132 There is no trailing NUL byte in a remote protocol packet; if the stub
26133 stores packets in a NUL-terminated format, it should allow an extra
26134 byte in its buffer for the NUL. If this stub feature is not supported,
26135 @value{GDBN} guesses based on the size of the @samp{g} packet response.
26137 @item qXfer:auxv:read
26138 The remote stub understands the @samp{qXfer:auxv:read} packet
26139 (@pxref{qXfer auxiliary vector read}).
26141 @item qXfer:features:read
26142 The remote stub understands the @samp{qXfer:features:read} packet
26143 (@pxref{qXfer target description read}).
26145 @item qXfer:libraries:read
26146 The remote stub understands the @samp{qXfer:libraries:read} packet
26147 (@pxref{qXfer library list read}).
26149 @item qXfer:memory-map:read
26150 The remote stub understands the @samp{qXfer:memory-map:read} packet
26151 (@pxref{qXfer memory map read}).
26153 @item qXfer:spu:read
26154 The remote stub understands the @samp{qXfer:spu:read} packet
26155 (@pxref{qXfer spu read}).
26157 @item qXfer:spu:write
26158 The remote stub understands the @samp{qXfer:spu:write} packet
26159 (@pxref{qXfer spu write}).
26162 The remote stub understands the @samp{QNonStop} packet
26163 (@pxref{QNonStop}).
26166 The remote stub understands the @samp{QPassSignals} packet
26167 (@pxref{QPassSignals}).
26169 @item QStartNoAckMode
26170 The remote stub understands the @samp{QStartNoAckMode} packet and
26171 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
26174 @anchor{multiprocess extensions}
26175 @cindex multiprocess extensions, in remote protocol
26176 The remote stub understands the multiprocess extensions to the remote
26177 protocol syntax. The multiprocess extensions affect the syntax of
26178 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
26179 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
26180 replies. Note that reporting this feature indicates support for the
26181 syntactic extensions only, not that the stub necessarily supports
26182 debugging of more than one process at a time. The stub must not use
26183 multiprocess extensions in packet replies unless @value{GDBN} has also
26184 indicated it supports them in its @samp{qSupported} request.
26189 @cindex symbol lookup, remote request
26190 @cindex @samp{qSymbol} packet
26191 Notify the target that @value{GDBN} is prepared to serve symbol lookup
26192 requests. Accept requests from the target for the values of symbols.
26197 The target does not need to look up any (more) symbols.
26198 @item qSymbol:@var{sym_name}
26199 The target requests the value of symbol @var{sym_name} (hex encoded).
26200 @value{GDBN} may provide the value by using the
26201 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
26205 @item qSymbol:@var{sym_value}:@var{sym_name}
26206 Set the value of @var{sym_name} to @var{sym_value}.
26208 @var{sym_name} (hex encoded) is the name of a symbol whose value the
26209 target has previously requested.
26211 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
26212 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
26218 The target does not need to look up any (more) symbols.
26219 @item qSymbol:@var{sym_name}
26220 The target requests the value of a new symbol @var{sym_name} (hex
26221 encoded). @value{GDBN} will continue to supply the values of symbols
26222 (if available), until the target ceases to request them.
26227 @xref{Tracepoint Packets}.
26229 @item qThreadExtraInfo,@var{thread-id}
26230 @cindex thread attributes info, remote request
26231 @cindex @samp{qThreadExtraInfo} packet
26232 Obtain a printable string description of a thread's attributes from
26233 the target OS. @var{thread-id} is a thread ID;
26234 see @ref{thread-id syntax}. This
26235 string may contain anything that the target OS thinks is interesting
26236 for @value{GDBN} to tell the user about the thread. The string is
26237 displayed in @value{GDBN}'s @code{info threads} display. Some
26238 examples of possible thread extra info strings are @samp{Runnable}, or
26239 @samp{Blocked on Mutex}.
26243 @item @var{XX}@dots{}
26244 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
26245 comprising the printable string containing the extra information about
26246 the thread's attributes.
26249 (Note that the @code{qThreadExtraInfo} packet's name is separated from
26250 the command by a @samp{,}, not a @samp{:}, contrary to the naming
26251 conventions above. Please don't use this packet as a model for new
26259 @xref{Tracepoint Packets}.
26261 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
26262 @cindex read special object, remote request
26263 @cindex @samp{qXfer} packet
26264 @anchor{qXfer read}
26265 Read uninterpreted bytes from the target's special data area
26266 identified by the keyword @var{object}. Request @var{length} bytes
26267 starting at @var{offset} bytes into the data. The content and
26268 encoding of @var{annex} is specific to @var{object}; it can supply
26269 additional details about what data to access.
26271 Here are the specific requests of this form defined so far. All
26272 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
26273 formats, listed below.
26276 @item qXfer:auxv:read::@var{offset},@var{length}
26277 @anchor{qXfer auxiliary vector read}
26278 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
26279 auxiliary vector}. Note @var{annex} must be empty.
26281 This packet is not probed by default; the remote stub must request it,
26282 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26284 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
26285 @anchor{qXfer target description read}
26286 Access the @dfn{target description}. @xref{Target Descriptions}. The
26287 annex specifies which XML document to access. The main description is
26288 always loaded from the @samp{target.xml} annex.
26290 This packet is not probed by default; the remote stub must request it,
26291 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26293 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
26294 @anchor{qXfer library list read}
26295 Access the target's list of loaded libraries. @xref{Library List Format}.
26296 The annex part of the generic @samp{qXfer} packet must be empty
26297 (@pxref{qXfer read}).
26299 Targets which maintain a list of libraries in the program's memory do
26300 not need to implement this packet; it is designed for platforms where
26301 the operating system manages the list of loaded libraries.
26303 This packet is not probed by default; the remote stub must request it,
26304 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26306 @item qXfer:memory-map:read::@var{offset},@var{length}
26307 @anchor{qXfer memory map read}
26308 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
26309 annex part of the generic @samp{qXfer} packet must be empty
26310 (@pxref{qXfer read}).
26312 This packet is not probed by default; the remote stub must request it,
26313 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26315 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
26316 @anchor{qXfer spu read}
26317 Read contents of an @code{spufs} file on the target system. The
26318 annex specifies which file to read; it must be of the form
26319 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26320 in the target process, and @var{name} identifes the @code{spufs} file
26321 in that context to be accessed.
26323 This packet is not probed by default; the remote stub must request it,
26324 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26330 Data @var{data} (@pxref{Binary Data}) has been read from the
26331 target. There may be more data at a higher address (although
26332 it is permitted to return @samp{m} even for the last valid
26333 block of data, as long as at least one byte of data was read).
26334 @var{data} may have fewer bytes than the @var{length} in the
26338 Data @var{data} (@pxref{Binary Data}) has been read from the target.
26339 There is no more data to be read. @var{data} may have fewer bytes
26340 than the @var{length} in the request.
26343 The @var{offset} in the request is at the end of the data.
26344 There is no more data to be read.
26347 The request was malformed, or @var{annex} was invalid.
26350 The offset was invalid, or there was an error encountered reading the data.
26351 @var{nn} is a hex-encoded @code{errno} value.
26354 An empty reply indicates the @var{object} string was not recognized by
26355 the stub, or that the object does not support reading.
26358 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26359 @cindex write data into object, remote request
26360 Write uninterpreted bytes into the target's special data area
26361 identified by the keyword @var{object}, starting at @var{offset} bytes
26362 into the data. @var{data}@dots{} is the binary-encoded data
26363 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
26364 is specific to @var{object}; it can supply additional details about what data
26367 Here are the specific requests of this form defined so far. All
26368 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
26369 formats, listed below.
26372 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26373 @anchor{qXfer spu write}
26374 Write @var{data} to an @code{spufs} file on the target system. The
26375 annex specifies which file to write; it must be of the form
26376 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26377 in the target process, and @var{name} identifes the @code{spufs} file
26378 in that context to be accessed.
26380 This packet is not probed by default; the remote stub must request it,
26381 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26387 @var{nn} (hex encoded) is the number of bytes written.
26388 This may be fewer bytes than supplied in the request.
26391 The request was malformed, or @var{annex} was invalid.
26394 The offset was invalid, or there was an error encountered writing the data.
26395 @var{nn} is a hex-encoded @code{errno} value.
26398 An empty reply indicates the @var{object} string was not
26399 recognized by the stub, or that the object does not support writing.
26402 @item qXfer:@var{object}:@var{operation}:@dots{}
26403 Requests of this form may be added in the future. When a stub does
26404 not recognize the @var{object} keyword, or its support for
26405 @var{object} does not recognize the @var{operation} keyword, the stub
26406 must respond with an empty packet.
26410 @node Register Packet Format
26411 @section Register Packet Format
26413 The following @code{g}/@code{G} packets have previously been defined.
26414 In the below, some thirty-two bit registers are transferred as
26415 sixty-four bits. Those registers should be zero/sign extended (which?)
26416 to fill the space allocated. Register bytes are transferred in target
26417 byte order. The two nibbles within a register byte are transferred
26418 most-significant - least-significant.
26424 All registers are transferred as thirty-two bit quantities in the order:
26425 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
26426 registers; fsr; fir; fp.
26430 All registers are transferred as sixty-four bit quantities (including
26431 thirty-two bit registers such as @code{sr}). The ordering is the same
26436 @node Tracepoint Packets
26437 @section Tracepoint Packets
26438 @cindex tracepoint packets
26439 @cindex packets, tracepoint
26441 Here we describe the packets @value{GDBN} uses to implement
26442 tracepoints (@pxref{Tracepoints}).
26446 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
26447 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
26448 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
26449 the tracepoint is disabled. @var{step} is the tracepoint's step
26450 count, and @var{pass} is its pass count. If the trailing @samp{-} is
26451 present, further @samp{QTDP} packets will follow to specify this
26452 tracepoint's actions.
26457 The packet was understood and carried out.
26459 The packet was not recognized.
26462 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
26463 Define actions to be taken when a tracepoint is hit. @var{n} and
26464 @var{addr} must be the same as in the initial @samp{QTDP} packet for
26465 this tracepoint. This packet may only be sent immediately after
26466 another @samp{QTDP} packet that ended with a @samp{-}. If the
26467 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
26468 specifying more actions for this tracepoint.
26470 In the series of action packets for a given tracepoint, at most one
26471 can have an @samp{S} before its first @var{action}. If such a packet
26472 is sent, it and the following packets define ``while-stepping''
26473 actions. Any prior packets define ordinary actions --- that is, those
26474 taken when the tracepoint is first hit. If no action packet has an
26475 @samp{S}, then all the packets in the series specify ordinary
26476 tracepoint actions.
26478 The @samp{@var{action}@dots{}} portion of the packet is a series of
26479 actions, concatenated without separators. Each action has one of the
26485 Collect the registers whose bits are set in @var{mask}. @var{mask} is
26486 a hexadecimal number whose @var{i}'th bit is set if register number
26487 @var{i} should be collected. (The least significant bit is numbered
26488 zero.) Note that @var{mask} may be any number of digits long; it may
26489 not fit in a 32-bit word.
26491 @item M @var{basereg},@var{offset},@var{len}
26492 Collect @var{len} bytes of memory starting at the address in register
26493 number @var{basereg}, plus @var{offset}. If @var{basereg} is
26494 @samp{-1}, then the range has a fixed address: @var{offset} is the
26495 address of the lowest byte to collect. The @var{basereg},
26496 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
26497 values (the @samp{-1} value for @var{basereg} is a special case).
26499 @item X @var{len},@var{expr}
26500 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
26501 it directs. @var{expr} is an agent expression, as described in
26502 @ref{Agent Expressions}. Each byte of the expression is encoded as a
26503 two-digit hex number in the packet; @var{len} is the number of bytes
26504 in the expression (and thus one-half the number of hex digits in the
26509 Any number of actions may be packed together in a single @samp{QTDP}
26510 packet, as long as the packet does not exceed the maximum packet
26511 length (400 bytes, for many stubs). There may be only one @samp{R}
26512 action per tracepoint, and it must precede any @samp{M} or @samp{X}
26513 actions. Any registers referred to by @samp{M} and @samp{X} actions
26514 must be collected by a preceding @samp{R} action. (The
26515 ``while-stepping'' actions are treated as if they were attached to a
26516 separate tracepoint, as far as these restrictions are concerned.)
26521 The packet was understood and carried out.
26523 The packet was not recognized.
26526 @item QTFrame:@var{n}
26527 Select the @var{n}'th tracepoint frame from the buffer, and use the
26528 register and memory contents recorded there to answer subsequent
26529 request packets from @value{GDBN}.
26531 A successful reply from the stub indicates that the stub has found the
26532 requested frame. The response is a series of parts, concatenated
26533 without separators, describing the frame we selected. Each part has
26534 one of the following forms:
26538 The selected frame is number @var{n} in the trace frame buffer;
26539 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
26540 was no frame matching the criteria in the request packet.
26543 The selected trace frame records a hit of tracepoint number @var{t};
26544 @var{t} is a hexadecimal number.
26548 @item QTFrame:pc:@var{addr}
26549 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26550 currently selected frame whose PC is @var{addr};
26551 @var{addr} is a hexadecimal number.
26553 @item QTFrame:tdp:@var{t}
26554 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26555 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
26556 is a hexadecimal number.
26558 @item QTFrame:range:@var{start}:@var{end}
26559 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26560 currently selected frame whose PC is between @var{start} (inclusive)
26561 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
26564 @item QTFrame:outside:@var{start}:@var{end}
26565 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
26566 frame @emph{outside} the given range of addresses.
26569 Begin the tracepoint experiment. Begin collecting data from tracepoint
26570 hits in the trace frame buffer.
26573 End the tracepoint experiment. Stop collecting trace frames.
26576 Clear the table of tracepoints, and empty the trace frame buffer.
26578 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
26579 Establish the given ranges of memory as ``transparent''. The stub
26580 will answer requests for these ranges from memory's current contents,
26581 if they were not collected as part of the tracepoint hit.
26583 @value{GDBN} uses this to mark read-only regions of memory, like those
26584 containing program code. Since these areas never change, they should
26585 still have the same contents they did when the tracepoint was hit, so
26586 there's no reason for the stub to refuse to provide their contents.
26589 Ask the stub if there is a trace experiment running right now.
26594 There is no trace experiment running.
26596 There is a trace experiment running.
26602 @node Host I/O Packets
26603 @section Host I/O Packets
26604 @cindex Host I/O, remote protocol
26605 @cindex file transfer, remote protocol
26607 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
26608 operations on the far side of a remote link. For example, Host I/O is
26609 used to upload and download files to a remote target with its own
26610 filesystem. Host I/O uses the same constant values and data structure
26611 layout as the target-initiated File-I/O protocol. However, the
26612 Host I/O packets are structured differently. The target-initiated
26613 protocol relies on target memory to store parameters and buffers.
26614 Host I/O requests are initiated by @value{GDBN}, and the
26615 target's memory is not involved. @xref{File-I/O Remote Protocol
26616 Extension}, for more details on the target-initiated protocol.
26618 The Host I/O request packets all encode a single operation along with
26619 its arguments. They have this format:
26623 @item vFile:@var{operation}: @var{parameter}@dots{}
26624 @var{operation} is the name of the particular request; the target
26625 should compare the entire packet name up to the second colon when checking
26626 for a supported operation. The format of @var{parameter} depends on
26627 the operation. Numbers are always passed in hexadecimal. Negative
26628 numbers have an explicit minus sign (i.e.@: two's complement is not
26629 used). Strings (e.g.@: filenames) are encoded as a series of
26630 hexadecimal bytes. The last argument to a system call may be a
26631 buffer of escaped binary data (@pxref{Binary Data}).
26635 The valid responses to Host I/O packets are:
26639 @item F @var{result} [, @var{errno}] [; @var{attachment}]
26640 @var{result} is the integer value returned by this operation, usually
26641 non-negative for success and -1 for errors. If an error has occured,
26642 @var{errno} will be included in the result. @var{errno} will have a
26643 value defined by the File-I/O protocol (@pxref{Errno Values}). For
26644 operations which return data, @var{attachment} supplies the data as a
26645 binary buffer. Binary buffers in response packets are escaped in the
26646 normal way (@pxref{Binary Data}). See the individual packet
26647 documentation for the interpretation of @var{result} and
26651 An empty response indicates that this operation is not recognized.
26655 These are the supported Host I/O operations:
26658 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
26659 Open a file at @var{pathname} and return a file descriptor for it, or
26660 return -1 if an error occurs. @var{pathname} is a string,
26661 @var{flags} is an integer indicating a mask of open flags
26662 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
26663 of mode bits to use if the file is created (@pxref{mode_t Values}).
26664 @xref{open}, for details of the open flags and mode values.
26666 @item vFile:close: @var{fd}
26667 Close the open file corresponding to @var{fd} and return 0, or
26668 -1 if an error occurs.
26670 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
26671 Read data from the open file corresponding to @var{fd}. Up to
26672 @var{count} bytes will be read from the file, starting at @var{offset}
26673 relative to the start of the file. The target may read fewer bytes;
26674 common reasons include packet size limits and an end-of-file
26675 condition. The number of bytes read is returned. Zero should only be
26676 returned for a successful read at the end of the file, or if
26677 @var{count} was zero.
26679 The data read should be returned as a binary attachment on success.
26680 If zero bytes were read, the response should include an empty binary
26681 attachment (i.e.@: a trailing semicolon). The return value is the
26682 number of target bytes read; the binary attachment may be longer if
26683 some characters were escaped.
26685 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
26686 Write @var{data} (a binary buffer) to the open file corresponding
26687 to @var{fd}. Start the write at @var{offset} from the start of the
26688 file. Unlike many @code{write} system calls, there is no
26689 separate @var{count} argument; the length of @var{data} in the
26690 packet is used. @samp{vFile:write} returns the number of bytes written,
26691 which may be shorter than the length of @var{data}, or -1 if an
26694 @item vFile:unlink: @var{pathname}
26695 Delete the file at @var{pathname} on the target. Return 0,
26696 or -1 if an error occurs. @var{pathname} is a string.
26701 @section Interrupts
26702 @cindex interrupts (remote protocol)
26704 When a program on the remote target is running, @value{GDBN} may
26705 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
26706 control of which is specified via @value{GDBN}'s @samp{remotebreak}
26707 setting (@pxref{set remotebreak}).
26709 The precise meaning of @code{BREAK} is defined by the transport
26710 mechanism and may, in fact, be undefined. @value{GDBN} does not
26711 currently define a @code{BREAK} mechanism for any of the network
26712 interfaces except for TCP, in which case @value{GDBN} sends the
26713 @code{telnet} BREAK sequence.
26715 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
26716 transport mechanisms. It is represented by sending the single byte
26717 @code{0x03} without any of the usual packet overhead described in
26718 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
26719 transmitted as part of a packet, it is considered to be packet data
26720 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
26721 (@pxref{X packet}), used for binary downloads, may include an unescaped
26722 @code{0x03} as part of its packet.
26724 Stubs are not required to recognize these interrupt mechanisms and the
26725 precise meaning associated with receipt of the interrupt is
26726 implementation defined. If the target supports debugging of multiple
26727 threads and/or processes, it should attempt to interrupt all
26728 currently-executing threads and processes.
26729 If the stub is successful at interrupting the
26730 running program, it should send one of the stop
26731 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
26732 of successfully stopping the program in all-stop mode, and a stop reply
26733 for each stopped thread in non-stop mode.
26734 Interrupts received while the
26735 program is stopped are discarded.
26737 @node Notification Packets
26738 @section Notification Packets
26739 @cindex notification packets
26740 @cindex packets, notification
26742 The @value{GDBN} remote serial protocol includes @dfn{notifications},
26743 packets that require no acknowledgment. Both the GDB and the stub
26744 may send notifications (although the only notifications defined at
26745 present are sent by the stub). Notifications carry information
26746 without incurring the round-trip latency of an acknowledgment, and so
26747 are useful for low-impact communications where occasional packet loss
26750 A notification packet has the form @samp{% @var{data} #
26751 @var{checksum}}, where @var{data} is the content of the notification,
26752 and @var{checksum} is a checksum of @var{data}, computed and formatted
26753 as for ordinary @value{GDBN} packets. A notification's @var{data}
26754 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
26755 receiving a notification, the recipient sends no @samp{+} or @samp{-}
26756 to acknowledge the notification's receipt or to report its corruption.
26758 Every notification's @var{data} begins with a name, which contains no
26759 colon characters, followed by a colon character.
26761 Recipients should silently ignore corrupted notifications and
26762 notifications they do not understand. Recipients should restart
26763 timeout periods on receipt of a well-formed notification, whether or
26764 not they understand it.
26766 Senders should only send the notifications described here when this
26767 protocol description specifies that they are permitted. In the
26768 future, we may extend the protocol to permit existing notifications in
26769 new contexts; this rule helps older senders avoid confusing newer
26772 (Older versions of @value{GDBN} ignore bytes received until they see
26773 the @samp{$} byte that begins an ordinary packet, so new stubs may
26774 transmit notifications without fear of confusing older clients. There
26775 are no notifications defined for @value{GDBN} to send at the moment, but we
26776 assume that most older stubs would ignore them, as well.)
26778 The following notification packets from the stub to @value{GDBN} are
26782 @item Stop: @var{reply}
26783 Report an asynchronous stop event in non-stop mode.
26784 The @var{reply} has the form of a stop reply, as
26785 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
26786 for information on how these notifications are acknowledged by
26790 @node Remote Non-Stop
26791 @section Remote Protocol Support for Non-Stop Mode
26793 @value{GDBN}'s remote protocol supports non-stop debugging of
26794 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
26795 supports non-stop mode, it should report that to @value{GDBN} by including
26796 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
26798 @value{GDBN} typically sends a @samp{QNonStop} packet only when
26799 establishing a new connection with the stub. Entering non-stop mode
26800 does not alter the state of any currently-running threads, but targets
26801 must stop all threads in any already-attached processes when entering
26802 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
26803 probe the target state after a mode change.
26805 In non-stop mode, when an attached process encounters an event that
26806 would otherwise be reported with a stop reply, it uses the
26807 asynchronous notification mechanism (@pxref{Notification Packets}) to
26808 inform @value{GDBN}. In contrast to all-stop mode, where all threads
26809 in all processes are stopped when a stop reply is sent, in non-stop
26810 mode only the thread reporting the stop event is stopped. That is,
26811 when reporting a @samp{S} or @samp{T} response to indicate completion
26812 of a step operation, hitting a breakpoint, or a fault, only the
26813 affected thread is stopped; any other still-running threads continue
26814 to run. When reporting a @samp{W} or @samp{X} response, all running
26815 threads belonging to other attached processes continue to run.
26817 Only one stop reply notification at a time may be pending; if
26818 additional stop events occur before @value{GDBN} has acknowledged the
26819 previous notification, they must be queued by the stub for later
26820 synchronous transmission in response to @samp{vStopped} packets from
26821 @value{GDBN}. Because the notification mechanism is unreliable,
26822 the stub is permitted to resend a stop reply notification
26823 if it believes @value{GDBN} may not have received it. @value{GDBN}
26824 ignores additional stop reply notifications received before it has
26825 finished processing a previous notification and the stub has completed
26826 sending any queued stop events.
26828 Otherwise, @value{GDBN} must be prepared to receive a stop reply
26829 notification at any time. Specifically, they may appear when
26830 @value{GDBN} is not otherwise reading input from the stub, or when
26831 @value{GDBN} is expecting to read a normal synchronous response or a
26832 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
26833 Notification packets are distinct from any other communication from
26834 the stub so there is no ambiguity.
26836 After receiving a stop reply notification, @value{GDBN} shall
26837 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
26838 as a regular, synchronous request to the stub. Such acknowledgment
26839 is not required to happen immediately, as @value{GDBN} is permitted to
26840 send other, unrelated packets to the stub first, which the stub should
26843 Upon receiving a @samp{vStopped} packet, if the stub has other queued
26844 stop events to report to @value{GDBN}, it shall respond by sending a
26845 normal stop reply response. @value{GDBN} shall then send another
26846 @samp{vStopped} packet to solicit further responses; again, it is
26847 permitted to send other, unrelated packets as well which the stub
26848 should process normally.
26850 If the stub receives a @samp{vStopped} packet and there are no
26851 additional stop events to report, the stub shall return an @samp{OK}
26852 response. At this point, if further stop events occur, the stub shall
26853 send a new stop reply notification, @value{GDBN} shall accept the
26854 notification, and the process shall be repeated.
26856 In non-stop mode, the target shall respond to the @samp{?} packet as
26857 follows. First, any incomplete stop reply notification/@samp{vStopped}
26858 sequence in progress is abandoned. The target must begin a new
26859 sequence reporting stop events for all stopped threads, whether or not
26860 it has previously reported those events to @value{GDBN}. The first
26861 stop reply is sent as a synchronous reply to the @samp{?} packet, and
26862 subsequent stop replies are sent as responses to @samp{vStopped} packets
26863 using the mechanism described above. The target must not send
26864 asynchronous stop reply notifications until the sequence is complete.
26865 If all threads are running when the target receives the @samp{?} packet,
26866 or if the target is not attached to any process, it shall respond
26869 @node Packet Acknowledgment
26870 @section Packet Acknowledgment
26872 @cindex acknowledgment, for @value{GDBN} remote
26873 @cindex packet acknowledgment, for @value{GDBN} remote
26874 By default, when either the host or the target machine receives a packet,
26875 the first response expected is an acknowledgment: either @samp{+} (to indicate
26876 the package was received correctly) or @samp{-} (to request retransmission).
26877 This mechanism allows the @value{GDBN} remote protocol to operate over
26878 unreliable transport mechanisms, such as a serial line.
26880 In cases where the transport mechanism is itself reliable (such as a pipe or
26881 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
26882 It may be desirable to disable them in that case to reduce communication
26883 overhead, or for other reasons. This can be accomplished by means of the
26884 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
26886 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
26887 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
26888 and response format still includes the normal checksum, as described in
26889 @ref{Overview}, but the checksum may be ignored by the receiver.
26891 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
26892 no-acknowledgment mode, it should report that to @value{GDBN}
26893 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
26894 @pxref{qSupported}.
26895 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
26896 disabled via the @code{set remote noack-packet off} command
26897 (@pxref{Remote Configuration}),
26898 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
26899 Only then may the stub actually turn off packet acknowledgments.
26900 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
26901 response, which can be safely ignored by the stub.
26903 Note that @code{set remote noack-packet} command only affects negotiation
26904 between @value{GDBN} and the stub when subsequent connections are made;
26905 it does not affect the protocol acknowledgment state for any current
26907 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
26908 new connection is established,
26909 there is also no protocol request to re-enable the acknowledgments
26910 for the current connection, once disabled.
26915 Example sequence of a target being re-started. Notice how the restart
26916 does not get any direct output:
26921 @emph{target restarts}
26924 <- @code{T001:1234123412341234}
26928 Example sequence of a target being stepped by a single instruction:
26931 -> @code{G1445@dots{}}
26936 <- @code{T001:1234123412341234}
26940 <- @code{1455@dots{}}
26944 @node File-I/O Remote Protocol Extension
26945 @section File-I/O Remote Protocol Extension
26946 @cindex File-I/O remote protocol extension
26949 * File-I/O Overview::
26950 * Protocol Basics::
26951 * The F Request Packet::
26952 * The F Reply Packet::
26953 * The Ctrl-C Message::
26955 * List of Supported Calls::
26956 * Protocol-specific Representation of Datatypes::
26958 * File-I/O Examples::
26961 @node File-I/O Overview
26962 @subsection File-I/O Overview
26963 @cindex file-i/o overview
26965 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
26966 target to use the host's file system and console I/O to perform various
26967 system calls. System calls on the target system are translated into a
26968 remote protocol packet to the host system, which then performs the needed
26969 actions and returns a response packet to the target system.
26970 This simulates file system operations even on targets that lack file systems.
26972 The protocol is defined to be independent of both the host and target systems.
26973 It uses its own internal representation of datatypes and values. Both
26974 @value{GDBN} and the target's @value{GDBN} stub are responsible for
26975 translating the system-dependent value representations into the internal
26976 protocol representations when data is transmitted.
26978 The communication is synchronous. A system call is possible only when
26979 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
26980 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
26981 the target is stopped to allow deterministic access to the target's
26982 memory. Therefore File-I/O is not interruptible by target signals. On
26983 the other hand, it is possible to interrupt File-I/O by a user interrupt
26984 (@samp{Ctrl-C}) within @value{GDBN}.
26986 The target's request to perform a host system call does not finish
26987 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
26988 after finishing the system call, the target returns to continuing the
26989 previous activity (continue, step). No additional continue or step
26990 request from @value{GDBN} is required.
26993 (@value{GDBP}) continue
26994 <- target requests 'system call X'
26995 target is stopped, @value{GDBN} executes system call
26996 -> @value{GDBN} returns result
26997 ... target continues, @value{GDBN} returns to wait for the target
26998 <- target hits breakpoint and sends a Txx packet
27001 The protocol only supports I/O on the console and to regular files on
27002 the host file system. Character or block special devices, pipes,
27003 named pipes, sockets or any other communication method on the host
27004 system are not supported by this protocol.
27006 File I/O is not supported in non-stop mode.
27008 @node Protocol Basics
27009 @subsection Protocol Basics
27010 @cindex protocol basics, file-i/o
27012 The File-I/O protocol uses the @code{F} packet as the request as well
27013 as reply packet. Since a File-I/O system call can only occur when
27014 @value{GDBN} is waiting for a response from the continuing or stepping target,
27015 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27016 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27017 This @code{F} packet contains all information needed to allow @value{GDBN}
27018 to call the appropriate host system call:
27022 A unique identifier for the requested system call.
27025 All parameters to the system call. Pointers are given as addresses
27026 in the target memory address space. Pointers to strings are given as
27027 pointer/length pair. Numerical values are given as they are.
27028 Numerical control flags are given in a protocol-specific representation.
27032 At this point, @value{GDBN} has to perform the following actions.
27036 If the parameters include pointer values to data needed as input to a
27037 system call, @value{GDBN} requests this data from the target with a
27038 standard @code{m} packet request. This additional communication has to be
27039 expected by the target implementation and is handled as any other @code{m}
27043 @value{GDBN} translates all value from protocol representation to host
27044 representation as needed. Datatypes are coerced into the host types.
27047 @value{GDBN} calls the system call.
27050 It then coerces datatypes back to protocol representation.
27053 If the system call is expected to return data in buffer space specified
27054 by pointer parameters to the call, the data is transmitted to the
27055 target using a @code{M} or @code{X} packet. This packet has to be expected
27056 by the target implementation and is handled as any other @code{M} or @code{X}
27061 Eventually @value{GDBN} replies with another @code{F} packet which contains all
27062 necessary information for the target to continue. This at least contains
27069 @code{errno}, if has been changed by the system call.
27076 After having done the needed type and value coercion, the target continues
27077 the latest continue or step action.
27079 @node The F Request Packet
27080 @subsection The @code{F} Request Packet
27081 @cindex file-i/o request packet
27082 @cindex @code{F} request packet
27084 The @code{F} request packet has the following format:
27087 @item F@var{call-id},@var{parameter@dots{}}
27089 @var{call-id} is the identifier to indicate the host system call to be called.
27090 This is just the name of the function.
27092 @var{parameter@dots{}} are the parameters to the system call.
27093 Parameters are hexadecimal integer values, either the actual values in case
27094 of scalar datatypes, pointers to target buffer space in case of compound
27095 datatypes and unspecified memory areas, or pointer/length pairs in case
27096 of string parameters. These are appended to the @var{call-id} as a
27097 comma-delimited list. All values are transmitted in ASCII
27098 string representation, pointer/length pairs separated by a slash.
27104 @node The F Reply Packet
27105 @subsection The @code{F} Reply Packet
27106 @cindex file-i/o reply packet
27107 @cindex @code{F} reply packet
27109 The @code{F} reply packet has the following format:
27113 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
27115 @var{retcode} is the return code of the system call as hexadecimal value.
27117 @var{errno} is the @code{errno} set by the call, in protocol-specific
27119 This parameter can be omitted if the call was successful.
27121 @var{Ctrl-C flag} is only sent if the user requested a break. In this
27122 case, @var{errno} must be sent as well, even if the call was successful.
27123 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
27130 or, if the call was interrupted before the host call has been performed:
27137 assuming 4 is the protocol-specific representation of @code{EINTR}.
27142 @node The Ctrl-C Message
27143 @subsection The @samp{Ctrl-C} Message
27144 @cindex ctrl-c message, in file-i/o protocol
27146 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
27147 reply packet (@pxref{The F Reply Packet}),
27148 the target should behave as if it had
27149 gotten a break message. The meaning for the target is ``system call
27150 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
27151 (as with a break message) and return to @value{GDBN} with a @code{T02}
27154 It's important for the target to know in which
27155 state the system call was interrupted. There are two possible cases:
27159 The system call hasn't been performed on the host yet.
27162 The system call on the host has been finished.
27166 These two states can be distinguished by the target by the value of the
27167 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
27168 call hasn't been performed. This is equivalent to the @code{EINTR} handling
27169 on POSIX systems. In any other case, the target may presume that the
27170 system call has been finished --- successfully or not --- and should behave
27171 as if the break message arrived right after the system call.
27173 @value{GDBN} must behave reliably. If the system call has not been called
27174 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
27175 @code{errno} in the packet. If the system call on the host has been finished
27176 before the user requests a break, the full action must be finished by
27177 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
27178 The @code{F} packet may only be sent when either nothing has happened
27179 or the full action has been completed.
27182 @subsection Console I/O
27183 @cindex console i/o as part of file-i/o
27185 By default and if not explicitly closed by the target system, the file
27186 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
27187 on the @value{GDBN} console is handled as any other file output operation
27188 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
27189 by @value{GDBN} so that after the target read request from file descriptor
27190 0 all following typing is buffered until either one of the following
27195 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
27197 system call is treated as finished.
27200 The user presses @key{RET}. This is treated as end of input with a trailing
27204 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
27205 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
27209 If the user has typed more characters than fit in the buffer given to
27210 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
27211 either another @code{read(0, @dots{})} is requested by the target, or debugging
27212 is stopped at the user's request.
27215 @node List of Supported Calls
27216 @subsection List of Supported Calls
27217 @cindex list of supported file-i/o calls
27234 @unnumberedsubsubsec open
27235 @cindex open, file-i/o system call
27240 int open(const char *pathname, int flags);
27241 int open(const char *pathname, int flags, mode_t mode);
27245 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
27248 @var{flags} is the bitwise @code{OR} of the following values:
27252 If the file does not exist it will be created. The host
27253 rules apply as far as file ownership and time stamps
27257 When used with @code{O_CREAT}, if the file already exists it is
27258 an error and open() fails.
27261 If the file already exists and the open mode allows
27262 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
27263 truncated to zero length.
27266 The file is opened in append mode.
27269 The file is opened for reading only.
27272 The file is opened for writing only.
27275 The file is opened for reading and writing.
27279 Other bits are silently ignored.
27283 @var{mode} is the bitwise @code{OR} of the following values:
27287 User has read permission.
27290 User has write permission.
27293 Group has read permission.
27296 Group has write permission.
27299 Others have read permission.
27302 Others have write permission.
27306 Other bits are silently ignored.
27309 @item Return value:
27310 @code{open} returns the new file descriptor or -1 if an error
27317 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
27320 @var{pathname} refers to a directory.
27323 The requested access is not allowed.
27326 @var{pathname} was too long.
27329 A directory component in @var{pathname} does not exist.
27332 @var{pathname} refers to a device, pipe, named pipe or socket.
27335 @var{pathname} refers to a file on a read-only filesystem and
27336 write access was requested.
27339 @var{pathname} is an invalid pointer value.
27342 No space on device to create the file.
27345 The process already has the maximum number of files open.
27348 The limit on the total number of files open on the system
27352 The call was interrupted by the user.
27358 @unnumberedsubsubsec close
27359 @cindex close, file-i/o system call
27368 @samp{Fclose,@var{fd}}
27370 @item Return value:
27371 @code{close} returns zero on success, or -1 if an error occurred.
27377 @var{fd} isn't a valid open file descriptor.
27380 The call was interrupted by the user.
27386 @unnumberedsubsubsec read
27387 @cindex read, file-i/o system call
27392 int read(int fd, void *buf, unsigned int count);
27396 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
27398 @item Return value:
27399 On success, the number of bytes read is returned.
27400 Zero indicates end of file. If count is zero, read
27401 returns zero as well. On error, -1 is returned.
27407 @var{fd} is not a valid file descriptor or is not open for
27411 @var{bufptr} is an invalid pointer value.
27414 The call was interrupted by the user.
27420 @unnumberedsubsubsec write
27421 @cindex write, file-i/o system call
27426 int write(int fd, const void *buf, unsigned int count);
27430 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
27432 @item Return value:
27433 On success, the number of bytes written are returned.
27434 Zero indicates nothing was written. On error, -1
27441 @var{fd} is not a valid file descriptor or is not open for
27445 @var{bufptr} is an invalid pointer value.
27448 An attempt was made to write a file that exceeds the
27449 host-specific maximum file size allowed.
27452 No space on device to write the data.
27455 The call was interrupted by the user.
27461 @unnumberedsubsubsec lseek
27462 @cindex lseek, file-i/o system call
27467 long lseek (int fd, long offset, int flag);
27471 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
27473 @var{flag} is one of:
27477 The offset is set to @var{offset} bytes.
27480 The offset is set to its current location plus @var{offset}
27484 The offset is set to the size of the file plus @var{offset}
27488 @item Return value:
27489 On success, the resulting unsigned offset in bytes from
27490 the beginning of the file is returned. Otherwise, a
27491 value of -1 is returned.
27497 @var{fd} is not a valid open file descriptor.
27500 @var{fd} is associated with the @value{GDBN} console.
27503 @var{flag} is not a proper value.
27506 The call was interrupted by the user.
27512 @unnumberedsubsubsec rename
27513 @cindex rename, file-i/o system call
27518 int rename(const char *oldpath, const char *newpath);
27522 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
27524 @item Return value:
27525 On success, zero is returned. On error, -1 is returned.
27531 @var{newpath} is an existing directory, but @var{oldpath} is not a
27535 @var{newpath} is a non-empty directory.
27538 @var{oldpath} or @var{newpath} is a directory that is in use by some
27542 An attempt was made to make a directory a subdirectory
27546 A component used as a directory in @var{oldpath} or new
27547 path is not a directory. Or @var{oldpath} is a directory
27548 and @var{newpath} exists but is not a directory.
27551 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
27554 No access to the file or the path of the file.
27558 @var{oldpath} or @var{newpath} was too long.
27561 A directory component in @var{oldpath} or @var{newpath} does not exist.
27564 The file is on a read-only filesystem.
27567 The device containing the file has no room for the new
27571 The call was interrupted by the user.
27577 @unnumberedsubsubsec unlink
27578 @cindex unlink, file-i/o system call
27583 int unlink(const char *pathname);
27587 @samp{Funlink,@var{pathnameptr}/@var{len}}
27589 @item Return value:
27590 On success, zero is returned. On error, -1 is returned.
27596 No access to the file or the path of the file.
27599 The system does not allow unlinking of directories.
27602 The file @var{pathname} cannot be unlinked because it's
27603 being used by another process.
27606 @var{pathnameptr} is an invalid pointer value.
27609 @var{pathname} was too long.
27612 A directory component in @var{pathname} does not exist.
27615 A component of the path is not a directory.
27618 The file is on a read-only filesystem.
27621 The call was interrupted by the user.
27627 @unnumberedsubsubsec stat/fstat
27628 @cindex fstat, file-i/o system call
27629 @cindex stat, file-i/o system call
27634 int stat(const char *pathname, struct stat *buf);
27635 int fstat(int fd, struct stat *buf);
27639 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
27640 @samp{Ffstat,@var{fd},@var{bufptr}}
27642 @item Return value:
27643 On success, zero is returned. On error, -1 is returned.
27649 @var{fd} is not a valid open file.
27652 A directory component in @var{pathname} does not exist or the
27653 path is an empty string.
27656 A component of the path is not a directory.
27659 @var{pathnameptr} is an invalid pointer value.
27662 No access to the file or the path of the file.
27665 @var{pathname} was too long.
27668 The call was interrupted by the user.
27674 @unnumberedsubsubsec gettimeofday
27675 @cindex gettimeofday, file-i/o system call
27680 int gettimeofday(struct timeval *tv, void *tz);
27684 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
27686 @item Return value:
27687 On success, 0 is returned, -1 otherwise.
27693 @var{tz} is a non-NULL pointer.
27696 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
27702 @unnumberedsubsubsec isatty
27703 @cindex isatty, file-i/o system call
27708 int isatty(int fd);
27712 @samp{Fisatty,@var{fd}}
27714 @item Return value:
27715 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
27721 The call was interrupted by the user.
27726 Note that the @code{isatty} call is treated as a special case: it returns
27727 1 to the target if the file descriptor is attached
27728 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
27729 would require implementing @code{ioctl} and would be more complex than
27734 @unnumberedsubsubsec system
27735 @cindex system, file-i/o system call
27740 int system(const char *command);
27744 @samp{Fsystem,@var{commandptr}/@var{len}}
27746 @item Return value:
27747 If @var{len} is zero, the return value indicates whether a shell is
27748 available. A zero return value indicates a shell is not available.
27749 For non-zero @var{len}, the value returned is -1 on error and the
27750 return status of the command otherwise. Only the exit status of the
27751 command is returned, which is extracted from the host's @code{system}
27752 return value by calling @code{WEXITSTATUS(retval)}. In case
27753 @file{/bin/sh} could not be executed, 127 is returned.
27759 The call was interrupted by the user.
27764 @value{GDBN} takes over the full task of calling the necessary host calls
27765 to perform the @code{system} call. The return value of @code{system} on
27766 the host is simplified before it's returned
27767 to the target. Any termination signal information from the child process
27768 is discarded, and the return value consists
27769 entirely of the exit status of the called command.
27771 Due to security concerns, the @code{system} call is by default refused
27772 by @value{GDBN}. The user has to allow this call explicitly with the
27773 @code{set remote system-call-allowed 1} command.
27776 @item set remote system-call-allowed
27777 @kindex set remote system-call-allowed
27778 Control whether to allow the @code{system} calls in the File I/O
27779 protocol for the remote target. The default is zero (disabled).
27781 @item show remote system-call-allowed
27782 @kindex show remote system-call-allowed
27783 Show whether the @code{system} calls are allowed in the File I/O
27787 @node Protocol-specific Representation of Datatypes
27788 @subsection Protocol-specific Representation of Datatypes
27789 @cindex protocol-specific representation of datatypes, in file-i/o protocol
27792 * Integral Datatypes::
27794 * Memory Transfer::
27799 @node Integral Datatypes
27800 @unnumberedsubsubsec Integral Datatypes
27801 @cindex integral datatypes, in file-i/o protocol
27803 The integral datatypes used in the system calls are @code{int},
27804 @code{unsigned int}, @code{long}, @code{unsigned long},
27805 @code{mode_t}, and @code{time_t}.
27807 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
27808 implemented as 32 bit values in this protocol.
27810 @code{long} and @code{unsigned long} are implemented as 64 bit types.
27812 @xref{Limits}, for corresponding MIN and MAX values (similar to those
27813 in @file{limits.h}) to allow range checking on host and target.
27815 @code{time_t} datatypes are defined as seconds since the Epoch.
27817 All integral datatypes transferred as part of a memory read or write of a
27818 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
27821 @node Pointer Values
27822 @unnumberedsubsubsec Pointer Values
27823 @cindex pointer values, in file-i/o protocol
27825 Pointers to target data are transmitted as they are. An exception
27826 is made for pointers to buffers for which the length isn't
27827 transmitted as part of the function call, namely strings. Strings
27828 are transmitted as a pointer/length pair, both as hex values, e.g.@:
27835 which is a pointer to data of length 18 bytes at position 0x1aaf.
27836 The length is defined as the full string length in bytes, including
27837 the trailing null byte. For example, the string @code{"hello world"}
27838 at address 0x123456 is transmitted as
27844 @node Memory Transfer
27845 @unnumberedsubsubsec Memory Transfer
27846 @cindex memory transfer, in file-i/o protocol
27848 Structured data which is transferred using a memory read or write (for
27849 example, a @code{struct stat}) is expected to be in a protocol-specific format
27850 with all scalar multibyte datatypes being big endian. Translation to
27851 this representation needs to be done both by the target before the @code{F}
27852 packet is sent, and by @value{GDBN} before
27853 it transfers memory to the target. Transferred pointers to structured
27854 data should point to the already-coerced data at any time.
27858 @unnumberedsubsubsec struct stat
27859 @cindex struct stat, in file-i/o protocol
27861 The buffer of type @code{struct stat} used by the target and @value{GDBN}
27862 is defined as follows:
27866 unsigned int st_dev; /* device */
27867 unsigned int st_ino; /* inode */
27868 mode_t st_mode; /* protection */
27869 unsigned int st_nlink; /* number of hard links */
27870 unsigned int st_uid; /* user ID of owner */
27871 unsigned int st_gid; /* group ID of owner */
27872 unsigned int st_rdev; /* device type (if inode device) */
27873 unsigned long st_size; /* total size, in bytes */
27874 unsigned long st_blksize; /* blocksize for filesystem I/O */
27875 unsigned long st_blocks; /* number of blocks allocated */
27876 time_t st_atime; /* time of last access */
27877 time_t st_mtime; /* time of last modification */
27878 time_t st_ctime; /* time of last change */
27882 The integral datatypes conform to the definitions given in the
27883 appropriate section (see @ref{Integral Datatypes}, for details) so this
27884 structure is of size 64 bytes.
27886 The values of several fields have a restricted meaning and/or
27892 A value of 0 represents a file, 1 the console.
27895 No valid meaning for the target. Transmitted unchanged.
27898 Valid mode bits are described in @ref{Constants}. Any other
27899 bits have currently no meaning for the target.
27904 No valid meaning for the target. Transmitted unchanged.
27909 These values have a host and file system dependent
27910 accuracy. Especially on Windows hosts, the file system may not
27911 support exact timing values.
27914 The target gets a @code{struct stat} of the above representation and is
27915 responsible for coercing it to the target representation before
27918 Note that due to size differences between the host, target, and protocol
27919 representations of @code{struct stat} members, these members could eventually
27920 get truncated on the target.
27922 @node struct timeval
27923 @unnumberedsubsubsec struct timeval
27924 @cindex struct timeval, in file-i/o protocol
27926 The buffer of type @code{struct timeval} used by the File-I/O protocol
27927 is defined as follows:
27931 time_t tv_sec; /* second */
27932 long tv_usec; /* microsecond */
27936 The integral datatypes conform to the definitions given in the
27937 appropriate section (see @ref{Integral Datatypes}, for details) so this
27938 structure is of size 8 bytes.
27941 @subsection Constants
27942 @cindex constants, in file-i/o protocol
27944 The following values are used for the constants inside of the
27945 protocol. @value{GDBN} and target are responsible for translating these
27946 values before and after the call as needed.
27957 @unnumberedsubsubsec Open Flags
27958 @cindex open flags, in file-i/o protocol
27960 All values are given in hexadecimal representation.
27972 @node mode_t Values
27973 @unnumberedsubsubsec mode_t Values
27974 @cindex mode_t values, in file-i/o protocol
27976 All values are given in octal representation.
27993 @unnumberedsubsubsec Errno Values
27994 @cindex errno values, in file-i/o protocol
27996 All values are given in decimal representation.
28021 @code{EUNKNOWN} is used as a fallback error value if a host system returns
28022 any error value not in the list of supported error numbers.
28025 @unnumberedsubsubsec Lseek Flags
28026 @cindex lseek flags, in file-i/o protocol
28035 @unnumberedsubsubsec Limits
28036 @cindex limits, in file-i/o protocol
28038 All values are given in decimal representation.
28041 INT_MIN -2147483648
28043 UINT_MAX 4294967295
28044 LONG_MIN -9223372036854775808
28045 LONG_MAX 9223372036854775807
28046 ULONG_MAX 18446744073709551615
28049 @node File-I/O Examples
28050 @subsection File-I/O Examples
28051 @cindex file-i/o examples
28053 Example sequence of a write call, file descriptor 3, buffer is at target
28054 address 0x1234, 6 bytes should be written:
28057 <- @code{Fwrite,3,1234,6}
28058 @emph{request memory read from target}
28061 @emph{return "6 bytes written"}
28065 Example sequence of a read call, file descriptor 3, buffer is at target
28066 address 0x1234, 6 bytes should be read:
28069 <- @code{Fread,3,1234,6}
28070 @emph{request memory write to target}
28071 -> @code{X1234,6:XXXXXX}
28072 @emph{return "6 bytes read"}
28076 Example sequence of a read call, call fails on the host due to invalid
28077 file descriptor (@code{EBADF}):
28080 <- @code{Fread,3,1234,6}
28084 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
28088 <- @code{Fread,3,1234,6}
28093 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
28097 <- @code{Fread,3,1234,6}
28098 -> @code{X1234,6:XXXXXX}
28102 @node Library List Format
28103 @section Library List Format
28104 @cindex library list format, remote protocol
28106 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
28107 same process as your application to manage libraries. In this case,
28108 @value{GDBN} can use the loader's symbol table and normal memory
28109 operations to maintain a list of shared libraries. On other
28110 platforms, the operating system manages loaded libraries.
28111 @value{GDBN} can not retrieve the list of currently loaded libraries
28112 through memory operations, so it uses the @samp{qXfer:libraries:read}
28113 packet (@pxref{qXfer library list read}) instead. The remote stub
28114 queries the target's operating system and reports which libraries
28117 The @samp{qXfer:libraries:read} packet returns an XML document which
28118 lists loaded libraries and their offsets. Each library has an
28119 associated name and one or more segment or section base addresses,
28120 which report where the library was loaded in memory.
28122 For the common case of libraries that are fully linked binaries, the
28123 library should have a list of segments. If the target supports
28124 dynamic linking of a relocatable object file, its library XML element
28125 should instead include a list of allocated sections. The segment or
28126 section bases are start addresses, not relocation offsets; they do not
28127 depend on the library's link-time base addresses.
28129 @value{GDBN} must be linked with the Expat library to support XML
28130 library lists. @xref{Expat}.
28132 A simple memory map, with one loaded library relocated by a single
28133 offset, looks like this:
28137 <library name="/lib/libc.so.6">
28138 <segment address="0x10000000"/>
28143 Another simple memory map, with one loaded library with three
28144 allocated sections (.text, .data, .bss), looks like this:
28148 <library name="sharedlib.o">
28149 <section address="0x10000000"/>
28150 <section address="0x20000000"/>
28151 <section address="0x30000000"/>
28156 The format of a library list is described by this DTD:
28159 <!-- library-list: Root element with versioning -->
28160 <!ELEMENT library-list (library)*>
28161 <!ATTLIST library-list version CDATA #FIXED "1.0">
28162 <!ELEMENT library (segment*, section*)>
28163 <!ATTLIST library name CDATA #REQUIRED>
28164 <!ELEMENT segment EMPTY>
28165 <!ATTLIST segment address CDATA #REQUIRED>
28166 <!ELEMENT section EMPTY>
28167 <!ATTLIST section address CDATA #REQUIRED>
28170 In addition, segments and section descriptors cannot be mixed within a
28171 single library element, and you must supply at least one segment or
28172 section for each library.
28174 @node Memory Map Format
28175 @section Memory Map Format
28176 @cindex memory map format
28178 To be able to write into flash memory, @value{GDBN} needs to obtain a
28179 memory map from the target. This section describes the format of the
28182 The memory map is obtained using the @samp{qXfer:memory-map:read}
28183 (@pxref{qXfer memory map read}) packet and is an XML document that
28184 lists memory regions.
28186 @value{GDBN} must be linked with the Expat library to support XML
28187 memory maps. @xref{Expat}.
28189 The top-level structure of the document is shown below:
28192 <?xml version="1.0"?>
28193 <!DOCTYPE memory-map
28194 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
28195 "http://sourceware.org/gdb/gdb-memory-map.dtd">
28201 Each region can be either:
28206 A region of RAM starting at @var{addr} and extending for @var{length}
28210 <memory type="ram" start="@var{addr}" length="@var{length}"/>
28215 A region of read-only memory:
28218 <memory type="rom" start="@var{addr}" length="@var{length}"/>
28223 A region of flash memory, with erasure blocks @var{blocksize}
28227 <memory type="flash" start="@var{addr}" length="@var{length}">
28228 <property name="blocksize">@var{blocksize}</property>
28234 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
28235 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
28236 packets to write to addresses in such ranges.
28238 The formal DTD for memory map format is given below:
28241 <!-- ................................................... -->
28242 <!-- Memory Map XML DTD ................................ -->
28243 <!-- File: memory-map.dtd .............................. -->
28244 <!-- .................................... .............. -->
28245 <!-- memory-map.dtd -->
28246 <!-- memory-map: Root element with versioning -->
28247 <!ELEMENT memory-map (memory | property)>
28248 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
28249 <!ELEMENT memory (property)>
28250 <!-- memory: Specifies a memory region,
28251 and its type, or device. -->
28252 <!ATTLIST memory type CDATA #REQUIRED
28253 start CDATA #REQUIRED
28254 length CDATA #REQUIRED
28255 device CDATA #IMPLIED>
28256 <!-- property: Generic attribute tag -->
28257 <!ELEMENT property (#PCDATA | property)*>
28258 <!ATTLIST property name CDATA #REQUIRED>
28261 @include agentexpr.texi
28263 @node Target Descriptions
28264 @appendix Target Descriptions
28265 @cindex target descriptions
28267 @strong{Warning:} target descriptions are still under active development,
28268 and the contents and format may change between @value{GDBN} releases.
28269 The format is expected to stabilize in the future.
28271 One of the challenges of using @value{GDBN} to debug embedded systems
28272 is that there are so many minor variants of each processor
28273 architecture in use. It is common practice for vendors to start with
28274 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
28275 and then make changes to adapt it to a particular market niche. Some
28276 architectures have hundreds of variants, available from dozens of
28277 vendors. This leads to a number of problems:
28281 With so many different customized processors, it is difficult for
28282 the @value{GDBN} maintainers to keep up with the changes.
28284 Since individual variants may have short lifetimes or limited
28285 audiences, it may not be worthwhile to carry information about every
28286 variant in the @value{GDBN} source tree.
28288 When @value{GDBN} does support the architecture of the embedded system
28289 at hand, the task of finding the correct architecture name to give the
28290 @command{set architecture} command can be error-prone.
28293 To address these problems, the @value{GDBN} remote protocol allows a
28294 target system to not only identify itself to @value{GDBN}, but to
28295 actually describe its own features. This lets @value{GDBN} support
28296 processor variants it has never seen before --- to the extent that the
28297 descriptions are accurate, and that @value{GDBN} understands them.
28299 @value{GDBN} must be linked with the Expat library to support XML
28300 target descriptions. @xref{Expat}.
28303 * Retrieving Descriptions:: How descriptions are fetched from a target.
28304 * Target Description Format:: The contents of a target description.
28305 * Predefined Target Types:: Standard types available for target
28307 * Standard Target Features:: Features @value{GDBN} knows about.
28310 @node Retrieving Descriptions
28311 @section Retrieving Descriptions
28313 Target descriptions can be read from the target automatically, or
28314 specified by the user manually. The default behavior is to read the
28315 description from the target. @value{GDBN} retrieves it via the remote
28316 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
28317 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
28318 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
28319 XML document, of the form described in @ref{Target Description
28322 Alternatively, you can specify a file to read for the target description.
28323 If a file is set, the target will not be queried. The commands to
28324 specify a file are:
28327 @cindex set tdesc filename
28328 @item set tdesc filename @var{path}
28329 Read the target description from @var{path}.
28331 @cindex unset tdesc filename
28332 @item unset tdesc filename
28333 Do not read the XML target description from a file. @value{GDBN}
28334 will use the description supplied by the current target.
28336 @cindex show tdesc filename
28337 @item show tdesc filename
28338 Show the filename to read for a target description, if any.
28342 @node Target Description Format
28343 @section Target Description Format
28344 @cindex target descriptions, XML format
28346 A target description annex is an @uref{http://www.w3.org/XML/, XML}
28347 document which complies with the Document Type Definition provided in
28348 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
28349 means you can use generally available tools like @command{xmllint} to
28350 check that your feature descriptions are well-formed and valid.
28351 However, to help people unfamiliar with XML write descriptions for
28352 their targets, we also describe the grammar here.
28354 Target descriptions can identify the architecture of the remote target
28355 and (for some architectures) provide information about custom register
28356 sets. @value{GDBN} can use this information to autoconfigure for your
28357 target, or to warn you if you connect to an unsupported target.
28359 Here is a simple target description:
28362 <target version="1.0">
28363 <architecture>i386:x86-64</architecture>
28368 This minimal description only says that the target uses
28369 the x86-64 architecture.
28371 A target description has the following overall form, with [ ] marking
28372 optional elements and @dots{} marking repeatable elements. The elements
28373 are explained further below.
28376 <?xml version="1.0"?>
28377 <!DOCTYPE target SYSTEM "gdb-target.dtd">
28378 <target version="1.0">
28379 @r{[}@var{architecture}@r{]}
28380 @r{[}@var{feature}@dots{}@r{]}
28385 The description is generally insensitive to whitespace and line
28386 breaks, under the usual common-sense rules. The XML version
28387 declaration and document type declaration can generally be omitted
28388 (@value{GDBN} does not require them), but specifying them may be
28389 useful for XML validation tools. The @samp{version} attribute for
28390 @samp{<target>} may also be omitted, but we recommend
28391 including it; if future versions of @value{GDBN} use an incompatible
28392 revision of @file{gdb-target.dtd}, they will detect and report
28393 the version mismatch.
28395 @subsection Inclusion
28396 @cindex target descriptions, inclusion
28399 @cindex <xi:include>
28402 It can sometimes be valuable to split a target description up into
28403 several different annexes, either for organizational purposes, or to
28404 share files between different possible target descriptions. You can
28405 divide a description into multiple files by replacing any element of
28406 the target description with an inclusion directive of the form:
28409 <xi:include href="@var{document}"/>
28413 When @value{GDBN} encounters an element of this form, it will retrieve
28414 the named XML @var{document}, and replace the inclusion directive with
28415 the contents of that document. If the current description was read
28416 using @samp{qXfer}, then so will be the included document;
28417 @var{document} will be interpreted as the name of an annex. If the
28418 current description was read from a file, @value{GDBN} will look for
28419 @var{document} as a file in the same directory where it found the
28420 original description.
28422 @subsection Architecture
28423 @cindex <architecture>
28425 An @samp{<architecture>} element has this form:
28428 <architecture>@var{arch}</architecture>
28431 @var{arch} is an architecture name from the same selection
28432 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
28433 Debugging Target}).
28435 @subsection Features
28438 Each @samp{<feature>} describes some logical portion of the target
28439 system. Features are currently used to describe available CPU
28440 registers and the types of their contents. A @samp{<feature>} element
28444 <feature name="@var{name}">
28445 @r{[}@var{type}@dots{}@r{]}
28451 Each feature's name should be unique within the description. The name
28452 of a feature does not matter unless @value{GDBN} has some special
28453 knowledge of the contents of that feature; if it does, the feature
28454 should have its standard name. @xref{Standard Target Features}.
28458 Any register's value is a collection of bits which @value{GDBN} must
28459 interpret. The default interpretation is a two's complement integer,
28460 but other types can be requested by name in the register description.
28461 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
28462 Target Types}), and the description can define additional composite types.
28464 Each type element must have an @samp{id} attribute, which gives
28465 a unique (within the containing @samp{<feature>}) name to the type.
28466 Types must be defined before they are used.
28469 Some targets offer vector registers, which can be treated as arrays
28470 of scalar elements. These types are written as @samp{<vector>} elements,
28471 specifying the array element type, @var{type}, and the number of elements,
28475 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
28479 If a register's value is usefully viewed in multiple ways, define it
28480 with a union type containing the useful representations. The
28481 @samp{<union>} element contains one or more @samp{<field>} elements,
28482 each of which has a @var{name} and a @var{type}:
28485 <union id="@var{id}">
28486 <field name="@var{name}" type="@var{type}"/>
28491 @subsection Registers
28494 Each register is represented as an element with this form:
28497 <reg name="@var{name}"
28498 bitsize="@var{size}"
28499 @r{[}regnum="@var{num}"@r{]}
28500 @r{[}save-restore="@var{save-restore}"@r{]}
28501 @r{[}type="@var{type}"@r{]}
28502 @r{[}group="@var{group}"@r{]}/>
28506 The components are as follows:
28511 The register's name; it must be unique within the target description.
28514 The register's size, in bits.
28517 The register's number. If omitted, a register's number is one greater
28518 than that of the previous register (either in the current feature or in
28519 a preceeding feature); the first register in the target description
28520 defaults to zero. This register number is used to read or write
28521 the register; e.g.@: it is used in the remote @code{p} and @code{P}
28522 packets, and registers appear in the @code{g} and @code{G} packets
28523 in order of increasing register number.
28526 Whether the register should be preserved across inferior function
28527 calls; this must be either @code{yes} or @code{no}. The default is
28528 @code{yes}, which is appropriate for most registers except for
28529 some system control registers; this is not related to the target's
28533 The type of the register. @var{type} may be a predefined type, a type
28534 defined in the current feature, or one of the special types @code{int}
28535 and @code{float}. @code{int} is an integer type of the correct size
28536 for @var{bitsize}, and @code{float} is a floating point type (in the
28537 architecture's normal floating point format) of the correct size for
28538 @var{bitsize}. The default is @code{int}.
28541 The register group to which this register belongs. @var{group} must
28542 be either @code{general}, @code{float}, or @code{vector}. If no
28543 @var{group} is specified, @value{GDBN} will not display the register
28544 in @code{info registers}.
28548 @node Predefined Target Types
28549 @section Predefined Target Types
28550 @cindex target descriptions, predefined types
28552 Type definitions in the self-description can build up composite types
28553 from basic building blocks, but can not define fundamental types. Instead,
28554 standard identifiers are provided by @value{GDBN} for the fundamental
28555 types. The currently supported types are:
28564 Signed integer types holding the specified number of bits.
28571 Unsigned integer types holding the specified number of bits.
28575 Pointers to unspecified code and data. The program counter and
28576 any dedicated return address register may be marked as code
28577 pointers; printing a code pointer converts it into a symbolic
28578 address. The stack pointer and any dedicated address registers
28579 may be marked as data pointers.
28582 Single precision IEEE floating point.
28585 Double precision IEEE floating point.
28588 The 12-byte extended precision format used by ARM FPA registers.
28592 @node Standard Target Features
28593 @section Standard Target Features
28594 @cindex target descriptions, standard features
28596 A target description must contain either no registers or all the
28597 target's registers. If the description contains no registers, then
28598 @value{GDBN} will assume a default register layout, selected based on
28599 the architecture. If the description contains any registers, the
28600 default layout will not be used; the standard registers must be
28601 described in the target description, in such a way that @value{GDBN}
28602 can recognize them.
28604 This is accomplished by giving specific names to feature elements
28605 which contain standard registers. @value{GDBN} will look for features
28606 with those names and verify that they contain the expected registers;
28607 if any known feature is missing required registers, or if any required
28608 feature is missing, @value{GDBN} will reject the target
28609 description. You can add additional registers to any of the
28610 standard features --- @value{GDBN} will display them just as if
28611 they were added to an unrecognized feature.
28613 This section lists the known features and their expected contents.
28614 Sample XML documents for these features are included in the
28615 @value{GDBN} source tree, in the directory @file{gdb/features}.
28617 Names recognized by @value{GDBN} should include the name of the
28618 company or organization which selected the name, and the overall
28619 architecture to which the feature applies; so e.g.@: the feature
28620 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
28622 The names of registers are not case sensitive for the purpose
28623 of recognizing standard features, but @value{GDBN} will only display
28624 registers using the capitalization used in the description.
28630 * PowerPC Features::
28635 @subsection ARM Features
28636 @cindex target descriptions, ARM features
28638 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
28639 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
28640 @samp{lr}, @samp{pc}, and @samp{cpsr}.
28642 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
28643 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
28645 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
28646 it should contain at least registers @samp{wR0} through @samp{wR15} and
28647 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
28648 @samp{wCSSF}, and @samp{wCASF} registers are optional.
28650 @node MIPS Features
28651 @subsection MIPS Features
28652 @cindex target descriptions, MIPS features
28654 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
28655 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
28656 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
28659 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
28660 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
28661 registers. They may be 32-bit or 64-bit depending on the target.
28663 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
28664 it may be optional in a future version of @value{GDBN}. It should
28665 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
28666 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
28668 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
28669 contain a single register, @samp{restart}, which is used by the
28670 Linux kernel to control restartable syscalls.
28672 @node M68K Features
28673 @subsection M68K Features
28674 @cindex target descriptions, M68K features
28677 @item @samp{org.gnu.gdb.m68k.core}
28678 @itemx @samp{org.gnu.gdb.coldfire.core}
28679 @itemx @samp{org.gnu.gdb.fido.core}
28680 One of those features must be always present.
28681 The feature that is present determines which flavor of m86k is
28682 used. The feature that is present should contain registers
28683 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
28684 @samp{sp}, @samp{ps} and @samp{pc}.
28686 @item @samp{org.gnu.gdb.coldfire.fp}
28687 This feature is optional. If present, it should contain registers
28688 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
28692 @node PowerPC Features
28693 @subsection PowerPC Features
28694 @cindex target descriptions, PowerPC features
28696 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
28697 targets. It should contain registers @samp{r0} through @samp{r31},
28698 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
28699 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
28701 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
28702 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
28704 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
28705 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
28708 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
28709 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
28710 will combine these registers with the floating point registers
28711 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
28712 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
28713 through @samp{vs63}, the set of vector registers for POWER7.
28715 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
28716 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
28717 @samp{spefscr}. SPE targets should provide 32-bit registers in
28718 @samp{org.gnu.gdb.power.core} and provide the upper halves in
28719 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
28720 these to present registers @samp{ev0} through @samp{ev31} to the
28735 % I think something like @colophon should be in texinfo. In the
28737 \long\def\colophon{\hbox to0pt{}\vfill
28738 \centerline{The body of this manual is set in}
28739 \centerline{\fontname\tenrm,}
28740 \centerline{with headings in {\bf\fontname\tenbf}}
28741 \centerline{and examples in {\tt\fontname\tentt}.}
28742 \centerline{{\it\fontname\tenit\/},}
28743 \centerline{{\bf\fontname\tenbf}, and}
28744 \centerline{{\sl\fontname\tensl\/}}
28745 \centerline{are used for emphasis.}\vfill}
28747 % Blame: doc@cygnus.com, 1991.