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, 2009, 2010
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
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
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 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
218 Support for Modula-2 is partial. For information on Modula-2, see
219 @ref{Modula-2,,Modula-2}.
222 Debugging Pascal programs which use sets, subranges, file variables, or
223 nested functions does not currently work. @value{GDBN} does not support
224 entering expressions, printing values, or similar features using Pascal
228 @value{GDBN} can be used to debug programs written in Fortran, although
229 it may be necessary to refer to some variables with a trailing
232 @value{GDBN} can be used to debug programs written in Objective-C,
233 using either the Apple/NeXT or the GNU Objective-C runtime.
236 * Free Software:: Freely redistributable software
237 * Contributors:: Contributors to GDB
241 @unnumberedsec Free Software
243 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
244 General Public License
245 (GPL). The GPL gives you the freedom to copy or adapt a licensed
246 program---but every person getting a copy also gets with it the
247 freedom to modify that copy (which means that they must get access to
248 the source code), and the freedom to distribute further copies.
249 Typical software companies use copyrights to limit your freedoms; the
250 Free Software Foundation uses the GPL to preserve these freedoms.
252 Fundamentally, the General Public License is a license which says that
253 you have these freedoms and that you cannot take these freedoms away
256 @unnumberedsec Free Software Needs Free Documentation
258 The biggest deficiency in the free software community today is not in
259 the software---it is the lack of good free documentation that we can
260 include with the free software. Many of our most important
261 programs do not come with free reference manuals and free introductory
262 texts. Documentation is an essential part of any software package;
263 when an important free software package does not come with a free
264 manual and a free tutorial, that is a major gap. We have many such
267 Consider Perl, for instance. The tutorial manuals that people
268 normally use are non-free. How did this come about? Because the
269 authors of those manuals published them with restrictive terms---no
270 copying, no modification, source files not available---which exclude
271 them from the free software world.
273 That wasn't the first time this sort of thing happened, and it was far
274 from the last. Many times we have heard a GNU user eagerly describe a
275 manual that he is writing, his intended contribution to the community,
276 only to learn that he had ruined everything by signing a publication
277 contract to make it non-free.
279 Free documentation, like free software, is a matter of freedom, not
280 price. The problem with the non-free manual is not that publishers
281 charge a price for printed copies---that in itself is fine. (The Free
282 Software Foundation sells printed copies of manuals, too.) The
283 problem is the restrictions on the use of the manual. Free manuals
284 are available in source code form, and give you permission to copy and
285 modify. Non-free manuals do not allow this.
287 The criteria of freedom for a free manual are roughly the same as for
288 free software. Redistribution (including the normal kinds of
289 commercial redistribution) must be permitted, so that the manual can
290 accompany every copy of the program, both on-line and on paper.
292 Permission for modification of the technical content is crucial too.
293 When people modify the software, adding or changing features, if they
294 are conscientious they will change the manual too---so they can
295 provide accurate and clear documentation for the modified program. A
296 manual that leaves you no choice but to write a new manual to document
297 a changed version of the program is not really available to our
300 Some kinds of limits on the way modification is handled are
301 acceptable. For example, requirements to preserve the original
302 author's copyright notice, the distribution terms, or the list of
303 authors, are ok. It is also no problem to require modified versions
304 to include notice that they were modified. Even entire sections that
305 may not be deleted or changed are acceptable, as long as they deal
306 with nontechnical topics (like this one). These kinds of restrictions
307 are acceptable because they don't obstruct the community's normal use
310 However, it must be possible to modify all the @emph{technical}
311 content of the manual, and then distribute the result in all the usual
312 media, through all the usual channels. Otherwise, the restrictions
313 obstruct the use of the manual, it is not free, and we need another
314 manual to replace it.
316 Please spread the word about this issue. Our community continues to
317 lose manuals to proprietary publishing. If we spread the word that
318 free software needs free reference manuals and free tutorials, perhaps
319 the next person who wants to contribute by writing documentation will
320 realize, before it is too late, that only free manuals contribute to
321 the free software community.
323 If you are writing documentation, please insist on publishing it under
324 the GNU Free Documentation License or another free documentation
325 license. Remember that this decision requires your approval---you
326 don't have to let the publisher decide. Some commercial publishers
327 will use a free license if you insist, but they will not propose the
328 option; it is up to you to raise the issue and say firmly that this is
329 what you want. If the publisher you are dealing with refuses, please
330 try other publishers. If you're not sure whether a proposed license
331 is free, write to @email{licensing@@gnu.org}.
333 You can encourage commercial publishers to sell more free, copylefted
334 manuals and tutorials by buying them, and particularly by buying
335 copies from the publishers that paid for their writing or for major
336 improvements. Meanwhile, try to avoid buying non-free documentation
337 at all. Check the distribution terms of a manual before you buy it,
338 and insist that whoever seeks your business must respect your freedom.
339 Check the history of the book, and try to reward the publishers that
340 have paid or pay the authors to work on it.
342 The Free Software Foundation maintains a list of free documentation
343 published by other publishers, at
344 @url{http://www.fsf.org/doc/other-free-books.html}.
347 @unnumberedsec Contributors to @value{GDBN}
349 Richard Stallman was the original author of @value{GDBN}, and of many
350 other @sc{gnu} programs. Many others have contributed to its
351 development. This section attempts to credit major contributors. One
352 of the virtues of free software is that everyone is free to contribute
353 to it; with regret, we cannot actually acknowledge everyone here. The
354 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
355 blow-by-blow account.
357 Changes much prior to version 2.0 are lost in the mists of time.
360 @emph{Plea:} Additions to this section are particularly welcome. If you
361 or your friends (or enemies, to be evenhanded) have been unfairly
362 omitted from this list, we would like to add your names!
365 So that they may not regard their many labors as thankless, we
366 particularly thank those who shepherded @value{GDBN} through major
368 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
369 Jim Blandy (release 4.18);
370 Jason Molenda (release 4.17);
371 Stan Shebs (release 4.14);
372 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
373 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
374 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
375 Jim Kingdon (releases 3.5, 3.4, and 3.3);
376 and Randy Smith (releases 3.2, 3.1, and 3.0).
378 Richard Stallman, assisted at various times by Peter TerMaat, Chris
379 Hanson, and Richard Mlynarik, handled releases through 2.8.
381 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
382 in @value{GDBN}, with significant additional contributions from Per
383 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
384 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
385 much general update work leading to release 3.0).
387 @value{GDBN} uses the BFD subroutine library to examine multiple
388 object-file formats; BFD was a joint project of David V.
389 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
391 David Johnson wrote the original COFF support; Pace Willison did
392 the original support for encapsulated COFF.
394 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
396 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
397 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
399 Jean-Daniel Fekete contributed Sun 386i support.
400 Chris Hanson improved the HP9000 support.
401 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
402 David Johnson contributed Encore Umax support.
403 Jyrki Kuoppala contributed Altos 3068 support.
404 Jeff Law contributed HP PA and SOM support.
405 Keith Packard contributed NS32K support.
406 Doug Rabson contributed Acorn Risc Machine support.
407 Bob Rusk contributed Harris Nighthawk CX-UX support.
408 Chris Smith contributed Convex support (and Fortran debugging).
409 Jonathan Stone contributed Pyramid support.
410 Michael Tiemann contributed SPARC support.
411 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
412 Pace Willison contributed Intel 386 support.
413 Jay Vosburgh contributed Symmetry support.
414 Marko Mlinar contributed OpenRISC 1000 support.
416 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
418 Rich Schaefer and Peter Schauer helped with support of SunOS shared
421 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
422 about several machine instruction sets.
424 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
425 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
426 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
427 and RDI targets, respectively.
429 Brian Fox is the author of the readline libraries providing
430 command-line editing and command history.
432 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
433 Modula-2 support, and contributed the Languages chapter of this manual.
435 Fred Fish wrote most of the support for Unix System Vr4.
436 He also enhanced the command-completion support to cover C@t{++} overloaded
439 Hitachi America (now Renesas America), Ltd. sponsored the support for
440 H8/300, H8/500, and Super-H processors.
442 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
444 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
447 Toshiba sponsored the support for the TX39 Mips processor.
449 Matsushita sponsored the support for the MN10200 and MN10300 processors.
451 Fujitsu sponsored the support for SPARClite and FR30 processors.
453 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
456 Michael Snyder added support for tracepoints.
458 Stu Grossman wrote gdbserver.
460 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
461 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
463 The following people at the Hewlett-Packard Company contributed
464 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
465 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
466 compiler, and the Text User Interface (nee Terminal User Interface):
467 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
468 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
469 provided HP-specific information in this manual.
471 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
472 Robert Hoehne made significant contributions to the DJGPP port.
474 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
475 development since 1991. Cygnus engineers who have worked on @value{GDBN}
476 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
477 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
478 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
479 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
480 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
481 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
482 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
483 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
484 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
485 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
486 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
487 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
488 Zuhn have made contributions both large and small.
490 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
491 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
493 Jim Blandy added support for preprocessor macros, while working for Red
496 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
497 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
498 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
499 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
500 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
501 with the migration of old architectures to this new framework.
503 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
504 unwinder framework, this consisting of a fresh new design featuring
505 frame IDs, independent frame sniffers, and the sentinel frame. Mark
506 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
507 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
508 trad unwinders. The architecture-specific changes, each involving a
509 complete rewrite of the architecture's frame code, were carried out by
510 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
511 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
512 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
513 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
516 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
517 Tensilica, Inc.@: contributed support for Xtensa processors. Others
518 who have worked on the Xtensa port of @value{GDBN} in the past include
519 Steve Tjiang, John Newlin, and Scott Foehner.
521 Michael Eager and staff of Xilinx, Inc., contributed support for the
522 Xilinx MicroBlaze architecture.
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 commands from file @var{file}. The contents of this file is
967 evaluated exactly as the @code{source} command would.
968 @xref{Command Files,, Command files}.
970 @item -eval-command @var{command}
971 @itemx -ex @var{command}
972 @cindex @code{--eval-command}
974 Execute a single @value{GDBN} command.
976 This option may be used multiple times to call multiple commands. It may
977 also be interleaved with @samp{-command} as required.
980 @value{GDBP} -ex 'target sim' -ex 'load' \
981 -x setbreakpoints -ex 'run' a.out
984 @item -directory @var{directory}
985 @itemx -d @var{directory}
986 @cindex @code{--directory}
988 Add @var{directory} to the path to search for source and script files.
992 @cindex @code{--readnow}
994 Read each symbol file's entire symbol table immediately, rather than
995 the default, which is to read it incrementally as it is needed.
996 This makes startup slower, but makes future operations faster.
1001 @subsection Choosing Modes
1003 You can run @value{GDBN} in various alternative modes---for example, in
1004 batch mode or quiet mode.
1011 Do not execute commands found in any initialization files. Normally,
1012 @value{GDBN} executes the commands in these files after all the command
1013 options and arguments have been processed. @xref{Command Files,,Command
1019 @cindex @code{--quiet}
1020 @cindex @code{--silent}
1022 ``Quiet''. Do not print the introductory and copyright messages. These
1023 messages are also suppressed in batch mode.
1026 @cindex @code{--batch}
1027 Run in batch mode. Exit with status @code{0} after processing all the
1028 command files specified with @samp{-x} (and all commands from
1029 initialization files, if not inhibited with @samp{-n}). Exit with
1030 nonzero status if an error occurs in executing the @value{GDBN} commands
1031 in the command files. Batch mode also disables pagination;
1032 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1033 effect (@pxref{Messages/Warnings}).
1035 Batch mode may be useful for running @value{GDBN} as a filter, for
1036 example to download and run a program on another computer; in order to
1037 make this more useful, the message
1040 Program exited normally.
1044 (which is ordinarily issued whenever a program running under
1045 @value{GDBN} control terminates) is not issued when running in batch
1049 @cindex @code{--batch-silent}
1050 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1051 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1052 unaffected). This is much quieter than @samp{-silent} and would be useless
1053 for an interactive session.
1055 This is particularly useful when using targets that give @samp{Loading section}
1056 messages, for example.
1058 Note that targets that give their output via @value{GDBN}, as opposed to
1059 writing directly to @code{stdout}, will also be made silent.
1061 @item -return-child-result
1062 @cindex @code{--return-child-result}
1063 The return code from @value{GDBN} will be the return code from the child
1064 process (the process being debugged), with the following exceptions:
1068 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1069 internal error. In this case the exit code is the same as it would have been
1070 without @samp{-return-child-result}.
1072 The user quits with an explicit value. E.g., @samp{quit 1}.
1074 The child process never runs, or is not allowed to terminate, in which case
1075 the exit code will be -1.
1078 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1079 when @value{GDBN} is being used as a remote program loader or simulator
1084 @cindex @code{--nowindows}
1086 ``No windows''. If @value{GDBN} comes with a graphical user interface
1087 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1088 interface. If no GUI is available, this option has no effect.
1092 @cindex @code{--windows}
1094 If @value{GDBN} includes a GUI, then this option requires it to be
1097 @item -cd @var{directory}
1099 Run @value{GDBN} using @var{directory} as its working directory,
1100 instead of the current directory.
1104 @cindex @code{--fullname}
1106 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1107 subprocess. It tells @value{GDBN} to output the full file name and line
1108 number in a standard, recognizable fashion each time a stack frame is
1109 displayed (which includes each time your program stops). This
1110 recognizable format looks like two @samp{\032} characters, followed by
1111 the file name, line number and character position separated by colons,
1112 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1113 @samp{\032} characters as a signal to display the source code for the
1117 @cindex @code{--epoch}
1118 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1119 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1120 routines so as to allow Epoch to display values of expressions in a
1123 @item -annotate @var{level}
1124 @cindex @code{--annotate}
1125 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1126 effect is identical to using @samp{set annotate @var{level}}
1127 (@pxref{Annotations}). The annotation @var{level} controls how much
1128 information @value{GDBN} prints together with its prompt, values of
1129 expressions, source lines, and other types of output. Level 0 is the
1130 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1131 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1132 that control @value{GDBN}, and level 2 has been deprecated.
1134 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1138 @cindex @code{--args}
1139 Change interpretation of command line so that arguments following the
1140 executable file are passed as command line arguments to the inferior.
1141 This option stops option processing.
1143 @item -baud @var{bps}
1145 @cindex @code{--baud}
1147 Set the line speed (baud rate or bits per second) of any serial
1148 interface used by @value{GDBN} for remote debugging.
1150 @item -l @var{timeout}
1152 Set the timeout (in seconds) of any communication used by @value{GDBN}
1153 for remote debugging.
1155 @item -tty @var{device}
1156 @itemx -t @var{device}
1157 @cindex @code{--tty}
1159 Run using @var{device} for your program's standard input and output.
1160 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1162 @c resolve the situation of these eventually
1164 @cindex @code{--tui}
1165 Activate the @dfn{Text User Interface} when starting. The Text User
1166 Interface manages several text windows on the terminal, showing
1167 source, assembly, registers and @value{GDBN} command outputs
1168 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1169 Text User Interface can be enabled by invoking the program
1170 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1171 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1174 @c @cindex @code{--xdb}
1175 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1176 @c For information, see the file @file{xdb_trans.html}, which is usually
1177 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1180 @item -interpreter @var{interp}
1181 @cindex @code{--interpreter}
1182 Use the interpreter @var{interp} for interface with the controlling
1183 program or device. This option is meant to be set by programs which
1184 communicate with @value{GDBN} using it as a back end.
1185 @xref{Interpreters, , Command Interpreters}.
1187 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1188 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1189 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1190 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1191 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1192 @sc{gdb/mi} interfaces are no longer supported.
1195 @cindex @code{--write}
1196 Open the executable and core files for both reading and writing. This
1197 is equivalent to the @samp{set write on} command inside @value{GDBN}
1201 @cindex @code{--statistics}
1202 This option causes @value{GDBN} to print statistics about time and
1203 memory usage after it completes each command and returns to the prompt.
1206 @cindex @code{--version}
1207 This option causes @value{GDBN} to print its version number and
1208 no-warranty blurb, and exit.
1213 @subsection What @value{GDBN} Does During Startup
1214 @cindex @value{GDBN} startup
1216 Here's the description of what @value{GDBN} does during session startup:
1220 Sets up the command interpreter as specified by the command line
1221 (@pxref{Mode Options, interpreter}).
1225 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1226 used when building @value{GDBN}; @pxref{System-wide configuration,
1227 ,System-wide configuration and settings}) and executes all the commands in
1231 Reads the init file (if any) in your home directory@footnote{On
1232 DOS/Windows systems, the home directory is the one pointed to by the
1233 @code{HOME} environment variable.} and executes all the commands in
1237 Processes command line options and operands.
1240 Reads and executes the commands from init file (if any) in the current
1241 working directory. This is only done if the current directory is
1242 different from your home directory. Thus, you can have more than one
1243 init file, one generic in your home directory, and another, specific
1244 to the program you are debugging, in the directory where you invoke
1248 Reads command files specified by the @samp{-x} option. @xref{Command
1249 Files}, for more details about @value{GDBN} command files.
1252 Reads the command history recorded in the @dfn{history file}.
1253 @xref{Command History}, for more details about the command history and the
1254 files where @value{GDBN} records it.
1257 Init files use the same syntax as @dfn{command files} (@pxref{Command
1258 Files}) and are processed by @value{GDBN} in the same way. The init
1259 file in your home directory can set options (such as @samp{set
1260 complaints}) that affect subsequent processing of command line options
1261 and operands. Init files are not executed if you use the @samp{-nx}
1262 option (@pxref{Mode Options, ,Choosing Modes}).
1264 To display the list of init files loaded by gdb at startup, you
1265 can use @kbd{gdb --help}.
1267 @cindex init file name
1268 @cindex @file{.gdbinit}
1269 @cindex @file{gdb.ini}
1270 The @value{GDBN} init files are normally called @file{.gdbinit}.
1271 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1272 the limitations of file names imposed by DOS filesystems. The Windows
1273 ports of @value{GDBN} use the standard name, but if they find a
1274 @file{gdb.ini} file, they warn you about that and suggest to rename
1275 the file to the standard name.
1279 @section Quitting @value{GDBN}
1280 @cindex exiting @value{GDBN}
1281 @cindex leaving @value{GDBN}
1284 @kindex quit @r{[}@var{expression}@r{]}
1285 @kindex q @r{(@code{quit})}
1286 @item quit @r{[}@var{expression}@r{]}
1288 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1289 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1290 do not supply @var{expression}, @value{GDBN} will terminate normally;
1291 otherwise it will terminate using the result of @var{expression} as the
1296 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1297 terminates the action of any @value{GDBN} command that is in progress and
1298 returns to @value{GDBN} command level. It is safe to type the interrupt
1299 character at any time because @value{GDBN} does not allow it to take effect
1300 until a time when it is safe.
1302 If you have been using @value{GDBN} to control an attached process or
1303 device, you can release it with the @code{detach} command
1304 (@pxref{Attach, ,Debugging an Already-running Process}).
1306 @node Shell Commands
1307 @section Shell Commands
1309 If you need to execute occasional shell commands during your
1310 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1311 just use the @code{shell} command.
1315 @cindex shell escape
1316 @item shell @var{command string}
1317 Invoke a standard shell to execute @var{command string}.
1318 If it exists, the environment variable @code{SHELL} determines which
1319 shell to run. Otherwise @value{GDBN} uses the default shell
1320 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1323 The utility @code{make} is often needed in development environments.
1324 You do not have to use the @code{shell} command for this purpose in
1329 @cindex calling make
1330 @item make @var{make-args}
1331 Execute the @code{make} program with the specified
1332 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1335 @node Logging Output
1336 @section Logging Output
1337 @cindex logging @value{GDBN} output
1338 @cindex save @value{GDBN} output to a file
1340 You may want to save the output of @value{GDBN} commands to a file.
1341 There are several commands to control @value{GDBN}'s logging.
1345 @item set logging on
1347 @item set logging off
1349 @cindex logging file name
1350 @item set logging file @var{file}
1351 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1352 @item set logging overwrite [on|off]
1353 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1354 you want @code{set logging on} to overwrite the logfile instead.
1355 @item set logging redirect [on|off]
1356 By default, @value{GDBN} output will go to both the terminal and the logfile.
1357 Set @code{redirect} if you want output to go only to the log file.
1358 @kindex show logging
1360 Show the current values of the logging settings.
1364 @chapter @value{GDBN} Commands
1366 You can abbreviate a @value{GDBN} command to the first few letters of the command
1367 name, if that abbreviation is unambiguous; and you can repeat certain
1368 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1369 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1370 show you the alternatives available, if there is more than one possibility).
1373 * Command Syntax:: How to give commands to @value{GDBN}
1374 * Completion:: Command completion
1375 * Help:: How to ask @value{GDBN} for help
1378 @node Command Syntax
1379 @section Command Syntax
1381 A @value{GDBN} command is a single line of input. There is no limit on
1382 how long it can be. It starts with a command name, which is followed by
1383 arguments whose meaning depends on the command name. For example, the
1384 command @code{step} accepts an argument which is the number of times to
1385 step, as in @samp{step 5}. You can also use the @code{step} command
1386 with no arguments. Some commands do not allow any arguments.
1388 @cindex abbreviation
1389 @value{GDBN} command names may always be truncated if that abbreviation is
1390 unambiguous. Other possible command abbreviations are listed in the
1391 documentation for individual commands. In some cases, even ambiguous
1392 abbreviations are allowed; for example, @code{s} is specially defined as
1393 equivalent to @code{step} even though there are other commands whose
1394 names start with @code{s}. You can test abbreviations by using them as
1395 arguments to the @code{help} command.
1397 @cindex repeating commands
1398 @kindex RET @r{(repeat last command)}
1399 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1400 repeat the previous command. Certain commands (for example, @code{run})
1401 will not repeat this way; these are commands whose unintentional
1402 repetition might cause trouble and which you are unlikely to want to
1403 repeat. User-defined commands can disable this feature; see
1404 @ref{Define, dont-repeat}.
1406 The @code{list} and @code{x} commands, when you repeat them with
1407 @key{RET}, construct new arguments rather than repeating
1408 exactly as typed. This permits easy scanning of source or memory.
1410 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1411 output, in a way similar to the common utility @code{more}
1412 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1413 @key{RET} too many in this situation, @value{GDBN} disables command
1414 repetition after any command that generates this sort of display.
1416 @kindex # @r{(a comment)}
1418 Any text from a @kbd{#} to the end of the line is a comment; it does
1419 nothing. This is useful mainly in command files (@pxref{Command
1420 Files,,Command Files}).
1422 @cindex repeating command sequences
1423 @kindex Ctrl-o @r{(operate-and-get-next)}
1424 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1425 commands. This command accepts the current line, like @key{RET}, and
1426 then fetches the next line relative to the current line from the history
1430 @section Command Completion
1433 @cindex word completion
1434 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1435 only one possibility; it can also show you what the valid possibilities
1436 are for the next word in a command, at any time. This works for @value{GDBN}
1437 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1439 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1440 of a word. If there is only one possibility, @value{GDBN} fills in the
1441 word, and waits for you to finish the command (or press @key{RET} to
1442 enter it). For example, if you type
1444 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1445 @c complete accuracy in these examples; space introduced for clarity.
1446 @c If texinfo enhancements make it unnecessary, it would be nice to
1447 @c replace " @key" by "@key" in the following...
1449 (@value{GDBP}) info bre @key{TAB}
1453 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1454 the only @code{info} subcommand beginning with @samp{bre}:
1457 (@value{GDBP}) info breakpoints
1461 You can either press @key{RET} at this point, to run the @code{info
1462 breakpoints} command, or backspace and enter something else, if
1463 @samp{breakpoints} does not look like the command you expected. (If you
1464 were sure you wanted @code{info breakpoints} in the first place, you
1465 might as well just type @key{RET} immediately after @samp{info bre},
1466 to exploit command abbreviations rather than command completion).
1468 If there is more than one possibility for the next word when you press
1469 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1470 characters and try again, or just press @key{TAB} a second time;
1471 @value{GDBN} displays all the possible completions for that word. For
1472 example, you might want to set a breakpoint on a subroutine whose name
1473 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1474 just sounds the bell. Typing @key{TAB} again displays all the
1475 function names in your program that begin with those characters, for
1479 (@value{GDBP}) b make_ @key{TAB}
1480 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1481 make_a_section_from_file make_environ
1482 make_abs_section make_function_type
1483 make_blockvector make_pointer_type
1484 make_cleanup make_reference_type
1485 make_command make_symbol_completion_list
1486 (@value{GDBP}) b make_
1490 After displaying the available possibilities, @value{GDBN} copies your
1491 partial input (@samp{b make_} in the example) so you can finish the
1494 If you just want to see the list of alternatives in the first place, you
1495 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1496 means @kbd{@key{META} ?}. You can type this either by holding down a
1497 key designated as the @key{META} shift on your keyboard (if there is
1498 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1500 @cindex quotes in commands
1501 @cindex completion of quoted strings
1502 Sometimes the string you need, while logically a ``word'', may contain
1503 parentheses or other characters that @value{GDBN} normally excludes from
1504 its notion of a word. To permit word completion to work in this
1505 situation, you may enclose words in @code{'} (single quote marks) in
1506 @value{GDBN} commands.
1508 The most likely situation where you might need this is in typing the
1509 name of a C@t{++} function. This is because C@t{++} allows function
1510 overloading (multiple definitions of the same function, distinguished
1511 by argument type). For example, when you want to set a breakpoint you
1512 may need to distinguish whether you mean the version of @code{name}
1513 that takes an @code{int} parameter, @code{name(int)}, or the version
1514 that takes a @code{float} parameter, @code{name(float)}. To use the
1515 word-completion facilities in this situation, type a single quote
1516 @code{'} at the beginning of the function name. This alerts
1517 @value{GDBN} that it may need to consider more information than usual
1518 when you press @key{TAB} or @kbd{M-?} to request word completion:
1521 (@value{GDBP}) b 'bubble( @kbd{M-?}
1522 bubble(double,double) bubble(int,int)
1523 (@value{GDBP}) b 'bubble(
1526 In some cases, @value{GDBN} can tell that completing a name requires using
1527 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1528 completing as much as it can) if you do not type the quote in the first
1532 (@value{GDBP}) b bub @key{TAB}
1533 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1534 (@value{GDBP}) b 'bubble(
1538 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1539 you have not yet started typing the argument list when you ask for
1540 completion on an overloaded symbol.
1542 For more information about overloaded functions, see @ref{C Plus Plus
1543 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1544 overload-resolution off} to disable overload resolution;
1545 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1547 @cindex completion of structure field names
1548 @cindex structure field name completion
1549 @cindex completion of union field names
1550 @cindex union field name completion
1551 When completing in an expression which looks up a field in a
1552 structure, @value{GDBN} also tries@footnote{The completer can be
1553 confused by certain kinds of invalid expressions. Also, it only
1554 examines the static type of the expression, not the dynamic type.} to
1555 limit completions to the field names available in the type of the
1559 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1560 magic to_delete to_fputs to_put to_rewind
1561 to_data to_flush to_isatty to_read to_write
1565 This is because the @code{gdb_stdout} is a variable of the type
1566 @code{struct ui_file} that is defined in @value{GDBN} sources as
1573 ui_file_flush_ftype *to_flush;
1574 ui_file_write_ftype *to_write;
1575 ui_file_fputs_ftype *to_fputs;
1576 ui_file_read_ftype *to_read;
1577 ui_file_delete_ftype *to_delete;
1578 ui_file_isatty_ftype *to_isatty;
1579 ui_file_rewind_ftype *to_rewind;
1580 ui_file_put_ftype *to_put;
1587 @section Getting Help
1588 @cindex online documentation
1591 You can always ask @value{GDBN} itself for information on its commands,
1592 using the command @code{help}.
1595 @kindex h @r{(@code{help})}
1598 You can use @code{help} (abbreviated @code{h}) with no arguments to
1599 display a short list of named classes of commands:
1603 List of classes of commands:
1605 aliases -- Aliases of other commands
1606 breakpoints -- Making program stop at certain points
1607 data -- Examining data
1608 files -- Specifying and examining files
1609 internals -- Maintenance commands
1610 obscure -- Obscure features
1611 running -- Running the program
1612 stack -- Examining the stack
1613 status -- Status inquiries
1614 support -- Support facilities
1615 tracepoints -- Tracing of program execution without
1616 stopping the program
1617 user-defined -- User-defined commands
1619 Type "help" followed by a class name for a list of
1620 commands in that class.
1621 Type "help" followed by command name for full
1623 Command name abbreviations are allowed if unambiguous.
1626 @c the above line break eliminates huge line overfull...
1628 @item help @var{class}
1629 Using one of the general help classes as an argument, you can get a
1630 list of the individual commands in that class. For example, here is the
1631 help display for the class @code{status}:
1634 (@value{GDBP}) help status
1639 @c Line break in "show" line falsifies real output, but needed
1640 @c to fit in smallbook page size.
1641 info -- Generic command for showing things
1642 about the program being debugged
1643 show -- Generic command for showing things
1646 Type "help" followed by command name for full
1648 Command name abbreviations are allowed if unambiguous.
1652 @item help @var{command}
1653 With a command name as @code{help} argument, @value{GDBN} displays a
1654 short paragraph on how to use that command.
1657 @item apropos @var{args}
1658 The @code{apropos} command searches through all of the @value{GDBN}
1659 commands, and their documentation, for the regular expression specified in
1660 @var{args}. It prints out all matches found. For example:
1671 set symbol-reloading -- Set dynamic symbol table reloading
1672 multiple times in one run
1673 show symbol-reloading -- Show dynamic symbol table reloading
1674 multiple times in one run
1679 @item complete @var{args}
1680 The @code{complete @var{args}} command lists all the possible completions
1681 for the beginning of a command. Use @var{args} to specify the beginning of the
1682 command you want completed. For example:
1688 @noindent results in:
1699 @noindent This is intended for use by @sc{gnu} Emacs.
1702 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1703 and @code{show} to inquire about the state of your program, or the state
1704 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1705 manual introduces each of them in the appropriate context. The listings
1706 under @code{info} and under @code{show} in the Index point to
1707 all the sub-commands. @xref{Index}.
1712 @kindex i @r{(@code{info})}
1714 This command (abbreviated @code{i}) is for describing the state of your
1715 program. For example, you can show the arguments passed to a function
1716 with @code{info args}, list the registers currently in use with @code{info
1717 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1718 You can get a complete list of the @code{info} sub-commands with
1719 @w{@code{help info}}.
1723 You can assign the result of an expression to an environment variable with
1724 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1725 @code{set prompt $}.
1729 In contrast to @code{info}, @code{show} is for describing the state of
1730 @value{GDBN} itself.
1731 You can change most of the things you can @code{show}, by using the
1732 related command @code{set}; for example, you can control what number
1733 system is used for displays with @code{set radix}, or simply inquire
1734 which is currently in use with @code{show radix}.
1737 To display all the settable parameters and their current
1738 values, you can use @code{show} with no arguments; you may also use
1739 @code{info set}. Both commands produce the same display.
1740 @c FIXME: "info set" violates the rule that "info" is for state of
1741 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1742 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1746 Here are three miscellaneous @code{show} subcommands, all of which are
1747 exceptional in lacking corresponding @code{set} commands:
1750 @kindex show version
1751 @cindex @value{GDBN} version number
1753 Show what version of @value{GDBN} is running. You should include this
1754 information in @value{GDBN} bug-reports. If multiple versions of
1755 @value{GDBN} are in use at your site, you may need to determine which
1756 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1757 commands are introduced, and old ones may wither away. Also, many
1758 system vendors ship variant versions of @value{GDBN}, and there are
1759 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1760 The version number is the same as the one announced when you start
1763 @kindex show copying
1764 @kindex info copying
1765 @cindex display @value{GDBN} copyright
1768 Display information about permission for copying @value{GDBN}.
1770 @kindex show warranty
1771 @kindex info warranty
1773 @itemx info warranty
1774 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1775 if your version of @value{GDBN} comes with one.
1780 @chapter Running Programs Under @value{GDBN}
1782 When you run a program under @value{GDBN}, you must first generate
1783 debugging information when you compile it.
1785 You may start @value{GDBN} with its arguments, if any, in an environment
1786 of your choice. If you are doing native debugging, you may redirect
1787 your program's input and output, debug an already running process, or
1788 kill a child process.
1791 * Compilation:: Compiling for debugging
1792 * Starting:: Starting your program
1793 * Arguments:: Your program's arguments
1794 * Environment:: Your program's environment
1796 * Working Directory:: Your program's working directory
1797 * Input/Output:: Your program's input and output
1798 * Attach:: Debugging an already-running process
1799 * Kill Process:: Killing the child process
1801 * Inferiors and Programs:: Debugging multiple inferiors and programs
1802 * Threads:: Debugging programs with multiple threads
1803 * Forks:: Debugging forks
1804 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1808 @section Compiling for Debugging
1810 In order to debug a program effectively, you need to generate
1811 debugging information when you compile it. This debugging information
1812 is stored in the object file; it describes the data type of each
1813 variable or function and the correspondence between source line numbers
1814 and addresses in the executable code.
1816 To request debugging information, specify the @samp{-g} option when you run
1819 Programs that are to be shipped to your customers are compiled with
1820 optimizations, using the @samp{-O} compiler option. However, some
1821 compilers are unable to handle the @samp{-g} and @samp{-O} options
1822 together. Using those compilers, you cannot generate optimized
1823 executables containing debugging information.
1825 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1826 without @samp{-O}, making it possible to debug optimized code. We
1827 recommend that you @emph{always} use @samp{-g} whenever you compile a
1828 program. You may think your program is correct, but there is no sense
1829 in pushing your luck. For more information, see @ref{Optimized Code}.
1831 Older versions of the @sc{gnu} C compiler permitted a variant option
1832 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1833 format; if your @sc{gnu} C compiler has this option, do not use it.
1835 @value{GDBN} knows about preprocessor macros and can show you their
1836 expansion (@pxref{Macros}). Most compilers do not include information
1837 about preprocessor macros in the debugging information if you specify
1838 the @option{-g} flag alone, because this information is rather large.
1839 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1840 provides macro information if you specify the options
1841 @option{-gdwarf-2} and @option{-g3}; the former option requests
1842 debugging information in the Dwarf 2 format, and the latter requests
1843 ``extra information''. In the future, we hope to find more compact
1844 ways to represent macro information, so that it can be included with
1849 @section Starting your Program
1855 @kindex r @r{(@code{run})}
1858 Use the @code{run} command to start your program under @value{GDBN}.
1859 You must first specify the program name (except on VxWorks) with an
1860 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1861 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1862 (@pxref{Files, ,Commands to Specify Files}).
1866 If you are running your program in an execution environment that
1867 supports processes, @code{run} creates an inferior process and makes
1868 that process run your program. In some environments without processes,
1869 @code{run} jumps to the start of your program. Other targets,
1870 like @samp{remote}, are always running. If you get an error
1871 message like this one:
1874 The "remote" target does not support "run".
1875 Try "help target" or "continue".
1879 then use @code{continue} to run your program. You may need @code{load}
1880 first (@pxref{load}).
1882 The execution of a program is affected by certain information it
1883 receives from its superior. @value{GDBN} provides ways to specify this
1884 information, which you must do @emph{before} starting your program. (You
1885 can change it after starting your program, but such changes only affect
1886 your program the next time you start it.) This information may be
1887 divided into four categories:
1890 @item The @emph{arguments.}
1891 Specify the arguments to give your program as the arguments of the
1892 @code{run} command. If a shell is available on your target, the shell
1893 is used to pass the arguments, so that you may use normal conventions
1894 (such as wildcard expansion or variable substitution) in describing
1896 In Unix systems, you can control which shell is used with the
1897 @code{SHELL} environment variable.
1898 @xref{Arguments, ,Your Program's Arguments}.
1900 @item The @emph{environment.}
1901 Your program normally inherits its environment from @value{GDBN}, but you can
1902 use the @value{GDBN} commands @code{set environment} and @code{unset
1903 environment} to change parts of the environment that affect
1904 your program. @xref{Environment, ,Your Program's Environment}.
1906 @item The @emph{working directory.}
1907 Your program inherits its working directory from @value{GDBN}. You can set
1908 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1909 @xref{Working Directory, ,Your Program's Working Directory}.
1911 @item The @emph{standard input and output.}
1912 Your program normally uses the same device for standard input and
1913 standard output as @value{GDBN} is using. You can redirect input and output
1914 in the @code{run} command line, or you can use the @code{tty} command to
1915 set a different device for your program.
1916 @xref{Input/Output, ,Your Program's Input and Output}.
1919 @emph{Warning:} While input and output redirection work, you cannot use
1920 pipes to pass the output of the program you are debugging to another
1921 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1925 When you issue the @code{run} command, your program begins to execute
1926 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1927 of how to arrange for your program to stop. Once your program has
1928 stopped, you may call functions in your program, using the @code{print}
1929 or @code{call} commands. @xref{Data, ,Examining Data}.
1931 If the modification time of your symbol file has changed since the last
1932 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1933 table, and reads it again. When it does this, @value{GDBN} tries to retain
1934 your current breakpoints.
1939 @cindex run to main procedure
1940 The name of the main procedure can vary from language to language.
1941 With C or C@t{++}, the main procedure name is always @code{main}, but
1942 other languages such as Ada do not require a specific name for their
1943 main procedure. The debugger provides a convenient way to start the
1944 execution of the program and to stop at the beginning of the main
1945 procedure, depending on the language used.
1947 The @samp{start} command does the equivalent of setting a temporary
1948 breakpoint at the beginning of the main procedure and then invoking
1949 the @samp{run} command.
1951 @cindex elaboration phase
1952 Some programs contain an @dfn{elaboration} phase where some startup code is
1953 executed before the main procedure is called. This depends on the
1954 languages used to write your program. In C@t{++}, for instance,
1955 constructors for static and global objects are executed before
1956 @code{main} is called. It is therefore possible that the debugger stops
1957 before reaching the main procedure. However, the temporary breakpoint
1958 will remain to halt execution.
1960 Specify the arguments to give to your program as arguments to the
1961 @samp{start} command. These arguments will be given verbatim to the
1962 underlying @samp{run} command. Note that the same arguments will be
1963 reused if no argument is provided during subsequent calls to
1964 @samp{start} or @samp{run}.
1966 It is sometimes necessary to debug the program during elaboration. In
1967 these cases, using the @code{start} command would stop the execution of
1968 your program too late, as the program would have already completed the
1969 elaboration phase. Under these circumstances, insert breakpoints in your
1970 elaboration code before running your program.
1972 @kindex set exec-wrapper
1973 @item set exec-wrapper @var{wrapper}
1974 @itemx show exec-wrapper
1975 @itemx unset exec-wrapper
1976 When @samp{exec-wrapper} is set, the specified wrapper is used to
1977 launch programs for debugging. @value{GDBN} starts your program
1978 with a shell command of the form @kbd{exec @var{wrapper}
1979 @var{program}}. Quoting is added to @var{program} and its
1980 arguments, but not to @var{wrapper}, so you should add quotes if
1981 appropriate for your shell. The wrapper runs until it executes
1982 your program, and then @value{GDBN} takes control.
1984 You can use any program that eventually calls @code{execve} with
1985 its arguments as a wrapper. Several standard Unix utilities do
1986 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1987 with @code{exec "$@@"} will also work.
1989 For example, you can use @code{env} to pass an environment variable to
1990 the debugged program, without setting the variable in your shell's
1994 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1998 This command is available when debugging locally on most targets, excluding
1999 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2001 @kindex set disable-randomization
2002 @item set disable-randomization
2003 @itemx set disable-randomization on
2004 This option (enabled by default in @value{GDBN}) will turn off the native
2005 randomization of the virtual address space of the started program. This option
2006 is useful for multiple debugging sessions to make the execution better
2007 reproducible and memory addresses reusable across debugging sessions.
2009 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2013 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2016 @item set disable-randomization off
2017 Leave the behavior of the started executable unchanged. Some bugs rear their
2018 ugly heads only when the program is loaded at certain addresses. If your bug
2019 disappears when you run the program under @value{GDBN}, that might be because
2020 @value{GDBN} by default disables the address randomization on platforms, such
2021 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2022 disable-randomization off} to try to reproduce such elusive bugs.
2024 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2025 It protects the programs against some kinds of security attacks. In these
2026 cases the attacker needs to know the exact location of a concrete executable
2027 code. Randomizing its location makes it impossible to inject jumps misusing
2028 a code at its expected addresses.
2030 Prelinking shared libraries provides a startup performance advantage but it
2031 makes addresses in these libraries predictable for privileged processes by
2032 having just unprivileged access at the target system. Reading the shared
2033 library binary gives enough information for assembling the malicious code
2034 misusing it. Still even a prelinked shared library can get loaded at a new
2035 random address just requiring the regular relocation process during the
2036 startup. Shared libraries not already prelinked are always loaded at
2037 a randomly chosen address.
2039 Position independent executables (PIE) contain position independent code
2040 similar to the shared libraries and therefore such executables get loaded at
2041 a randomly chosen address upon startup. PIE executables always load even
2042 already prelinked shared libraries at a random address. You can build such
2043 executable using @command{gcc -fPIE -pie}.
2045 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2046 (as long as the randomization is enabled).
2048 @item show disable-randomization
2049 Show the current setting of the explicit disable of the native randomization of
2050 the virtual address space of the started program.
2055 @section Your Program's Arguments
2057 @cindex arguments (to your program)
2058 The arguments to your program can be specified by the arguments of the
2060 They are passed to a shell, which expands wildcard characters and
2061 performs redirection of I/O, and thence to your program. Your
2062 @code{SHELL} environment variable (if it exists) specifies what shell
2063 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2064 the default shell (@file{/bin/sh} on Unix).
2066 On non-Unix systems, the program is usually invoked directly by
2067 @value{GDBN}, which emulates I/O redirection via the appropriate system
2068 calls, and the wildcard characters are expanded by the startup code of
2069 the program, not by the shell.
2071 @code{run} with no arguments uses the same arguments used by the previous
2072 @code{run}, or those set by the @code{set args} command.
2077 Specify the arguments to be used the next time your program is run. If
2078 @code{set args} has no arguments, @code{run} executes your program
2079 with no arguments. Once you have run your program with arguments,
2080 using @code{set args} before the next @code{run} is the only way to run
2081 it again without arguments.
2085 Show the arguments to give your program when it is started.
2089 @section Your Program's Environment
2091 @cindex environment (of your program)
2092 The @dfn{environment} consists of a set of environment variables and
2093 their values. Environment variables conventionally record such things as
2094 your user name, your home directory, your terminal type, and your search
2095 path for programs to run. Usually you set up environment variables with
2096 the shell and they are inherited by all the other programs you run. When
2097 debugging, it can be useful to try running your program with a modified
2098 environment without having to start @value{GDBN} over again.
2102 @item path @var{directory}
2103 Add @var{directory} to the front of the @code{PATH} environment variable
2104 (the search path for executables) that will be passed to your program.
2105 The value of @code{PATH} used by @value{GDBN} does not change.
2106 You may specify several directory names, separated by whitespace or by a
2107 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2108 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2109 is moved to the front, so it is searched sooner.
2111 You can use the string @samp{$cwd} to refer to whatever is the current
2112 working directory at the time @value{GDBN} searches the path. If you
2113 use @samp{.} instead, it refers to the directory where you executed the
2114 @code{path} command. @value{GDBN} replaces @samp{.} in the
2115 @var{directory} argument (with the current path) before adding
2116 @var{directory} to the search path.
2117 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2118 @c document that, since repeating it would be a no-op.
2122 Display the list of search paths for executables (the @code{PATH}
2123 environment variable).
2125 @kindex show environment
2126 @item show environment @r{[}@var{varname}@r{]}
2127 Print the value of environment variable @var{varname} to be given to
2128 your program when it starts. If you do not supply @var{varname},
2129 print the names and values of all environment variables to be given to
2130 your program. You can abbreviate @code{environment} as @code{env}.
2132 @kindex set environment
2133 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2134 Set environment variable @var{varname} to @var{value}. The value
2135 changes for your program only, not for @value{GDBN} itself. @var{value} may
2136 be any string; the values of environment variables are just strings, and
2137 any interpretation is supplied by your program itself. The @var{value}
2138 parameter is optional; if it is eliminated, the variable is set to a
2140 @c "any string" here does not include leading, trailing
2141 @c blanks. Gnu asks: does anyone care?
2143 For example, this command:
2150 tells the debugged program, when subsequently run, that its user is named
2151 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2152 are not actually required.)
2154 @kindex unset environment
2155 @item unset environment @var{varname}
2156 Remove variable @var{varname} from the environment to be passed to your
2157 program. This is different from @samp{set env @var{varname} =};
2158 @code{unset environment} removes the variable from the environment,
2159 rather than assigning it an empty value.
2162 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2164 by your @code{SHELL} environment variable if it exists (or
2165 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2166 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2167 @file{.bashrc} for BASH---any variables you set in that file affect
2168 your program. You may wish to move setting of environment variables to
2169 files that are only run when you sign on, such as @file{.login} or
2172 @node Working Directory
2173 @section Your Program's Working Directory
2175 @cindex working directory (of your program)
2176 Each time you start your program with @code{run}, it inherits its
2177 working directory from the current working directory of @value{GDBN}.
2178 The @value{GDBN} working directory is initially whatever it inherited
2179 from its parent process (typically the shell), but you can specify a new
2180 working directory in @value{GDBN} with the @code{cd} command.
2182 The @value{GDBN} working directory also serves as a default for the commands
2183 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2188 @cindex change working directory
2189 @item cd @var{directory}
2190 Set the @value{GDBN} working directory to @var{directory}.
2194 Print the @value{GDBN} working directory.
2197 It is generally impossible to find the current working directory of
2198 the process being debugged (since a program can change its directory
2199 during its run). If you work on a system where @value{GDBN} is
2200 configured with the @file{/proc} support, you can use the @code{info
2201 proc} command (@pxref{SVR4 Process Information}) to find out the
2202 current working directory of the debuggee.
2205 @section Your Program's Input and Output
2210 By default, the program you run under @value{GDBN} does input and output to
2211 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2212 to its own terminal modes to interact with you, but it records the terminal
2213 modes your program was using and switches back to them when you continue
2214 running your program.
2217 @kindex info terminal
2219 Displays information recorded by @value{GDBN} about the terminal modes your
2223 You can redirect your program's input and/or output using shell
2224 redirection with the @code{run} command. For example,
2231 starts your program, diverting its output to the file @file{outfile}.
2234 @cindex controlling terminal
2235 Another way to specify where your program should do input and output is
2236 with the @code{tty} command. This command accepts a file name as
2237 argument, and causes this file to be the default for future @code{run}
2238 commands. It also resets the controlling terminal for the child
2239 process, for future @code{run} commands. For example,
2246 directs that processes started with subsequent @code{run} commands
2247 default to do input and output on the terminal @file{/dev/ttyb} and have
2248 that as their controlling terminal.
2250 An explicit redirection in @code{run} overrides the @code{tty} command's
2251 effect on the input/output device, but not its effect on the controlling
2254 When you use the @code{tty} command or redirect input in the @code{run}
2255 command, only the input @emph{for your program} is affected. The input
2256 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2257 for @code{set inferior-tty}.
2259 @cindex inferior tty
2260 @cindex set inferior controlling terminal
2261 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2262 display the name of the terminal that will be used for future runs of your
2266 @item set inferior-tty /dev/ttyb
2267 @kindex set inferior-tty
2268 Set the tty for the program being debugged to /dev/ttyb.
2270 @item show inferior-tty
2271 @kindex show inferior-tty
2272 Show the current tty for the program being debugged.
2276 @section Debugging an Already-running Process
2281 @item attach @var{process-id}
2282 This command attaches to a running process---one that was started
2283 outside @value{GDBN}. (@code{info files} shows your active
2284 targets.) The command takes as argument a process ID. The usual way to
2285 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2286 or with the @samp{jobs -l} shell command.
2288 @code{attach} does not repeat if you press @key{RET} a second time after
2289 executing the command.
2292 To use @code{attach}, your program must be running in an environment
2293 which supports processes; for example, @code{attach} does not work for
2294 programs on bare-board targets that lack an operating system. You must
2295 also have permission to send the process a signal.
2297 When you use @code{attach}, the debugger finds the program running in
2298 the process first by looking in the current working directory, then (if
2299 the program is not found) by using the source file search path
2300 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2301 the @code{file} command to load the program. @xref{Files, ,Commands to
2304 The first thing @value{GDBN} does after arranging to debug the specified
2305 process is to stop it. You can examine and modify an attached process
2306 with all the @value{GDBN} commands that are ordinarily available when
2307 you start processes with @code{run}. You can insert breakpoints; you
2308 can step and continue; you can modify storage. If you would rather the
2309 process continue running, you may use the @code{continue} command after
2310 attaching @value{GDBN} to the process.
2315 When you have finished debugging the attached process, you can use the
2316 @code{detach} command to release it from @value{GDBN} control. Detaching
2317 the process continues its execution. After the @code{detach} command,
2318 that process and @value{GDBN} become completely independent once more, and you
2319 are ready to @code{attach} another process or start one with @code{run}.
2320 @code{detach} does not repeat if you press @key{RET} again after
2321 executing the command.
2324 If you exit @value{GDBN} while you have an attached process, you detach
2325 that process. If you use the @code{run} command, you kill that process.
2326 By default, @value{GDBN} asks for confirmation if you try to do either of these
2327 things; you can control whether or not you need to confirm by using the
2328 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2332 @section Killing the Child Process
2337 Kill the child process in which your program is running under @value{GDBN}.
2340 This command is useful if you wish to debug a core dump instead of a
2341 running process. @value{GDBN} ignores any core dump file while your program
2344 On some operating systems, a program cannot be executed outside @value{GDBN}
2345 while you have breakpoints set on it inside @value{GDBN}. You can use the
2346 @code{kill} command in this situation to permit running your program
2347 outside the debugger.
2349 The @code{kill} command is also useful if you wish to recompile and
2350 relink your program, since on many systems it is impossible to modify an
2351 executable file while it is running in a process. In this case, when you
2352 next type @code{run}, @value{GDBN} notices that the file has changed, and
2353 reads the symbol table again (while trying to preserve your current
2354 breakpoint settings).
2356 @node Inferiors and Programs
2357 @section Debugging Multiple Inferiors and Programs
2359 @value{GDBN} lets you run and debug multiple programs in a single
2360 session. In addition, @value{GDBN} on some systems may let you run
2361 several programs simultaneously (otherwise you have to exit from one
2362 before starting another). In the most general case, you can have
2363 multiple threads of execution in each of multiple processes, launched
2364 from multiple executables.
2367 @value{GDBN} represents the state of each program execution with an
2368 object called an @dfn{inferior}. An inferior typically corresponds to
2369 a process, but is more general and applies also to targets that do not
2370 have processes. Inferiors may be created before a process runs, and
2371 may be retained after a process exits. Inferiors have unique
2372 identifiers that are different from process ids. Usually each
2373 inferior will also have its own distinct address space, although some
2374 embedded targets may have several inferiors running in different parts
2375 of a single address space. Each inferior may in turn have multiple
2376 threads running in it.
2378 To find out what inferiors exist at any moment, use @w{@code{info
2382 @kindex info inferiors
2383 @item info inferiors
2384 Print a list of all inferiors currently being managed by @value{GDBN}.
2386 @value{GDBN} displays for each inferior (in this order):
2390 the inferior number assigned by @value{GDBN}
2393 the target system's inferior identifier
2396 the name of the executable the inferior is running.
2401 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2402 indicates the current inferior.
2406 @c end table here to get a little more width for example
2409 (@value{GDBP}) info inferiors
2410 Num Description Executable
2411 2 process 2307 hello
2412 * 1 process 3401 goodbye
2415 To switch focus between inferiors, use the @code{inferior} command:
2418 @kindex inferior @var{infno}
2419 @item inferior @var{infno}
2420 Make inferior number @var{infno} the current inferior. The argument
2421 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2422 in the first field of the @samp{info inferiors} display.
2426 You can get multiple executables into a debugging session via the
2427 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2428 systems @value{GDBN} can add inferiors to the debug session
2429 automatically by following calls to @code{fork} and @code{exec}. To
2430 remove inferiors from the debugging session use the
2431 @w{@code{remove-inferior}} command.
2434 @kindex add-inferior
2435 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2436 Adds @var{n} inferiors to be run using @var{executable} as the
2437 executable. @var{n} defaults to 1. If no executable is specified,
2438 the inferiors begins empty, with no program. You can still assign or
2439 change the program assigned to the inferior at any time by using the
2440 @code{file} command with the executable name as its argument.
2442 @kindex clone-inferior
2443 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2444 Adds @var{n} inferiors ready to execute the same program as inferior
2445 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2446 number of the current inferior. This is a convenient command when you
2447 want to run another instance of the inferior you are debugging.
2450 (@value{GDBP}) info inferiors
2451 Num Description Executable
2452 * 1 process 29964 helloworld
2453 (@value{GDBP}) clone-inferior
2456 (@value{GDBP}) info inferiors
2457 Num Description Executable
2459 * 1 process 29964 helloworld
2462 You can now simply switch focus to inferior 2 and run it.
2464 @kindex remove-inferior
2465 @item remove-inferior @var{infno}
2466 Removes the inferior @var{infno}. It is not possible to remove an
2467 inferior that is running with this command. For those, use the
2468 @code{kill} or @code{detach} command first.
2472 To quit debugging one of the running inferiors that is not the current
2473 inferior, you can either detach from it by using the @w{@code{detach
2474 inferior}} command (allowing it to run independently), or kill it
2475 using the @w{@code{kill inferior}} command:
2478 @kindex detach inferior @var{infno}
2479 @item detach inferior @var{infno}
2480 Detach from the inferior identified by @value{GDBN} inferior number
2481 @var{infno}, and remove it from the inferior list.
2483 @kindex kill inferior @var{infno}
2484 @item kill inferior @var{infno}
2485 Kill the inferior identified by @value{GDBN} inferior number
2486 @var{infno}, and remove it from the inferior list.
2489 After the successful completion of a command such as @code{detach},
2490 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2491 a normal process exit, the inferior is still valid and listed with
2492 @code{info inferiors}, ready to be restarted.
2495 To be notified when inferiors are started or exit under @value{GDBN}'s
2496 control use @w{@code{set print inferior-events}}:
2499 @kindex set print inferior-events
2500 @cindex print messages on inferior start and exit
2501 @item set print inferior-events
2502 @itemx set print inferior-events on
2503 @itemx set print inferior-events off
2504 The @code{set print inferior-events} command allows you to enable or
2505 disable printing of messages when @value{GDBN} notices that new
2506 inferiors have started or that inferiors have exited or have been
2507 detached. By default, these messages will not be printed.
2509 @kindex show print inferior-events
2510 @item show print inferior-events
2511 Show whether messages will be printed when @value{GDBN} detects that
2512 inferiors have started, exited or have been detached.
2515 Many commands will work the same with multiple programs as with a
2516 single program: e.g., @code{print myglobal} will simply display the
2517 value of @code{myglobal} in the current inferior.
2520 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2521 get more info about the relationship of inferiors, programs, address
2522 spaces in a debug session. You can do that with the @w{@code{maint
2523 info program-spaces}} command.
2526 @kindex maint info program-spaces
2527 @item maint info program-spaces
2528 Print a list of all program spaces currently being managed by
2531 @value{GDBN} displays for each program space (in this order):
2535 the program space number assigned by @value{GDBN}
2538 the name of the executable loaded into the program space, with e.g.,
2539 the @code{file} command.
2544 An asterisk @samp{*} preceding the @value{GDBN} program space number
2545 indicates the current program space.
2547 In addition, below each program space line, @value{GDBN} prints extra
2548 information that isn't suitable to display in tabular form. For
2549 example, the list of inferiors bound to the program space.
2552 (@value{GDBP}) maint info program-spaces
2555 Bound inferiors: ID 1 (process 21561)
2559 Here we can see that no inferior is running the program @code{hello},
2560 while @code{process 21561} is running the program @code{goodbye}. On
2561 some targets, it is possible that multiple inferiors are bound to the
2562 same program space. The most common example is that of debugging both
2563 the parent and child processes of a @code{vfork} call. For example,
2566 (@value{GDBP}) maint info program-spaces
2569 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2572 Here, both inferior 2 and inferior 1 are running in the same program
2573 space as a result of inferior 1 having executed a @code{vfork} call.
2577 @section Debugging Programs with Multiple Threads
2579 @cindex threads of execution
2580 @cindex multiple threads
2581 @cindex switching threads
2582 In some operating systems, such as HP-UX and Solaris, a single program
2583 may have more than one @dfn{thread} of execution. The precise semantics
2584 of threads differ from one operating system to another, but in general
2585 the threads of a single program are akin to multiple processes---except
2586 that they share one address space (that is, they can all examine and
2587 modify the same variables). On the other hand, each thread has its own
2588 registers and execution stack, and perhaps private memory.
2590 @value{GDBN} provides these facilities for debugging multi-thread
2594 @item automatic notification of new threads
2595 @item @samp{thread @var{threadno}}, a command to switch among threads
2596 @item @samp{info threads}, a command to inquire about existing threads
2597 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2598 a command to apply a command to a list of threads
2599 @item thread-specific breakpoints
2600 @item @samp{set print thread-events}, which controls printing of
2601 messages on thread start and exit.
2602 @item @samp{set libthread-db-search-path @var{path}}, which lets
2603 the user specify which @code{libthread_db} to use if the default choice
2604 isn't compatible with the program.
2608 @emph{Warning:} These facilities are not yet available on every
2609 @value{GDBN} configuration where the operating system supports threads.
2610 If your @value{GDBN} does not support threads, these commands have no
2611 effect. For example, a system without thread support shows no output
2612 from @samp{info threads}, and always rejects the @code{thread} command,
2616 (@value{GDBP}) info threads
2617 (@value{GDBP}) thread 1
2618 Thread ID 1 not known. Use the "info threads" command to
2619 see the IDs of currently known threads.
2621 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2622 @c doesn't support threads"?
2625 @cindex focus of debugging
2626 @cindex current thread
2627 The @value{GDBN} thread debugging facility allows you to observe all
2628 threads while your program runs---but whenever @value{GDBN} takes
2629 control, one thread in particular is always the focus of debugging.
2630 This thread is called the @dfn{current thread}. Debugging commands show
2631 program information from the perspective of the current thread.
2633 @cindex @code{New} @var{systag} message
2634 @cindex thread identifier (system)
2635 @c FIXME-implementors!! It would be more helpful if the [New...] message
2636 @c included GDB's numeric thread handle, so you could just go to that
2637 @c thread without first checking `info threads'.
2638 Whenever @value{GDBN} detects a new thread in your program, it displays
2639 the target system's identification for the thread with a message in the
2640 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2641 whose form varies depending on the particular system. For example, on
2642 @sc{gnu}/Linux, you might see
2645 [New Thread 46912507313328 (LWP 25582)]
2649 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2650 the @var{systag} is simply something like @samp{process 368}, with no
2653 @c FIXME!! (1) Does the [New...] message appear even for the very first
2654 @c thread of a program, or does it only appear for the
2655 @c second---i.e.@: when it becomes obvious we have a multithread
2657 @c (2) *Is* there necessarily a first thread always? Or do some
2658 @c multithread systems permit starting a program with multiple
2659 @c threads ab initio?
2661 @cindex thread number
2662 @cindex thread identifier (GDB)
2663 For debugging purposes, @value{GDBN} associates its own thread
2664 number---always a single integer---with each thread in your program.
2667 @kindex info threads
2669 Display a summary of all threads currently in your
2670 program. @value{GDBN} displays for each thread (in this order):
2674 the thread number assigned by @value{GDBN}
2677 the target system's thread identifier (@var{systag})
2680 the current stack frame summary for that thread
2684 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2685 indicates the current thread.
2689 @c end table here to get a little more width for example
2692 (@value{GDBP}) info threads
2693 3 process 35 thread 27 0x34e5 in sigpause ()
2694 2 process 35 thread 23 0x34e5 in sigpause ()
2695 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2701 @cindex debugging multithreaded programs (on HP-UX)
2702 @cindex thread identifier (GDB), on HP-UX
2703 For debugging purposes, @value{GDBN} associates its own thread
2704 number---a small integer assigned in thread-creation order---with each
2705 thread in your program.
2707 @cindex @code{New} @var{systag} message, on HP-UX
2708 @cindex thread identifier (system), on HP-UX
2709 @c FIXME-implementors!! It would be more helpful if the [New...] message
2710 @c included GDB's numeric thread handle, so you could just go to that
2711 @c thread without first checking `info threads'.
2712 Whenever @value{GDBN} detects a new thread in your program, it displays
2713 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2714 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2715 whose form varies depending on the particular system. For example, on
2719 [New thread 2 (system thread 26594)]
2723 when @value{GDBN} notices a new thread.
2726 @kindex info threads (HP-UX)
2728 Display a summary of all threads currently in your
2729 program. @value{GDBN} displays for each thread (in this order):
2732 @item the thread number assigned by @value{GDBN}
2734 @item the target system's thread identifier (@var{systag})
2736 @item the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2749 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2751 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2752 from /usr/lib/libc.2
2753 1 system thread 27905 0x7b003498 in _brk () \@*
2754 from /usr/lib/libc.2
2757 On Solaris, you can display more information about user threads with a
2758 Solaris-specific command:
2761 @item maint info sol-threads
2762 @kindex maint info sol-threads
2763 @cindex thread info (Solaris)
2764 Display info on Solaris user threads.
2768 @kindex thread @var{threadno}
2769 @item thread @var{threadno}
2770 Make thread number @var{threadno} the current thread. The command
2771 argument @var{threadno} is the internal @value{GDBN} thread number, as
2772 shown in the first field of the @samp{info threads} display.
2773 @value{GDBN} responds by displaying the system identifier of the thread
2774 you selected, and its current stack frame summary:
2777 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2778 (@value{GDBP}) thread 2
2779 [Switching to process 35 thread 23]
2780 0x34e5 in sigpause ()
2784 As with the @samp{[New @dots{}]} message, the form of the text after
2785 @samp{Switching to} depends on your system's conventions for identifying
2788 @kindex thread apply
2789 @cindex apply command to several threads
2790 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2791 The @code{thread apply} command allows you to apply the named
2792 @var{command} to one or more threads. Specify the numbers of the
2793 threads that you want affected with the command argument
2794 @var{threadno}. It can be a single thread number, one of the numbers
2795 shown in the first field of the @samp{info threads} display; or it
2796 could be a range of thread numbers, as in @code{2-4}. To apply a
2797 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @kindex set print thread-events
2800 @cindex print messages on thread start and exit
2801 @item set print thread-events
2802 @itemx set print thread-events on
2803 @itemx set print thread-events off
2804 The @code{set print thread-events} command allows you to enable or
2805 disable printing of messages when @value{GDBN} notices that new threads have
2806 started or that threads have exited. By default, these messages will
2807 be printed if detection of these events is supported by the target.
2808 Note that these messages cannot be disabled on all targets.
2810 @kindex show print thread-events
2811 @item show print thread-events
2812 Show whether messages will be printed when @value{GDBN} detects that threads
2813 have started and exited.
2816 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2817 more information about how @value{GDBN} behaves when you stop and start
2818 programs with multiple threads.
2820 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2821 watchpoints in programs with multiple threads.
2824 @kindex set libthread-db-search-path
2825 @cindex search path for @code{libthread_db}
2826 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2827 If this variable is set, @var{path} is a colon-separated list of
2828 directories @value{GDBN} will use to search for @code{libthread_db}.
2829 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2832 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2833 @code{libthread_db} library to obtain information about threads in the
2834 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2835 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2836 with default system shared library directories, and finally the directory
2837 from which @code{libpthread} was loaded in the inferior process.
2839 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2840 @value{GDBN} attempts to initialize it with the current inferior process.
2841 If this initialization fails (which could happen because of a version
2842 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2843 will unload @code{libthread_db}, and continue with the next directory.
2844 If none of @code{libthread_db} libraries initialize successfully,
2845 @value{GDBN} will issue a warning and thread debugging will be disabled.
2847 Setting @code{libthread-db-search-path} is currently implemented
2848 only on some platforms.
2850 @kindex show libthread-db-search-path
2851 @item show libthread-db-search-path
2852 Display current libthread_db search path.
2856 @section Debugging Forks
2858 @cindex fork, debugging programs which call
2859 @cindex multiple processes
2860 @cindex processes, multiple
2861 On most systems, @value{GDBN} has no special support for debugging
2862 programs which create additional processes using the @code{fork}
2863 function. When a program forks, @value{GDBN} will continue to debug the
2864 parent process and the child process will run unimpeded. If you have
2865 set a breakpoint in any code which the child then executes, the child
2866 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2867 will cause it to terminate.
2869 However, if you want to debug the child process there is a workaround
2870 which isn't too painful. Put a call to @code{sleep} in the code which
2871 the child process executes after the fork. It may be useful to sleep
2872 only if a certain environment variable is set, or a certain file exists,
2873 so that the delay need not occur when you don't want to run @value{GDBN}
2874 on the child. While the child is sleeping, use the @code{ps} program to
2875 get its process ID. Then tell @value{GDBN} (a new invocation of
2876 @value{GDBN} if you are also debugging the parent process) to attach to
2877 the child process (@pxref{Attach}). From that point on you can debug
2878 the child process just like any other process which you attached to.
2880 On some systems, @value{GDBN} provides support for debugging programs that
2881 create additional processes using the @code{fork} or @code{vfork} functions.
2882 Currently, the only platforms with this feature are HP-UX (11.x and later
2883 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2885 By default, when a program forks, @value{GDBN} will continue to debug
2886 the parent process and the child process will run unimpeded.
2888 If you want to follow the child process instead of the parent process,
2889 use the command @w{@code{set follow-fork-mode}}.
2892 @kindex set follow-fork-mode
2893 @item set follow-fork-mode @var{mode}
2894 Set the debugger response to a program call of @code{fork} or
2895 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2896 process. The @var{mode} argument can be:
2900 The original process is debugged after a fork. The child process runs
2901 unimpeded. This is the default.
2904 The new process is debugged after a fork. The parent process runs
2909 @kindex show follow-fork-mode
2910 @item show follow-fork-mode
2911 Display the current debugger response to a @code{fork} or @code{vfork} call.
2914 @cindex debugging multiple processes
2915 On Linux, if you want to debug both the parent and child processes, use the
2916 command @w{@code{set detach-on-fork}}.
2919 @kindex set detach-on-fork
2920 @item set detach-on-fork @var{mode}
2921 Tells gdb whether to detach one of the processes after a fork, or
2922 retain debugger control over them both.
2926 The child process (or parent process, depending on the value of
2927 @code{follow-fork-mode}) will be detached and allowed to run
2928 independently. This is the default.
2931 Both processes will be held under the control of @value{GDBN}.
2932 One process (child or parent, depending on the value of
2933 @code{follow-fork-mode}) is debugged as usual, while the other
2938 @kindex show detach-on-fork
2939 @item show detach-on-fork
2940 Show whether detach-on-fork mode is on/off.
2943 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2944 will retain control of all forked processes (including nested forks).
2945 You can list the forked processes under the control of @value{GDBN} by
2946 using the @w{@code{info inferiors}} command, and switch from one fork
2947 to another by using the @code{inferior} command (@pxref{Inferiors and
2948 Programs, ,Debugging Multiple Inferiors and Programs}).
2950 To quit debugging one of the forked processes, you can either detach
2951 from it by using the @w{@code{detach inferior}} command (allowing it
2952 to run independently), or kill it using the @w{@code{kill inferior}}
2953 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2956 If you ask to debug a child process and a @code{vfork} is followed by an
2957 @code{exec}, @value{GDBN} executes the new target up to the first
2958 breakpoint in the new target. If you have a breakpoint set on
2959 @code{main} in your original program, the breakpoint will also be set on
2960 the child process's @code{main}.
2962 On some systems, when a child process is spawned by @code{vfork}, you
2963 cannot debug the child or parent until an @code{exec} call completes.
2965 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2966 call executes, the new target restarts. To restart the parent
2967 process, use the @code{file} command with the parent executable name
2968 as its argument. By default, after an @code{exec} call executes,
2969 @value{GDBN} discards the symbols of the previous executable image.
2970 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2974 @kindex set follow-exec-mode
2975 @item set follow-exec-mode @var{mode}
2977 Set debugger response to a program call of @code{exec}. An
2978 @code{exec} call replaces the program image of a process.
2980 @code{follow-exec-mode} can be:
2984 @value{GDBN} creates a new inferior and rebinds the process to this
2985 new inferior. The program the process was running before the
2986 @code{exec} call can be restarted afterwards by restarting the
2992 (@value{GDBP}) info inferiors
2994 Id Description Executable
2997 process 12020 is executing new program: prog2
2998 Program exited normally.
2999 (@value{GDBP}) info inferiors
3000 Id Description Executable
3006 @value{GDBN} keeps the process bound to the same inferior. The new
3007 executable image replaces the previous executable loaded in the
3008 inferior. Restarting the inferior after the @code{exec} call, with
3009 e.g., the @code{run} command, restarts the executable the process was
3010 running after the @code{exec} call. This is the default mode.
3015 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3029 You can use the @code{catch} command to make @value{GDBN} stop whenever
3030 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3031 Catchpoints, ,Setting Catchpoints}.
3033 @node Checkpoint/Restart
3034 @section Setting a @emph{Bookmark} to Return to Later
3039 @cindex snapshot of a process
3040 @cindex rewind program state
3042 On certain operating systems@footnote{Currently, only
3043 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3044 program's state, called a @dfn{checkpoint}, and come back to it
3047 Returning to a checkpoint effectively undoes everything that has
3048 happened in the program since the @code{checkpoint} was saved. This
3049 includes changes in memory, registers, and even (within some limits)
3050 system state. Effectively, it is like going back in time to the
3051 moment when the checkpoint was saved.
3053 Thus, if you're stepping thru a program and you think you're
3054 getting close to the point where things go wrong, you can save
3055 a checkpoint. Then, if you accidentally go too far and miss
3056 the critical statement, instead of having to restart your program
3057 from the beginning, you can just go back to the checkpoint and
3058 start again from there.
3060 This can be especially useful if it takes a lot of time or
3061 steps to reach the point where you think the bug occurs.
3063 To use the @code{checkpoint}/@code{restart} method of debugging:
3068 Save a snapshot of the debugged program's current execution state.
3069 The @code{checkpoint} command takes no arguments, but each checkpoint
3070 is assigned a small integer id, similar to a breakpoint id.
3072 @kindex info checkpoints
3073 @item info checkpoints
3074 List the checkpoints that have been saved in the current debugging
3075 session. For each checkpoint, the following information will be
3082 @item Source line, or label
3085 @kindex restart @var{checkpoint-id}
3086 @item restart @var{checkpoint-id}
3087 Restore the program state that was saved as checkpoint number
3088 @var{checkpoint-id}. All program variables, registers, stack frames
3089 etc.@: will be returned to the values that they had when the checkpoint
3090 was saved. In essence, gdb will ``wind back the clock'' to the point
3091 in time when the checkpoint was saved.
3093 Note that breakpoints, @value{GDBN} variables, command history etc.
3094 are not affected by restoring a checkpoint. In general, a checkpoint
3095 only restores things that reside in the program being debugged, not in
3098 @kindex delete checkpoint @var{checkpoint-id}
3099 @item delete checkpoint @var{checkpoint-id}
3100 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3104 Returning to a previously saved checkpoint will restore the user state
3105 of the program being debugged, plus a significant subset of the system
3106 (OS) state, including file pointers. It won't ``un-write'' data from
3107 a file, but it will rewind the file pointer to the previous location,
3108 so that the previously written data can be overwritten. For files
3109 opened in read mode, the pointer will also be restored so that the
3110 previously read data can be read again.
3112 Of course, characters that have been sent to a printer (or other
3113 external device) cannot be ``snatched back'', and characters received
3114 from eg.@: a serial device can be removed from internal program buffers,
3115 but they cannot be ``pushed back'' into the serial pipeline, ready to
3116 be received again. Similarly, the actual contents of files that have
3117 been changed cannot be restored (at this time).
3119 However, within those constraints, you actually can ``rewind'' your
3120 program to a previously saved point in time, and begin debugging it
3121 again --- and you can change the course of events so as to debug a
3122 different execution path this time.
3124 @cindex checkpoints and process id
3125 Finally, there is one bit of internal program state that will be
3126 different when you return to a checkpoint --- the program's process
3127 id. Each checkpoint will have a unique process id (or @var{pid}),
3128 and each will be different from the program's original @var{pid}.
3129 If your program has saved a local copy of its process id, this could
3130 potentially pose a problem.
3132 @subsection A Non-obvious Benefit of Using Checkpoints
3134 On some systems such as @sc{gnu}/Linux, address space randomization
3135 is performed on new processes for security reasons. This makes it
3136 difficult or impossible to set a breakpoint, or watchpoint, on an
3137 absolute address if you have to restart the program, since the
3138 absolute location of a symbol will change from one execution to the
3141 A checkpoint, however, is an @emph{identical} copy of a process.
3142 Therefore if you create a checkpoint at (eg.@:) the start of main,
3143 and simply return to that checkpoint instead of restarting the
3144 process, you can avoid the effects of address randomization and
3145 your symbols will all stay in the same place.
3148 @chapter Stopping and Continuing
3150 The principal purposes of using a debugger are so that you can stop your
3151 program before it terminates; or so that, if your program runs into
3152 trouble, you can investigate and find out why.
3154 Inside @value{GDBN}, your program may stop for any of several reasons,
3155 such as a signal, a breakpoint, or reaching a new line after a
3156 @value{GDBN} command such as @code{step}. You may then examine and
3157 change variables, set new breakpoints or remove old ones, and then
3158 continue execution. Usually, the messages shown by @value{GDBN} provide
3159 ample explanation of the status of your program---but you can also
3160 explicitly request this information at any time.
3163 @kindex info program
3165 Display information about the status of your program: whether it is
3166 running or not, what process it is, and why it stopped.
3170 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3171 * Continuing and Stepping:: Resuming execution
3173 * Thread Stops:: Stopping and starting multi-thread programs
3177 @section Breakpoints, Watchpoints, and Catchpoints
3180 A @dfn{breakpoint} makes your program stop whenever a certain point in
3181 the program is reached. For each breakpoint, you can add conditions to
3182 control in finer detail whether your program stops. You can set
3183 breakpoints with the @code{break} command and its variants (@pxref{Set
3184 Breaks, ,Setting Breakpoints}), to specify the place where your program
3185 should stop by line number, function name or exact address in the
3188 On some systems, you can set breakpoints in shared libraries before
3189 the executable is run. There is a minor limitation on HP-UX systems:
3190 you must wait until the executable is run in order to set breakpoints
3191 in shared library routines that are not called directly by the program
3192 (for example, routines that are arguments in a @code{pthread_create}
3196 @cindex data breakpoints
3197 @cindex memory tracing
3198 @cindex breakpoint on memory address
3199 @cindex breakpoint on variable modification
3200 A @dfn{watchpoint} is a special breakpoint that stops your program
3201 when the value of an expression changes. The expression may be a value
3202 of a variable, or it could involve values of one or more variables
3203 combined by operators, such as @samp{a + b}. This is sometimes called
3204 @dfn{data breakpoints}. You must use a different command to set
3205 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3206 from that, you can manage a watchpoint like any other breakpoint: you
3207 enable, disable, and delete both breakpoints and watchpoints using the
3210 You can arrange to have values from your program displayed automatically
3211 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3215 @cindex breakpoint on events
3216 A @dfn{catchpoint} is another special breakpoint that stops your program
3217 when a certain kind of event occurs, such as the throwing of a C@t{++}
3218 exception or the loading of a library. As with watchpoints, you use a
3219 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3220 Catchpoints}), but aside from that, you can manage a catchpoint like any
3221 other breakpoint. (To stop when your program receives a signal, use the
3222 @code{handle} command; see @ref{Signals, ,Signals}.)
3224 @cindex breakpoint numbers
3225 @cindex numbers for breakpoints
3226 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3227 catchpoint when you create it; these numbers are successive integers
3228 starting with one. In many of the commands for controlling various
3229 features of breakpoints you use the breakpoint number to say which
3230 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3231 @dfn{disabled}; if disabled, it has no effect on your program until you
3234 @cindex breakpoint ranges
3235 @cindex ranges of breakpoints
3236 Some @value{GDBN} commands accept a range of breakpoints on which to
3237 operate. A breakpoint range is either a single breakpoint number, like
3238 @samp{5}, or two such numbers, in increasing order, separated by a
3239 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3240 all breakpoints in that range are operated on.
3243 * Set Breaks:: Setting breakpoints
3244 * Set Watchpoints:: Setting watchpoints
3245 * Set Catchpoints:: Setting catchpoints
3246 * Delete Breaks:: Deleting breakpoints
3247 * Disabling:: Disabling breakpoints
3248 * Conditions:: Break conditions
3249 * Break Commands:: Breakpoint command lists
3250 * Error in Breakpoints:: ``Cannot insert breakpoints''
3251 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3255 @subsection Setting Breakpoints
3257 @c FIXME LMB what does GDB do if no code on line of breakpt?
3258 @c consider in particular declaration with/without initialization.
3260 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3263 @kindex b @r{(@code{break})}
3264 @vindex $bpnum@r{, convenience variable}
3265 @cindex latest breakpoint
3266 Breakpoints are set with the @code{break} command (abbreviated
3267 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3268 number of the breakpoint you've set most recently; see @ref{Convenience
3269 Vars,, Convenience Variables}, for a discussion of what you can do with
3270 convenience variables.
3273 @item break @var{location}
3274 Set a breakpoint at the given @var{location}, which can specify a
3275 function name, a line number, or an address of an instruction.
3276 (@xref{Specify Location}, for a list of all the possible ways to
3277 specify a @var{location}.) The breakpoint will stop your program just
3278 before it executes any of the code in the specified @var{location}.
3280 When using source languages that permit overloading of symbols, such as
3281 C@t{++}, a function name may refer to more than one possible place to break.
3282 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3285 It is also possible to insert a breakpoint that will stop the program
3286 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3287 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3290 When called without any arguments, @code{break} sets a breakpoint at
3291 the next instruction to be executed in the selected stack frame
3292 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3293 innermost, this makes your program stop as soon as control
3294 returns to that frame. This is similar to the effect of a
3295 @code{finish} command in the frame inside the selected frame---except
3296 that @code{finish} does not leave an active breakpoint. If you use
3297 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3298 the next time it reaches the current location; this may be useful
3301 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3302 least one instruction has been executed. If it did not do this, you
3303 would be unable to proceed past a breakpoint without first disabling the
3304 breakpoint. This rule applies whether or not the breakpoint already
3305 existed when your program stopped.
3307 @item break @dots{} if @var{cond}
3308 Set a breakpoint with condition @var{cond}; evaluate the expression
3309 @var{cond} each time the breakpoint is reached, and stop only if the
3310 value is nonzero---that is, if @var{cond} evaluates as true.
3311 @samp{@dots{}} stands for one of the possible arguments described
3312 above (or no argument) specifying where to break. @xref{Conditions,
3313 ,Break Conditions}, for more information on breakpoint conditions.
3316 @item tbreak @var{args}
3317 Set a breakpoint enabled only for one stop. @var{args} are the
3318 same as for the @code{break} command, and the breakpoint is set in the same
3319 way, but the breakpoint is automatically deleted after the first time your
3320 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3323 @cindex hardware breakpoints
3324 @item hbreak @var{args}
3325 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3326 @code{break} command and the breakpoint is set in the same way, but the
3327 breakpoint requires hardware support and some target hardware may not
3328 have this support. The main purpose of this is EPROM/ROM code
3329 debugging, so you can set a breakpoint at an instruction without
3330 changing the instruction. This can be used with the new trap-generation
3331 provided by SPARClite DSU and most x86-based targets. These targets
3332 will generate traps when a program accesses some data or instruction
3333 address that is assigned to the debug registers. However the hardware
3334 breakpoint registers can take a limited number of breakpoints. For
3335 example, on the DSU, only two data breakpoints can be set at a time, and
3336 @value{GDBN} will reject this command if more than two are used. Delete
3337 or disable unused hardware breakpoints before setting new ones
3338 (@pxref{Disabling, ,Disabling Breakpoints}).
3339 @xref{Conditions, ,Break Conditions}.
3340 For remote targets, you can restrict the number of hardware
3341 breakpoints @value{GDBN} will use, see @ref{set remote
3342 hardware-breakpoint-limit}.
3345 @item thbreak @var{args}
3346 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3347 are the same as for the @code{hbreak} command and the breakpoint is set in
3348 the same way. However, like the @code{tbreak} command,
3349 the breakpoint is automatically deleted after the
3350 first time your program stops there. Also, like the @code{hbreak}
3351 command, the breakpoint requires hardware support and some target hardware
3352 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3353 See also @ref{Conditions, ,Break Conditions}.
3356 @cindex regular expression
3357 @cindex breakpoints in functions matching a regexp
3358 @cindex set breakpoints in many functions
3359 @item rbreak @var{regex}
3360 Set breakpoints on all functions matching the regular expression
3361 @var{regex}. This command sets an unconditional breakpoint on all
3362 matches, printing a list of all breakpoints it set. Once these
3363 breakpoints are set, they are treated just like the breakpoints set with
3364 the @code{break} command. You can delete them, disable them, or make
3365 them conditional the same way as any other breakpoint.
3367 The syntax of the regular expression is the standard one used with tools
3368 like @file{grep}. Note that this is different from the syntax used by
3369 shells, so for instance @code{foo*} matches all functions that include
3370 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3371 @code{.*} leading and trailing the regular expression you supply, so to
3372 match only functions that begin with @code{foo}, use @code{^foo}.
3374 @cindex non-member C@t{++} functions, set breakpoint in
3375 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3376 breakpoints on overloaded functions that are not members of any special
3379 @cindex set breakpoints on all functions
3380 The @code{rbreak} command can be used to set breakpoints in
3381 @strong{all} the functions in a program, like this:
3384 (@value{GDBP}) rbreak .
3387 @kindex info breakpoints
3388 @cindex @code{$_} and @code{info breakpoints}
3389 @item info breakpoints @r{[}@var{n}@r{]}
3390 @itemx info break @r{[}@var{n}@r{]}
3391 @itemx info watchpoints @r{[}@var{n}@r{]}
3392 Print a table of all breakpoints, watchpoints, and catchpoints set and
3393 not deleted. Optional argument @var{n} means print information only
3394 about the specified breakpoint (or watchpoint or catchpoint). For
3395 each breakpoint, following columns are printed:
3398 @item Breakpoint Numbers
3400 Breakpoint, watchpoint, or catchpoint.
3402 Whether the breakpoint is marked to be disabled or deleted when hit.
3403 @item Enabled or Disabled
3404 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3405 that are not enabled.
3407 Where the breakpoint is in your program, as a memory address. For a
3408 pending breakpoint whose address is not yet known, this field will
3409 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3410 library that has the symbol or line referred by breakpoint is loaded.
3411 See below for details. A breakpoint with several locations will
3412 have @samp{<MULTIPLE>} in this field---see below for details.
3414 Where the breakpoint is in the source for your program, as a file and
3415 line number. For a pending breakpoint, the original string passed to
3416 the breakpoint command will be listed as it cannot be resolved until
3417 the appropriate shared library is loaded in the future.
3421 If a breakpoint is conditional, @code{info break} shows the condition on
3422 the line following the affected breakpoint; breakpoint commands, if any,
3423 are listed after that. A pending breakpoint is allowed to have a condition
3424 specified for it. The condition is not parsed for validity until a shared
3425 library is loaded that allows the pending breakpoint to resolve to a
3429 @code{info break} with a breakpoint
3430 number @var{n} as argument lists only that breakpoint. The
3431 convenience variable @code{$_} and the default examining-address for
3432 the @code{x} command are set to the address of the last breakpoint
3433 listed (@pxref{Memory, ,Examining Memory}).
3436 @code{info break} displays a count of the number of times the breakpoint
3437 has been hit. This is especially useful in conjunction with the
3438 @code{ignore} command. You can ignore a large number of breakpoint
3439 hits, look at the breakpoint info to see how many times the breakpoint
3440 was hit, and then run again, ignoring one less than that number. This
3441 will get you quickly to the last hit of that breakpoint.
3444 @value{GDBN} allows you to set any number of breakpoints at the same place in
3445 your program. There is nothing silly or meaningless about this. When
3446 the breakpoints are conditional, this is even useful
3447 (@pxref{Conditions, ,Break Conditions}).
3449 @cindex multiple locations, breakpoints
3450 @cindex breakpoints, multiple locations
3451 It is possible that a breakpoint corresponds to several locations
3452 in your program. Examples of this situation are:
3456 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3457 instances of the function body, used in different cases.
3460 For a C@t{++} template function, a given line in the function can
3461 correspond to any number of instantiations.
3464 For an inlined function, a given source line can correspond to
3465 several places where that function is inlined.
3468 In all those cases, @value{GDBN} will insert a breakpoint at all
3469 the relevant locations@footnote{
3470 As of this writing, multiple-location breakpoints work only if there's
3471 line number information for all the locations. This means that they
3472 will generally not work in system libraries, unless you have debug
3473 info with line numbers for them.}.
3475 A breakpoint with multiple locations is displayed in the breakpoint
3476 table using several rows---one header row, followed by one row for
3477 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3478 address column. The rows for individual locations contain the actual
3479 addresses for locations, and show the functions to which those
3480 locations belong. The number column for a location is of the form
3481 @var{breakpoint-number}.@var{location-number}.
3486 Num Type Disp Enb Address What
3487 1 breakpoint keep y <MULTIPLE>
3489 breakpoint already hit 1 time
3490 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3491 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3494 Each location can be individually enabled or disabled by passing
3495 @var{breakpoint-number}.@var{location-number} as argument to the
3496 @code{enable} and @code{disable} commands. Note that you cannot
3497 delete the individual locations from the list, you can only delete the
3498 entire list of locations that belong to their parent breakpoint (with
3499 the @kbd{delete @var{num}} command, where @var{num} is the number of
3500 the parent breakpoint, 1 in the above example). Disabling or enabling
3501 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3502 that belong to that breakpoint.
3504 @cindex pending breakpoints
3505 It's quite common to have a breakpoint inside a shared library.
3506 Shared libraries can be loaded and unloaded explicitly,
3507 and possibly repeatedly, as the program is executed. To support
3508 this use case, @value{GDBN} updates breakpoint locations whenever
3509 any shared library is loaded or unloaded. Typically, you would
3510 set a breakpoint in a shared library at the beginning of your
3511 debugging session, when the library is not loaded, and when the
3512 symbols from the library are not available. When you try to set
3513 breakpoint, @value{GDBN} will ask you if you want to set
3514 a so called @dfn{pending breakpoint}---breakpoint whose address
3515 is not yet resolved.
3517 After the program is run, whenever a new shared library is loaded,
3518 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3519 shared library contains the symbol or line referred to by some
3520 pending breakpoint, that breakpoint is resolved and becomes an
3521 ordinary breakpoint. When a library is unloaded, all breakpoints
3522 that refer to its symbols or source lines become pending again.
3524 This logic works for breakpoints with multiple locations, too. For
3525 example, if you have a breakpoint in a C@t{++} template function, and
3526 a newly loaded shared library has an instantiation of that template,
3527 a new location is added to the list of locations for the breakpoint.
3529 Except for having unresolved address, pending breakpoints do not
3530 differ from regular breakpoints. You can set conditions or commands,
3531 enable and disable them and perform other breakpoint operations.
3533 @value{GDBN} provides some additional commands for controlling what
3534 happens when the @samp{break} command cannot resolve breakpoint
3535 address specification to an address:
3537 @kindex set breakpoint pending
3538 @kindex show breakpoint pending
3540 @item set breakpoint pending auto
3541 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3542 location, it queries you whether a pending breakpoint should be created.
3544 @item set breakpoint pending on
3545 This indicates that an unrecognized breakpoint location should automatically
3546 result in a pending breakpoint being created.
3548 @item set breakpoint pending off
3549 This indicates that pending breakpoints are not to be created. Any
3550 unrecognized breakpoint location results in an error. This setting does
3551 not affect any pending breakpoints previously created.
3553 @item show breakpoint pending
3554 Show the current behavior setting for creating pending breakpoints.
3557 The settings above only affect the @code{break} command and its
3558 variants. Once breakpoint is set, it will be automatically updated
3559 as shared libraries are loaded and unloaded.
3561 @cindex automatic hardware breakpoints
3562 For some targets, @value{GDBN} can automatically decide if hardware or
3563 software breakpoints should be used, depending on whether the
3564 breakpoint address is read-only or read-write. This applies to
3565 breakpoints set with the @code{break} command as well as to internal
3566 breakpoints set by commands like @code{next} and @code{finish}. For
3567 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3570 You can control this automatic behaviour with the following commands::
3572 @kindex set breakpoint auto-hw
3573 @kindex show breakpoint auto-hw
3575 @item set breakpoint auto-hw on
3576 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3577 will try to use the target memory map to decide if software or hardware
3578 breakpoint must be used.
3580 @item set breakpoint auto-hw off
3581 This indicates @value{GDBN} should not automatically select breakpoint
3582 type. If the target provides a memory map, @value{GDBN} will warn when
3583 trying to set software breakpoint at a read-only address.
3586 @value{GDBN} normally implements breakpoints by replacing the program code
3587 at the breakpoint address with a special instruction, which, when
3588 executed, given control to the debugger. By default, the program
3589 code is so modified only when the program is resumed. As soon as
3590 the program stops, @value{GDBN} restores the original instructions. This
3591 behaviour guards against leaving breakpoints inserted in the
3592 target should gdb abrubptly disconnect. However, with slow remote
3593 targets, inserting and removing breakpoint can reduce the performance.
3594 This behavior can be controlled with the following commands::
3596 @kindex set breakpoint always-inserted
3597 @kindex show breakpoint always-inserted
3599 @item set breakpoint always-inserted off
3600 All breakpoints, including newly added by the user, are inserted in
3601 the target only when the target is resumed. All breakpoints are
3602 removed from the target when it stops.
3604 @item set breakpoint always-inserted on
3605 Causes all breakpoints to be inserted in the target at all times. If
3606 the user adds a new breakpoint, or changes an existing breakpoint, the
3607 breakpoints in the target are updated immediately. A breakpoint is
3608 removed from the target only when breakpoint itself is removed.
3610 @cindex non-stop mode, and @code{breakpoint always-inserted}
3611 @item set breakpoint always-inserted auto
3612 This is the default mode. If @value{GDBN} is controlling the inferior
3613 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3614 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3615 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3616 @code{breakpoint always-inserted} mode is off.
3619 @cindex negative breakpoint numbers
3620 @cindex internal @value{GDBN} breakpoints
3621 @value{GDBN} itself sometimes sets breakpoints in your program for
3622 special purposes, such as proper handling of @code{longjmp} (in C
3623 programs). These internal breakpoints are assigned negative numbers,
3624 starting with @code{-1}; @samp{info breakpoints} does not display them.
3625 You can see these breakpoints with the @value{GDBN} maintenance command
3626 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3629 @node Set Watchpoints
3630 @subsection Setting Watchpoints
3632 @cindex setting watchpoints
3633 You can use a watchpoint to stop execution whenever the value of an
3634 expression changes, without having to predict a particular place where
3635 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3636 The expression may be as simple as the value of a single variable, or
3637 as complex as many variables combined by operators. Examples include:
3641 A reference to the value of a single variable.
3644 An address cast to an appropriate data type. For example,
3645 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3646 address (assuming an @code{int} occupies 4 bytes).
3649 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3650 expression can use any operators valid in the program's native
3651 language (@pxref{Languages}).
3654 You can set a watchpoint on an expression even if the expression can
3655 not be evaluated yet. For instance, you can set a watchpoint on
3656 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3657 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3658 the expression produces a valid value. If the expression becomes
3659 valid in some other way than changing a variable (e.g.@: if the memory
3660 pointed to by @samp{*global_ptr} becomes readable as the result of a
3661 @code{malloc} call), @value{GDBN} may not stop until the next time
3662 the expression changes.
3664 @cindex software watchpoints
3665 @cindex hardware watchpoints
3666 Depending on your system, watchpoints may be implemented in software or
3667 hardware. @value{GDBN} does software watchpointing by single-stepping your
3668 program and testing the variable's value each time, which is hundreds of
3669 times slower than normal execution. (But this may still be worth it, to
3670 catch errors where you have no clue what part of your program is the
3673 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3674 x86-based targets, @value{GDBN} includes support for hardware
3675 watchpoints, which do not slow down the running of your program.
3679 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3680 Set a watchpoint for an expression. @value{GDBN} will break when the
3681 expression @var{expr} is written into by the program and its value
3682 changes. The simplest (and the most popular) use of this command is
3683 to watch the value of a single variable:
3686 (@value{GDBP}) watch foo
3689 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3690 clause, @value{GDBN} breaks only when the thread identified by
3691 @var{threadnum} changes the value of @var{expr}. If any other threads
3692 change the value of @var{expr}, @value{GDBN} will not break. Note
3693 that watchpoints restricted to a single thread in this way only work
3694 with Hardware Watchpoints.
3697 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3698 Set a watchpoint that will break when the value of @var{expr} is read
3702 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint that will break when @var{expr} is either read from
3704 or written into by the program.
3706 @kindex info watchpoints @r{[}@var{n}@r{]}
3707 @item info watchpoints
3708 This command prints a list of watchpoints, breakpoints, and catchpoints;
3709 it is the same as @code{info break} (@pxref{Set Breaks}).
3712 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3713 watchpoints execute very quickly, and the debugger reports a change in
3714 value at the exact instruction where the change occurs. If @value{GDBN}
3715 cannot set a hardware watchpoint, it sets a software watchpoint, which
3716 executes more slowly and reports the change in value at the next
3717 @emph{statement}, not the instruction, after the change occurs.
3719 @cindex use only software watchpoints
3720 You can force @value{GDBN} to use only software watchpoints with the
3721 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3722 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3723 the underlying system supports them. (Note that hardware-assisted
3724 watchpoints that were set @emph{before} setting
3725 @code{can-use-hw-watchpoints} to zero will still use the hardware
3726 mechanism of watching expression values.)
3729 @item set can-use-hw-watchpoints
3730 @kindex set can-use-hw-watchpoints
3731 Set whether or not to use hardware watchpoints.
3733 @item show can-use-hw-watchpoints
3734 @kindex show can-use-hw-watchpoints
3735 Show the current mode of using hardware watchpoints.
3738 For remote targets, you can restrict the number of hardware
3739 watchpoints @value{GDBN} will use, see @ref{set remote
3740 hardware-breakpoint-limit}.
3742 When you issue the @code{watch} command, @value{GDBN} reports
3745 Hardware watchpoint @var{num}: @var{expr}
3749 if it was able to set a hardware watchpoint.
3751 Currently, the @code{awatch} and @code{rwatch} commands can only set
3752 hardware watchpoints, because accesses to data that don't change the
3753 value of the watched expression cannot be detected without examining
3754 every instruction as it is being executed, and @value{GDBN} does not do
3755 that currently. If @value{GDBN} finds that it is unable to set a
3756 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3757 will print a message like this:
3760 Expression cannot be implemented with read/access watchpoint.
3763 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3764 data type of the watched expression is wider than what a hardware
3765 watchpoint on the target machine can handle. For example, some systems
3766 can only watch regions that are up to 4 bytes wide; on such systems you
3767 cannot set hardware watchpoints for an expression that yields a
3768 double-precision floating-point number (which is typically 8 bytes
3769 wide). As a work-around, it might be possible to break the large region
3770 into a series of smaller ones and watch them with separate watchpoints.
3772 If you set too many hardware watchpoints, @value{GDBN} might be unable
3773 to insert all of them when you resume the execution of your program.
3774 Since the precise number of active watchpoints is unknown until such
3775 time as the program is about to be resumed, @value{GDBN} might not be
3776 able to warn you about this when you set the watchpoints, and the
3777 warning will be printed only when the program is resumed:
3780 Hardware watchpoint @var{num}: Could not insert watchpoint
3784 If this happens, delete or disable some of the watchpoints.
3786 Watching complex expressions that reference many variables can also
3787 exhaust the resources available for hardware-assisted watchpoints.
3788 That's because @value{GDBN} needs to watch every variable in the
3789 expression with separately allocated resources.
3791 If you call a function interactively using @code{print} or @code{call},
3792 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3793 kind of breakpoint or the call completes.
3795 @value{GDBN} automatically deletes watchpoints that watch local
3796 (automatic) variables, or expressions that involve such variables, when
3797 they go out of scope, that is, when the execution leaves the block in
3798 which these variables were defined. In particular, when the program
3799 being debugged terminates, @emph{all} local variables go out of scope,
3800 and so only watchpoints that watch global variables remain set. If you
3801 rerun the program, you will need to set all such watchpoints again. One
3802 way of doing that would be to set a code breakpoint at the entry to the
3803 @code{main} function and when it breaks, set all the watchpoints.
3805 @cindex watchpoints and threads
3806 @cindex threads and watchpoints
3807 In multi-threaded programs, watchpoints will detect changes to the
3808 watched expression from every thread.
3811 @emph{Warning:} In multi-threaded programs, software watchpoints
3812 have only limited usefulness. If @value{GDBN} creates a software
3813 watchpoint, it can only watch the value of an expression @emph{in a
3814 single thread}. If you are confident that the expression can only
3815 change due to the current thread's activity (and if you are also
3816 confident that no other thread can become current), then you can use
3817 software watchpoints as usual. However, @value{GDBN} may not notice
3818 when a non-current thread's activity changes the expression. (Hardware
3819 watchpoints, in contrast, watch an expression in all threads.)
3822 @xref{set remote hardware-watchpoint-limit}.
3824 @node Set Catchpoints
3825 @subsection Setting Catchpoints
3826 @cindex catchpoints, setting
3827 @cindex exception handlers
3828 @cindex event handling
3830 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3831 kinds of program events, such as C@t{++} exceptions or the loading of a
3832 shared library. Use the @code{catch} command to set a catchpoint.
3836 @item catch @var{event}
3837 Stop when @var{event} occurs. @var{event} can be any of the following:
3840 @cindex stop on C@t{++} exceptions
3841 The throwing of a C@t{++} exception.
3844 The catching of a C@t{++} exception.
3847 @cindex Ada exception catching
3848 @cindex catch Ada exceptions
3849 An Ada exception being raised. If an exception name is specified
3850 at the end of the command (eg @code{catch exception Program_Error}),
3851 the debugger will stop only when this specific exception is raised.
3852 Otherwise, the debugger stops execution when any Ada exception is raised.
3854 When inserting an exception catchpoint on a user-defined exception whose
3855 name is identical to one of the exceptions defined by the language, the
3856 fully qualified name must be used as the exception name. Otherwise,
3857 @value{GDBN} will assume that it should stop on the pre-defined exception
3858 rather than the user-defined one. For instance, assuming an exception
3859 called @code{Constraint_Error} is defined in package @code{Pck}, then
3860 the command to use to catch such exceptions is @kbd{catch exception
3861 Pck.Constraint_Error}.
3863 @item exception unhandled
3864 An exception that was raised but is not handled by the program.
3867 A failed Ada assertion.
3870 @cindex break on fork/exec
3871 A call to @code{exec}. This is currently only available for HP-UX
3875 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
3876 @cindex break on a system call.
3877 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3878 syscall is a mechanism for application programs to request a service
3879 from the operating system (OS) or one of the OS system services.
3880 @value{GDBN} can catch some or all of the syscalls issued by the
3881 debuggee, and show the related information for each syscall. If no
3882 argument is specified, calls to and returns from all system calls
3885 @var{name} can be any system call name that is valid for the
3886 underlying OS. Just what syscalls are valid depends on the OS. On
3887 GNU and Unix systems, you can find the full list of valid syscall
3888 names on @file{/usr/include/asm/unistd.h}.
3890 @c For MS-Windows, the syscall names and the corresponding numbers
3891 @c can be found, e.g., on this URL:
3892 @c http://www.metasploit.com/users/opcode/syscalls.html
3893 @c but we don't support Windows syscalls yet.
3895 Normally, @value{GDBN} knows in advance which syscalls are valid for
3896 each OS, so you can use the @value{GDBN} command-line completion
3897 facilities (@pxref{Completion,, command completion}) to list the
3900 You may also specify the system call numerically. A syscall's
3901 number is the value passed to the OS's syscall dispatcher to
3902 identify the requested service. When you specify the syscall by its
3903 name, @value{GDBN} uses its database of syscalls to convert the name
3904 into the corresponding numeric code, but using the number directly
3905 may be useful if @value{GDBN}'s database does not have the complete
3906 list of syscalls on your system (e.g., because @value{GDBN} lags
3907 behind the OS upgrades).
3909 The example below illustrates how this command works if you don't provide
3913 (@value{GDBP}) catch syscall
3914 Catchpoint 1 (syscall)
3916 Starting program: /tmp/catch-syscall
3918 Catchpoint 1 (call to syscall 'close'), \
3919 0xffffe424 in __kernel_vsyscall ()
3923 Catchpoint 1 (returned from syscall 'close'), \
3924 0xffffe424 in __kernel_vsyscall ()
3928 Here is an example of catching a system call by name:
3931 (@value{GDBP}) catch syscall chroot
3932 Catchpoint 1 (syscall 'chroot' [61])
3934 Starting program: /tmp/catch-syscall
3936 Catchpoint 1 (call to syscall 'chroot'), \
3937 0xffffe424 in __kernel_vsyscall ()
3941 Catchpoint 1 (returned from syscall 'chroot'), \
3942 0xffffe424 in __kernel_vsyscall ()
3946 An example of specifying a system call numerically. In the case
3947 below, the syscall number has a corresponding entry in the XML
3948 file, so @value{GDBN} finds its name and prints it:
3951 (@value{GDBP}) catch syscall 252
3952 Catchpoint 1 (syscall(s) 'exit_group')
3954 Starting program: /tmp/catch-syscall
3956 Catchpoint 1 (call to syscall 'exit_group'), \
3957 0xffffe424 in __kernel_vsyscall ()
3961 Program exited normally.
3965 However, there can be situations when there is no corresponding name
3966 in XML file for that syscall number. In this case, @value{GDBN} prints
3967 a warning message saying that it was not able to find the syscall name,
3968 but the catchpoint will be set anyway. See the example below:
3971 (@value{GDBP}) catch syscall 764
3972 warning: The number '764' does not represent a known syscall.
3973 Catchpoint 2 (syscall 764)
3977 If you configure @value{GDBN} using the @samp{--without-expat} option,
3978 it will not be able to display syscall names. Also, if your
3979 architecture does not have an XML file describing its system calls,
3980 you will not be able to see the syscall names. It is important to
3981 notice that these two features are used for accessing the syscall
3982 name database. In either case, you will see a warning like this:
3985 (@value{GDBP}) catch syscall
3986 warning: Could not open "syscalls/i386-linux.xml"
3987 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3988 GDB will not be able to display syscall names.
3989 Catchpoint 1 (syscall)
3993 Of course, the file name will change depending on your architecture and system.
3995 Still using the example above, you can also try to catch a syscall by its
3996 number. In this case, you would see something like:
3999 (@value{GDBP}) catch syscall 252
4000 Catchpoint 1 (syscall(s) 252)
4003 Again, in this case @value{GDBN} would not be able to display syscall's names.
4006 A call to @code{fork}. This is currently only available for HP-UX
4010 A call to @code{vfork}. This is currently only available for HP-UX
4015 @item tcatch @var{event}
4016 Set a catchpoint that is enabled only for one stop. The catchpoint is
4017 automatically deleted after the first time the event is caught.
4021 Use the @code{info break} command to list the current catchpoints.
4023 There are currently some limitations to C@t{++} exception handling
4024 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4028 If you call a function interactively, @value{GDBN} normally returns
4029 control to you when the function has finished executing. If the call
4030 raises an exception, however, the call may bypass the mechanism that
4031 returns control to you and cause your program either to abort or to
4032 simply continue running until it hits a breakpoint, catches a signal
4033 that @value{GDBN} is listening for, or exits. This is the case even if
4034 you set a catchpoint for the exception; catchpoints on exceptions are
4035 disabled within interactive calls.
4038 You cannot raise an exception interactively.
4041 You cannot install an exception handler interactively.
4044 @cindex raise exceptions
4045 Sometimes @code{catch} is not the best way to debug exception handling:
4046 if you need to know exactly where an exception is raised, it is better to
4047 stop @emph{before} the exception handler is called, since that way you
4048 can see the stack before any unwinding takes place. If you set a
4049 breakpoint in an exception handler instead, it may not be easy to find
4050 out where the exception was raised.
4052 To stop just before an exception handler is called, you need some
4053 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4054 raised by calling a library function named @code{__raise_exception}
4055 which has the following ANSI C interface:
4058 /* @var{addr} is where the exception identifier is stored.
4059 @var{id} is the exception identifier. */
4060 void __raise_exception (void **addr, void *id);
4064 To make the debugger catch all exceptions before any stack
4065 unwinding takes place, set a breakpoint on @code{__raise_exception}
4066 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4068 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4069 that depends on the value of @var{id}, you can stop your program when
4070 a specific exception is raised. You can use multiple conditional
4071 breakpoints to stop your program when any of a number of exceptions are
4076 @subsection Deleting Breakpoints
4078 @cindex clearing breakpoints, watchpoints, catchpoints
4079 @cindex deleting breakpoints, watchpoints, catchpoints
4080 It is often necessary to eliminate a breakpoint, watchpoint, or
4081 catchpoint once it has done its job and you no longer want your program
4082 to stop there. This is called @dfn{deleting} the breakpoint. A
4083 breakpoint that has been deleted no longer exists; it is forgotten.
4085 With the @code{clear} command you can delete breakpoints according to
4086 where they are in your program. With the @code{delete} command you can
4087 delete individual breakpoints, watchpoints, or catchpoints by specifying
4088 their breakpoint numbers.
4090 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4091 automatically ignores breakpoints on the first instruction to be executed
4092 when you continue execution without changing the execution address.
4097 Delete any breakpoints at the next instruction to be executed in the
4098 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4099 the innermost frame is selected, this is a good way to delete a
4100 breakpoint where your program just stopped.
4102 @item clear @var{location}
4103 Delete any breakpoints set at the specified @var{location}.
4104 @xref{Specify Location}, for the various forms of @var{location}; the
4105 most useful ones are listed below:
4108 @item clear @var{function}
4109 @itemx clear @var{filename}:@var{function}
4110 Delete any breakpoints set at entry to the named @var{function}.
4112 @item clear @var{linenum}
4113 @itemx clear @var{filename}:@var{linenum}
4114 Delete any breakpoints set at or within the code of the specified
4115 @var{linenum} of the specified @var{filename}.
4118 @cindex delete breakpoints
4120 @kindex d @r{(@code{delete})}
4121 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4122 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4123 ranges specified as arguments. If no argument is specified, delete all
4124 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4125 confirm off}). You can abbreviate this command as @code{d}.
4129 @subsection Disabling Breakpoints
4131 @cindex enable/disable a breakpoint
4132 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4133 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4134 it had been deleted, but remembers the information on the breakpoint so
4135 that you can @dfn{enable} it again later.
4137 You disable and enable breakpoints, watchpoints, and catchpoints with
4138 the @code{enable} and @code{disable} commands, optionally specifying one
4139 or more breakpoint numbers as arguments. Use @code{info break} or
4140 @code{info watch} to print a list of breakpoints, watchpoints, and
4141 catchpoints if you do not know which numbers to use.
4143 Disabling and enabling a breakpoint that has multiple locations
4144 affects all of its locations.
4146 A breakpoint, watchpoint, or catchpoint can have any of four different
4147 states of enablement:
4151 Enabled. The breakpoint stops your program. A breakpoint set
4152 with the @code{break} command starts out in this state.
4154 Disabled. The breakpoint has no effect on your program.
4156 Enabled once. The breakpoint stops your program, but then becomes
4159 Enabled for deletion. The breakpoint stops your program, but
4160 immediately after it does so it is deleted permanently. A breakpoint
4161 set with the @code{tbreak} command starts out in this state.
4164 You can use the following commands to enable or disable breakpoints,
4165 watchpoints, and catchpoints:
4169 @kindex dis @r{(@code{disable})}
4170 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4171 Disable the specified breakpoints---or all breakpoints, if none are
4172 listed. A disabled breakpoint has no effect but is not forgotten. All
4173 options such as ignore-counts, conditions and commands are remembered in
4174 case the breakpoint is enabled again later. You may abbreviate
4175 @code{disable} as @code{dis}.
4178 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4179 Enable the specified breakpoints (or all defined breakpoints). They
4180 become effective once again in stopping your program.
4182 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4183 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4184 of these breakpoints immediately after stopping your program.
4186 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4187 Enable the specified breakpoints to work once, then die. @value{GDBN}
4188 deletes any of these breakpoints as soon as your program stops there.
4189 Breakpoints set by the @code{tbreak} command start out in this state.
4192 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4193 @c confusing: tbreak is also initially enabled.
4194 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4195 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4196 subsequently, they become disabled or enabled only when you use one of
4197 the commands above. (The command @code{until} can set and delete a
4198 breakpoint of its own, but it does not change the state of your other
4199 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4203 @subsection Break Conditions
4204 @cindex conditional breakpoints
4205 @cindex breakpoint conditions
4207 @c FIXME what is scope of break condition expr? Context where wanted?
4208 @c in particular for a watchpoint?
4209 The simplest sort of breakpoint breaks every time your program reaches a
4210 specified place. You can also specify a @dfn{condition} for a
4211 breakpoint. A condition is just a Boolean expression in your
4212 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4213 a condition evaluates the expression each time your program reaches it,
4214 and your program stops only if the condition is @emph{true}.
4216 This is the converse of using assertions for program validation; in that
4217 situation, you want to stop when the assertion is violated---that is,
4218 when the condition is false. In C, if you want to test an assertion expressed
4219 by the condition @var{assert}, you should set the condition
4220 @samp{! @var{assert}} on the appropriate breakpoint.
4222 Conditions are also accepted for watchpoints; you may not need them,
4223 since a watchpoint is inspecting the value of an expression anyhow---but
4224 it might be simpler, say, to just set a watchpoint on a variable name,
4225 and specify a condition that tests whether the new value is an interesting
4228 Break conditions can have side effects, and may even call functions in
4229 your program. This can be useful, for example, to activate functions
4230 that log program progress, or to use your own print functions to
4231 format special data structures. The effects are completely predictable
4232 unless there is another enabled breakpoint at the same address. (In
4233 that case, @value{GDBN} might see the other breakpoint first and stop your
4234 program without checking the condition of this one.) Note that
4235 breakpoint commands are usually more convenient and flexible than break
4237 purpose of performing side effects when a breakpoint is reached
4238 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4240 Break conditions can be specified when a breakpoint is set, by using
4241 @samp{if} in the arguments to the @code{break} command. @xref{Set
4242 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4243 with the @code{condition} command.
4245 You can also use the @code{if} keyword with the @code{watch} command.
4246 The @code{catch} command does not recognize the @code{if} keyword;
4247 @code{condition} is the only way to impose a further condition on a
4252 @item condition @var{bnum} @var{expression}
4253 Specify @var{expression} as the break condition for breakpoint,
4254 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4255 breakpoint @var{bnum} stops your program only if the value of
4256 @var{expression} is true (nonzero, in C). When you use
4257 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4258 syntactic correctness, and to determine whether symbols in it have
4259 referents in the context of your breakpoint. If @var{expression} uses
4260 symbols not referenced in the context of the breakpoint, @value{GDBN}
4261 prints an error message:
4264 No symbol "foo" in current context.
4269 not actually evaluate @var{expression} at the time the @code{condition}
4270 command (or a command that sets a breakpoint with a condition, like
4271 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4273 @item condition @var{bnum}
4274 Remove the condition from breakpoint number @var{bnum}. It becomes
4275 an ordinary unconditional breakpoint.
4278 @cindex ignore count (of breakpoint)
4279 A special case of a breakpoint condition is to stop only when the
4280 breakpoint has been reached a certain number of times. This is so
4281 useful that there is a special way to do it, using the @dfn{ignore
4282 count} of the breakpoint. Every breakpoint has an ignore count, which
4283 is an integer. Most of the time, the ignore count is zero, and
4284 therefore has no effect. But if your program reaches a breakpoint whose
4285 ignore count is positive, then instead of stopping, it just decrements
4286 the ignore count by one and continues. As a result, if the ignore count
4287 value is @var{n}, the breakpoint does not stop the next @var{n} times
4288 your program reaches it.
4292 @item ignore @var{bnum} @var{count}
4293 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4294 The next @var{count} times the breakpoint is reached, your program's
4295 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4298 To make the breakpoint stop the next time it is reached, specify
4301 When you use @code{continue} to resume execution of your program from a
4302 breakpoint, you can specify an ignore count directly as an argument to
4303 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4304 Stepping,,Continuing and Stepping}.
4306 If a breakpoint has a positive ignore count and a condition, the
4307 condition is not checked. Once the ignore count reaches zero,
4308 @value{GDBN} resumes checking the condition.
4310 You could achieve the effect of the ignore count with a condition such
4311 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4312 is decremented each time. @xref{Convenience Vars, ,Convenience
4316 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4319 @node Break Commands
4320 @subsection Breakpoint Command Lists
4322 @cindex breakpoint commands
4323 You can give any breakpoint (or watchpoint or catchpoint) a series of
4324 commands to execute when your program stops due to that breakpoint. For
4325 example, you might want to print the values of certain expressions, or
4326 enable other breakpoints.
4330 @kindex end@r{ (breakpoint commands)}
4331 @item commands @r{[}@var{bnum}@r{]}
4332 @itemx @dots{} @var{command-list} @dots{}
4334 Specify a list of commands for breakpoint number @var{bnum}. The commands
4335 themselves appear on the following lines. Type a line containing just
4336 @code{end} to terminate the commands.
4338 To remove all commands from a breakpoint, type @code{commands} and
4339 follow it immediately with @code{end}; that is, give no commands.
4341 With no @var{bnum} argument, @code{commands} refers to the last
4342 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4343 recently encountered).
4346 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4347 disabled within a @var{command-list}.
4349 You can use breakpoint commands to start your program up again. Simply
4350 use the @code{continue} command, or @code{step}, or any other command
4351 that resumes execution.
4353 Any other commands in the command list, after a command that resumes
4354 execution, are ignored. This is because any time you resume execution
4355 (even with a simple @code{next} or @code{step}), you may encounter
4356 another breakpoint---which could have its own command list, leading to
4357 ambiguities about which list to execute.
4360 If the first command you specify in a command list is @code{silent}, the
4361 usual message about stopping at a breakpoint is not printed. This may
4362 be desirable for breakpoints that are to print a specific message and
4363 then continue. If none of the remaining commands print anything, you
4364 see no sign that the breakpoint was reached. @code{silent} is
4365 meaningful only at the beginning of a breakpoint command list.
4367 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4368 print precisely controlled output, and are often useful in silent
4369 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4371 For example, here is how you could use breakpoint commands to print the
4372 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4378 printf "x is %d\n",x
4383 One application for breakpoint commands is to compensate for one bug so
4384 you can test for another. Put a breakpoint just after the erroneous line
4385 of code, give it a condition to detect the case in which something
4386 erroneous has been done, and give it commands to assign correct values
4387 to any variables that need them. End with the @code{continue} command
4388 so that your program does not stop, and start with the @code{silent}
4389 command so that no output is produced. Here is an example:
4400 @c @ifclear BARETARGET
4401 @node Error in Breakpoints
4402 @subsection ``Cannot insert breakpoints''
4404 If you request too many active hardware-assisted breakpoints and
4405 watchpoints, you will see this error message:
4407 @c FIXME: the precise wording of this message may change; the relevant
4408 @c source change is not committed yet (Sep 3, 1999).
4410 Stopped; cannot insert breakpoints.
4411 You may have requested too many hardware breakpoints and watchpoints.
4415 This message is printed when you attempt to resume the program, since
4416 only then @value{GDBN} knows exactly how many hardware breakpoints and
4417 watchpoints it needs to insert.
4419 When this message is printed, you need to disable or remove some of the
4420 hardware-assisted breakpoints and watchpoints, and then continue.
4422 @node Breakpoint-related Warnings
4423 @subsection ``Breakpoint address adjusted...''
4424 @cindex breakpoint address adjusted
4426 Some processor architectures place constraints on the addresses at
4427 which breakpoints may be placed. For architectures thus constrained,
4428 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4429 with the constraints dictated by the architecture.
4431 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4432 a VLIW architecture in which a number of RISC-like instructions may be
4433 bundled together for parallel execution. The FR-V architecture
4434 constrains the location of a breakpoint instruction within such a
4435 bundle to the instruction with the lowest address. @value{GDBN}
4436 honors this constraint by adjusting a breakpoint's address to the
4437 first in the bundle.
4439 It is not uncommon for optimized code to have bundles which contain
4440 instructions from different source statements, thus it may happen that
4441 a breakpoint's address will be adjusted from one source statement to
4442 another. Since this adjustment may significantly alter @value{GDBN}'s
4443 breakpoint related behavior from what the user expects, a warning is
4444 printed when the breakpoint is first set and also when the breakpoint
4447 A warning like the one below is printed when setting a breakpoint
4448 that's been subject to address adjustment:
4451 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4454 Such warnings are printed both for user settable and @value{GDBN}'s
4455 internal breakpoints. If you see one of these warnings, you should
4456 verify that a breakpoint set at the adjusted address will have the
4457 desired affect. If not, the breakpoint in question may be removed and
4458 other breakpoints may be set which will have the desired behavior.
4459 E.g., it may be sufficient to place the breakpoint at a later
4460 instruction. A conditional breakpoint may also be useful in some
4461 cases to prevent the breakpoint from triggering too often.
4463 @value{GDBN} will also issue a warning when stopping at one of these
4464 adjusted breakpoints:
4467 warning: Breakpoint 1 address previously adjusted from 0x00010414
4471 When this warning is encountered, it may be too late to take remedial
4472 action except in cases where the breakpoint is hit earlier or more
4473 frequently than expected.
4475 @node Continuing and Stepping
4476 @section Continuing and Stepping
4480 @cindex resuming execution
4481 @dfn{Continuing} means resuming program execution until your program
4482 completes normally. In contrast, @dfn{stepping} means executing just
4483 one more ``step'' of your program, where ``step'' may mean either one
4484 line of source code, or one machine instruction (depending on what
4485 particular command you use). Either when continuing or when stepping,
4486 your program may stop even sooner, due to a breakpoint or a signal. (If
4487 it stops due to a signal, you may want to use @code{handle}, or use
4488 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4492 @kindex c @r{(@code{continue})}
4493 @kindex fg @r{(resume foreground execution)}
4494 @item continue @r{[}@var{ignore-count}@r{]}
4495 @itemx c @r{[}@var{ignore-count}@r{]}
4496 @itemx fg @r{[}@var{ignore-count}@r{]}
4497 Resume program execution, at the address where your program last stopped;
4498 any breakpoints set at that address are bypassed. The optional argument
4499 @var{ignore-count} allows you to specify a further number of times to
4500 ignore a breakpoint at this location; its effect is like that of
4501 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4503 The argument @var{ignore-count} is meaningful only when your program
4504 stopped due to a breakpoint. At other times, the argument to
4505 @code{continue} is ignored.
4507 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4508 debugged program is deemed to be the foreground program) are provided
4509 purely for convenience, and have exactly the same behavior as
4513 To resume execution at a different place, you can use @code{return}
4514 (@pxref{Returning, ,Returning from a Function}) to go back to the
4515 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4516 Different Address}) to go to an arbitrary location in your program.
4518 A typical technique for using stepping is to set a breakpoint
4519 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4520 beginning of the function or the section of your program where a problem
4521 is believed to lie, run your program until it stops at that breakpoint,
4522 and then step through the suspect area, examining the variables that are
4523 interesting, until you see the problem happen.
4527 @kindex s @r{(@code{step})}
4529 Continue running your program until control reaches a different source
4530 line, then stop it and return control to @value{GDBN}. This command is
4531 abbreviated @code{s}.
4534 @c "without debugging information" is imprecise; actually "without line
4535 @c numbers in the debugging information". (gcc -g1 has debugging info but
4536 @c not line numbers). But it seems complex to try to make that
4537 @c distinction here.
4538 @emph{Warning:} If you use the @code{step} command while control is
4539 within a function that was compiled without debugging information,
4540 execution proceeds until control reaches a function that does have
4541 debugging information. Likewise, it will not step into a function which
4542 is compiled without debugging information. To step through functions
4543 without debugging information, use the @code{stepi} command, described
4547 The @code{step} command only stops at the first instruction of a source
4548 line. This prevents the multiple stops that could otherwise occur in
4549 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4550 to stop if a function that has debugging information is called within
4551 the line. In other words, @code{step} @emph{steps inside} any functions
4552 called within the line.
4554 Also, the @code{step} command only enters a function if there is line
4555 number information for the function. Otherwise it acts like the
4556 @code{next} command. This avoids problems when using @code{cc -gl}
4557 on MIPS machines. Previously, @code{step} entered subroutines if there
4558 was any debugging information about the routine.
4560 @item step @var{count}
4561 Continue running as in @code{step}, but do so @var{count} times. If a
4562 breakpoint is reached, or a signal not related to stepping occurs before
4563 @var{count} steps, stepping stops right away.
4566 @kindex n @r{(@code{next})}
4567 @item next @r{[}@var{count}@r{]}
4568 Continue to the next source line in the current (innermost) stack frame.
4569 This is similar to @code{step}, but function calls that appear within
4570 the line of code are executed without stopping. Execution stops when
4571 control reaches a different line of code at the original stack level
4572 that was executing when you gave the @code{next} command. This command
4573 is abbreviated @code{n}.
4575 An argument @var{count} is a repeat count, as for @code{step}.
4578 @c FIX ME!! Do we delete this, or is there a way it fits in with
4579 @c the following paragraph? --- Vctoria
4581 @c @code{next} within a function that lacks debugging information acts like
4582 @c @code{step}, but any function calls appearing within the code of the
4583 @c function are executed without stopping.
4585 The @code{next} command only stops at the first instruction of a
4586 source line. This prevents multiple stops that could otherwise occur in
4587 @code{switch} statements, @code{for} loops, etc.
4589 @kindex set step-mode
4591 @cindex functions without line info, and stepping
4592 @cindex stepping into functions with no line info
4593 @itemx set step-mode on
4594 The @code{set step-mode on} command causes the @code{step} command to
4595 stop at the first instruction of a function which contains no debug line
4596 information rather than stepping over it.
4598 This is useful in cases where you may be interested in inspecting the
4599 machine instructions of a function which has no symbolic info and do not
4600 want @value{GDBN} to automatically skip over this function.
4602 @item set step-mode off
4603 Causes the @code{step} command to step over any functions which contains no
4604 debug information. This is the default.
4606 @item show step-mode
4607 Show whether @value{GDBN} will stop in or step over functions without
4608 source line debug information.
4611 @kindex fin @r{(@code{finish})}
4613 Continue running until just after function in the selected stack frame
4614 returns. Print the returned value (if any). This command can be
4615 abbreviated as @code{fin}.
4617 Contrast this with the @code{return} command (@pxref{Returning,
4618 ,Returning from a Function}).
4621 @kindex u @r{(@code{until})}
4622 @cindex run until specified location
4625 Continue running until a source line past the current line, in the
4626 current stack frame, is reached. This command is used to avoid single
4627 stepping through a loop more than once. It is like the @code{next}
4628 command, except that when @code{until} encounters a jump, it
4629 automatically continues execution until the program counter is greater
4630 than the address of the jump.
4632 This means that when you reach the end of a loop after single stepping
4633 though it, @code{until} makes your program continue execution until it
4634 exits the loop. In contrast, a @code{next} command at the end of a loop
4635 simply steps back to the beginning of the loop, which forces you to step
4636 through the next iteration.
4638 @code{until} always stops your program if it attempts to exit the current
4641 @code{until} may produce somewhat counterintuitive results if the order
4642 of machine code does not match the order of the source lines. For
4643 example, in the following excerpt from a debugging session, the @code{f}
4644 (@code{frame}) command shows that execution is stopped at line
4645 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4649 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4651 (@value{GDBP}) until
4652 195 for ( ; argc > 0; NEXTARG) @{
4655 This happened because, for execution efficiency, the compiler had
4656 generated code for the loop closure test at the end, rather than the
4657 start, of the loop---even though the test in a C @code{for}-loop is
4658 written before the body of the loop. The @code{until} command appeared
4659 to step back to the beginning of the loop when it advanced to this
4660 expression; however, it has not really gone to an earlier
4661 statement---not in terms of the actual machine code.
4663 @code{until} with no argument works by means of single
4664 instruction stepping, and hence is slower than @code{until} with an
4667 @item until @var{location}
4668 @itemx u @var{location}
4669 Continue running your program until either the specified location is
4670 reached, or the current stack frame returns. @var{location} is any of
4671 the forms described in @ref{Specify Location}.
4672 This form of the command uses temporary breakpoints, and
4673 hence is quicker than @code{until} without an argument. The specified
4674 location is actually reached only if it is in the current frame. This
4675 implies that @code{until} can be used to skip over recursive function
4676 invocations. For instance in the code below, if the current location is
4677 line @code{96}, issuing @code{until 99} will execute the program up to
4678 line @code{99} in the same invocation of factorial, i.e., after the inner
4679 invocations have returned.
4682 94 int factorial (int value)
4684 96 if (value > 1) @{
4685 97 value *= factorial (value - 1);
4692 @kindex advance @var{location}
4693 @itemx advance @var{location}
4694 Continue running the program up to the given @var{location}. An argument is
4695 required, which should be of one of the forms described in
4696 @ref{Specify Location}.
4697 Execution will also stop upon exit from the current stack
4698 frame. This command is similar to @code{until}, but @code{advance} will
4699 not skip over recursive function calls, and the target location doesn't
4700 have to be in the same frame as the current one.
4704 @kindex si @r{(@code{stepi})}
4706 @itemx stepi @var{arg}
4708 Execute one machine instruction, then stop and return to the debugger.
4710 It is often useful to do @samp{display/i $pc} when stepping by machine
4711 instructions. This makes @value{GDBN} automatically display the next
4712 instruction to be executed, each time your program stops. @xref{Auto
4713 Display,, Automatic Display}.
4715 An argument is a repeat count, as in @code{step}.
4719 @kindex ni @r{(@code{nexti})}
4721 @itemx nexti @var{arg}
4723 Execute one machine instruction, but if it is a function call,
4724 proceed until the function returns.
4726 An argument is a repeat count, as in @code{next}.
4733 A signal is an asynchronous event that can happen in a program. The
4734 operating system defines the possible kinds of signals, and gives each
4735 kind a name and a number. For example, in Unix @code{SIGINT} is the
4736 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4737 @code{SIGSEGV} is the signal a program gets from referencing a place in
4738 memory far away from all the areas in use; @code{SIGALRM} occurs when
4739 the alarm clock timer goes off (which happens only if your program has
4740 requested an alarm).
4742 @cindex fatal signals
4743 Some signals, including @code{SIGALRM}, are a normal part of the
4744 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4745 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4746 program has not specified in advance some other way to handle the signal.
4747 @code{SIGINT} does not indicate an error in your program, but it is normally
4748 fatal so it can carry out the purpose of the interrupt: to kill the program.
4750 @value{GDBN} has the ability to detect any occurrence of a signal in your
4751 program. You can tell @value{GDBN} in advance what to do for each kind of
4754 @cindex handling signals
4755 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4756 @code{SIGALRM} be silently passed to your program
4757 (so as not to interfere with their role in the program's functioning)
4758 but to stop your program immediately whenever an error signal happens.
4759 You can change these settings with the @code{handle} command.
4762 @kindex info signals
4766 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4767 handle each one. You can use this to see the signal numbers of all
4768 the defined types of signals.
4770 @item info signals @var{sig}
4771 Similar, but print information only about the specified signal number.
4773 @code{info handle} is an alias for @code{info signals}.
4776 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4777 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4778 can be the number of a signal or its name (with or without the
4779 @samp{SIG} at the beginning); a list of signal numbers of the form
4780 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4781 known signals. Optional arguments @var{keywords}, described below,
4782 say what change to make.
4786 The keywords allowed by the @code{handle} command can be abbreviated.
4787 Their full names are:
4791 @value{GDBN} should not stop your program when this signal happens. It may
4792 still print a message telling you that the signal has come in.
4795 @value{GDBN} should stop your program when this signal happens. This implies
4796 the @code{print} keyword as well.
4799 @value{GDBN} should print a message when this signal happens.
4802 @value{GDBN} should not mention the occurrence of the signal at all. This
4803 implies the @code{nostop} keyword as well.
4807 @value{GDBN} should allow your program to see this signal; your program
4808 can handle the signal, or else it may terminate if the signal is fatal
4809 and not handled. @code{pass} and @code{noignore} are synonyms.
4813 @value{GDBN} should not allow your program to see this signal.
4814 @code{nopass} and @code{ignore} are synonyms.
4818 When a signal stops your program, the signal is not visible to the
4820 continue. Your program sees the signal then, if @code{pass} is in
4821 effect for the signal in question @emph{at that time}. In other words,
4822 after @value{GDBN} reports a signal, you can use the @code{handle}
4823 command with @code{pass} or @code{nopass} to control whether your
4824 program sees that signal when you continue.
4826 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4827 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4828 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4831 You can also use the @code{signal} command to prevent your program from
4832 seeing a signal, or cause it to see a signal it normally would not see,
4833 or to give it any signal at any time. For example, if your program stopped
4834 due to some sort of memory reference error, you might store correct
4835 values into the erroneous variables and continue, hoping to see more
4836 execution; but your program would probably terminate immediately as
4837 a result of the fatal signal once it saw the signal. To prevent this,
4838 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4841 @cindex extra signal information
4842 @anchor{extra signal information}
4844 On some targets, @value{GDBN} can inspect extra signal information
4845 associated with the intercepted signal, before it is actually
4846 delivered to the program being debugged. This information is exported
4847 by the convenience variable @code{$_siginfo}, and consists of data
4848 that is passed by the kernel to the signal handler at the time of the
4849 receipt of a signal. The data type of the information itself is
4850 target dependent. You can see the data type using the @code{ptype
4851 $_siginfo} command. On Unix systems, it typically corresponds to the
4852 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4855 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4856 referenced address that raised a segmentation fault.
4860 (@value{GDBP}) continue
4861 Program received signal SIGSEGV, Segmentation fault.
4862 0x0000000000400766 in main ()
4864 (@value{GDBP}) ptype $_siginfo
4871 struct @{...@} _kill;
4872 struct @{...@} _timer;
4874 struct @{...@} _sigchld;
4875 struct @{...@} _sigfault;
4876 struct @{...@} _sigpoll;
4879 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4883 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4884 $1 = (void *) 0x7ffff7ff7000
4888 Depending on target support, @code{$_siginfo} may also be writable.
4891 @section Stopping and Starting Multi-thread Programs
4893 @cindex stopped threads
4894 @cindex threads, stopped
4896 @cindex continuing threads
4897 @cindex threads, continuing
4899 @value{GDBN} supports debugging programs with multiple threads
4900 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4901 are two modes of controlling execution of your program within the
4902 debugger. In the default mode, referred to as @dfn{all-stop mode},
4903 when any thread in your program stops (for example, at a breakpoint
4904 or while being stepped), all other threads in the program are also stopped by
4905 @value{GDBN}. On some targets, @value{GDBN} also supports
4906 @dfn{non-stop mode}, in which other threads can continue to run freely while
4907 you examine the stopped thread in the debugger.
4910 * All-Stop Mode:: All threads stop when GDB takes control
4911 * Non-Stop Mode:: Other threads continue to execute
4912 * Background Execution:: Running your program asynchronously
4913 * Thread-Specific Breakpoints:: Controlling breakpoints
4914 * Interrupted System Calls:: GDB may interfere with system calls
4918 @subsection All-Stop Mode
4920 @cindex all-stop mode
4922 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4923 @emph{all} threads of execution stop, not just the current thread. This
4924 allows you to examine the overall state of the program, including
4925 switching between threads, without worrying that things may change
4928 Conversely, whenever you restart the program, @emph{all} threads start
4929 executing. @emph{This is true even when single-stepping} with commands
4930 like @code{step} or @code{next}.
4932 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4933 Since thread scheduling is up to your debugging target's operating
4934 system (not controlled by @value{GDBN}), other threads may
4935 execute more than one statement while the current thread completes a
4936 single step. Moreover, in general other threads stop in the middle of a
4937 statement, rather than at a clean statement boundary, when the program
4940 You might even find your program stopped in another thread after
4941 continuing or even single-stepping. This happens whenever some other
4942 thread runs into a breakpoint, a signal, or an exception before the
4943 first thread completes whatever you requested.
4945 @cindex automatic thread selection
4946 @cindex switching threads automatically
4947 @cindex threads, automatic switching
4948 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4949 signal, it automatically selects the thread where that breakpoint or
4950 signal happened. @value{GDBN} alerts you to the context switch with a
4951 message such as @samp{[Switching to Thread @var{n}]} to identify the
4954 On some OSes, you can modify @value{GDBN}'s default behavior by
4955 locking the OS scheduler to allow only a single thread to run.
4958 @item set scheduler-locking @var{mode}
4959 @cindex scheduler locking mode
4960 @cindex lock scheduler
4961 Set the scheduler locking mode. If it is @code{off}, then there is no
4962 locking and any thread may run at any time. If @code{on}, then only the
4963 current thread may run when the inferior is resumed. The @code{step}
4964 mode optimizes for single-stepping; it prevents other threads
4965 from preempting the current thread while you are stepping, so that
4966 the focus of debugging does not change unexpectedly.
4967 Other threads only rarely (or never) get a chance to run
4968 when you step. They are more likely to run when you @samp{next} over a
4969 function call, and they are completely free to run when you use commands
4970 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4971 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4972 the current thread away from the thread that you are debugging.
4974 @item show scheduler-locking
4975 Display the current scheduler locking mode.
4978 @cindex resume threads of multiple processes simultaneously
4979 By default, when you issue one of the execution commands such as
4980 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4981 threads of the current inferior to run. For example, if @value{GDBN}
4982 is attached to two inferiors, each with two threads, the
4983 @code{continue} command resumes only the two threads of the current
4984 inferior. This is useful, for example, when you debug a program that
4985 forks and you want to hold the parent stopped (so that, for instance,
4986 it doesn't run to exit), while you debug the child. In other
4987 situations, you may not be interested in inspecting the current state
4988 of any of the processes @value{GDBN} is attached to, and you may want
4989 to resume them all until some breakpoint is hit. In the latter case,
4990 you can instruct @value{GDBN} to allow all threads of all the
4991 inferiors to run with the @w{@code{set schedule-multiple}} command.
4994 @kindex set schedule-multiple
4995 @item set schedule-multiple
4996 Set the mode for allowing threads of multiple processes to be resumed
4997 when an execution command is issued. When @code{on}, all threads of
4998 all processes are allowed to run. When @code{off}, only the threads
4999 of the current process are resumed. The default is @code{off}. The
5000 @code{scheduler-locking} mode takes precedence when set to @code{on},
5001 or while you are stepping and set to @code{step}.
5003 @item show schedule-multiple
5004 Display the current mode for resuming the execution of threads of
5009 @subsection Non-Stop Mode
5011 @cindex non-stop mode
5013 @c This section is really only a place-holder, and needs to be expanded
5014 @c with more details.
5016 For some multi-threaded targets, @value{GDBN} supports an optional
5017 mode of operation in which you can examine stopped program threads in
5018 the debugger while other threads continue to execute freely. This
5019 minimizes intrusion when debugging live systems, such as programs
5020 where some threads have real-time constraints or must continue to
5021 respond to external events. This is referred to as @dfn{non-stop} mode.
5023 In non-stop mode, when a thread stops to report a debugging event,
5024 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5025 threads as well, in contrast to the all-stop mode behavior. Additionally,
5026 execution commands such as @code{continue} and @code{step} apply by default
5027 only to the current thread in non-stop mode, rather than all threads as
5028 in all-stop mode. This allows you to control threads explicitly in
5029 ways that are not possible in all-stop mode --- for example, stepping
5030 one thread while allowing others to run freely, stepping
5031 one thread while holding all others stopped, or stepping several threads
5032 independently and simultaneously.
5034 To enter non-stop mode, use this sequence of commands before you run
5035 or attach to your program:
5038 # Enable the async interface.
5041 # If using the CLI, pagination breaks non-stop.
5044 # Finally, turn it on!
5048 You can use these commands to manipulate the non-stop mode setting:
5051 @kindex set non-stop
5052 @item set non-stop on
5053 Enable selection of non-stop mode.
5054 @item set non-stop off
5055 Disable selection of non-stop mode.
5056 @kindex show non-stop
5058 Show the current non-stop enablement setting.
5061 Note these commands only reflect whether non-stop mode is enabled,
5062 not whether the currently-executing program is being run in non-stop mode.
5063 In particular, the @code{set non-stop} preference is only consulted when
5064 @value{GDBN} starts or connects to the target program, and it is generally
5065 not possible to switch modes once debugging has started. Furthermore,
5066 since not all targets support non-stop mode, even when you have enabled
5067 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5070 In non-stop mode, all execution commands apply only to the current thread
5071 by default. That is, @code{continue} only continues one thread.
5072 To continue all threads, issue @code{continue -a} or @code{c -a}.
5074 You can use @value{GDBN}'s background execution commands
5075 (@pxref{Background Execution}) to run some threads in the background
5076 while you continue to examine or step others from @value{GDBN}.
5077 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5078 always executed asynchronously in non-stop mode.
5080 Suspending execution is done with the @code{interrupt} command when
5081 running in the background, or @kbd{Ctrl-c} during foreground execution.
5082 In all-stop mode, this stops the whole process;
5083 but in non-stop mode the interrupt applies only to the current thread.
5084 To stop the whole program, use @code{interrupt -a}.
5086 Other execution commands do not currently support the @code{-a} option.
5088 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5089 that thread current, as it does in all-stop mode. This is because the
5090 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5091 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5092 changed to a different thread just as you entered a command to operate on the
5093 previously current thread.
5095 @node Background Execution
5096 @subsection Background Execution
5098 @cindex foreground execution
5099 @cindex background execution
5100 @cindex asynchronous execution
5101 @cindex execution, foreground, background and asynchronous
5103 @value{GDBN}'s execution commands have two variants: the normal
5104 foreground (synchronous) behavior, and a background
5105 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5106 the program to report that some thread has stopped before prompting for
5107 another command. In background execution, @value{GDBN} immediately gives
5108 a command prompt so that you can issue other commands while your program runs.
5110 You need to explicitly enable asynchronous mode before you can use
5111 background execution commands. You can use these commands to
5112 manipulate the asynchronous mode setting:
5115 @kindex set target-async
5116 @item set target-async on
5117 Enable asynchronous mode.
5118 @item set target-async off
5119 Disable asynchronous mode.
5120 @kindex show target-async
5121 @item show target-async
5122 Show the current target-async setting.
5125 If the target doesn't support async mode, @value{GDBN} issues an error
5126 message if you attempt to use the background execution commands.
5128 To specify background execution, add a @code{&} to the command. For example,
5129 the background form of the @code{continue} command is @code{continue&}, or
5130 just @code{c&}. The execution commands that accept background execution
5136 @xref{Starting, , Starting your Program}.
5140 @xref{Attach, , Debugging an Already-running Process}.
5144 @xref{Continuing and Stepping, step}.
5148 @xref{Continuing and Stepping, stepi}.
5152 @xref{Continuing and Stepping, next}.
5156 @xref{Continuing and Stepping, nexti}.
5160 @xref{Continuing and Stepping, continue}.
5164 @xref{Continuing and Stepping, finish}.
5168 @xref{Continuing and Stepping, until}.
5172 Background execution is especially useful in conjunction with non-stop
5173 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5174 However, you can also use these commands in the normal all-stop mode with
5175 the restriction that you cannot issue another execution command until the
5176 previous one finishes. Examples of commands that are valid in all-stop
5177 mode while the program is running include @code{help} and @code{info break}.
5179 You can interrupt your program while it is running in the background by
5180 using the @code{interrupt} command.
5187 Suspend execution of the running program. In all-stop mode,
5188 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5189 only the current thread. To stop the whole program in non-stop mode,
5190 use @code{interrupt -a}.
5193 @node Thread-Specific Breakpoints
5194 @subsection Thread-Specific Breakpoints
5196 When your program has multiple threads (@pxref{Threads,, Debugging
5197 Programs with Multiple Threads}), you can choose whether to set
5198 breakpoints on all threads, or on a particular thread.
5201 @cindex breakpoints and threads
5202 @cindex thread breakpoints
5203 @kindex break @dots{} thread @var{threadno}
5204 @item break @var{linespec} thread @var{threadno}
5205 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5206 @var{linespec} specifies source lines; there are several ways of
5207 writing them (@pxref{Specify Location}), but the effect is always to
5208 specify some source line.
5210 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5211 to specify that you only want @value{GDBN} to stop the program when a
5212 particular thread reaches this breakpoint. @var{threadno} is one of the
5213 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5214 column of the @samp{info threads} display.
5216 If you do not specify @samp{thread @var{threadno}} when you set a
5217 breakpoint, the breakpoint applies to @emph{all} threads of your
5220 You can use the @code{thread} qualifier on conditional breakpoints as
5221 well; in this case, place @samp{thread @var{threadno}} before or
5222 after the breakpoint condition, like this:
5225 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5230 @node Interrupted System Calls
5231 @subsection Interrupted System Calls
5233 @cindex thread breakpoints and system calls
5234 @cindex system calls and thread breakpoints
5235 @cindex premature return from system calls
5236 There is an unfortunate side effect when using @value{GDBN} to debug
5237 multi-threaded programs. If one thread stops for a
5238 breakpoint, or for some other reason, and another thread is blocked in a
5239 system call, then the system call may return prematurely. This is a
5240 consequence of the interaction between multiple threads and the signals
5241 that @value{GDBN} uses to implement breakpoints and other events that
5244 To handle this problem, your program should check the return value of
5245 each system call and react appropriately. This is good programming
5248 For example, do not write code like this:
5254 The call to @code{sleep} will return early if a different thread stops
5255 at a breakpoint or for some other reason.
5257 Instead, write this:
5262 unslept = sleep (unslept);
5265 A system call is allowed to return early, so the system is still
5266 conforming to its specification. But @value{GDBN} does cause your
5267 multi-threaded program to behave differently than it would without
5270 Also, @value{GDBN} uses internal breakpoints in the thread library to
5271 monitor certain events such as thread creation and thread destruction.
5272 When such an event happens, a system call in another thread may return
5273 prematurely, even though your program does not appear to stop.
5276 @node Reverse Execution
5277 @chapter Running programs backward
5278 @cindex reverse execution
5279 @cindex running programs backward
5281 When you are debugging a program, it is not unusual to realize that
5282 you have gone too far, and some event of interest has already happened.
5283 If the target environment supports it, @value{GDBN} can allow you to
5284 ``rewind'' the program by running it backward.
5286 A target environment that supports reverse execution should be able
5287 to ``undo'' the changes in machine state that have taken place as the
5288 program was executing normally. Variables, registers etc.@: should
5289 revert to their previous values. Obviously this requires a great
5290 deal of sophistication on the part of the target environment; not
5291 all target environments can support reverse execution.
5293 When a program is executed in reverse, the instructions that
5294 have most recently been executed are ``un-executed'', in reverse
5295 order. The program counter runs backward, following the previous
5296 thread of execution in reverse. As each instruction is ``un-executed'',
5297 the values of memory and/or registers that were changed by that
5298 instruction are reverted to their previous states. After executing
5299 a piece of source code in reverse, all side effects of that code
5300 should be ``undone'', and all variables should be returned to their
5301 prior values@footnote{
5302 Note that some side effects are easier to undo than others. For instance,
5303 memory and registers are relatively easy, but device I/O is hard. Some
5304 targets may be able undo things like device I/O, and some may not.
5306 The contract between @value{GDBN} and the reverse executing target
5307 requires only that the target do something reasonable when
5308 @value{GDBN} tells it to execute backwards, and then report the
5309 results back to @value{GDBN}. Whatever the target reports back to
5310 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5311 assumes that the memory and registers that the target reports are in a
5312 consistant state, but @value{GDBN} accepts whatever it is given.
5315 If you are debugging in a target environment that supports
5316 reverse execution, @value{GDBN} provides the following commands.
5319 @kindex reverse-continue
5320 @kindex rc @r{(@code{reverse-continue})}
5321 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5322 @itemx rc @r{[}@var{ignore-count}@r{]}
5323 Beginning at the point where your program last stopped, start executing
5324 in reverse. Reverse execution will stop for breakpoints and synchronous
5325 exceptions (signals), just like normal execution. Behavior of
5326 asynchronous signals depends on the target environment.
5328 @kindex reverse-step
5329 @kindex rs @r{(@code{step})}
5330 @item reverse-step @r{[}@var{count}@r{]}
5331 Run the program backward until control reaches the start of a
5332 different source line; then stop it, and return control to @value{GDBN}.
5334 Like the @code{step} command, @code{reverse-step} will only stop
5335 at the beginning of a source line. It ``un-executes'' the previously
5336 executed source line. If the previous source line included calls to
5337 debuggable functions, @code{reverse-step} will step (backward) into
5338 the called function, stopping at the beginning of the @emph{last}
5339 statement in the called function (typically a return statement).
5341 Also, as with the @code{step} command, if non-debuggable functions are
5342 called, @code{reverse-step} will run thru them backward without stopping.
5344 @kindex reverse-stepi
5345 @kindex rsi @r{(@code{reverse-stepi})}
5346 @item reverse-stepi @r{[}@var{count}@r{]}
5347 Reverse-execute one machine instruction. Note that the instruction
5348 to be reverse-executed is @emph{not} the one pointed to by the program
5349 counter, but the instruction executed prior to that one. For instance,
5350 if the last instruction was a jump, @code{reverse-stepi} will take you
5351 back from the destination of the jump to the jump instruction itself.
5353 @kindex reverse-next
5354 @kindex rn @r{(@code{reverse-next})}
5355 @item reverse-next @r{[}@var{count}@r{]}
5356 Run backward to the beginning of the previous line executed in
5357 the current (innermost) stack frame. If the line contains function
5358 calls, they will be ``un-executed'' without stopping. Starting from
5359 the first line of a function, @code{reverse-next} will take you back
5360 to the caller of that function, @emph{before} the function was called,
5361 just as the normal @code{next} command would take you from the last
5362 line of a function back to its return to its caller
5363 @footnote{Unless the code is too heavily optimized.}.
5365 @kindex reverse-nexti
5366 @kindex rni @r{(@code{reverse-nexti})}
5367 @item reverse-nexti @r{[}@var{count}@r{]}
5368 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5369 in reverse, except that called functions are ``un-executed'' atomically.
5370 That is, if the previously executed instruction was a return from
5371 another function, @code{reverse-nexti} will continue to execute
5372 in reverse until the call to that function (from the current stack
5375 @kindex reverse-finish
5376 @item reverse-finish
5377 Just as the @code{finish} command takes you to the point where the
5378 current function returns, @code{reverse-finish} takes you to the point
5379 where it was called. Instead of ending up at the end of the current
5380 function invocation, you end up at the beginning.
5382 @kindex set exec-direction
5383 @item set exec-direction
5384 Set the direction of target execution.
5385 @itemx set exec-direction reverse
5386 @cindex execute forward or backward in time
5387 @value{GDBN} will perform all execution commands in reverse, until the
5388 exec-direction mode is changed to ``forward''. Affected commands include
5389 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5390 command cannot be used in reverse mode.
5391 @item set exec-direction forward
5392 @value{GDBN} will perform all execution commands in the normal fashion.
5393 This is the default.
5397 @node Process Record and Replay
5398 @chapter Recording Inferior's Execution and Replaying It
5399 @cindex process record and replay
5400 @cindex recording inferior's execution and replaying it
5402 On some platforms, @value{GDBN} provides a special @dfn{process record
5403 and replay} target that can record a log of the process execution, and
5404 replay it later with both forward and reverse execution commands.
5407 When this target is in use, if the execution log includes the record
5408 for the next instruction, @value{GDBN} will debug in @dfn{replay
5409 mode}. In the replay mode, the inferior does not really execute code
5410 instructions. Instead, all the events that normally happen during
5411 code execution are taken from the execution log. While code is not
5412 really executed in replay mode, the values of registers (including the
5413 program counter register) and the memory of the inferior are still
5414 changed as they normally would. Their contents are taken from the
5418 If the record for the next instruction is not in the execution log,
5419 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5420 inferior executes normally, and @value{GDBN} records the execution log
5423 The process record and replay target supports reverse execution
5424 (@pxref{Reverse Execution}), even if the platform on which the
5425 inferior runs does not. However, the reverse execution is limited in
5426 this case by the range of the instructions recorded in the execution
5427 log. In other words, reverse execution on platforms that don't
5428 support it directly can only be done in the replay mode.
5430 When debugging in the reverse direction, @value{GDBN} will work in
5431 replay mode as long as the execution log includes the record for the
5432 previous instruction; otherwise, it will work in record mode, if the
5433 platform supports reverse execution, or stop if not.
5435 For architecture environments that support process record and replay,
5436 @value{GDBN} provides the following commands:
5439 @kindex target record
5443 This command starts the process record and replay target. The process
5444 record and replay target can only debug a process that is already
5445 running. Therefore, you need first to start the process with the
5446 @kbd{run} or @kbd{start} commands, and then start the recording with
5447 the @kbd{target record} command.
5449 Both @code{record} and @code{rec} are aliases of @code{target record}.
5451 @cindex displaced stepping, and process record and replay
5452 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5453 will be automatically disabled when process record and replay target
5454 is started. That's because the process record and replay target
5455 doesn't support displaced stepping.
5457 @cindex non-stop mode, and process record and replay
5458 @cindex asynchronous execution, and process record and replay
5459 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5460 the asynchronous execution mode (@pxref{Background Execution}), the
5461 process record and replay target cannot be started because it doesn't
5462 support these two modes.
5467 Stop the process record and replay target. When process record and
5468 replay target stops, the entire execution log will be deleted and the
5469 inferior will either be terminated, or will remain in its final state.
5471 When you stop the process record and replay target in record mode (at
5472 the end of the execution log), the inferior will be stopped at the
5473 next instruction that would have been recorded. In other words, if
5474 you record for a while and then stop recording, the inferior process
5475 will be left in the same state as if the recording never happened.
5477 On the other hand, if the process record and replay target is stopped
5478 while in replay mode (that is, not at the end of the execution log,
5479 but at some earlier point), the inferior process will become ``live''
5480 at that earlier state, and it will then be possible to continue the
5481 usual ``live'' debugging of the process from that state.
5483 When the inferior process exits, or @value{GDBN} detaches from it,
5484 process record and replay target will automatically stop itself.
5486 @kindex set record insn-number-max
5487 @item set record insn-number-max @var{limit}
5488 Set the limit of instructions to be recorded. Default value is 200000.
5490 If @var{limit} is a positive number, then @value{GDBN} will start
5491 deleting instructions from the log once the number of the record
5492 instructions becomes greater than @var{limit}. For every new recorded
5493 instruction, @value{GDBN} will delete the earliest recorded
5494 instruction to keep the number of recorded instructions at the limit.
5495 (Since deleting recorded instructions loses information, @value{GDBN}
5496 lets you control what happens when the limit is reached, by means of
5497 the @code{stop-at-limit} option, described below.)
5499 If @var{limit} is zero, @value{GDBN} will never delete recorded
5500 instructions from the execution log. The number of recorded
5501 instructions is unlimited in this case.
5503 @kindex show record insn-number-max
5504 @item show record insn-number-max
5505 Show the limit of instructions to be recorded.
5507 @kindex set record stop-at-limit
5508 @item set record stop-at-limit
5509 Control the behavior when the number of recorded instructions reaches
5510 the limit. If ON (the default), @value{GDBN} will stop when the limit
5511 is reached for the first time and ask you whether you want to stop the
5512 inferior or continue running it and recording the execution log. If
5513 you decide to continue recording, each new recorded instruction will
5514 cause the oldest one to be deleted.
5516 If this option is OFF, @value{GDBN} will automatically delete the
5517 oldest record to make room for each new one, without asking.
5519 @kindex show record stop-at-limit
5520 @item show record stop-at-limit
5521 Show the current setting of @code{stop-at-limit}.
5525 Show various statistics about the state of process record and its
5526 in-memory execution log buffer, including:
5530 Whether in record mode or replay mode.
5532 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5534 Highest recorded instruction number.
5536 Current instruction about to be replayed (if in replay mode).
5538 Number of instructions contained in the execution log.
5540 Maximum number of instructions that may be contained in the execution log.
5543 @kindex record delete
5546 When record target runs in replay mode (``in the past''), delete the
5547 subsequent execution log and begin to record a new execution log starting
5548 from the current address. This means you will abandon the previously
5549 recorded ``future'' and begin recording a new ``future''.
5554 @chapter Examining the Stack
5556 When your program has stopped, the first thing you need to know is where it
5557 stopped and how it got there.
5560 Each time your program performs a function call, information about the call
5562 That information includes the location of the call in your program,
5563 the arguments of the call,
5564 and the local variables of the function being called.
5565 The information is saved in a block of data called a @dfn{stack frame}.
5566 The stack frames are allocated in a region of memory called the @dfn{call
5569 When your program stops, the @value{GDBN} commands for examining the
5570 stack allow you to see all of this information.
5572 @cindex selected frame
5573 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5574 @value{GDBN} commands refer implicitly to the selected frame. In
5575 particular, whenever you ask @value{GDBN} for the value of a variable in
5576 your program, the value is found in the selected frame. There are
5577 special @value{GDBN} commands to select whichever frame you are
5578 interested in. @xref{Selection, ,Selecting a Frame}.
5580 When your program stops, @value{GDBN} automatically selects the
5581 currently executing frame and describes it briefly, similar to the
5582 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5585 * Frames:: Stack frames
5586 * Backtrace:: Backtraces
5587 * Selection:: Selecting a frame
5588 * Frame Info:: Information on a frame
5593 @section Stack Frames
5595 @cindex frame, definition
5597 The call stack is divided up into contiguous pieces called @dfn{stack
5598 frames}, or @dfn{frames} for short; each frame is the data associated
5599 with one call to one function. The frame contains the arguments given
5600 to the function, the function's local variables, and the address at
5601 which the function is executing.
5603 @cindex initial frame
5604 @cindex outermost frame
5605 @cindex innermost frame
5606 When your program is started, the stack has only one frame, that of the
5607 function @code{main}. This is called the @dfn{initial} frame or the
5608 @dfn{outermost} frame. Each time a function is called, a new frame is
5609 made. Each time a function returns, the frame for that function invocation
5610 is eliminated. If a function is recursive, there can be many frames for
5611 the same function. The frame for the function in which execution is
5612 actually occurring is called the @dfn{innermost} frame. This is the most
5613 recently created of all the stack frames that still exist.
5615 @cindex frame pointer
5616 Inside your program, stack frames are identified by their addresses. A
5617 stack frame consists of many bytes, each of which has its own address; each
5618 kind of computer has a convention for choosing one byte whose
5619 address serves as the address of the frame. Usually this address is kept
5620 in a register called the @dfn{frame pointer register}
5621 (@pxref{Registers, $fp}) while execution is going on in that frame.
5623 @cindex frame number
5624 @value{GDBN} assigns numbers to all existing stack frames, starting with
5625 zero for the innermost frame, one for the frame that called it,
5626 and so on upward. These numbers do not really exist in your program;
5627 they are assigned by @value{GDBN} to give you a way of designating stack
5628 frames in @value{GDBN} commands.
5630 @c The -fomit-frame-pointer below perennially causes hbox overflow
5631 @c underflow problems.
5632 @cindex frameless execution
5633 Some compilers provide a way to compile functions so that they operate
5634 without stack frames. (For example, the @value{NGCC} option
5636 @samp{-fomit-frame-pointer}
5638 generates functions without a frame.)
5639 This is occasionally done with heavily used library functions to save
5640 the frame setup time. @value{GDBN} has limited facilities for dealing
5641 with these function invocations. If the innermost function invocation
5642 has no stack frame, @value{GDBN} nevertheless regards it as though
5643 it had a separate frame, which is numbered zero as usual, allowing
5644 correct tracing of the function call chain. However, @value{GDBN} has
5645 no provision for frameless functions elsewhere in the stack.
5648 @kindex frame@r{, command}
5649 @cindex current stack frame
5650 @item frame @var{args}
5651 The @code{frame} command allows you to move from one stack frame to another,
5652 and to print the stack frame you select. @var{args} may be either the
5653 address of the frame or the stack frame number. Without an argument,
5654 @code{frame} prints the current stack frame.
5656 @kindex select-frame
5657 @cindex selecting frame silently
5659 The @code{select-frame} command allows you to move from one stack frame
5660 to another without printing the frame. This is the silent version of
5668 @cindex call stack traces
5669 A backtrace is a summary of how your program got where it is. It shows one
5670 line per frame, for many frames, starting with the currently executing
5671 frame (frame zero), followed by its caller (frame one), and on up the
5676 @kindex bt @r{(@code{backtrace})}
5679 Print a backtrace of the entire stack: one line per frame for all
5680 frames in the stack.
5682 You can stop the backtrace at any time by typing the system interrupt
5683 character, normally @kbd{Ctrl-c}.
5685 @item backtrace @var{n}
5687 Similar, but print only the innermost @var{n} frames.
5689 @item backtrace -@var{n}
5691 Similar, but print only the outermost @var{n} frames.
5693 @item backtrace full
5695 @itemx bt full @var{n}
5696 @itemx bt full -@var{n}
5697 Print the values of the local variables also. @var{n} specifies the
5698 number of frames to print, as described above.
5703 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5704 are additional aliases for @code{backtrace}.
5706 @cindex multiple threads, backtrace
5707 In a multi-threaded program, @value{GDBN} by default shows the
5708 backtrace only for the current thread. To display the backtrace for
5709 several or all of the threads, use the command @code{thread apply}
5710 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5711 apply all backtrace}, @value{GDBN} will display the backtrace for all
5712 the threads; this is handy when you debug a core dump of a
5713 multi-threaded program.
5715 Each line in the backtrace shows the frame number and the function name.
5716 The program counter value is also shown---unless you use @code{set
5717 print address off}. The backtrace also shows the source file name and
5718 line number, as well as the arguments to the function. The program
5719 counter value is omitted if it is at the beginning of the code for that
5722 Here is an example of a backtrace. It was made with the command
5723 @samp{bt 3}, so it shows the innermost three frames.
5727 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5729 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5730 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5732 (More stack frames follow...)
5737 The display for frame zero does not begin with a program counter
5738 value, indicating that your program has stopped at the beginning of the
5739 code for line @code{993} of @code{builtin.c}.
5742 The value of parameter @code{data} in frame 1 has been replaced by
5743 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5744 only if it is a scalar (integer, pointer, enumeration, etc). See command
5745 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5746 on how to configure the way function parameter values are printed.
5748 @cindex value optimized out, in backtrace
5749 @cindex function call arguments, optimized out
5750 If your program was compiled with optimizations, some compilers will
5751 optimize away arguments passed to functions if those arguments are
5752 never used after the call. Such optimizations generate code that
5753 passes arguments through registers, but doesn't store those arguments
5754 in the stack frame. @value{GDBN} has no way of displaying such
5755 arguments in stack frames other than the innermost one. Here's what
5756 such a backtrace might look like:
5760 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5762 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5763 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5765 (More stack frames follow...)
5770 The values of arguments that were not saved in their stack frames are
5771 shown as @samp{<value optimized out>}.
5773 If you need to display the values of such optimized-out arguments,
5774 either deduce that from other variables whose values depend on the one
5775 you are interested in, or recompile without optimizations.
5777 @cindex backtrace beyond @code{main} function
5778 @cindex program entry point
5779 @cindex startup code, and backtrace
5780 Most programs have a standard user entry point---a place where system
5781 libraries and startup code transition into user code. For C this is
5782 @code{main}@footnote{
5783 Note that embedded programs (the so-called ``free-standing''
5784 environment) are not required to have a @code{main} function as the
5785 entry point. They could even have multiple entry points.}.
5786 When @value{GDBN} finds the entry function in a backtrace
5787 it will terminate the backtrace, to avoid tracing into highly
5788 system-specific (and generally uninteresting) code.
5790 If you need to examine the startup code, or limit the number of levels
5791 in a backtrace, you can change this behavior:
5794 @item set backtrace past-main
5795 @itemx set backtrace past-main on
5796 @kindex set backtrace
5797 Backtraces will continue past the user entry point.
5799 @item set backtrace past-main off
5800 Backtraces will stop when they encounter the user entry point. This is the
5803 @item show backtrace past-main
5804 @kindex show backtrace
5805 Display the current user entry point backtrace policy.
5807 @item set backtrace past-entry
5808 @itemx set backtrace past-entry on
5809 Backtraces will continue past the internal entry point of an application.
5810 This entry point is encoded by the linker when the application is built,
5811 and is likely before the user entry point @code{main} (or equivalent) is called.
5813 @item set backtrace past-entry off
5814 Backtraces will stop when they encounter the internal entry point of an
5815 application. This is the default.
5817 @item show backtrace past-entry
5818 Display the current internal entry point backtrace policy.
5820 @item set backtrace limit @var{n}
5821 @itemx set backtrace limit 0
5822 @cindex backtrace limit
5823 Limit the backtrace to @var{n} levels. A value of zero means
5826 @item show backtrace limit
5827 Display the current limit on backtrace levels.
5831 @section Selecting a Frame
5833 Most commands for examining the stack and other data in your program work on
5834 whichever stack frame is selected at the moment. Here are the commands for
5835 selecting a stack frame; all of them finish by printing a brief description
5836 of the stack frame just selected.
5839 @kindex frame@r{, selecting}
5840 @kindex f @r{(@code{frame})}
5843 Select frame number @var{n}. Recall that frame zero is the innermost
5844 (currently executing) frame, frame one is the frame that called the
5845 innermost one, and so on. The highest-numbered frame is the one for
5848 @item frame @var{addr}
5850 Select the frame at address @var{addr}. This is useful mainly if the
5851 chaining of stack frames has been damaged by a bug, making it
5852 impossible for @value{GDBN} to assign numbers properly to all frames. In
5853 addition, this can be useful when your program has multiple stacks and
5854 switches between them.
5856 On the SPARC architecture, @code{frame} needs two addresses to
5857 select an arbitrary frame: a frame pointer and a stack pointer.
5859 On the MIPS and Alpha architecture, it needs two addresses: a stack
5860 pointer and a program counter.
5862 On the 29k architecture, it needs three addresses: a register stack
5863 pointer, a program counter, and a memory stack pointer.
5867 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5868 advances toward the outermost frame, to higher frame numbers, to frames
5869 that have existed longer. @var{n} defaults to one.
5872 @kindex do @r{(@code{down})}
5874 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5875 advances toward the innermost frame, to lower frame numbers, to frames
5876 that were created more recently. @var{n} defaults to one. You may
5877 abbreviate @code{down} as @code{do}.
5880 All of these commands end by printing two lines of output describing the
5881 frame. The first line shows the frame number, the function name, the
5882 arguments, and the source file and line number of execution in that
5883 frame. The second line shows the text of that source line.
5891 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5893 10 read_input_file (argv[i]);
5897 After such a printout, the @code{list} command with no arguments
5898 prints ten lines centered on the point of execution in the frame.
5899 You can also edit the program at the point of execution with your favorite
5900 editing program by typing @code{edit}.
5901 @xref{List, ,Printing Source Lines},
5905 @kindex down-silently
5907 @item up-silently @var{n}
5908 @itemx down-silently @var{n}
5909 These two commands are variants of @code{up} and @code{down},
5910 respectively; they differ in that they do their work silently, without
5911 causing display of the new frame. They are intended primarily for use
5912 in @value{GDBN} command scripts, where the output might be unnecessary and
5917 @section Information About a Frame
5919 There are several other commands to print information about the selected
5925 When used without any argument, this command does not change which
5926 frame is selected, but prints a brief description of the currently
5927 selected stack frame. It can be abbreviated @code{f}. With an
5928 argument, this command is used to select a stack frame.
5929 @xref{Selection, ,Selecting a Frame}.
5932 @kindex info f @r{(@code{info frame})}
5935 This command prints a verbose description of the selected stack frame,
5940 the address of the frame
5942 the address of the next frame down (called by this frame)
5944 the address of the next frame up (caller of this frame)
5946 the language in which the source code corresponding to this frame is written
5948 the address of the frame's arguments
5950 the address of the frame's local variables
5952 the program counter saved in it (the address of execution in the caller frame)
5954 which registers were saved in the frame
5957 @noindent The verbose description is useful when
5958 something has gone wrong that has made the stack format fail to fit
5959 the usual conventions.
5961 @item info frame @var{addr}
5962 @itemx info f @var{addr}
5963 Print a verbose description of the frame at address @var{addr}, without
5964 selecting that frame. The selected frame remains unchanged by this
5965 command. This requires the same kind of address (more than one for some
5966 architectures) that you specify in the @code{frame} command.
5967 @xref{Selection, ,Selecting a Frame}.
5971 Print the arguments of the selected frame, each on a separate line.
5975 Print the local variables of the selected frame, each on a separate
5976 line. These are all variables (declared either static or automatic)
5977 accessible at the point of execution of the selected frame.
5980 @cindex catch exceptions, list active handlers
5981 @cindex exception handlers, how to list
5983 Print a list of all the exception handlers that are active in the
5984 current stack frame at the current point of execution. To see other
5985 exception handlers, visit the associated frame (using the @code{up},
5986 @code{down}, or @code{frame} commands); then type @code{info catch}.
5987 @xref{Set Catchpoints, , Setting Catchpoints}.
5993 @chapter Examining Source Files
5995 @value{GDBN} can print parts of your program's source, since the debugging
5996 information recorded in the program tells @value{GDBN} what source files were
5997 used to build it. When your program stops, @value{GDBN} spontaneously prints
5998 the line where it stopped. Likewise, when you select a stack frame
5999 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6000 execution in that frame has stopped. You can print other portions of
6001 source files by explicit command.
6003 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6004 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6005 @value{GDBN} under @sc{gnu} Emacs}.
6008 * List:: Printing source lines
6009 * Specify Location:: How to specify code locations
6010 * Edit:: Editing source files
6011 * Search:: Searching source files
6012 * Source Path:: Specifying source directories
6013 * Machine Code:: Source and machine code
6017 @section Printing Source Lines
6020 @kindex l @r{(@code{list})}
6021 To print lines from a source file, use the @code{list} command
6022 (abbreviated @code{l}). By default, ten lines are printed.
6023 There are several ways to specify what part of the file you want to
6024 print; see @ref{Specify Location}, for the full list.
6026 Here are the forms of the @code{list} command most commonly used:
6029 @item list @var{linenum}
6030 Print lines centered around line number @var{linenum} in the
6031 current source file.
6033 @item list @var{function}
6034 Print lines centered around the beginning of function
6038 Print more lines. If the last lines printed were printed with a
6039 @code{list} command, this prints lines following the last lines
6040 printed; however, if the last line printed was a solitary line printed
6041 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6042 Stack}), this prints lines centered around that line.
6045 Print lines just before the lines last printed.
6048 @cindex @code{list}, how many lines to display
6049 By default, @value{GDBN} prints ten source lines with any of these forms of
6050 the @code{list} command. You can change this using @code{set listsize}:
6053 @kindex set listsize
6054 @item set listsize @var{count}
6055 Make the @code{list} command display @var{count} source lines (unless
6056 the @code{list} argument explicitly specifies some other number).
6058 @kindex show listsize
6060 Display the number of lines that @code{list} prints.
6063 Repeating a @code{list} command with @key{RET} discards the argument,
6064 so it is equivalent to typing just @code{list}. This is more useful
6065 than listing the same lines again. An exception is made for an
6066 argument of @samp{-}; that argument is preserved in repetition so that
6067 each repetition moves up in the source file.
6069 In general, the @code{list} command expects you to supply zero, one or two
6070 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6071 of writing them (@pxref{Specify Location}), but the effect is always
6072 to specify some source line.
6074 Here is a complete description of the possible arguments for @code{list}:
6077 @item list @var{linespec}
6078 Print lines centered around the line specified by @var{linespec}.
6080 @item list @var{first},@var{last}
6081 Print lines from @var{first} to @var{last}. Both arguments are
6082 linespecs. When a @code{list} command has two linespecs, and the
6083 source file of the second linespec is omitted, this refers to
6084 the same source file as the first linespec.
6086 @item list ,@var{last}
6087 Print lines ending with @var{last}.
6089 @item list @var{first},
6090 Print lines starting with @var{first}.
6093 Print lines just after the lines last printed.
6096 Print lines just before the lines last printed.
6099 As described in the preceding table.
6102 @node Specify Location
6103 @section Specifying a Location
6104 @cindex specifying location
6107 Several @value{GDBN} commands accept arguments that specify a location
6108 of your program's code. Since @value{GDBN} is a source-level
6109 debugger, a location usually specifies some line in the source code;
6110 for that reason, locations are also known as @dfn{linespecs}.
6112 Here are all the different ways of specifying a code location that
6113 @value{GDBN} understands:
6117 Specifies the line number @var{linenum} of the current source file.
6120 @itemx +@var{offset}
6121 Specifies the line @var{offset} lines before or after the @dfn{current
6122 line}. For the @code{list} command, the current line is the last one
6123 printed; for the breakpoint commands, this is the line at which
6124 execution stopped in the currently selected @dfn{stack frame}
6125 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6126 used as the second of the two linespecs in a @code{list} command,
6127 this specifies the line @var{offset} lines up or down from the first
6130 @item @var{filename}:@var{linenum}
6131 Specifies the line @var{linenum} in the source file @var{filename}.
6133 @item @var{function}
6134 Specifies the line that begins the body of the function @var{function}.
6135 For example, in C, this is the line with the open brace.
6137 @item @var{filename}:@var{function}
6138 Specifies the line that begins the body of the function @var{function}
6139 in the file @var{filename}. You only need the file name with a
6140 function name to avoid ambiguity when there are identically named
6141 functions in different source files.
6143 @item *@var{address}
6144 Specifies the program address @var{address}. For line-oriented
6145 commands, such as @code{list} and @code{edit}, this specifies a source
6146 line that contains @var{address}. For @code{break} and other
6147 breakpoint oriented commands, this can be used to set breakpoints in
6148 parts of your program which do not have debugging information or
6151 Here @var{address} may be any expression valid in the current working
6152 language (@pxref{Languages, working language}) that specifies a code
6153 address. In addition, as a convenience, @value{GDBN} extends the
6154 semantics of expressions used in locations to cover the situations
6155 that frequently happen during debugging. Here are the various forms
6159 @item @var{expression}
6160 Any expression valid in the current working language.
6162 @item @var{funcaddr}
6163 An address of a function or procedure derived from its name. In C,
6164 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6165 simply the function's name @var{function} (and actually a special case
6166 of a valid expression). In Pascal and Modula-2, this is
6167 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6168 (although the Pascal form also works).
6170 This form specifies the address of the function's first instruction,
6171 before the stack frame and arguments have been set up.
6173 @item '@var{filename}'::@var{funcaddr}
6174 Like @var{funcaddr} above, but also specifies the name of the source
6175 file explicitly. This is useful if the name of the function does not
6176 specify the function unambiguously, e.g., if there are several
6177 functions with identical names in different source files.
6184 @section Editing Source Files
6185 @cindex editing source files
6188 @kindex e @r{(@code{edit})}
6189 To edit the lines in a source file, use the @code{edit} command.
6190 The editing program of your choice
6191 is invoked with the current line set to
6192 the active line in the program.
6193 Alternatively, there are several ways to specify what part of the file you
6194 want to print if you want to see other parts of the program:
6197 @item edit @var{location}
6198 Edit the source file specified by @code{location}. Editing starts at
6199 that @var{location}, e.g., at the specified source line of the
6200 specified file. @xref{Specify Location}, for all the possible forms
6201 of the @var{location} argument; here are the forms of the @code{edit}
6202 command most commonly used:
6205 @item edit @var{number}
6206 Edit the current source file with @var{number} as the active line number.
6208 @item edit @var{function}
6209 Edit the file containing @var{function} at the beginning of its definition.
6214 @subsection Choosing your Editor
6215 You can customize @value{GDBN} to use any editor you want
6217 The only restriction is that your editor (say @code{ex}), recognizes the
6218 following command-line syntax:
6220 ex +@var{number} file
6222 The optional numeric value +@var{number} specifies the number of the line in
6223 the file where to start editing.}.
6224 By default, it is @file{@value{EDITOR}}, but you can change this
6225 by setting the environment variable @code{EDITOR} before using
6226 @value{GDBN}. For example, to configure @value{GDBN} to use the
6227 @code{vi} editor, you could use these commands with the @code{sh} shell:
6233 or in the @code{csh} shell,
6235 setenv EDITOR /usr/bin/vi
6240 @section Searching Source Files
6241 @cindex searching source files
6243 There are two commands for searching through the current source file for a
6248 @kindex forward-search
6249 @item forward-search @var{regexp}
6250 @itemx search @var{regexp}
6251 The command @samp{forward-search @var{regexp}} checks each line,
6252 starting with the one following the last line listed, for a match for
6253 @var{regexp}. It lists the line that is found. You can use the
6254 synonym @samp{search @var{regexp}} or abbreviate the command name as
6257 @kindex reverse-search
6258 @item reverse-search @var{regexp}
6259 The command @samp{reverse-search @var{regexp}} checks each line, starting
6260 with the one before the last line listed and going backward, for a match
6261 for @var{regexp}. It lists the line that is found. You can abbreviate
6262 this command as @code{rev}.
6266 @section Specifying Source Directories
6269 @cindex directories for source files
6270 Executable programs sometimes do not record the directories of the source
6271 files from which they were compiled, just the names. Even when they do,
6272 the directories could be moved between the compilation and your debugging
6273 session. @value{GDBN} has a list of directories to search for source files;
6274 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6275 it tries all the directories in the list, in the order they are present
6276 in the list, until it finds a file with the desired name.
6278 For example, suppose an executable references the file
6279 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6280 @file{/mnt/cross}. The file is first looked up literally; if this
6281 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6282 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6283 message is printed. @value{GDBN} does not look up the parts of the
6284 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6285 Likewise, the subdirectories of the source path are not searched: if
6286 the source path is @file{/mnt/cross}, and the binary refers to
6287 @file{foo.c}, @value{GDBN} would not find it under
6288 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6290 Plain file names, relative file names with leading directories, file
6291 names containing dots, etc.@: are all treated as described above; for
6292 instance, if the source path is @file{/mnt/cross}, and the source file
6293 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6294 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6295 that---@file{/mnt/cross/foo.c}.
6297 Note that the executable search path is @emph{not} used to locate the
6300 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6301 any information it has cached about where source files are found and where
6302 each line is in the file.
6306 When you start @value{GDBN}, its source path includes only @samp{cdir}
6307 and @samp{cwd}, in that order.
6308 To add other directories, use the @code{directory} command.
6310 The search path is used to find both program source files and @value{GDBN}
6311 script files (read using the @samp{-command} option and @samp{source} command).
6313 In addition to the source path, @value{GDBN} provides a set of commands
6314 that manage a list of source path substitution rules. A @dfn{substitution
6315 rule} specifies how to rewrite source directories stored in the program's
6316 debug information in case the sources were moved to a different
6317 directory between compilation and debugging. A rule is made of
6318 two strings, the first specifying what needs to be rewritten in
6319 the path, and the second specifying how it should be rewritten.
6320 In @ref{set substitute-path}, we name these two parts @var{from} and
6321 @var{to} respectively. @value{GDBN} does a simple string replacement
6322 of @var{from} with @var{to} at the start of the directory part of the
6323 source file name, and uses that result instead of the original file
6324 name to look up the sources.
6326 Using the previous example, suppose the @file{foo-1.0} tree has been
6327 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6328 @value{GDBN} to replace @file{/usr/src} in all source path names with
6329 @file{/mnt/cross}. The first lookup will then be
6330 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6331 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6332 substitution rule, use the @code{set substitute-path} command
6333 (@pxref{set substitute-path}).
6335 To avoid unexpected substitution results, a rule is applied only if the
6336 @var{from} part of the directory name ends at a directory separator.
6337 For instance, a rule substituting @file{/usr/source} into
6338 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6339 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6340 is applied only at the beginning of the directory name, this rule will
6341 not be applied to @file{/root/usr/source/baz.c} either.
6343 In many cases, you can achieve the same result using the @code{directory}
6344 command. However, @code{set substitute-path} can be more efficient in
6345 the case where the sources are organized in a complex tree with multiple
6346 subdirectories. With the @code{directory} command, you need to add each
6347 subdirectory of your project. If you moved the entire tree while
6348 preserving its internal organization, then @code{set substitute-path}
6349 allows you to direct the debugger to all the sources with one single
6352 @code{set substitute-path} is also more than just a shortcut command.
6353 The source path is only used if the file at the original location no
6354 longer exists. On the other hand, @code{set substitute-path} modifies
6355 the debugger behavior to look at the rewritten location instead. So, if
6356 for any reason a source file that is not relevant to your executable is
6357 located at the original location, a substitution rule is the only
6358 method available to point @value{GDBN} at the new location.
6360 @cindex @samp{--with-relocated-sources}
6361 @cindex default source path substitution
6362 You can configure a default source path substitution rule by
6363 configuring @value{GDBN} with the
6364 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6365 should be the name of a directory under @value{GDBN}'s configured
6366 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6367 directory names in debug information under @var{dir} will be adjusted
6368 automatically if the installed @value{GDBN} is moved to a new
6369 location. This is useful if @value{GDBN}, libraries or executables
6370 with debug information and corresponding source code are being moved
6374 @item directory @var{dirname} @dots{}
6375 @item dir @var{dirname} @dots{}
6376 Add directory @var{dirname} to the front of the source path. Several
6377 directory names may be given to this command, separated by @samp{:}
6378 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6379 part of absolute file names) or
6380 whitespace. You may specify a directory that is already in the source
6381 path; this moves it forward, so @value{GDBN} searches it sooner.
6385 @vindex $cdir@r{, convenience variable}
6386 @vindex $cwd@r{, convenience variable}
6387 @cindex compilation directory
6388 @cindex current directory
6389 @cindex working directory
6390 @cindex directory, current
6391 @cindex directory, compilation
6392 You can use the string @samp{$cdir} to refer to the compilation
6393 directory (if one is recorded), and @samp{$cwd} to refer to the current
6394 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6395 tracks the current working directory as it changes during your @value{GDBN}
6396 session, while the latter is immediately expanded to the current
6397 directory at the time you add an entry to the source path.
6400 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6402 @c RET-repeat for @code{directory} is explicitly disabled, but since
6403 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6405 @item show directories
6406 @kindex show directories
6407 Print the source path: show which directories it contains.
6409 @anchor{set substitute-path}
6410 @item set substitute-path @var{from} @var{to}
6411 @kindex set substitute-path
6412 Define a source path substitution rule, and add it at the end of the
6413 current list of existing substitution rules. If a rule with the same
6414 @var{from} was already defined, then the old rule is also deleted.
6416 For example, if the file @file{/foo/bar/baz.c} was moved to
6417 @file{/mnt/cross/baz.c}, then the command
6420 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6424 will tell @value{GDBN} to replace @samp{/usr/src} with
6425 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6426 @file{baz.c} even though it was moved.
6428 In the case when more than one substitution rule have been defined,
6429 the rules are evaluated one by one in the order where they have been
6430 defined. The first one matching, if any, is selected to perform
6433 For instance, if we had entered the following commands:
6436 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6437 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6441 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6442 @file{/mnt/include/defs.h} by using the first rule. However, it would
6443 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6444 @file{/mnt/src/lib/foo.c}.
6447 @item unset substitute-path [path]
6448 @kindex unset substitute-path
6449 If a path is specified, search the current list of substitution rules
6450 for a rule that would rewrite that path. Delete that rule if found.
6451 A warning is emitted by the debugger if no rule could be found.
6453 If no path is specified, then all substitution rules are deleted.
6455 @item show substitute-path [path]
6456 @kindex show substitute-path
6457 If a path is specified, then print the source path substitution rule
6458 which would rewrite that path, if any.
6460 If no path is specified, then print all existing source path substitution
6465 If your source path is cluttered with directories that are no longer of
6466 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6467 versions of source. You can correct the situation as follows:
6471 Use @code{directory} with no argument to reset the source path to its default value.
6474 Use @code{directory} with suitable arguments to reinstall the
6475 directories you want in the source path. You can add all the
6476 directories in one command.
6480 @section Source and Machine Code
6481 @cindex source line and its code address
6483 You can use the command @code{info line} to map source lines to program
6484 addresses (and vice versa), and the command @code{disassemble} to display
6485 a range of addresses as machine instructions. You can use the command
6486 @code{set disassemble-next-line} to set whether to disassemble next
6487 source line when execution stops. When run under @sc{gnu} Emacs
6488 mode, the @code{info line} command causes the arrow to point to the
6489 line specified. Also, @code{info line} prints addresses in symbolic form as
6494 @item info line @var{linespec}
6495 Print the starting and ending addresses of the compiled code for
6496 source line @var{linespec}. You can specify source lines in any of
6497 the ways documented in @ref{Specify Location}.
6500 For example, we can use @code{info line} to discover the location of
6501 the object code for the first line of function
6502 @code{m4_changequote}:
6504 @c FIXME: I think this example should also show the addresses in
6505 @c symbolic form, as they usually would be displayed.
6507 (@value{GDBP}) info line m4_changequote
6508 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6512 @cindex code address and its source line
6513 We can also inquire (using @code{*@var{addr}} as the form for
6514 @var{linespec}) what source line covers a particular address:
6516 (@value{GDBP}) info line *0x63ff
6517 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6520 @cindex @code{$_} and @code{info line}
6521 @cindex @code{x} command, default address
6522 @kindex x@r{(examine), and} info line
6523 After @code{info line}, the default address for the @code{x} command
6524 is changed to the starting address of the line, so that @samp{x/i} is
6525 sufficient to begin examining the machine code (@pxref{Memory,
6526 ,Examining Memory}). Also, this address is saved as the value of the
6527 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6532 @cindex assembly instructions
6533 @cindex instructions, assembly
6534 @cindex machine instructions
6535 @cindex listing machine instructions
6537 @itemx disassemble /m
6538 @itemx disassemble /r
6539 This specialized command dumps a range of memory as machine
6540 instructions. It can also print mixed source+disassembly by specifying
6541 the @code{/m} modifier and print the raw instructions in hex as well as
6542 in symbolic form by specifying the @code{/r}.
6543 The default memory range is the function surrounding the
6544 program counter of the selected frame. A single argument to this
6545 command is a program counter value; @value{GDBN} dumps the function
6546 surrounding this value. When two arguments are given, they should
6547 be separated by a comma, possibly surrounded by whitespace. The
6548 arguments specify a range of addresses (first inclusive, second exclusive)
6549 to dump. In that case, the name of the function is also printed (since
6550 there could be several functions in the given range).
6552 The argument(s) can be any expression yielding a numeric value, such as
6553 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6555 If the range of memory being disassembled contains current program counter,
6556 the instruction at that location is shown with a @code{=>} marker.
6559 The following example shows the disassembly of a range of addresses of
6560 HP PA-RISC 2.0 code:
6563 (@value{GDBP}) disas 0x32c4, 0x32e4
6564 Dump of assembler code from 0x32c4 to 0x32e4:
6565 0x32c4 <main+204>: addil 0,dp
6566 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6567 0x32cc <main+212>: ldil 0x3000,r31
6568 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6569 0x32d4 <main+220>: ldo 0(r31),rp
6570 0x32d8 <main+224>: addil -0x800,dp
6571 0x32dc <main+228>: ldo 0x588(r1),r26
6572 0x32e0 <main+232>: ldil 0x3000,r31
6573 End of assembler dump.
6576 Here is an example showing mixed source+assembly for Intel x86, when the
6577 program is stopped just after function prologue:
6580 (@value{GDBP}) disas /m main
6581 Dump of assembler code for function main:
6583 0x08048330 <+0>: push %ebp
6584 0x08048331 <+1>: mov %esp,%ebp
6585 0x08048333 <+3>: sub $0x8,%esp
6586 0x08048336 <+6>: and $0xfffffff0,%esp
6587 0x08048339 <+9>: sub $0x10,%esp
6589 6 printf ("Hello.\n");
6590 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6591 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6595 0x08048348 <+24>: mov $0x0,%eax
6596 0x0804834d <+29>: leave
6597 0x0804834e <+30>: ret
6599 End of assembler dump.
6602 Some architectures have more than one commonly-used set of instruction
6603 mnemonics or other syntax.
6605 For programs that were dynamically linked and use shared libraries,
6606 instructions that call functions or branch to locations in the shared
6607 libraries might show a seemingly bogus location---it's actually a
6608 location of the relocation table. On some architectures, @value{GDBN}
6609 might be able to resolve these to actual function names.
6612 @kindex set disassembly-flavor
6613 @cindex Intel disassembly flavor
6614 @cindex AT&T disassembly flavor
6615 @item set disassembly-flavor @var{instruction-set}
6616 Select the instruction set to use when disassembling the
6617 program via the @code{disassemble} or @code{x/i} commands.
6619 Currently this command is only defined for the Intel x86 family. You
6620 can set @var{instruction-set} to either @code{intel} or @code{att}.
6621 The default is @code{att}, the AT&T flavor used by default by Unix
6622 assemblers for x86-based targets.
6624 @kindex show disassembly-flavor
6625 @item show disassembly-flavor
6626 Show the current setting of the disassembly flavor.
6630 @kindex set disassemble-next-line
6631 @kindex show disassemble-next-line
6632 @item set disassemble-next-line
6633 @itemx show disassemble-next-line
6634 Control whether or not @value{GDBN} will disassemble the next source
6635 line or instruction when execution stops. If ON, @value{GDBN} will
6636 display disassembly of the next source line when execution of the
6637 program being debugged stops. This is @emph{in addition} to
6638 displaying the source line itself, which @value{GDBN} always does if
6639 possible. If the next source line cannot be displayed for some reason
6640 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6641 info in the debug info), @value{GDBN} will display disassembly of the
6642 next @emph{instruction} instead of showing the next source line. If
6643 AUTO, @value{GDBN} will display disassembly of next instruction only
6644 if the source line cannot be displayed. This setting causes
6645 @value{GDBN} to display some feedback when you step through a function
6646 with no line info or whose source file is unavailable. The default is
6647 OFF, which means never display the disassembly of the next line or
6653 @chapter Examining Data
6655 @cindex printing data
6656 @cindex examining data
6659 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6660 @c document because it is nonstandard... Under Epoch it displays in a
6661 @c different window or something like that.
6662 The usual way to examine data in your program is with the @code{print}
6663 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6664 evaluates and prints the value of an expression of the language your
6665 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6666 Different Languages}). It may also print the expression using a
6667 Python-based pretty-printer (@pxref{Pretty Printing}).
6670 @item print @var{expr}
6671 @itemx print /@var{f} @var{expr}
6672 @var{expr} is an expression (in the source language). By default the
6673 value of @var{expr} is printed in a format appropriate to its data type;
6674 you can choose a different format by specifying @samp{/@var{f}}, where
6675 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6679 @itemx print /@var{f}
6680 @cindex reprint the last value
6681 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6682 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6683 conveniently inspect the same value in an alternative format.
6686 A more low-level way of examining data is with the @code{x} command.
6687 It examines data in memory at a specified address and prints it in a
6688 specified format. @xref{Memory, ,Examining Memory}.
6690 If you are interested in information about types, or about how the
6691 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6692 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6696 * Expressions:: Expressions
6697 * Ambiguous Expressions:: Ambiguous Expressions
6698 * Variables:: Program variables
6699 * Arrays:: Artificial arrays
6700 * Output Formats:: Output formats
6701 * Memory:: Examining memory
6702 * Auto Display:: Automatic display
6703 * Print Settings:: Print settings
6704 * Value History:: Value history
6705 * Convenience Vars:: Convenience variables
6706 * Registers:: Registers
6707 * Floating Point Hardware:: Floating point hardware
6708 * Vector Unit:: Vector Unit
6709 * OS Information:: Auxiliary data provided by operating system
6710 * Memory Region Attributes:: Memory region attributes
6711 * Dump/Restore Files:: Copy between memory and a file
6712 * Core File Generation:: Cause a program dump its core
6713 * Character Sets:: Debugging programs that use a different
6714 character set than GDB does
6715 * Caching Remote Data:: Data caching for remote targets
6716 * Searching Memory:: Searching memory for a sequence of bytes
6720 @section Expressions
6723 @code{print} and many other @value{GDBN} commands accept an expression and
6724 compute its value. Any kind of constant, variable or operator defined
6725 by the programming language you are using is valid in an expression in
6726 @value{GDBN}. This includes conditional expressions, function calls,
6727 casts, and string constants. It also includes preprocessor macros, if
6728 you compiled your program to include this information; see
6731 @cindex arrays in expressions
6732 @value{GDBN} supports array constants in expressions input by
6733 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6734 you can use the command @code{print @{1, 2, 3@}} to create an array
6735 of three integers. If you pass an array to a function or assign it
6736 to a program variable, @value{GDBN} copies the array to memory that
6737 is @code{malloc}ed in the target program.
6739 Because C is so widespread, most of the expressions shown in examples in
6740 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6741 Languages}, for information on how to use expressions in other
6744 In this section, we discuss operators that you can use in @value{GDBN}
6745 expressions regardless of your programming language.
6747 @cindex casts, in expressions
6748 Casts are supported in all languages, not just in C, because it is so
6749 useful to cast a number into a pointer in order to examine a structure
6750 at that address in memory.
6751 @c FIXME: casts supported---Mod2 true?
6753 @value{GDBN} supports these operators, in addition to those common
6754 to programming languages:
6758 @samp{@@} is a binary operator for treating parts of memory as arrays.
6759 @xref{Arrays, ,Artificial Arrays}, for more information.
6762 @samp{::} allows you to specify a variable in terms of the file or
6763 function where it is defined. @xref{Variables, ,Program Variables}.
6765 @cindex @{@var{type}@}
6766 @cindex type casting memory
6767 @cindex memory, viewing as typed object
6768 @cindex casts, to view memory
6769 @item @{@var{type}@} @var{addr}
6770 Refers to an object of type @var{type} stored at address @var{addr} in
6771 memory. @var{addr} may be any expression whose value is an integer or
6772 pointer (but parentheses are required around binary operators, just as in
6773 a cast). This construct is allowed regardless of what kind of data is
6774 normally supposed to reside at @var{addr}.
6777 @node Ambiguous Expressions
6778 @section Ambiguous Expressions
6779 @cindex ambiguous expressions
6781 Expressions can sometimes contain some ambiguous elements. For instance,
6782 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6783 a single function name to be defined several times, for application in
6784 different contexts. This is called @dfn{overloading}. Another example
6785 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6786 templates and is typically instantiated several times, resulting in
6787 the same function name being defined in different contexts.
6789 In some cases and depending on the language, it is possible to adjust
6790 the expression to remove the ambiguity. For instance in C@t{++}, you
6791 can specify the signature of the function you want to break on, as in
6792 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6793 qualified name of your function often makes the expression unambiguous
6796 When an ambiguity that needs to be resolved is detected, the debugger
6797 has the capability to display a menu of numbered choices for each
6798 possibility, and then waits for the selection with the prompt @samp{>}.
6799 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6800 aborts the current command. If the command in which the expression was
6801 used allows more than one choice to be selected, the next option in the
6802 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6805 For example, the following session excerpt shows an attempt to set a
6806 breakpoint at the overloaded symbol @code{String::after}.
6807 We choose three particular definitions of that function name:
6809 @c FIXME! This is likely to change to show arg type lists, at least
6812 (@value{GDBP}) b String::after
6815 [2] file:String.cc; line number:867
6816 [3] file:String.cc; line number:860
6817 [4] file:String.cc; line number:875
6818 [5] file:String.cc; line number:853
6819 [6] file:String.cc; line number:846
6820 [7] file:String.cc; line number:735
6822 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6823 Breakpoint 2 at 0xb344: file String.cc, line 875.
6824 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6825 Multiple breakpoints were set.
6826 Use the "delete" command to delete unwanted
6833 @kindex set multiple-symbols
6834 @item set multiple-symbols @var{mode}
6835 @cindex multiple-symbols menu
6837 This option allows you to adjust the debugger behavior when an expression
6840 By default, @var{mode} is set to @code{all}. If the command with which
6841 the expression is used allows more than one choice, then @value{GDBN}
6842 automatically selects all possible choices. For instance, inserting
6843 a breakpoint on a function using an ambiguous name results in a breakpoint
6844 inserted on each possible match. However, if a unique choice must be made,
6845 then @value{GDBN} uses the menu to help you disambiguate the expression.
6846 For instance, printing the address of an overloaded function will result
6847 in the use of the menu.
6849 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6850 when an ambiguity is detected.
6852 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6853 an error due to the ambiguity and the command is aborted.
6855 @kindex show multiple-symbols
6856 @item show multiple-symbols
6857 Show the current value of the @code{multiple-symbols} setting.
6861 @section Program Variables
6863 The most common kind of expression to use is the name of a variable
6866 Variables in expressions are understood in the selected stack frame
6867 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6871 global (or file-static)
6878 visible according to the scope rules of the
6879 programming language from the point of execution in that frame
6882 @noindent This means that in the function
6897 you can examine and use the variable @code{a} whenever your program is
6898 executing within the function @code{foo}, but you can only use or
6899 examine the variable @code{b} while your program is executing inside
6900 the block where @code{b} is declared.
6902 @cindex variable name conflict
6903 There is an exception: you can refer to a variable or function whose
6904 scope is a single source file even if the current execution point is not
6905 in this file. But it is possible to have more than one such variable or
6906 function with the same name (in different source files). If that
6907 happens, referring to that name has unpredictable effects. If you wish,
6908 you can specify a static variable in a particular function or file,
6909 using the colon-colon (@code{::}) notation:
6911 @cindex colon-colon, context for variables/functions
6913 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6914 @cindex @code{::}, context for variables/functions
6917 @var{file}::@var{variable}
6918 @var{function}::@var{variable}
6922 Here @var{file} or @var{function} is the name of the context for the
6923 static @var{variable}. In the case of file names, you can use quotes to
6924 make sure @value{GDBN} parses the file name as a single word---for example,
6925 to print a global value of @code{x} defined in @file{f2.c}:
6928 (@value{GDBP}) p 'f2.c'::x
6931 @cindex C@t{++} scope resolution
6932 This use of @samp{::} is very rarely in conflict with the very similar
6933 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6934 scope resolution operator in @value{GDBN} expressions.
6935 @c FIXME: Um, so what happens in one of those rare cases where it's in
6938 @cindex wrong values
6939 @cindex variable values, wrong
6940 @cindex function entry/exit, wrong values of variables
6941 @cindex optimized code, wrong values of variables
6943 @emph{Warning:} Occasionally, a local variable may appear to have the
6944 wrong value at certain points in a function---just after entry to a new
6945 scope, and just before exit.
6947 You may see this problem when you are stepping by machine instructions.
6948 This is because, on most machines, it takes more than one instruction to
6949 set up a stack frame (including local variable definitions); if you are
6950 stepping by machine instructions, variables may appear to have the wrong
6951 values until the stack frame is completely built. On exit, it usually
6952 also takes more than one machine instruction to destroy a stack frame;
6953 after you begin stepping through that group of instructions, local
6954 variable definitions may be gone.
6956 This may also happen when the compiler does significant optimizations.
6957 To be sure of always seeing accurate values, turn off all optimization
6960 @cindex ``No symbol "foo" in current context''
6961 Another possible effect of compiler optimizations is to optimize
6962 unused variables out of existence, or assign variables to registers (as
6963 opposed to memory addresses). Depending on the support for such cases
6964 offered by the debug info format used by the compiler, @value{GDBN}
6965 might not be able to display values for such local variables. If that
6966 happens, @value{GDBN} will print a message like this:
6969 No symbol "foo" in current context.
6972 To solve such problems, either recompile without optimizations, or use a
6973 different debug info format, if the compiler supports several such
6974 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6975 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6976 produces debug info in a format that is superior to formats such as
6977 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6978 an effective form for debug info. @xref{Debugging Options,,Options
6979 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6980 Compiler Collection (GCC)}.
6981 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6982 that are best suited to C@t{++} programs.
6984 If you ask to print an object whose contents are unknown to
6985 @value{GDBN}, e.g., because its data type is not completely specified
6986 by the debug information, @value{GDBN} will say @samp{<incomplete
6987 type>}. @xref{Symbols, incomplete type}, for more about this.
6989 Strings are identified as arrays of @code{char} values without specified
6990 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6991 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6992 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6993 defines literal string type @code{"char"} as @code{char} without a sign.
6998 signed char var1[] = "A";
7001 You get during debugging
7006 $2 = @{65 'A', 0 '\0'@}
7010 @section Artificial Arrays
7012 @cindex artificial array
7014 @kindex @@@r{, referencing memory as an array}
7015 It is often useful to print out several successive objects of the
7016 same type in memory; a section of an array, or an array of
7017 dynamically determined size for which only a pointer exists in the
7020 You can do this by referring to a contiguous span of memory as an
7021 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7022 operand of @samp{@@} should be the first element of the desired array
7023 and be an individual object. The right operand should be the desired length
7024 of the array. The result is an array value whose elements are all of
7025 the type of the left argument. The first element is actually the left
7026 argument; the second element comes from bytes of memory immediately
7027 following those that hold the first element, and so on. Here is an
7028 example. If a program says
7031 int *array = (int *) malloc (len * sizeof (int));
7035 you can print the contents of @code{array} with
7041 The left operand of @samp{@@} must reside in memory. Array values made
7042 with @samp{@@} in this way behave just like other arrays in terms of
7043 subscripting, and are coerced to pointers when used in expressions.
7044 Artificial arrays most often appear in expressions via the value history
7045 (@pxref{Value History, ,Value History}), after printing one out.
7047 Another way to create an artificial array is to use a cast.
7048 This re-interprets a value as if it were an array.
7049 The value need not be in memory:
7051 (@value{GDBP}) p/x (short[2])0x12345678
7052 $1 = @{0x1234, 0x5678@}
7055 As a convenience, if you leave the array length out (as in
7056 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7057 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7059 (@value{GDBP}) p/x (short[])0x12345678
7060 $2 = @{0x1234, 0x5678@}
7063 Sometimes the artificial array mechanism is not quite enough; in
7064 moderately complex data structures, the elements of interest may not
7065 actually be adjacent---for example, if you are interested in the values
7066 of pointers in an array. One useful work-around in this situation is
7067 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7068 Variables}) as a counter in an expression that prints the first
7069 interesting value, and then repeat that expression via @key{RET}. For
7070 instance, suppose you have an array @code{dtab} of pointers to
7071 structures, and you are interested in the values of a field @code{fv}
7072 in each structure. Here is an example of what you might type:
7082 @node Output Formats
7083 @section Output Formats
7085 @cindex formatted output
7086 @cindex output formats
7087 By default, @value{GDBN} prints a value according to its data type. Sometimes
7088 this is not what you want. For example, you might want to print a number
7089 in hex, or a pointer in decimal. Or you might want to view data in memory
7090 at a certain address as a character string or as an instruction. To do
7091 these things, specify an @dfn{output format} when you print a value.
7093 The simplest use of output formats is to say how to print a value
7094 already computed. This is done by starting the arguments of the
7095 @code{print} command with a slash and a format letter. The format
7096 letters supported are:
7100 Regard the bits of the value as an integer, and print the integer in
7104 Print as integer in signed decimal.
7107 Print as integer in unsigned decimal.
7110 Print as integer in octal.
7113 Print as integer in binary. The letter @samp{t} stands for ``two''.
7114 @footnote{@samp{b} cannot be used because these format letters are also
7115 used with the @code{x} command, where @samp{b} stands for ``byte'';
7116 see @ref{Memory,,Examining Memory}.}
7119 @cindex unknown address, locating
7120 @cindex locate address
7121 Print as an address, both absolute in hexadecimal and as an offset from
7122 the nearest preceding symbol. You can use this format used to discover
7123 where (in what function) an unknown address is located:
7126 (@value{GDBP}) p/a 0x54320
7127 $3 = 0x54320 <_initialize_vx+396>
7131 The command @code{info symbol 0x54320} yields similar results.
7132 @xref{Symbols, info symbol}.
7135 Regard as an integer and print it as a character constant. This
7136 prints both the numerical value and its character representation. The
7137 character representation is replaced with the octal escape @samp{\nnn}
7138 for characters outside the 7-bit @sc{ascii} range.
7140 Without this format, @value{GDBN} displays @code{char},
7141 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7142 constants. Single-byte members of vectors are displayed as integer
7146 Regard the bits of the value as a floating point number and print
7147 using typical floating point syntax.
7150 @cindex printing strings
7151 @cindex printing byte arrays
7152 Regard as a string, if possible. With this format, pointers to single-byte
7153 data are displayed as null-terminated strings and arrays of single-byte data
7154 are displayed as fixed-length strings. Other values are displayed in their
7157 Without this format, @value{GDBN} displays pointers to and arrays of
7158 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7159 strings. Single-byte members of a vector are displayed as an integer
7163 @cindex raw printing
7164 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7165 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7166 Printing}). This typically results in a higher-level display of the
7167 value's contents. The @samp{r} format bypasses any Python
7168 pretty-printer which might exist.
7171 For example, to print the program counter in hex (@pxref{Registers}), type
7178 Note that no space is required before the slash; this is because command
7179 names in @value{GDBN} cannot contain a slash.
7181 To reprint the last value in the value history with a different format,
7182 you can use the @code{print} command with just a format and no
7183 expression. For example, @samp{p/x} reprints the last value in hex.
7186 @section Examining Memory
7188 You can use the command @code{x} (for ``examine'') to examine memory in
7189 any of several formats, independently of your program's data types.
7191 @cindex examining memory
7193 @kindex x @r{(examine memory)}
7194 @item x/@var{nfu} @var{addr}
7197 Use the @code{x} command to examine memory.
7200 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7201 much memory to display and how to format it; @var{addr} is an
7202 expression giving the address where you want to start displaying memory.
7203 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7204 Several commands set convenient defaults for @var{addr}.
7207 @item @var{n}, the repeat count
7208 The repeat count is a decimal integer; the default is 1. It specifies
7209 how much memory (counting by units @var{u}) to display.
7210 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7213 @item @var{f}, the display format
7214 The display format is one of the formats used by @code{print}
7215 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7216 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7217 The default is @samp{x} (hexadecimal) initially. The default changes
7218 each time you use either @code{x} or @code{print}.
7220 @item @var{u}, the unit size
7221 The unit size is any of
7227 Halfwords (two bytes).
7229 Words (four bytes). This is the initial default.
7231 Giant words (eight bytes).
7234 Each time you specify a unit size with @code{x}, that size becomes the
7235 default unit the next time you use @code{x}. (For the @samp{s} and
7236 @samp{i} formats, the unit size is ignored and is normally not written.)
7238 @item @var{addr}, starting display address
7239 @var{addr} is the address where you want @value{GDBN} to begin displaying
7240 memory. The expression need not have a pointer value (though it may);
7241 it is always interpreted as an integer address of a byte of memory.
7242 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7243 @var{addr} is usually just after the last address examined---but several
7244 other commands also set the default address: @code{info breakpoints} (to
7245 the address of the last breakpoint listed), @code{info line} (to the
7246 starting address of a line), and @code{print} (if you use it to display
7247 a value from memory).
7250 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7251 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7252 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7253 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7254 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7256 Since the letters indicating unit sizes are all distinct from the
7257 letters specifying output formats, you do not have to remember whether
7258 unit size or format comes first; either order works. The output
7259 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7260 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7262 Even though the unit size @var{u} is ignored for the formats @samp{s}
7263 and @samp{i}, you might still want to use a count @var{n}; for example,
7264 @samp{3i} specifies that you want to see three machine instructions,
7265 including any operands. For convenience, especially when used with
7266 the @code{display} command, the @samp{i} format also prints branch delay
7267 slot instructions, if any, beyond the count specified, which immediately
7268 follow the last instruction that is within the count. The command
7269 @code{disassemble} gives an alternative way of inspecting machine
7270 instructions; see @ref{Machine Code,,Source and Machine Code}.
7272 All the defaults for the arguments to @code{x} are designed to make it
7273 easy to continue scanning memory with minimal specifications each time
7274 you use @code{x}. For example, after you have inspected three machine
7275 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7276 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7277 the repeat count @var{n} is used again; the other arguments default as
7278 for successive uses of @code{x}.
7280 When examining machine instructions, the instruction at current program
7281 counter is shown with a @code{=>} marker. For example:
7284 (@value{GDBP}) x/5i $pc-6
7285 0x804837f <main+11>: mov %esp,%ebp
7286 0x8048381 <main+13>: push %ecx
7287 0x8048382 <main+14>: sub $0x4,%esp
7288 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7289 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7292 @cindex @code{$_}, @code{$__}, and value history
7293 The addresses and contents printed by the @code{x} command are not saved
7294 in the value history because there is often too much of them and they
7295 would get in the way. Instead, @value{GDBN} makes these values available for
7296 subsequent use in expressions as values of the convenience variables
7297 @code{$_} and @code{$__}. After an @code{x} command, the last address
7298 examined is available for use in expressions in the convenience variable
7299 @code{$_}. The contents of that address, as examined, are available in
7300 the convenience variable @code{$__}.
7302 If the @code{x} command has a repeat count, the address and contents saved
7303 are from the last memory unit printed; this is not the same as the last
7304 address printed if several units were printed on the last line of output.
7306 @cindex remote memory comparison
7307 @cindex verify remote memory image
7308 When you are debugging a program running on a remote target machine
7309 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7310 remote machine's memory against the executable file you downloaded to
7311 the target. The @code{compare-sections} command is provided for such
7315 @kindex compare-sections
7316 @item compare-sections @r{[}@var{section-name}@r{]}
7317 Compare the data of a loadable section @var{section-name} in the
7318 executable file of the program being debugged with the same section in
7319 the remote machine's memory, and report any mismatches. With no
7320 arguments, compares all loadable sections. This command's
7321 availability depends on the target's support for the @code{"qCRC"}
7326 @section Automatic Display
7327 @cindex automatic display
7328 @cindex display of expressions
7330 If you find that you want to print the value of an expression frequently
7331 (to see how it changes), you might want to add it to the @dfn{automatic
7332 display list} so that @value{GDBN} prints its value each time your program stops.
7333 Each expression added to the list is given a number to identify it;
7334 to remove an expression from the list, you specify that number.
7335 The automatic display looks like this:
7339 3: bar[5] = (struct hack *) 0x3804
7343 This display shows item numbers, expressions and their current values. As with
7344 displays you request manually using @code{x} or @code{print}, you can
7345 specify the output format you prefer; in fact, @code{display} decides
7346 whether to use @code{print} or @code{x} depending your format
7347 specification---it uses @code{x} if you specify either the @samp{i}
7348 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7352 @item display @var{expr}
7353 Add the expression @var{expr} to the list of expressions to display
7354 each time your program stops. @xref{Expressions, ,Expressions}.
7356 @code{display} does not repeat if you press @key{RET} again after using it.
7358 @item display/@var{fmt} @var{expr}
7359 For @var{fmt} specifying only a display format and not a size or
7360 count, add the expression @var{expr} to the auto-display list but
7361 arrange to display it each time in the specified format @var{fmt}.
7362 @xref{Output Formats,,Output Formats}.
7364 @item display/@var{fmt} @var{addr}
7365 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7366 number of units, add the expression @var{addr} as a memory address to
7367 be examined each time your program stops. Examining means in effect
7368 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7371 For example, @samp{display/i $pc} can be helpful, to see the machine
7372 instruction about to be executed each time execution stops (@samp{$pc}
7373 is a common name for the program counter; @pxref{Registers, ,Registers}).
7376 @kindex delete display
7378 @item undisplay @var{dnums}@dots{}
7379 @itemx delete display @var{dnums}@dots{}
7380 Remove item numbers @var{dnums} from the list of expressions to display.
7382 @code{undisplay} does not repeat if you press @key{RET} after using it.
7383 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7385 @kindex disable display
7386 @item disable display @var{dnums}@dots{}
7387 Disable the display of item numbers @var{dnums}. A disabled display
7388 item is not printed automatically, but is not forgotten. It may be
7389 enabled again later.
7391 @kindex enable display
7392 @item enable display @var{dnums}@dots{}
7393 Enable display of item numbers @var{dnums}. It becomes effective once
7394 again in auto display of its expression, until you specify otherwise.
7397 Display the current values of the expressions on the list, just as is
7398 done when your program stops.
7400 @kindex info display
7402 Print the list of expressions previously set up to display
7403 automatically, each one with its item number, but without showing the
7404 values. This includes disabled expressions, which are marked as such.
7405 It also includes expressions which would not be displayed right now
7406 because they refer to automatic variables not currently available.
7409 @cindex display disabled out of scope
7410 If a display expression refers to local variables, then it does not make
7411 sense outside the lexical context for which it was set up. Such an
7412 expression is disabled when execution enters a context where one of its
7413 variables is not defined. For example, if you give the command
7414 @code{display last_char} while inside a function with an argument
7415 @code{last_char}, @value{GDBN} displays this argument while your program
7416 continues to stop inside that function. When it stops elsewhere---where
7417 there is no variable @code{last_char}---the display is disabled
7418 automatically. The next time your program stops where @code{last_char}
7419 is meaningful, you can enable the display expression once again.
7421 @node Print Settings
7422 @section Print Settings
7424 @cindex format options
7425 @cindex print settings
7426 @value{GDBN} provides the following ways to control how arrays, structures,
7427 and symbols are printed.
7430 These settings are useful for debugging programs in any language:
7434 @item set print address
7435 @itemx set print address on
7436 @cindex print/don't print memory addresses
7437 @value{GDBN} prints memory addresses showing the location of stack
7438 traces, structure values, pointer values, breakpoints, and so forth,
7439 even when it also displays the contents of those addresses. The default
7440 is @code{on}. For example, this is what a stack frame display looks like with
7441 @code{set print address on}:
7446 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7448 530 if (lquote != def_lquote)
7452 @item set print address off
7453 Do not print addresses when displaying their contents. For example,
7454 this is the same stack frame displayed with @code{set print address off}:
7458 (@value{GDBP}) set print addr off
7460 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7461 530 if (lquote != def_lquote)
7465 You can use @samp{set print address off} to eliminate all machine
7466 dependent displays from the @value{GDBN} interface. For example, with
7467 @code{print address off}, you should get the same text for backtraces on
7468 all machines---whether or not they involve pointer arguments.
7471 @item show print address
7472 Show whether or not addresses are to be printed.
7475 When @value{GDBN} prints a symbolic address, it normally prints the
7476 closest earlier symbol plus an offset. If that symbol does not uniquely
7477 identify the address (for example, it is a name whose scope is a single
7478 source file), you may need to clarify. One way to do this is with
7479 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7480 you can set @value{GDBN} to print the source file and line number when
7481 it prints a symbolic address:
7484 @item set print symbol-filename on
7485 @cindex source file and line of a symbol
7486 @cindex symbol, source file and line
7487 Tell @value{GDBN} to print the source file name and line number of a
7488 symbol in the symbolic form of an address.
7490 @item set print symbol-filename off
7491 Do not print source file name and line number of a symbol. This is the
7494 @item show print symbol-filename
7495 Show whether or not @value{GDBN} will print the source file name and
7496 line number of a symbol in the symbolic form of an address.
7499 Another situation where it is helpful to show symbol filenames and line
7500 numbers is when disassembling code; @value{GDBN} shows you the line
7501 number and source file that corresponds to each instruction.
7503 Also, you may wish to see the symbolic form only if the address being
7504 printed is reasonably close to the closest earlier symbol:
7507 @item set print max-symbolic-offset @var{max-offset}
7508 @cindex maximum value for offset of closest symbol
7509 Tell @value{GDBN} to only display the symbolic form of an address if the
7510 offset between the closest earlier symbol and the address is less than
7511 @var{max-offset}. The default is 0, which tells @value{GDBN}
7512 to always print the symbolic form of an address if any symbol precedes it.
7514 @item show print max-symbolic-offset
7515 Ask how large the maximum offset is that @value{GDBN} prints in a
7519 @cindex wild pointer, interpreting
7520 @cindex pointer, finding referent
7521 If you have a pointer and you are not sure where it points, try
7522 @samp{set print symbol-filename on}. Then you can determine the name
7523 and source file location of the variable where it points, using
7524 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7525 For example, here @value{GDBN} shows that a variable @code{ptt} points
7526 at another variable @code{t}, defined in @file{hi2.c}:
7529 (@value{GDBP}) set print symbol-filename on
7530 (@value{GDBP}) p/a ptt
7531 $4 = 0xe008 <t in hi2.c>
7535 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7536 does not show the symbol name and filename of the referent, even with
7537 the appropriate @code{set print} options turned on.
7540 Other settings control how different kinds of objects are printed:
7543 @item set print array
7544 @itemx set print array on
7545 @cindex pretty print arrays
7546 Pretty print arrays. This format is more convenient to read,
7547 but uses more space. The default is off.
7549 @item set print array off
7550 Return to compressed format for arrays.
7552 @item show print array
7553 Show whether compressed or pretty format is selected for displaying
7556 @cindex print array indexes
7557 @item set print array-indexes
7558 @itemx set print array-indexes on
7559 Print the index of each element when displaying arrays. May be more
7560 convenient to locate a given element in the array or quickly find the
7561 index of a given element in that printed array. The default is off.
7563 @item set print array-indexes off
7564 Stop printing element indexes when displaying arrays.
7566 @item show print array-indexes
7567 Show whether the index of each element is printed when displaying
7570 @item set print elements @var{number-of-elements}
7571 @cindex number of array elements to print
7572 @cindex limit on number of printed array elements
7573 Set a limit on how many elements of an array @value{GDBN} will print.
7574 If @value{GDBN} is printing a large array, it stops printing after it has
7575 printed the number of elements set by the @code{set print elements} command.
7576 This limit also applies to the display of strings.
7577 When @value{GDBN} starts, this limit is set to 200.
7578 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7580 @item show print elements
7581 Display the number of elements of a large array that @value{GDBN} will print.
7582 If the number is 0, then the printing is unlimited.
7584 @item set print frame-arguments @var{value}
7585 @kindex set print frame-arguments
7586 @cindex printing frame argument values
7587 @cindex print all frame argument values
7588 @cindex print frame argument values for scalars only
7589 @cindex do not print frame argument values
7590 This command allows to control how the values of arguments are printed
7591 when the debugger prints a frame (@pxref{Frames}). The possible
7596 The values of all arguments are printed.
7599 Print the value of an argument only if it is a scalar. The value of more
7600 complex arguments such as arrays, structures, unions, etc, is replaced
7601 by @code{@dots{}}. This is the default. Here is an example where
7602 only scalar arguments are shown:
7605 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7610 None of the argument values are printed. Instead, the value of each argument
7611 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7614 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7619 By default, only scalar arguments are printed. This command can be used
7620 to configure the debugger to print the value of all arguments, regardless
7621 of their type. However, it is often advantageous to not print the value
7622 of more complex parameters. For instance, it reduces the amount of
7623 information printed in each frame, making the backtrace more readable.
7624 Also, it improves performance when displaying Ada frames, because
7625 the computation of large arguments can sometimes be CPU-intensive,
7626 especially in large applications. Setting @code{print frame-arguments}
7627 to @code{scalars} (the default) or @code{none} avoids this computation,
7628 thus speeding up the display of each Ada frame.
7630 @item show print frame-arguments
7631 Show how the value of arguments should be displayed when printing a frame.
7633 @item set print repeats
7634 @cindex repeated array elements
7635 Set the threshold for suppressing display of repeated array
7636 elements. When the number of consecutive identical elements of an
7637 array exceeds the threshold, @value{GDBN} prints the string
7638 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7639 identical repetitions, instead of displaying the identical elements
7640 themselves. Setting the threshold to zero will cause all elements to
7641 be individually printed. The default threshold is 10.
7643 @item show print repeats
7644 Display the current threshold for printing repeated identical
7647 @item set print null-stop
7648 @cindex @sc{null} elements in arrays
7649 Cause @value{GDBN} to stop printing the characters of an array when the first
7650 @sc{null} is encountered. This is useful when large arrays actually
7651 contain only short strings.
7654 @item show print null-stop
7655 Show whether @value{GDBN} stops printing an array on the first
7656 @sc{null} character.
7658 @item set print pretty on
7659 @cindex print structures in indented form
7660 @cindex indentation in structure display
7661 Cause @value{GDBN} to print structures in an indented format with one member
7662 per line, like this:
7677 @item set print pretty off
7678 Cause @value{GDBN} to print structures in a compact format, like this:
7682 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7683 meat = 0x54 "Pork"@}
7688 This is the default format.
7690 @item show print pretty
7691 Show which format @value{GDBN} is using to print structures.
7693 @item set print sevenbit-strings on
7694 @cindex eight-bit characters in strings
7695 @cindex octal escapes in strings
7696 Print using only seven-bit characters; if this option is set,
7697 @value{GDBN} displays any eight-bit characters (in strings or
7698 character values) using the notation @code{\}@var{nnn}. This setting is
7699 best if you are working in English (@sc{ascii}) and you use the
7700 high-order bit of characters as a marker or ``meta'' bit.
7702 @item set print sevenbit-strings off
7703 Print full eight-bit characters. This allows the use of more
7704 international character sets, and is the default.
7706 @item show print sevenbit-strings
7707 Show whether or not @value{GDBN} is printing only seven-bit characters.
7709 @item set print union on
7710 @cindex unions in structures, printing
7711 Tell @value{GDBN} to print unions which are contained in structures
7712 and other unions. This is the default setting.
7714 @item set print union off
7715 Tell @value{GDBN} not to print unions which are contained in
7716 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7719 @item show print union
7720 Ask @value{GDBN} whether or not it will print unions which are contained in
7721 structures and other unions.
7723 For example, given the declarations
7726 typedef enum @{Tree, Bug@} Species;
7727 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7728 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7739 struct thing foo = @{Tree, @{Acorn@}@};
7743 with @code{set print union on} in effect @samp{p foo} would print
7746 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7750 and with @code{set print union off} in effect it would print
7753 $1 = @{it = Tree, form = @{...@}@}
7757 @code{set print union} affects programs written in C-like languages
7763 These settings are of interest when debugging C@t{++} programs:
7766 @cindex demangling C@t{++} names
7767 @item set print demangle
7768 @itemx set print demangle on
7769 Print C@t{++} names in their source form rather than in the encoded
7770 (``mangled'') form passed to the assembler and linker for type-safe
7771 linkage. The default is on.
7773 @item show print demangle
7774 Show whether C@t{++} names are printed in mangled or demangled form.
7776 @item set print asm-demangle
7777 @itemx set print asm-demangle on
7778 Print C@t{++} names in their source form rather than their mangled form, even
7779 in assembler code printouts such as instruction disassemblies.
7782 @item show print asm-demangle
7783 Show whether C@t{++} names in assembly listings are printed in mangled
7786 @cindex C@t{++} symbol decoding style
7787 @cindex symbol decoding style, C@t{++}
7788 @kindex set demangle-style
7789 @item set demangle-style @var{style}
7790 Choose among several encoding schemes used by different compilers to
7791 represent C@t{++} names. The choices for @var{style} are currently:
7795 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7798 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7799 This is the default.
7802 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7805 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7808 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7809 @strong{Warning:} this setting alone is not sufficient to allow
7810 debugging @code{cfront}-generated executables. @value{GDBN} would
7811 require further enhancement to permit that.
7814 If you omit @var{style}, you will see a list of possible formats.
7816 @item show demangle-style
7817 Display the encoding style currently in use for decoding C@t{++} symbols.
7819 @item set print object
7820 @itemx set print object on
7821 @cindex derived type of an object, printing
7822 @cindex display derived types
7823 When displaying a pointer to an object, identify the @emph{actual}
7824 (derived) type of the object rather than the @emph{declared} type, using
7825 the virtual function table.
7827 @item set print object off
7828 Display only the declared type of objects, without reference to the
7829 virtual function table. This is the default setting.
7831 @item show print object
7832 Show whether actual, or declared, object types are displayed.
7834 @item set print static-members
7835 @itemx set print static-members on
7836 @cindex static members of C@t{++} objects
7837 Print static members when displaying a C@t{++} object. The default is on.
7839 @item set print static-members off
7840 Do not print static members when displaying a C@t{++} object.
7842 @item show print static-members
7843 Show whether C@t{++} static members are printed or not.
7845 @item set print pascal_static-members
7846 @itemx set print pascal_static-members on
7847 @cindex static members of Pascal objects
7848 @cindex Pascal objects, static members display
7849 Print static members when displaying a Pascal object. The default is on.
7851 @item set print pascal_static-members off
7852 Do not print static members when displaying a Pascal object.
7854 @item show print pascal_static-members
7855 Show whether Pascal static members are printed or not.
7857 @c These don't work with HP ANSI C++ yet.
7858 @item set print vtbl
7859 @itemx set print vtbl on
7860 @cindex pretty print C@t{++} virtual function tables
7861 @cindex virtual functions (C@t{++}) display
7862 @cindex VTBL display
7863 Pretty print C@t{++} virtual function tables. The default is off.
7864 (The @code{vtbl} commands do not work on programs compiled with the HP
7865 ANSI C@t{++} compiler (@code{aCC}).)
7867 @item set print vtbl off
7868 Do not pretty print C@t{++} virtual function tables.
7870 @item show print vtbl
7871 Show whether C@t{++} virtual function tables are pretty printed, or not.
7875 @section Value History
7877 @cindex value history
7878 @cindex history of values printed by @value{GDBN}
7879 Values printed by the @code{print} command are saved in the @value{GDBN}
7880 @dfn{value history}. This allows you to refer to them in other expressions.
7881 Values are kept until the symbol table is re-read or discarded
7882 (for example with the @code{file} or @code{symbol-file} commands).
7883 When the symbol table changes, the value history is discarded,
7884 since the values may contain pointers back to the types defined in the
7889 @cindex history number
7890 The values printed are given @dfn{history numbers} by which you can
7891 refer to them. These are successive integers starting with one.
7892 @code{print} shows you the history number assigned to a value by
7893 printing @samp{$@var{num} = } before the value; here @var{num} is the
7896 To refer to any previous value, use @samp{$} followed by the value's
7897 history number. The way @code{print} labels its output is designed to
7898 remind you of this. Just @code{$} refers to the most recent value in
7899 the history, and @code{$$} refers to the value before that.
7900 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7901 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7902 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7904 For example, suppose you have just printed a pointer to a structure and
7905 want to see the contents of the structure. It suffices to type
7911 If you have a chain of structures where the component @code{next} points
7912 to the next one, you can print the contents of the next one with this:
7919 You can print successive links in the chain by repeating this
7920 command---which you can do by just typing @key{RET}.
7922 Note that the history records values, not expressions. If the value of
7923 @code{x} is 4 and you type these commands:
7931 then the value recorded in the value history by the @code{print} command
7932 remains 4 even though the value of @code{x} has changed.
7937 Print the last ten values in the value history, with their item numbers.
7938 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7939 values} does not change the history.
7941 @item show values @var{n}
7942 Print ten history values centered on history item number @var{n}.
7945 Print ten history values just after the values last printed. If no more
7946 values are available, @code{show values +} produces no display.
7949 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7950 same effect as @samp{show values +}.
7952 @node Convenience Vars
7953 @section Convenience Variables
7955 @cindex convenience variables
7956 @cindex user-defined variables
7957 @value{GDBN} provides @dfn{convenience variables} that you can use within
7958 @value{GDBN} to hold on to a value and refer to it later. These variables
7959 exist entirely within @value{GDBN}; they are not part of your program, and
7960 setting a convenience variable has no direct effect on further execution
7961 of your program. That is why you can use them freely.
7963 Convenience variables are prefixed with @samp{$}. Any name preceded by
7964 @samp{$} can be used for a convenience variable, unless it is one of
7965 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7966 (Value history references, in contrast, are @emph{numbers} preceded
7967 by @samp{$}. @xref{Value History, ,Value History}.)
7969 You can save a value in a convenience variable with an assignment
7970 expression, just as you would set a variable in your program.
7974 set $foo = *object_ptr
7978 would save in @code{$foo} the value contained in the object pointed to by
7981 Using a convenience variable for the first time creates it, but its
7982 value is @code{void} until you assign a new value. You can alter the
7983 value with another assignment at any time.
7985 Convenience variables have no fixed types. You can assign a convenience
7986 variable any type of value, including structures and arrays, even if
7987 that variable already has a value of a different type. The convenience
7988 variable, when used as an expression, has the type of its current value.
7991 @kindex show convenience
7992 @cindex show all user variables
7993 @item show convenience
7994 Print a list of convenience variables used so far, and their values.
7995 Abbreviated @code{show conv}.
7997 @kindex init-if-undefined
7998 @cindex convenience variables, initializing
7999 @item init-if-undefined $@var{variable} = @var{expression}
8000 Set a convenience variable if it has not already been set. This is useful
8001 for user-defined commands that keep some state. It is similar, in concept,
8002 to using local static variables with initializers in C (except that
8003 convenience variables are global). It can also be used to allow users to
8004 override default values used in a command script.
8006 If the variable is already defined then the expression is not evaluated so
8007 any side-effects do not occur.
8010 One of the ways to use a convenience variable is as a counter to be
8011 incremented or a pointer to be advanced. For example, to print
8012 a field from successive elements of an array of structures:
8016 print bar[$i++]->contents
8020 Repeat that command by typing @key{RET}.
8022 Some convenience variables are created automatically by @value{GDBN} and given
8023 values likely to be useful.
8026 @vindex $_@r{, convenience variable}
8028 The variable @code{$_} is automatically set by the @code{x} command to
8029 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8030 commands which provide a default address for @code{x} to examine also
8031 set @code{$_} to that address; these commands include @code{info line}
8032 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8033 except when set by the @code{x} command, in which case it is a pointer
8034 to the type of @code{$__}.
8036 @vindex $__@r{, convenience variable}
8038 The variable @code{$__} is automatically set by the @code{x} command
8039 to the value found in the last address examined. Its type is chosen
8040 to match the format in which the data was printed.
8043 @vindex $_exitcode@r{, convenience variable}
8044 The variable @code{$_exitcode} is automatically set to the exit code when
8045 the program being debugged terminates.
8048 @vindex $_siginfo@r{, convenience variable}
8049 The variable @code{$_siginfo} contains extra signal information
8050 (@pxref{extra signal information}). Note that @code{$_siginfo}
8051 could be empty, if the application has not yet received any signals.
8052 For example, it will be empty before you execute the @code{run} command.
8055 On HP-UX systems, if you refer to a function or variable name that
8056 begins with a dollar sign, @value{GDBN} searches for a user or system
8057 name first, before it searches for a convenience variable.
8059 @cindex convenience functions
8060 @value{GDBN} also supplies some @dfn{convenience functions}. These
8061 have a syntax similar to convenience variables. A convenience
8062 function can be used in an expression just like an ordinary function;
8063 however, a convenience function is implemented internally to
8068 @kindex help function
8069 @cindex show all convenience functions
8070 Print a list of all convenience functions.
8077 You can refer to machine register contents, in expressions, as variables
8078 with names starting with @samp{$}. The names of registers are different
8079 for each machine; use @code{info registers} to see the names used on
8083 @kindex info registers
8084 @item info registers
8085 Print the names and values of all registers except floating-point
8086 and vector registers (in the selected stack frame).
8088 @kindex info all-registers
8089 @cindex floating point registers
8090 @item info all-registers
8091 Print the names and values of all registers, including floating-point
8092 and vector registers (in the selected stack frame).
8094 @item info registers @var{regname} @dots{}
8095 Print the @dfn{relativized} value of each specified register @var{regname}.
8096 As discussed in detail below, register values are normally relative to
8097 the selected stack frame. @var{regname} may be any register name valid on
8098 the machine you are using, with or without the initial @samp{$}.
8101 @cindex stack pointer register
8102 @cindex program counter register
8103 @cindex process status register
8104 @cindex frame pointer register
8105 @cindex standard registers
8106 @value{GDBN} has four ``standard'' register names that are available (in
8107 expressions) on most machines---whenever they do not conflict with an
8108 architecture's canonical mnemonics for registers. The register names
8109 @code{$pc} and @code{$sp} are used for the program counter register and
8110 the stack pointer. @code{$fp} is used for a register that contains a
8111 pointer to the current stack frame, and @code{$ps} is used for a
8112 register that contains the processor status. For example,
8113 you could print the program counter in hex with
8120 or print the instruction to be executed next with
8127 or add four to the stack pointer@footnote{This is a way of removing
8128 one word from the stack, on machines where stacks grow downward in
8129 memory (most machines, nowadays). This assumes that the innermost
8130 stack frame is selected; setting @code{$sp} is not allowed when other
8131 stack frames are selected. To pop entire frames off the stack,
8132 regardless of machine architecture, use @code{return};
8133 see @ref{Returning, ,Returning from a Function}.} with
8139 Whenever possible, these four standard register names are available on
8140 your machine even though the machine has different canonical mnemonics,
8141 so long as there is no conflict. The @code{info registers} command
8142 shows the canonical names. For example, on the SPARC, @code{info
8143 registers} displays the processor status register as @code{$psr} but you
8144 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8145 is an alias for the @sc{eflags} register.
8147 @value{GDBN} always considers the contents of an ordinary register as an
8148 integer when the register is examined in this way. Some machines have
8149 special registers which can hold nothing but floating point; these
8150 registers are considered to have floating point values. There is no way
8151 to refer to the contents of an ordinary register as floating point value
8152 (although you can @emph{print} it as a floating point value with
8153 @samp{print/f $@var{regname}}).
8155 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8156 means that the data format in which the register contents are saved by
8157 the operating system is not the same one that your program normally
8158 sees. For example, the registers of the 68881 floating point
8159 coprocessor are always saved in ``extended'' (raw) format, but all C
8160 programs expect to work with ``double'' (virtual) format. In such
8161 cases, @value{GDBN} normally works with the virtual format only (the format
8162 that makes sense for your program), but the @code{info registers} command
8163 prints the data in both formats.
8165 @cindex SSE registers (x86)
8166 @cindex MMX registers (x86)
8167 Some machines have special registers whose contents can be interpreted
8168 in several different ways. For example, modern x86-based machines
8169 have SSE and MMX registers that can hold several values packed
8170 together in several different formats. @value{GDBN} refers to such
8171 registers in @code{struct} notation:
8174 (@value{GDBP}) print $xmm1
8176 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8177 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8178 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8179 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8180 v4_int32 = @{0, 20657912, 11, 13@},
8181 v2_int64 = @{88725056443645952, 55834574859@},
8182 uint128 = 0x0000000d0000000b013b36f800000000
8187 To set values of such registers, you need to tell @value{GDBN} which
8188 view of the register you wish to change, as if you were assigning
8189 value to a @code{struct} member:
8192 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8195 Normally, register values are relative to the selected stack frame
8196 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8197 value that the register would contain if all stack frames farther in
8198 were exited and their saved registers restored. In order to see the
8199 true contents of hardware registers, you must select the innermost
8200 frame (with @samp{frame 0}).
8202 However, @value{GDBN} must deduce where registers are saved, from the machine
8203 code generated by your compiler. If some registers are not saved, or if
8204 @value{GDBN} is unable to locate the saved registers, the selected stack
8205 frame makes no difference.
8207 @node Floating Point Hardware
8208 @section Floating Point Hardware
8209 @cindex floating point
8211 Depending on the configuration, @value{GDBN} may be able to give
8212 you more information about the status of the floating point hardware.
8217 Display hardware-dependent information about the floating
8218 point unit. The exact contents and layout vary depending on the
8219 floating point chip. Currently, @samp{info float} is supported on
8220 the ARM and x86 machines.
8224 @section Vector Unit
8227 Depending on the configuration, @value{GDBN} may be able to give you
8228 more information about the status of the vector unit.
8233 Display information about the vector unit. The exact contents and
8234 layout vary depending on the hardware.
8237 @node OS Information
8238 @section Operating System Auxiliary Information
8239 @cindex OS information
8241 @value{GDBN} provides interfaces to useful OS facilities that can help
8242 you debug your program.
8244 @cindex @code{ptrace} system call
8245 @cindex @code{struct user} contents
8246 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8247 machines), it interfaces with the inferior via the @code{ptrace}
8248 system call. The operating system creates a special sata structure,
8249 called @code{struct user}, for this interface. You can use the
8250 command @code{info udot} to display the contents of this data
8256 Display the contents of the @code{struct user} maintained by the OS
8257 kernel for the program being debugged. @value{GDBN} displays the
8258 contents of @code{struct user} as a list of hex numbers, similar to
8259 the @code{examine} command.
8262 @cindex auxiliary vector
8263 @cindex vector, auxiliary
8264 Some operating systems supply an @dfn{auxiliary vector} to programs at
8265 startup. This is akin to the arguments and environment that you
8266 specify for a program, but contains a system-dependent variety of
8267 binary values that tell system libraries important details about the
8268 hardware, operating system, and process. Each value's purpose is
8269 identified by an integer tag; the meanings are well-known but system-specific.
8270 Depending on the configuration and operating system facilities,
8271 @value{GDBN} may be able to show you this information. For remote
8272 targets, this functionality may further depend on the remote stub's
8273 support of the @samp{qXfer:auxv:read} packet, see
8274 @ref{qXfer auxiliary vector read}.
8279 Display the auxiliary vector of the inferior, which can be either a
8280 live process or a core dump file. @value{GDBN} prints each tag value
8281 numerically, and also shows names and text descriptions for recognized
8282 tags. Some values in the vector are numbers, some bit masks, and some
8283 pointers to strings or other data. @value{GDBN} displays each value in the
8284 most appropriate form for a recognized tag, and in hexadecimal for
8285 an unrecognized tag.
8288 On some targets, @value{GDBN} can access operating-system-specific information
8289 and display it to user, without interpretation. For remote targets,
8290 this functionality depends on the remote stub's support of the
8291 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8294 @kindex info os processes
8295 @item info os processes
8296 Display the list of processes on the target. For each process,
8297 @value{GDBN} prints the process identifier, the name of the user, and
8298 the command corresponding to the process.
8301 @node Memory Region Attributes
8302 @section Memory Region Attributes
8303 @cindex memory region attributes
8305 @dfn{Memory region attributes} allow you to describe special handling
8306 required by regions of your target's memory. @value{GDBN} uses
8307 attributes to determine whether to allow certain types of memory
8308 accesses; whether to use specific width accesses; and whether to cache
8309 target memory. By default the description of memory regions is
8310 fetched from the target (if the current target supports this), but the
8311 user can override the fetched regions.
8313 Defined memory regions can be individually enabled and disabled. When a
8314 memory region is disabled, @value{GDBN} uses the default attributes when
8315 accessing memory in that region. Similarly, if no memory regions have
8316 been defined, @value{GDBN} uses the default attributes when accessing
8319 When a memory region is defined, it is given a number to identify it;
8320 to enable, disable, or remove a memory region, you specify that number.
8324 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8325 Define a memory region bounded by @var{lower} and @var{upper} with
8326 attributes @var{attributes}@dots{}, and add it to the list of regions
8327 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8328 case: it is treated as the target's maximum memory address.
8329 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8332 Discard any user changes to the memory regions and use target-supplied
8333 regions, if available, or no regions if the target does not support.
8336 @item delete mem @var{nums}@dots{}
8337 Remove memory regions @var{nums}@dots{} from the list of regions
8338 monitored by @value{GDBN}.
8341 @item disable mem @var{nums}@dots{}
8342 Disable monitoring of memory regions @var{nums}@dots{}.
8343 A disabled memory region is not forgotten.
8344 It may be enabled again later.
8347 @item enable mem @var{nums}@dots{}
8348 Enable monitoring of memory regions @var{nums}@dots{}.
8352 Print a table of all defined memory regions, with the following columns
8356 @item Memory Region Number
8357 @item Enabled or Disabled.
8358 Enabled memory regions are marked with @samp{y}.
8359 Disabled memory regions are marked with @samp{n}.
8362 The address defining the inclusive lower bound of the memory region.
8365 The address defining the exclusive upper bound of the memory region.
8368 The list of attributes set for this memory region.
8373 @subsection Attributes
8375 @subsubsection Memory Access Mode
8376 The access mode attributes set whether @value{GDBN} may make read or
8377 write accesses to a memory region.
8379 While these attributes prevent @value{GDBN} from performing invalid
8380 memory accesses, they do nothing to prevent the target system, I/O DMA,
8381 etc.@: from accessing memory.
8385 Memory is read only.
8387 Memory is write only.
8389 Memory is read/write. This is the default.
8392 @subsubsection Memory Access Size
8393 The access size attribute tells @value{GDBN} to use specific sized
8394 accesses in the memory region. Often memory mapped device registers
8395 require specific sized accesses. If no access size attribute is
8396 specified, @value{GDBN} may use accesses of any size.
8400 Use 8 bit memory accesses.
8402 Use 16 bit memory accesses.
8404 Use 32 bit memory accesses.
8406 Use 64 bit memory accesses.
8409 @c @subsubsection Hardware/Software Breakpoints
8410 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8411 @c will use hardware or software breakpoints for the internal breakpoints
8412 @c used by the step, next, finish, until, etc. commands.
8416 @c Always use hardware breakpoints
8417 @c @item swbreak (default)
8420 @subsubsection Data Cache
8421 The data cache attributes set whether @value{GDBN} will cache target
8422 memory. While this generally improves performance by reducing debug
8423 protocol overhead, it can lead to incorrect results because @value{GDBN}
8424 does not know about volatile variables or memory mapped device
8429 Enable @value{GDBN} to cache target memory.
8431 Disable @value{GDBN} from caching target memory. This is the default.
8434 @subsection Memory Access Checking
8435 @value{GDBN} can be instructed to refuse accesses to memory that is
8436 not explicitly described. This can be useful if accessing such
8437 regions has undesired effects for a specific target, or to provide
8438 better error checking. The following commands control this behaviour.
8441 @kindex set mem inaccessible-by-default
8442 @item set mem inaccessible-by-default [on|off]
8443 If @code{on} is specified, make @value{GDBN} treat memory not
8444 explicitly described by the memory ranges as non-existent and refuse accesses
8445 to such memory. The checks are only performed if there's at least one
8446 memory range defined. If @code{off} is specified, make @value{GDBN}
8447 treat the memory not explicitly described by the memory ranges as RAM.
8448 The default value is @code{on}.
8449 @kindex show mem inaccessible-by-default
8450 @item show mem inaccessible-by-default
8451 Show the current handling of accesses to unknown memory.
8455 @c @subsubsection Memory Write Verification
8456 @c The memory write verification attributes set whether @value{GDBN}
8457 @c will re-reads data after each write to verify the write was successful.
8461 @c @item noverify (default)
8464 @node Dump/Restore Files
8465 @section Copy Between Memory and a File
8466 @cindex dump/restore files
8467 @cindex append data to a file
8468 @cindex dump data to a file
8469 @cindex restore data from a file
8471 You can use the commands @code{dump}, @code{append}, and
8472 @code{restore} to copy data between target memory and a file. The
8473 @code{dump} and @code{append} commands write data to a file, and the
8474 @code{restore} command reads data from a file back into the inferior's
8475 memory. Files may be in binary, Motorola S-record, Intel hex, or
8476 Tektronix Hex format; however, @value{GDBN} can only append to binary
8482 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8483 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8484 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8485 or the value of @var{expr}, to @var{filename} in the given format.
8487 The @var{format} parameter may be any one of:
8494 Motorola S-record format.
8496 Tektronix Hex format.
8499 @value{GDBN} uses the same definitions of these formats as the
8500 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8501 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8505 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8506 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8507 Append the contents of memory from @var{start_addr} to @var{end_addr},
8508 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8509 (@value{GDBN} can only append data to files in raw binary form.)
8512 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8513 Restore the contents of file @var{filename} into memory. The
8514 @code{restore} command can automatically recognize any known @sc{bfd}
8515 file format, except for raw binary. To restore a raw binary file you
8516 must specify the optional keyword @code{binary} after the filename.
8518 If @var{bias} is non-zero, its value will be added to the addresses
8519 contained in the file. Binary files always start at address zero, so
8520 they will be restored at address @var{bias}. Other bfd files have
8521 a built-in location; they will be restored at offset @var{bias}
8524 If @var{start} and/or @var{end} are non-zero, then only data between
8525 file offset @var{start} and file offset @var{end} will be restored.
8526 These offsets are relative to the addresses in the file, before
8527 the @var{bias} argument is applied.
8531 @node Core File Generation
8532 @section How to Produce a Core File from Your Program
8533 @cindex dump core from inferior
8535 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8536 image of a running process and its process status (register values
8537 etc.). Its primary use is post-mortem debugging of a program that
8538 crashed while it ran outside a debugger. A program that crashes
8539 automatically produces a core file, unless this feature is disabled by
8540 the user. @xref{Files}, for information on invoking @value{GDBN} in
8541 the post-mortem debugging mode.
8543 Occasionally, you may wish to produce a core file of the program you
8544 are debugging in order to preserve a snapshot of its state.
8545 @value{GDBN} has a special command for that.
8549 @kindex generate-core-file
8550 @item generate-core-file [@var{file}]
8551 @itemx gcore [@var{file}]
8552 Produce a core dump of the inferior process. The optional argument
8553 @var{file} specifies the file name where to put the core dump. If not
8554 specified, the file name defaults to @file{core.@var{pid}}, where
8555 @var{pid} is the inferior process ID.
8557 Note that this command is implemented only for some systems (as of
8558 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8561 @node Character Sets
8562 @section Character Sets
8563 @cindex character sets
8565 @cindex translating between character sets
8566 @cindex host character set
8567 @cindex target character set
8569 If the program you are debugging uses a different character set to
8570 represent characters and strings than the one @value{GDBN} uses itself,
8571 @value{GDBN} can automatically translate between the character sets for
8572 you. The character set @value{GDBN} uses we call the @dfn{host
8573 character set}; the one the inferior program uses we call the
8574 @dfn{target character set}.
8576 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8577 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8578 remote protocol (@pxref{Remote Debugging}) to debug a program
8579 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8580 then the host character set is Latin-1, and the target character set is
8581 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8582 target-charset EBCDIC-US}, then @value{GDBN} translates between
8583 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8584 character and string literals in expressions.
8586 @value{GDBN} has no way to automatically recognize which character set
8587 the inferior program uses; you must tell it, using the @code{set
8588 target-charset} command, described below.
8590 Here are the commands for controlling @value{GDBN}'s character set
8594 @item set target-charset @var{charset}
8595 @kindex set target-charset
8596 Set the current target character set to @var{charset}. To display the
8597 list of supported target character sets, type
8598 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8600 @item set host-charset @var{charset}
8601 @kindex set host-charset
8602 Set the current host character set to @var{charset}.
8604 By default, @value{GDBN} uses a host character set appropriate to the
8605 system it is running on; you can override that default using the
8606 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8607 automatically determine the appropriate host character set. In this
8608 case, @value{GDBN} uses @samp{UTF-8}.
8610 @value{GDBN} can only use certain character sets as its host character
8611 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8612 @value{GDBN} will list the host character sets it supports.
8614 @item set charset @var{charset}
8616 Set the current host and target character sets to @var{charset}. As
8617 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8618 @value{GDBN} will list the names of the character sets that can be used
8619 for both host and target.
8622 @kindex show charset
8623 Show the names of the current host and target character sets.
8625 @item show host-charset
8626 @kindex show host-charset
8627 Show the name of the current host character set.
8629 @item show target-charset
8630 @kindex show target-charset
8631 Show the name of the current target character set.
8633 @item set target-wide-charset @var{charset}
8634 @kindex set target-wide-charset
8635 Set the current target's wide character set to @var{charset}. This is
8636 the character set used by the target's @code{wchar_t} type. To
8637 display the list of supported wide character sets, type
8638 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8640 @item show target-wide-charset
8641 @kindex show target-wide-charset
8642 Show the name of the current target's wide character set.
8645 Here is an example of @value{GDBN}'s character set support in action.
8646 Assume that the following source code has been placed in the file
8647 @file{charset-test.c}:
8653 = @{72, 101, 108, 108, 111, 44, 32, 119,
8654 111, 114, 108, 100, 33, 10, 0@};
8655 char ibm1047_hello[]
8656 = @{200, 133, 147, 147, 150, 107, 64, 166,
8657 150, 153, 147, 132, 90, 37, 0@};
8661 printf ("Hello, world!\n");
8665 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8666 containing the string @samp{Hello, world!} followed by a newline,
8667 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8669 We compile the program, and invoke the debugger on it:
8672 $ gcc -g charset-test.c -o charset-test
8673 $ gdb -nw charset-test
8674 GNU gdb 2001-12-19-cvs
8675 Copyright 2001 Free Software Foundation, Inc.
8680 We can use the @code{show charset} command to see what character sets
8681 @value{GDBN} is currently using to interpret and display characters and
8685 (@value{GDBP}) show charset
8686 The current host and target character set is `ISO-8859-1'.
8690 For the sake of printing this manual, let's use @sc{ascii} as our
8691 initial character set:
8693 (@value{GDBP}) set charset ASCII
8694 (@value{GDBP}) show charset
8695 The current host and target character set is `ASCII'.
8699 Let's assume that @sc{ascii} is indeed the correct character set for our
8700 host system --- in other words, let's assume that if @value{GDBN} prints
8701 characters using the @sc{ascii} character set, our terminal will display
8702 them properly. Since our current target character set is also
8703 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8706 (@value{GDBP}) print ascii_hello
8707 $1 = 0x401698 "Hello, world!\n"
8708 (@value{GDBP}) print ascii_hello[0]
8713 @value{GDBN} uses the target character set for character and string
8714 literals you use in expressions:
8717 (@value{GDBP}) print '+'
8722 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8725 @value{GDBN} relies on the user to tell it which character set the
8726 target program uses. If we print @code{ibm1047_hello} while our target
8727 character set is still @sc{ascii}, we get jibberish:
8730 (@value{GDBP}) print ibm1047_hello
8731 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8732 (@value{GDBP}) print ibm1047_hello[0]
8737 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8738 @value{GDBN} tells us the character sets it supports:
8741 (@value{GDBP}) set target-charset
8742 ASCII EBCDIC-US IBM1047 ISO-8859-1
8743 (@value{GDBP}) set target-charset
8746 We can select @sc{ibm1047} as our target character set, and examine the
8747 program's strings again. Now the @sc{ascii} string is wrong, but
8748 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8749 target character set, @sc{ibm1047}, to the host character set,
8750 @sc{ascii}, and they display correctly:
8753 (@value{GDBP}) set target-charset IBM1047
8754 (@value{GDBP}) show charset
8755 The current host character set is `ASCII'.
8756 The current target character set is `IBM1047'.
8757 (@value{GDBP}) print ascii_hello
8758 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8759 (@value{GDBP}) print ascii_hello[0]
8761 (@value{GDBP}) print ibm1047_hello
8762 $8 = 0x4016a8 "Hello, world!\n"
8763 (@value{GDBP}) print ibm1047_hello[0]
8768 As above, @value{GDBN} uses the target character set for character and
8769 string literals you use in expressions:
8772 (@value{GDBP}) print '+'
8777 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8780 @node Caching Remote Data
8781 @section Caching Data of Remote Targets
8782 @cindex caching data of remote targets
8784 @value{GDBN} caches data exchanged between the debugger and a
8785 remote target (@pxref{Remote Debugging}). Such caching generally improves
8786 performance, because it reduces the overhead of the remote protocol by
8787 bundling memory reads and writes into large chunks. Unfortunately, simply
8788 caching everything would lead to incorrect results, since @value{GDBN}
8789 does not necessarily know anything about volatile values, memory-mapped I/O
8790 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8791 memory can be changed @emph{while} a gdb command is executing.
8792 Therefore, by default, @value{GDBN} only caches data
8793 known to be on the stack@footnote{In non-stop mode, it is moderately
8794 rare for a running thread to modify the stack of a stopped thread
8795 in a way that would interfere with a backtrace, and caching of
8796 stack reads provides a significant speed up of remote backtraces.}.
8797 Other regions of memory can be explicitly marked as
8798 cacheable; see @pxref{Memory Region Attributes}.
8801 @kindex set remotecache
8802 @item set remotecache on
8803 @itemx set remotecache off
8804 This option no longer does anything; it exists for compatibility
8807 @kindex show remotecache
8808 @item show remotecache
8809 Show the current state of the obsolete remotecache flag.
8811 @kindex set stack-cache
8812 @item set stack-cache on
8813 @itemx set stack-cache off
8814 Enable or disable caching of stack accesses. When @code{ON}, use
8815 caching. By default, this option is @code{ON}.
8817 @kindex show stack-cache
8818 @item show stack-cache
8819 Show the current state of data caching for memory accesses.
8822 @item info dcache @r{[}line@r{]}
8823 Print the information about the data cache performance. The
8824 information displayed includes the dcache width and depth, and for
8825 each cache line, its number, address, and how many times it was
8826 referenced. This command is useful for debugging the data cache
8829 If a line number is specified, the contents of that line will be
8833 @node Searching Memory
8834 @section Search Memory
8835 @cindex searching memory
8837 Memory can be searched for a particular sequence of bytes with the
8838 @code{find} command.
8842 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8843 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8844 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8845 etc. The search begins at address @var{start_addr} and continues for either
8846 @var{len} bytes or through to @var{end_addr} inclusive.
8849 @var{s} and @var{n} are optional parameters.
8850 They may be specified in either order, apart or together.
8853 @item @var{s}, search query size
8854 The size of each search query value.
8860 halfwords (two bytes)
8864 giant words (eight bytes)
8867 All values are interpreted in the current language.
8868 This means, for example, that if the current source language is C/C@t{++}
8869 then searching for the string ``hello'' includes the trailing '\0'.
8871 If the value size is not specified, it is taken from the
8872 value's type in the current language.
8873 This is useful when one wants to specify the search
8874 pattern as a mixture of types.
8875 Note that this means, for example, that in the case of C-like languages
8876 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8877 which is typically four bytes.
8879 @item @var{n}, maximum number of finds
8880 The maximum number of matches to print. The default is to print all finds.
8883 You can use strings as search values. Quote them with double-quotes
8885 The string value is copied into the search pattern byte by byte,
8886 regardless of the endianness of the target and the size specification.
8888 The address of each match found is printed as well as a count of the
8889 number of matches found.
8891 The address of the last value found is stored in convenience variable
8893 A count of the number of matches is stored in @samp{$numfound}.
8895 For example, if stopped at the @code{printf} in this function:
8901 static char hello[] = "hello-hello";
8902 static struct @{ char c; short s; int i; @}
8903 __attribute__ ((packed)) mixed
8904 = @{ 'c', 0x1234, 0x87654321 @};
8905 printf ("%s\n", hello);
8910 you get during debugging:
8913 (gdb) find &hello[0], +sizeof(hello), "hello"
8914 0x804956d <hello.1620+6>
8916 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8917 0x8049567 <hello.1620>
8918 0x804956d <hello.1620+6>
8920 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8921 0x8049567 <hello.1620>
8923 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8924 0x8049560 <mixed.1625>
8926 (gdb) print $numfound
8929 $2 = (void *) 0x8049560
8932 @node Optimized Code
8933 @chapter Debugging Optimized Code
8934 @cindex optimized code, debugging
8935 @cindex debugging optimized code
8937 Almost all compilers support optimization. With optimization
8938 disabled, the compiler generates assembly code that corresponds
8939 directly to your source code, in a simplistic way. As the compiler
8940 applies more powerful optimizations, the generated assembly code
8941 diverges from your original source code. With help from debugging
8942 information generated by the compiler, @value{GDBN} can map from
8943 the running program back to constructs from your original source.
8945 @value{GDBN} is more accurate with optimization disabled. If you
8946 can recompile without optimization, it is easier to follow the
8947 progress of your program during debugging. But, there are many cases
8948 where you may need to debug an optimized version.
8950 When you debug a program compiled with @samp{-g -O}, remember that the
8951 optimizer has rearranged your code; the debugger shows you what is
8952 really there. Do not be too surprised when the execution path does not
8953 exactly match your source file! An extreme example: if you define a
8954 variable, but never use it, @value{GDBN} never sees that
8955 variable---because the compiler optimizes it out of existence.
8957 Some things do not work as well with @samp{-g -O} as with just
8958 @samp{-g}, particularly on machines with instruction scheduling. If in
8959 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8960 please report it to us as a bug (including a test case!).
8961 @xref{Variables}, for more information about debugging optimized code.
8964 * Inline Functions:: How @value{GDBN} presents inlining
8967 @node Inline Functions
8968 @section Inline Functions
8969 @cindex inline functions, debugging
8971 @dfn{Inlining} is an optimization that inserts a copy of the function
8972 body directly at each call site, instead of jumping to a shared
8973 routine. @value{GDBN} displays inlined functions just like
8974 non-inlined functions. They appear in backtraces. You can view their
8975 arguments and local variables, step into them with @code{step}, skip
8976 them with @code{next}, and escape from them with @code{finish}.
8977 You can check whether a function was inlined by using the
8978 @code{info frame} command.
8980 For @value{GDBN} to support inlined functions, the compiler must
8981 record information about inlining in the debug information ---
8982 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8983 other compilers do also. @value{GDBN} only supports inlined functions
8984 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8985 do not emit two required attributes (@samp{DW_AT_call_file} and
8986 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8987 function calls with earlier versions of @value{NGCC}. It instead
8988 displays the arguments and local variables of inlined functions as
8989 local variables in the caller.
8991 The body of an inlined function is directly included at its call site;
8992 unlike a non-inlined function, there are no instructions devoted to
8993 the call. @value{GDBN} still pretends that the call site and the
8994 start of the inlined function are different instructions. Stepping to
8995 the call site shows the call site, and then stepping again shows
8996 the first line of the inlined function, even though no additional
8997 instructions are executed.
8999 This makes source-level debugging much clearer; you can see both the
9000 context of the call and then the effect of the call. Only stepping by
9001 a single instruction using @code{stepi} or @code{nexti} does not do
9002 this; single instruction steps always show the inlined body.
9004 There are some ways that @value{GDBN} does not pretend that inlined
9005 function calls are the same as normal calls:
9009 You cannot set breakpoints on inlined functions. @value{GDBN}
9010 either reports that there is no symbol with that name, or else sets the
9011 breakpoint only on non-inlined copies of the function. This limitation
9012 will be removed in a future version of @value{GDBN}; until then,
9013 set a breakpoint by line number on the first line of the inlined
9017 Setting breakpoints at the call site of an inlined function may not
9018 work, because the call site does not contain any code. @value{GDBN}
9019 may incorrectly move the breakpoint to the next line of the enclosing
9020 function, after the call. This limitation will be removed in a future
9021 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9022 or inside the inlined function instead.
9025 @value{GDBN} cannot locate the return value of inlined calls after
9026 using the @code{finish} command. This is a limitation of compiler-generated
9027 debugging information; after @code{finish}, you can step to the next line
9028 and print a variable where your program stored the return value.
9034 @chapter C Preprocessor Macros
9036 Some languages, such as C and C@t{++}, provide a way to define and invoke
9037 ``preprocessor macros'' which expand into strings of tokens.
9038 @value{GDBN} can evaluate expressions containing macro invocations, show
9039 the result of macro expansion, and show a macro's definition, including
9040 where it was defined.
9042 You may need to compile your program specially to provide @value{GDBN}
9043 with information about preprocessor macros. Most compilers do not
9044 include macros in their debugging information, even when you compile
9045 with the @option{-g} flag. @xref{Compilation}.
9047 A program may define a macro at one point, remove that definition later,
9048 and then provide a different definition after that. Thus, at different
9049 points in the program, a macro may have different definitions, or have
9050 no definition at all. If there is a current stack frame, @value{GDBN}
9051 uses the macros in scope at that frame's source code line. Otherwise,
9052 @value{GDBN} uses the macros in scope at the current listing location;
9055 Whenever @value{GDBN} evaluates an expression, it always expands any
9056 macro invocations present in the expression. @value{GDBN} also provides
9057 the following commands for working with macros explicitly.
9061 @kindex macro expand
9062 @cindex macro expansion, showing the results of preprocessor
9063 @cindex preprocessor macro expansion, showing the results of
9064 @cindex expanding preprocessor macros
9065 @item macro expand @var{expression}
9066 @itemx macro exp @var{expression}
9067 Show the results of expanding all preprocessor macro invocations in
9068 @var{expression}. Since @value{GDBN} simply expands macros, but does
9069 not parse the result, @var{expression} need not be a valid expression;
9070 it can be any string of tokens.
9073 @item macro expand-once @var{expression}
9074 @itemx macro exp1 @var{expression}
9075 @cindex expand macro once
9076 @i{(This command is not yet implemented.)} Show the results of
9077 expanding those preprocessor macro invocations that appear explicitly in
9078 @var{expression}. Macro invocations appearing in that expansion are
9079 left unchanged. This command allows you to see the effect of a
9080 particular macro more clearly, without being confused by further
9081 expansions. Since @value{GDBN} simply expands macros, but does not
9082 parse the result, @var{expression} need not be a valid expression; it
9083 can be any string of tokens.
9086 @cindex macro definition, showing
9087 @cindex definition, showing a macro's
9088 @item info macro @var{macro}
9089 Show the definition of the macro named @var{macro}, and describe the
9090 source location or compiler command-line where that definition was established.
9092 @kindex macro define
9093 @cindex user-defined macros
9094 @cindex defining macros interactively
9095 @cindex macros, user-defined
9096 @item macro define @var{macro} @var{replacement-list}
9097 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9098 Introduce a definition for a preprocessor macro named @var{macro},
9099 invocations of which are replaced by the tokens given in
9100 @var{replacement-list}. The first form of this command defines an
9101 ``object-like'' macro, which takes no arguments; the second form
9102 defines a ``function-like'' macro, which takes the arguments given in
9105 A definition introduced by this command is in scope in every
9106 expression evaluated in @value{GDBN}, until it is removed with the
9107 @code{macro undef} command, described below. The definition overrides
9108 all definitions for @var{macro} present in the program being debugged,
9109 as well as any previous user-supplied definition.
9112 @item macro undef @var{macro}
9113 Remove any user-supplied definition for the macro named @var{macro}.
9114 This command only affects definitions provided with the @code{macro
9115 define} command, described above; it cannot remove definitions present
9116 in the program being debugged.
9120 List all the macros defined using the @code{macro define} command.
9123 @cindex macros, example of debugging with
9124 Here is a transcript showing the above commands in action. First, we
9125 show our source files:
9133 #define ADD(x) (M + x)
9138 printf ("Hello, world!\n");
9140 printf ("We're so creative.\n");
9142 printf ("Goodbye, world!\n");
9149 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9150 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9151 compiler includes information about preprocessor macros in the debugging
9155 $ gcc -gdwarf-2 -g3 sample.c -o sample
9159 Now, we start @value{GDBN} on our sample program:
9163 GNU gdb 2002-05-06-cvs
9164 Copyright 2002 Free Software Foundation, Inc.
9165 GDB is free software, @dots{}
9169 We can expand macros and examine their definitions, even when the
9170 program is not running. @value{GDBN} uses the current listing position
9171 to decide which macro definitions are in scope:
9174 (@value{GDBP}) list main
9177 5 #define ADD(x) (M + x)
9182 10 printf ("Hello, world!\n");
9184 12 printf ("We're so creative.\n");
9185 (@value{GDBP}) info macro ADD
9186 Defined at /home/jimb/gdb/macros/play/sample.c:5
9187 #define ADD(x) (M + x)
9188 (@value{GDBP}) info macro Q
9189 Defined at /home/jimb/gdb/macros/play/sample.h:1
9190 included at /home/jimb/gdb/macros/play/sample.c:2
9192 (@value{GDBP}) macro expand ADD(1)
9193 expands to: (42 + 1)
9194 (@value{GDBP}) macro expand-once ADD(1)
9195 expands to: once (M + 1)
9199 In the example above, note that @code{macro expand-once} expands only
9200 the macro invocation explicit in the original text --- the invocation of
9201 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9202 which was introduced by @code{ADD}.
9204 Once the program is running, @value{GDBN} uses the macro definitions in
9205 force at the source line of the current stack frame:
9208 (@value{GDBP}) break main
9209 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9211 Starting program: /home/jimb/gdb/macros/play/sample
9213 Breakpoint 1, main () at sample.c:10
9214 10 printf ("Hello, world!\n");
9218 At line 10, the definition of the macro @code{N} at line 9 is in force:
9221 (@value{GDBP}) info macro N
9222 Defined at /home/jimb/gdb/macros/play/sample.c:9
9224 (@value{GDBP}) macro expand N Q M
9226 (@value{GDBP}) print N Q M
9231 As we step over directives that remove @code{N}'s definition, and then
9232 give it a new definition, @value{GDBN} finds the definition (or lack
9233 thereof) in force at each point:
9238 12 printf ("We're so creative.\n");
9239 (@value{GDBP}) info macro N
9240 The symbol `N' has no definition as a C/C++ preprocessor macro
9241 at /home/jimb/gdb/macros/play/sample.c:12
9244 14 printf ("Goodbye, world!\n");
9245 (@value{GDBP}) info macro N
9246 Defined at /home/jimb/gdb/macros/play/sample.c:13
9248 (@value{GDBP}) macro expand N Q M
9249 expands to: 1729 < 42
9250 (@value{GDBP}) print N Q M
9255 In addition to source files, macros can be defined on the compilation command
9256 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9257 such a way, @value{GDBN} displays the location of their definition as line zero
9258 of the source file submitted to the compiler.
9261 (@value{GDBP}) info macro __STDC__
9262 Defined at /home/jimb/gdb/macros/play/sample.c:0
9269 @chapter Tracepoints
9270 @c This chapter is based on the documentation written by Michael
9271 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9274 In some applications, it is not feasible for the debugger to interrupt
9275 the program's execution long enough for the developer to learn
9276 anything helpful about its behavior. If the program's correctness
9277 depends on its real-time behavior, delays introduced by a debugger
9278 might cause the program to change its behavior drastically, or perhaps
9279 fail, even when the code itself is correct. It is useful to be able
9280 to observe the program's behavior without interrupting it.
9282 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9283 specify locations in the program, called @dfn{tracepoints}, and
9284 arbitrary expressions to evaluate when those tracepoints are reached.
9285 Later, using the @code{tfind} command, you can examine the values
9286 those expressions had when the program hit the tracepoints. The
9287 expressions may also denote objects in memory---structures or arrays,
9288 for example---whose values @value{GDBN} should record; while visiting
9289 a particular tracepoint, you may inspect those objects as if they were
9290 in memory at that moment. However, because @value{GDBN} records these
9291 values without interacting with you, it can do so quickly and
9292 unobtrusively, hopefully not disturbing the program's behavior.
9294 The tracepoint facility is currently available only for remote
9295 targets. @xref{Targets}. In addition, your remote target must know
9296 how to collect trace data. This functionality is implemented in the
9297 remote stub; however, none of the stubs distributed with @value{GDBN}
9298 support tracepoints as of this writing. The format of the remote
9299 packets used to implement tracepoints are described in @ref{Tracepoint
9302 It is also possible to get trace data from a file, in a manner reminiscent
9303 of corefiles; you specify the filename, and use @code{tfind} to search
9304 through the file. @xref{Trace Files}, for more details.
9306 This chapter describes the tracepoint commands and features.
9310 * Analyze Collected Data::
9311 * Tracepoint Variables::
9315 @node Set Tracepoints
9316 @section Commands to Set Tracepoints
9318 Before running such a @dfn{trace experiment}, an arbitrary number of
9319 tracepoints can be set. A tracepoint is actually a special type of
9320 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9321 standard breakpoint commands. For instance, as with breakpoints,
9322 tracepoint numbers are successive integers starting from one, and many
9323 of the commands associated with tracepoints take the tracepoint number
9324 as their argument, to identify which tracepoint to work on.
9326 For each tracepoint, you can specify, in advance, some arbitrary set
9327 of data that you want the target to collect in the trace buffer when
9328 it hits that tracepoint. The collected data can include registers,
9329 local variables, or global data. Later, you can use @value{GDBN}
9330 commands to examine the values these data had at the time the
9333 Tracepoints do not support every breakpoint feature. Conditional
9334 expressions and ignore counts on tracepoints have no effect, and
9335 tracepoints cannot run @value{GDBN} commands when they are
9336 hit. Tracepoints may not be thread-specific either.
9338 @cindex fast tracepoints
9339 Some targets may support @dfn{fast tracepoints}, which are inserted in
9340 a different way (such as with a jump instead of a trap), that is
9341 faster but possibly restricted in where they may be installed.
9343 This section describes commands to set tracepoints and associated
9344 conditions and actions.
9347 * Create and Delete Tracepoints::
9348 * Enable and Disable Tracepoints::
9349 * Tracepoint Passcounts::
9350 * Tracepoint Conditions::
9351 * Trace State Variables::
9352 * Tracepoint Actions::
9353 * Listing Tracepoints::
9354 * Starting and Stopping Trace Experiments::
9355 * Tracepoint Restrictions::
9358 @node Create and Delete Tracepoints
9359 @subsection Create and Delete Tracepoints
9362 @cindex set tracepoint
9364 @item trace @var{location}
9365 The @code{trace} command is very similar to the @code{break} command.
9366 Its argument @var{location} can be a source line, a function name, or
9367 an address in the target program. @xref{Specify Location}. The
9368 @code{trace} command defines a tracepoint, which is a point in the
9369 target program where the debugger will briefly stop, collect some
9370 data, and then allow the program to continue. Setting a tracepoint or
9371 changing its actions doesn't take effect until the next @code{tstart}
9372 command, and once a trace experiment is running, further changes will
9373 not have any effect until the next trace experiment starts.
9375 Here are some examples of using the @code{trace} command:
9378 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9380 (@value{GDBP}) @b{trace +2} // 2 lines forward
9382 (@value{GDBP}) @b{trace my_function} // first source line of function
9384 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9386 (@value{GDBP}) @b{trace *0x2117c4} // an address
9390 You can abbreviate @code{trace} as @code{tr}.
9392 @item trace @var{location} if @var{cond}
9393 Set a tracepoint with condition @var{cond}; evaluate the expression
9394 @var{cond} each time the tracepoint is reached, and collect data only
9395 if the value is nonzero---that is, if @var{cond} evaluates as true.
9396 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9397 information on tracepoint conditions.
9399 @item ftrace @var{location} [ if @var{cond} ]
9400 @cindex set fast tracepoint
9402 The @code{ftrace} command sets a fast tracepoint. For targets that
9403 support them, fast tracepoints will use a more efficient but possibly
9404 less general technique to trigger data collection, such as a jump
9405 instruction instead of a trap, or some sort of hardware support. It
9406 may not be possible to create a fast tracepoint at the desired
9407 location, in which case the command will exit with an explanatory
9410 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9414 @cindex last tracepoint number
9415 @cindex recent tracepoint number
9416 @cindex tracepoint number
9417 The convenience variable @code{$tpnum} records the tracepoint number
9418 of the most recently set tracepoint.
9420 @kindex delete tracepoint
9421 @cindex tracepoint deletion
9422 @item delete tracepoint @r{[}@var{num}@r{]}
9423 Permanently delete one or more tracepoints. With no argument, the
9424 default is to delete all tracepoints. Note that the regular
9425 @code{delete} command can remove tracepoints also.
9430 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9432 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9436 You can abbreviate this command as @code{del tr}.
9439 @node Enable and Disable Tracepoints
9440 @subsection Enable and Disable Tracepoints
9442 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9445 @kindex disable tracepoint
9446 @item disable tracepoint @r{[}@var{num}@r{]}
9447 Disable tracepoint @var{num}, or all tracepoints if no argument
9448 @var{num} is given. A disabled tracepoint will have no effect during
9449 the next trace experiment, but it is not forgotten. You can re-enable
9450 a disabled tracepoint using the @code{enable tracepoint} command.
9452 @kindex enable tracepoint
9453 @item enable tracepoint @r{[}@var{num}@r{]}
9454 Enable tracepoint @var{num}, or all tracepoints. The enabled
9455 tracepoints will become effective the next time a trace experiment is
9459 @node Tracepoint Passcounts
9460 @subsection Tracepoint Passcounts
9464 @cindex tracepoint pass count
9465 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9466 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9467 automatically stop a trace experiment. If a tracepoint's passcount is
9468 @var{n}, then the trace experiment will be automatically stopped on
9469 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9470 @var{num} is not specified, the @code{passcount} command sets the
9471 passcount of the most recently defined tracepoint. If no passcount is
9472 given, the trace experiment will run until stopped explicitly by the
9478 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9479 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9481 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9482 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9483 (@value{GDBP}) @b{trace foo}
9484 (@value{GDBP}) @b{pass 3}
9485 (@value{GDBP}) @b{trace bar}
9486 (@value{GDBP}) @b{pass 2}
9487 (@value{GDBP}) @b{trace baz}
9488 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9489 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9490 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9491 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9495 @node Tracepoint Conditions
9496 @subsection Tracepoint Conditions
9497 @cindex conditional tracepoints
9498 @cindex tracepoint conditions
9500 The simplest sort of tracepoint collects data every time your program
9501 reaches a specified place. You can also specify a @dfn{condition} for
9502 a tracepoint. A condition is just a Boolean expression in your
9503 programming language (@pxref{Expressions, ,Expressions}). A
9504 tracepoint with a condition evaluates the expression each time your
9505 program reaches it, and data collection happens only if the condition
9508 Tracepoint conditions can be specified when a tracepoint is set, by
9509 using @samp{if} in the arguments to the @code{trace} command.
9510 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9511 also be set or changed at any time with the @code{condition} command,
9512 just as with breakpoints.
9514 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9515 the conditional expression itself. Instead, @value{GDBN} encodes the
9516 expression into an agent expression (@pxref{Agent Expressions}
9517 suitable for execution on the target, independently of @value{GDBN}.
9518 Global variables become raw memory locations, locals become stack
9519 accesses, and so forth.
9521 For instance, suppose you have a function that is usually called
9522 frequently, but should not be called after an error has occurred. You
9523 could use the following tracepoint command to collect data about calls
9524 of that function that happen while the error code is propagating
9525 through the program; an unconditional tracepoint could end up
9526 collecting thousands of useless trace frames that you would have to
9530 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9533 @node Trace State Variables
9534 @subsection Trace State Variables
9535 @cindex trace state variables
9537 A @dfn{trace state variable} is a special type of variable that is
9538 created and managed by target-side code. The syntax is the same as
9539 that for GDB's convenience variables (a string prefixed with ``$''),
9540 but they are stored on the target. They must be created explicitly,
9541 using a @code{tvariable} command. They are always 64-bit signed
9544 Trace state variables are remembered by @value{GDBN}, and downloaded
9545 to the target along with tracepoint information when the trace
9546 experiment starts. There are no intrinsic limits on the number of
9547 trace state variables, beyond memory limitations of the target.
9549 @cindex convenience variables, and trace state variables
9550 Although trace state variables are managed by the target, you can use
9551 them in print commands and expressions as if they were convenience
9552 variables; @value{GDBN} will get the current value from the target
9553 while the trace experiment is running. Trace state variables share
9554 the same namespace as other ``$'' variables, which means that you
9555 cannot have trace state variables with names like @code{$23} or
9556 @code{$pc}, nor can you have a trace state variable and a convenience
9557 variable with the same name.
9561 @item tvariable $@var{name} [ = @var{expression} ]
9563 The @code{tvariable} command creates a new trace state variable named
9564 @code{$@var{name}}, and optionally gives it an initial value of
9565 @var{expression}. @var{expression} is evaluated when this command is
9566 entered; the result will be converted to an integer if possible,
9567 otherwise @value{GDBN} will report an error. A subsequent
9568 @code{tvariable} command specifying the same name does not create a
9569 variable, but instead assigns the supplied initial value to the
9570 existing variable of that name, overwriting any previous initial
9571 value. The default initial value is 0.
9573 @item info tvariables
9574 @kindex info tvariables
9575 List all the trace state variables along with their initial values.
9576 Their current values may also be displayed, if the trace experiment is
9579 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9580 @kindex delete tvariable
9581 Delete the given trace state variables, or all of them if no arguments
9586 @node Tracepoint Actions
9587 @subsection Tracepoint Action Lists
9591 @cindex tracepoint actions
9592 @item actions @r{[}@var{num}@r{]}
9593 This command will prompt for a list of actions to be taken when the
9594 tracepoint is hit. If the tracepoint number @var{num} is not
9595 specified, this command sets the actions for the one that was most
9596 recently defined (so that you can define a tracepoint and then say
9597 @code{actions} without bothering about its number). You specify the
9598 actions themselves on the following lines, one action at a time, and
9599 terminate the actions list with a line containing just @code{end}. So
9600 far, the only defined actions are @code{collect} and
9601 @code{while-stepping}.
9603 @cindex remove actions from a tracepoint
9604 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9605 and follow it immediately with @samp{end}.
9608 (@value{GDBP}) @b{collect @var{data}} // collect some data
9610 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9612 (@value{GDBP}) @b{end} // signals the end of actions.
9615 In the following example, the action list begins with @code{collect}
9616 commands indicating the things to be collected when the tracepoint is
9617 hit. Then, in order to single-step and collect additional data
9618 following the tracepoint, a @code{while-stepping} command is used,
9619 followed by the list of things to be collected while stepping. The
9620 @code{while-stepping} command is terminated by its own separate
9621 @code{end} command. Lastly, the action list is terminated by an
9625 (@value{GDBP}) @b{trace foo}
9626 (@value{GDBP}) @b{actions}
9627 Enter actions for tracepoint 1, one per line:
9636 @kindex collect @r{(tracepoints)}
9637 @item collect @var{expr1}, @var{expr2}, @dots{}
9638 Collect values of the given expressions when the tracepoint is hit.
9639 This command accepts a comma-separated list of any valid expressions.
9640 In addition to global, static, or local variables, the following
9641 special arguments are supported:
9645 collect all registers
9648 collect all function arguments
9651 collect all local variables.
9654 You can give several consecutive @code{collect} commands, each one
9655 with a single argument, or one @code{collect} command with several
9656 arguments separated by commas: the effect is the same.
9658 The command @code{info scope} (@pxref{Symbols, info scope}) is
9659 particularly useful for figuring out what data to collect.
9661 @kindex teval @r{(tracepoints)}
9662 @item teval @var{expr1}, @var{expr2}, @dots{}
9663 Evaluate the given expressions when the tracepoint is hit. This
9664 command accepts a comma-separated list of expressions. The results
9665 are discarded, so this is mainly useful for assigning values to trace
9666 state variables (@pxref{Trace State Variables}) without adding those
9667 values to the trace buffer, as would be the case if the @code{collect}
9670 @kindex while-stepping @r{(tracepoints)}
9671 @item while-stepping @var{n}
9672 Perform @var{n} single-step instruction traces after the tracepoint,
9673 collecting new data at each instruction. The @code{while-stepping}
9674 command is followed by the list of what to collect while stepping
9675 (followed by its own @code{end} command):
9679 > collect $regs, myglobal
9685 You may abbreviate @code{while-stepping} as @code{ws} or
9688 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9689 @kindex set default-collect
9690 @cindex default collection action
9691 This variable is a list of expressions to collect at each tracepoint
9692 hit. It is effectively an additional @code{collect} action prepended
9693 to every tracepoint action list. The expressions are parsed
9694 individually for each tracepoint, so for instance a variable named
9695 @code{xyz} may be interpreted as a global for one tracepoint, and a
9696 local for another, as appropriate to the tracepoint's location.
9698 @item show default-collect
9699 @kindex show default-collect
9700 Show the list of expressions that are collected by default at each
9705 @node Listing Tracepoints
9706 @subsection Listing Tracepoints
9709 @kindex info tracepoints
9711 @cindex information about tracepoints
9712 @item info tracepoints @r{[}@var{num}@r{]}
9713 Display information about the tracepoint @var{num}. If you don't
9714 specify a tracepoint number, displays information about all the
9715 tracepoints defined so far. The format is similar to that used for
9716 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9717 command, simply restricting itself to tracepoints.
9719 A tracepoint's listing may include additional information specific to
9724 its passcount as given by the @code{passcount @var{n}} command
9726 its step count as given by the @code{while-stepping @var{n}} command
9728 its action list as given by the @code{actions} command. The actions
9729 are prefixed with an @samp{A} so as to distinguish them from commands.
9733 (@value{GDBP}) @b{info trace}
9734 Num Type Disp Enb Address What
9735 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9739 A collect globfoo, $regs
9747 This command can be abbreviated @code{info tp}.
9750 @node Starting and Stopping Trace Experiments
9751 @subsection Starting and Stopping Trace Experiments
9755 @cindex start a new trace experiment
9756 @cindex collected data discarded
9758 This command takes no arguments. It starts the trace experiment, and
9759 begins collecting data. This has the side effect of discarding all
9760 the data collected in the trace buffer during the previous trace
9764 @cindex stop a running trace experiment
9766 This command takes no arguments. It ends the trace experiment, and
9767 stops collecting data.
9769 @strong{Note}: a trace experiment and data collection may stop
9770 automatically if any tracepoint's passcount is reached
9771 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9774 @cindex status of trace data collection
9775 @cindex trace experiment, status of
9777 This command displays the status of the current trace data
9781 Here is an example of the commands we described so far:
9784 (@value{GDBP}) @b{trace gdb_c_test}
9785 (@value{GDBP}) @b{actions}
9786 Enter actions for tracepoint #1, one per line.
9787 > collect $regs,$locals,$args
9792 (@value{GDBP}) @b{tstart}
9793 [time passes @dots{}]
9794 (@value{GDBP}) @b{tstop}
9797 @cindex disconnected tracing
9798 You can choose to continue running the trace experiment even if
9799 @value{GDBN} disconnects from the target, voluntarily or
9800 involuntarily. For commands such as @code{detach}, the debugger will
9801 ask what you want to do with the trace. But for unexpected
9802 terminations (@value{GDBN} crash, network outage), it would be
9803 unfortunate to lose hard-won trace data, so the variable
9804 @code{disconnected-tracing} lets you decide whether the trace should
9805 continue running without @value{GDBN}.
9808 @item set disconnected-tracing on
9809 @itemx set disconnected-tracing off
9810 @kindex set disconnected-tracing
9811 Choose whether a tracing run should continue to run if @value{GDBN}
9812 has disconnected from the target. Note that @code{detach} or
9813 @code{quit} will ask you directly what to do about a running trace no
9814 matter what this variable's setting, so the variable is mainly useful
9815 for handling unexpected situations, such as loss of the network.
9817 @item show disconnected-tracing
9818 @kindex show disconnected-tracing
9819 Show the current choice for disconnected tracing.
9823 When you reconnect to the target, the trace experiment may or may not
9824 still be running; it might have filled the trace buffer in the
9825 meantime, or stopped for one of the other reasons. If it is running,
9826 it will continue after reconnection.
9828 Upon reconnection, the target will upload information about the
9829 tracepoints in effect. @value{GDBN} will then compare that
9830 information to the set of tracepoints currently defined, and attempt
9831 to match them up, allowing for the possibility that the numbers may
9832 have changed due to creation and deletion in the meantime. If one of
9833 the target's tracepoints does not match any in @value{GDBN}, the
9834 debugger will create a new tracepoint, so that you have a number with
9835 which to specify that tracepoint. This matching-up process is
9836 necessarily heuristic, and it may result in useless tracepoints being
9837 created; you may simply delete them if they are of no use.
9839 @cindex circular trace buffer
9840 If your target agent supports a @dfn{circular trace buffer}, then you
9841 can run a trace experiment indefinitely without filling the trace
9842 buffer; when space runs out, the agent deletes already-collected trace
9843 frames, oldest first, until there is enough room to continue
9844 collecting. This is especially useful if your tracepoints are being
9845 hit too often, and your trace gets terminated prematurely because the
9846 buffer is full. To ask for a circular trace buffer, simply set
9847 @samp{circular_trace_buffer} to on. You can set this at any time,
9848 including during tracing; if the agent can do it, it will change
9849 buffer handling on the fly, otherwise it will not take effect until
9853 @item set circular-trace-buffer on
9854 @itemx set circular-trace-buffer off
9855 @kindex set circular-trace-buffer
9856 Choose whether a tracing run should use a linear or circular buffer
9857 for trace data. A linear buffer will not lose any trace data, but may
9858 fill up prematurely, while a circular buffer will discard old trace
9859 data, but it will have always room for the latest tracepoint hits.
9861 @item show circular-trace-buffer
9862 @kindex show circular-trace-buffer
9863 Show the current choice for the trace buffer. Note that this may not
9864 match the agent's current buffer handling, nor is it guaranteed to
9865 match the setting that might have been in effect during a past run,
9866 for instance if you are looking at frames from a trace file.
9870 @node Tracepoint Restrictions
9871 @subsection Tracepoint Restrictions
9873 @cindex tracepoint restrictions
9874 There are a number of restrictions on the use of tracepoints. As
9875 described above, tracepoint data gathering occurs on the target
9876 without interaction from @value{GDBN}. Thus the full capabilities of
9877 the debugger are not available during data gathering, and then at data
9878 examination time, you will be limited by only having what was
9879 collected. The following items describe some common problems, but it
9880 is not exhaustive, and you may run into additional difficulties not
9886 Tracepoint expressions are intended to gather objects (lvalues). Thus
9887 the full flexibility of GDB's expression evaluator is not available.
9888 You cannot call functions, cast objects to aggregate types, access
9889 convenience variables or modify values (except by assignment to trace
9890 state variables). Some language features may implicitly call
9891 functions (for instance Objective-C fields with accessors), and therefore
9892 cannot be collected either.
9895 Collection of local variables, either individually or in bulk with
9896 @code{$locals} or @code{$args}, during @code{while-stepping} may
9897 behave erratically. The stepping action may enter a new scope (for
9898 instance by stepping into a function), or the location of the variable
9899 may change (for instance it is loaded into a register). The
9900 tracepoint data recorded uses the location information for the
9901 variables that is correct for the tracepoint location. When the
9902 tracepoint is created, it is not possible, in general, to determine
9903 where the steps of a @code{while-stepping} sequence will advance the
9904 program---particularly if a conditional branch is stepped.
9907 Collection of an incompletely-initialized or partially-destroyed object
9908 may result in something that @value{GDBN} cannot display, or displays
9909 in a misleading way.
9912 When @value{GDBN} displays a pointer to character it automatically
9913 dereferences the pointer to also display characters of the string
9914 being pointed to. However, collecting the pointer during tracing does
9915 not automatically collect the string. You need to explicitly
9916 dereference the pointer and provide size information if you want to
9917 collect not only the pointer, but the memory pointed to. For example,
9918 @code{*ptr@@50} can be used to collect the 50 element array pointed to
9922 It is not possible to collect a complete stack backtrace at a
9923 tracepoint. Instead, you may collect the registers and a few hundred
9924 bytes from the stack pointer with something like @code{*$esp@@300}
9925 (adjust to use the name of the actual stack pointer register on your
9926 target architecture, and the amount of stack you wish to capture).
9927 Then the @code{backtrace} command will show a partial backtrace when
9928 using a trace frame. The number of stack frames that can be examined
9929 depends on the sizes of the frames in the collected stack. Note that
9930 if you ask for a block so large that it goes past the bottom of the
9931 stack, the target agent may report an error trying to read from an
9936 @node Analyze Collected Data
9937 @section Using the Collected Data
9939 After the tracepoint experiment ends, you use @value{GDBN} commands
9940 for examining the trace data. The basic idea is that each tracepoint
9941 collects a trace @dfn{snapshot} every time it is hit and another
9942 snapshot every time it single-steps. All these snapshots are
9943 consecutively numbered from zero and go into a buffer, and you can
9944 examine them later. The way you examine them is to @dfn{focus} on a
9945 specific trace snapshot. When the remote stub is focused on a trace
9946 snapshot, it will respond to all @value{GDBN} requests for memory and
9947 registers by reading from the buffer which belongs to that snapshot,
9948 rather than from @emph{real} memory or registers of the program being
9949 debugged. This means that @strong{all} @value{GDBN} commands
9950 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9951 behave as if we were currently debugging the program state as it was
9952 when the tracepoint occurred. Any requests for data that are not in
9953 the buffer will fail.
9956 * tfind:: How to select a trace snapshot
9957 * tdump:: How to display all data for a snapshot
9958 * save-tracepoints:: How to save tracepoints for a future run
9962 @subsection @code{tfind @var{n}}
9965 @cindex select trace snapshot
9966 @cindex find trace snapshot
9967 The basic command for selecting a trace snapshot from the buffer is
9968 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9969 counting from zero. If no argument @var{n} is given, the next
9970 snapshot is selected.
9972 Here are the various forms of using the @code{tfind} command.
9976 Find the first snapshot in the buffer. This is a synonym for
9977 @code{tfind 0} (since 0 is the number of the first snapshot).
9980 Stop debugging trace snapshots, resume @emph{live} debugging.
9983 Same as @samp{tfind none}.
9986 No argument means find the next trace snapshot.
9989 Find the previous trace snapshot before the current one. This permits
9990 retracing earlier steps.
9992 @item tfind tracepoint @var{num}
9993 Find the next snapshot associated with tracepoint @var{num}. Search
9994 proceeds forward from the last examined trace snapshot. If no
9995 argument @var{num} is given, it means find the next snapshot collected
9996 for the same tracepoint as the current snapshot.
9998 @item tfind pc @var{addr}
9999 Find the next snapshot associated with the value @var{addr} of the
10000 program counter. Search proceeds forward from the last examined trace
10001 snapshot. If no argument @var{addr} is given, it means find the next
10002 snapshot with the same value of PC as the current snapshot.
10004 @item tfind outside @var{addr1}, @var{addr2}
10005 Find the next snapshot whose PC is outside the given range of
10006 addresses (exclusive).
10008 @item tfind range @var{addr1}, @var{addr2}
10009 Find the next snapshot whose PC is between @var{addr1} and
10010 @var{addr2} (inclusive).
10012 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10013 Find the next snapshot associated with the source line @var{n}. If
10014 the optional argument @var{file} is given, refer to line @var{n} in
10015 that source file. Search proceeds forward from the last examined
10016 trace snapshot. If no argument @var{n} is given, it means find the
10017 next line other than the one currently being examined; thus saying
10018 @code{tfind line} repeatedly can appear to have the same effect as
10019 stepping from line to line in a @emph{live} debugging session.
10022 The default arguments for the @code{tfind} commands are specifically
10023 designed to make it easy to scan through the trace buffer. For
10024 instance, @code{tfind} with no argument selects the next trace
10025 snapshot, and @code{tfind -} with no argument selects the previous
10026 trace snapshot. So, by giving one @code{tfind} command, and then
10027 simply hitting @key{RET} repeatedly you can examine all the trace
10028 snapshots in order. Or, by saying @code{tfind -} and then hitting
10029 @key{RET} repeatedly you can examine the snapshots in reverse order.
10030 The @code{tfind line} command with no argument selects the snapshot
10031 for the next source line executed. The @code{tfind pc} command with
10032 no argument selects the next snapshot with the same program counter
10033 (PC) as the current frame. The @code{tfind tracepoint} command with
10034 no argument selects the next trace snapshot collected by the same
10035 tracepoint as the current one.
10037 In addition to letting you scan through the trace buffer manually,
10038 these commands make it easy to construct @value{GDBN} scripts that
10039 scan through the trace buffer and print out whatever collected data
10040 you are interested in. Thus, if we want to examine the PC, FP, and SP
10041 registers from each trace frame in the buffer, we can say this:
10044 (@value{GDBP}) @b{tfind start}
10045 (@value{GDBP}) @b{while ($trace_frame != -1)}
10046 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10047 $trace_frame, $pc, $sp, $fp
10051 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10052 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10053 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10054 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10055 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10056 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10057 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10058 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10059 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10060 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10061 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10064 Or, if we want to examine the variable @code{X} at each source line in
10068 (@value{GDBP}) @b{tfind start}
10069 (@value{GDBP}) @b{while ($trace_frame != -1)}
10070 > printf "Frame %d, X == %d\n", $trace_frame, X
10080 @subsection @code{tdump}
10082 @cindex dump all data collected at tracepoint
10083 @cindex tracepoint data, display
10085 This command takes no arguments. It prints all the data collected at
10086 the current trace snapshot.
10089 (@value{GDBP}) @b{trace 444}
10090 (@value{GDBP}) @b{actions}
10091 Enter actions for tracepoint #2, one per line:
10092 > collect $regs, $locals, $args, gdb_long_test
10095 (@value{GDBP}) @b{tstart}
10097 (@value{GDBP}) @b{tfind line 444}
10098 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10100 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10102 (@value{GDBP}) @b{tdump}
10103 Data collected at tracepoint 2, trace frame 1:
10104 d0 0xc4aa0085 -995491707
10108 d4 0x71aea3d 119204413
10111 d7 0x380035 3670069
10112 a0 0x19e24a 1696330
10113 a1 0x3000668 50333288
10115 a3 0x322000 3284992
10116 a4 0x3000698 50333336
10117 a5 0x1ad3cc 1758156
10118 fp 0x30bf3c 0x30bf3c
10119 sp 0x30bf34 0x30bf34
10121 pc 0x20b2c8 0x20b2c8
10125 p = 0x20e5b4 "gdb-test"
10132 gdb_long_test = 17 '\021'
10137 @node save-tracepoints
10138 @subsection @code{save-tracepoints @var{filename}}
10139 @kindex save-tracepoints
10140 @cindex save tracepoints for future sessions
10142 This command saves all current tracepoint definitions together with
10143 their actions and passcounts, into a file @file{@var{filename}}
10144 suitable for use in a later debugging session. To read the saved
10145 tracepoint definitions, use the @code{source} command (@pxref{Command
10148 @node Tracepoint Variables
10149 @section Convenience Variables for Tracepoints
10150 @cindex tracepoint variables
10151 @cindex convenience variables for tracepoints
10154 @vindex $trace_frame
10155 @item (int) $trace_frame
10156 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10157 snapshot is selected.
10159 @vindex $tracepoint
10160 @item (int) $tracepoint
10161 The tracepoint for the current trace snapshot.
10163 @vindex $trace_line
10164 @item (int) $trace_line
10165 The line number for the current trace snapshot.
10167 @vindex $trace_file
10168 @item (char []) $trace_file
10169 The source file for the current trace snapshot.
10171 @vindex $trace_func
10172 @item (char []) $trace_func
10173 The name of the function containing @code{$tracepoint}.
10176 Note: @code{$trace_file} is not suitable for use in @code{printf},
10177 use @code{output} instead.
10179 Here's a simple example of using these convenience variables for
10180 stepping through all the trace snapshots and printing some of their
10181 data. Note that these are not the same as trace state variables,
10182 which are managed by the target.
10185 (@value{GDBP}) @b{tfind start}
10187 (@value{GDBP}) @b{while $trace_frame != -1}
10188 > output $trace_file
10189 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10195 @section Using Trace Files
10196 @cindex trace files
10198 In some situations, the target running a trace experiment may no
10199 longer be available; perhaps it crashed, or the hardware was needed
10200 for a different activity. To handle these cases, you can arrange to
10201 dump the trace data into a file, and later use that file as a source
10202 of trace data, via the @code{target tfile} command.
10207 @item tsave [ -r ] @var{filename}
10208 Save the trace data to @var{filename}. By default, this command
10209 assumes that @var{filename} refers to the host filesystem, so if
10210 necessary @value{GDBN} will copy raw trace data up from the target and
10211 then save it. If the target supports it, you can also supply the
10212 optional argument @code{-r} (``remote'') to direct the target to save
10213 the data directly into @var{filename} in its own filesystem, which may be
10214 more efficient if the trace buffer is very large. (Note, however, that
10215 @code{target tfile} can only read from files accessible to the host.)
10217 @kindex target tfile
10219 @item target tfile @var{filename}
10220 Use the file named @var{filename} as a source of trace data. Commands
10221 that examine data work as they do with a live target, but it is not
10222 possible to run any new trace experiments. @code{tstatus} will report
10223 the state of the trace run at the moment the data was saved, as well
10224 as the current trace frame you are examining. @var{filename} must be
10225 on a filesystem accessible to the host.
10230 @chapter Debugging Programs That Use Overlays
10233 If your program is too large to fit completely in your target system's
10234 memory, you can sometimes use @dfn{overlays} to work around this
10235 problem. @value{GDBN} provides some support for debugging programs that
10239 * How Overlays Work:: A general explanation of overlays.
10240 * Overlay Commands:: Managing overlays in @value{GDBN}.
10241 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10242 mapped by asking the inferior.
10243 * Overlay Sample Program:: A sample program using overlays.
10246 @node How Overlays Work
10247 @section How Overlays Work
10248 @cindex mapped overlays
10249 @cindex unmapped overlays
10250 @cindex load address, overlay's
10251 @cindex mapped address
10252 @cindex overlay area
10254 Suppose you have a computer whose instruction address space is only 64
10255 kilobytes long, but which has much more memory which can be accessed by
10256 other means: special instructions, segment registers, or memory
10257 management hardware, for example. Suppose further that you want to
10258 adapt a program which is larger than 64 kilobytes to run on this system.
10260 One solution is to identify modules of your program which are relatively
10261 independent, and need not call each other directly; call these modules
10262 @dfn{overlays}. Separate the overlays from the main program, and place
10263 their machine code in the larger memory. Place your main program in
10264 instruction memory, but leave at least enough space there to hold the
10265 largest overlay as well.
10267 Now, to call a function located in an overlay, you must first copy that
10268 overlay's machine code from the large memory into the space set aside
10269 for it in the instruction memory, and then jump to its entry point
10272 @c NB: In the below the mapped area's size is greater or equal to the
10273 @c size of all overlays. This is intentional to remind the developer
10274 @c that overlays don't necessarily need to be the same size.
10278 Data Instruction Larger
10279 Address Space Address Space Address Space
10280 +-----------+ +-----------+ +-----------+
10282 +-----------+ +-----------+ +-----------+<-- overlay 1
10283 | program | | main | .----| overlay 1 | load address
10284 | variables | | program | | +-----------+
10285 | and heap | | | | | |
10286 +-----------+ | | | +-----------+<-- overlay 2
10287 | | +-----------+ | | | load address
10288 +-----------+ | | | .-| overlay 2 |
10290 mapped --->+-----------+ | | +-----------+
10291 address | | | | | |
10292 | overlay | <-' | | |
10293 | area | <---' +-----------+<-- overlay 3
10294 | | <---. | | load address
10295 +-----------+ `--| overlay 3 |
10302 @anchor{A code overlay}A code overlay
10306 The diagram (@pxref{A code overlay}) shows a system with separate data
10307 and instruction address spaces. To map an overlay, the program copies
10308 its code from the larger address space to the instruction address space.
10309 Since the overlays shown here all use the same mapped address, only one
10310 may be mapped at a time. For a system with a single address space for
10311 data and instructions, the diagram would be similar, except that the
10312 program variables and heap would share an address space with the main
10313 program and the overlay area.
10315 An overlay loaded into instruction memory and ready for use is called a
10316 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10317 instruction memory. An overlay not present (or only partially present)
10318 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10319 is its address in the larger memory. The mapped address is also called
10320 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10321 called the @dfn{load memory address}, or @dfn{LMA}.
10323 Unfortunately, overlays are not a completely transparent way to adapt a
10324 program to limited instruction memory. They introduce a new set of
10325 global constraints you must keep in mind as you design your program:
10330 Before calling or returning to a function in an overlay, your program
10331 must make sure that overlay is actually mapped. Otherwise, the call or
10332 return will transfer control to the right address, but in the wrong
10333 overlay, and your program will probably crash.
10336 If the process of mapping an overlay is expensive on your system, you
10337 will need to choose your overlays carefully to minimize their effect on
10338 your program's performance.
10341 The executable file you load onto your system must contain each
10342 overlay's instructions, appearing at the overlay's load address, not its
10343 mapped address. However, each overlay's instructions must be relocated
10344 and its symbols defined as if the overlay were at its mapped address.
10345 You can use GNU linker scripts to specify different load and relocation
10346 addresses for pieces of your program; see @ref{Overlay Description,,,
10347 ld.info, Using ld: the GNU linker}.
10350 The procedure for loading executable files onto your system must be able
10351 to load their contents into the larger address space as well as the
10352 instruction and data spaces.
10356 The overlay system described above is rather simple, and could be
10357 improved in many ways:
10362 If your system has suitable bank switch registers or memory management
10363 hardware, you could use those facilities to make an overlay's load area
10364 contents simply appear at their mapped address in instruction space.
10365 This would probably be faster than copying the overlay to its mapped
10366 area in the usual way.
10369 If your overlays are small enough, you could set aside more than one
10370 overlay area, and have more than one overlay mapped at a time.
10373 You can use overlays to manage data, as well as instructions. In
10374 general, data overlays are even less transparent to your design than
10375 code overlays: whereas code overlays only require care when you call or
10376 return to functions, data overlays require care every time you access
10377 the data. Also, if you change the contents of a data overlay, you
10378 must copy its contents back out to its load address before you can copy a
10379 different data overlay into the same mapped area.
10384 @node Overlay Commands
10385 @section Overlay Commands
10387 To use @value{GDBN}'s overlay support, each overlay in your program must
10388 correspond to a separate section of the executable file. The section's
10389 virtual memory address and load memory address must be the overlay's
10390 mapped and load addresses. Identifying overlays with sections allows
10391 @value{GDBN} to determine the appropriate address of a function or
10392 variable, depending on whether the overlay is mapped or not.
10394 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10395 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10400 Disable @value{GDBN}'s overlay support. When overlay support is
10401 disabled, @value{GDBN} assumes that all functions and variables are
10402 always present at their mapped addresses. By default, @value{GDBN}'s
10403 overlay support is disabled.
10405 @item overlay manual
10406 @cindex manual overlay debugging
10407 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10408 relies on you to tell it which overlays are mapped, and which are not,
10409 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10410 commands described below.
10412 @item overlay map-overlay @var{overlay}
10413 @itemx overlay map @var{overlay}
10414 @cindex map an overlay
10415 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10416 be the name of the object file section containing the overlay. When an
10417 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10418 functions and variables at their mapped addresses. @value{GDBN} assumes
10419 that any other overlays whose mapped ranges overlap that of
10420 @var{overlay} are now unmapped.
10422 @item overlay unmap-overlay @var{overlay}
10423 @itemx overlay unmap @var{overlay}
10424 @cindex unmap an overlay
10425 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10426 must be the name of the object file section containing the overlay.
10427 When an overlay is unmapped, @value{GDBN} assumes it can find the
10428 overlay's functions and variables at their load addresses.
10431 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10432 consults a data structure the overlay manager maintains in the inferior
10433 to see which overlays are mapped. For details, see @ref{Automatic
10434 Overlay Debugging}.
10436 @item overlay load-target
10437 @itemx overlay load
10438 @cindex reloading the overlay table
10439 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10440 re-reads the table @value{GDBN} automatically each time the inferior
10441 stops, so this command should only be necessary if you have changed the
10442 overlay mapping yourself using @value{GDBN}. This command is only
10443 useful when using automatic overlay debugging.
10445 @item overlay list-overlays
10446 @itemx overlay list
10447 @cindex listing mapped overlays
10448 Display a list of the overlays currently mapped, along with their mapped
10449 addresses, load addresses, and sizes.
10453 Normally, when @value{GDBN} prints a code address, it includes the name
10454 of the function the address falls in:
10457 (@value{GDBP}) print main
10458 $3 = @{int ()@} 0x11a0 <main>
10461 When overlay debugging is enabled, @value{GDBN} recognizes code in
10462 unmapped overlays, and prints the names of unmapped functions with
10463 asterisks around them. For example, if @code{foo} is a function in an
10464 unmapped overlay, @value{GDBN} prints it this way:
10467 (@value{GDBP}) overlay list
10468 No sections are mapped.
10469 (@value{GDBP}) print foo
10470 $5 = @{int (int)@} 0x100000 <*foo*>
10473 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10477 (@value{GDBP}) overlay list
10478 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10479 mapped at 0x1016 - 0x104a
10480 (@value{GDBP}) print foo
10481 $6 = @{int (int)@} 0x1016 <foo>
10484 When overlay debugging is enabled, @value{GDBN} can find the correct
10485 address for functions and variables in an overlay, whether or not the
10486 overlay is mapped. This allows most @value{GDBN} commands, like
10487 @code{break} and @code{disassemble}, to work normally, even on unmapped
10488 code. However, @value{GDBN}'s breakpoint support has some limitations:
10492 @cindex breakpoints in overlays
10493 @cindex overlays, setting breakpoints in
10494 You can set breakpoints in functions in unmapped overlays, as long as
10495 @value{GDBN} can write to the overlay at its load address.
10497 @value{GDBN} can not set hardware or simulator-based breakpoints in
10498 unmapped overlays. However, if you set a breakpoint at the end of your
10499 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10500 you are using manual overlay management), @value{GDBN} will re-set its
10501 breakpoints properly.
10505 @node Automatic Overlay Debugging
10506 @section Automatic Overlay Debugging
10507 @cindex automatic overlay debugging
10509 @value{GDBN} can automatically track which overlays are mapped and which
10510 are not, given some simple co-operation from the overlay manager in the
10511 inferior. If you enable automatic overlay debugging with the
10512 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10513 looks in the inferior's memory for certain variables describing the
10514 current state of the overlays.
10516 Here are the variables your overlay manager must define to support
10517 @value{GDBN}'s automatic overlay debugging:
10521 @item @code{_ovly_table}:
10522 This variable must be an array of the following structures:
10527 /* The overlay's mapped address. */
10530 /* The size of the overlay, in bytes. */
10531 unsigned long size;
10533 /* The overlay's load address. */
10536 /* Non-zero if the overlay is currently mapped;
10538 unsigned long mapped;
10542 @item @code{_novlys}:
10543 This variable must be a four-byte signed integer, holding the total
10544 number of elements in @code{_ovly_table}.
10548 To decide whether a particular overlay is mapped or not, @value{GDBN}
10549 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10550 @code{lma} members equal the VMA and LMA of the overlay's section in the
10551 executable file. When @value{GDBN} finds a matching entry, it consults
10552 the entry's @code{mapped} member to determine whether the overlay is
10555 In addition, your overlay manager may define a function called
10556 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10557 will silently set a breakpoint there. If the overlay manager then
10558 calls this function whenever it has changed the overlay table, this
10559 will enable @value{GDBN} to accurately keep track of which overlays
10560 are in program memory, and update any breakpoints that may be set
10561 in overlays. This will allow breakpoints to work even if the
10562 overlays are kept in ROM or other non-writable memory while they
10563 are not being executed.
10565 @node Overlay Sample Program
10566 @section Overlay Sample Program
10567 @cindex overlay example program
10569 When linking a program which uses overlays, you must place the overlays
10570 at their load addresses, while relocating them to run at their mapped
10571 addresses. To do this, you must write a linker script (@pxref{Overlay
10572 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10573 since linker scripts are specific to a particular host system, target
10574 architecture, and target memory layout, this manual cannot provide
10575 portable sample code demonstrating @value{GDBN}'s overlay support.
10577 However, the @value{GDBN} source distribution does contain an overlaid
10578 program, with linker scripts for a few systems, as part of its test
10579 suite. The program consists of the following files from
10580 @file{gdb/testsuite/gdb.base}:
10584 The main program file.
10586 A simple overlay manager, used by @file{overlays.c}.
10591 Overlay modules, loaded and used by @file{overlays.c}.
10594 Linker scripts for linking the test program on the @code{d10v-elf}
10595 and @code{m32r-elf} targets.
10598 You can build the test program using the @code{d10v-elf} GCC
10599 cross-compiler like this:
10602 $ d10v-elf-gcc -g -c overlays.c
10603 $ d10v-elf-gcc -g -c ovlymgr.c
10604 $ d10v-elf-gcc -g -c foo.c
10605 $ d10v-elf-gcc -g -c bar.c
10606 $ d10v-elf-gcc -g -c baz.c
10607 $ d10v-elf-gcc -g -c grbx.c
10608 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10609 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10612 The build process is identical for any other architecture, except that
10613 you must substitute the appropriate compiler and linker script for the
10614 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10618 @chapter Using @value{GDBN} with Different Languages
10621 Although programming languages generally have common aspects, they are
10622 rarely expressed in the same manner. For instance, in ANSI C,
10623 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10624 Modula-2, it is accomplished by @code{p^}. Values can also be
10625 represented (and displayed) differently. Hex numbers in C appear as
10626 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10628 @cindex working language
10629 Language-specific information is built into @value{GDBN} for some languages,
10630 allowing you to express operations like the above in your program's
10631 native language, and allowing @value{GDBN} to output values in a manner
10632 consistent with the syntax of your program's native language. The
10633 language you use to build expressions is called the @dfn{working
10637 * Setting:: Switching between source languages
10638 * Show:: Displaying the language
10639 * Checks:: Type and range checks
10640 * Supported Languages:: Supported languages
10641 * Unsupported Languages:: Unsupported languages
10645 @section Switching Between Source Languages
10647 There are two ways to control the working language---either have @value{GDBN}
10648 set it automatically, or select it manually yourself. You can use the
10649 @code{set language} command for either purpose. On startup, @value{GDBN}
10650 defaults to setting the language automatically. The working language is
10651 used to determine how expressions you type are interpreted, how values
10654 In addition to the working language, every source file that
10655 @value{GDBN} knows about has its own working language. For some object
10656 file formats, the compiler might indicate which language a particular
10657 source file is in. However, most of the time @value{GDBN} infers the
10658 language from the name of the file. The language of a source file
10659 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10660 show each frame appropriately for its own language. There is no way to
10661 set the language of a source file from within @value{GDBN}, but you can
10662 set the language associated with a filename extension. @xref{Show, ,
10663 Displaying the Language}.
10665 This is most commonly a problem when you use a program, such
10666 as @code{cfront} or @code{f2c}, that generates C but is written in
10667 another language. In that case, make the
10668 program use @code{#line} directives in its C output; that way
10669 @value{GDBN} will know the correct language of the source code of the original
10670 program, and will display that source code, not the generated C code.
10673 * Filenames:: Filename extensions and languages.
10674 * Manually:: Setting the working language manually
10675 * Automatically:: Having @value{GDBN} infer the source language
10679 @subsection List of Filename Extensions and Languages
10681 If a source file name ends in one of the following extensions, then
10682 @value{GDBN} infers that its language is the one indicated.
10700 C@t{++} source file
10703 Objective-C source file
10707 Fortran source file
10710 Modula-2 source file
10714 Assembler source file. This actually behaves almost like C, but
10715 @value{GDBN} does not skip over function prologues when stepping.
10718 In addition, you may set the language associated with a filename
10719 extension. @xref{Show, , Displaying the Language}.
10722 @subsection Setting the Working Language
10724 If you allow @value{GDBN} to set the language automatically,
10725 expressions are interpreted the same way in your debugging session and
10728 @kindex set language
10729 If you wish, you may set the language manually. To do this, issue the
10730 command @samp{set language @var{lang}}, where @var{lang} is the name of
10731 a language, such as
10732 @code{c} or @code{modula-2}.
10733 For a list of the supported languages, type @samp{set language}.
10735 Setting the language manually prevents @value{GDBN} from updating the working
10736 language automatically. This can lead to confusion if you try
10737 to debug a program when the working language is not the same as the
10738 source language, when an expression is acceptable to both
10739 languages---but means different things. For instance, if the current
10740 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10748 might not have the effect you intended. In C, this means to add
10749 @code{b} and @code{c} and place the result in @code{a}. The result
10750 printed would be the value of @code{a}. In Modula-2, this means to compare
10751 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10753 @node Automatically
10754 @subsection Having @value{GDBN} Infer the Source Language
10756 To have @value{GDBN} set the working language automatically, use
10757 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10758 then infers the working language. That is, when your program stops in a
10759 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10760 working language to the language recorded for the function in that
10761 frame. If the language for a frame is unknown (that is, if the function
10762 or block corresponding to the frame was defined in a source file that
10763 does not have a recognized extension), the current working language is
10764 not changed, and @value{GDBN} issues a warning.
10766 This may not seem necessary for most programs, which are written
10767 entirely in one source language. However, program modules and libraries
10768 written in one source language can be used by a main program written in
10769 a different source language. Using @samp{set language auto} in this
10770 case frees you from having to set the working language manually.
10773 @section Displaying the Language
10775 The following commands help you find out which language is the
10776 working language, and also what language source files were written in.
10779 @item show language
10780 @kindex show language
10781 Display the current working language. This is the
10782 language you can use with commands such as @code{print} to
10783 build and compute expressions that may involve variables in your program.
10786 @kindex info frame@r{, show the source language}
10787 Display the source language for this frame. This language becomes the
10788 working language if you use an identifier from this frame.
10789 @xref{Frame Info, ,Information about a Frame}, to identify the other
10790 information listed here.
10793 @kindex info source@r{, show the source language}
10794 Display the source language of this source file.
10795 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10796 information listed here.
10799 In unusual circumstances, you may have source files with extensions
10800 not in the standard list. You can then set the extension associated
10801 with a language explicitly:
10804 @item set extension-language @var{ext} @var{language}
10805 @kindex set extension-language
10806 Tell @value{GDBN} that source files with extension @var{ext} are to be
10807 assumed as written in the source language @var{language}.
10809 @item info extensions
10810 @kindex info extensions
10811 List all the filename extensions and the associated languages.
10815 @section Type and Range Checking
10818 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10819 checking are included, but they do not yet have any effect. This
10820 section documents the intended facilities.
10822 @c FIXME remove warning when type/range code added
10824 Some languages are designed to guard you against making seemingly common
10825 errors through a series of compile- and run-time checks. These include
10826 checking the type of arguments to functions and operators, and making
10827 sure mathematical overflows are caught at run time. Checks such as
10828 these help to ensure a program's correctness once it has been compiled
10829 by eliminating type mismatches, and providing active checks for range
10830 errors when your program is running.
10832 @value{GDBN} can check for conditions like the above if you wish.
10833 Although @value{GDBN} does not check the statements in your program,
10834 it can check expressions entered directly into @value{GDBN} for
10835 evaluation via the @code{print} command, for example. As with the
10836 working language, @value{GDBN} can also decide whether or not to check
10837 automatically based on your program's source language.
10838 @xref{Supported Languages, ,Supported Languages}, for the default
10839 settings of supported languages.
10842 * Type Checking:: An overview of type checking
10843 * Range Checking:: An overview of range checking
10846 @cindex type checking
10847 @cindex checks, type
10848 @node Type Checking
10849 @subsection An Overview of Type Checking
10851 Some languages, such as Modula-2, are strongly typed, meaning that the
10852 arguments to operators and functions have to be of the correct type,
10853 otherwise an error occurs. These checks prevent type mismatch
10854 errors from ever causing any run-time problems. For example,
10862 The second example fails because the @code{CARDINAL} 1 is not
10863 type-compatible with the @code{REAL} 2.3.
10865 For the expressions you use in @value{GDBN} commands, you can tell the
10866 @value{GDBN} type checker to skip checking;
10867 to treat any mismatches as errors and abandon the expression;
10868 or to only issue warnings when type mismatches occur,
10869 but evaluate the expression anyway. When you choose the last of
10870 these, @value{GDBN} evaluates expressions like the second example above, but
10871 also issues a warning.
10873 Even if you turn type checking off, there may be other reasons
10874 related to type that prevent @value{GDBN} from evaluating an expression.
10875 For instance, @value{GDBN} does not know how to add an @code{int} and
10876 a @code{struct foo}. These particular type errors have nothing to do
10877 with the language in use, and usually arise from expressions, such as
10878 the one described above, which make little sense to evaluate anyway.
10880 Each language defines to what degree it is strict about type. For
10881 instance, both Modula-2 and C require the arguments to arithmetical
10882 operators to be numbers. In C, enumerated types and pointers can be
10883 represented as numbers, so that they are valid arguments to mathematical
10884 operators. @xref{Supported Languages, ,Supported Languages}, for further
10885 details on specific languages.
10887 @value{GDBN} provides some additional commands for controlling the type checker:
10889 @kindex set check type
10890 @kindex show check type
10892 @item set check type auto
10893 Set type checking on or off based on the current working language.
10894 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10897 @item set check type on
10898 @itemx set check type off
10899 Set type checking on or off, overriding the default setting for the
10900 current working language. Issue a warning if the setting does not
10901 match the language default. If any type mismatches occur in
10902 evaluating an expression while type checking is on, @value{GDBN} prints a
10903 message and aborts evaluation of the expression.
10905 @item set check type warn
10906 Cause the type checker to issue warnings, but to always attempt to
10907 evaluate the expression. Evaluating the expression may still
10908 be impossible for other reasons. For example, @value{GDBN} cannot add
10909 numbers and structures.
10912 Show the current setting of the type checker, and whether or not @value{GDBN}
10913 is setting it automatically.
10916 @cindex range checking
10917 @cindex checks, range
10918 @node Range Checking
10919 @subsection An Overview of Range Checking
10921 In some languages (such as Modula-2), it is an error to exceed the
10922 bounds of a type; this is enforced with run-time checks. Such range
10923 checking is meant to ensure program correctness by making sure
10924 computations do not overflow, or indices on an array element access do
10925 not exceed the bounds of the array.
10927 For expressions you use in @value{GDBN} commands, you can tell
10928 @value{GDBN} to treat range errors in one of three ways: ignore them,
10929 always treat them as errors and abandon the expression, or issue
10930 warnings but evaluate the expression anyway.
10932 A range error can result from numerical overflow, from exceeding an
10933 array index bound, or when you type a constant that is not a member
10934 of any type. Some languages, however, do not treat overflows as an
10935 error. In many implementations of C, mathematical overflow causes the
10936 result to ``wrap around'' to lower values---for example, if @var{m} is
10937 the largest integer value, and @var{s} is the smallest, then
10940 @var{m} + 1 @result{} @var{s}
10943 This, too, is specific to individual languages, and in some cases
10944 specific to individual compilers or machines. @xref{Supported Languages, ,
10945 Supported Languages}, for further details on specific languages.
10947 @value{GDBN} provides some additional commands for controlling the range checker:
10949 @kindex set check range
10950 @kindex show check range
10952 @item set check range auto
10953 Set range checking on or off based on the current working language.
10954 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10957 @item set check range on
10958 @itemx set check range off
10959 Set range checking on or off, overriding the default setting for the
10960 current working language. A warning is issued if the setting does not
10961 match the language default. If a range error occurs and range checking is on,
10962 then a message is printed and evaluation of the expression is aborted.
10964 @item set check range warn
10965 Output messages when the @value{GDBN} range checker detects a range error,
10966 but attempt to evaluate the expression anyway. Evaluating the
10967 expression may still be impossible for other reasons, such as accessing
10968 memory that the process does not own (a typical example from many Unix
10972 Show the current setting of the range checker, and whether or not it is
10973 being set automatically by @value{GDBN}.
10976 @node Supported Languages
10977 @section Supported Languages
10979 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10980 assembly, Modula-2, and Ada.
10981 @c This is false ...
10982 Some @value{GDBN} features may be used in expressions regardless of the
10983 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10984 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10985 ,Expressions}) can be used with the constructs of any supported
10988 The following sections detail to what degree each source language is
10989 supported by @value{GDBN}. These sections are not meant to be language
10990 tutorials or references, but serve only as a reference guide to what the
10991 @value{GDBN} expression parser accepts, and what input and output
10992 formats should look like for different languages. There are many good
10993 books written on each of these languages; please look to these for a
10994 language reference or tutorial.
10997 * C:: C and C@t{++}
10998 * Objective-C:: Objective-C
10999 * Fortran:: Fortran
11001 * Modula-2:: Modula-2
11006 @subsection C and C@t{++}
11008 @cindex C and C@t{++}
11009 @cindex expressions in C or C@t{++}
11011 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11012 to both languages. Whenever this is the case, we discuss those languages
11016 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11017 @cindex @sc{gnu} C@t{++}
11018 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11019 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11020 effectively, you must compile your C@t{++} programs with a supported
11021 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11022 compiler (@code{aCC}).
11024 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11025 format; if it doesn't work on your system, try the stabs+ debugging
11026 format. You can select those formats explicitly with the @code{g++}
11027 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11028 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11029 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11032 * C Operators:: C and C@t{++} operators
11033 * C Constants:: C and C@t{++} constants
11034 * C Plus Plus Expressions:: C@t{++} expressions
11035 * C Defaults:: Default settings for C and C@t{++}
11036 * C Checks:: C and C@t{++} type and range checks
11037 * Debugging C:: @value{GDBN} and C
11038 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11039 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11043 @subsubsection C and C@t{++} Operators
11045 @cindex C and C@t{++} operators
11047 Operators must be defined on values of specific types. For instance,
11048 @code{+} is defined on numbers, but not on structures. Operators are
11049 often defined on groups of types.
11051 For the purposes of C and C@t{++}, the following definitions hold:
11056 @emph{Integral types} include @code{int} with any of its storage-class
11057 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11060 @emph{Floating-point types} include @code{float}, @code{double}, and
11061 @code{long double} (if supported by the target platform).
11064 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11067 @emph{Scalar types} include all of the above.
11072 The following operators are supported. They are listed here
11073 in order of increasing precedence:
11077 The comma or sequencing operator. Expressions in a comma-separated list
11078 are evaluated from left to right, with the result of the entire
11079 expression being the last expression evaluated.
11082 Assignment. The value of an assignment expression is the value
11083 assigned. Defined on scalar types.
11086 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11087 and translated to @w{@code{@var{a} = @var{a op b}}}.
11088 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11089 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11090 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11093 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11094 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11098 Logical @sc{or}. Defined on integral types.
11101 Logical @sc{and}. Defined on integral types.
11104 Bitwise @sc{or}. Defined on integral types.
11107 Bitwise exclusive-@sc{or}. Defined on integral types.
11110 Bitwise @sc{and}. Defined on integral types.
11113 Equality and inequality. Defined on scalar types. The value of these
11114 expressions is 0 for false and non-zero for true.
11116 @item <@r{, }>@r{, }<=@r{, }>=
11117 Less than, greater than, less than or equal, greater than or equal.
11118 Defined on scalar types. The value of these expressions is 0 for false
11119 and non-zero for true.
11122 left shift, and right shift. Defined on integral types.
11125 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11128 Addition and subtraction. Defined on integral types, floating-point types and
11131 @item *@r{, }/@r{, }%
11132 Multiplication, division, and modulus. Multiplication and division are
11133 defined on integral and floating-point types. Modulus is defined on
11137 Increment and decrement. When appearing before a variable, the
11138 operation is performed before the variable is used in an expression;
11139 when appearing after it, the variable's value is used before the
11140 operation takes place.
11143 Pointer dereferencing. Defined on pointer types. Same precedence as
11147 Address operator. Defined on variables. Same precedence as @code{++}.
11149 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11150 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11151 to examine the address
11152 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11156 Negative. Defined on integral and floating-point types. Same
11157 precedence as @code{++}.
11160 Logical negation. Defined on integral types. Same precedence as
11164 Bitwise complement operator. Defined on integral types. Same precedence as
11169 Structure member, and pointer-to-structure member. For convenience,
11170 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11171 pointer based on the stored type information.
11172 Defined on @code{struct} and @code{union} data.
11175 Dereferences of pointers to members.
11178 Array indexing. @code{@var{a}[@var{i}]} is defined as
11179 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11182 Function parameter list. Same precedence as @code{->}.
11185 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11186 and @code{class} types.
11189 Doubled colons also represent the @value{GDBN} scope operator
11190 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11194 If an operator is redefined in the user code, @value{GDBN} usually
11195 attempts to invoke the redefined version instead of using the operator's
11196 predefined meaning.
11199 @subsubsection C and C@t{++} Constants
11201 @cindex C and C@t{++} constants
11203 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11208 Integer constants are a sequence of digits. Octal constants are
11209 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11210 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11211 @samp{l}, specifying that the constant should be treated as a
11215 Floating point constants are a sequence of digits, followed by a decimal
11216 point, followed by a sequence of digits, and optionally followed by an
11217 exponent. An exponent is of the form:
11218 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11219 sequence of digits. The @samp{+} is optional for positive exponents.
11220 A floating-point constant may also end with a letter @samp{f} or
11221 @samp{F}, specifying that the constant should be treated as being of
11222 the @code{float} (as opposed to the default @code{double}) type; or with
11223 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11227 Enumerated constants consist of enumerated identifiers, or their
11228 integral equivalents.
11231 Character constants are a single character surrounded by single quotes
11232 (@code{'}), or a number---the ordinal value of the corresponding character
11233 (usually its @sc{ascii} value). Within quotes, the single character may
11234 be represented by a letter or by @dfn{escape sequences}, which are of
11235 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11236 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11237 @samp{@var{x}} is a predefined special character---for example,
11238 @samp{\n} for newline.
11241 String constants are a sequence of character constants surrounded by
11242 double quotes (@code{"}). Any valid character constant (as described
11243 above) may appear. Double quotes within the string must be preceded by
11244 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11248 Pointer constants are an integral value. You can also write pointers
11249 to constants using the C operator @samp{&}.
11252 Array constants are comma-separated lists surrounded by braces @samp{@{}
11253 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11254 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11255 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11258 @node C Plus Plus Expressions
11259 @subsubsection C@t{++} Expressions
11261 @cindex expressions in C@t{++}
11262 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11264 @cindex debugging C@t{++} programs
11265 @cindex C@t{++} compilers
11266 @cindex debug formats and C@t{++}
11267 @cindex @value{NGCC} and C@t{++}
11269 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11270 proper compiler and the proper debug format. Currently, @value{GDBN}
11271 works best when debugging C@t{++} code that is compiled with
11272 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11273 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11274 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11275 stabs+ as their default debug format, so you usually don't need to
11276 specify a debug format explicitly. Other compilers and/or debug formats
11277 are likely to work badly or not at all when using @value{GDBN} to debug
11283 @cindex member functions
11285 Member function calls are allowed; you can use expressions like
11288 count = aml->GetOriginal(x, y)
11291 @vindex this@r{, inside C@t{++} member functions}
11292 @cindex namespace in C@t{++}
11294 While a member function is active (in the selected stack frame), your
11295 expressions have the same namespace available as the member function;
11296 that is, @value{GDBN} allows implicit references to the class instance
11297 pointer @code{this} following the same rules as C@t{++}.
11299 @cindex call overloaded functions
11300 @cindex overloaded functions, calling
11301 @cindex type conversions in C@t{++}
11303 You can call overloaded functions; @value{GDBN} resolves the function
11304 call to the right definition, with some restrictions. @value{GDBN} does not
11305 perform overload resolution involving user-defined type conversions,
11306 calls to constructors, or instantiations of templates that do not exist
11307 in the program. It also cannot handle ellipsis argument lists or
11310 It does perform integral conversions and promotions, floating-point
11311 promotions, arithmetic conversions, pointer conversions, conversions of
11312 class objects to base classes, and standard conversions such as those of
11313 functions or arrays to pointers; it requires an exact match on the
11314 number of function arguments.
11316 Overload resolution is always performed, unless you have specified
11317 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11318 ,@value{GDBN} Features for C@t{++}}.
11320 You must specify @code{set overload-resolution off} in order to use an
11321 explicit function signature to call an overloaded function, as in
11323 p 'foo(char,int)'('x', 13)
11326 The @value{GDBN} command-completion facility can simplify this;
11327 see @ref{Completion, ,Command Completion}.
11329 @cindex reference declarations
11331 @value{GDBN} understands variables declared as C@t{++} references; you can use
11332 them in expressions just as you do in C@t{++} source---they are automatically
11335 In the parameter list shown when @value{GDBN} displays a frame, the values of
11336 reference variables are not displayed (unlike other variables); this
11337 avoids clutter, since references are often used for large structures.
11338 The @emph{address} of a reference variable is always shown, unless
11339 you have specified @samp{set print address off}.
11342 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11343 expressions can use it just as expressions in your program do. Since
11344 one scope may be defined in another, you can use @code{::} repeatedly if
11345 necessary, for example in an expression like
11346 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11347 resolving name scope by reference to source files, in both C and C@t{++}
11348 debugging (@pxref{Variables, ,Program Variables}).
11351 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11352 calling virtual functions correctly, printing out virtual bases of
11353 objects, calling functions in a base subobject, casting objects, and
11354 invoking user-defined operators.
11357 @subsubsection C and C@t{++} Defaults
11359 @cindex C and C@t{++} defaults
11361 If you allow @value{GDBN} to set type and range checking automatically, they
11362 both default to @code{off} whenever the working language changes to
11363 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11364 selects the working language.
11366 If you allow @value{GDBN} to set the language automatically, it
11367 recognizes source files whose names end with @file{.c}, @file{.C}, or
11368 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11369 these files, it sets the working language to C or C@t{++}.
11370 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11371 for further details.
11373 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11374 @c unimplemented. If (b) changes, it might make sense to let this node
11375 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11378 @subsubsection C and C@t{++} Type and Range Checks
11380 @cindex C and C@t{++} checks
11382 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11383 is not used. However, if you turn type checking on, @value{GDBN}
11384 considers two variables type equivalent if:
11388 The two variables are structured and have the same structure, union, or
11392 The two variables have the same type name, or types that have been
11393 declared equivalent through @code{typedef}.
11396 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11399 The two @code{struct}, @code{union}, or @code{enum} variables are
11400 declared in the same declaration. (Note: this may not be true for all C
11405 Range checking, if turned on, is done on mathematical operations. Array
11406 indices are not checked, since they are often used to index a pointer
11407 that is not itself an array.
11410 @subsubsection @value{GDBN} and C
11412 The @code{set print union} and @code{show print union} commands apply to
11413 the @code{union} type. When set to @samp{on}, any @code{union} that is
11414 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11415 appears as @samp{@{...@}}.
11417 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11418 with pointers and a memory allocation function. @xref{Expressions,
11421 @node Debugging C Plus Plus
11422 @subsubsection @value{GDBN} Features for C@t{++}
11424 @cindex commands for C@t{++}
11426 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11427 designed specifically for use with C@t{++}. Here is a summary:
11430 @cindex break in overloaded functions
11431 @item @r{breakpoint menus}
11432 When you want a breakpoint in a function whose name is overloaded,
11433 @value{GDBN} has the capability to display a menu of possible breakpoint
11434 locations to help you specify which function definition you want.
11435 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11437 @cindex overloading in C@t{++}
11438 @item rbreak @var{regex}
11439 Setting breakpoints using regular expressions is helpful for setting
11440 breakpoints on overloaded functions that are not members of any special
11442 @xref{Set Breaks, ,Setting Breakpoints}.
11444 @cindex C@t{++} exception handling
11447 Debug C@t{++} exception handling using these commands. @xref{Set
11448 Catchpoints, , Setting Catchpoints}.
11450 @cindex inheritance
11451 @item ptype @var{typename}
11452 Print inheritance relationships as well as other information for type
11454 @xref{Symbols, ,Examining the Symbol Table}.
11456 @cindex C@t{++} symbol display
11457 @item set print demangle
11458 @itemx show print demangle
11459 @itemx set print asm-demangle
11460 @itemx show print asm-demangle
11461 Control whether C@t{++} symbols display in their source form, both when
11462 displaying code as C@t{++} source and when displaying disassemblies.
11463 @xref{Print Settings, ,Print Settings}.
11465 @item set print object
11466 @itemx show print object
11467 Choose whether to print derived (actual) or declared types of objects.
11468 @xref{Print Settings, ,Print Settings}.
11470 @item set print vtbl
11471 @itemx show print vtbl
11472 Control the format for printing virtual function tables.
11473 @xref{Print Settings, ,Print Settings}.
11474 (The @code{vtbl} commands do not work on programs compiled with the HP
11475 ANSI C@t{++} compiler (@code{aCC}).)
11477 @kindex set overload-resolution
11478 @cindex overloaded functions, overload resolution
11479 @item set overload-resolution on
11480 Enable overload resolution for C@t{++} expression evaluation. The default
11481 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11482 and searches for a function whose signature matches the argument types,
11483 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11484 Expressions, ,C@t{++} Expressions}, for details).
11485 If it cannot find a match, it emits a message.
11487 @item set overload-resolution off
11488 Disable overload resolution for C@t{++} expression evaluation. For
11489 overloaded functions that are not class member functions, @value{GDBN}
11490 chooses the first function of the specified name that it finds in the
11491 symbol table, whether or not its arguments are of the correct type. For
11492 overloaded functions that are class member functions, @value{GDBN}
11493 searches for a function whose signature @emph{exactly} matches the
11496 @kindex show overload-resolution
11497 @item show overload-resolution
11498 Show the current setting of overload resolution.
11500 @item @r{Overloaded symbol names}
11501 You can specify a particular definition of an overloaded symbol, using
11502 the same notation that is used to declare such symbols in C@t{++}: type
11503 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11504 also use the @value{GDBN} command-line word completion facilities to list the
11505 available choices, or to finish the type list for you.
11506 @xref{Completion,, Command Completion}, for details on how to do this.
11509 @node Decimal Floating Point
11510 @subsubsection Decimal Floating Point format
11511 @cindex decimal floating point format
11513 @value{GDBN} can examine, set and perform computations with numbers in
11514 decimal floating point format, which in the C language correspond to the
11515 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11516 specified by the extension to support decimal floating-point arithmetic.
11518 There are two encodings in use, depending on the architecture: BID (Binary
11519 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11520 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11523 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11524 to manipulate decimal floating point numbers, it is not possible to convert
11525 (using a cast, for example) integers wider than 32-bit to decimal float.
11527 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11528 point computations, error checking in decimal float operations ignores
11529 underflow, overflow and divide by zero exceptions.
11531 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11532 to inspect @code{_Decimal128} values stored in floating point registers.
11533 See @ref{PowerPC,,PowerPC} for more details.
11536 @subsection Objective-C
11538 @cindex Objective-C
11539 This section provides information about some commands and command
11540 options that are useful for debugging Objective-C code. See also
11541 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11542 few more commands specific to Objective-C support.
11545 * Method Names in Commands::
11546 * The Print Command with Objective-C::
11549 @node Method Names in Commands
11550 @subsubsection Method Names in Commands
11552 The following commands have been extended to accept Objective-C method
11553 names as line specifications:
11555 @kindex clear@r{, and Objective-C}
11556 @kindex break@r{, and Objective-C}
11557 @kindex info line@r{, and Objective-C}
11558 @kindex jump@r{, and Objective-C}
11559 @kindex list@r{, and Objective-C}
11563 @item @code{info line}
11568 A fully qualified Objective-C method name is specified as
11571 -[@var{Class} @var{methodName}]
11574 where the minus sign is used to indicate an instance method and a
11575 plus sign (not shown) is used to indicate a class method. The class
11576 name @var{Class} and method name @var{methodName} are enclosed in
11577 brackets, similar to the way messages are specified in Objective-C
11578 source code. For example, to set a breakpoint at the @code{create}
11579 instance method of class @code{Fruit} in the program currently being
11583 break -[Fruit create]
11586 To list ten program lines around the @code{initialize} class method,
11590 list +[NSText initialize]
11593 In the current version of @value{GDBN}, the plus or minus sign is
11594 required. In future versions of @value{GDBN}, the plus or minus
11595 sign will be optional, but you can use it to narrow the search. It
11596 is also possible to specify just a method name:
11602 You must specify the complete method name, including any colons. If
11603 your program's source files contain more than one @code{create} method,
11604 you'll be presented with a numbered list of classes that implement that
11605 method. Indicate your choice by number, or type @samp{0} to exit if
11608 As another example, to clear a breakpoint established at the
11609 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11612 clear -[NSWindow makeKeyAndOrderFront:]
11615 @node The Print Command with Objective-C
11616 @subsubsection The Print Command With Objective-C
11617 @cindex Objective-C, print objects
11618 @kindex print-object
11619 @kindex po @r{(@code{print-object})}
11621 The print command has also been extended to accept methods. For example:
11624 print -[@var{object} hash]
11627 @cindex print an Objective-C object description
11628 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11630 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11631 and print the result. Also, an additional command has been added,
11632 @code{print-object} or @code{po} for short, which is meant to print
11633 the description of an object. However, this command may only work
11634 with certain Objective-C libraries that have a particular hook
11635 function, @code{_NSPrintForDebugger}, defined.
11638 @subsection Fortran
11639 @cindex Fortran-specific support in @value{GDBN}
11641 @value{GDBN} can be used to debug programs written in Fortran, but it
11642 currently supports only the features of Fortran 77 language.
11644 @cindex trailing underscore, in Fortran symbols
11645 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11646 among them) append an underscore to the names of variables and
11647 functions. When you debug programs compiled by those compilers, you
11648 will need to refer to variables and functions with a trailing
11652 * Fortran Operators:: Fortran operators and expressions
11653 * Fortran Defaults:: Default settings for Fortran
11654 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11657 @node Fortran Operators
11658 @subsubsection Fortran Operators and Expressions
11660 @cindex Fortran operators and expressions
11662 Operators must be defined on values of specific types. For instance,
11663 @code{+} is defined on numbers, but not on characters or other non-
11664 arithmetic types. Operators are often defined on groups of types.
11668 The exponentiation operator. It raises the first operand to the power
11672 The range operator. Normally used in the form of array(low:high) to
11673 represent a section of array.
11676 The access component operator. Normally used to access elements in derived
11677 types. Also suitable for unions. As unions aren't part of regular Fortran,
11678 this can only happen when accessing a register that uses a gdbarch-defined
11682 @node Fortran Defaults
11683 @subsubsection Fortran Defaults
11685 @cindex Fortran Defaults
11687 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11688 default uses case-insensitive matches for Fortran symbols. You can
11689 change that with the @samp{set case-insensitive} command, see
11690 @ref{Symbols}, for the details.
11692 @node Special Fortran Commands
11693 @subsubsection Special Fortran Commands
11695 @cindex Special Fortran commands
11697 @value{GDBN} has some commands to support Fortran-specific features,
11698 such as displaying common blocks.
11701 @cindex @code{COMMON} blocks, Fortran
11702 @kindex info common
11703 @item info common @r{[}@var{common-name}@r{]}
11704 This command prints the values contained in the Fortran @code{COMMON}
11705 block whose name is @var{common-name}. With no argument, the names of
11706 all @code{COMMON} blocks visible at the current program location are
11713 @cindex Pascal support in @value{GDBN}, limitations
11714 Debugging Pascal programs which use sets, subranges, file variables, or
11715 nested functions does not currently work. @value{GDBN} does not support
11716 entering expressions, printing values, or similar features using Pascal
11719 The Pascal-specific command @code{set print pascal_static-members}
11720 controls whether static members of Pascal objects are displayed.
11721 @xref{Print Settings, pascal_static-members}.
11724 @subsection Modula-2
11726 @cindex Modula-2, @value{GDBN} support
11728 The extensions made to @value{GDBN} to support Modula-2 only support
11729 output from the @sc{gnu} Modula-2 compiler (which is currently being
11730 developed). Other Modula-2 compilers are not currently supported, and
11731 attempting to debug executables produced by them is most likely
11732 to give an error as @value{GDBN} reads in the executable's symbol
11735 @cindex expressions in Modula-2
11737 * M2 Operators:: Built-in operators
11738 * Built-In Func/Proc:: Built-in functions and procedures
11739 * M2 Constants:: Modula-2 constants
11740 * M2 Types:: Modula-2 types
11741 * M2 Defaults:: Default settings for Modula-2
11742 * Deviations:: Deviations from standard Modula-2
11743 * M2 Checks:: Modula-2 type and range checks
11744 * M2 Scope:: The scope operators @code{::} and @code{.}
11745 * GDB/M2:: @value{GDBN} and Modula-2
11749 @subsubsection Operators
11750 @cindex Modula-2 operators
11752 Operators must be defined on values of specific types. For instance,
11753 @code{+} is defined on numbers, but not on structures. Operators are
11754 often defined on groups of types. For the purposes of Modula-2, the
11755 following definitions hold:
11760 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11764 @emph{Character types} consist of @code{CHAR} and its subranges.
11767 @emph{Floating-point types} consist of @code{REAL}.
11770 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11774 @emph{Scalar types} consist of all of the above.
11777 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11780 @emph{Boolean types} consist of @code{BOOLEAN}.
11784 The following operators are supported, and appear in order of
11785 increasing precedence:
11789 Function argument or array index separator.
11792 Assignment. The value of @var{var} @code{:=} @var{value} is
11796 Less than, greater than on integral, floating-point, or enumerated
11800 Less than or equal to, greater than or equal to
11801 on integral, floating-point and enumerated types, or set inclusion on
11802 set types. Same precedence as @code{<}.
11804 @item =@r{, }<>@r{, }#
11805 Equality and two ways of expressing inequality, valid on scalar types.
11806 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11807 available for inequality, since @code{#} conflicts with the script
11811 Set membership. Defined on set types and the types of their members.
11812 Same precedence as @code{<}.
11815 Boolean disjunction. Defined on boolean types.
11818 Boolean conjunction. Defined on boolean types.
11821 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11824 Addition and subtraction on integral and floating-point types, or union
11825 and difference on set types.
11828 Multiplication on integral and floating-point types, or set intersection
11832 Division on floating-point types, or symmetric set difference on set
11833 types. Same precedence as @code{*}.
11836 Integer division and remainder. Defined on integral types. Same
11837 precedence as @code{*}.
11840 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11843 Pointer dereferencing. Defined on pointer types.
11846 Boolean negation. Defined on boolean types. Same precedence as
11850 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11851 precedence as @code{^}.
11854 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11857 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11861 @value{GDBN} and Modula-2 scope operators.
11865 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11866 treats the use of the operator @code{IN}, or the use of operators
11867 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11868 @code{<=}, and @code{>=} on sets as an error.
11872 @node Built-In Func/Proc
11873 @subsubsection Built-in Functions and Procedures
11874 @cindex Modula-2 built-ins
11876 Modula-2 also makes available several built-in procedures and functions.
11877 In describing these, the following metavariables are used:
11882 represents an @code{ARRAY} variable.
11885 represents a @code{CHAR} constant or variable.
11888 represents a variable or constant of integral type.
11891 represents an identifier that belongs to a set. Generally used in the
11892 same function with the metavariable @var{s}. The type of @var{s} should
11893 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11896 represents a variable or constant of integral or floating-point type.
11899 represents a variable or constant of floating-point type.
11905 represents a variable.
11908 represents a variable or constant of one of many types. See the
11909 explanation of the function for details.
11912 All Modula-2 built-in procedures also return a result, described below.
11916 Returns the absolute value of @var{n}.
11919 If @var{c} is a lower case letter, it returns its upper case
11920 equivalent, otherwise it returns its argument.
11923 Returns the character whose ordinal value is @var{i}.
11926 Decrements the value in the variable @var{v} by one. Returns the new value.
11928 @item DEC(@var{v},@var{i})
11929 Decrements the value in the variable @var{v} by @var{i}. Returns the
11932 @item EXCL(@var{m},@var{s})
11933 Removes the element @var{m} from the set @var{s}. Returns the new
11936 @item FLOAT(@var{i})
11937 Returns the floating point equivalent of the integer @var{i}.
11939 @item HIGH(@var{a})
11940 Returns the index of the last member of @var{a}.
11943 Increments the value in the variable @var{v} by one. Returns the new value.
11945 @item INC(@var{v},@var{i})
11946 Increments the value in the variable @var{v} by @var{i}. Returns the
11949 @item INCL(@var{m},@var{s})
11950 Adds the element @var{m} to the set @var{s} if it is not already
11951 there. Returns the new set.
11954 Returns the maximum value of the type @var{t}.
11957 Returns the minimum value of the type @var{t}.
11960 Returns boolean TRUE if @var{i} is an odd number.
11963 Returns the ordinal value of its argument. For example, the ordinal
11964 value of a character is its @sc{ascii} value (on machines supporting the
11965 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11966 integral, character and enumerated types.
11968 @item SIZE(@var{x})
11969 Returns the size of its argument. @var{x} can be a variable or a type.
11971 @item TRUNC(@var{r})
11972 Returns the integral part of @var{r}.
11974 @item TSIZE(@var{x})
11975 Returns the size of its argument. @var{x} can be a variable or a type.
11977 @item VAL(@var{t},@var{i})
11978 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11982 @emph{Warning:} Sets and their operations are not yet supported, so
11983 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11987 @cindex Modula-2 constants
11989 @subsubsection Constants
11991 @value{GDBN} allows you to express the constants of Modula-2 in the following
11997 Integer constants are simply a sequence of digits. When used in an
11998 expression, a constant is interpreted to be type-compatible with the
11999 rest of the expression. Hexadecimal integers are specified by a
12000 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12003 Floating point constants appear as a sequence of digits, followed by a
12004 decimal point and another sequence of digits. An optional exponent can
12005 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12006 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12007 digits of the floating point constant must be valid decimal (base 10)
12011 Character constants consist of a single character enclosed by a pair of
12012 like quotes, either single (@code{'}) or double (@code{"}). They may
12013 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12014 followed by a @samp{C}.
12017 String constants consist of a sequence of characters enclosed by a
12018 pair of like quotes, either single (@code{'}) or double (@code{"}).
12019 Escape sequences in the style of C are also allowed. @xref{C
12020 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12024 Enumerated constants consist of an enumerated identifier.
12027 Boolean constants consist of the identifiers @code{TRUE} and
12031 Pointer constants consist of integral values only.
12034 Set constants are not yet supported.
12038 @subsubsection Modula-2 Types
12039 @cindex Modula-2 types
12041 Currently @value{GDBN} can print the following data types in Modula-2
12042 syntax: array types, record types, set types, pointer types, procedure
12043 types, enumerated types, subrange types and base types. You can also
12044 print the contents of variables declared using these type.
12045 This section gives a number of simple source code examples together with
12046 sample @value{GDBN} sessions.
12048 The first example contains the following section of code:
12057 and you can request @value{GDBN} to interrogate the type and value of
12058 @code{r} and @code{s}.
12061 (@value{GDBP}) print s
12063 (@value{GDBP}) ptype s
12065 (@value{GDBP}) print r
12067 (@value{GDBP}) ptype r
12072 Likewise if your source code declares @code{s} as:
12076 s: SET ['A'..'Z'] ;
12080 then you may query the type of @code{s} by:
12083 (@value{GDBP}) ptype s
12084 type = SET ['A'..'Z']
12088 Note that at present you cannot interactively manipulate set
12089 expressions using the debugger.
12091 The following example shows how you might declare an array in Modula-2
12092 and how you can interact with @value{GDBN} to print its type and contents:
12096 s: ARRAY [-10..10] OF CHAR ;
12100 (@value{GDBP}) ptype s
12101 ARRAY [-10..10] OF CHAR
12104 Note that the array handling is not yet complete and although the type
12105 is printed correctly, expression handling still assumes that all
12106 arrays have a lower bound of zero and not @code{-10} as in the example
12109 Here are some more type related Modula-2 examples:
12113 colour = (blue, red, yellow, green) ;
12114 t = [blue..yellow] ;
12122 The @value{GDBN} interaction shows how you can query the data type
12123 and value of a variable.
12126 (@value{GDBP}) print s
12128 (@value{GDBP}) ptype t
12129 type = [blue..yellow]
12133 In this example a Modula-2 array is declared and its contents
12134 displayed. Observe that the contents are written in the same way as
12135 their @code{C} counterparts.
12139 s: ARRAY [1..5] OF CARDINAL ;
12145 (@value{GDBP}) print s
12146 $1 = @{1, 0, 0, 0, 0@}
12147 (@value{GDBP}) ptype s
12148 type = ARRAY [1..5] OF CARDINAL
12151 The Modula-2 language interface to @value{GDBN} also understands
12152 pointer types as shown in this example:
12156 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12163 and you can request that @value{GDBN} describes the type of @code{s}.
12166 (@value{GDBP}) ptype s
12167 type = POINTER TO ARRAY [1..5] OF CARDINAL
12170 @value{GDBN} handles compound types as we can see in this example.
12171 Here we combine array types, record types, pointer types and subrange
12182 myarray = ARRAY myrange OF CARDINAL ;
12183 myrange = [-2..2] ;
12185 s: POINTER TO ARRAY myrange OF foo ;
12189 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12193 (@value{GDBP}) ptype s
12194 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12197 f3 : ARRAY [-2..2] OF CARDINAL;
12202 @subsubsection Modula-2 Defaults
12203 @cindex Modula-2 defaults
12205 If type and range checking are set automatically by @value{GDBN}, they
12206 both default to @code{on} whenever the working language changes to
12207 Modula-2. This happens regardless of whether you or @value{GDBN}
12208 selected the working language.
12210 If you allow @value{GDBN} to set the language automatically, then entering
12211 code compiled from a file whose name ends with @file{.mod} sets the
12212 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12213 Infer the Source Language}, for further details.
12216 @subsubsection Deviations from Standard Modula-2
12217 @cindex Modula-2, deviations from
12219 A few changes have been made to make Modula-2 programs easier to debug.
12220 This is done primarily via loosening its type strictness:
12224 Unlike in standard Modula-2, pointer constants can be formed by
12225 integers. This allows you to modify pointer variables during
12226 debugging. (In standard Modula-2, the actual address contained in a
12227 pointer variable is hidden from you; it can only be modified
12228 through direct assignment to another pointer variable or expression that
12229 returned a pointer.)
12232 C escape sequences can be used in strings and characters to represent
12233 non-printable characters. @value{GDBN} prints out strings with these
12234 escape sequences embedded. Single non-printable characters are
12235 printed using the @samp{CHR(@var{nnn})} format.
12238 The assignment operator (@code{:=}) returns the value of its right-hand
12242 All built-in procedures both modify @emph{and} return their argument.
12246 @subsubsection Modula-2 Type and Range Checks
12247 @cindex Modula-2 checks
12250 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12253 @c FIXME remove warning when type/range checks added
12255 @value{GDBN} considers two Modula-2 variables type equivalent if:
12259 They are of types that have been declared equivalent via a @code{TYPE
12260 @var{t1} = @var{t2}} statement
12263 They have been declared on the same line. (Note: This is true of the
12264 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12267 As long as type checking is enabled, any attempt to combine variables
12268 whose types are not equivalent is an error.
12270 Range checking is done on all mathematical operations, assignment, array
12271 index bounds, and all built-in functions and procedures.
12274 @subsubsection The Scope Operators @code{::} and @code{.}
12276 @cindex @code{.}, Modula-2 scope operator
12277 @cindex colon, doubled as scope operator
12279 @vindex colon-colon@r{, in Modula-2}
12280 @c Info cannot handle :: but TeX can.
12283 @vindex ::@r{, in Modula-2}
12286 There are a few subtle differences between the Modula-2 scope operator
12287 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12292 @var{module} . @var{id}
12293 @var{scope} :: @var{id}
12297 where @var{scope} is the name of a module or a procedure,
12298 @var{module} the name of a module, and @var{id} is any declared
12299 identifier within your program, except another module.
12301 Using the @code{::} operator makes @value{GDBN} search the scope
12302 specified by @var{scope} for the identifier @var{id}. If it is not
12303 found in the specified scope, then @value{GDBN} searches all scopes
12304 enclosing the one specified by @var{scope}.
12306 Using the @code{.} operator makes @value{GDBN} search the current scope for
12307 the identifier specified by @var{id} that was imported from the
12308 definition module specified by @var{module}. With this operator, it is
12309 an error if the identifier @var{id} was not imported from definition
12310 module @var{module}, or if @var{id} is not an identifier in
12314 @subsubsection @value{GDBN} and Modula-2
12316 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12317 Five subcommands of @code{set print} and @code{show print} apply
12318 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12319 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12320 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12321 analogue in Modula-2.
12323 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12324 with any language, is not useful with Modula-2. Its
12325 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12326 created in Modula-2 as they can in C or C@t{++}. However, because an
12327 address can be specified by an integral constant, the construct
12328 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12330 @cindex @code{#} in Modula-2
12331 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12332 interpreted as the beginning of a comment. Use @code{<>} instead.
12338 The extensions made to @value{GDBN} for Ada only support
12339 output from the @sc{gnu} Ada (GNAT) compiler.
12340 Other Ada compilers are not currently supported, and
12341 attempting to debug executables produced by them is most likely
12345 @cindex expressions in Ada
12347 * Ada Mode Intro:: General remarks on the Ada syntax
12348 and semantics supported by Ada mode
12350 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12351 * Additions to Ada:: Extensions of the Ada expression syntax.
12352 * Stopping Before Main Program:: Debugging the program during elaboration.
12353 * Ada Tasks:: Listing and setting breakpoints in tasks.
12354 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12355 * Ada Glitches:: Known peculiarities of Ada mode.
12358 @node Ada Mode Intro
12359 @subsubsection Introduction
12360 @cindex Ada mode, general
12362 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12363 syntax, with some extensions.
12364 The philosophy behind the design of this subset is
12368 That @value{GDBN} should provide basic literals and access to operations for
12369 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12370 leaving more sophisticated computations to subprograms written into the
12371 program (which therefore may be called from @value{GDBN}).
12374 That type safety and strict adherence to Ada language restrictions
12375 are not particularly important to the @value{GDBN} user.
12378 That brevity is important to the @value{GDBN} user.
12381 Thus, for brevity, the debugger acts as if all names declared in
12382 user-written packages are directly visible, even if they are not visible
12383 according to Ada rules, thus making it unnecessary to fully qualify most
12384 names with their packages, regardless of context. Where this causes
12385 ambiguity, @value{GDBN} asks the user's intent.
12387 The debugger will start in Ada mode if it detects an Ada main program.
12388 As for other languages, it will enter Ada mode when stopped in a program that
12389 was translated from an Ada source file.
12391 While in Ada mode, you may use `@t{--}' for comments. This is useful
12392 mostly for documenting command files. The standard @value{GDBN} comment
12393 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12394 middle (to allow based literals).
12396 The debugger supports limited overloading. Given a subprogram call in which
12397 the function symbol has multiple definitions, it will use the number of
12398 actual parameters and some information about their types to attempt to narrow
12399 the set of definitions. It also makes very limited use of context, preferring
12400 procedures to functions in the context of the @code{call} command, and
12401 functions to procedures elsewhere.
12403 @node Omissions from Ada
12404 @subsubsection Omissions from Ada
12405 @cindex Ada, omissions from
12407 Here are the notable omissions from the subset:
12411 Only a subset of the attributes are supported:
12415 @t{'First}, @t{'Last}, and @t{'Length}
12416 on array objects (not on types and subtypes).
12419 @t{'Min} and @t{'Max}.
12422 @t{'Pos} and @t{'Val}.
12428 @t{'Range} on array objects (not subtypes), but only as the right
12429 operand of the membership (@code{in}) operator.
12432 @t{'Access}, @t{'Unchecked_Access}, and
12433 @t{'Unrestricted_Access} (a GNAT extension).
12441 @code{Characters.Latin_1} are not available and
12442 concatenation is not implemented. Thus, escape characters in strings are
12443 not currently available.
12446 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12447 equality of representations. They will generally work correctly
12448 for strings and arrays whose elements have integer or enumeration types.
12449 They may not work correctly for arrays whose element
12450 types have user-defined equality, for arrays of real values
12451 (in particular, IEEE-conformant floating point, because of negative
12452 zeroes and NaNs), and for arrays whose elements contain unused bits with
12453 indeterminate values.
12456 The other component-by-component array operations (@code{and}, @code{or},
12457 @code{xor}, @code{not}, and relational tests other than equality)
12458 are not implemented.
12461 @cindex array aggregates (Ada)
12462 @cindex record aggregates (Ada)
12463 @cindex aggregates (Ada)
12464 There is limited support for array and record aggregates. They are
12465 permitted only on the right sides of assignments, as in these examples:
12468 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12469 (@value{GDBP}) set An_Array := (1, others => 0)
12470 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12471 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12472 (@value{GDBP}) set A_Record := (1, "Peter", True);
12473 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12477 discriminant's value by assigning an aggregate has an
12478 undefined effect if that discriminant is used within the record.
12479 However, you can first modify discriminants by directly assigning to
12480 them (which normally would not be allowed in Ada), and then performing an
12481 aggregate assignment. For example, given a variable @code{A_Rec}
12482 declared to have a type such as:
12485 type Rec (Len : Small_Integer := 0) is record
12487 Vals : IntArray (1 .. Len);
12491 you can assign a value with a different size of @code{Vals} with two
12495 (@value{GDBP}) set A_Rec.Len := 4
12496 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12499 As this example also illustrates, @value{GDBN} is very loose about the usual
12500 rules concerning aggregates. You may leave out some of the
12501 components of an array or record aggregate (such as the @code{Len}
12502 component in the assignment to @code{A_Rec} above); they will retain their
12503 original values upon assignment. You may freely use dynamic values as
12504 indices in component associations. You may even use overlapping or
12505 redundant component associations, although which component values are
12506 assigned in such cases is not defined.
12509 Calls to dispatching subprograms are not implemented.
12512 The overloading algorithm is much more limited (i.e., less selective)
12513 than that of real Ada. It makes only limited use of the context in
12514 which a subexpression appears to resolve its meaning, and it is much
12515 looser in its rules for allowing type matches. As a result, some
12516 function calls will be ambiguous, and the user will be asked to choose
12517 the proper resolution.
12520 The @code{new} operator is not implemented.
12523 Entry calls are not implemented.
12526 Aside from printing, arithmetic operations on the native VAX floating-point
12527 formats are not supported.
12530 It is not possible to slice a packed array.
12533 The names @code{True} and @code{False}, when not part of a qualified name,
12534 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12536 Should your program
12537 redefine these names in a package or procedure (at best a dubious practice),
12538 you will have to use fully qualified names to access their new definitions.
12541 @node Additions to Ada
12542 @subsubsection Additions to Ada
12543 @cindex Ada, deviations from
12545 As it does for other languages, @value{GDBN} makes certain generic
12546 extensions to Ada (@pxref{Expressions}):
12550 If the expression @var{E} is a variable residing in memory (typically
12551 a local variable or array element) and @var{N} is a positive integer,
12552 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12553 @var{N}-1 adjacent variables following it in memory as an array. In
12554 Ada, this operator is generally not necessary, since its prime use is
12555 in displaying parts of an array, and slicing will usually do this in
12556 Ada. However, there are occasional uses when debugging programs in
12557 which certain debugging information has been optimized away.
12560 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12561 appears in function or file @var{B}.'' When @var{B} is a file name,
12562 you must typically surround it in single quotes.
12565 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12566 @var{type} that appears at address @var{addr}.''
12569 A name starting with @samp{$} is a convenience variable
12570 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12573 In addition, @value{GDBN} provides a few other shortcuts and outright
12574 additions specific to Ada:
12578 The assignment statement is allowed as an expression, returning
12579 its right-hand operand as its value. Thus, you may enter
12582 (@value{GDBP}) set x := y + 3
12583 (@value{GDBP}) print A(tmp := y + 1)
12587 The semicolon is allowed as an ``operator,'' returning as its value
12588 the value of its right-hand operand.
12589 This allows, for example,
12590 complex conditional breaks:
12593 (@value{GDBP}) break f
12594 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12598 Rather than use catenation and symbolic character names to introduce special
12599 characters into strings, one may instead use a special bracket notation,
12600 which is also used to print strings. A sequence of characters of the form
12601 @samp{["@var{XX}"]} within a string or character literal denotes the
12602 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12603 sequence of characters @samp{["""]} also denotes a single quotation mark
12604 in strings. For example,
12606 "One line.["0a"]Next line.["0a"]"
12609 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12613 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12614 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12618 (@value{GDBP}) print 'max(x, y)
12622 When printing arrays, @value{GDBN} uses positional notation when the
12623 array has a lower bound of 1, and uses a modified named notation otherwise.
12624 For example, a one-dimensional array of three integers with a lower bound
12625 of 3 might print as
12632 That is, in contrast to valid Ada, only the first component has a @code{=>}
12636 You may abbreviate attributes in expressions with any unique,
12637 multi-character subsequence of
12638 their names (an exact match gets preference).
12639 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12640 in place of @t{a'length}.
12643 @cindex quoting Ada internal identifiers
12644 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12645 to lower case. The GNAT compiler uses upper-case characters for
12646 some of its internal identifiers, which are normally of no interest to users.
12647 For the rare occasions when you actually have to look at them,
12648 enclose them in angle brackets to avoid the lower-case mapping.
12651 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12655 Printing an object of class-wide type or dereferencing an
12656 access-to-class-wide value will display all the components of the object's
12657 specific type (as indicated by its run-time tag). Likewise, component
12658 selection on such a value will operate on the specific type of the
12663 @node Stopping Before Main Program
12664 @subsubsection Stopping at the Very Beginning
12666 @cindex breakpointing Ada elaboration code
12667 It is sometimes necessary to debug the program during elaboration, and
12668 before reaching the main procedure.
12669 As defined in the Ada Reference
12670 Manual, the elaboration code is invoked from a procedure called
12671 @code{adainit}. To run your program up to the beginning of
12672 elaboration, simply use the following two commands:
12673 @code{tbreak adainit} and @code{run}.
12676 @subsubsection Extensions for Ada Tasks
12677 @cindex Ada, tasking
12679 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12680 @value{GDBN} provides the following task-related commands:
12685 This command shows a list of current Ada tasks, as in the following example:
12692 (@value{GDBP}) info tasks
12693 ID TID P-ID Pri State Name
12694 1 8088000 0 15 Child Activation Wait main_task
12695 2 80a4000 1 15 Accept Statement b
12696 3 809a800 1 15 Child Activation Wait a
12697 * 4 80ae800 3 15 Runnable c
12702 In this listing, the asterisk before the last task indicates it to be the
12703 task currently being inspected.
12707 Represents @value{GDBN}'s internal task number.
12713 The parent's task ID (@value{GDBN}'s internal task number).
12716 The base priority of the task.
12719 Current state of the task.
12723 The task has been created but has not been activated. It cannot be
12727 The task is not blocked for any reason known to Ada. (It may be waiting
12728 for a mutex, though.) It is conceptually "executing" in normal mode.
12731 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12732 that were waiting on terminate alternatives have been awakened and have
12733 terminated themselves.
12735 @item Child Activation Wait
12736 The task is waiting for created tasks to complete activation.
12738 @item Accept Statement
12739 The task is waiting on an accept or selective wait statement.
12741 @item Waiting on entry call
12742 The task is waiting on an entry call.
12744 @item Async Select Wait
12745 The task is waiting to start the abortable part of an asynchronous
12749 The task is waiting on a select statement with only a delay
12752 @item Child Termination Wait
12753 The task is sleeping having completed a master within itself, and is
12754 waiting for the tasks dependent on that master to become terminated or
12755 waiting on a terminate Phase.
12757 @item Wait Child in Term Alt
12758 The task is sleeping waiting for tasks on terminate alternatives to
12759 finish terminating.
12761 @item Accepting RV with @var{taskno}
12762 The task is accepting a rendez-vous with the task @var{taskno}.
12766 Name of the task in the program.
12770 @kindex info task @var{taskno}
12771 @item info task @var{taskno}
12772 This command shows detailled informations on the specified task, as in
12773 the following example:
12778 (@value{GDBP}) info tasks
12779 ID TID P-ID Pri State Name
12780 1 8077880 0 15 Child Activation Wait main_task
12781 * 2 807c468 1 15 Runnable task_1
12782 (@value{GDBP}) info task 2
12783 Ada Task: 0x807c468
12786 Parent: 1 (main_task)
12792 @kindex task@r{ (Ada)}
12793 @cindex current Ada task ID
12794 This command prints the ID of the current task.
12800 (@value{GDBP}) info tasks
12801 ID TID P-ID Pri State Name
12802 1 8077870 0 15 Child Activation Wait main_task
12803 * 2 807c458 1 15 Runnable t
12804 (@value{GDBP}) task
12805 [Current task is 2]
12808 @item task @var{taskno}
12809 @cindex Ada task switching
12810 This command is like the @code{thread @var{threadno}}
12811 command (@pxref{Threads}). It switches the context of debugging
12812 from the current task to the given task.
12818 (@value{GDBP}) info tasks
12819 ID TID P-ID Pri State Name
12820 1 8077870 0 15 Child Activation Wait main_task
12821 * 2 807c458 1 15 Runnable t
12822 (@value{GDBP}) task 1
12823 [Switching to task 1]
12824 #0 0x8067726 in pthread_cond_wait ()
12826 #0 0x8067726 in pthread_cond_wait ()
12827 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12828 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12829 #3 0x806153e in system.tasking.stages.activate_tasks ()
12830 #4 0x804aacc in un () at un.adb:5
12833 @item break @var{linespec} task @var{taskno}
12834 @itemx break @var{linespec} task @var{taskno} if @dots{}
12835 @cindex breakpoints and tasks, in Ada
12836 @cindex task breakpoints, in Ada
12837 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12838 These commands are like the @code{break @dots{} thread @dots{}}
12839 command (@pxref{Thread Stops}).
12840 @var{linespec} specifies source lines, as described
12841 in @ref{Specify Location}.
12843 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12844 to specify that you only want @value{GDBN} to stop the program when a
12845 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12846 numeric task identifiers assigned by @value{GDBN}, shown in the first
12847 column of the @samp{info tasks} display.
12849 If you do not specify @samp{task @var{taskno}} when you set a
12850 breakpoint, the breakpoint applies to @emph{all} tasks of your
12853 You can use the @code{task} qualifier on conditional breakpoints as
12854 well; in this case, place @samp{task @var{taskno}} before the
12855 breakpoint condition (before the @code{if}).
12863 (@value{GDBP}) info tasks
12864 ID TID P-ID Pri State Name
12865 1 140022020 0 15 Child Activation Wait main_task
12866 2 140045060 1 15 Accept/Select Wait t2
12867 3 140044840 1 15 Runnable t1
12868 * 4 140056040 1 15 Runnable t3
12869 (@value{GDBP}) b 15 task 2
12870 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12871 (@value{GDBP}) cont
12876 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12878 (@value{GDBP}) info tasks
12879 ID TID P-ID Pri State Name
12880 1 140022020 0 15 Child Activation Wait main_task
12881 * 2 140045060 1 15 Runnable t2
12882 3 140044840 1 15 Runnable t1
12883 4 140056040 1 15 Delay Sleep t3
12887 @node Ada Tasks and Core Files
12888 @subsubsection Tasking Support when Debugging Core Files
12889 @cindex Ada tasking and core file debugging
12891 When inspecting a core file, as opposed to debugging a live program,
12892 tasking support may be limited or even unavailable, depending on
12893 the platform being used.
12894 For instance, on x86-linux, the list of tasks is available, but task
12895 switching is not supported. On Tru64, however, task switching will work
12898 On certain platforms, including Tru64, the debugger needs to perform some
12899 memory writes in order to provide Ada tasking support. When inspecting
12900 a core file, this means that the core file must be opened with read-write
12901 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12902 Under these circumstances, you should make a backup copy of the core
12903 file before inspecting it with @value{GDBN}.
12906 @subsubsection Known Peculiarities of Ada Mode
12907 @cindex Ada, problems
12909 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12910 we know of several problems with and limitations of Ada mode in
12912 some of which will be fixed with planned future releases of the debugger
12913 and the GNU Ada compiler.
12917 Currently, the debugger
12918 has insufficient information to determine whether certain pointers represent
12919 pointers to objects or the objects themselves.
12920 Thus, the user may have to tack an extra @code{.all} after an expression
12921 to get it printed properly.
12924 Static constants that the compiler chooses not to materialize as objects in
12925 storage are invisible to the debugger.
12928 Named parameter associations in function argument lists are ignored (the
12929 argument lists are treated as positional).
12932 Many useful library packages are currently invisible to the debugger.
12935 Fixed-point arithmetic, conversions, input, and output is carried out using
12936 floating-point arithmetic, and may give results that only approximate those on
12940 The GNAT compiler never generates the prefix @code{Standard} for any of
12941 the standard symbols defined by the Ada language. @value{GDBN} knows about
12942 this: it will strip the prefix from names when you use it, and will never
12943 look for a name you have so qualified among local symbols, nor match against
12944 symbols in other packages or subprograms. If you have
12945 defined entities anywhere in your program other than parameters and
12946 local variables whose simple names match names in @code{Standard},
12947 GNAT's lack of qualification here can cause confusion. When this happens,
12948 you can usually resolve the confusion
12949 by qualifying the problematic names with package
12950 @code{Standard} explicitly.
12953 Older versions of the compiler sometimes generate erroneous debugging
12954 information, resulting in the debugger incorrectly printing the value
12955 of affected entities. In some cases, the debugger is able to work
12956 around an issue automatically. In other cases, the debugger is able
12957 to work around the issue, but the work-around has to be specifically
12960 @kindex set ada trust-PAD-over-XVS
12961 @kindex show ada trust-PAD-over-XVS
12964 @item set ada trust-PAD-over-XVS on
12965 Configure GDB to strictly follow the GNAT encoding when computing the
12966 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
12967 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
12968 a complete description of the encoding used by the GNAT compiler).
12969 This is the default.
12971 @item set ada trust-PAD-over-XVS off
12972 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
12973 sometimes prints the wrong value for certain entities, changing @code{ada
12974 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
12975 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
12976 @code{off}, but this incurs a slight performance penalty, so it is
12977 recommended to leave this setting to @code{on} unless necessary.
12981 @node Unsupported Languages
12982 @section Unsupported Languages
12984 @cindex unsupported languages
12985 @cindex minimal language
12986 In addition to the other fully-supported programming languages,
12987 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12988 It does not represent a real programming language, but provides a set
12989 of capabilities close to what the C or assembly languages provide.
12990 This should allow most simple operations to be performed while debugging
12991 an application that uses a language currently not supported by @value{GDBN}.
12993 If the language is set to @code{auto}, @value{GDBN} will automatically
12994 select this language if the current frame corresponds to an unsupported
12998 @chapter Examining the Symbol Table
13000 The commands described in this chapter allow you to inquire about the
13001 symbols (names of variables, functions and types) defined in your
13002 program. This information is inherent in the text of your program and
13003 does not change as your program executes. @value{GDBN} finds it in your
13004 program's symbol table, in the file indicated when you started @value{GDBN}
13005 (@pxref{File Options, ,Choosing Files}), or by one of the
13006 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13008 @cindex symbol names
13009 @cindex names of symbols
13010 @cindex quoting names
13011 Occasionally, you may need to refer to symbols that contain unusual
13012 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13013 most frequent case is in referring to static variables in other
13014 source files (@pxref{Variables,,Program Variables}). File names
13015 are recorded in object files as debugging symbols, but @value{GDBN} would
13016 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13017 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13018 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13025 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13028 @cindex case-insensitive symbol names
13029 @cindex case sensitivity in symbol names
13030 @kindex set case-sensitive
13031 @item set case-sensitive on
13032 @itemx set case-sensitive off
13033 @itemx set case-sensitive auto
13034 Normally, when @value{GDBN} looks up symbols, it matches their names
13035 with case sensitivity determined by the current source language.
13036 Occasionally, you may wish to control that. The command @code{set
13037 case-sensitive} lets you do that by specifying @code{on} for
13038 case-sensitive matches or @code{off} for case-insensitive ones. If
13039 you specify @code{auto}, case sensitivity is reset to the default
13040 suitable for the source language. The default is case-sensitive
13041 matches for all languages except for Fortran, for which the default is
13042 case-insensitive matches.
13044 @kindex show case-sensitive
13045 @item show case-sensitive
13046 This command shows the current setting of case sensitivity for symbols
13049 @kindex info address
13050 @cindex address of a symbol
13051 @item info address @var{symbol}
13052 Describe where the data for @var{symbol} is stored. For a register
13053 variable, this says which register it is kept in. For a non-register
13054 local variable, this prints the stack-frame offset at which the variable
13057 Note the contrast with @samp{print &@var{symbol}}, which does not work
13058 at all for a register variable, and for a stack local variable prints
13059 the exact address of the current instantiation of the variable.
13061 @kindex info symbol
13062 @cindex symbol from address
13063 @cindex closest symbol and offset for an address
13064 @item info symbol @var{addr}
13065 Print the name of a symbol which is stored at the address @var{addr}.
13066 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13067 nearest symbol and an offset from it:
13070 (@value{GDBP}) info symbol 0x54320
13071 _initialize_vx + 396 in section .text
13075 This is the opposite of the @code{info address} command. You can use
13076 it to find out the name of a variable or a function given its address.
13078 For dynamically linked executables, the name of executable or shared
13079 library containing the symbol is also printed:
13082 (@value{GDBP}) info symbol 0x400225
13083 _start + 5 in section .text of /tmp/a.out
13084 (@value{GDBP}) info symbol 0x2aaaac2811cf
13085 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13089 @item whatis [@var{arg}]
13090 Print the data type of @var{arg}, which can be either an expression or
13091 a data type. With no argument, print the data type of @code{$}, the
13092 last value in the value history. If @var{arg} is an expression, it is
13093 not actually evaluated, and any side-effecting operations (such as
13094 assignments or function calls) inside it do not take place. If
13095 @var{arg} is a type name, it may be the name of a type or typedef, or
13096 for C code it may have the form @samp{class @var{class-name}},
13097 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13098 @samp{enum @var{enum-tag}}.
13099 @xref{Expressions, ,Expressions}.
13102 @item ptype [@var{arg}]
13103 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13104 detailed description of the type, instead of just the name of the type.
13105 @xref{Expressions, ,Expressions}.
13107 For example, for this variable declaration:
13110 struct complex @{double real; double imag;@} v;
13114 the two commands give this output:
13118 (@value{GDBP}) whatis v
13119 type = struct complex
13120 (@value{GDBP}) ptype v
13121 type = struct complex @{
13129 As with @code{whatis}, using @code{ptype} without an argument refers to
13130 the type of @code{$}, the last value in the value history.
13132 @cindex incomplete type
13133 Sometimes, programs use opaque data types or incomplete specifications
13134 of complex data structure. If the debug information included in the
13135 program does not allow @value{GDBN} to display a full declaration of
13136 the data type, it will say @samp{<incomplete type>}. For example,
13137 given these declarations:
13141 struct foo *fooptr;
13145 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13148 (@value{GDBP}) ptype foo
13149 $1 = <incomplete type>
13153 ``Incomplete type'' is C terminology for data types that are not
13154 completely specified.
13157 @item info types @var{regexp}
13159 Print a brief description of all types whose names match the regular
13160 expression @var{regexp} (or all types in your program, if you supply
13161 no argument). Each complete typename is matched as though it were a
13162 complete line; thus, @samp{i type value} gives information on all
13163 types in your program whose names include the string @code{value}, but
13164 @samp{i type ^value$} gives information only on types whose complete
13165 name is @code{value}.
13167 This command differs from @code{ptype} in two ways: first, like
13168 @code{whatis}, it does not print a detailed description; second, it
13169 lists all source files where a type is defined.
13172 @cindex local variables
13173 @item info scope @var{location}
13174 List all the variables local to a particular scope. This command
13175 accepts a @var{location} argument---a function name, a source line, or
13176 an address preceded by a @samp{*}, and prints all the variables local
13177 to the scope defined by that location. (@xref{Specify Location}, for
13178 details about supported forms of @var{location}.) For example:
13181 (@value{GDBP}) @b{info scope command_line_handler}
13182 Scope for command_line_handler:
13183 Symbol rl is an argument at stack/frame offset 8, length 4.
13184 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13185 Symbol linelength is in static storage at address 0x150a1c, length 4.
13186 Symbol p is a local variable in register $esi, length 4.
13187 Symbol p1 is a local variable in register $ebx, length 4.
13188 Symbol nline is a local variable in register $edx, length 4.
13189 Symbol repeat is a local variable at frame offset -8, length 4.
13193 This command is especially useful for determining what data to collect
13194 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13197 @kindex info source
13199 Show information about the current source file---that is, the source file for
13200 the function containing the current point of execution:
13203 the name of the source file, and the directory containing it,
13205 the directory it was compiled in,
13207 its length, in lines,
13209 which programming language it is written in,
13211 whether the executable includes debugging information for that file, and
13212 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13214 whether the debugging information includes information about
13215 preprocessor macros.
13219 @kindex info sources
13221 Print the names of all source files in your program for which there is
13222 debugging information, organized into two lists: files whose symbols
13223 have already been read, and files whose symbols will be read when needed.
13225 @kindex info functions
13226 @item info functions
13227 Print the names and data types of all defined functions.
13229 @item info functions @var{regexp}
13230 Print the names and data types of all defined functions
13231 whose names contain a match for regular expression @var{regexp}.
13232 Thus, @samp{info fun step} finds all functions whose names
13233 include @code{step}; @samp{info fun ^step} finds those whose names
13234 start with @code{step}. If a function name contains characters
13235 that conflict with the regular expression language (e.g.@:
13236 @samp{operator*()}), they may be quoted with a backslash.
13238 @kindex info variables
13239 @item info variables
13240 Print the names and data types of all variables that are defined
13241 outside of functions (i.e.@: excluding local variables).
13243 @item info variables @var{regexp}
13244 Print the names and data types of all variables (except for local
13245 variables) whose names contain a match for regular expression
13248 @kindex info classes
13249 @cindex Objective-C, classes and selectors
13251 @itemx info classes @var{regexp}
13252 Display all Objective-C classes in your program, or
13253 (with the @var{regexp} argument) all those matching a particular regular
13256 @kindex info selectors
13257 @item info selectors
13258 @itemx info selectors @var{regexp}
13259 Display all Objective-C selectors in your program, or
13260 (with the @var{regexp} argument) all those matching a particular regular
13264 This was never implemented.
13265 @kindex info methods
13267 @itemx info methods @var{regexp}
13268 The @code{info methods} command permits the user to examine all defined
13269 methods within C@t{++} program, or (with the @var{regexp} argument) a
13270 specific set of methods found in the various C@t{++} classes. Many
13271 C@t{++} classes provide a large number of methods. Thus, the output
13272 from the @code{ptype} command can be overwhelming and hard to use. The
13273 @code{info-methods} command filters the methods, printing only those
13274 which match the regular-expression @var{regexp}.
13277 @cindex reloading symbols
13278 Some systems allow individual object files that make up your program to
13279 be replaced without stopping and restarting your program. For example,
13280 in VxWorks you can simply recompile a defective object file and keep on
13281 running. If you are running on one of these systems, you can allow
13282 @value{GDBN} to reload the symbols for automatically relinked modules:
13285 @kindex set symbol-reloading
13286 @item set symbol-reloading on
13287 Replace symbol definitions for the corresponding source file when an
13288 object file with a particular name is seen again.
13290 @item set symbol-reloading off
13291 Do not replace symbol definitions when encountering object files of the
13292 same name more than once. This is the default state; if you are not
13293 running on a system that permits automatic relinking of modules, you
13294 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13295 may discard symbols when linking large programs, that may contain
13296 several modules (from different directories or libraries) with the same
13299 @kindex show symbol-reloading
13300 @item show symbol-reloading
13301 Show the current @code{on} or @code{off} setting.
13304 @cindex opaque data types
13305 @kindex set opaque-type-resolution
13306 @item set opaque-type-resolution on
13307 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13308 declared as a pointer to a @code{struct}, @code{class}, or
13309 @code{union}---for example, @code{struct MyType *}---that is used in one
13310 source file although the full declaration of @code{struct MyType} is in
13311 another source file. The default is on.
13313 A change in the setting of this subcommand will not take effect until
13314 the next time symbols for a file are loaded.
13316 @item set opaque-type-resolution off
13317 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13318 is printed as follows:
13320 @{<no data fields>@}
13323 @kindex show opaque-type-resolution
13324 @item show opaque-type-resolution
13325 Show whether opaque types are resolved or not.
13327 @kindex maint print symbols
13328 @cindex symbol dump
13329 @kindex maint print psymbols
13330 @cindex partial symbol dump
13331 @item maint print symbols @var{filename}
13332 @itemx maint print psymbols @var{filename}
13333 @itemx maint print msymbols @var{filename}
13334 Write a dump of debugging symbol data into the file @var{filename}.
13335 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13336 symbols with debugging data are included. If you use @samp{maint print
13337 symbols}, @value{GDBN} includes all the symbols for which it has already
13338 collected full details: that is, @var{filename} reflects symbols for
13339 only those files whose symbols @value{GDBN} has read. You can use the
13340 command @code{info sources} to find out which files these are. If you
13341 use @samp{maint print psymbols} instead, the dump shows information about
13342 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13343 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13344 @samp{maint print msymbols} dumps just the minimal symbol information
13345 required for each object file from which @value{GDBN} has read some symbols.
13346 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13347 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13349 @kindex maint info symtabs
13350 @kindex maint info psymtabs
13351 @cindex listing @value{GDBN}'s internal symbol tables
13352 @cindex symbol tables, listing @value{GDBN}'s internal
13353 @cindex full symbol tables, listing @value{GDBN}'s internal
13354 @cindex partial symbol tables, listing @value{GDBN}'s internal
13355 @item maint info symtabs @r{[} @var{regexp} @r{]}
13356 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13358 List the @code{struct symtab} or @code{struct partial_symtab}
13359 structures whose names match @var{regexp}. If @var{regexp} is not
13360 given, list them all. The output includes expressions which you can
13361 copy into a @value{GDBN} debugging this one to examine a particular
13362 structure in more detail. For example:
13365 (@value{GDBP}) maint info psymtabs dwarf2read
13366 @{ objfile /home/gnu/build/gdb/gdb
13367 ((struct objfile *) 0x82e69d0)
13368 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13369 ((struct partial_symtab *) 0x8474b10)
13372 text addresses 0x814d3c8 -- 0x8158074
13373 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13374 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13375 dependencies (none)
13378 (@value{GDBP}) maint info symtabs
13382 We see that there is one partial symbol table whose filename contains
13383 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13384 and we see that @value{GDBN} has not read in any symtabs yet at all.
13385 If we set a breakpoint on a function, that will cause @value{GDBN} to
13386 read the symtab for the compilation unit containing that function:
13389 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13390 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13392 (@value{GDBP}) maint info symtabs
13393 @{ objfile /home/gnu/build/gdb/gdb
13394 ((struct objfile *) 0x82e69d0)
13395 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13396 ((struct symtab *) 0x86c1f38)
13399 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13400 linetable ((struct linetable *) 0x8370fa0)
13401 debugformat DWARF 2
13410 @chapter Altering Execution
13412 Once you think you have found an error in your program, you might want to
13413 find out for certain whether correcting the apparent error would lead to
13414 correct results in the rest of the run. You can find the answer by
13415 experiment, using the @value{GDBN} features for altering execution of the
13418 For example, you can store new values into variables or memory
13419 locations, give your program a signal, restart it at a different
13420 address, or even return prematurely from a function.
13423 * Assignment:: Assignment to variables
13424 * Jumping:: Continuing at a different address
13425 * Signaling:: Giving your program a signal
13426 * Returning:: Returning from a function
13427 * Calling:: Calling your program's functions
13428 * Patching:: Patching your program
13432 @section Assignment to Variables
13435 @cindex setting variables
13436 To alter the value of a variable, evaluate an assignment expression.
13437 @xref{Expressions, ,Expressions}. For example,
13444 stores the value 4 into the variable @code{x}, and then prints the
13445 value of the assignment expression (which is 4).
13446 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13447 information on operators in supported languages.
13449 @kindex set variable
13450 @cindex variables, setting
13451 If you are not interested in seeing the value of the assignment, use the
13452 @code{set} command instead of the @code{print} command. @code{set} is
13453 really the same as @code{print} except that the expression's value is
13454 not printed and is not put in the value history (@pxref{Value History,
13455 ,Value History}). The expression is evaluated only for its effects.
13457 If the beginning of the argument string of the @code{set} command
13458 appears identical to a @code{set} subcommand, use the @code{set
13459 variable} command instead of just @code{set}. This command is identical
13460 to @code{set} except for its lack of subcommands. For example, if your
13461 program has a variable @code{width}, you get an error if you try to set
13462 a new value with just @samp{set width=13}, because @value{GDBN} has the
13463 command @code{set width}:
13466 (@value{GDBP}) whatis width
13468 (@value{GDBP}) p width
13470 (@value{GDBP}) set width=47
13471 Invalid syntax in expression.
13475 The invalid expression, of course, is @samp{=47}. In
13476 order to actually set the program's variable @code{width}, use
13479 (@value{GDBP}) set var width=47
13482 Because the @code{set} command has many subcommands that can conflict
13483 with the names of program variables, it is a good idea to use the
13484 @code{set variable} command instead of just @code{set}. For example, if
13485 your program has a variable @code{g}, you run into problems if you try
13486 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13487 the command @code{set gnutarget}, abbreviated @code{set g}:
13491 (@value{GDBP}) whatis g
13495 (@value{GDBP}) set g=4
13499 The program being debugged has been started already.
13500 Start it from the beginning? (y or n) y
13501 Starting program: /home/smith/cc_progs/a.out
13502 "/home/smith/cc_progs/a.out": can't open to read symbols:
13503 Invalid bfd target.
13504 (@value{GDBP}) show g
13505 The current BFD target is "=4".
13510 The program variable @code{g} did not change, and you silently set the
13511 @code{gnutarget} to an invalid value. In order to set the variable
13515 (@value{GDBP}) set var g=4
13518 @value{GDBN} allows more implicit conversions in assignments than C; you can
13519 freely store an integer value into a pointer variable or vice versa,
13520 and you can convert any structure to any other structure that is the
13521 same length or shorter.
13522 @comment FIXME: how do structs align/pad in these conversions?
13523 @comment /doc@cygnus.com 18dec1990
13525 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13526 construct to generate a value of specified type at a specified address
13527 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13528 to memory location @code{0x83040} as an integer (which implies a certain size
13529 and representation in memory), and
13532 set @{int@}0x83040 = 4
13536 stores the value 4 into that memory location.
13539 @section Continuing at a Different Address
13541 Ordinarily, when you continue your program, you do so at the place where
13542 it stopped, with the @code{continue} command. You can instead continue at
13543 an address of your own choosing, with the following commands:
13547 @item jump @var{linespec}
13548 @itemx jump @var{location}
13549 Resume execution at line @var{linespec} or at address given by
13550 @var{location}. Execution stops again immediately if there is a
13551 breakpoint there. @xref{Specify Location}, for a description of the
13552 different forms of @var{linespec} and @var{location}. It is common
13553 practice to use the @code{tbreak} command in conjunction with
13554 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13556 The @code{jump} command does not change the current stack frame, or
13557 the stack pointer, or the contents of any memory location or any
13558 register other than the program counter. If line @var{linespec} is in
13559 a different function from the one currently executing, the results may
13560 be bizarre if the two functions expect different patterns of arguments or
13561 of local variables. For this reason, the @code{jump} command requests
13562 confirmation if the specified line is not in the function currently
13563 executing. However, even bizarre results are predictable if you are
13564 well acquainted with the machine-language code of your program.
13567 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13568 On many systems, you can get much the same effect as the @code{jump}
13569 command by storing a new value into the register @code{$pc}. The
13570 difference is that this does not start your program running; it only
13571 changes the address of where it @emph{will} run when you continue. For
13579 makes the next @code{continue} command or stepping command execute at
13580 address @code{0x485}, rather than at the address where your program stopped.
13581 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13583 The most common occasion to use the @code{jump} command is to back
13584 up---perhaps with more breakpoints set---over a portion of a program
13585 that has already executed, in order to examine its execution in more
13590 @section Giving your Program a Signal
13591 @cindex deliver a signal to a program
13595 @item signal @var{signal}
13596 Resume execution where your program stopped, but immediately give it the
13597 signal @var{signal}. @var{signal} can be the name or the number of a
13598 signal. For example, on many systems @code{signal 2} and @code{signal
13599 SIGINT} are both ways of sending an interrupt signal.
13601 Alternatively, if @var{signal} is zero, continue execution without
13602 giving a signal. This is useful when your program stopped on account of
13603 a signal and would ordinary see the signal when resumed with the
13604 @code{continue} command; @samp{signal 0} causes it to resume without a
13607 @code{signal} does not repeat when you press @key{RET} a second time
13608 after executing the command.
13612 Invoking the @code{signal} command is not the same as invoking the
13613 @code{kill} utility from the shell. Sending a signal with @code{kill}
13614 causes @value{GDBN} to decide what to do with the signal depending on
13615 the signal handling tables (@pxref{Signals}). The @code{signal} command
13616 passes the signal directly to your program.
13620 @section Returning from a Function
13623 @cindex returning from a function
13626 @itemx return @var{expression}
13627 You can cancel execution of a function call with the @code{return}
13628 command. If you give an
13629 @var{expression} argument, its value is used as the function's return
13633 When you use @code{return}, @value{GDBN} discards the selected stack frame
13634 (and all frames within it). You can think of this as making the
13635 discarded frame return prematurely. If you wish to specify a value to
13636 be returned, give that value as the argument to @code{return}.
13638 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13639 Frame}), and any other frames inside of it, leaving its caller as the
13640 innermost remaining frame. That frame becomes selected. The
13641 specified value is stored in the registers used for returning values
13644 The @code{return} command does not resume execution; it leaves the
13645 program stopped in the state that would exist if the function had just
13646 returned. In contrast, the @code{finish} command (@pxref{Continuing
13647 and Stepping, ,Continuing and Stepping}) resumes execution until the
13648 selected stack frame returns naturally.
13650 @value{GDBN} needs to know how the @var{expression} argument should be set for
13651 the inferior. The concrete registers assignment depends on the OS ABI and the
13652 type being returned by the selected stack frame. For example it is common for
13653 OS ABI to return floating point values in FPU registers while integer values in
13654 CPU registers. Still some ABIs return even floating point values in CPU
13655 registers. Larger integer widths (such as @code{long long int}) also have
13656 specific placement rules. @value{GDBN} already knows the OS ABI from its
13657 current target so it needs to find out also the type being returned to make the
13658 assignment into the right register(s).
13660 Normally, the selected stack frame has debug info. @value{GDBN} will always
13661 use the debug info instead of the implicit type of @var{expression} when the
13662 debug info is available. For example, if you type @kbd{return -1}, and the
13663 function in the current stack frame is declared to return a @code{long long
13664 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13665 into a @code{long long int}:
13668 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13670 (@value{GDBP}) return -1
13671 Make func return now? (y or n) y
13672 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13673 43 printf ("result=%lld\n", func ());
13677 However, if the selected stack frame does not have a debug info, e.g., if the
13678 function was compiled without debug info, @value{GDBN} has to find out the type
13679 to return from user. Specifying a different type by mistake may set the value
13680 in different inferior registers than the caller code expects. For example,
13681 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13682 of a @code{long long int} result for a debug info less function (on 32-bit
13683 architectures). Therefore the user is required to specify the return type by
13684 an appropriate cast explicitly:
13687 Breakpoint 2, 0x0040050b in func ()
13688 (@value{GDBP}) return -1
13689 Return value type not available for selected stack frame.
13690 Please use an explicit cast of the value to return.
13691 (@value{GDBP}) return (long long int) -1
13692 Make selected stack frame return now? (y or n) y
13693 #0 0x00400526 in main ()
13698 @section Calling Program Functions
13701 @cindex calling functions
13702 @cindex inferior functions, calling
13703 @item print @var{expr}
13704 Evaluate the expression @var{expr} and display the resulting value.
13705 @var{expr} may include calls to functions in the program being
13709 @item call @var{expr}
13710 Evaluate the expression @var{expr} without displaying @code{void}
13713 You can use this variant of the @code{print} command if you want to
13714 execute a function from your program that does not return anything
13715 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13716 with @code{void} returned values that @value{GDBN} will otherwise
13717 print. If the result is not void, it is printed and saved in the
13721 It is possible for the function you call via the @code{print} or
13722 @code{call} command to generate a signal (e.g., if there's a bug in
13723 the function, or if you passed it incorrect arguments). What happens
13724 in that case is controlled by the @code{set unwindonsignal} command.
13726 Similarly, with a C@t{++} program it is possible for the function you
13727 call via the @code{print} or @code{call} command to generate an
13728 exception that is not handled due to the constraints of the dummy
13729 frame. In this case, any exception that is raised in the frame, but has
13730 an out-of-frame exception handler will not be found. GDB builds a
13731 dummy-frame for the inferior function call, and the unwinder cannot
13732 seek for exception handlers outside of this dummy-frame. What happens
13733 in that case is controlled by the
13734 @code{set unwind-on-terminating-exception} command.
13737 @item set unwindonsignal
13738 @kindex set unwindonsignal
13739 @cindex unwind stack in called functions
13740 @cindex call dummy stack unwinding
13741 Set unwinding of the stack if a signal is received while in a function
13742 that @value{GDBN} called in the program being debugged. If set to on,
13743 @value{GDBN} unwinds the stack it created for the call and restores
13744 the context to what it was before the call. If set to off (the
13745 default), @value{GDBN} stops in the frame where the signal was
13748 @item show unwindonsignal
13749 @kindex show unwindonsignal
13750 Show the current setting of stack unwinding in the functions called by
13753 @item set unwind-on-terminating-exception
13754 @kindex set unwind-on-terminating-exception
13755 @cindex unwind stack in called functions with unhandled exceptions
13756 @cindex call dummy stack unwinding on unhandled exception.
13757 Set unwinding of the stack if a C@t{++} exception is raised, but left
13758 unhandled while in a function that @value{GDBN} called in the program being
13759 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13760 it created for the call and restores the context to what it was before
13761 the call. If set to off, @value{GDBN} the exception is delivered to
13762 the default C@t{++} exception handler and the inferior terminated.
13764 @item show unwind-on-terminating-exception
13765 @kindex show unwind-on-terminating-exception
13766 Show the current setting of stack unwinding in the functions called by
13771 @cindex weak alias functions
13772 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13773 for another function. In such case, @value{GDBN} might not pick up
13774 the type information, including the types of the function arguments,
13775 which causes @value{GDBN} to call the inferior function incorrectly.
13776 As a result, the called function will function erroneously and may
13777 even crash. A solution to that is to use the name of the aliased
13781 @section Patching Programs
13783 @cindex patching binaries
13784 @cindex writing into executables
13785 @cindex writing into corefiles
13787 By default, @value{GDBN} opens the file containing your program's
13788 executable code (or the corefile) read-only. This prevents accidental
13789 alterations to machine code; but it also prevents you from intentionally
13790 patching your program's binary.
13792 If you'd like to be able to patch the binary, you can specify that
13793 explicitly with the @code{set write} command. For example, you might
13794 want to turn on internal debugging flags, or even to make emergency
13800 @itemx set write off
13801 If you specify @samp{set write on}, @value{GDBN} opens executable and
13802 core files for both reading and writing; if you specify @kbd{set write
13803 off} (the default), @value{GDBN} opens them read-only.
13805 If you have already loaded a file, you must load it again (using the
13806 @code{exec-file} or @code{core-file} command) after changing @code{set
13807 write}, for your new setting to take effect.
13811 Display whether executable files and core files are opened for writing
13812 as well as reading.
13816 @chapter @value{GDBN} Files
13818 @value{GDBN} needs to know the file name of the program to be debugged,
13819 both in order to read its symbol table and in order to start your
13820 program. To debug a core dump of a previous run, you must also tell
13821 @value{GDBN} the name of the core dump file.
13824 * Files:: Commands to specify files
13825 * Separate Debug Files:: Debugging information in separate files
13826 * Symbol Errors:: Errors reading symbol files
13827 * Data Files:: GDB data files
13831 @section Commands to Specify Files
13833 @cindex symbol table
13834 @cindex core dump file
13836 You may want to specify executable and core dump file names. The usual
13837 way to do this is at start-up time, using the arguments to
13838 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13839 Out of @value{GDBN}}).
13841 Occasionally it is necessary to change to a different file during a
13842 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13843 specify a file you want to use. Or you are debugging a remote target
13844 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13845 Program}). In these situations the @value{GDBN} commands to specify
13846 new files are useful.
13849 @cindex executable file
13851 @item file @var{filename}
13852 Use @var{filename} as the program to be debugged. It is read for its
13853 symbols and for the contents of pure memory. It is also the program
13854 executed when you use the @code{run} command. If you do not specify a
13855 directory and the file is not found in the @value{GDBN} working directory,
13856 @value{GDBN} uses the environment variable @code{PATH} as a list of
13857 directories to search, just as the shell does when looking for a program
13858 to run. You can change the value of this variable, for both @value{GDBN}
13859 and your program, using the @code{path} command.
13861 @cindex unlinked object files
13862 @cindex patching object files
13863 You can load unlinked object @file{.o} files into @value{GDBN} using
13864 the @code{file} command. You will not be able to ``run'' an object
13865 file, but you can disassemble functions and inspect variables. Also,
13866 if the underlying BFD functionality supports it, you could use
13867 @kbd{gdb -write} to patch object files using this technique. Note
13868 that @value{GDBN} can neither interpret nor modify relocations in this
13869 case, so branches and some initialized variables will appear to go to
13870 the wrong place. But this feature is still handy from time to time.
13873 @code{file} with no argument makes @value{GDBN} discard any information it
13874 has on both executable file and the symbol table.
13877 @item exec-file @r{[} @var{filename} @r{]}
13878 Specify that the program to be run (but not the symbol table) is found
13879 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13880 if necessary to locate your program. Omitting @var{filename} means to
13881 discard information on the executable file.
13883 @kindex symbol-file
13884 @item symbol-file @r{[} @var{filename} @r{]}
13885 Read symbol table information from file @var{filename}. @code{PATH} is
13886 searched when necessary. Use the @code{file} command to get both symbol
13887 table and program to run from the same file.
13889 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13890 program's symbol table.
13892 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13893 some breakpoints and auto-display expressions. This is because they may
13894 contain pointers to the internal data recording symbols and data types,
13895 which are part of the old symbol table data being discarded inside
13898 @code{symbol-file} does not repeat if you press @key{RET} again after
13901 When @value{GDBN} is configured for a particular environment, it
13902 understands debugging information in whatever format is the standard
13903 generated for that environment; you may use either a @sc{gnu} compiler, or
13904 other compilers that adhere to the local conventions.
13905 Best results are usually obtained from @sc{gnu} compilers; for example,
13906 using @code{@value{NGCC}} you can generate debugging information for
13909 For most kinds of object files, with the exception of old SVR3 systems
13910 using COFF, the @code{symbol-file} command does not normally read the
13911 symbol table in full right away. Instead, it scans the symbol table
13912 quickly to find which source files and which symbols are present. The
13913 details are read later, one source file at a time, as they are needed.
13915 The purpose of this two-stage reading strategy is to make @value{GDBN}
13916 start up faster. For the most part, it is invisible except for
13917 occasional pauses while the symbol table details for a particular source
13918 file are being read. (The @code{set verbose} command can turn these
13919 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13920 Warnings and Messages}.)
13922 We have not implemented the two-stage strategy for COFF yet. When the
13923 symbol table is stored in COFF format, @code{symbol-file} reads the
13924 symbol table data in full right away. Note that ``stabs-in-COFF''
13925 still does the two-stage strategy, since the debug info is actually
13929 @cindex reading symbols immediately
13930 @cindex symbols, reading immediately
13931 @item symbol-file @r{[} -readnow @r{]} @var{filename}
13932 @itemx file @r{[} -readnow @r{]} @var{filename}
13933 You can override the @value{GDBN} two-stage strategy for reading symbol
13934 tables by using the @samp{-readnow} option with any of the commands that
13935 load symbol table information, if you want to be sure @value{GDBN} has the
13936 entire symbol table available.
13938 @c FIXME: for now no mention of directories, since this seems to be in
13939 @c flux. 13mar1992 status is that in theory GDB would look either in
13940 @c current dir or in same dir as myprog; but issues like competing
13941 @c GDB's, or clutter in system dirs, mean that in practice right now
13942 @c only current dir is used. FFish says maybe a special GDB hierarchy
13943 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13947 @item core-file @r{[}@var{filename}@r{]}
13949 Specify the whereabouts of a core dump file to be used as the ``contents
13950 of memory''. Traditionally, core files contain only some parts of the
13951 address space of the process that generated them; @value{GDBN} can access the
13952 executable file itself for other parts.
13954 @code{core-file} with no argument specifies that no core file is
13957 Note that the core file is ignored when your program is actually running
13958 under @value{GDBN}. So, if you have been running your program and you
13959 wish to debug a core file instead, you must kill the subprocess in which
13960 the program is running. To do this, use the @code{kill} command
13961 (@pxref{Kill Process, ,Killing the Child Process}).
13963 @kindex add-symbol-file
13964 @cindex dynamic linking
13965 @item add-symbol-file @var{filename} @var{address}
13966 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13967 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13968 The @code{add-symbol-file} command reads additional symbol table
13969 information from the file @var{filename}. You would use this command
13970 when @var{filename} has been dynamically loaded (by some other means)
13971 into the program that is running. @var{address} should be the memory
13972 address at which the file has been loaded; @value{GDBN} cannot figure
13973 this out for itself. You can additionally specify an arbitrary number
13974 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13975 section name and base address for that section. You can specify any
13976 @var{address} as an expression.
13978 The symbol table of the file @var{filename} is added to the symbol table
13979 originally read with the @code{symbol-file} command. You can use the
13980 @code{add-symbol-file} command any number of times; the new symbol data
13981 thus read keeps adding to the old. To discard all old symbol data
13982 instead, use the @code{symbol-file} command without any arguments.
13984 @cindex relocatable object files, reading symbols from
13985 @cindex object files, relocatable, reading symbols from
13986 @cindex reading symbols from relocatable object files
13987 @cindex symbols, reading from relocatable object files
13988 @cindex @file{.o} files, reading symbols from
13989 Although @var{filename} is typically a shared library file, an
13990 executable file, or some other object file which has been fully
13991 relocated for loading into a process, you can also load symbolic
13992 information from relocatable @file{.o} files, as long as:
13996 the file's symbolic information refers only to linker symbols defined in
13997 that file, not to symbols defined by other object files,
13999 every section the file's symbolic information refers to has actually
14000 been loaded into the inferior, as it appears in the file, and
14002 you can determine the address at which every section was loaded, and
14003 provide these to the @code{add-symbol-file} command.
14007 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14008 relocatable files into an already running program; such systems
14009 typically make the requirements above easy to meet. However, it's
14010 important to recognize that many native systems use complex link
14011 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14012 assembly, for example) that make the requirements difficult to meet. In
14013 general, one cannot assume that using @code{add-symbol-file} to read a
14014 relocatable object file's symbolic information will have the same effect
14015 as linking the relocatable object file into the program in the normal
14018 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14020 @kindex add-symbol-file-from-memory
14021 @cindex @code{syscall DSO}
14022 @cindex load symbols from memory
14023 @item add-symbol-file-from-memory @var{address}
14024 Load symbols from the given @var{address} in a dynamically loaded
14025 object file whose image is mapped directly into the inferior's memory.
14026 For example, the Linux kernel maps a @code{syscall DSO} into each
14027 process's address space; this DSO provides kernel-specific code for
14028 some system calls. The argument can be any expression whose
14029 evaluation yields the address of the file's shared object file header.
14030 For this command to work, you must have used @code{symbol-file} or
14031 @code{exec-file} commands in advance.
14033 @kindex add-shared-symbol-files
14035 @item add-shared-symbol-files @var{library-file}
14036 @itemx assf @var{library-file}
14037 The @code{add-shared-symbol-files} command can currently be used only
14038 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14039 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14040 @value{GDBN} automatically looks for shared libraries, however if
14041 @value{GDBN} does not find yours, you can invoke
14042 @code{add-shared-symbol-files}. It takes one argument: the shared
14043 library's file name. @code{assf} is a shorthand alias for
14044 @code{add-shared-symbol-files}.
14047 @item section @var{section} @var{addr}
14048 The @code{section} command changes the base address of the named
14049 @var{section} of the exec file to @var{addr}. This can be used if the
14050 exec file does not contain section addresses, (such as in the
14051 @code{a.out} format), or when the addresses specified in the file
14052 itself are wrong. Each section must be changed separately. The
14053 @code{info files} command, described below, lists all the sections and
14057 @kindex info target
14060 @code{info files} and @code{info target} are synonymous; both print the
14061 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14062 including the names of the executable and core dump files currently in
14063 use by @value{GDBN}, and the files from which symbols were loaded. The
14064 command @code{help target} lists all possible targets rather than
14067 @kindex maint info sections
14068 @item maint info sections
14069 Another command that can give you extra information about program sections
14070 is @code{maint info sections}. In addition to the section information
14071 displayed by @code{info files}, this command displays the flags and file
14072 offset of each section in the executable and core dump files. In addition,
14073 @code{maint info sections} provides the following command options (which
14074 may be arbitrarily combined):
14078 Display sections for all loaded object files, including shared libraries.
14079 @item @var{sections}
14080 Display info only for named @var{sections}.
14081 @item @var{section-flags}
14082 Display info only for sections for which @var{section-flags} are true.
14083 The section flags that @value{GDBN} currently knows about are:
14086 Section will have space allocated in the process when loaded.
14087 Set for all sections except those containing debug information.
14089 Section will be loaded from the file into the child process memory.
14090 Set for pre-initialized code and data, clear for @code{.bss} sections.
14092 Section needs to be relocated before loading.
14094 Section cannot be modified by the child process.
14096 Section contains executable code only.
14098 Section contains data only (no executable code).
14100 Section will reside in ROM.
14102 Section contains data for constructor/destructor lists.
14104 Section is not empty.
14106 An instruction to the linker to not output the section.
14107 @item COFF_SHARED_LIBRARY
14108 A notification to the linker that the section contains
14109 COFF shared library information.
14111 Section contains common symbols.
14114 @kindex set trust-readonly-sections
14115 @cindex read-only sections
14116 @item set trust-readonly-sections on
14117 Tell @value{GDBN} that readonly sections in your object file
14118 really are read-only (i.e.@: that their contents will not change).
14119 In that case, @value{GDBN} can fetch values from these sections
14120 out of the object file, rather than from the target program.
14121 For some targets (notably embedded ones), this can be a significant
14122 enhancement to debugging performance.
14124 The default is off.
14126 @item set trust-readonly-sections off
14127 Tell @value{GDBN} not to trust readonly sections. This means that
14128 the contents of the section might change while the program is running,
14129 and must therefore be fetched from the target when needed.
14131 @item show trust-readonly-sections
14132 Show the current setting of trusting readonly sections.
14135 All file-specifying commands allow both absolute and relative file names
14136 as arguments. @value{GDBN} always converts the file name to an absolute file
14137 name and remembers it that way.
14139 @cindex shared libraries
14140 @anchor{Shared Libraries}
14141 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14142 and IBM RS/6000 AIX shared libraries.
14144 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14145 shared libraries. @xref{Expat}.
14147 @value{GDBN} automatically loads symbol definitions from shared libraries
14148 when you use the @code{run} command, or when you examine a core file.
14149 (Before you issue the @code{run} command, @value{GDBN} does not understand
14150 references to a function in a shared library, however---unless you are
14151 debugging a core file).
14153 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14154 automatically loads the symbols at the time of the @code{shl_load} call.
14156 @c FIXME: some @value{GDBN} release may permit some refs to undef
14157 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14158 @c FIXME...lib; check this from time to time when updating manual
14160 There are times, however, when you may wish to not automatically load
14161 symbol definitions from shared libraries, such as when they are
14162 particularly large or there are many of them.
14164 To control the automatic loading of shared library symbols, use the
14168 @kindex set auto-solib-add
14169 @item set auto-solib-add @var{mode}
14170 If @var{mode} is @code{on}, symbols from all shared object libraries
14171 will be loaded automatically when the inferior begins execution, you
14172 attach to an independently started inferior, or when the dynamic linker
14173 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14174 is @code{off}, symbols must be loaded manually, using the
14175 @code{sharedlibrary} command. The default value is @code{on}.
14177 @cindex memory used for symbol tables
14178 If your program uses lots of shared libraries with debug info that
14179 takes large amounts of memory, you can decrease the @value{GDBN}
14180 memory footprint by preventing it from automatically loading the
14181 symbols from shared libraries. To that end, type @kbd{set
14182 auto-solib-add off} before running the inferior, then load each
14183 library whose debug symbols you do need with @kbd{sharedlibrary
14184 @var{regexp}}, where @var{regexp} is a regular expression that matches
14185 the libraries whose symbols you want to be loaded.
14187 @kindex show auto-solib-add
14188 @item show auto-solib-add
14189 Display the current autoloading mode.
14192 @cindex load shared library
14193 To explicitly load shared library symbols, use the @code{sharedlibrary}
14197 @kindex info sharedlibrary
14199 @item info share @var{regex}
14200 @itemx info sharedlibrary @var{regex}
14201 Print the names of the shared libraries which are currently loaded
14202 that match @var{regex}. If @var{regex} is omitted then print
14203 all shared libraries that are loaded.
14205 @kindex sharedlibrary
14207 @item sharedlibrary @var{regex}
14208 @itemx share @var{regex}
14209 Load shared object library symbols for files matching a
14210 Unix regular expression.
14211 As with files loaded automatically, it only loads shared libraries
14212 required by your program for a core file or after typing @code{run}. If
14213 @var{regex} is omitted all shared libraries required by your program are
14216 @item nosharedlibrary
14217 @kindex nosharedlibrary
14218 @cindex unload symbols from shared libraries
14219 Unload all shared object library symbols. This discards all symbols
14220 that have been loaded from all shared libraries. Symbols from shared
14221 libraries that were loaded by explicit user requests are not
14225 Sometimes you may wish that @value{GDBN} stops and gives you control
14226 when any of shared library events happen. Use the @code{set
14227 stop-on-solib-events} command for this:
14230 @item set stop-on-solib-events
14231 @kindex set stop-on-solib-events
14232 This command controls whether @value{GDBN} should give you control
14233 when the dynamic linker notifies it about some shared library event.
14234 The most common event of interest is loading or unloading of a new
14237 @item show stop-on-solib-events
14238 @kindex show stop-on-solib-events
14239 Show whether @value{GDBN} stops and gives you control when shared
14240 library events happen.
14243 Shared libraries are also supported in many cross or remote debugging
14244 configurations. @value{GDBN} needs to have access to the target's libraries;
14245 this can be accomplished either by providing copies of the libraries
14246 on the host system, or by asking @value{GDBN} to automatically retrieve the
14247 libraries from the target. If copies of the target libraries are
14248 provided, they need to be the same as the target libraries, although the
14249 copies on the target can be stripped as long as the copies on the host are
14252 @cindex where to look for shared libraries
14253 For remote debugging, you need to tell @value{GDBN} where the target
14254 libraries are, so that it can load the correct copies---otherwise, it
14255 may try to load the host's libraries. @value{GDBN} has two variables
14256 to specify the search directories for target libraries.
14259 @cindex prefix for shared library file names
14260 @cindex system root, alternate
14261 @kindex set solib-absolute-prefix
14262 @kindex set sysroot
14263 @item set sysroot @var{path}
14264 Use @var{path} as the system root for the program being debugged. Any
14265 absolute shared library paths will be prefixed with @var{path}; many
14266 runtime loaders store the absolute paths to the shared library in the
14267 target program's memory. If you use @code{set sysroot} to find shared
14268 libraries, they need to be laid out in the same way that they are on
14269 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14272 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14273 retrieve the target libraries from the remote system. This is only
14274 supported when using a remote target that supports the @code{remote get}
14275 command (@pxref{File Transfer,,Sending files to a remote system}).
14276 The part of @var{path} following the initial @file{remote:}
14277 (if present) is used as system root prefix on the remote file system.
14278 @footnote{If you want to specify a local system root using a directory
14279 that happens to be named @file{remote:}, you need to use some equivalent
14280 variant of the name like @file{./remote:}.}
14282 The @code{set solib-absolute-prefix} command is an alias for @code{set
14285 @cindex default system root
14286 @cindex @samp{--with-sysroot}
14287 You can set the default system root by using the configure-time
14288 @samp{--with-sysroot} option. If the system root is inside
14289 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14290 @samp{--exec-prefix}), then the default system root will be updated
14291 automatically if the installed @value{GDBN} is moved to a new
14294 @kindex show sysroot
14296 Display the current shared library prefix.
14298 @kindex set solib-search-path
14299 @item set solib-search-path @var{path}
14300 If this variable is set, @var{path} is a colon-separated list of
14301 directories to search for shared libraries. @samp{solib-search-path}
14302 is used after @samp{sysroot} fails to locate the library, or if the
14303 path to the library is relative instead of absolute. If you want to
14304 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14305 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14306 finding your host's libraries. @samp{sysroot} is preferred; setting
14307 it to a nonexistent directory may interfere with automatic loading
14308 of shared library symbols.
14310 @kindex show solib-search-path
14311 @item show solib-search-path
14312 Display the current shared library search path.
14316 @node Separate Debug Files
14317 @section Debugging Information in Separate Files
14318 @cindex separate debugging information files
14319 @cindex debugging information in separate files
14320 @cindex @file{.debug} subdirectories
14321 @cindex debugging information directory, global
14322 @cindex global debugging information directory
14323 @cindex build ID, and separate debugging files
14324 @cindex @file{.build-id} directory
14326 @value{GDBN} allows you to put a program's debugging information in a
14327 file separate from the executable itself, in a way that allows
14328 @value{GDBN} to find and load the debugging information automatically.
14329 Since debugging information can be very large---sometimes larger
14330 than the executable code itself---some systems distribute debugging
14331 information for their executables in separate files, which users can
14332 install only when they need to debug a problem.
14334 @value{GDBN} supports two ways of specifying the separate debug info
14339 The executable contains a @dfn{debug link} that specifies the name of
14340 the separate debug info file. The separate debug file's name is
14341 usually @file{@var{executable}.debug}, where @var{executable} is the
14342 name of the corresponding executable file without leading directories
14343 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14344 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14345 checksum for the debug file, which @value{GDBN} uses to validate that
14346 the executable and the debug file came from the same build.
14349 The executable contains a @dfn{build ID}, a unique bit string that is
14350 also present in the corresponding debug info file. (This is supported
14351 only on some operating systems, notably those which use the ELF format
14352 for binary files and the @sc{gnu} Binutils.) For more details about
14353 this feature, see the description of the @option{--build-id}
14354 command-line option in @ref{Options, , Command Line Options, ld.info,
14355 The GNU Linker}. The debug info file's name is not specified
14356 explicitly by the build ID, but can be computed from the build ID, see
14360 Depending on the way the debug info file is specified, @value{GDBN}
14361 uses two different methods of looking for the debug file:
14365 For the ``debug link'' method, @value{GDBN} looks up the named file in
14366 the directory of the executable file, then in a subdirectory of that
14367 directory named @file{.debug}, and finally under the global debug
14368 directory, in a subdirectory whose name is identical to the leading
14369 directories of the executable's absolute file name.
14372 For the ``build ID'' method, @value{GDBN} looks in the
14373 @file{.build-id} subdirectory of the global debug directory for a file
14374 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14375 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14376 are the rest of the bit string. (Real build ID strings are 32 or more
14377 hex characters, not 10.)
14380 So, for example, suppose you ask @value{GDBN} to debug
14381 @file{/usr/bin/ls}, which has a debug link that specifies the
14382 file @file{ls.debug}, and a build ID whose value in hex is
14383 @code{abcdef1234}. If the global debug directory is
14384 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14385 debug information files, in the indicated order:
14389 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14391 @file{/usr/bin/ls.debug}
14393 @file{/usr/bin/.debug/ls.debug}
14395 @file{/usr/lib/debug/usr/bin/ls.debug}.
14398 You can set the global debugging info directory's name, and view the
14399 name @value{GDBN} is currently using.
14403 @kindex set debug-file-directory
14404 @item set debug-file-directory @var{directories}
14405 Set the directories which @value{GDBN} searches for separate debugging
14406 information files to @var{directory}. Multiple directory components can be set
14407 concatenating them by a directory separator.
14409 @kindex show debug-file-directory
14410 @item show debug-file-directory
14411 Show the directories @value{GDBN} searches for separate debugging
14416 @cindex @code{.gnu_debuglink} sections
14417 @cindex debug link sections
14418 A debug link is a special section of the executable file named
14419 @code{.gnu_debuglink}. The section must contain:
14423 A filename, with any leading directory components removed, followed by
14426 zero to three bytes of padding, as needed to reach the next four-byte
14427 boundary within the section, and
14429 a four-byte CRC checksum, stored in the same endianness used for the
14430 executable file itself. The checksum is computed on the debugging
14431 information file's full contents by the function given below, passing
14432 zero as the @var{crc} argument.
14435 Any executable file format can carry a debug link, as long as it can
14436 contain a section named @code{.gnu_debuglink} with the contents
14439 @cindex @code{.note.gnu.build-id} sections
14440 @cindex build ID sections
14441 The build ID is a special section in the executable file (and in other
14442 ELF binary files that @value{GDBN} may consider). This section is
14443 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14444 It contains unique identification for the built files---the ID remains
14445 the same across multiple builds of the same build tree. The default
14446 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14447 content for the build ID string. The same section with an identical
14448 value is present in the original built binary with symbols, in its
14449 stripped variant, and in the separate debugging information file.
14451 The debugging information file itself should be an ordinary
14452 executable, containing a full set of linker symbols, sections, and
14453 debugging information. The sections of the debugging information file
14454 should have the same names, addresses, and sizes as the original file,
14455 but they need not contain any data---much like a @code{.bss} section
14456 in an ordinary executable.
14458 The @sc{gnu} binary utilities (Binutils) package includes the
14459 @samp{objcopy} utility that can produce
14460 the separated executable / debugging information file pairs using the
14461 following commands:
14464 @kbd{objcopy --only-keep-debug foo foo.debug}
14469 These commands remove the debugging
14470 information from the executable file @file{foo} and place it in the file
14471 @file{foo.debug}. You can use the first, second or both methods to link the
14476 The debug link method needs the following additional command to also leave
14477 behind a debug link in @file{foo}:
14480 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14483 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14484 a version of the @code{strip} command such that the command @kbd{strip foo -f
14485 foo.debug} has the same functionality as the two @code{objcopy} commands and
14486 the @code{ln -s} command above, together.
14489 Build ID gets embedded into the main executable using @code{ld --build-id} or
14490 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14491 compatibility fixes for debug files separation are present in @sc{gnu} binary
14492 utilities (Binutils) package since version 2.18.
14497 @cindex CRC algorithm definition
14498 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14499 IEEE 802.3 using the polynomial:
14501 @c TexInfo requires naked braces for multi-digit exponents for Tex
14502 @c output, but this causes HTML output to barf. HTML has to be set using
14503 @c raw commands. So we end up having to specify this equation in 2
14508 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
14509 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
14515 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14516 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14520 The function is computed byte at a time, taking the least
14521 significant bit of each byte first. The initial pattern
14522 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14523 the final result is inverted to ensure trailing zeros also affect the
14526 @emph{Note:} This is the same CRC polynomial as used in handling the
14527 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14528 , @value{GDBN} Remote Serial Protocol}). However in the
14529 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14530 significant bit first, and the result is not inverted, so trailing
14531 zeros have no effect on the CRC value.
14533 To complete the description, we show below the code of the function
14534 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14535 initially supplied @code{crc} argument means that an initial call to
14536 this function passing in zero will start computing the CRC using
14539 @kindex gnu_debuglink_crc32
14542 gnu_debuglink_crc32 (unsigned long crc,
14543 unsigned char *buf, size_t len)
14545 static const unsigned long crc32_table[256] =
14547 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14548 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14549 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14550 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14551 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14552 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14553 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14554 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14555 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14556 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14557 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14558 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14559 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14560 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14561 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14562 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14563 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14564 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14565 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14566 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14567 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14568 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14569 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14570 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14571 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14572 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14573 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14574 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14575 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14576 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14577 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14578 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14579 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14580 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14581 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14582 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14583 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14584 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14585 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14586 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14587 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14588 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14589 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14590 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14591 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14592 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14593 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14594 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14595 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14596 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14597 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14600 unsigned char *end;
14602 crc = ~crc & 0xffffffff;
14603 for (end = buf + len; buf < end; ++buf)
14604 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14605 return ~crc & 0xffffffff;
14610 This computation does not apply to the ``build ID'' method.
14613 @node Symbol Errors
14614 @section Errors Reading Symbol Files
14616 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14617 such as symbol types it does not recognize, or known bugs in compiler
14618 output. By default, @value{GDBN} does not notify you of such problems, since
14619 they are relatively common and primarily of interest to people
14620 debugging compilers. If you are interested in seeing information
14621 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14622 only one message about each such type of problem, no matter how many
14623 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14624 to see how many times the problems occur, with the @code{set
14625 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14628 The messages currently printed, and their meanings, include:
14631 @item inner block not inside outer block in @var{symbol}
14633 The symbol information shows where symbol scopes begin and end
14634 (such as at the start of a function or a block of statements). This
14635 error indicates that an inner scope block is not fully contained
14636 in its outer scope blocks.
14638 @value{GDBN} circumvents the problem by treating the inner block as if it had
14639 the same scope as the outer block. In the error message, @var{symbol}
14640 may be shown as ``@code{(don't know)}'' if the outer block is not a
14643 @item block at @var{address} out of order
14645 The symbol information for symbol scope blocks should occur in
14646 order of increasing addresses. This error indicates that it does not
14649 @value{GDBN} does not circumvent this problem, and has trouble
14650 locating symbols in the source file whose symbols it is reading. (You
14651 can often determine what source file is affected by specifying
14652 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14655 @item bad block start address patched
14657 The symbol information for a symbol scope block has a start address
14658 smaller than the address of the preceding source line. This is known
14659 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14661 @value{GDBN} circumvents the problem by treating the symbol scope block as
14662 starting on the previous source line.
14664 @item bad string table offset in symbol @var{n}
14667 Symbol number @var{n} contains a pointer into the string table which is
14668 larger than the size of the string table.
14670 @value{GDBN} circumvents the problem by considering the symbol to have the
14671 name @code{foo}, which may cause other problems if many symbols end up
14674 @item unknown symbol type @code{0x@var{nn}}
14676 The symbol information contains new data types that @value{GDBN} does
14677 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14678 uncomprehended information, in hexadecimal.
14680 @value{GDBN} circumvents the error by ignoring this symbol information.
14681 This usually allows you to debug your program, though certain symbols
14682 are not accessible. If you encounter such a problem and feel like
14683 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14684 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14685 and examine @code{*bufp} to see the symbol.
14687 @item stub type has NULL name
14689 @value{GDBN} could not find the full definition for a struct or class.
14691 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14692 The symbol information for a C@t{++} member function is missing some
14693 information that recent versions of the compiler should have output for
14696 @item info mismatch between compiler and debugger
14698 @value{GDBN} could not parse a type specification output by the compiler.
14703 @section GDB Data Files
14705 @cindex prefix for data files
14706 @value{GDBN} will sometimes read an auxiliary data file. These files
14707 are kept in a directory known as the @dfn{data directory}.
14709 You can set the data directory's name, and view the name @value{GDBN}
14710 is currently using.
14713 @kindex set data-directory
14714 @item set data-directory @var{directory}
14715 Set the directory which @value{GDBN} searches for auxiliary data files
14716 to @var{directory}.
14718 @kindex show data-directory
14719 @item show data-directory
14720 Show the directory @value{GDBN} searches for auxiliary data files.
14723 @cindex default data directory
14724 @cindex @samp{--with-gdb-datadir}
14725 You can set the default data directory by using the configure-time
14726 @samp{--with-gdb-datadir} option. If the data directory is inside
14727 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14728 @samp{--exec-prefix}), then the default data directory will be updated
14729 automatically if the installed @value{GDBN} is moved to a new
14733 @chapter Specifying a Debugging Target
14735 @cindex debugging target
14736 A @dfn{target} is the execution environment occupied by your program.
14738 Often, @value{GDBN} runs in the same host environment as your program;
14739 in that case, the debugging target is specified as a side effect when
14740 you use the @code{file} or @code{core} commands. When you need more
14741 flexibility---for example, running @value{GDBN} on a physically separate
14742 host, or controlling a standalone system over a serial port or a
14743 realtime system over a TCP/IP connection---you can use the @code{target}
14744 command to specify one of the target types configured for @value{GDBN}
14745 (@pxref{Target Commands, ,Commands for Managing Targets}).
14747 @cindex target architecture
14748 It is possible to build @value{GDBN} for several different @dfn{target
14749 architectures}. When @value{GDBN} is built like that, you can choose
14750 one of the available architectures with the @kbd{set architecture}
14754 @kindex set architecture
14755 @kindex show architecture
14756 @item set architecture @var{arch}
14757 This command sets the current target architecture to @var{arch}. The
14758 value of @var{arch} can be @code{"auto"}, in addition to one of the
14759 supported architectures.
14761 @item show architecture
14762 Show the current target architecture.
14764 @item set processor
14766 @kindex set processor
14767 @kindex show processor
14768 These are alias commands for, respectively, @code{set architecture}
14769 and @code{show architecture}.
14773 * Active Targets:: Active targets
14774 * Target Commands:: Commands for managing targets
14775 * Byte Order:: Choosing target byte order
14778 @node Active Targets
14779 @section Active Targets
14781 @cindex stacking targets
14782 @cindex active targets
14783 @cindex multiple targets
14785 There are three classes of targets: processes, core files, and
14786 executable files. @value{GDBN} can work concurrently on up to three
14787 active targets, one in each class. This allows you to (for example)
14788 start a process and inspect its activity without abandoning your work on
14791 For example, if you execute @samp{gdb a.out}, then the executable file
14792 @code{a.out} is the only active target. If you designate a core file as
14793 well---presumably from a prior run that crashed and coredumped---then
14794 @value{GDBN} has two active targets and uses them in tandem, looking
14795 first in the corefile target, then in the executable file, to satisfy
14796 requests for memory addresses. (Typically, these two classes of target
14797 are complementary, since core files contain only a program's
14798 read-write memory---variables and so on---plus machine status, while
14799 executable files contain only the program text and initialized data.)
14801 When you type @code{run}, your executable file becomes an active process
14802 target as well. When a process target is active, all @value{GDBN}
14803 commands requesting memory addresses refer to that target; addresses in
14804 an active core file or executable file target are obscured while the
14805 process target is active.
14807 Use the @code{core-file} and @code{exec-file} commands to select a new
14808 core file or executable target (@pxref{Files, ,Commands to Specify
14809 Files}). To specify as a target a process that is already running, use
14810 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14813 @node Target Commands
14814 @section Commands for Managing Targets
14817 @item target @var{type} @var{parameters}
14818 Connects the @value{GDBN} host environment to a target machine or
14819 process. A target is typically a protocol for talking to debugging
14820 facilities. You use the argument @var{type} to specify the type or
14821 protocol of the target machine.
14823 Further @var{parameters} are interpreted by the target protocol, but
14824 typically include things like device names or host names to connect
14825 with, process numbers, and baud rates.
14827 The @code{target} command does not repeat if you press @key{RET} again
14828 after executing the command.
14830 @kindex help target
14832 Displays the names of all targets available. To display targets
14833 currently selected, use either @code{info target} or @code{info files}
14834 (@pxref{Files, ,Commands to Specify Files}).
14836 @item help target @var{name}
14837 Describe a particular target, including any parameters necessary to
14840 @kindex set gnutarget
14841 @item set gnutarget @var{args}
14842 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14843 knows whether it is reading an @dfn{executable},
14844 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14845 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14846 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14849 @emph{Warning:} To specify a file format with @code{set gnutarget},
14850 you must know the actual BFD name.
14854 @xref{Files, , Commands to Specify Files}.
14856 @kindex show gnutarget
14857 @item show gnutarget
14858 Use the @code{show gnutarget} command to display what file format
14859 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14860 @value{GDBN} will determine the file format for each file automatically,
14861 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14864 @cindex common targets
14865 Here are some common targets (available, or not, depending on the GDB
14870 @item target exec @var{program}
14871 @cindex executable file target
14872 An executable file. @samp{target exec @var{program}} is the same as
14873 @samp{exec-file @var{program}}.
14875 @item target core @var{filename}
14876 @cindex core dump file target
14877 A core dump file. @samp{target core @var{filename}} is the same as
14878 @samp{core-file @var{filename}}.
14880 @item target remote @var{medium}
14881 @cindex remote target
14882 A remote system connected to @value{GDBN} via a serial line or network
14883 connection. This command tells @value{GDBN} to use its own remote
14884 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14886 For example, if you have a board connected to @file{/dev/ttya} on the
14887 machine running @value{GDBN}, you could say:
14890 target remote /dev/ttya
14893 @code{target remote} supports the @code{load} command. This is only
14894 useful if you have some other way of getting the stub to the target
14895 system, and you can put it somewhere in memory where it won't get
14896 clobbered by the download.
14899 @cindex built-in simulator target
14900 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14908 works; however, you cannot assume that a specific memory map, device
14909 drivers, or even basic I/O is available, although some simulators do
14910 provide these. For info about any processor-specific simulator details,
14911 see the appropriate section in @ref{Embedded Processors, ,Embedded
14916 Some configurations may include these targets as well:
14920 @item target nrom @var{dev}
14921 @cindex NetROM ROM emulator target
14922 NetROM ROM emulator. This target only supports downloading.
14926 Different targets are available on different configurations of @value{GDBN};
14927 your configuration may have more or fewer targets.
14929 Many remote targets require you to download the executable's code once
14930 you've successfully established a connection. You may wish to control
14931 various aspects of this process.
14936 @kindex set hash@r{, for remote monitors}
14937 @cindex hash mark while downloading
14938 This command controls whether a hash mark @samp{#} is displayed while
14939 downloading a file to the remote monitor. If on, a hash mark is
14940 displayed after each S-record is successfully downloaded to the
14944 @kindex show hash@r{, for remote monitors}
14945 Show the current status of displaying the hash mark.
14947 @item set debug monitor
14948 @kindex set debug monitor
14949 @cindex display remote monitor communications
14950 Enable or disable display of communications messages between
14951 @value{GDBN} and the remote monitor.
14953 @item show debug monitor
14954 @kindex show debug monitor
14955 Show the current status of displaying communications between
14956 @value{GDBN} and the remote monitor.
14961 @kindex load @var{filename}
14962 @item load @var{filename}
14964 Depending on what remote debugging facilities are configured into
14965 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14966 is meant to make @var{filename} (an executable) available for debugging
14967 on the remote system---by downloading, or dynamic linking, for example.
14968 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14969 the @code{add-symbol-file} command.
14971 If your @value{GDBN} does not have a @code{load} command, attempting to
14972 execute it gets the error message ``@code{You can't do that when your
14973 target is @dots{}}''
14975 The file is loaded at whatever address is specified in the executable.
14976 For some object file formats, you can specify the load address when you
14977 link the program; for other formats, like a.out, the object file format
14978 specifies a fixed address.
14979 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14981 Depending on the remote side capabilities, @value{GDBN} may be able to
14982 load programs into flash memory.
14984 @code{load} does not repeat if you press @key{RET} again after using it.
14988 @section Choosing Target Byte Order
14990 @cindex choosing target byte order
14991 @cindex target byte order
14993 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14994 offer the ability to run either big-endian or little-endian byte
14995 orders. Usually the executable or symbol will include a bit to
14996 designate the endian-ness, and you will not need to worry about
14997 which to use. However, you may still find it useful to adjust
14998 @value{GDBN}'s idea of processor endian-ness manually.
15002 @item set endian big
15003 Instruct @value{GDBN} to assume the target is big-endian.
15005 @item set endian little
15006 Instruct @value{GDBN} to assume the target is little-endian.
15008 @item set endian auto
15009 Instruct @value{GDBN} to use the byte order associated with the
15013 Display @value{GDBN}'s current idea of the target byte order.
15017 Note that these commands merely adjust interpretation of symbolic
15018 data on the host, and that they have absolutely no effect on the
15022 @node Remote Debugging
15023 @chapter Debugging Remote Programs
15024 @cindex remote debugging
15026 If you are trying to debug a program running on a machine that cannot run
15027 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15028 For example, you might use remote debugging on an operating system kernel,
15029 or on a small system which does not have a general purpose operating system
15030 powerful enough to run a full-featured debugger.
15032 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15033 to make this work with particular debugging targets. In addition,
15034 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15035 but not specific to any particular target system) which you can use if you
15036 write the remote stubs---the code that runs on the remote system to
15037 communicate with @value{GDBN}.
15039 Other remote targets may be available in your
15040 configuration of @value{GDBN}; use @code{help target} to list them.
15043 * Connecting:: Connecting to a remote target
15044 * File Transfer:: Sending files to a remote system
15045 * Server:: Using the gdbserver program
15046 * Remote Configuration:: Remote configuration
15047 * Remote Stub:: Implementing a remote stub
15051 @section Connecting to a Remote Target
15053 On the @value{GDBN} host machine, you will need an unstripped copy of
15054 your program, since @value{GDBN} needs symbol and debugging information.
15055 Start up @value{GDBN} as usual, using the name of the local copy of your
15056 program as the first argument.
15058 @cindex @code{target remote}
15059 @value{GDBN} can communicate with the target over a serial line, or
15060 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15061 each case, @value{GDBN} uses the same protocol for debugging your
15062 program; only the medium carrying the debugging packets varies. The
15063 @code{target remote} command establishes a connection to the target.
15064 Its arguments indicate which medium to use:
15068 @item target remote @var{serial-device}
15069 @cindex serial line, @code{target remote}
15070 Use @var{serial-device} to communicate with the target. For example,
15071 to use a serial line connected to the device named @file{/dev/ttyb}:
15074 target remote /dev/ttyb
15077 If you're using a serial line, you may want to give @value{GDBN} the
15078 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15079 (@pxref{Remote Configuration, set remotebaud}) before the
15080 @code{target} command.
15082 @item target remote @code{@var{host}:@var{port}}
15083 @itemx target remote @code{tcp:@var{host}:@var{port}}
15084 @cindex @acronym{TCP} port, @code{target remote}
15085 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15086 The @var{host} may be either a host name or a numeric @acronym{IP}
15087 address; @var{port} must be a decimal number. The @var{host} could be
15088 the target machine itself, if it is directly connected to the net, or
15089 it might be a terminal server which in turn has a serial line to the
15092 For example, to connect to port 2828 on a terminal server named
15096 target remote manyfarms:2828
15099 If your remote target is actually running on the same machine as your
15100 debugger session (e.g.@: a simulator for your target running on the
15101 same host), you can omit the hostname. For example, to connect to
15102 port 1234 on your local machine:
15105 target remote :1234
15109 Note that the colon is still required here.
15111 @item target remote @code{udp:@var{host}:@var{port}}
15112 @cindex @acronym{UDP} port, @code{target remote}
15113 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15114 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15117 target remote udp:manyfarms:2828
15120 When using a @acronym{UDP} connection for remote debugging, you should
15121 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15122 can silently drop packets on busy or unreliable networks, which will
15123 cause havoc with your debugging session.
15125 @item target remote | @var{command}
15126 @cindex pipe, @code{target remote} to
15127 Run @var{command} in the background and communicate with it using a
15128 pipe. The @var{command} is a shell command, to be parsed and expanded
15129 by the system's command shell, @code{/bin/sh}; it should expect remote
15130 protocol packets on its standard input, and send replies on its
15131 standard output. You could use this to run a stand-alone simulator
15132 that speaks the remote debugging protocol, to make net connections
15133 using programs like @code{ssh}, or for other similar tricks.
15135 If @var{command} closes its standard output (perhaps by exiting),
15136 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15137 program has already exited, this will have no effect.)
15141 Once the connection has been established, you can use all the usual
15142 commands to examine and change data. The remote program is already
15143 running; you can use @kbd{step} and @kbd{continue}, and you do not
15144 need to use @kbd{run}.
15146 @cindex interrupting remote programs
15147 @cindex remote programs, interrupting
15148 Whenever @value{GDBN} is waiting for the remote program, if you type the
15149 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15150 program. This may or may not succeed, depending in part on the hardware
15151 and the serial drivers the remote system uses. If you type the
15152 interrupt character once again, @value{GDBN} displays this prompt:
15155 Interrupted while waiting for the program.
15156 Give up (and stop debugging it)? (y or n)
15159 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15160 (If you decide you want to try again later, you can use @samp{target
15161 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15162 goes back to waiting.
15165 @kindex detach (remote)
15167 When you have finished debugging the remote program, you can use the
15168 @code{detach} command to release it from @value{GDBN} control.
15169 Detaching from the target normally resumes its execution, but the results
15170 will depend on your particular remote stub. After the @code{detach}
15171 command, @value{GDBN} is free to connect to another target.
15175 The @code{disconnect} command behaves like @code{detach}, except that
15176 the target is generally not resumed. It will wait for @value{GDBN}
15177 (this instance or another one) to connect and continue debugging. After
15178 the @code{disconnect} command, @value{GDBN} is again free to connect to
15181 @cindex send command to remote monitor
15182 @cindex extend @value{GDBN} for remote targets
15183 @cindex add new commands for external monitor
15185 @item monitor @var{cmd}
15186 This command allows you to send arbitrary commands directly to the
15187 remote monitor. Since @value{GDBN} doesn't care about the commands it
15188 sends like this, this command is the way to extend @value{GDBN}---you
15189 can add new commands that only the external monitor will understand
15193 @node File Transfer
15194 @section Sending files to a remote system
15195 @cindex remote target, file transfer
15196 @cindex file transfer
15197 @cindex sending files to remote systems
15199 Some remote targets offer the ability to transfer files over the same
15200 connection used to communicate with @value{GDBN}. This is convenient
15201 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15202 running @code{gdbserver} over a network interface. For other targets,
15203 e.g.@: embedded devices with only a single serial port, this may be
15204 the only way to upload or download files.
15206 Not all remote targets support these commands.
15210 @item remote put @var{hostfile} @var{targetfile}
15211 Copy file @var{hostfile} from the host system (the machine running
15212 @value{GDBN}) to @var{targetfile} on the target system.
15215 @item remote get @var{targetfile} @var{hostfile}
15216 Copy file @var{targetfile} from the target system to @var{hostfile}
15217 on the host system.
15219 @kindex remote delete
15220 @item remote delete @var{targetfile}
15221 Delete @var{targetfile} from the target system.
15226 @section Using the @code{gdbserver} Program
15229 @cindex remote connection without stubs
15230 @code{gdbserver} is a control program for Unix-like systems, which
15231 allows you to connect your program with a remote @value{GDBN} via
15232 @code{target remote}---but without linking in the usual debugging stub.
15234 @code{gdbserver} is not a complete replacement for the debugging stubs,
15235 because it requires essentially the same operating-system facilities
15236 that @value{GDBN} itself does. In fact, a system that can run
15237 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15238 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15239 because it is a much smaller program than @value{GDBN} itself. It is
15240 also easier to port than all of @value{GDBN}, so you may be able to get
15241 started more quickly on a new system by using @code{gdbserver}.
15242 Finally, if you develop code for real-time systems, you may find that
15243 the tradeoffs involved in real-time operation make it more convenient to
15244 do as much development work as possible on another system, for example
15245 by cross-compiling. You can use @code{gdbserver} to make a similar
15246 choice for debugging.
15248 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15249 or a TCP connection, using the standard @value{GDBN} remote serial
15253 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15254 Do not run @code{gdbserver} connected to any public network; a
15255 @value{GDBN} connection to @code{gdbserver} provides access to the
15256 target system with the same privileges as the user running
15260 @subsection Running @code{gdbserver}
15261 @cindex arguments, to @code{gdbserver}
15263 Run @code{gdbserver} on the target system. You need a copy of the
15264 program you want to debug, including any libraries it requires.
15265 @code{gdbserver} does not need your program's symbol table, so you can
15266 strip the program if necessary to save space. @value{GDBN} on the host
15267 system does all the symbol handling.
15269 To use the server, you must tell it how to communicate with @value{GDBN};
15270 the name of your program; and the arguments for your program. The usual
15274 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15277 @var{comm} is either a device name (to use a serial line) or a TCP
15278 hostname and portnumber. For example, to debug Emacs with the argument
15279 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15283 target> gdbserver /dev/com1 emacs foo.txt
15286 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15289 To use a TCP connection instead of a serial line:
15292 target> gdbserver host:2345 emacs foo.txt
15295 The only difference from the previous example is the first argument,
15296 specifying that you are communicating with the host @value{GDBN} via
15297 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15298 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15299 (Currently, the @samp{host} part is ignored.) You can choose any number
15300 you want for the port number as long as it does not conflict with any
15301 TCP ports already in use on the target system (for example, @code{23} is
15302 reserved for @code{telnet}).@footnote{If you choose a port number that
15303 conflicts with another service, @code{gdbserver} prints an error message
15304 and exits.} You must use the same port number with the host @value{GDBN}
15305 @code{target remote} command.
15307 @subsubsection Attaching to a Running Program
15309 On some targets, @code{gdbserver} can also attach to running programs.
15310 This is accomplished via the @code{--attach} argument. The syntax is:
15313 target> gdbserver --attach @var{comm} @var{pid}
15316 @var{pid} is the process ID of a currently running process. It isn't necessary
15317 to point @code{gdbserver} at a binary for the running process.
15320 @cindex attach to a program by name
15321 You can debug processes by name instead of process ID if your target has the
15322 @code{pidof} utility:
15325 target> gdbserver --attach @var{comm} `pidof @var{program}`
15328 In case more than one copy of @var{program} is running, or @var{program}
15329 has multiple threads, most versions of @code{pidof} support the
15330 @code{-s} option to only return the first process ID.
15332 @subsubsection Multi-Process Mode for @code{gdbserver}
15333 @cindex gdbserver, multiple processes
15334 @cindex multiple processes with gdbserver
15336 When you connect to @code{gdbserver} using @code{target remote},
15337 @code{gdbserver} debugs the specified program only once. When the
15338 program exits, or you detach from it, @value{GDBN} closes the connection
15339 and @code{gdbserver} exits.
15341 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15342 enters multi-process mode. When the debugged program exits, or you
15343 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15344 though no program is running. The @code{run} and @code{attach}
15345 commands instruct @code{gdbserver} to run or attach to a new program.
15346 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15347 remote exec-file}) to select the program to run. Command line
15348 arguments are supported, except for wildcard expansion and I/O
15349 redirection (@pxref{Arguments}).
15351 To start @code{gdbserver} without supplying an initial command to run
15352 or process ID to attach, use the @option{--multi} command line option.
15353 Then you can connect using @kbd{target extended-remote} and start
15354 the program you want to debug.
15356 @code{gdbserver} does not automatically exit in multi-process mode.
15357 You can terminate it by using @code{monitor exit}
15358 (@pxref{Monitor Commands for gdbserver}).
15360 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15362 The @option{--debug} option tells @code{gdbserver} to display extra
15363 status information about the debugging process. The
15364 @option{--remote-debug} option tells @code{gdbserver} to display
15365 remote protocol debug output. These options are intended for
15366 @code{gdbserver} development and for bug reports to the developers.
15368 The @option{--wrapper} option specifies a wrapper to launch programs
15369 for debugging. The option should be followed by the name of the
15370 wrapper, then any command-line arguments to pass to the wrapper, then
15371 @kbd{--} indicating the end of the wrapper arguments.
15373 @code{gdbserver} runs the specified wrapper program with a combined
15374 command line including the wrapper arguments, then the name of the
15375 program to debug, then any arguments to the program. The wrapper
15376 runs until it executes your program, and then @value{GDBN} gains control.
15378 You can use any program that eventually calls @code{execve} with
15379 its arguments as a wrapper. Several standard Unix utilities do
15380 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15381 with @code{exec "$@@"} will also work.
15383 For example, you can use @code{env} to pass an environment variable to
15384 the debugged program, without setting the variable in @code{gdbserver}'s
15388 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15391 @subsection Connecting to @code{gdbserver}
15393 Run @value{GDBN} on the host system.
15395 First make sure you have the necessary symbol files. Load symbols for
15396 your application using the @code{file} command before you connect. Use
15397 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15398 was compiled with the correct sysroot using @code{--with-sysroot}).
15400 The symbol file and target libraries must exactly match the executable
15401 and libraries on the target, with one exception: the files on the host
15402 system should not be stripped, even if the files on the target system
15403 are. Mismatched or missing files will lead to confusing results
15404 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15405 files may also prevent @code{gdbserver} from debugging multi-threaded
15408 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15409 For TCP connections, you must start up @code{gdbserver} prior to using
15410 the @code{target remote} command. Otherwise you may get an error whose
15411 text depends on the host system, but which usually looks something like
15412 @samp{Connection refused}. Don't use the @code{load}
15413 command in @value{GDBN} when using @code{gdbserver}, since the program is
15414 already on the target.
15416 @subsection Monitor Commands for @code{gdbserver}
15417 @cindex monitor commands, for @code{gdbserver}
15418 @anchor{Monitor Commands for gdbserver}
15420 During a @value{GDBN} session using @code{gdbserver}, you can use the
15421 @code{monitor} command to send special requests to @code{gdbserver}.
15422 Here are the available commands.
15426 List the available monitor commands.
15428 @item monitor set debug 0
15429 @itemx monitor set debug 1
15430 Disable or enable general debugging messages.
15432 @item monitor set remote-debug 0
15433 @itemx monitor set remote-debug 1
15434 Disable or enable specific debugging messages associated with the remote
15435 protocol (@pxref{Remote Protocol}).
15437 @item monitor set libthread-db-search-path [PATH]
15438 @cindex gdbserver, search path for @code{libthread_db}
15439 When this command is issued, @var{path} is a colon-separated list of
15440 directories to search for @code{libthread_db} (@pxref{Threads,,set
15441 libthread-db-search-path}). If you omit @var{path},
15442 @samp{libthread-db-search-path} will be reset to an empty list.
15445 Tell gdbserver to exit immediately. This command should be followed by
15446 @code{disconnect} to close the debugging session. @code{gdbserver} will
15447 detach from any attached processes and kill any processes it created.
15448 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15449 of a multi-process mode debug session.
15453 @node Remote Configuration
15454 @section Remote Configuration
15457 @kindex show remote
15458 This section documents the configuration options available when
15459 debugging remote programs. For the options related to the File I/O
15460 extensions of the remote protocol, see @ref{system,
15461 system-call-allowed}.
15464 @item set remoteaddresssize @var{bits}
15465 @cindex address size for remote targets
15466 @cindex bits in remote address
15467 Set the maximum size of address in a memory packet to the specified
15468 number of bits. @value{GDBN} will mask off the address bits above
15469 that number, when it passes addresses to the remote target. The
15470 default value is the number of bits in the target's address.
15472 @item show remoteaddresssize
15473 Show the current value of remote address size in bits.
15475 @item set remotebaud @var{n}
15476 @cindex baud rate for remote targets
15477 Set the baud rate for the remote serial I/O to @var{n} baud. The
15478 value is used to set the speed of the serial port used for debugging
15481 @item show remotebaud
15482 Show the current speed of the remote connection.
15484 @item set remotebreak
15485 @cindex interrupt remote programs
15486 @cindex BREAK signal instead of Ctrl-C
15487 @anchor{set remotebreak}
15488 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15489 when you type @kbd{Ctrl-c} to interrupt the program running
15490 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15491 character instead. The default is off, since most remote systems
15492 expect to see @samp{Ctrl-C} as the interrupt signal.
15494 @item show remotebreak
15495 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15496 interrupt the remote program.
15498 @item set remoteflow on
15499 @itemx set remoteflow off
15500 @kindex set remoteflow
15501 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15502 on the serial port used to communicate to the remote target.
15504 @item show remoteflow
15505 @kindex show remoteflow
15506 Show the current setting of hardware flow control.
15508 @item set remotelogbase @var{base}
15509 Set the base (a.k.a.@: radix) of logging serial protocol
15510 communications to @var{base}. Supported values of @var{base} are:
15511 @code{ascii}, @code{octal}, and @code{hex}. The default is
15514 @item show remotelogbase
15515 Show the current setting of the radix for logging remote serial
15518 @item set remotelogfile @var{file}
15519 @cindex record serial communications on file
15520 Record remote serial communications on the named @var{file}. The
15521 default is not to record at all.
15523 @item show remotelogfile.
15524 Show the current setting of the file name on which to record the
15525 serial communications.
15527 @item set remotetimeout @var{num}
15528 @cindex timeout for serial communications
15529 @cindex remote timeout
15530 Set the timeout limit to wait for the remote target to respond to
15531 @var{num} seconds. The default is 2 seconds.
15533 @item show remotetimeout
15534 Show the current number of seconds to wait for the remote target
15537 @cindex limit hardware breakpoints and watchpoints
15538 @cindex remote target, limit break- and watchpoints
15539 @anchor{set remote hardware-watchpoint-limit}
15540 @anchor{set remote hardware-breakpoint-limit}
15541 @item set remote hardware-watchpoint-limit @var{limit}
15542 @itemx set remote hardware-breakpoint-limit @var{limit}
15543 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15544 watchpoints. A limit of -1, the default, is treated as unlimited.
15546 @item set remote exec-file @var{filename}
15547 @itemx show remote exec-file
15548 @anchor{set remote exec-file}
15549 @cindex executable file, for remote target
15550 Select the file used for @code{run} with @code{target
15551 extended-remote}. This should be set to a filename valid on the
15552 target system. If it is not set, the target will use a default
15553 filename (e.g.@: the last program run).
15555 @item set remote interrupt-sequence
15556 @cindex interrupt remote programs
15557 @cindex select Ctrl-C, BREAK or BREAK-g
15558 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15559 @samp{BREAK-g} as the
15560 sequence to the remote target in order to interrupt the execution.
15561 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15562 is high level of serial line for some certain time.
15563 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15564 It is @code{BREAK} signal followed by character @code{g}.
15566 @item show interrupt-sequence
15567 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15568 is sent by @value{GDBN} to interrupt the remote program.
15569 @code{BREAK-g} is BREAK signal followed by @code{g} and
15570 also known as Magic SysRq g.
15572 @item set remote interrupt-on-connect
15573 @cindex send interrupt-sequence on start
15574 Specify whether interrupt-sequence is sent to remote target when
15575 @value{GDBN} connects to it. This is mostly needed when you debug
15576 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15577 which is known as Magic SysRq g in order to connect @value{GDBN}.
15579 @item show interrupt-on-connect
15580 Show whether interrupt-sequence is sent
15581 to remote target when @value{GDBN} connects to it.
15585 @item set tcp auto-retry on
15586 @cindex auto-retry, for remote TCP target
15587 Enable auto-retry for remote TCP connections. This is useful if the remote
15588 debugging agent is launched in parallel with @value{GDBN}; there is a race
15589 condition because the agent may not become ready to accept the connection
15590 before @value{GDBN} attempts to connect. When auto-retry is
15591 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15592 to establish the connection using the timeout specified by
15593 @code{set tcp connect-timeout}.
15595 @item set tcp auto-retry off
15596 Do not auto-retry failed TCP connections.
15598 @item show tcp auto-retry
15599 Show the current auto-retry setting.
15601 @item set tcp connect-timeout @var{seconds}
15602 @cindex connection timeout, for remote TCP target
15603 @cindex timeout, for remote target connection
15604 Set the timeout for establishing a TCP connection to the remote target to
15605 @var{seconds}. The timeout affects both polling to retry failed connections
15606 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15607 that are merely slow to complete, and represents an approximate cumulative
15610 @item show tcp connect-timeout
15611 Show the current connection timeout setting.
15614 @cindex remote packets, enabling and disabling
15615 The @value{GDBN} remote protocol autodetects the packets supported by
15616 your debugging stub. If you need to override the autodetection, you
15617 can use these commands to enable or disable individual packets. Each
15618 packet can be set to @samp{on} (the remote target supports this
15619 packet), @samp{off} (the remote target does not support this packet),
15620 or @samp{auto} (detect remote target support for this packet). They
15621 all default to @samp{auto}. For more information about each packet,
15622 see @ref{Remote Protocol}.
15624 During normal use, you should not have to use any of these commands.
15625 If you do, that may be a bug in your remote debugging stub, or a bug
15626 in @value{GDBN}. You may want to report the problem to the
15627 @value{GDBN} developers.
15629 For each packet @var{name}, the command to enable or disable the
15630 packet is @code{set remote @var{name}-packet}. The available settings
15633 @multitable @columnfractions 0.28 0.32 0.25
15636 @tab Related Features
15638 @item @code{fetch-register}
15640 @tab @code{info registers}
15642 @item @code{set-register}
15646 @item @code{binary-download}
15648 @tab @code{load}, @code{set}
15650 @item @code{read-aux-vector}
15651 @tab @code{qXfer:auxv:read}
15652 @tab @code{info auxv}
15654 @item @code{symbol-lookup}
15655 @tab @code{qSymbol}
15656 @tab Detecting multiple threads
15658 @item @code{attach}
15659 @tab @code{vAttach}
15662 @item @code{verbose-resume}
15664 @tab Stepping or resuming multiple threads
15670 @item @code{software-breakpoint}
15674 @item @code{hardware-breakpoint}
15678 @item @code{write-watchpoint}
15682 @item @code{read-watchpoint}
15686 @item @code{access-watchpoint}
15690 @item @code{target-features}
15691 @tab @code{qXfer:features:read}
15692 @tab @code{set architecture}
15694 @item @code{library-info}
15695 @tab @code{qXfer:libraries:read}
15696 @tab @code{info sharedlibrary}
15698 @item @code{memory-map}
15699 @tab @code{qXfer:memory-map:read}
15700 @tab @code{info mem}
15702 @item @code{read-spu-object}
15703 @tab @code{qXfer:spu:read}
15704 @tab @code{info spu}
15706 @item @code{write-spu-object}
15707 @tab @code{qXfer:spu:write}
15708 @tab @code{info spu}
15710 @item @code{read-siginfo-object}
15711 @tab @code{qXfer:siginfo:read}
15712 @tab @code{print $_siginfo}
15714 @item @code{write-siginfo-object}
15715 @tab @code{qXfer:siginfo:write}
15716 @tab @code{set $_siginfo}
15718 @item @code{threads}
15719 @tab @code{qXfer:threads:read}
15720 @tab @code{info threads}
15722 @item @code{get-thread-local-@*storage-address}
15723 @tab @code{qGetTLSAddr}
15724 @tab Displaying @code{__thread} variables
15726 @item @code{search-memory}
15727 @tab @code{qSearch:memory}
15730 @item @code{supported-packets}
15731 @tab @code{qSupported}
15732 @tab Remote communications parameters
15734 @item @code{pass-signals}
15735 @tab @code{QPassSignals}
15736 @tab @code{handle @var{signal}}
15738 @item @code{hostio-close-packet}
15739 @tab @code{vFile:close}
15740 @tab @code{remote get}, @code{remote put}
15742 @item @code{hostio-open-packet}
15743 @tab @code{vFile:open}
15744 @tab @code{remote get}, @code{remote put}
15746 @item @code{hostio-pread-packet}
15747 @tab @code{vFile:pread}
15748 @tab @code{remote get}, @code{remote put}
15750 @item @code{hostio-pwrite-packet}
15751 @tab @code{vFile:pwrite}
15752 @tab @code{remote get}, @code{remote put}
15754 @item @code{hostio-unlink-packet}
15755 @tab @code{vFile:unlink}
15756 @tab @code{remote delete}
15758 @item @code{noack-packet}
15759 @tab @code{QStartNoAckMode}
15760 @tab Packet acknowledgment
15762 @item @code{osdata}
15763 @tab @code{qXfer:osdata:read}
15764 @tab @code{info os}
15766 @item @code{query-attached}
15767 @tab @code{qAttached}
15768 @tab Querying remote process attach state.
15772 @section Implementing a Remote Stub
15774 @cindex debugging stub, example
15775 @cindex remote stub, example
15776 @cindex stub example, remote debugging
15777 The stub files provided with @value{GDBN} implement the target side of the
15778 communication protocol, and the @value{GDBN} side is implemented in the
15779 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15780 these subroutines to communicate, and ignore the details. (If you're
15781 implementing your own stub file, you can still ignore the details: start
15782 with one of the existing stub files. @file{sparc-stub.c} is the best
15783 organized, and therefore the easiest to read.)
15785 @cindex remote serial debugging, overview
15786 To debug a program running on another machine (the debugging
15787 @dfn{target} machine), you must first arrange for all the usual
15788 prerequisites for the program to run by itself. For example, for a C
15793 A startup routine to set up the C runtime environment; these usually
15794 have a name like @file{crt0}. The startup routine may be supplied by
15795 your hardware supplier, or you may have to write your own.
15798 A C subroutine library to support your program's
15799 subroutine calls, notably managing input and output.
15802 A way of getting your program to the other machine---for example, a
15803 download program. These are often supplied by the hardware
15804 manufacturer, but you may have to write your own from hardware
15808 The next step is to arrange for your program to use a serial port to
15809 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15810 machine). In general terms, the scheme looks like this:
15814 @value{GDBN} already understands how to use this protocol; when everything
15815 else is set up, you can simply use the @samp{target remote} command
15816 (@pxref{Targets,,Specifying a Debugging Target}).
15818 @item On the target,
15819 you must link with your program a few special-purpose subroutines that
15820 implement the @value{GDBN} remote serial protocol. The file containing these
15821 subroutines is called a @dfn{debugging stub}.
15823 On certain remote targets, you can use an auxiliary program
15824 @code{gdbserver} instead of linking a stub into your program.
15825 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15828 The debugging stub is specific to the architecture of the remote
15829 machine; for example, use @file{sparc-stub.c} to debug programs on
15832 @cindex remote serial stub list
15833 These working remote stubs are distributed with @value{GDBN}:
15838 @cindex @file{i386-stub.c}
15841 For Intel 386 and compatible architectures.
15844 @cindex @file{m68k-stub.c}
15845 @cindex Motorola 680x0
15847 For Motorola 680x0 architectures.
15850 @cindex @file{sh-stub.c}
15853 For Renesas SH architectures.
15856 @cindex @file{sparc-stub.c}
15858 For @sc{sparc} architectures.
15860 @item sparcl-stub.c
15861 @cindex @file{sparcl-stub.c}
15864 For Fujitsu @sc{sparclite} architectures.
15868 The @file{README} file in the @value{GDBN} distribution may list other
15869 recently added stubs.
15872 * Stub Contents:: What the stub can do for you
15873 * Bootstrapping:: What you must do for the stub
15874 * Debug Session:: Putting it all together
15877 @node Stub Contents
15878 @subsection What the Stub Can Do for You
15880 @cindex remote serial stub
15881 The debugging stub for your architecture supplies these three
15885 @item set_debug_traps
15886 @findex set_debug_traps
15887 @cindex remote serial stub, initialization
15888 This routine arranges for @code{handle_exception} to run when your
15889 program stops. You must call this subroutine explicitly near the
15890 beginning of your program.
15892 @item handle_exception
15893 @findex handle_exception
15894 @cindex remote serial stub, main routine
15895 This is the central workhorse, but your program never calls it
15896 explicitly---the setup code arranges for @code{handle_exception} to
15897 run when a trap is triggered.
15899 @code{handle_exception} takes control when your program stops during
15900 execution (for example, on a breakpoint), and mediates communications
15901 with @value{GDBN} on the host machine. This is where the communications
15902 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15903 representative on the target machine. It begins by sending summary
15904 information on the state of your program, then continues to execute,
15905 retrieving and transmitting any information @value{GDBN} needs, until you
15906 execute a @value{GDBN} command that makes your program resume; at that point,
15907 @code{handle_exception} returns control to your own code on the target
15911 @cindex @code{breakpoint} subroutine, remote
15912 Use this auxiliary subroutine to make your program contain a
15913 breakpoint. Depending on the particular situation, this may be the only
15914 way for @value{GDBN} to get control. For instance, if your target
15915 machine has some sort of interrupt button, you won't need to call this;
15916 pressing the interrupt button transfers control to
15917 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15918 simply receiving characters on the serial port may also trigger a trap;
15919 again, in that situation, you don't need to call @code{breakpoint} from
15920 your own program---simply running @samp{target remote} from the host
15921 @value{GDBN} session gets control.
15923 Call @code{breakpoint} if none of these is true, or if you simply want
15924 to make certain your program stops at a predetermined point for the
15925 start of your debugging session.
15928 @node Bootstrapping
15929 @subsection What You Must Do for the Stub
15931 @cindex remote stub, support routines
15932 The debugging stubs that come with @value{GDBN} are set up for a particular
15933 chip architecture, but they have no information about the rest of your
15934 debugging target machine.
15936 First of all you need to tell the stub how to communicate with the
15940 @item int getDebugChar()
15941 @findex getDebugChar
15942 Write this subroutine to read a single character from the serial port.
15943 It may be identical to @code{getchar} for your target system; a
15944 different name is used to allow you to distinguish the two if you wish.
15946 @item void putDebugChar(int)
15947 @findex putDebugChar
15948 Write this subroutine to write a single character to the serial port.
15949 It may be identical to @code{putchar} for your target system; a
15950 different name is used to allow you to distinguish the two if you wish.
15953 @cindex control C, and remote debugging
15954 @cindex interrupting remote targets
15955 If you want @value{GDBN} to be able to stop your program while it is
15956 running, you need to use an interrupt-driven serial driver, and arrange
15957 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15958 character). That is the character which @value{GDBN} uses to tell the
15959 remote system to stop.
15961 Getting the debugging target to return the proper status to @value{GDBN}
15962 probably requires changes to the standard stub; one quick and dirty way
15963 is to just execute a breakpoint instruction (the ``dirty'' part is that
15964 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15966 Other routines you need to supply are:
15969 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15970 @findex exceptionHandler
15971 Write this function to install @var{exception_address} in the exception
15972 handling tables. You need to do this because the stub does not have any
15973 way of knowing what the exception handling tables on your target system
15974 are like (for example, the processor's table might be in @sc{rom},
15975 containing entries which point to a table in @sc{ram}).
15976 @var{exception_number} is the exception number which should be changed;
15977 its meaning is architecture-dependent (for example, different numbers
15978 might represent divide by zero, misaligned access, etc). When this
15979 exception occurs, control should be transferred directly to
15980 @var{exception_address}, and the processor state (stack, registers,
15981 and so on) should be just as it is when a processor exception occurs. So if
15982 you want to use a jump instruction to reach @var{exception_address}, it
15983 should be a simple jump, not a jump to subroutine.
15985 For the 386, @var{exception_address} should be installed as an interrupt
15986 gate so that interrupts are masked while the handler runs. The gate
15987 should be at privilege level 0 (the most privileged level). The
15988 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15989 help from @code{exceptionHandler}.
15991 @item void flush_i_cache()
15992 @findex flush_i_cache
15993 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15994 instruction cache, if any, on your target machine. If there is no
15995 instruction cache, this subroutine may be a no-op.
15997 On target machines that have instruction caches, @value{GDBN} requires this
15998 function to make certain that the state of your program is stable.
16002 You must also make sure this library routine is available:
16005 @item void *memset(void *, int, int)
16007 This is the standard library function @code{memset} that sets an area of
16008 memory to a known value. If you have one of the free versions of
16009 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16010 either obtain it from your hardware manufacturer, or write your own.
16013 If you do not use the GNU C compiler, you may need other standard
16014 library subroutines as well; this varies from one stub to another,
16015 but in general the stubs are likely to use any of the common library
16016 subroutines which @code{@value{NGCC}} generates as inline code.
16019 @node Debug Session
16020 @subsection Putting it All Together
16022 @cindex remote serial debugging summary
16023 In summary, when your program is ready to debug, you must follow these
16028 Make sure you have defined the supporting low-level routines
16029 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16031 @code{getDebugChar}, @code{putDebugChar},
16032 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16036 Insert these lines near the top of your program:
16044 For the 680x0 stub only, you need to provide a variable called
16045 @code{exceptionHook}. Normally you just use:
16048 void (*exceptionHook)() = 0;
16052 but if before calling @code{set_debug_traps}, you set it to point to a
16053 function in your program, that function is called when
16054 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16055 error). The function indicated by @code{exceptionHook} is called with
16056 one parameter: an @code{int} which is the exception number.
16059 Compile and link together: your program, the @value{GDBN} debugging stub for
16060 your target architecture, and the supporting subroutines.
16063 Make sure you have a serial connection between your target machine and
16064 the @value{GDBN} host, and identify the serial port on the host.
16067 @c The "remote" target now provides a `load' command, so we should
16068 @c document that. FIXME.
16069 Download your program to your target machine (or get it there by
16070 whatever means the manufacturer provides), and start it.
16073 Start @value{GDBN} on the host, and connect to the target
16074 (@pxref{Connecting,,Connecting to a Remote Target}).
16078 @node Configurations
16079 @chapter Configuration-Specific Information
16081 While nearly all @value{GDBN} commands are available for all native and
16082 cross versions of the debugger, there are some exceptions. This chapter
16083 describes things that are only available in certain configurations.
16085 There are three major categories of configurations: native
16086 configurations, where the host and target are the same, embedded
16087 operating system configurations, which are usually the same for several
16088 different processor architectures, and bare embedded processors, which
16089 are quite different from each other.
16094 * Embedded Processors::
16101 This section describes details specific to particular native
16106 * BSD libkvm Interface:: Debugging BSD kernel memory images
16107 * SVR4 Process Information:: SVR4 process information
16108 * DJGPP Native:: Features specific to the DJGPP port
16109 * Cygwin Native:: Features specific to the Cygwin port
16110 * Hurd Native:: Features specific to @sc{gnu} Hurd
16111 * Neutrino:: Features specific to QNX Neutrino
16112 * Darwin:: Features specific to Darwin
16118 On HP-UX systems, if you refer to a function or variable name that
16119 begins with a dollar sign, @value{GDBN} searches for a user or system
16120 name first, before it searches for a convenience variable.
16123 @node BSD libkvm Interface
16124 @subsection BSD libkvm Interface
16127 @cindex kernel memory image
16128 @cindex kernel crash dump
16130 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16131 interface that provides a uniform interface for accessing kernel virtual
16132 memory images, including live systems and crash dumps. @value{GDBN}
16133 uses this interface to allow you to debug live kernels and kernel crash
16134 dumps on many native BSD configurations. This is implemented as a
16135 special @code{kvm} debugging target. For debugging a live system, load
16136 the currently running kernel into @value{GDBN} and connect to the
16140 (@value{GDBP}) @b{target kvm}
16143 For debugging crash dumps, provide the file name of the crash dump as an
16147 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16150 Once connected to the @code{kvm} target, the following commands are
16156 Set current context from the @dfn{Process Control Block} (PCB) address.
16159 Set current context from proc address. This command isn't available on
16160 modern FreeBSD systems.
16163 @node SVR4 Process Information
16164 @subsection SVR4 Process Information
16166 @cindex examine process image
16167 @cindex process info via @file{/proc}
16169 Many versions of SVR4 and compatible systems provide a facility called
16170 @samp{/proc} that can be used to examine the image of a running
16171 process using file-system subroutines. If @value{GDBN} is configured
16172 for an operating system with this facility, the command @code{info
16173 proc} is available to report information about the process running
16174 your program, or about any process running on your system. @code{info
16175 proc} works only on SVR4 systems that include the @code{procfs} code.
16176 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16177 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16183 @itemx info proc @var{process-id}
16184 Summarize available information about any running process. If a
16185 process ID is specified by @var{process-id}, display information about
16186 that process; otherwise display information about the program being
16187 debugged. The summary includes the debugged process ID, the command
16188 line used to invoke it, its current working directory, and its
16189 executable file's absolute file name.
16191 On some systems, @var{process-id} can be of the form
16192 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16193 within a process. If the optional @var{pid} part is missing, it means
16194 a thread from the process being debugged (the leading @samp{/} still
16195 needs to be present, or else @value{GDBN} will interpret the number as
16196 a process ID rather than a thread ID).
16198 @item info proc mappings
16199 @cindex memory address space mappings
16200 Report the memory address space ranges accessible in the program, with
16201 information on whether the process has read, write, or execute access
16202 rights to each range. On @sc{gnu}/Linux systems, each memory range
16203 includes the object file which is mapped to that range, instead of the
16204 memory access rights to that range.
16206 @item info proc stat
16207 @itemx info proc status
16208 @cindex process detailed status information
16209 These subcommands are specific to @sc{gnu}/Linux systems. They show
16210 the process-related information, including the user ID and group ID;
16211 how many threads are there in the process; its virtual memory usage;
16212 the signals that are pending, blocked, and ignored; its TTY; its
16213 consumption of system and user time; its stack size; its @samp{nice}
16214 value; etc. For more information, see the @samp{proc} man page
16215 (type @kbd{man 5 proc} from your shell prompt).
16217 @item info proc all
16218 Show all the information about the process described under all of the
16219 above @code{info proc} subcommands.
16222 @comment These sub-options of 'info proc' were not included when
16223 @comment procfs.c was re-written. Keep their descriptions around
16224 @comment against the day when someone finds the time to put them back in.
16225 @kindex info proc times
16226 @item info proc times
16227 Starting time, user CPU time, and system CPU time for your program and
16230 @kindex info proc id
16232 Report on the process IDs related to your program: its own process ID,
16233 the ID of its parent, the process group ID, and the session ID.
16236 @item set procfs-trace
16237 @kindex set procfs-trace
16238 @cindex @code{procfs} API calls
16239 This command enables and disables tracing of @code{procfs} API calls.
16241 @item show procfs-trace
16242 @kindex show procfs-trace
16243 Show the current state of @code{procfs} API call tracing.
16245 @item set procfs-file @var{file}
16246 @kindex set procfs-file
16247 Tell @value{GDBN} to write @code{procfs} API trace to the named
16248 @var{file}. @value{GDBN} appends the trace info to the previous
16249 contents of the file. The default is to display the trace on the
16252 @item show procfs-file
16253 @kindex show procfs-file
16254 Show the file to which @code{procfs} API trace is written.
16256 @item proc-trace-entry
16257 @itemx proc-trace-exit
16258 @itemx proc-untrace-entry
16259 @itemx proc-untrace-exit
16260 @kindex proc-trace-entry
16261 @kindex proc-trace-exit
16262 @kindex proc-untrace-entry
16263 @kindex proc-untrace-exit
16264 These commands enable and disable tracing of entries into and exits
16265 from the @code{syscall} interface.
16268 @kindex info pidlist
16269 @cindex process list, QNX Neutrino
16270 For QNX Neutrino only, this command displays the list of all the
16271 processes and all the threads within each process.
16274 @kindex info meminfo
16275 @cindex mapinfo list, QNX Neutrino
16276 For QNX Neutrino only, this command displays the list of all mapinfos.
16280 @subsection Features for Debugging @sc{djgpp} Programs
16281 @cindex @sc{djgpp} debugging
16282 @cindex native @sc{djgpp} debugging
16283 @cindex MS-DOS-specific commands
16286 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16287 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16288 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16289 top of real-mode DOS systems and their emulations.
16291 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16292 defines a few commands specific to the @sc{djgpp} port. This
16293 subsection describes those commands.
16298 This is a prefix of @sc{djgpp}-specific commands which print
16299 information about the target system and important OS structures.
16302 @cindex MS-DOS system info
16303 @cindex free memory information (MS-DOS)
16304 @item info dos sysinfo
16305 This command displays assorted information about the underlying
16306 platform: the CPU type and features, the OS version and flavor, the
16307 DPMI version, and the available conventional and DPMI memory.
16312 @cindex segment descriptor tables
16313 @cindex descriptor tables display
16315 @itemx info dos ldt
16316 @itemx info dos idt
16317 These 3 commands display entries from, respectively, Global, Local,
16318 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16319 tables are data structures which store a descriptor for each segment
16320 that is currently in use. The segment's selector is an index into a
16321 descriptor table; the table entry for that index holds the
16322 descriptor's base address and limit, and its attributes and access
16325 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16326 segment (used for both data and the stack), and a DOS segment (which
16327 allows access to DOS/BIOS data structures and absolute addresses in
16328 conventional memory). However, the DPMI host will usually define
16329 additional segments in order to support the DPMI environment.
16331 @cindex garbled pointers
16332 These commands allow to display entries from the descriptor tables.
16333 Without an argument, all entries from the specified table are
16334 displayed. An argument, which should be an integer expression, means
16335 display a single entry whose index is given by the argument. For
16336 example, here's a convenient way to display information about the
16337 debugged program's data segment:
16340 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16341 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16345 This comes in handy when you want to see whether a pointer is outside
16346 the data segment's limit (i.e.@: @dfn{garbled}).
16348 @cindex page tables display (MS-DOS)
16350 @itemx info dos pte
16351 These two commands display entries from, respectively, the Page
16352 Directory and the Page Tables. Page Directories and Page Tables are
16353 data structures which control how virtual memory addresses are mapped
16354 into physical addresses. A Page Table includes an entry for every
16355 page of memory that is mapped into the program's address space; there
16356 may be several Page Tables, each one holding up to 4096 entries. A
16357 Page Directory has up to 4096 entries, one each for every Page Table
16358 that is currently in use.
16360 Without an argument, @kbd{info dos pde} displays the entire Page
16361 Directory, and @kbd{info dos pte} displays all the entries in all of
16362 the Page Tables. An argument, an integer expression, given to the
16363 @kbd{info dos pde} command means display only that entry from the Page
16364 Directory table. An argument given to the @kbd{info dos pte} command
16365 means display entries from a single Page Table, the one pointed to by
16366 the specified entry in the Page Directory.
16368 @cindex direct memory access (DMA) on MS-DOS
16369 These commands are useful when your program uses @dfn{DMA} (Direct
16370 Memory Access), which needs physical addresses to program the DMA
16373 These commands are supported only with some DPMI servers.
16375 @cindex physical address from linear address
16376 @item info dos address-pte @var{addr}
16377 This command displays the Page Table entry for a specified linear
16378 address. The argument @var{addr} is a linear address which should
16379 already have the appropriate segment's base address added to it,
16380 because this command accepts addresses which may belong to @emph{any}
16381 segment. For example, here's how to display the Page Table entry for
16382 the page where a variable @code{i} is stored:
16385 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16386 @exdent @code{Page Table entry for address 0x11a00d30:}
16387 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16391 This says that @code{i} is stored at offset @code{0xd30} from the page
16392 whose physical base address is @code{0x02698000}, and shows all the
16393 attributes of that page.
16395 Note that you must cast the addresses of variables to a @code{char *},
16396 since otherwise the value of @code{__djgpp_base_address}, the base
16397 address of all variables and functions in a @sc{djgpp} program, will
16398 be added using the rules of C pointer arithmetics: if @code{i} is
16399 declared an @code{int}, @value{GDBN} will add 4 times the value of
16400 @code{__djgpp_base_address} to the address of @code{i}.
16402 Here's another example, it displays the Page Table entry for the
16406 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16407 @exdent @code{Page Table entry for address 0x29110:}
16408 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16412 (The @code{+ 3} offset is because the transfer buffer's address is the
16413 3rd member of the @code{_go32_info_block} structure.) The output
16414 clearly shows that this DPMI server maps the addresses in conventional
16415 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16416 linear (@code{0x29110}) addresses are identical.
16418 This command is supported only with some DPMI servers.
16421 @cindex DOS serial data link, remote debugging
16422 In addition to native debugging, the DJGPP port supports remote
16423 debugging via a serial data link. The following commands are specific
16424 to remote serial debugging in the DJGPP port of @value{GDBN}.
16427 @kindex set com1base
16428 @kindex set com1irq
16429 @kindex set com2base
16430 @kindex set com2irq
16431 @kindex set com3base
16432 @kindex set com3irq
16433 @kindex set com4base
16434 @kindex set com4irq
16435 @item set com1base @var{addr}
16436 This command sets the base I/O port address of the @file{COM1} serial
16439 @item set com1irq @var{irq}
16440 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16441 for the @file{COM1} serial port.
16443 There are similar commands @samp{set com2base}, @samp{set com3irq},
16444 etc.@: for setting the port address and the @code{IRQ} lines for the
16447 @kindex show com1base
16448 @kindex show com1irq
16449 @kindex show com2base
16450 @kindex show com2irq
16451 @kindex show com3base
16452 @kindex show com3irq
16453 @kindex show com4base
16454 @kindex show com4irq
16455 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16456 display the current settings of the base address and the @code{IRQ}
16457 lines used by the COM ports.
16460 @kindex info serial
16461 @cindex DOS serial port status
16462 This command prints the status of the 4 DOS serial ports. For each
16463 port, it prints whether it's active or not, its I/O base address and
16464 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16465 counts of various errors encountered so far.
16469 @node Cygwin Native
16470 @subsection Features for Debugging MS Windows PE Executables
16471 @cindex MS Windows debugging
16472 @cindex native Cygwin debugging
16473 @cindex Cygwin-specific commands
16475 @value{GDBN} supports native debugging of MS Windows programs, including
16476 DLLs with and without symbolic debugging information.
16478 @cindex Ctrl-BREAK, MS-Windows
16479 @cindex interrupt debuggee on MS-Windows
16480 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16481 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16482 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16483 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16484 sequence, which can be used to interrupt the debuggee even if it
16487 There are various additional Cygwin-specific commands, described in
16488 this section. Working with DLLs that have no debugging symbols is
16489 described in @ref{Non-debug DLL Symbols}.
16494 This is a prefix of MS Windows-specific commands which print
16495 information about the target system and important OS structures.
16497 @item info w32 selector
16498 This command displays information returned by
16499 the Win32 API @code{GetThreadSelectorEntry} function.
16500 It takes an optional argument that is evaluated to
16501 a long value to give the information about this given selector.
16502 Without argument, this command displays information
16503 about the six segment registers.
16507 This is a Cygwin-specific alias of @code{info shared}.
16509 @kindex dll-symbols
16511 This command loads symbols from a dll similarly to
16512 add-sym command but without the need to specify a base address.
16514 @kindex set cygwin-exceptions
16515 @cindex debugging the Cygwin DLL
16516 @cindex Cygwin DLL, debugging
16517 @item set cygwin-exceptions @var{mode}
16518 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16519 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16520 @value{GDBN} will delay recognition of exceptions, and may ignore some
16521 exceptions which seem to be caused by internal Cygwin DLL
16522 ``bookkeeping''. This option is meant primarily for debugging the
16523 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16524 @value{GDBN} users with false @code{SIGSEGV} signals.
16526 @kindex show cygwin-exceptions
16527 @item show cygwin-exceptions
16528 Displays whether @value{GDBN} will break on exceptions that happen
16529 inside the Cygwin DLL itself.
16531 @kindex set new-console
16532 @item set new-console @var{mode}
16533 If @var{mode} is @code{on} the debuggee will
16534 be started in a new console on next start.
16535 If @var{mode} is @code{off}, the debuggee will
16536 be started in the same console as the debugger.
16538 @kindex show new-console
16539 @item show new-console
16540 Displays whether a new console is used
16541 when the debuggee is started.
16543 @kindex set new-group
16544 @item set new-group @var{mode}
16545 This boolean value controls whether the debuggee should
16546 start a new group or stay in the same group as the debugger.
16547 This affects the way the Windows OS handles
16550 @kindex show new-group
16551 @item show new-group
16552 Displays current value of new-group boolean.
16554 @kindex set debugevents
16555 @item set debugevents
16556 This boolean value adds debug output concerning kernel events related
16557 to the debuggee seen by the debugger. This includes events that
16558 signal thread and process creation and exit, DLL loading and
16559 unloading, console interrupts, and debugging messages produced by the
16560 Windows @code{OutputDebugString} API call.
16562 @kindex set debugexec
16563 @item set debugexec
16564 This boolean value adds debug output concerning execute events
16565 (such as resume thread) seen by the debugger.
16567 @kindex set debugexceptions
16568 @item set debugexceptions
16569 This boolean value adds debug output concerning exceptions in the
16570 debuggee seen by the debugger.
16572 @kindex set debugmemory
16573 @item set debugmemory
16574 This boolean value adds debug output concerning debuggee memory reads
16575 and writes by the debugger.
16579 This boolean values specifies whether the debuggee is called
16580 via a shell or directly (default value is on).
16584 Displays if the debuggee will be started with a shell.
16589 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16592 @node Non-debug DLL Symbols
16593 @subsubsection Support for DLLs without Debugging Symbols
16594 @cindex DLLs with no debugging symbols
16595 @cindex Minimal symbols and DLLs
16597 Very often on windows, some of the DLLs that your program relies on do
16598 not include symbolic debugging information (for example,
16599 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16600 symbols in a DLL, it relies on the minimal amount of symbolic
16601 information contained in the DLL's export table. This section
16602 describes working with such symbols, known internally to @value{GDBN} as
16603 ``minimal symbols''.
16605 Note that before the debugged program has started execution, no DLLs
16606 will have been loaded. The easiest way around this problem is simply to
16607 start the program --- either by setting a breakpoint or letting the
16608 program run once to completion. It is also possible to force
16609 @value{GDBN} to load a particular DLL before starting the executable ---
16610 see the shared library information in @ref{Files}, or the
16611 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16612 explicitly loading symbols from a DLL with no debugging information will
16613 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16614 which may adversely affect symbol lookup performance.
16616 @subsubsection DLL Name Prefixes
16618 In keeping with the naming conventions used by the Microsoft debugging
16619 tools, DLL export symbols are made available with a prefix based on the
16620 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16621 also entered into the symbol table, so @code{CreateFileA} is often
16622 sufficient. In some cases there will be name clashes within a program
16623 (particularly if the executable itself includes full debugging symbols)
16624 necessitating the use of the fully qualified name when referring to the
16625 contents of the DLL. Use single-quotes around the name to avoid the
16626 exclamation mark (``!'') being interpreted as a language operator.
16628 Note that the internal name of the DLL may be all upper-case, even
16629 though the file name of the DLL is lower-case, or vice-versa. Since
16630 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16631 some confusion. If in doubt, try the @code{info functions} and
16632 @code{info variables} commands or even @code{maint print msymbols}
16633 (@pxref{Symbols}). Here's an example:
16636 (@value{GDBP}) info function CreateFileA
16637 All functions matching regular expression "CreateFileA":
16639 Non-debugging symbols:
16640 0x77e885f4 CreateFileA
16641 0x77e885f4 KERNEL32!CreateFileA
16645 (@value{GDBP}) info function !
16646 All functions matching regular expression "!":
16648 Non-debugging symbols:
16649 0x6100114c cygwin1!__assert
16650 0x61004034 cygwin1!_dll_crt0@@0
16651 0x61004240 cygwin1!dll_crt0(per_process *)
16655 @subsubsection Working with Minimal Symbols
16657 Symbols extracted from a DLL's export table do not contain very much
16658 type information. All that @value{GDBN} can do is guess whether a symbol
16659 refers to a function or variable depending on the linker section that
16660 contains the symbol. Also note that the actual contents of the memory
16661 contained in a DLL are not available unless the program is running. This
16662 means that you cannot examine the contents of a variable or disassemble
16663 a function within a DLL without a running program.
16665 Variables are generally treated as pointers and dereferenced
16666 automatically. For this reason, it is often necessary to prefix a
16667 variable name with the address-of operator (``&'') and provide explicit
16668 type information in the command. Here's an example of the type of
16672 (@value{GDBP}) print 'cygwin1!__argv'
16677 (@value{GDBP}) x 'cygwin1!__argv'
16678 0x10021610: "\230y\""
16681 And two possible solutions:
16684 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16685 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16689 (@value{GDBP}) x/2x &'cygwin1!__argv'
16690 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16691 (@value{GDBP}) x/x 0x10021608
16692 0x10021608: 0x0022fd98
16693 (@value{GDBP}) x/s 0x0022fd98
16694 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16697 Setting a break point within a DLL is possible even before the program
16698 starts execution. However, under these circumstances, @value{GDBN} can't
16699 examine the initial instructions of the function in order to skip the
16700 function's frame set-up code. You can work around this by using ``*&''
16701 to set the breakpoint at a raw memory address:
16704 (@value{GDBP}) break *&'python22!PyOS_Readline'
16705 Breakpoint 1 at 0x1e04eff0
16708 The author of these extensions is not entirely convinced that setting a
16709 break point within a shared DLL like @file{kernel32.dll} is completely
16713 @subsection Commands Specific to @sc{gnu} Hurd Systems
16714 @cindex @sc{gnu} Hurd debugging
16716 This subsection describes @value{GDBN} commands specific to the
16717 @sc{gnu} Hurd native debugging.
16722 @kindex set signals@r{, Hurd command}
16723 @kindex set sigs@r{, Hurd command}
16724 This command toggles the state of inferior signal interception by
16725 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16726 affected by this command. @code{sigs} is a shorthand alias for
16731 @kindex show signals@r{, Hurd command}
16732 @kindex show sigs@r{, Hurd command}
16733 Show the current state of intercepting inferior's signals.
16735 @item set signal-thread
16736 @itemx set sigthread
16737 @kindex set signal-thread
16738 @kindex set sigthread
16739 This command tells @value{GDBN} which thread is the @code{libc} signal
16740 thread. That thread is run when a signal is delivered to a running
16741 process. @code{set sigthread} is the shorthand alias of @code{set
16744 @item show signal-thread
16745 @itemx show sigthread
16746 @kindex show signal-thread
16747 @kindex show sigthread
16748 These two commands show which thread will run when the inferior is
16749 delivered a signal.
16752 @kindex set stopped@r{, Hurd command}
16753 This commands tells @value{GDBN} that the inferior process is stopped,
16754 as with the @code{SIGSTOP} signal. The stopped process can be
16755 continued by delivering a signal to it.
16758 @kindex show stopped@r{, Hurd command}
16759 This command shows whether @value{GDBN} thinks the debuggee is
16762 @item set exceptions
16763 @kindex set exceptions@r{, Hurd command}
16764 Use this command to turn off trapping of exceptions in the inferior.
16765 When exception trapping is off, neither breakpoints nor
16766 single-stepping will work. To restore the default, set exception
16769 @item show exceptions
16770 @kindex show exceptions@r{, Hurd command}
16771 Show the current state of trapping exceptions in the inferior.
16773 @item set task pause
16774 @kindex set task@r{, Hurd commands}
16775 @cindex task attributes (@sc{gnu} Hurd)
16776 @cindex pause current task (@sc{gnu} Hurd)
16777 This command toggles task suspension when @value{GDBN} has control.
16778 Setting it to on takes effect immediately, and the task is suspended
16779 whenever @value{GDBN} gets control. Setting it to off will take
16780 effect the next time the inferior is continued. If this option is set
16781 to off, you can use @code{set thread default pause on} or @code{set
16782 thread pause on} (see below) to pause individual threads.
16784 @item show task pause
16785 @kindex show task@r{, Hurd commands}
16786 Show the current state of task suspension.
16788 @item set task detach-suspend-count
16789 @cindex task suspend count
16790 @cindex detach from task, @sc{gnu} Hurd
16791 This command sets the suspend count the task will be left with when
16792 @value{GDBN} detaches from it.
16794 @item show task detach-suspend-count
16795 Show the suspend count the task will be left with when detaching.
16797 @item set task exception-port
16798 @itemx set task excp
16799 @cindex task exception port, @sc{gnu} Hurd
16800 This command sets the task exception port to which @value{GDBN} will
16801 forward exceptions. The argument should be the value of the @dfn{send
16802 rights} of the task. @code{set task excp} is a shorthand alias.
16804 @item set noninvasive
16805 @cindex noninvasive task options
16806 This command switches @value{GDBN} to a mode that is the least
16807 invasive as far as interfering with the inferior is concerned. This
16808 is the same as using @code{set task pause}, @code{set exceptions}, and
16809 @code{set signals} to values opposite to the defaults.
16811 @item info send-rights
16812 @itemx info receive-rights
16813 @itemx info port-rights
16814 @itemx info port-sets
16815 @itemx info dead-names
16818 @cindex send rights, @sc{gnu} Hurd
16819 @cindex receive rights, @sc{gnu} Hurd
16820 @cindex port rights, @sc{gnu} Hurd
16821 @cindex port sets, @sc{gnu} Hurd
16822 @cindex dead names, @sc{gnu} Hurd
16823 These commands display information about, respectively, send rights,
16824 receive rights, port rights, port sets, and dead names of a task.
16825 There are also shorthand aliases: @code{info ports} for @code{info
16826 port-rights} and @code{info psets} for @code{info port-sets}.
16828 @item set thread pause
16829 @kindex set thread@r{, Hurd command}
16830 @cindex thread properties, @sc{gnu} Hurd
16831 @cindex pause current thread (@sc{gnu} Hurd)
16832 This command toggles current thread suspension when @value{GDBN} has
16833 control. Setting it to on takes effect immediately, and the current
16834 thread is suspended whenever @value{GDBN} gets control. Setting it to
16835 off will take effect the next time the inferior is continued.
16836 Normally, this command has no effect, since when @value{GDBN} has
16837 control, the whole task is suspended. However, if you used @code{set
16838 task pause off} (see above), this command comes in handy to suspend
16839 only the current thread.
16841 @item show thread pause
16842 @kindex show thread@r{, Hurd command}
16843 This command shows the state of current thread suspension.
16845 @item set thread run
16846 This command sets whether the current thread is allowed to run.
16848 @item show thread run
16849 Show whether the current thread is allowed to run.
16851 @item set thread detach-suspend-count
16852 @cindex thread suspend count, @sc{gnu} Hurd
16853 @cindex detach from thread, @sc{gnu} Hurd
16854 This command sets the suspend count @value{GDBN} will leave on a
16855 thread when detaching. This number is relative to the suspend count
16856 found by @value{GDBN} when it notices the thread; use @code{set thread
16857 takeover-suspend-count} to force it to an absolute value.
16859 @item show thread detach-suspend-count
16860 Show the suspend count @value{GDBN} will leave on the thread when
16863 @item set thread exception-port
16864 @itemx set thread excp
16865 Set the thread exception port to which to forward exceptions. This
16866 overrides the port set by @code{set task exception-port} (see above).
16867 @code{set thread excp} is the shorthand alias.
16869 @item set thread takeover-suspend-count
16870 Normally, @value{GDBN}'s thread suspend counts are relative to the
16871 value @value{GDBN} finds when it notices each thread. This command
16872 changes the suspend counts to be absolute instead.
16874 @item set thread default
16875 @itemx show thread default
16876 @cindex thread default settings, @sc{gnu} Hurd
16877 Each of the above @code{set thread} commands has a @code{set thread
16878 default} counterpart (e.g., @code{set thread default pause}, @code{set
16879 thread default exception-port}, etc.). The @code{thread default}
16880 variety of commands sets the default thread properties for all
16881 threads; you can then change the properties of individual threads with
16882 the non-default commands.
16887 @subsection QNX Neutrino
16888 @cindex QNX Neutrino
16890 @value{GDBN} provides the following commands specific to the QNX
16894 @item set debug nto-debug
16895 @kindex set debug nto-debug
16896 When set to on, enables debugging messages specific to the QNX
16899 @item show debug nto-debug
16900 @kindex show debug nto-debug
16901 Show the current state of QNX Neutrino messages.
16908 @value{GDBN} provides the following commands specific to the Darwin target:
16911 @item set debug darwin @var{num}
16912 @kindex set debug darwin
16913 When set to a non zero value, enables debugging messages specific to
16914 the Darwin support. Higher values produce more verbose output.
16916 @item show debug darwin
16917 @kindex show debug darwin
16918 Show the current state of Darwin messages.
16920 @item set debug mach-o @var{num}
16921 @kindex set debug mach-o
16922 When set to a non zero value, enables debugging messages while
16923 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16924 file format used on Darwin for object and executable files.) Higher
16925 values produce more verbose output. This is a command to diagnose
16926 problems internal to @value{GDBN} and should not be needed in normal
16929 @item show debug mach-o
16930 @kindex show debug mach-o
16931 Show the current state of Mach-O file messages.
16933 @item set mach-exceptions on
16934 @itemx set mach-exceptions off
16935 @kindex set mach-exceptions
16936 On Darwin, faults are first reported as a Mach exception and are then
16937 mapped to a Posix signal. Use this command to turn on trapping of
16938 Mach exceptions in the inferior. This might be sometimes useful to
16939 better understand the cause of a fault. The default is off.
16941 @item show mach-exceptions
16942 @kindex show mach-exceptions
16943 Show the current state of exceptions trapping.
16948 @section Embedded Operating Systems
16950 This section describes configurations involving the debugging of
16951 embedded operating systems that are available for several different
16955 * VxWorks:: Using @value{GDBN} with VxWorks
16958 @value{GDBN} includes the ability to debug programs running on
16959 various real-time operating systems.
16962 @subsection Using @value{GDBN} with VxWorks
16968 @kindex target vxworks
16969 @item target vxworks @var{machinename}
16970 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16971 is the target system's machine name or IP address.
16975 On VxWorks, @code{load} links @var{filename} dynamically on the
16976 current target system as well as adding its symbols in @value{GDBN}.
16978 @value{GDBN} enables developers to spawn and debug tasks running on networked
16979 VxWorks targets from a Unix host. Already-running tasks spawned from
16980 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16981 both the Unix host and on the VxWorks target. The program
16982 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16983 installed with the name @code{vxgdb}, to distinguish it from a
16984 @value{GDBN} for debugging programs on the host itself.)
16987 @item VxWorks-timeout @var{args}
16988 @kindex vxworks-timeout
16989 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16990 This option is set by the user, and @var{args} represents the number of
16991 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16992 your VxWorks target is a slow software simulator or is on the far side
16993 of a thin network line.
16996 The following information on connecting to VxWorks was current when
16997 this manual was produced; newer releases of VxWorks may use revised
17000 @findex INCLUDE_RDB
17001 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17002 to include the remote debugging interface routines in the VxWorks
17003 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17004 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17005 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17006 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17007 information on configuring and remaking VxWorks, see the manufacturer's
17009 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17011 Once you have included @file{rdb.a} in your VxWorks system image and set
17012 your Unix execution search path to find @value{GDBN}, you are ready to
17013 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17014 @code{vxgdb}, depending on your installation).
17016 @value{GDBN} comes up showing the prompt:
17023 * VxWorks Connection:: Connecting to VxWorks
17024 * VxWorks Download:: VxWorks download
17025 * VxWorks Attach:: Running tasks
17028 @node VxWorks Connection
17029 @subsubsection Connecting to VxWorks
17031 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17032 network. To connect to a target whose host name is ``@code{tt}'', type:
17035 (vxgdb) target vxworks tt
17039 @value{GDBN} displays messages like these:
17042 Attaching remote machine across net...
17047 @value{GDBN} then attempts to read the symbol tables of any object modules
17048 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17049 these files by searching the directories listed in the command search
17050 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17051 to find an object file, it displays a message such as:
17054 prog.o: No such file or directory.
17057 When this happens, add the appropriate directory to the search path with
17058 the @value{GDBN} command @code{path}, and execute the @code{target}
17061 @node VxWorks Download
17062 @subsubsection VxWorks Download
17064 @cindex download to VxWorks
17065 If you have connected to the VxWorks target and you want to debug an
17066 object that has not yet been loaded, you can use the @value{GDBN}
17067 @code{load} command to download a file from Unix to VxWorks
17068 incrementally. The object file given as an argument to the @code{load}
17069 command is actually opened twice: first by the VxWorks target in order
17070 to download the code, then by @value{GDBN} in order to read the symbol
17071 table. This can lead to problems if the current working directories on
17072 the two systems differ. If both systems have NFS mounted the same
17073 filesystems, you can avoid these problems by using absolute paths.
17074 Otherwise, it is simplest to set the working directory on both systems
17075 to the directory in which the object file resides, and then to reference
17076 the file by its name, without any path. For instance, a program
17077 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17078 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17079 program, type this on VxWorks:
17082 -> cd "@var{vxpath}/vw/demo/rdb"
17086 Then, in @value{GDBN}, type:
17089 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17090 (vxgdb) load prog.o
17093 @value{GDBN} displays a response similar to this:
17096 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17099 You can also use the @code{load} command to reload an object module
17100 after editing and recompiling the corresponding source file. Note that
17101 this makes @value{GDBN} delete all currently-defined breakpoints,
17102 auto-displays, and convenience variables, and to clear the value
17103 history. (This is necessary in order to preserve the integrity of
17104 debugger's data structures that reference the target system's symbol
17107 @node VxWorks Attach
17108 @subsubsection Running Tasks
17110 @cindex running VxWorks tasks
17111 You can also attach to an existing task using the @code{attach} command as
17115 (vxgdb) attach @var{task}
17119 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17120 or suspended when you attach to it. Running tasks are suspended at
17121 the time of attachment.
17123 @node Embedded Processors
17124 @section Embedded Processors
17126 This section goes into details specific to particular embedded
17129 @cindex send command to simulator
17130 Whenever a specific embedded processor has a simulator, @value{GDBN}
17131 allows to send an arbitrary command to the simulator.
17134 @item sim @var{command}
17135 @kindex sim@r{, a command}
17136 Send an arbitrary @var{command} string to the simulator. Consult the
17137 documentation for the specific simulator in use for information about
17138 acceptable commands.
17144 * M32R/D:: Renesas M32R/D
17145 * M68K:: Motorola M68K
17146 * MicroBlaze:: Xilinx MicroBlaze
17147 * MIPS Embedded:: MIPS Embedded
17148 * OpenRISC 1000:: OpenRisc 1000
17149 * PA:: HP PA Embedded
17150 * PowerPC Embedded:: PowerPC Embedded
17151 * Sparclet:: Tsqware Sparclet
17152 * Sparclite:: Fujitsu Sparclite
17153 * Z8000:: Zilog Z8000
17156 * Super-H:: Renesas Super-H
17165 @item target rdi @var{dev}
17166 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17167 use this target to communicate with both boards running the Angel
17168 monitor, or with the EmbeddedICE JTAG debug device.
17171 @item target rdp @var{dev}
17176 @value{GDBN} provides the following ARM-specific commands:
17179 @item set arm disassembler
17181 This commands selects from a list of disassembly styles. The
17182 @code{"std"} style is the standard style.
17184 @item show arm disassembler
17186 Show the current disassembly style.
17188 @item set arm apcs32
17189 @cindex ARM 32-bit mode
17190 This command toggles ARM operation mode between 32-bit and 26-bit.
17192 @item show arm apcs32
17193 Display the current usage of the ARM 32-bit mode.
17195 @item set arm fpu @var{fputype}
17196 This command sets the ARM floating-point unit (FPU) type. The
17197 argument @var{fputype} can be one of these:
17201 Determine the FPU type by querying the OS ABI.
17203 Software FPU, with mixed-endian doubles on little-endian ARM
17206 GCC-compiled FPA co-processor.
17208 Software FPU with pure-endian doubles.
17214 Show the current type of the FPU.
17217 This command forces @value{GDBN} to use the specified ABI.
17220 Show the currently used ABI.
17222 @item set arm fallback-mode (arm|thumb|auto)
17223 @value{GDBN} uses the symbol table, when available, to determine
17224 whether instructions are ARM or Thumb. This command controls
17225 @value{GDBN}'s default behavior when the symbol table is not
17226 available. The default is @samp{auto}, which causes @value{GDBN} to
17227 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17230 @item show arm fallback-mode
17231 Show the current fallback instruction mode.
17233 @item set arm force-mode (arm|thumb|auto)
17234 This command overrides use of the symbol table to determine whether
17235 instructions are ARM or Thumb. The default is @samp{auto}, which
17236 causes @value{GDBN} to use the symbol table and then the setting
17237 of @samp{set arm fallback-mode}.
17239 @item show arm force-mode
17240 Show the current forced instruction mode.
17242 @item set debug arm
17243 Toggle whether to display ARM-specific debugging messages from the ARM
17244 target support subsystem.
17246 @item show debug arm
17247 Show whether ARM-specific debugging messages are enabled.
17250 The following commands are available when an ARM target is debugged
17251 using the RDI interface:
17254 @item rdilogfile @r{[}@var{file}@r{]}
17256 @cindex ADP (Angel Debugger Protocol) logging
17257 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17258 With an argument, sets the log file to the specified @var{file}. With
17259 no argument, show the current log file name. The default log file is
17262 @item rdilogenable @r{[}@var{arg}@r{]}
17263 @kindex rdilogenable
17264 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17265 enables logging, with an argument 0 or @code{"no"} disables it. With
17266 no arguments displays the current setting. When logging is enabled,
17267 ADP packets exchanged between @value{GDBN} and the RDI target device
17268 are logged to a file.
17270 @item set rdiromatzero
17271 @kindex set rdiromatzero
17272 @cindex ROM at zero address, RDI
17273 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17274 vector catching is disabled, so that zero address can be used. If off
17275 (the default), vector catching is enabled. For this command to take
17276 effect, it needs to be invoked prior to the @code{target rdi} command.
17278 @item show rdiromatzero
17279 @kindex show rdiromatzero
17280 Show the current setting of ROM at zero address.
17282 @item set rdiheartbeat
17283 @kindex set rdiheartbeat
17284 @cindex RDI heartbeat
17285 Enable or disable RDI heartbeat packets. It is not recommended to
17286 turn on this option, since it confuses ARM and EPI JTAG interface, as
17287 well as the Angel monitor.
17289 @item show rdiheartbeat
17290 @kindex show rdiheartbeat
17291 Show the setting of RDI heartbeat packets.
17296 @subsection Renesas M32R/D and M32R/SDI
17299 @kindex target m32r
17300 @item target m32r @var{dev}
17301 Renesas M32R/D ROM monitor.
17303 @kindex target m32rsdi
17304 @item target m32rsdi @var{dev}
17305 Renesas M32R SDI server, connected via parallel port to the board.
17308 The following @value{GDBN} commands are specific to the M32R monitor:
17311 @item set download-path @var{path}
17312 @kindex set download-path
17313 @cindex find downloadable @sc{srec} files (M32R)
17314 Set the default path for finding downloadable @sc{srec} files.
17316 @item show download-path
17317 @kindex show download-path
17318 Show the default path for downloadable @sc{srec} files.
17320 @item set board-address @var{addr}
17321 @kindex set board-address
17322 @cindex M32-EVA target board address
17323 Set the IP address for the M32R-EVA target board.
17325 @item show board-address
17326 @kindex show board-address
17327 Show the current IP address of the target board.
17329 @item set server-address @var{addr}
17330 @kindex set server-address
17331 @cindex download server address (M32R)
17332 Set the IP address for the download server, which is the @value{GDBN}'s
17335 @item show server-address
17336 @kindex show server-address
17337 Display the IP address of the download server.
17339 @item upload @r{[}@var{file}@r{]}
17340 @kindex upload@r{, M32R}
17341 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17342 upload capability. If no @var{file} argument is given, the current
17343 executable file is uploaded.
17345 @item tload @r{[}@var{file}@r{]}
17346 @kindex tload@r{, M32R}
17347 Test the @code{upload} command.
17350 The following commands are available for M32R/SDI:
17355 @cindex reset SDI connection, M32R
17356 This command resets the SDI connection.
17360 This command shows the SDI connection status.
17363 @kindex debug_chaos
17364 @cindex M32R/Chaos debugging
17365 Instructs the remote that M32R/Chaos debugging is to be used.
17367 @item use_debug_dma
17368 @kindex use_debug_dma
17369 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17372 @kindex use_mon_code
17373 Instructs the remote to use the MON_CODE method of accessing memory.
17376 @kindex use_ib_break
17377 Instructs the remote to set breakpoints by IB break.
17379 @item use_dbt_break
17380 @kindex use_dbt_break
17381 Instructs the remote to set breakpoints by DBT.
17387 The Motorola m68k configuration includes ColdFire support, and a
17388 target command for the following ROM monitor.
17392 @kindex target dbug
17393 @item target dbug @var{dev}
17394 dBUG ROM monitor for Motorola ColdFire.
17399 @subsection MicroBlaze
17400 @cindex Xilinx MicroBlaze
17401 @cindex XMD, Xilinx Microprocessor Debugger
17403 The MicroBlaze is a soft-core processor supported on various Xilinx
17404 FPGAs, such as Spartan or Virtex series. Boards with these processors
17405 usually have JTAG ports which connect to a host system running the Xilinx
17406 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17407 This host system is used to download the configuration bitstream to
17408 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17409 communicates with the target board using the JTAG interface and
17410 presents a @code{gdbserver} interface to the board. By default
17411 @code{xmd} uses port @code{1234}. (While it is possible to change
17412 this default port, it requires the use of undocumented @code{xmd}
17413 commands. Contact Xilinx support if you need to do this.)
17415 Use these GDB commands to connect to the MicroBlaze target processor.
17418 @item target remote :1234
17419 Use this command to connect to the target if you are running @value{GDBN}
17420 on the same system as @code{xmd}.
17422 @item target remote @var{xmd-host}:1234
17423 Use this command to connect to the target if it is connected to @code{xmd}
17424 running on a different system named @var{xmd-host}.
17427 Use this command to download a program to the MicroBlaze target.
17429 @item set debug microblaze @var{n}
17430 Enable MicroBlaze-specific debugging messages if non-zero.
17432 @item show debug microblaze @var{n}
17433 Show MicroBlaze-specific debugging level.
17436 @node MIPS Embedded
17437 @subsection MIPS Embedded
17439 @cindex MIPS boards
17440 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17441 MIPS board attached to a serial line. This is available when
17442 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17445 Use these @value{GDBN} commands to specify the connection to your target board:
17448 @item target mips @var{port}
17449 @kindex target mips @var{port}
17450 To run a program on the board, start up @code{@value{GDBP}} with the
17451 name of your program as the argument. To connect to the board, use the
17452 command @samp{target mips @var{port}}, where @var{port} is the name of
17453 the serial port connected to the board. If the program has not already
17454 been downloaded to the board, you may use the @code{load} command to
17455 download it. You can then use all the usual @value{GDBN} commands.
17457 For example, this sequence connects to the target board through a serial
17458 port, and loads and runs a program called @var{prog} through the
17462 host$ @value{GDBP} @var{prog}
17463 @value{GDBN} is free software and @dots{}
17464 (@value{GDBP}) target mips /dev/ttyb
17465 (@value{GDBP}) load @var{prog}
17469 @item target mips @var{hostname}:@var{portnumber}
17470 On some @value{GDBN} host configurations, you can specify a TCP
17471 connection (for instance, to a serial line managed by a terminal
17472 concentrator) instead of a serial port, using the syntax
17473 @samp{@var{hostname}:@var{portnumber}}.
17475 @item target pmon @var{port}
17476 @kindex target pmon @var{port}
17479 @item target ddb @var{port}
17480 @kindex target ddb @var{port}
17481 NEC's DDB variant of PMON for Vr4300.
17483 @item target lsi @var{port}
17484 @kindex target lsi @var{port}
17485 LSI variant of PMON.
17487 @kindex target r3900
17488 @item target r3900 @var{dev}
17489 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17491 @kindex target array
17492 @item target array @var{dev}
17493 Array Tech LSI33K RAID controller board.
17499 @value{GDBN} also supports these special commands for MIPS targets:
17502 @item set mipsfpu double
17503 @itemx set mipsfpu single
17504 @itemx set mipsfpu none
17505 @itemx set mipsfpu auto
17506 @itemx show mipsfpu
17507 @kindex set mipsfpu
17508 @kindex show mipsfpu
17509 @cindex MIPS remote floating point
17510 @cindex floating point, MIPS remote
17511 If your target board does not support the MIPS floating point
17512 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17513 need this, you may wish to put the command in your @value{GDBN} init
17514 file). This tells @value{GDBN} how to find the return value of
17515 functions which return floating point values. It also allows
17516 @value{GDBN} to avoid saving the floating point registers when calling
17517 functions on the board. If you are using a floating point coprocessor
17518 with only single precision floating point support, as on the @sc{r4650}
17519 processor, use the command @samp{set mipsfpu single}. The default
17520 double precision floating point coprocessor may be selected using
17521 @samp{set mipsfpu double}.
17523 In previous versions the only choices were double precision or no
17524 floating point, so @samp{set mipsfpu on} will select double precision
17525 and @samp{set mipsfpu off} will select no floating point.
17527 As usual, you can inquire about the @code{mipsfpu} variable with
17528 @samp{show mipsfpu}.
17530 @item set timeout @var{seconds}
17531 @itemx set retransmit-timeout @var{seconds}
17532 @itemx show timeout
17533 @itemx show retransmit-timeout
17534 @cindex @code{timeout}, MIPS protocol
17535 @cindex @code{retransmit-timeout}, MIPS protocol
17536 @kindex set timeout
17537 @kindex show timeout
17538 @kindex set retransmit-timeout
17539 @kindex show retransmit-timeout
17540 You can control the timeout used while waiting for a packet, in the MIPS
17541 remote protocol, with the @code{set timeout @var{seconds}} command. The
17542 default is 5 seconds. Similarly, you can control the timeout used while
17543 waiting for an acknowledgment of a packet with the @code{set
17544 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17545 You can inspect both values with @code{show timeout} and @code{show
17546 retransmit-timeout}. (These commands are @emph{only} available when
17547 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17549 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17550 is waiting for your program to stop. In that case, @value{GDBN} waits
17551 forever because it has no way of knowing how long the program is going
17552 to run before stopping.
17554 @item set syn-garbage-limit @var{num}
17555 @kindex set syn-garbage-limit@r{, MIPS remote}
17556 @cindex synchronize with remote MIPS target
17557 Limit the maximum number of characters @value{GDBN} should ignore when
17558 it tries to synchronize with the remote target. The default is 10
17559 characters. Setting the limit to -1 means there's no limit.
17561 @item show syn-garbage-limit
17562 @kindex show syn-garbage-limit@r{, MIPS remote}
17563 Show the current limit on the number of characters to ignore when
17564 trying to synchronize with the remote system.
17566 @item set monitor-prompt @var{prompt}
17567 @kindex set monitor-prompt@r{, MIPS remote}
17568 @cindex remote monitor prompt
17569 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17570 remote monitor. The default depends on the target:
17580 @item show monitor-prompt
17581 @kindex show monitor-prompt@r{, MIPS remote}
17582 Show the current strings @value{GDBN} expects as the prompt from the
17585 @item set monitor-warnings
17586 @kindex set monitor-warnings@r{, MIPS remote}
17587 Enable or disable monitor warnings about hardware breakpoints. This
17588 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17589 display warning messages whose codes are returned by the @code{lsi}
17590 PMON monitor for breakpoint commands.
17592 @item show monitor-warnings
17593 @kindex show monitor-warnings@r{, MIPS remote}
17594 Show the current setting of printing monitor warnings.
17596 @item pmon @var{command}
17597 @kindex pmon@r{, MIPS remote}
17598 @cindex send PMON command
17599 This command allows sending an arbitrary @var{command} string to the
17600 monitor. The monitor must be in debug mode for this to work.
17603 @node OpenRISC 1000
17604 @subsection OpenRISC 1000
17605 @cindex OpenRISC 1000
17607 @cindex or1k boards
17608 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17609 about platform and commands.
17613 @kindex target jtag
17614 @item target jtag jtag://@var{host}:@var{port}
17616 Connects to remote JTAG server.
17617 JTAG remote server can be either an or1ksim or JTAG server,
17618 connected via parallel port to the board.
17620 Example: @code{target jtag jtag://localhost:9999}
17623 @item or1ksim @var{command}
17624 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17625 Simulator, proprietary commands can be executed.
17627 @kindex info or1k spr
17628 @item info or1k spr
17629 Displays spr groups.
17631 @item info or1k spr @var{group}
17632 @itemx info or1k spr @var{groupno}
17633 Displays register names in selected group.
17635 @item info or1k spr @var{group} @var{register}
17636 @itemx info or1k spr @var{register}
17637 @itemx info or1k spr @var{groupno} @var{registerno}
17638 @itemx info or1k spr @var{registerno}
17639 Shows information about specified spr register.
17642 @item spr @var{group} @var{register} @var{value}
17643 @itemx spr @var{register @var{value}}
17644 @itemx spr @var{groupno} @var{registerno @var{value}}
17645 @itemx spr @var{registerno @var{value}}
17646 Writes @var{value} to specified spr register.
17649 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17650 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17651 program execution and is thus much faster. Hardware breakpoints/watchpoint
17652 triggers can be set using:
17655 Load effective address/data
17657 Store effective address/data
17659 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17664 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17665 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17667 @code{htrace} commands:
17668 @cindex OpenRISC 1000 htrace
17671 @item hwatch @var{conditional}
17672 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17673 or Data. For example:
17675 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17677 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17681 Display information about current HW trace configuration.
17683 @item htrace trigger @var{conditional}
17684 Set starting criteria for HW trace.
17686 @item htrace qualifier @var{conditional}
17687 Set acquisition qualifier for HW trace.
17689 @item htrace stop @var{conditional}
17690 Set HW trace stopping criteria.
17692 @item htrace record [@var{data}]*
17693 Selects the data to be recorded, when qualifier is met and HW trace was
17696 @item htrace enable
17697 @itemx htrace disable
17698 Enables/disables the HW trace.
17700 @item htrace rewind [@var{filename}]
17701 Clears currently recorded trace data.
17703 If filename is specified, new trace file is made and any newly collected data
17704 will be written there.
17706 @item htrace print [@var{start} [@var{len}]]
17707 Prints trace buffer, using current record configuration.
17709 @item htrace mode continuous
17710 Set continuous trace mode.
17712 @item htrace mode suspend
17713 Set suspend trace mode.
17717 @node PowerPC Embedded
17718 @subsection PowerPC Embedded
17720 @value{GDBN} provides the following PowerPC-specific commands:
17723 @kindex set powerpc
17724 @item set powerpc soft-float
17725 @itemx show powerpc soft-float
17726 Force @value{GDBN} to use (or not use) a software floating point calling
17727 convention. By default, @value{GDBN} selects the calling convention based
17728 on the selected architecture and the provided executable file.
17730 @item set powerpc vector-abi
17731 @itemx show powerpc vector-abi
17732 Force @value{GDBN} to use the specified calling convention for vector
17733 arguments and return values. The valid options are @samp{auto};
17734 @samp{generic}, to avoid vector registers even if they are present;
17735 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17736 registers. By default, @value{GDBN} selects the calling convention
17737 based on the selected architecture and the provided executable file.
17739 @kindex target dink32
17740 @item target dink32 @var{dev}
17741 DINK32 ROM monitor.
17743 @kindex target ppcbug
17744 @item target ppcbug @var{dev}
17745 @kindex target ppcbug1
17746 @item target ppcbug1 @var{dev}
17747 PPCBUG ROM monitor for PowerPC.
17750 @item target sds @var{dev}
17751 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17754 @cindex SDS protocol
17755 The following commands specific to the SDS protocol are supported
17759 @item set sdstimeout @var{nsec}
17760 @kindex set sdstimeout
17761 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17762 default is 2 seconds.
17764 @item show sdstimeout
17765 @kindex show sdstimeout
17766 Show the current value of the SDS timeout.
17768 @item sds @var{command}
17769 @kindex sds@r{, a command}
17770 Send the specified @var{command} string to the SDS monitor.
17775 @subsection HP PA Embedded
17779 @kindex target op50n
17780 @item target op50n @var{dev}
17781 OP50N monitor, running on an OKI HPPA board.
17783 @kindex target w89k
17784 @item target w89k @var{dev}
17785 W89K monitor, running on a Winbond HPPA board.
17790 @subsection Tsqware Sparclet
17794 @value{GDBN} enables developers to debug tasks running on
17795 Sparclet targets from a Unix host.
17796 @value{GDBN} uses code that runs on
17797 both the Unix host and on the Sparclet target. The program
17798 @code{@value{GDBP}} is installed and executed on the Unix host.
17801 @item remotetimeout @var{args}
17802 @kindex remotetimeout
17803 @value{GDBN} supports the option @code{remotetimeout}.
17804 This option is set by the user, and @var{args} represents the number of
17805 seconds @value{GDBN} waits for responses.
17808 @cindex compiling, on Sparclet
17809 When compiling for debugging, include the options @samp{-g} to get debug
17810 information and @samp{-Ttext} to relocate the program to where you wish to
17811 load it on the target. You may also want to add the options @samp{-n} or
17812 @samp{-N} in order to reduce the size of the sections. Example:
17815 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17818 You can use @code{objdump} to verify that the addresses are what you intended:
17821 sparclet-aout-objdump --headers --syms prog
17824 @cindex running, on Sparclet
17826 your Unix execution search path to find @value{GDBN}, you are ready to
17827 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17828 (or @code{sparclet-aout-gdb}, depending on your installation).
17830 @value{GDBN} comes up showing the prompt:
17837 * Sparclet File:: Setting the file to debug
17838 * Sparclet Connection:: Connecting to Sparclet
17839 * Sparclet Download:: Sparclet download
17840 * Sparclet Execution:: Running and debugging
17843 @node Sparclet File
17844 @subsubsection Setting File to Debug
17846 The @value{GDBN} command @code{file} lets you choose with program to debug.
17849 (gdbslet) file prog
17853 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17854 @value{GDBN} locates
17855 the file by searching the directories listed in the command search
17857 If the file was compiled with debug information (option @samp{-g}), source
17858 files will be searched as well.
17859 @value{GDBN} locates
17860 the source files by searching the directories listed in the directory search
17861 path (@pxref{Environment, ,Your Program's Environment}).
17863 to find a file, it displays a message such as:
17866 prog: No such file or directory.
17869 When this happens, add the appropriate directories to the search paths with
17870 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17871 @code{target} command again.
17873 @node Sparclet Connection
17874 @subsubsection Connecting to Sparclet
17876 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17877 To connect to a target on serial port ``@code{ttya}'', type:
17880 (gdbslet) target sparclet /dev/ttya
17881 Remote target sparclet connected to /dev/ttya
17882 main () at ../prog.c:3
17886 @value{GDBN} displays messages like these:
17892 @node Sparclet Download
17893 @subsubsection Sparclet Download
17895 @cindex download to Sparclet
17896 Once connected to the Sparclet target,
17897 you can use the @value{GDBN}
17898 @code{load} command to download the file from the host to the target.
17899 The file name and load offset should be given as arguments to the @code{load}
17901 Since the file format is aout, the program must be loaded to the starting
17902 address. You can use @code{objdump} to find out what this value is. The load
17903 offset is an offset which is added to the VMA (virtual memory address)
17904 of each of the file's sections.
17905 For instance, if the program
17906 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17907 and bss at 0x12010170, in @value{GDBN}, type:
17910 (gdbslet) load prog 0x12010000
17911 Loading section .text, size 0xdb0 vma 0x12010000
17914 If the code is loaded at a different address then what the program was linked
17915 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17916 to tell @value{GDBN} where to map the symbol table.
17918 @node Sparclet Execution
17919 @subsubsection Running and Debugging
17921 @cindex running and debugging Sparclet programs
17922 You can now begin debugging the task using @value{GDBN}'s execution control
17923 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17924 manual for the list of commands.
17928 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17930 Starting program: prog
17931 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17932 3 char *symarg = 0;
17934 4 char *execarg = "hello!";
17939 @subsection Fujitsu Sparclite
17943 @kindex target sparclite
17944 @item target sparclite @var{dev}
17945 Fujitsu sparclite boards, used only for the purpose of loading.
17946 You must use an additional command to debug the program.
17947 For example: target remote @var{dev} using @value{GDBN} standard
17953 @subsection Zilog Z8000
17956 @cindex simulator, Z8000
17957 @cindex Zilog Z8000 simulator
17959 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17962 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17963 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17964 segmented variant). The simulator recognizes which architecture is
17965 appropriate by inspecting the object code.
17968 @item target sim @var{args}
17970 @kindex target sim@r{, with Z8000}
17971 Debug programs on a simulated CPU. If the simulator supports setup
17972 options, specify them via @var{args}.
17976 After specifying this target, you can debug programs for the simulated
17977 CPU in the same style as programs for your host computer; use the
17978 @code{file} command to load a new program image, the @code{run} command
17979 to run your program, and so on.
17981 As well as making available all the usual machine registers
17982 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17983 additional items of information as specially named registers:
17988 Counts clock-ticks in the simulator.
17991 Counts instructions run in the simulator.
17994 Execution time in 60ths of a second.
17998 You can refer to these values in @value{GDBN} expressions with the usual
17999 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18000 conditional breakpoint that suspends only after at least 5000
18001 simulated clock ticks.
18004 @subsection Atmel AVR
18007 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18008 following AVR-specific commands:
18011 @item info io_registers
18012 @kindex info io_registers@r{, AVR}
18013 @cindex I/O registers (Atmel AVR)
18014 This command displays information about the AVR I/O registers. For
18015 each register, @value{GDBN} prints its number and value.
18022 When configured for debugging CRIS, @value{GDBN} provides the
18023 following CRIS-specific commands:
18026 @item set cris-version @var{ver}
18027 @cindex CRIS version
18028 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18029 The CRIS version affects register names and sizes. This command is useful in
18030 case autodetection of the CRIS version fails.
18032 @item show cris-version
18033 Show the current CRIS version.
18035 @item set cris-dwarf2-cfi
18036 @cindex DWARF-2 CFI and CRIS
18037 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18038 Change to @samp{off} when using @code{gcc-cris} whose version is below
18041 @item show cris-dwarf2-cfi
18042 Show the current state of using DWARF-2 CFI.
18044 @item set cris-mode @var{mode}
18046 Set the current CRIS mode to @var{mode}. It should only be changed when
18047 debugging in guru mode, in which case it should be set to
18048 @samp{guru} (the default is @samp{normal}).
18050 @item show cris-mode
18051 Show the current CRIS mode.
18055 @subsection Renesas Super-H
18058 For the Renesas Super-H processor, @value{GDBN} provides these
18063 @kindex regs@r{, Super-H}
18064 Show the values of all Super-H registers.
18066 @item set sh calling-convention @var{convention}
18067 @kindex set sh calling-convention
18068 Set the calling-convention used when calling functions from @value{GDBN}.
18069 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18070 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18071 convention. If the DWARF-2 information of the called function specifies
18072 that the function follows the Renesas calling convention, the function
18073 is called using the Renesas calling convention. If the calling convention
18074 is set to @samp{renesas}, the Renesas calling convention is always used,
18075 regardless of the DWARF-2 information. This can be used to override the
18076 default of @samp{gcc} if debug information is missing, or the compiler
18077 does not emit the DWARF-2 calling convention entry for a function.
18079 @item show sh calling-convention
18080 @kindex show sh calling-convention
18081 Show the current calling convention setting.
18086 @node Architectures
18087 @section Architectures
18089 This section describes characteristics of architectures that affect
18090 all uses of @value{GDBN} with the architecture, both native and cross.
18097 * HPPA:: HP PA architecture
18098 * SPU:: Cell Broadband Engine SPU architecture
18103 @subsection x86 Architecture-specific Issues
18106 @item set struct-convention @var{mode}
18107 @kindex set struct-convention
18108 @cindex struct return convention
18109 @cindex struct/union returned in registers
18110 Set the convention used by the inferior to return @code{struct}s and
18111 @code{union}s from functions to @var{mode}. Possible values of
18112 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18113 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18114 are returned on the stack, while @code{"reg"} means that a
18115 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18116 be returned in a register.
18118 @item show struct-convention
18119 @kindex show struct-convention
18120 Show the current setting of the convention to return @code{struct}s
18129 @kindex set rstack_high_address
18130 @cindex AMD 29K register stack
18131 @cindex register stack, AMD29K
18132 @item set rstack_high_address @var{address}
18133 On AMD 29000 family processors, registers are saved in a separate
18134 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18135 extent of this stack. Normally, @value{GDBN} just assumes that the
18136 stack is ``large enough''. This may result in @value{GDBN} referencing
18137 memory locations that do not exist. If necessary, you can get around
18138 this problem by specifying the ending address of the register stack with
18139 the @code{set rstack_high_address} command. The argument should be an
18140 address, which you probably want to precede with @samp{0x} to specify in
18143 @kindex show rstack_high_address
18144 @item show rstack_high_address
18145 Display the current limit of the register stack, on AMD 29000 family
18153 See the following section.
18158 @cindex stack on Alpha
18159 @cindex stack on MIPS
18160 @cindex Alpha stack
18162 Alpha- and MIPS-based computers use an unusual stack frame, which
18163 sometimes requires @value{GDBN} to search backward in the object code to
18164 find the beginning of a function.
18166 @cindex response time, MIPS debugging
18167 To improve response time (especially for embedded applications, where
18168 @value{GDBN} may be restricted to a slow serial line for this search)
18169 you may want to limit the size of this search, using one of these
18173 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18174 @item set heuristic-fence-post @var{limit}
18175 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18176 search for the beginning of a function. A value of @var{0} (the
18177 default) means there is no limit. However, except for @var{0}, the
18178 larger the limit the more bytes @code{heuristic-fence-post} must search
18179 and therefore the longer it takes to run. You should only need to use
18180 this command when debugging a stripped executable.
18182 @item show heuristic-fence-post
18183 Display the current limit.
18187 These commands are available @emph{only} when @value{GDBN} is configured
18188 for debugging programs on Alpha or MIPS processors.
18190 Several MIPS-specific commands are available when debugging MIPS
18194 @item set mips abi @var{arg}
18195 @kindex set mips abi
18196 @cindex set ABI for MIPS
18197 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18198 values of @var{arg} are:
18202 The default ABI associated with the current binary (this is the
18213 @item show mips abi
18214 @kindex show mips abi
18215 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18218 @itemx show mipsfpu
18219 @xref{MIPS Embedded, set mipsfpu}.
18221 @item set mips mask-address @var{arg}
18222 @kindex set mips mask-address
18223 @cindex MIPS addresses, masking
18224 This command determines whether the most-significant 32 bits of 64-bit
18225 MIPS addresses are masked off. The argument @var{arg} can be
18226 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18227 setting, which lets @value{GDBN} determine the correct value.
18229 @item show mips mask-address
18230 @kindex show mips mask-address
18231 Show whether the upper 32 bits of MIPS addresses are masked off or
18234 @item set remote-mips64-transfers-32bit-regs
18235 @kindex set remote-mips64-transfers-32bit-regs
18236 This command controls compatibility with 64-bit MIPS targets that
18237 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18238 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18239 and 64 bits for other registers, set this option to @samp{on}.
18241 @item show remote-mips64-transfers-32bit-regs
18242 @kindex show remote-mips64-transfers-32bit-regs
18243 Show the current setting of compatibility with older MIPS 64 targets.
18245 @item set debug mips
18246 @kindex set debug mips
18247 This command turns on and off debugging messages for the MIPS-specific
18248 target code in @value{GDBN}.
18250 @item show debug mips
18251 @kindex show debug mips
18252 Show the current setting of MIPS debugging messages.
18258 @cindex HPPA support
18260 When @value{GDBN} is debugging the HP PA architecture, it provides the
18261 following special commands:
18264 @item set debug hppa
18265 @kindex set debug hppa
18266 This command determines whether HPPA architecture-specific debugging
18267 messages are to be displayed.
18269 @item show debug hppa
18270 Show whether HPPA debugging messages are displayed.
18272 @item maint print unwind @var{address}
18273 @kindex maint print unwind@r{, HPPA}
18274 This command displays the contents of the unwind table entry at the
18275 given @var{address}.
18281 @subsection Cell Broadband Engine SPU architecture
18282 @cindex Cell Broadband Engine
18285 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18286 it provides the following special commands:
18289 @item info spu event
18291 Display SPU event facility status. Shows current event mask
18292 and pending event status.
18294 @item info spu signal
18295 Display SPU signal notification facility status. Shows pending
18296 signal-control word and signal notification mode of both signal
18297 notification channels.
18299 @item info spu mailbox
18300 Display SPU mailbox facility status. Shows all pending entries,
18301 in order of processing, in each of the SPU Write Outbound,
18302 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18305 Display MFC DMA status. Shows all pending commands in the MFC
18306 DMA queue. For each entry, opcode, tag, class IDs, effective
18307 and local store addresses and transfer size are shown.
18309 @item info spu proxydma
18310 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18311 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18312 and local store addresses and transfer size are shown.
18316 When @value{GDBN} is debugging a combined PowerPC/SPU application
18317 on the Cell Broadband Engine, it provides in addition the following
18321 @item set spu stop-on-load @var{arg}
18323 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18324 will give control to the user when a new SPE thread enters its @code{main}
18325 function. The default is @code{off}.
18327 @item show spu stop-on-load
18329 Show whether to stop for new SPE threads.
18331 @item set spu auto-flush-cache @var{arg}
18332 Set whether to automatically flush the software-managed cache. When set to
18333 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18334 cache to be flushed whenever SPE execution stops. This provides a consistent
18335 view of PowerPC memory that is accessed via the cache. If an application
18336 does not use the software-managed cache, this option has no effect.
18338 @item show spu auto-flush-cache
18339 Show whether to automatically flush the software-managed cache.
18344 @subsection PowerPC
18345 @cindex PowerPC architecture
18347 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18348 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18349 numbers stored in the floating point registers. These values must be stored
18350 in two consecutive registers, always starting at an even register like
18351 @code{f0} or @code{f2}.
18353 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18354 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18355 @code{f2} and @code{f3} for @code{$dl1} and so on.
18357 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18358 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18361 @node Controlling GDB
18362 @chapter Controlling @value{GDBN}
18364 You can alter the way @value{GDBN} interacts with you by using the
18365 @code{set} command. For commands controlling how @value{GDBN} displays
18366 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18371 * Editing:: Command editing
18372 * Command History:: Command history
18373 * Screen Size:: Screen size
18374 * Numbers:: Numbers
18375 * ABI:: Configuring the current ABI
18376 * Messages/Warnings:: Optional warnings and messages
18377 * Debugging Output:: Optional messages about internal happenings
18378 * Other Misc Settings:: Other Miscellaneous Settings
18386 @value{GDBN} indicates its readiness to read a command by printing a string
18387 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18388 can change the prompt string with the @code{set prompt} command. For
18389 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18390 the prompt in one of the @value{GDBN} sessions so that you can always tell
18391 which one you are talking to.
18393 @emph{Note:} @code{set prompt} does not add a space for you after the
18394 prompt you set. This allows you to set a prompt which ends in a space
18395 or a prompt that does not.
18399 @item set prompt @var{newprompt}
18400 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18402 @kindex show prompt
18404 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18408 @section Command Editing
18410 @cindex command line editing
18412 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18413 @sc{gnu} library provides consistent behavior for programs which provide a
18414 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18415 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18416 substitution, and a storage and recall of command history across
18417 debugging sessions.
18419 You may control the behavior of command line editing in @value{GDBN} with the
18420 command @code{set}.
18423 @kindex set editing
18426 @itemx set editing on
18427 Enable command line editing (enabled by default).
18429 @item set editing off
18430 Disable command line editing.
18432 @kindex show editing
18434 Show whether command line editing is enabled.
18437 @xref{Command Line Editing}, for more details about the Readline
18438 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18439 encouraged to read that chapter.
18441 @node Command History
18442 @section Command History
18443 @cindex command history
18445 @value{GDBN} can keep track of the commands you type during your
18446 debugging sessions, so that you can be certain of precisely what
18447 happened. Use these commands to manage the @value{GDBN} command
18450 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18451 package, to provide the history facility. @xref{Using History
18452 Interactively}, for the detailed description of the History library.
18454 To issue a command to @value{GDBN} without affecting certain aspects of
18455 the state which is seen by users, prefix it with @samp{server }
18456 (@pxref{Server Prefix}). This
18457 means that this command will not affect the command history, nor will it
18458 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18459 pressed on a line by itself.
18461 @cindex @code{server}, command prefix
18462 The server prefix does not affect the recording of values into the value
18463 history; to print a value without recording it into the value history,
18464 use the @code{output} command instead of the @code{print} command.
18466 Here is the description of @value{GDBN} commands related to command
18470 @cindex history substitution
18471 @cindex history file
18472 @kindex set history filename
18473 @cindex @env{GDBHISTFILE}, environment variable
18474 @item set history filename @var{fname}
18475 Set the name of the @value{GDBN} command history file to @var{fname}.
18476 This is the file where @value{GDBN} reads an initial command history
18477 list, and where it writes the command history from this session when it
18478 exits. You can access this list through history expansion or through
18479 the history command editing characters listed below. This file defaults
18480 to the value of the environment variable @code{GDBHISTFILE}, or to
18481 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18484 @cindex save command history
18485 @kindex set history save
18486 @item set history save
18487 @itemx set history save on
18488 Record command history in a file, whose name may be specified with the
18489 @code{set history filename} command. By default, this option is disabled.
18491 @item set history save off
18492 Stop recording command history in a file.
18494 @cindex history size
18495 @kindex set history size
18496 @cindex @env{HISTSIZE}, environment variable
18497 @item set history size @var{size}
18498 Set the number of commands which @value{GDBN} keeps in its history list.
18499 This defaults to the value of the environment variable
18500 @code{HISTSIZE}, or to 256 if this variable is not set.
18503 History expansion assigns special meaning to the character @kbd{!}.
18504 @xref{Event Designators}, for more details.
18506 @cindex history expansion, turn on/off
18507 Since @kbd{!} is also the logical not operator in C, history expansion
18508 is off by default. If you decide to enable history expansion with the
18509 @code{set history expansion on} command, you may sometimes need to
18510 follow @kbd{!} (when it is used as logical not, in an expression) with
18511 a space or a tab to prevent it from being expanded. The readline
18512 history facilities do not attempt substitution on the strings
18513 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18515 The commands to control history expansion are:
18518 @item set history expansion on
18519 @itemx set history expansion
18520 @kindex set history expansion
18521 Enable history expansion. History expansion is off by default.
18523 @item set history expansion off
18524 Disable history expansion.
18527 @kindex show history
18529 @itemx show history filename
18530 @itemx show history save
18531 @itemx show history size
18532 @itemx show history expansion
18533 These commands display the state of the @value{GDBN} history parameters.
18534 @code{show history} by itself displays all four states.
18539 @kindex show commands
18540 @cindex show last commands
18541 @cindex display command history
18542 @item show commands
18543 Display the last ten commands in the command history.
18545 @item show commands @var{n}
18546 Print ten commands centered on command number @var{n}.
18548 @item show commands +
18549 Print ten commands just after the commands last printed.
18553 @section Screen Size
18554 @cindex size of screen
18555 @cindex pauses in output
18557 Certain commands to @value{GDBN} may produce large amounts of
18558 information output to the screen. To help you read all of it,
18559 @value{GDBN} pauses and asks you for input at the end of each page of
18560 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18561 to discard the remaining output. Also, the screen width setting
18562 determines when to wrap lines of output. Depending on what is being
18563 printed, @value{GDBN} tries to break the line at a readable place,
18564 rather than simply letting it overflow onto the following line.
18566 Normally @value{GDBN} knows the size of the screen from the terminal
18567 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18568 together with the value of the @code{TERM} environment variable and the
18569 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18570 you can override it with the @code{set height} and @code{set
18577 @kindex show height
18578 @item set height @var{lpp}
18580 @itemx set width @var{cpl}
18582 These @code{set} commands specify a screen height of @var{lpp} lines and
18583 a screen width of @var{cpl} characters. The associated @code{show}
18584 commands display the current settings.
18586 If you specify a height of zero lines, @value{GDBN} does not pause during
18587 output no matter how long the output is. This is useful if output is to a
18588 file or to an editor buffer.
18590 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18591 from wrapping its output.
18593 @item set pagination on
18594 @itemx set pagination off
18595 @kindex set pagination
18596 Turn the output pagination on or off; the default is on. Turning
18597 pagination off is the alternative to @code{set height 0}. Note that
18598 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18599 Options, -batch}) also automatically disables pagination.
18601 @item show pagination
18602 @kindex show pagination
18603 Show the current pagination mode.
18608 @cindex number representation
18609 @cindex entering numbers
18611 You can always enter numbers in octal, decimal, or hexadecimal in
18612 @value{GDBN} by the usual conventions: octal numbers begin with
18613 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18614 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18615 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18616 10; likewise, the default display for numbers---when no particular
18617 format is specified---is base 10. You can change the default base for
18618 both input and output with the commands described below.
18621 @kindex set input-radix
18622 @item set input-radix @var{base}
18623 Set the default base for numeric input. Supported choices
18624 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18625 specified either unambiguously or using the current input radix; for
18629 set input-radix 012
18630 set input-radix 10.
18631 set input-radix 0xa
18635 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18636 leaves the input radix unchanged, no matter what it was, since
18637 @samp{10}, being without any leading or trailing signs of its base, is
18638 interpreted in the current radix. Thus, if the current radix is 16,
18639 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18642 @kindex set output-radix
18643 @item set output-radix @var{base}
18644 Set the default base for numeric display. Supported choices
18645 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18646 specified either unambiguously or using the current input radix.
18648 @kindex show input-radix
18649 @item show input-radix
18650 Display the current default base for numeric input.
18652 @kindex show output-radix
18653 @item show output-radix
18654 Display the current default base for numeric display.
18656 @item set radix @r{[}@var{base}@r{]}
18660 These commands set and show the default base for both input and output
18661 of numbers. @code{set radix} sets the radix of input and output to
18662 the same base; without an argument, it resets the radix back to its
18663 default value of 10.
18668 @section Configuring the Current ABI
18670 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18671 application automatically. However, sometimes you need to override its
18672 conclusions. Use these commands to manage @value{GDBN}'s view of the
18679 One @value{GDBN} configuration can debug binaries for multiple operating
18680 system targets, either via remote debugging or native emulation.
18681 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18682 but you can override its conclusion using the @code{set osabi} command.
18683 One example where this is useful is in debugging of binaries which use
18684 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18685 not have the same identifying marks that the standard C library for your
18690 Show the OS ABI currently in use.
18693 With no argument, show the list of registered available OS ABI's.
18695 @item set osabi @var{abi}
18696 Set the current OS ABI to @var{abi}.
18699 @cindex float promotion
18701 Generally, the way that an argument of type @code{float} is passed to a
18702 function depends on whether the function is prototyped. For a prototyped
18703 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18704 according to the architecture's convention for @code{float}. For unprototyped
18705 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18706 @code{double} and then passed.
18708 Unfortunately, some forms of debug information do not reliably indicate whether
18709 a function is prototyped. If @value{GDBN} calls a function that is not marked
18710 as prototyped, it consults @kbd{set coerce-float-to-double}.
18713 @kindex set coerce-float-to-double
18714 @item set coerce-float-to-double
18715 @itemx set coerce-float-to-double on
18716 Arguments of type @code{float} will be promoted to @code{double} when passed
18717 to an unprototyped function. This is the default setting.
18719 @item set coerce-float-to-double off
18720 Arguments of type @code{float} will be passed directly to unprototyped
18723 @kindex show coerce-float-to-double
18724 @item show coerce-float-to-double
18725 Show the current setting of promoting @code{float} to @code{double}.
18729 @kindex show cp-abi
18730 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18731 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18732 used to build your application. @value{GDBN} only fully supports
18733 programs with a single C@t{++} ABI; if your program contains code using
18734 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18735 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18736 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18737 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18738 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18739 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18744 Show the C@t{++} ABI currently in use.
18747 With no argument, show the list of supported C@t{++} ABI's.
18749 @item set cp-abi @var{abi}
18750 @itemx set cp-abi auto
18751 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18754 @node Messages/Warnings
18755 @section Optional Warnings and Messages
18757 @cindex verbose operation
18758 @cindex optional warnings
18759 By default, @value{GDBN} is silent about its inner workings. If you are
18760 running on a slow machine, you may want to use the @code{set verbose}
18761 command. This makes @value{GDBN} tell you when it does a lengthy
18762 internal operation, so you will not think it has crashed.
18764 Currently, the messages controlled by @code{set verbose} are those
18765 which announce that the symbol table for a source file is being read;
18766 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18769 @kindex set verbose
18770 @item set verbose on
18771 Enables @value{GDBN} output of certain informational messages.
18773 @item set verbose off
18774 Disables @value{GDBN} output of certain informational messages.
18776 @kindex show verbose
18778 Displays whether @code{set verbose} is on or off.
18781 By default, if @value{GDBN} encounters bugs in the symbol table of an
18782 object file, it is silent; but if you are debugging a compiler, you may
18783 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18788 @kindex set complaints
18789 @item set complaints @var{limit}
18790 Permits @value{GDBN} to output @var{limit} complaints about each type of
18791 unusual symbols before becoming silent about the problem. Set
18792 @var{limit} to zero to suppress all complaints; set it to a large number
18793 to prevent complaints from being suppressed.
18795 @kindex show complaints
18796 @item show complaints
18797 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18801 @anchor{confirmation requests}
18802 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18803 lot of stupid questions to confirm certain commands. For example, if
18804 you try to run a program which is already running:
18808 The program being debugged has been started already.
18809 Start it from the beginning? (y or n)
18812 If you are willing to unflinchingly face the consequences of your own
18813 commands, you can disable this ``feature'':
18817 @kindex set confirm
18819 @cindex confirmation
18820 @cindex stupid questions
18821 @item set confirm off
18822 Disables confirmation requests. Note that running @value{GDBN} with
18823 the @option{--batch} option (@pxref{Mode Options, -batch}) also
18824 automatically disables confirmation requests.
18826 @item set confirm on
18827 Enables confirmation requests (the default).
18829 @kindex show confirm
18831 Displays state of confirmation requests.
18835 @cindex command tracing
18836 If you need to debug user-defined commands or sourced files you may find it
18837 useful to enable @dfn{command tracing}. In this mode each command will be
18838 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18839 quantity denoting the call depth of each command.
18842 @kindex set trace-commands
18843 @cindex command scripts, debugging
18844 @item set trace-commands on
18845 Enable command tracing.
18846 @item set trace-commands off
18847 Disable command tracing.
18848 @item show trace-commands
18849 Display the current state of command tracing.
18852 @node Debugging Output
18853 @section Optional Messages about Internal Happenings
18854 @cindex optional debugging messages
18856 @value{GDBN} has commands that enable optional debugging messages from
18857 various @value{GDBN} subsystems; normally these commands are of
18858 interest to @value{GDBN} maintainers, or when reporting a bug. This
18859 section documents those commands.
18862 @kindex set exec-done-display
18863 @item set exec-done-display
18864 Turns on or off the notification of asynchronous commands'
18865 completion. When on, @value{GDBN} will print a message when an
18866 asynchronous command finishes its execution. The default is off.
18867 @kindex show exec-done-display
18868 @item show exec-done-display
18869 Displays the current setting of asynchronous command completion
18872 @cindex gdbarch debugging info
18873 @cindex architecture debugging info
18874 @item set debug arch
18875 Turns on or off display of gdbarch debugging info. The default is off
18877 @item show debug arch
18878 Displays the current state of displaying gdbarch debugging info.
18879 @item set debug aix-thread
18880 @cindex AIX threads
18881 Display debugging messages about inner workings of the AIX thread
18883 @item show debug aix-thread
18884 Show the current state of AIX thread debugging info display.
18885 @item set debug dwarf2-die
18886 @cindex DWARF2 DIEs
18887 Dump DWARF2 DIEs after they are read in.
18888 The value is the number of nesting levels to print.
18889 A value of zero turns off the display.
18890 @item show debug dwarf2-die
18891 Show the current state of DWARF2 DIE debugging.
18892 @item set debug displaced
18893 @cindex displaced stepping debugging info
18894 Turns on or off display of @value{GDBN} debugging info for the
18895 displaced stepping support. The default is off.
18896 @item show debug displaced
18897 Displays the current state of displaying @value{GDBN} debugging info
18898 related to displaced stepping.
18899 @item set debug event
18900 @cindex event debugging info
18901 Turns on or off display of @value{GDBN} event debugging info. The
18903 @item show debug event
18904 Displays the current state of displaying @value{GDBN} event debugging
18906 @item set debug expression
18907 @cindex expression debugging info
18908 Turns on or off display of debugging info about @value{GDBN}
18909 expression parsing. The default is off.
18910 @item show debug expression
18911 Displays the current state of displaying debugging info about
18912 @value{GDBN} expression parsing.
18913 @item set debug frame
18914 @cindex frame debugging info
18915 Turns on or off display of @value{GDBN} frame debugging info. The
18917 @item show debug frame
18918 Displays the current state of displaying @value{GDBN} frame debugging
18920 @item set debug gnu-nat
18921 @cindex @sc{gnu}/Hurd debug messages
18922 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18923 @item show debug gnu-nat
18924 Show the current state of @sc{gnu}/Hurd debugging messages.
18925 @item set debug infrun
18926 @cindex inferior debugging info
18927 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18928 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18929 for implementing operations such as single-stepping the inferior.
18930 @item show debug infrun
18931 Displays the current state of @value{GDBN} inferior debugging.
18932 @item set debug lin-lwp
18933 @cindex @sc{gnu}/Linux LWP debug messages
18934 @cindex Linux lightweight processes
18935 Turns on or off debugging messages from the Linux LWP debug support.
18936 @item show debug lin-lwp
18937 Show the current state of Linux LWP debugging messages.
18938 @item set debug lin-lwp-async
18939 @cindex @sc{gnu}/Linux LWP async debug messages
18940 @cindex Linux lightweight processes
18941 Turns on or off debugging messages from the Linux LWP async debug support.
18942 @item show debug lin-lwp-async
18943 Show the current state of Linux LWP async debugging messages.
18944 @item set debug observer
18945 @cindex observer debugging info
18946 Turns on or off display of @value{GDBN} observer debugging. This
18947 includes info such as the notification of observable events.
18948 @item show debug observer
18949 Displays the current state of observer debugging.
18950 @item set debug overload
18951 @cindex C@t{++} overload debugging info
18952 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18953 info. This includes info such as ranking of functions, etc. The default
18955 @item show debug overload
18956 Displays the current state of displaying @value{GDBN} C@t{++} overload
18958 @cindex expression parser, debugging info
18959 @cindex debug expression parser
18960 @item set debug parser
18961 Turns on or off the display of expression parser debugging output.
18962 Internally, this sets the @code{yydebug} variable in the expression
18963 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
18964 details. The default is off.
18965 @item show debug parser
18966 Show the current state of expression parser debugging.
18967 @cindex packets, reporting on stdout
18968 @cindex serial connections, debugging
18969 @cindex debug remote protocol
18970 @cindex remote protocol debugging
18971 @cindex display remote packets
18972 @item set debug remote
18973 Turns on or off display of reports on all packets sent back and forth across
18974 the serial line to the remote machine. The info is printed on the
18975 @value{GDBN} standard output stream. The default is off.
18976 @item show debug remote
18977 Displays the state of display of remote packets.
18978 @item set debug serial
18979 Turns on or off display of @value{GDBN} serial debugging info. The
18981 @item show debug serial
18982 Displays the current state of displaying @value{GDBN} serial debugging
18984 @item set debug solib-frv
18985 @cindex FR-V shared-library debugging
18986 Turns on or off debugging messages for FR-V shared-library code.
18987 @item show debug solib-frv
18988 Display the current state of FR-V shared-library code debugging
18990 @item set debug target
18991 @cindex target debugging info
18992 Turns on or off display of @value{GDBN} target debugging info. This info
18993 includes what is going on at the target level of GDB, as it happens. The
18994 default is 0. Set it to 1 to track events, and to 2 to also track the
18995 value of large memory transfers. Changes to this flag do not take effect
18996 until the next time you connect to a target or use the @code{run} command.
18997 @item show debug target
18998 Displays the current state of displaying @value{GDBN} target debugging
19000 @item set debug timestamp
19001 @cindex timestampping debugging info
19002 Turns on or off display of timestamps with @value{GDBN} debugging info.
19003 When enabled, seconds and microseconds are displayed before each debugging
19005 @item show debug timestamp
19006 Displays the current state of displaying timestamps with @value{GDBN}
19008 @item set debugvarobj
19009 @cindex variable object debugging info
19010 Turns on or off display of @value{GDBN} variable object debugging
19011 info. The default is off.
19012 @item show debugvarobj
19013 Displays the current state of displaying @value{GDBN} variable object
19015 @item set debug xml
19016 @cindex XML parser debugging
19017 Turns on or off debugging messages for built-in XML parsers.
19018 @item show debug xml
19019 Displays the current state of XML debugging messages.
19022 @node Other Misc Settings
19023 @section Other Miscellaneous Settings
19024 @cindex miscellaneous settings
19027 @kindex set interactive-mode
19028 @item set interactive-mode
19029 If @code{on}, forces @value{GDBN} to operate interactively.
19030 If @code{off}, forces @value{GDBN} to operate non-interactively,
19031 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19032 based on whether the debugger was started in a terminal or not.
19034 In the vast majority of cases, the debugger should be able to guess
19035 correctly which mode should be used. But this setting can be useful
19036 in certain specific cases, such as running a MinGW @value{GDBN}
19037 inside a cygwin window.
19039 @kindex show interactive-mode
19040 @item show interactive-mode
19041 Displays whether the debugger is operating in interactive mode or not.
19044 @node Extending GDB
19045 @chapter Extending @value{GDBN}
19046 @cindex extending GDB
19048 @value{GDBN} provides two mechanisms for extension. The first is based
19049 on composition of @value{GDBN} commands, and the second is based on the
19050 Python scripting language.
19052 To facilitate the use of these extensions, @value{GDBN} is capable
19053 of evaluating the contents of a file. When doing so, @value{GDBN}
19054 can recognize which scripting language is being used by looking at
19055 the filename extension. Files with an unrecognized filename extension
19056 are always treated as a @value{GDBN} Command Files.
19057 @xref{Command Files,, Command files}.
19059 You can control how @value{GDBN} evaluates these files with the following
19063 @kindex set script-extension
19064 @kindex show script-extension
19065 @item set script-extension off
19066 All scripts are always evaluated as @value{GDBN} Command Files.
19068 @item set script-extension soft
19069 The debugger determines the scripting language based on filename
19070 extension. If this scripting language is supported, @value{GDBN}
19071 evaluates the script using that language. Otherwise, it evaluates
19072 the file as a @value{GDBN} Command File.
19074 @item set script-extension strict
19075 The debugger determines the scripting language based on filename
19076 extension, and evaluates the script using that language. If the
19077 language is not supported, then the evaluation fails.
19079 @item show script-extension
19080 Display the current value of the @code{script-extension} option.
19085 * Sequences:: Canned Sequences of Commands
19086 * Python:: Scripting @value{GDBN} using Python
19090 @section Canned Sequences of Commands
19092 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19093 Command Lists}), @value{GDBN} provides two ways to store sequences of
19094 commands for execution as a unit: user-defined commands and command
19098 * Define:: How to define your own commands
19099 * Hooks:: Hooks for user-defined commands
19100 * Command Files:: How to write scripts of commands to be stored in a file
19101 * Output:: Commands for controlled output
19105 @subsection User-defined Commands
19107 @cindex user-defined command
19108 @cindex arguments, to user-defined commands
19109 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19110 which you assign a new name as a command. This is done with the
19111 @code{define} command. User commands may accept up to 10 arguments
19112 separated by whitespace. Arguments are accessed within the user command
19113 via @code{$arg0@dots{}$arg9}. A trivial example:
19117 print $arg0 + $arg1 + $arg2
19122 To execute the command use:
19129 This defines the command @code{adder}, which prints the sum of
19130 its three arguments. Note the arguments are text substitutions, so they may
19131 reference variables, use complex expressions, or even perform inferior
19134 @cindex argument count in user-defined commands
19135 @cindex how many arguments (user-defined commands)
19136 In addition, @code{$argc} may be used to find out how many arguments have
19137 been passed. This expands to a number in the range 0@dots{}10.
19142 print $arg0 + $arg1
19145 print $arg0 + $arg1 + $arg2
19153 @item define @var{commandname}
19154 Define a command named @var{commandname}. If there is already a command
19155 by that name, you are asked to confirm that you want to redefine it.
19156 @var{commandname} may be a bare command name consisting of letters,
19157 numbers, dashes, and underscores. It may also start with any predefined
19158 prefix command. For example, @samp{define target my-target} creates
19159 a user-defined @samp{target my-target} command.
19161 The definition of the command is made up of other @value{GDBN} command lines,
19162 which are given following the @code{define} command. The end of these
19163 commands is marked by a line containing @code{end}.
19166 @kindex end@r{ (user-defined commands)}
19167 @item document @var{commandname}
19168 Document the user-defined command @var{commandname}, so that it can be
19169 accessed by @code{help}. The command @var{commandname} must already be
19170 defined. This command reads lines of documentation just as @code{define}
19171 reads the lines of the command definition, ending with @code{end}.
19172 After the @code{document} command is finished, @code{help} on command
19173 @var{commandname} displays the documentation you have written.
19175 You may use the @code{document} command again to change the
19176 documentation of a command. Redefining the command with @code{define}
19177 does not change the documentation.
19179 @kindex dont-repeat
19180 @cindex don't repeat command
19182 Used inside a user-defined command, this tells @value{GDBN} that this
19183 command should not be repeated when the user hits @key{RET}
19184 (@pxref{Command Syntax, repeat last command}).
19186 @kindex help user-defined
19187 @item help user-defined
19188 List all user-defined commands, with the first line of the documentation
19193 @itemx show user @var{commandname}
19194 Display the @value{GDBN} commands used to define @var{commandname} (but
19195 not its documentation). If no @var{commandname} is given, display the
19196 definitions for all user-defined commands.
19198 @cindex infinite recursion in user-defined commands
19199 @kindex show max-user-call-depth
19200 @kindex set max-user-call-depth
19201 @item show max-user-call-depth
19202 @itemx set max-user-call-depth
19203 The value of @code{max-user-call-depth} controls how many recursion
19204 levels are allowed in user-defined commands before @value{GDBN} suspects an
19205 infinite recursion and aborts the command.
19208 In addition to the above commands, user-defined commands frequently
19209 use control flow commands, described in @ref{Command Files}.
19211 When user-defined commands are executed, the
19212 commands of the definition are not printed. An error in any command
19213 stops execution of the user-defined command.
19215 If used interactively, commands that would ask for confirmation proceed
19216 without asking when used inside a user-defined command. Many @value{GDBN}
19217 commands that normally print messages to say what they are doing omit the
19218 messages when used in a user-defined command.
19221 @subsection User-defined Command Hooks
19222 @cindex command hooks
19223 @cindex hooks, for commands
19224 @cindex hooks, pre-command
19227 You may define @dfn{hooks}, which are a special kind of user-defined
19228 command. Whenever you run the command @samp{foo}, if the user-defined
19229 command @samp{hook-foo} exists, it is executed (with no arguments)
19230 before that command.
19232 @cindex hooks, post-command
19234 A hook may also be defined which is run after the command you executed.
19235 Whenever you run the command @samp{foo}, if the user-defined command
19236 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19237 that command. Post-execution hooks may exist simultaneously with
19238 pre-execution hooks, for the same command.
19240 It is valid for a hook to call the command which it hooks. If this
19241 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19243 @c It would be nice if hookpost could be passed a parameter indicating
19244 @c if the command it hooks executed properly or not. FIXME!
19246 @kindex stop@r{, a pseudo-command}
19247 In addition, a pseudo-command, @samp{stop} exists. Defining
19248 (@samp{hook-stop}) makes the associated commands execute every time
19249 execution stops in your program: before breakpoint commands are run,
19250 displays are printed, or the stack frame is printed.
19252 For example, to ignore @code{SIGALRM} signals while
19253 single-stepping, but treat them normally during normal execution,
19258 handle SIGALRM nopass
19262 handle SIGALRM pass
19265 define hook-continue
19266 handle SIGALRM pass
19270 As a further example, to hook at the beginning and end of the @code{echo}
19271 command, and to add extra text to the beginning and end of the message,
19279 define hookpost-echo
19283 (@value{GDBP}) echo Hello World
19284 <<<---Hello World--->>>
19289 You can define a hook for any single-word command in @value{GDBN}, but
19290 not for command aliases; you should define a hook for the basic command
19291 name, e.g.@: @code{backtrace} rather than @code{bt}.
19292 @c FIXME! So how does Joe User discover whether a command is an alias
19294 You can hook a multi-word command by adding @code{hook-} or
19295 @code{hookpost-} to the last word of the command, e.g.@:
19296 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19298 If an error occurs during the execution of your hook, execution of
19299 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19300 (before the command that you actually typed had a chance to run).
19302 If you try to define a hook which does not match any known command, you
19303 get a warning from the @code{define} command.
19305 @node Command Files
19306 @subsection Command Files
19308 @cindex command files
19309 @cindex scripting commands
19310 A command file for @value{GDBN} is a text file made of lines that are
19311 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19312 also be included. An empty line in a command file does nothing; it
19313 does not mean to repeat the last command, as it would from the
19316 You can request the execution of a command file with the @code{source}
19317 command. Note that the @code{source} command is also used to evaluate
19318 scripts that are not Command Files. The exact behavior can be configured
19319 using the @code{script-extension} setting.
19320 @xref{Extending GDB,, Extending GDB}.
19324 @cindex execute commands from a file
19325 @item source [@code{-v}] @var{filename}
19326 Execute the command file @var{filename}.
19329 The lines in a command file are generally executed sequentially,
19330 unless the order of execution is changed by one of the
19331 @emph{flow-control commands} described below. The commands are not
19332 printed as they are executed. An error in any command terminates
19333 execution of the command file and control is returned to the console.
19335 @value{GDBN} searches for @var{filename} in the current directory and then
19336 on the search path (specified with the @samp{directory} command).
19338 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19339 each command as it is executed. The option must be given before
19340 @var{filename}, and is interpreted as part of the filename anywhere else.
19342 Commands that would ask for confirmation if used interactively proceed
19343 without asking when used in a command file. Many @value{GDBN} commands that
19344 normally print messages to say what they are doing omit the messages
19345 when called from command files.
19347 @value{GDBN} also accepts command input from standard input. In this
19348 mode, normal output goes to standard output and error output goes to
19349 standard error. Errors in a command file supplied on standard input do
19350 not terminate execution of the command file---execution continues with
19354 gdb < cmds > log 2>&1
19357 (The syntax above will vary depending on the shell used.) This example
19358 will execute commands from the file @file{cmds}. All output and errors
19359 would be directed to @file{log}.
19361 Since commands stored on command files tend to be more general than
19362 commands typed interactively, they frequently need to deal with
19363 complicated situations, such as different or unexpected values of
19364 variables and symbols, changes in how the program being debugged is
19365 built, etc. @value{GDBN} provides a set of flow-control commands to
19366 deal with these complexities. Using these commands, you can write
19367 complex scripts that loop over data structures, execute commands
19368 conditionally, etc.
19375 This command allows to include in your script conditionally executed
19376 commands. The @code{if} command takes a single argument, which is an
19377 expression to evaluate. It is followed by a series of commands that
19378 are executed only if the expression is true (its value is nonzero).
19379 There can then optionally be an @code{else} line, followed by a series
19380 of commands that are only executed if the expression was false. The
19381 end of the list is marked by a line containing @code{end}.
19385 This command allows to write loops. Its syntax is similar to
19386 @code{if}: the command takes a single argument, which is an expression
19387 to evaluate, and must be followed by the commands to execute, one per
19388 line, terminated by an @code{end}. These commands are called the
19389 @dfn{body} of the loop. The commands in the body of @code{while} are
19390 executed repeatedly as long as the expression evaluates to true.
19394 This command exits the @code{while} loop in whose body it is included.
19395 Execution of the script continues after that @code{while}s @code{end}
19398 @kindex loop_continue
19399 @item loop_continue
19400 This command skips the execution of the rest of the body of commands
19401 in the @code{while} loop in whose body it is included. Execution
19402 branches to the beginning of the @code{while} loop, where it evaluates
19403 the controlling expression.
19405 @kindex end@r{ (if/else/while commands)}
19407 Terminate the block of commands that are the body of @code{if},
19408 @code{else}, or @code{while} flow-control commands.
19413 @subsection Commands for Controlled Output
19415 During the execution of a command file or a user-defined command, normal
19416 @value{GDBN} output is suppressed; the only output that appears is what is
19417 explicitly printed by the commands in the definition. This section
19418 describes three commands useful for generating exactly the output you
19423 @item echo @var{text}
19424 @c I do not consider backslash-space a standard C escape sequence
19425 @c because it is not in ANSI.
19426 Print @var{text}. Nonprinting characters can be included in
19427 @var{text} using C escape sequences, such as @samp{\n} to print a
19428 newline. @strong{No newline is printed unless you specify one.}
19429 In addition to the standard C escape sequences, a backslash followed
19430 by a space stands for a space. This is useful for displaying a
19431 string with spaces at the beginning or the end, since leading and
19432 trailing spaces are otherwise trimmed from all arguments.
19433 To print @samp{@w{ }and foo =@w{ }}, use the command
19434 @samp{echo \@w{ }and foo = \@w{ }}.
19436 A backslash at the end of @var{text} can be used, as in C, to continue
19437 the command onto subsequent lines. For example,
19440 echo This is some text\n\
19441 which is continued\n\
19442 onto several lines.\n
19445 produces the same output as
19448 echo This is some text\n
19449 echo which is continued\n
19450 echo onto several lines.\n
19454 @item output @var{expression}
19455 Print the value of @var{expression} and nothing but that value: no
19456 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19457 value history either. @xref{Expressions, ,Expressions}, for more information
19460 @item output/@var{fmt} @var{expression}
19461 Print the value of @var{expression} in format @var{fmt}. You can use
19462 the same formats as for @code{print}. @xref{Output Formats,,Output
19463 Formats}, for more information.
19466 @item printf @var{template}, @var{expressions}@dots{}
19467 Print the values of one or more @var{expressions} under the control of
19468 the string @var{template}. To print several values, make
19469 @var{expressions} be a comma-separated list of individual expressions,
19470 which may be either numbers or pointers. Their values are printed as
19471 specified by @var{template}, exactly as a C program would do by
19472 executing the code below:
19475 printf (@var{template}, @var{expressions}@dots{});
19478 As in @code{C} @code{printf}, ordinary characters in @var{template}
19479 are printed verbatim, while @dfn{conversion specification} introduced
19480 by the @samp{%} character cause subsequent @var{expressions} to be
19481 evaluated, their values converted and formatted according to type and
19482 style information encoded in the conversion specifications, and then
19485 For example, you can print two values in hex like this:
19488 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19491 @code{printf} supports all the standard @code{C} conversion
19492 specifications, including the flags and modifiers between the @samp{%}
19493 character and the conversion letter, with the following exceptions:
19497 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19500 The modifier @samp{*} is not supported for specifying precision or
19504 The @samp{'} flag (for separation of digits into groups according to
19505 @code{LC_NUMERIC'}) is not supported.
19508 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19512 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19515 The conversion letters @samp{a} and @samp{A} are not supported.
19519 Note that the @samp{ll} type modifier is supported only if the
19520 underlying @code{C} implementation used to build @value{GDBN} supports
19521 the @code{long long int} type, and the @samp{L} type modifier is
19522 supported only if @code{long double} type is available.
19524 As in @code{C}, @code{printf} supports simple backslash-escape
19525 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19526 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19527 single character. Octal and hexadecimal escape sequences are not
19530 Additionally, @code{printf} supports conversion specifications for DFP
19531 (@dfn{Decimal Floating Point}) types using the following length modifiers
19532 together with a floating point specifier.
19537 @samp{H} for printing @code{Decimal32} types.
19540 @samp{D} for printing @code{Decimal64} types.
19543 @samp{DD} for printing @code{Decimal128} types.
19546 If the underlying @code{C} implementation used to build @value{GDBN} has
19547 support for the three length modifiers for DFP types, other modifiers
19548 such as width and precision will also be available for @value{GDBN} to use.
19550 In case there is no such @code{C} support, no additional modifiers will be
19551 available and the value will be printed in the standard way.
19553 Here's an example of printing DFP types using the above conversion letters:
19555 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19561 @section Scripting @value{GDBN} using Python
19562 @cindex python scripting
19563 @cindex scripting with python
19565 You can script @value{GDBN} using the @uref{http://www.python.org/,
19566 Python programming language}. This feature is available only if
19567 @value{GDBN} was configured using @option{--with-python}.
19570 * Python Commands:: Accessing Python from @value{GDBN}.
19571 * Python API:: Accessing @value{GDBN} from Python.
19574 @node Python Commands
19575 @subsection Python Commands
19576 @cindex python commands
19577 @cindex commands to access python
19579 @value{GDBN} provides one command for accessing the Python interpreter,
19580 and one related setting:
19584 @item python @r{[}@var{code}@r{]}
19585 The @code{python} command can be used to evaluate Python code.
19587 If given an argument, the @code{python} command will evaluate the
19588 argument as a Python command. For example:
19591 (@value{GDBP}) python print 23
19595 If you do not provide an argument to @code{python}, it will act as a
19596 multi-line command, like @code{define}. In this case, the Python
19597 script is made up of subsequent command lines, given after the
19598 @code{python} command. This command list is terminated using a line
19599 containing @code{end}. For example:
19602 (@value{GDBP}) python
19604 End with a line saying just "end".
19610 @kindex maint set python print-stack
19611 @item maint set python print-stack
19612 By default, @value{GDBN} will print a stack trace when an error occurs
19613 in a Python script. This can be controlled using @code{maint set
19614 python print-stack}: if @code{on}, the default, then Python stack
19615 printing is enabled; if @code{off}, then Python stack printing is
19619 It is also possible to execute a Python script from the @value{GDBN}
19623 @item source @file{script-name}
19624 The script name must end with @samp{.py} and @value{GDBN} must be configured
19625 to recognize the script language based on filename extension using
19626 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19628 @item python execfile ("script-name")
19629 This method is based on the @code{execfile} Python built-in function,
19630 and thus is always available.
19634 @subsection Python API
19636 @cindex programming in python
19638 @cindex python stdout
19639 @cindex python pagination
19640 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19641 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19642 A Python program which outputs to one of these streams may have its
19643 output interrupted by the user (@pxref{Screen Size}). In this
19644 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19647 * Basic Python:: Basic Python Functions.
19648 * Exception Handling::
19649 * Auto-loading:: Automatically loading Python code.
19650 * Values From Inferior::
19651 * Types In Python:: Python representation of types.
19652 * Pretty Printing:: Pretty-printing values.
19653 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19654 * Commands In Python:: Implementing new commands in Python.
19655 * Functions In Python:: Writing new convenience functions.
19656 * Objfiles In Python:: Object files.
19657 * Frames In Python:: Accessing inferior stack frames from Python.
19658 * Blocks In Python:: Accessing frame blocks from Python.
19659 * Symbols In Python:: Python representation of symbols.
19660 * Symbol Tables In Python:: Python representation of symbol tables.
19661 * Lazy Strings In Python:: Python representation of lazy strings.
19665 @subsubsection Basic Python
19667 @cindex python functions
19668 @cindex python module
19670 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19671 methods and classes added by @value{GDBN} are placed in this module.
19672 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19673 use in all scripts evaluated by the @code{python} command.
19675 @findex gdb.execute
19676 @defun execute command [from_tty]
19677 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19678 If a GDB exception happens while @var{command} runs, it is
19679 translated as described in @ref{Exception Handling,,Exception Handling}.
19680 If no exceptions occur, this function returns @code{None}.
19682 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19683 command as having originated from the user invoking it interactively.
19684 It must be a boolean value. If omitted, it defaults to @code{False}.
19687 @findex gdb.parameter
19688 @defun parameter parameter
19689 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19690 string naming the parameter to look up; @var{parameter} may contain
19691 spaces if the parameter has a multi-part name. For example,
19692 @samp{print object} is a valid parameter name.
19694 If the named parameter does not exist, this function throws a
19695 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19696 a Python value of the appropriate type, and returned.
19699 @findex gdb.history
19700 @defun history number
19701 Return a value from @value{GDBN}'s value history (@pxref{Value
19702 History}). @var{number} indicates which history element to return.
19703 If @var{number} is negative, then @value{GDBN} will take its absolute value
19704 and count backward from the last element (i.e., the most recent element) to
19705 find the value to return. If @var{number} is zero, then @value{GDBN} will
19706 return the most recent element. If the element specified by @var{number}
19707 doesn't exist in the value history, a @code{RuntimeError} exception will be
19710 If no exception is raised, the return value is always an instance of
19711 @code{gdb.Value} (@pxref{Values From Inferior}).
19714 @findex gdb.parse_and_eval
19715 @defun parse_and_eval expression
19716 Parse @var{expression} as an expression in the current language,
19717 evaluate it, and return the result as a @code{gdb.Value}.
19718 @var{expression} must be a string.
19720 This function can be useful when implementing a new command
19721 (@pxref{Commands In Python}), as it provides a way to parse the
19722 command's argument as an expression. It is also useful simply to
19723 compute values, for example, it is the only way to get the value of a
19724 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
19728 @defun write string
19729 Print a string to @value{GDBN}'s paginated standard output stream.
19730 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19731 call this function.
19736 Flush @value{GDBN}'s paginated standard output stream. Flushing
19737 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19741 @findex gdb.target_charset
19742 @defun target_charset
19743 Return the name of the current target character set (@pxref{Character
19744 Sets}). This differs from @code{gdb.parameter('target-charset')} in
19745 that @samp{auto} is never returned.
19748 @findex gdb.target_wide_charset
19749 @defun target_wide_charset
19750 Return the name of the current target wide character set
19751 (@pxref{Character Sets}). This differs from
19752 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
19756 @node Exception Handling
19757 @subsubsection Exception Handling
19758 @cindex python exceptions
19759 @cindex exceptions, python
19761 When executing the @code{python} command, Python exceptions
19762 uncaught within the Python code are translated to calls to
19763 @value{GDBN} error-reporting mechanism. If the command that called
19764 @code{python} does not handle the error, @value{GDBN} will
19765 terminate it and print an error message containing the Python
19766 exception name, the associated value, and the Python call stack
19767 backtrace at the point where the exception was raised. Example:
19770 (@value{GDBP}) python print foo
19771 Traceback (most recent call last):
19772 File "<string>", line 1, in <module>
19773 NameError: name 'foo' is not defined
19776 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19777 code are converted to Python @code{RuntimeError} exceptions. User
19778 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19779 prompt) is translated to a Python @code{KeyboardInterrupt}
19780 exception. If you catch these exceptions in your Python code, your
19781 exception handler will see @code{RuntimeError} or
19782 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19783 message as its value, and the Python call stack backtrace at the
19784 Python statement closest to where the @value{GDBN} error occured as the
19788 @subsubsection Auto-loading
19789 @cindex auto-loading, Python
19791 When a new object file is read (for example, due to the @code{file}
19792 command, or because the inferior has loaded a shared library),
19793 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19794 where @var{objfile} is the object file's real name, formed by ensuring
19795 that the file name is absolute, following all symlinks, and resolving
19796 @code{.} and @code{..} components. If this file exists and is
19797 readable, @value{GDBN} will evaluate it as a Python script.
19799 If this file does not exist, and if the parameter
19800 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19801 then @value{GDBN} will use for its each separated directory component
19802 @code{component} the file named @file{@code{component}/@var{real-name}}, where
19803 @var{real-name} is the object file's real name, as described above.
19805 Finally, if this file does not exist, then @value{GDBN} will look for
19806 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19807 @var{data-directory} is @value{GDBN}'s data directory (available via
19808 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19809 is the object file's real name, as described above.
19811 When reading an auto-loaded file, @value{GDBN} sets the ``current
19812 objfile''. This is available via the @code{gdb.current_objfile}
19813 function (@pxref{Objfiles In Python}). This can be useful for
19814 registering objfile-specific pretty-printers.
19816 The auto-loading feature is useful for supplying application-specific
19817 debugging commands and scripts. You can enable or disable this
19818 feature, and view its current state.
19821 @kindex maint set python auto-load
19822 @item maint set python auto-load [yes|no]
19823 Enable or disable the Python auto-loading feature.
19825 @kindex show python auto-load
19826 @item show python auto-load
19827 Show whether Python auto-loading is enabled or disabled.
19830 @value{GDBN} does not track which files it has already auto-loaded.
19831 So, your @samp{-gdb.py} file should take care to ensure that it may be
19832 evaluated multiple times without error.
19834 @node Values From Inferior
19835 @subsubsection Values From Inferior
19836 @cindex values from inferior, with Python
19837 @cindex python, working with values from inferior
19839 @cindex @code{gdb.Value}
19840 @value{GDBN} provides values it obtains from the inferior program in
19841 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19842 for its internal bookkeeping of the inferior's values, and for
19843 fetching values when necessary.
19845 Inferior values that are simple scalars can be used directly in
19846 Python expressions that are valid for the value's data type. Here's
19847 an example for an integer or floating-point value @code{some_val}:
19854 As result of this, @code{bar} will also be a @code{gdb.Value} object
19855 whose values are of the same type as those of @code{some_val}.
19857 Inferior values that are structures or instances of some class can
19858 be accessed using the Python @dfn{dictionary syntax}. For example, if
19859 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19860 can access its @code{foo} element with:
19863 bar = some_val['foo']
19866 Again, @code{bar} will also be a @code{gdb.Value} object.
19868 The following attributes are provided:
19871 @defivar Value address
19872 If this object is addressable, this read-only attribute holds a
19873 @code{gdb.Value} object representing the address. Otherwise,
19874 this attribute holds @code{None}.
19877 @cindex optimized out value in Python
19878 @defivar Value is_optimized_out
19879 This read-only boolean attribute is true if the compiler optimized out
19880 this value, thus it is not available for fetching from the inferior.
19883 @defivar Value type
19884 The type of this @code{gdb.Value}. The value of this attribute is a
19885 @code{gdb.Type} object.
19889 The following methods are provided:
19892 @defmethod Value cast type
19893 Return a new instance of @code{gdb.Value} that is the result of
19894 casting this instance to the type described by @var{type}, which must
19895 be a @code{gdb.Type} object. If the cast cannot be performed for some
19896 reason, this method throws an exception.
19899 @defmethod Value dereference
19900 For pointer data types, this method returns a new @code{gdb.Value} object
19901 whose contents is the object pointed to by the pointer. For example, if
19902 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19909 then you can use the corresponding @code{gdb.Value} to access what
19910 @code{foo} points to like this:
19913 bar = foo.dereference ()
19916 The result @code{bar} will be a @code{gdb.Value} object holding the
19917 value pointed to by @code{foo}.
19920 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19921 If this @code{gdb.Value} represents a string, then this method
19922 converts the contents to a Python string. Otherwise, this method will
19923 throw an exception.
19925 Strings are recognized in a language-specific way; whether a given
19926 @code{gdb.Value} represents a string is determined by the current
19929 For C-like languages, a value is a string if it is a pointer to or an
19930 array of characters or ints. The string is assumed to be terminated
19931 by a zero of the appropriate width. However if the optional length
19932 argument is given, the string will be converted to that given length,
19933 ignoring any embedded zeros that the string may contain.
19935 If the optional @var{encoding} argument is given, it must be a string
19936 naming the encoding of the string in the @code{gdb.Value}, such as
19937 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19938 the same encodings as the corresponding argument to Python's
19939 @code{string.decode} method, and the Python codec machinery will be used
19940 to convert the string. If @var{encoding} is not given, or if
19941 @var{encoding} is the empty string, then either the @code{target-charset}
19942 (@pxref{Character Sets}) will be used, or a language-specific encoding
19943 will be used, if the current language is able to supply one.
19945 The optional @var{errors} argument is the same as the corresponding
19946 argument to Python's @code{string.decode} method.
19948 If the optional @var{length} argument is given, the string will be
19949 fetched and converted to the given length.
19952 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
19953 If this @code{gdb.Value} represents a string, then this method
19954 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
19955 In Python}). Otherwise, this method will throw an exception.
19957 If the optional @var{encoding} argument is given, it must be a string
19958 naming the encoding of the @code{gdb.LazyString}. Some examples are:
19959 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
19960 @var{encoding} argument is an encoding that @value{GDBN} does
19961 recognize, @value{GDBN} will raise an error.
19963 When a lazy string is printed, the @value{GDBN} encoding machinery is
19964 used to convert the string during printing. If the optional
19965 @var{encoding} argument is not provided, or is an empty string,
19966 @value{GDBN} will automatically select the encoding most suitable for
19967 the string type. For further information on encoding in @value{GDBN}
19968 please see @ref{Character Sets}.
19970 If the optional @var{length} argument is given, the string will be
19971 fetched and encoded to the length of characters specified. If
19972 the @var{length} argument is not provided, the string will be fetched
19973 and encoded until a null of appropriate width is found.
19977 @node Types In Python
19978 @subsubsection Types In Python
19979 @cindex types in Python
19980 @cindex Python, working with types
19983 @value{GDBN} represents types from the inferior using the class
19986 The following type-related functions are available in the @code{gdb}
19989 @findex gdb.lookup_type
19990 @defun lookup_type name [block]
19991 This function looks up a type by name. @var{name} is the name of the
19992 type to look up. It must be a string.
19994 If @var{block} is given, then @var{name} is looked up in that scope.
19995 Otherwise, it is searched for globally.
19997 Ordinarily, this function will return an instance of @code{gdb.Type}.
19998 If the named type cannot be found, it will throw an exception.
20001 An instance of @code{Type} has the following attributes:
20005 The type code for this type. The type code will be one of the
20006 @code{TYPE_CODE_} constants defined below.
20009 @defivar Type sizeof
20010 The size of this type, in target @code{char} units. Usually, a
20011 target's @code{char} type will be an 8-bit byte. However, on some
20012 unusual platforms, this type may have a different size.
20016 The tag name for this type. The tag name is the name after
20017 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20018 languages have this concept. If this type has no tag name, then
20019 @code{None} is returned.
20023 The following methods are provided:
20026 @defmethod Type fields
20027 For structure and union types, this method returns the fields. Range
20028 types have two fields, the minimum and maximum values. Enum types
20029 have one field per enum constant. Function and method types have one
20030 field per parameter. The base types of C@t{++} classes are also
20031 represented as fields. If the type has no fields, or does not fit
20032 into one of these categories, an empty sequence will be returned.
20034 Each field is an object, with some pre-defined attributes:
20037 This attribute is not available for @code{static} fields (as in
20038 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20039 position of the field.
20042 The name of the field, or @code{None} for anonymous fields.
20045 This is @code{True} if the field is artificial, usually meaning that
20046 it was provided by the compiler and not the user. This attribute is
20047 always provided, and is @code{False} if the field is not artificial.
20049 @item is_base_class
20050 This is @code{True} if the field represents a base class of a C@t{++}
20051 structure. This attribute is always provided, and is @code{False}
20052 if the field is not a base class of the type that is the argument of
20053 @code{fields}, or if that type was not a C@t{++} class.
20056 If the field is packed, or is a bitfield, then this will have a
20057 non-zero value, which is the size of the field in bits. Otherwise,
20058 this will be zero; in this case the field's size is given by its type.
20061 The type of the field. This is usually an instance of @code{Type},
20062 but it can be @code{None} in some situations.
20066 @defmethod Type const
20067 Return a new @code{gdb.Type} object which represents a
20068 @code{const}-qualified variant of this type.
20071 @defmethod Type volatile
20072 Return a new @code{gdb.Type} object which represents a
20073 @code{volatile}-qualified variant of this type.
20076 @defmethod Type unqualified
20077 Return a new @code{gdb.Type} object which represents an unqualified
20078 variant of this type. That is, the result is neither @code{const} nor
20082 @defmethod Type range
20083 Return a Python @code{Tuple} object that contains two elements: the
20084 low bound of the argument type and the high bound of that type. If
20085 the type does not have a range, @value{GDBN} will raise a
20086 @code{RuntimeError} exception.
20089 @defmethod Type reference
20090 Return a new @code{gdb.Type} object which represents a reference to this
20094 @defmethod Type pointer
20095 Return a new @code{gdb.Type} object which represents a pointer to this
20099 @defmethod Type strip_typedefs
20100 Return a new @code{gdb.Type} that represents the real type,
20101 after removing all layers of typedefs.
20104 @defmethod Type target
20105 Return a new @code{gdb.Type} object which represents the target type
20108 For a pointer type, the target type is the type of the pointed-to
20109 object. For an array type (meaning C-like arrays), the target type is
20110 the type of the elements of the array. For a function or method type,
20111 the target type is the type of the return value. For a complex type,
20112 the target type is the type of the elements. For a typedef, the
20113 target type is the aliased type.
20115 If the type does not have a target, this method will throw an
20119 @defmethod Type template_argument n [block]
20120 If this @code{gdb.Type} is an instantiation of a template, this will
20121 return a new @code{gdb.Type} which represents the type of the
20122 @var{n}th template argument.
20124 If this @code{gdb.Type} is not a template type, this will throw an
20125 exception. Ordinarily, only C@t{++} code will have template types.
20127 If @var{block} is given, then @var{name} is looked up in that scope.
20128 Otherwise, it is searched for globally.
20133 Each type has a code, which indicates what category this type falls
20134 into. The available type categories are represented by constants
20135 defined in the @code{gdb} module:
20138 @findex TYPE_CODE_PTR
20139 @findex gdb.TYPE_CODE_PTR
20140 @item TYPE_CODE_PTR
20141 The type is a pointer.
20143 @findex TYPE_CODE_ARRAY
20144 @findex gdb.TYPE_CODE_ARRAY
20145 @item TYPE_CODE_ARRAY
20146 The type is an array.
20148 @findex TYPE_CODE_STRUCT
20149 @findex gdb.TYPE_CODE_STRUCT
20150 @item TYPE_CODE_STRUCT
20151 The type is a structure.
20153 @findex TYPE_CODE_UNION
20154 @findex gdb.TYPE_CODE_UNION
20155 @item TYPE_CODE_UNION
20156 The type is a union.
20158 @findex TYPE_CODE_ENUM
20159 @findex gdb.TYPE_CODE_ENUM
20160 @item TYPE_CODE_ENUM
20161 The type is an enum.
20163 @findex TYPE_CODE_FLAGS
20164 @findex gdb.TYPE_CODE_FLAGS
20165 @item TYPE_CODE_FLAGS
20166 A bit flags type, used for things such as status registers.
20168 @findex TYPE_CODE_FUNC
20169 @findex gdb.TYPE_CODE_FUNC
20170 @item TYPE_CODE_FUNC
20171 The type is a function.
20173 @findex TYPE_CODE_INT
20174 @findex gdb.TYPE_CODE_INT
20175 @item TYPE_CODE_INT
20176 The type is an integer type.
20178 @findex TYPE_CODE_FLT
20179 @findex gdb.TYPE_CODE_FLT
20180 @item TYPE_CODE_FLT
20181 A floating point type.
20183 @findex TYPE_CODE_VOID
20184 @findex gdb.TYPE_CODE_VOID
20185 @item TYPE_CODE_VOID
20186 The special type @code{void}.
20188 @findex TYPE_CODE_SET
20189 @findex gdb.TYPE_CODE_SET
20190 @item TYPE_CODE_SET
20193 @findex TYPE_CODE_RANGE
20194 @findex gdb.TYPE_CODE_RANGE
20195 @item TYPE_CODE_RANGE
20196 A range type, that is, an integer type with bounds.
20198 @findex TYPE_CODE_STRING
20199 @findex gdb.TYPE_CODE_STRING
20200 @item TYPE_CODE_STRING
20201 A string type. Note that this is only used for certain languages with
20202 language-defined string types; C strings are not represented this way.
20204 @findex TYPE_CODE_BITSTRING
20205 @findex gdb.TYPE_CODE_BITSTRING
20206 @item TYPE_CODE_BITSTRING
20209 @findex TYPE_CODE_ERROR
20210 @findex gdb.TYPE_CODE_ERROR
20211 @item TYPE_CODE_ERROR
20212 An unknown or erroneous type.
20214 @findex TYPE_CODE_METHOD
20215 @findex gdb.TYPE_CODE_METHOD
20216 @item TYPE_CODE_METHOD
20217 A method type, as found in C@t{++} or Java.
20219 @findex TYPE_CODE_METHODPTR
20220 @findex gdb.TYPE_CODE_METHODPTR
20221 @item TYPE_CODE_METHODPTR
20222 A pointer-to-member-function.
20224 @findex TYPE_CODE_MEMBERPTR
20225 @findex gdb.TYPE_CODE_MEMBERPTR
20226 @item TYPE_CODE_MEMBERPTR
20227 A pointer-to-member.
20229 @findex TYPE_CODE_REF
20230 @findex gdb.TYPE_CODE_REF
20231 @item TYPE_CODE_REF
20234 @findex TYPE_CODE_CHAR
20235 @findex gdb.TYPE_CODE_CHAR
20236 @item TYPE_CODE_CHAR
20239 @findex TYPE_CODE_BOOL
20240 @findex gdb.TYPE_CODE_BOOL
20241 @item TYPE_CODE_BOOL
20244 @findex TYPE_CODE_COMPLEX
20245 @findex gdb.TYPE_CODE_COMPLEX
20246 @item TYPE_CODE_COMPLEX
20247 A complex float type.
20249 @findex TYPE_CODE_TYPEDEF
20250 @findex gdb.TYPE_CODE_TYPEDEF
20251 @item TYPE_CODE_TYPEDEF
20252 A typedef to some other type.
20254 @findex TYPE_CODE_NAMESPACE
20255 @findex gdb.TYPE_CODE_NAMESPACE
20256 @item TYPE_CODE_NAMESPACE
20257 A C@t{++} namespace.
20259 @findex TYPE_CODE_DECFLOAT
20260 @findex gdb.TYPE_CODE_DECFLOAT
20261 @item TYPE_CODE_DECFLOAT
20262 A decimal floating point type.
20264 @findex TYPE_CODE_INTERNAL_FUNCTION
20265 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20266 @item TYPE_CODE_INTERNAL_FUNCTION
20267 A function internal to @value{GDBN}. This is the type used to represent
20268 convenience functions.
20271 @node Pretty Printing
20272 @subsubsection Pretty Printing
20274 @value{GDBN} provides a mechanism to allow pretty-printing of values
20275 using Python code. The pretty-printer API allows application-specific
20276 code to greatly simplify the display of complex objects. This
20277 mechanism works for both MI and the CLI.
20279 For example, here is how a C@t{++} @code{std::string} looks without a
20283 (@value{GDBP}) print s
20285 static npos = 4294967295,
20287 <std::allocator<char>> = @{
20288 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
20289 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
20290 _M_p = 0x804a014 "abcd"
20295 After a pretty-printer for @code{std::string} has been installed, only
20296 the contents are printed:
20299 (@value{GDBP}) print s
20303 A pretty-printer is just an object that holds a value and implements a
20304 specific interface, defined here.
20306 @defop Operation {pretty printer} children (self)
20307 @value{GDBN} will call this method on a pretty-printer to compute the
20308 children of the pretty-printer's value.
20310 This method must return an object conforming to the Python iterator
20311 protocol. Each item returned by the iterator must be a tuple holding
20312 two elements. The first element is the ``name'' of the child; the
20313 second element is the child's value. The value can be any Python
20314 object which is convertible to a @value{GDBN} value.
20316 This method is optional. If it does not exist, @value{GDBN} will act
20317 as though the value has no children.
20320 @defop Operation {pretty printer} display_hint (self)
20321 The CLI may call this method and use its result to change the
20322 formatting of a value. The result will also be supplied to an MI
20323 consumer as a @samp{displayhint} attribute of the variable being
20326 This method is optional. If it does exist, this method must return a
20329 Some display hints are predefined by @value{GDBN}:
20333 Indicate that the object being printed is ``array-like''. The CLI
20334 uses this to respect parameters such as @code{set print elements} and
20335 @code{set print array}.
20338 Indicate that the object being printed is ``map-like'', and that the
20339 children of this value can be assumed to alternate between keys and
20343 Indicate that the object being printed is ``string-like''. If the
20344 printer's @code{to_string} method returns a Python string of some
20345 kind, then @value{GDBN} will call its internal language-specific
20346 string-printing function to format the string. For the CLI this means
20347 adding quotation marks, possibly escaping some characters, respecting
20348 @code{set print elements}, and the like.
20352 @defop Operation {pretty printer} to_string (self)
20353 @value{GDBN} will call this method to display the string
20354 representation of the value passed to the object's constructor.
20356 When printing from the CLI, if the @code{to_string} method exists,
20357 then @value{GDBN} will prepend its result to the values returned by
20358 @code{children}. Exactly how this formatting is done is dependent on
20359 the display hint, and may change as more hints are added. Also,
20360 depending on the print settings (@pxref{Print Settings}), the CLI may
20361 print just the result of @code{to_string} in a stack trace, omitting
20362 the result of @code{children}.
20364 If this method returns a string, it is printed verbatim.
20366 Otherwise, if this method returns an instance of @code{gdb.Value},
20367 then @value{GDBN} prints this value. This may result in a call to
20368 another pretty-printer.
20370 If instead the method returns a Python value which is convertible to a
20371 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20372 the resulting value. Again, this may result in a call to another
20373 pretty-printer. Python scalars (integers, floats, and booleans) and
20374 strings are convertible to @code{gdb.Value}; other types are not.
20376 If the result is not one of these types, an exception is raised.
20379 @node Selecting Pretty-Printers
20380 @subsubsection Selecting Pretty-Printers
20382 The Python list @code{gdb.pretty_printers} contains an array of
20383 functions that have been registered via addition as a pretty-printer.
20384 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20387 A function on one of these lists is passed a single @code{gdb.Value}
20388 argument and should return a pretty-printer object conforming to the
20389 interface definition above (@pxref{Pretty Printing}). If a function
20390 cannot create a pretty-printer for the value, it should return
20393 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20394 @code{gdb.Objfile} and iteratively calls each function in the list for
20395 that @code{gdb.Objfile} until it receives a pretty-printer object.
20396 After these lists have been exhausted, it tries the global
20397 @code{gdb.pretty-printers} list, again calling each function until an
20398 object is returned.
20400 The order in which the objfiles are searched is not specified. For a
20401 given list, functions are always invoked from the head of the list,
20402 and iterated over sequentially until the end of the list, or a printer
20403 object is returned.
20405 Here is an example showing how a @code{std::string} printer might be
20409 class StdStringPrinter:
20410 "Print a std::string"
20412 def __init__ (self, val):
20415 def to_string (self):
20416 return self.val['_M_dataplus']['_M_p']
20418 def display_hint (self):
20422 And here is an example showing how a lookup function for the printer
20423 example above might be written.
20426 def str_lookup_function (val):
20428 lookup_tag = val.type.tag
20429 regex = re.compile ("^std::basic_string<char,.*>$")
20430 if lookup_tag == None:
20432 if regex.match (lookup_tag):
20433 return StdStringPrinter (val)
20438 The example lookup function extracts the value's type, and attempts to
20439 match it to a type that it can pretty-print. If it is a type the
20440 printer can pretty-print, it will return a printer object. If not, it
20441 returns @code{None}.
20443 We recommend that you put your core pretty-printers into a Python
20444 package. If your pretty-printers are for use with a library, we
20445 further recommend embedding a version number into the package name.
20446 This practice will enable @value{GDBN} to load multiple versions of
20447 your pretty-printers at the same time, because they will have
20450 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20451 can be evaluated multiple times without changing its meaning. An
20452 ideal auto-load file will consist solely of @code{import}s of your
20453 printer modules, followed by a call to a register pretty-printers with
20454 the current objfile.
20456 Taken as a whole, this approach will scale nicely to multiple
20457 inferiors, each potentially using a different library version.
20458 Embedding a version number in the Python package name will ensure that
20459 @value{GDBN} is able to load both sets of printers simultaneously.
20460 Then, because the search for pretty-printers is done by objfile, and
20461 because your auto-loaded code took care to register your library's
20462 printers with a specific objfile, @value{GDBN} will find the correct
20463 printers for the specific version of the library used by each
20466 To continue the @code{std::string} example (@pxref{Pretty Printing}),
20467 this code might appear in @code{gdb.libstdcxx.v6}:
20470 def register_printers (objfile):
20471 objfile.pretty_printers.add (str_lookup_function)
20475 And then the corresponding contents of the auto-load file would be:
20478 import gdb.libstdcxx.v6
20479 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20482 @node Commands In Python
20483 @subsubsection Commands In Python
20485 @cindex commands in python
20486 @cindex python commands
20487 You can implement new @value{GDBN} CLI commands in Python. A CLI
20488 command is implemented using an instance of the @code{gdb.Command}
20489 class, most commonly using a subclass.
20491 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20492 The object initializer for @code{Command} registers the new command
20493 with @value{GDBN}. This initializer is normally invoked from the
20494 subclass' own @code{__init__} method.
20496 @var{name} is the name of the command. If @var{name} consists of
20497 multiple words, then the initial words are looked for as prefix
20498 commands. In this case, if one of the prefix commands does not exist,
20499 an exception is raised.
20501 There is no support for multi-line commands.
20503 @var{command_class} should be one of the @samp{COMMAND_} constants
20504 defined below. This argument tells @value{GDBN} how to categorize the
20505 new command in the help system.
20507 @var{completer_class} is an optional argument. If given, it should be
20508 one of the @samp{COMPLETE_} constants defined below. This argument
20509 tells @value{GDBN} how to perform completion for this command. If not
20510 given, @value{GDBN} will attempt to complete using the object's
20511 @code{complete} method (see below); if no such method is found, an
20512 error will occur when completion is attempted.
20514 @var{prefix} is an optional argument. If @code{True}, then the new
20515 command is a prefix command; sub-commands of this command may be
20518 The help text for the new command is taken from the Python
20519 documentation string for the command's class, if there is one. If no
20520 documentation string is provided, the default value ``This command is
20521 not documented.'' is used.
20524 @cindex don't repeat Python command
20525 @defmethod Command dont_repeat
20526 By default, a @value{GDBN} command is repeated when the user enters a
20527 blank line at the command prompt. A command can suppress this
20528 behavior by invoking the @code{dont_repeat} method. This is similar
20529 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20532 @defmethod Command invoke argument from_tty
20533 This method is called by @value{GDBN} when this command is invoked.
20535 @var{argument} is a string. It is the argument to the command, after
20536 leading and trailing whitespace has been stripped.
20538 @var{from_tty} is a boolean argument. When true, this means that the
20539 command was entered by the user at the terminal; when false it means
20540 that the command came from elsewhere.
20542 If this method throws an exception, it is turned into a @value{GDBN}
20543 @code{error} call. Otherwise, the return value is ignored.
20546 @cindex completion of Python commands
20547 @defmethod Command complete text word
20548 This method is called by @value{GDBN} when the user attempts
20549 completion on this command. All forms of completion are handled by
20550 this method, that is, the @key{TAB} and @key{M-?} key bindings
20551 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20554 The arguments @var{text} and @var{word} are both strings. @var{text}
20555 holds the complete command line up to the cursor's location.
20556 @var{word} holds the last word of the command line; this is computed
20557 using a word-breaking heuristic.
20559 The @code{complete} method can return several values:
20562 If the return value is a sequence, the contents of the sequence are
20563 used as the completions. It is up to @code{complete} to ensure that the
20564 contents actually do complete the word. A zero-length sequence is
20565 allowed, it means that there were no completions available. Only
20566 string elements of the sequence are used; other elements in the
20567 sequence are ignored.
20570 If the return value is one of the @samp{COMPLETE_} constants defined
20571 below, then the corresponding @value{GDBN}-internal completion
20572 function is invoked, and its result is used.
20575 All other results are treated as though there were no available
20580 When a new command is registered, it must be declared as a member of
20581 some general class of commands. This is used to classify top-level
20582 commands in the on-line help system; note that prefix commands are not
20583 listed under their own category but rather that of their top-level
20584 command. The available classifications are represented by constants
20585 defined in the @code{gdb} module:
20588 @findex COMMAND_NONE
20589 @findex gdb.COMMAND_NONE
20591 The command does not belong to any particular class. A command in
20592 this category will not be displayed in any of the help categories.
20594 @findex COMMAND_RUNNING
20595 @findex gdb.COMMAND_RUNNING
20596 @item COMMAND_RUNNING
20597 The command is related to running the inferior. For example,
20598 @code{start}, @code{step}, and @code{continue} are in this category.
20599 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20600 commands in this category.
20602 @findex COMMAND_DATA
20603 @findex gdb.COMMAND_DATA
20605 The command is related to data or variables. For example,
20606 @code{call}, @code{find}, and @code{print} are in this category. Type
20607 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20610 @findex COMMAND_STACK
20611 @findex gdb.COMMAND_STACK
20612 @item COMMAND_STACK
20613 The command has to do with manipulation of the stack. For example,
20614 @code{backtrace}, @code{frame}, and @code{return} are in this
20615 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20616 list of commands in this category.
20618 @findex COMMAND_FILES
20619 @findex gdb.COMMAND_FILES
20620 @item COMMAND_FILES
20621 This class is used for file-related commands. For example,
20622 @code{file}, @code{list} and @code{section} are in this category.
20623 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20624 commands in this category.
20626 @findex COMMAND_SUPPORT
20627 @findex gdb.COMMAND_SUPPORT
20628 @item COMMAND_SUPPORT
20629 This should be used for ``support facilities'', generally meaning
20630 things that are useful to the user when interacting with @value{GDBN},
20631 but not related to the state of the inferior. For example,
20632 @code{help}, @code{make}, and @code{shell} are in this category. Type
20633 @kbd{help support} at the @value{GDBN} prompt to see a list of
20634 commands in this category.
20636 @findex COMMAND_STATUS
20637 @findex gdb.COMMAND_STATUS
20638 @item COMMAND_STATUS
20639 The command is an @samp{info}-related command, that is, related to the
20640 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20641 and @code{show} are in this category. Type @kbd{help status} at the
20642 @value{GDBN} prompt to see a list of commands in this category.
20644 @findex COMMAND_BREAKPOINTS
20645 @findex gdb.COMMAND_BREAKPOINTS
20646 @item COMMAND_BREAKPOINTS
20647 The command has to do with breakpoints. For example, @code{break},
20648 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20649 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20652 @findex COMMAND_TRACEPOINTS
20653 @findex gdb.COMMAND_TRACEPOINTS
20654 @item COMMAND_TRACEPOINTS
20655 The command has to do with tracepoints. For example, @code{trace},
20656 @code{actions}, and @code{tfind} are in this category. Type
20657 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20658 commands in this category.
20660 @findex COMMAND_OBSCURE
20661 @findex gdb.COMMAND_OBSCURE
20662 @item COMMAND_OBSCURE
20663 The command is only used in unusual circumstances, or is not of
20664 general interest to users. For example, @code{checkpoint},
20665 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20666 obscure} at the @value{GDBN} prompt to see a list of commands in this
20669 @findex COMMAND_MAINTENANCE
20670 @findex gdb.COMMAND_MAINTENANCE
20671 @item COMMAND_MAINTENANCE
20672 The command is only useful to @value{GDBN} maintainers. The
20673 @code{maintenance} and @code{flushregs} commands are in this category.
20674 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20675 commands in this category.
20678 A new command can use a predefined completion function, either by
20679 specifying it via an argument at initialization, or by returning it
20680 from the @code{complete} method. These predefined completion
20681 constants are all defined in the @code{gdb} module:
20684 @findex COMPLETE_NONE
20685 @findex gdb.COMPLETE_NONE
20686 @item COMPLETE_NONE
20687 This constant means that no completion should be done.
20689 @findex COMPLETE_FILENAME
20690 @findex gdb.COMPLETE_FILENAME
20691 @item COMPLETE_FILENAME
20692 This constant means that filename completion should be performed.
20694 @findex COMPLETE_LOCATION
20695 @findex gdb.COMPLETE_LOCATION
20696 @item COMPLETE_LOCATION
20697 This constant means that location completion should be done.
20698 @xref{Specify Location}.
20700 @findex COMPLETE_COMMAND
20701 @findex gdb.COMPLETE_COMMAND
20702 @item COMPLETE_COMMAND
20703 This constant means that completion should examine @value{GDBN}
20706 @findex COMPLETE_SYMBOL
20707 @findex gdb.COMPLETE_SYMBOL
20708 @item COMPLETE_SYMBOL
20709 This constant means that completion should be done using symbol names
20713 The following code snippet shows how a trivial CLI command can be
20714 implemented in Python:
20717 class HelloWorld (gdb.Command):
20718 """Greet the whole world."""
20720 def __init__ (self):
20721 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20723 def invoke (self, arg, from_tty):
20724 print "Hello, World!"
20729 The last line instantiates the class, and is necessary to trigger the
20730 registration of the command with @value{GDBN}. Depending on how the
20731 Python code is read into @value{GDBN}, you may need to import the
20732 @code{gdb} module explicitly.
20734 @node Functions In Python
20735 @subsubsection Writing new convenience functions
20737 @cindex writing convenience functions
20738 @cindex convenience functions in python
20739 @cindex python convenience functions
20740 @tindex gdb.Function
20742 You can implement new convenience functions (@pxref{Convenience Vars})
20743 in Python. A convenience function is an instance of a subclass of the
20744 class @code{gdb.Function}.
20746 @defmethod Function __init__ name
20747 The initializer for @code{Function} registers the new function with
20748 @value{GDBN}. The argument @var{name} is the name of the function,
20749 a string. The function will be visible to the user as a convenience
20750 variable of type @code{internal function}, whose name is the same as
20751 the given @var{name}.
20753 The documentation for the new function is taken from the documentation
20754 string for the new class.
20757 @defmethod Function invoke @var{*args}
20758 When a convenience function is evaluated, its arguments are converted
20759 to instances of @code{gdb.Value}, and then the function's
20760 @code{invoke} method is called. Note that @value{GDBN} does not
20761 predetermine the arity of convenience functions. Instead, all
20762 available arguments are passed to @code{invoke}, following the
20763 standard Python calling convention. In particular, a convenience
20764 function can have default values for parameters without ill effect.
20766 The return value of this method is used as its value in the enclosing
20767 expression. If an ordinary Python value is returned, it is converted
20768 to a @code{gdb.Value} following the usual rules.
20771 The following code snippet shows how a trivial convenience function can
20772 be implemented in Python:
20775 class Greet (gdb.Function):
20776 """Return string to greet someone.
20777 Takes a name as argument."""
20779 def __init__ (self):
20780 super (Greet, self).__init__ ("greet")
20782 def invoke (self, name):
20783 return "Hello, %s!" % name.string ()
20788 The last line instantiates the class, and is necessary to trigger the
20789 registration of the function with @value{GDBN}. Depending on how the
20790 Python code is read into @value{GDBN}, you may need to import the
20791 @code{gdb} module explicitly.
20793 @node Objfiles In Python
20794 @subsubsection Objfiles In Python
20796 @cindex objfiles in python
20797 @tindex gdb.Objfile
20799 @value{GDBN} loads symbols for an inferior from various
20800 symbol-containing files (@pxref{Files}). These include the primary
20801 executable file, any shared libraries used by the inferior, and any
20802 separate debug info files (@pxref{Separate Debug Files}).
20803 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20805 The following objfile-related functions are available in the
20808 @findex gdb.current_objfile
20809 @defun current_objfile
20810 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20811 sets the ``current objfile'' to the corresponding objfile. This
20812 function returns the current objfile. If there is no current objfile,
20813 this function returns @code{None}.
20816 @findex gdb.objfiles
20818 Return a sequence of all the objfiles current known to @value{GDBN}.
20819 @xref{Objfiles In Python}.
20822 Each objfile is represented by an instance of the @code{gdb.Objfile}
20825 @defivar Objfile filename
20826 The file name of the objfile as a string.
20829 @defivar Objfile pretty_printers
20830 The @code{pretty_printers} attribute is a list of functions. It is
20831 used to look up pretty-printers. A @code{Value} is passed to each
20832 function in order; if the function returns @code{None}, then the
20833 search continues. Otherwise, the return value should be an object
20834 which is used to format the value. @xref{Pretty Printing}, for more
20838 @node Frames In Python
20839 @subsubsection Accessing inferior stack frames from Python.
20841 @cindex frames in python
20842 When the debugged program stops, @value{GDBN} is able to analyze its call
20843 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20844 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20845 while its corresponding frame exists in the inferior's stack. If you try
20846 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20849 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20853 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20857 The following frame-related functions are available in the @code{gdb} module:
20859 @findex gdb.selected_frame
20860 @defun selected_frame
20861 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20864 @defun frame_stop_reason_string reason
20865 Return a string explaining the reason why @value{GDBN} stopped unwinding
20866 frames, as expressed by the given @var{reason} code (an integer, see the
20867 @code{unwind_stop_reason} method further down in this section).
20870 A @code{gdb.Frame} object has the following methods:
20873 @defmethod Frame is_valid
20874 Returns true if the @code{gdb.Frame} object is valid, false if not.
20875 A frame object can become invalid if the frame it refers to doesn't
20876 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20877 an exception if it is invalid at the time the method is called.
20880 @defmethod Frame name
20881 Returns the function name of the frame, or @code{None} if it can't be
20885 @defmethod Frame type
20886 Returns the type of the frame. The value can be one of
20887 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20888 or @code{gdb.SENTINEL_FRAME}.
20891 @defmethod Frame unwind_stop_reason
20892 Return an integer representing the reason why it's not possible to find
20893 more frames toward the outermost frame. Use
20894 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20895 function to a string.
20898 @defmethod Frame pc
20899 Returns the frame's resume address.
20902 @defmethod Frame block
20903 Return the frame's code block. @xref{Blocks In Python}.
20906 @defmethod Frame function
20907 Return the symbol for the function corresponding to this frame.
20908 @xref{Symbols In Python}.
20911 @defmethod Frame older
20912 Return the frame that called this frame.
20915 @defmethod Frame newer
20916 Return the frame called by this frame.
20919 @defmethod Frame find_sal
20920 Return the frame's symtab and line object.
20921 @xref{Symbol Tables In Python}.
20924 @defmethod Frame read_var variable @r{[}block@r{]}
20925 Return the value of @var{variable} in this frame. If the optional
20926 argument @var{block} is provided, search for the variable from that
20927 block; otherwise start at the frame's current block (which is
20928 determined by the frame's current program counter). @var{variable}
20929 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
20930 @code{gdb.Block} object.
20933 @defmethod Frame select
20934 Set this frame to be the selected frame. @xref{Stack, ,Examining the
20939 @node Blocks In Python
20940 @subsubsection Accessing frame blocks from Python.
20942 @cindex blocks in python
20945 Within each frame, @value{GDBN} maintains information on each block
20946 stored in that frame. These blocks are organized hierarchically, and
20947 are represented individually in Python as a @code{gdb.Block}.
20948 Please see @ref{Frames In Python}, for a more in-depth discussion on
20949 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
20950 detailed technical information on @value{GDBN}'s book-keeping of the
20953 The following block-related functions are available in the @code{gdb}
20956 @findex gdb.block_for_pc
20957 @defun block_for_pc pc
20958 Return the @code{gdb.Block} containing the given @var{pc} value. If the
20959 block cannot be found for the @var{pc} value specified, the function
20960 will return @code{None}.
20963 A @code{gdb.Block} object has the following attributes:
20966 @defivar Block start
20967 The start address of the block. This attribute is not writable.
20971 The end address of the block. This attribute is not writable.
20974 @defivar Block function
20975 The name of the block represented as a @code{gdb.Symbol}. If the
20976 block is not named, then this attribute holds @code{None}. This
20977 attribute is not writable.
20980 @defivar Block superblock
20981 The block containing this block. If this parent block does not exist,
20982 this attribute holds @code{None}. This attribute is not writable.
20986 @node Symbols In Python
20987 @subsubsection Python representation of Symbols.
20989 @cindex symbols in python
20992 @value{GDBN} represents every variable, function and type as an
20993 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
20994 Similarly, Python represents these symbols in @value{GDBN} with the
20995 @code{gdb.Symbol} object.
20997 The following symbol-related functions are available in the @code{gdb}
21000 @findex gdb.lookup_symbol
21001 @defun lookup_symbol name [block] [domain]
21002 This function searches for a symbol by name. The search scope can be
21003 restricted to the parameters defined in the optional domain and block
21006 @var{name} is the name of the symbol. It must be a string. The
21007 optional @var{block} argument restricts the search to symbols visible
21008 in that @var{block}. The @var{block} argument must be a
21009 @code{gdb.Block} object. The optional @var{domain} argument restricts
21010 the search to the domain type. The @var{domain} argument must be a
21011 domain constant defined in the @code{gdb} module and described later
21015 A @code{gdb.Symbol} object has the following attributes:
21018 @defivar Symbol symtab
21019 The symbol table in which the symbol appears. This attribute is
21020 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21021 Python}. This attribute is not writable.
21024 @defivar Symbol name
21025 The name of the symbol as a string. This attribute is not writable.
21028 @defivar Symbol linkage_name
21029 The name of the symbol, as used by the linker (i.e., may be mangled).
21030 This attribute is not writable.
21033 @defivar Symbol print_name
21034 The name of the symbol in a form suitable for output. This is either
21035 @code{name} or @code{linkage_name}, depending on whether the user
21036 asked @value{GDBN} to display demangled or mangled names.
21039 @defivar Symbol addr_class
21040 The address class of the symbol. This classifies how to find the value
21041 of a symbol. Each address class is a constant defined in the
21042 @code{gdb} module and described later in this chapter.
21045 @defivar Symbol is_argument
21046 @code{True} if the symbol is an argument of a function.
21049 @defivar Symbol is_constant
21050 @code{True} if the symbol is a constant.
21053 @defivar Symbol is_function
21054 @code{True} if the symbol is a function or a method.
21057 @defivar Symbol is_variable
21058 @code{True} if the symbol is a variable.
21062 The available domain categories in @code{gdb.Symbol} are represented
21063 as constants in the @code{gdb} module:
21066 @findex SYMBOL_UNDEF_DOMAIN
21067 @findex gdb.SYMBOL_UNDEF_DOMAIN
21068 @item SYMBOL_UNDEF_DOMAIN
21069 This is used when a domain has not been discovered or none of the
21070 following domains apply. This usually indicates an error either
21071 in the symbol information or in @value{GDBN}'s handling of symbols.
21072 @findex SYMBOL_VAR_DOMAIN
21073 @findex gdb.SYMBOL_VAR_DOMAIN
21074 @item SYMBOL_VAR_DOMAIN
21075 This domain contains variables, function names, typedef names and enum
21077 @findex SYMBOL_STRUCT_DOMAIN
21078 @findex gdb.SYMBOL_STRUCT_DOMAIN
21079 @item SYMBOL_STRUCT_DOMAIN
21080 This domain holds struct, union and enum type names.
21081 @findex SYMBOL_LABEL_DOMAIN
21082 @findex gdb.SYMBOL_LABEL_DOMAIN
21083 @item SYMBOL_LABEL_DOMAIN
21084 This domain contains names of labels (for gotos).
21085 @findex SYMBOL_VARIABLES_DOMAIN
21086 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21087 @item SYMBOL_VARIABLES_DOMAIN
21088 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21089 contains everything minus functions and types.
21090 @findex SYMBOL_FUNCTIONS_DOMAIN
21091 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21092 @item SYMBOL_FUNCTION_DOMAIN
21093 This domain contains all functions.
21094 @findex SYMBOL_TYPES_DOMAIN
21095 @findex gdb.SYMBOL_TYPES_DOMAIN
21096 @item SYMBOL_TYPES_DOMAIN
21097 This domain contains all types.
21100 The available address class categories in @code{gdb.Symbol} are represented
21101 as constants in the @code{gdb} module:
21104 @findex SYMBOL_LOC_UNDEF
21105 @findex gdb.SYMBOL_LOC_UNDEF
21106 @item SYMBOL_LOC_UNDEF
21107 If this is returned by address class, it indicates an error either in
21108 the symbol information or in @value{GDBN}'s handling of symbols.
21109 @findex SYMBOL_LOC_CONST
21110 @findex gdb.SYMBOL_LOC_CONST
21111 @item SYMBOL_LOC_CONST
21112 Value is constant int.
21113 @findex SYMBOL_LOC_STATIC
21114 @findex gdb.SYMBOL_LOC_STATIC
21115 @item SYMBOL_LOC_STATIC
21116 Value is at a fixed address.
21117 @findex SYMBOL_LOC_REGISTER
21118 @findex gdb.SYMBOL_LOC_REGISTER
21119 @item SYMBOL_LOC_REGISTER
21120 Value is in a register.
21121 @findex SYMBOL_LOC_ARG
21122 @findex gdb.SYMBOL_LOC_ARG
21123 @item SYMBOL_LOC_ARG
21124 Value is an argument. This value is at the offset stored within the
21125 symbol inside the frame's argument list.
21126 @findex SYMBOL_LOC_REF_ARG
21127 @findex gdb.SYMBOL_LOC_REF_ARG
21128 @item SYMBOL_LOC_REF_ARG
21129 Value address is stored in the frame's argument list. Just like
21130 @code{LOC_ARG} except that the value's address is stored at the
21131 offset, not the value itself.
21132 @findex SYMBOL_LOC_REGPARM_ADDR
21133 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21134 @item SYMBOL_LOC_REGPARM_ADDR
21135 Value is a specified register. Just like @code{LOC_REGISTER} except
21136 the register holds the address of the argument instead of the argument
21138 @findex SYMBOL_LOC_LOCAL
21139 @findex gdb.SYMBOL_LOC_LOCAL
21140 @item SYMBOL_LOC_LOCAL
21141 Value is a local variable.
21142 @findex SYMBOL_LOC_TYPEDEF
21143 @findex gdb.SYMBOL_LOC_TYPEDEF
21144 @item SYMBOL_LOC_TYPEDEF
21145 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21147 @findex SYMBOL_LOC_BLOCK
21148 @findex gdb.SYMBOL_LOC_BLOCK
21149 @item SYMBOL_LOC_BLOCK
21151 @findex SYMBOL_LOC_CONST_BYTES
21152 @findex gdb.SYMBOL_LOC_CONST_BYTES
21153 @item SYMBOL_LOC_CONST_BYTES
21154 Value is a byte-sequence.
21155 @findex SYMBOL_LOC_UNRESOLVED
21156 @findex gdb.SYMBOL_LOC_UNRESOLVED
21157 @item SYMBOL_LOC_UNRESOLVED
21158 Value is at a fixed address, but the address of the variable has to be
21159 determined from the minimal symbol table whenever the variable is
21161 @findex SYMBOL_LOC_OPTIMIZED_OUT
21162 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21163 @item SYMBOL_LOC_OPTIMIZED_OUT
21164 The value does not actually exist in the program.
21165 @findex SYMBOL_LOC_COMPUTED
21166 @findex gdb.SYMBOL_LOC_COMPUTED
21167 @item SYMBOL_LOC_COMPUTED
21168 The value's address is a computed location.
21171 @node Symbol Tables In Python
21172 @subsubsection Symbol table representation in Python.
21174 @cindex symbol tables in python
21176 @tindex gdb.Symtab_and_line
21178 Access to symbol table data maintained by @value{GDBN} on the inferior
21179 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21180 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21181 from the @code{find_sal} method in @code{gdb.Frame} object.
21182 @xref{Frames In Python}.
21184 For more information on @value{GDBN}'s symbol table management, see
21185 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21187 A @code{gdb.Symtab_and_line} object has the following attributes:
21190 @defivar Symtab_and_line symtab
21191 The symbol table object (@code{gdb.Symtab}) for this frame.
21192 This attribute is not writable.
21195 @defivar Symtab_and_line pc
21196 Indicates the current program counter address. This attribute is not
21200 @defivar Symtab_and_line line
21201 Indicates the current line number for this object. This
21202 attribute is not writable.
21206 A @code{gdb.Symtab} object has the following attributes:
21209 @defivar Symtab filename
21210 The symbol table's source filename. This attribute is not writable.
21213 @defivar Symtab objfile
21214 The symbol table's backing object file. @xref{Objfiles In Python}.
21215 This attribute is not writable.
21219 The following methods are provided:
21222 @defmethod Symtab fullname
21223 Return the symbol table's source absolute file name.
21227 @node Lazy Strings In Python
21228 @subsubsection Python representation of lazy strings.
21230 @cindex lazy strings in python
21231 @tindex gdb.LazyString
21233 A @dfn{lazy string} is a string whose contents is not retrieved or
21234 encoded until it is needed.
21236 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21237 @code{address} that points to a region of memory, an @code{encoding}
21238 that will be used to encode that region of memory, and a @code{length}
21239 to delimit the region of memory that represents the string. The
21240 difference between a @code{gdb.LazyString} and a string wrapped within
21241 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21242 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21243 retrieved and encoded during printing, while a @code{gdb.Value}
21244 wrapping a string is immediately retrieved and encoded on creation.
21246 A @code{gdb.LazyString} object has the following functions:
21248 @defmethod LazyString value
21249 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21250 will point to the string in memory, but will lose all the delayed
21251 retrieval, encoding and handling that @value{GDBN} applies to a
21252 @code{gdb.LazyString}.
21255 @defivar LazyString address
21256 This attribute holds the address of the string. This attribute is not
21260 @defivar LazyString length
21261 This attribute holds the length of the string in characters. If the
21262 length is -1, then the string will be fetched and encoded up to the
21263 first null of appropriate width. This attribute is not writable.
21266 @defivar LazyString encoding
21267 This attribute holds the encoding that will be applied to the string
21268 when the string is printed by @value{GDBN}. If the encoding is not
21269 set, or contains an empty string, then @value{GDBN} will select the
21270 most appropriate encoding when the string is printed. This attribute
21274 @defivar LazyString type
21275 This attribute holds the type that is represented by the lazy string's
21276 type. For a lazy string this will always be a pointer type. To
21277 resolve this to the lazy string's character type, use the type's
21278 @code{target} method. @xref{Types In Python}. This attribute is not
21283 @chapter Command Interpreters
21284 @cindex command interpreters
21286 @value{GDBN} supports multiple command interpreters, and some command
21287 infrastructure to allow users or user interface writers to switch
21288 between interpreters or run commands in other interpreters.
21290 @value{GDBN} currently supports two command interpreters, the console
21291 interpreter (sometimes called the command-line interpreter or @sc{cli})
21292 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21293 describes both of these interfaces in great detail.
21295 By default, @value{GDBN} will start with the console interpreter.
21296 However, the user may choose to start @value{GDBN} with another
21297 interpreter by specifying the @option{-i} or @option{--interpreter}
21298 startup options. Defined interpreters include:
21302 @cindex console interpreter
21303 The traditional console or command-line interpreter. This is the most often
21304 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21305 @value{GDBN} will use this interpreter.
21308 @cindex mi interpreter
21309 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21310 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21311 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21315 @cindex mi2 interpreter
21316 The current @sc{gdb/mi} interface.
21319 @cindex mi1 interpreter
21320 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21324 @cindex invoke another interpreter
21325 The interpreter being used by @value{GDBN} may not be dynamically
21326 switched at runtime. Although possible, this could lead to a very
21327 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21328 enters the command "interpreter-set console" in a console view,
21329 @value{GDBN} would switch to using the console interpreter, rendering
21330 the IDE inoperable!
21332 @kindex interpreter-exec
21333 Although you may only choose a single interpreter at startup, you may execute
21334 commands in any interpreter from the current interpreter using the appropriate
21335 command. If you are running the console interpreter, simply use the
21336 @code{interpreter-exec} command:
21339 interpreter-exec mi "-data-list-register-names"
21342 @sc{gdb/mi} has a similar command, although it is only available in versions of
21343 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21346 @chapter @value{GDBN} Text User Interface
21348 @cindex Text User Interface
21351 * TUI Overview:: TUI overview
21352 * TUI Keys:: TUI key bindings
21353 * TUI Single Key Mode:: TUI single key mode
21354 * TUI Commands:: TUI-specific commands
21355 * TUI Configuration:: TUI configuration variables
21358 The @value{GDBN} Text User Interface (TUI) is a terminal
21359 interface which uses the @code{curses} library to show the source
21360 file, the assembly output, the program registers and @value{GDBN}
21361 commands in separate text windows. The TUI mode is supported only
21362 on platforms where a suitable version of the @code{curses} library
21365 @pindex @value{GDBTUI}
21366 The TUI mode is enabled by default when you invoke @value{GDBN} as
21367 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21368 You can also switch in and out of TUI mode while @value{GDBN} runs by
21369 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21370 @xref{TUI Keys, ,TUI Key Bindings}.
21373 @section TUI Overview
21375 In TUI mode, @value{GDBN} can display several text windows:
21379 This window is the @value{GDBN} command window with the @value{GDBN}
21380 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21381 managed using readline.
21384 The source window shows the source file of the program. The current
21385 line and active breakpoints are displayed in this window.
21388 The assembly window shows the disassembly output of the program.
21391 This window shows the processor registers. Registers are highlighted
21392 when their values change.
21395 The source and assembly windows show the current program position
21396 by highlighting the current line and marking it with a @samp{>} marker.
21397 Breakpoints are indicated with two markers. The first marker
21398 indicates the breakpoint type:
21402 Breakpoint which was hit at least once.
21405 Breakpoint which was never hit.
21408 Hardware breakpoint which was hit at least once.
21411 Hardware breakpoint which was never hit.
21414 The second marker indicates whether the breakpoint is enabled or not:
21418 Breakpoint is enabled.
21421 Breakpoint is disabled.
21424 The source, assembly and register windows are updated when the current
21425 thread changes, when the frame changes, or when the program counter
21428 These windows are not all visible at the same time. The command
21429 window is always visible. The others can be arranged in several
21440 source and assembly,
21443 source and registers, or
21446 assembly and registers.
21449 A status line above the command window shows the following information:
21453 Indicates the current @value{GDBN} target.
21454 (@pxref{Targets, ,Specifying a Debugging Target}).
21457 Gives the current process or thread number.
21458 When no process is being debugged, this field is set to @code{No process}.
21461 Gives the current function name for the selected frame.
21462 The name is demangled if demangling is turned on (@pxref{Print Settings}).
21463 When there is no symbol corresponding to the current program counter,
21464 the string @code{??} is displayed.
21467 Indicates the current line number for the selected frame.
21468 When the current line number is not known, the string @code{??} is displayed.
21471 Indicates the current program counter address.
21475 @section TUI Key Bindings
21476 @cindex TUI key bindings
21478 The TUI installs several key bindings in the readline keymaps
21479 (@pxref{Command Line Editing}). The following key bindings
21480 are installed for both TUI mode and the @value{GDBN} standard mode.
21489 Enter or leave the TUI mode. When leaving the TUI mode,
21490 the curses window management stops and @value{GDBN} operates using
21491 its standard mode, writing on the terminal directly. When reentering
21492 the TUI mode, control is given back to the curses windows.
21493 The screen is then refreshed.
21497 Use a TUI layout with only one window. The layout will
21498 either be @samp{source} or @samp{assembly}. When the TUI mode
21499 is not active, it will switch to the TUI mode.
21501 Think of this key binding as the Emacs @kbd{C-x 1} binding.
21505 Use a TUI layout with at least two windows. When the current
21506 layout already has two windows, the next layout with two windows is used.
21507 When a new layout is chosen, one window will always be common to the
21508 previous layout and the new one.
21510 Think of it as the Emacs @kbd{C-x 2} binding.
21514 Change the active window. The TUI associates several key bindings
21515 (like scrolling and arrow keys) with the active window. This command
21516 gives the focus to the next TUI window.
21518 Think of it as the Emacs @kbd{C-x o} binding.
21522 Switch in and out of the TUI SingleKey mode that binds single
21523 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
21526 The following key bindings only work in the TUI mode:
21531 Scroll the active window one page up.
21535 Scroll the active window one page down.
21539 Scroll the active window one line up.
21543 Scroll the active window one line down.
21547 Scroll the active window one column left.
21551 Scroll the active window one column right.
21555 Refresh the screen.
21558 Because the arrow keys scroll the active window in the TUI mode, they
21559 are not available for their normal use by readline unless the command
21560 window has the focus. When another window is active, you must use
21561 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
21562 and @kbd{C-f} to control the command window.
21564 @node TUI Single Key Mode
21565 @section TUI Single Key Mode
21566 @cindex TUI single key mode
21568 The TUI also provides a @dfn{SingleKey} mode, which binds several
21569 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
21570 switch into this mode, where the following key bindings are used:
21573 @kindex c @r{(SingleKey TUI key)}
21577 @kindex d @r{(SingleKey TUI key)}
21581 @kindex f @r{(SingleKey TUI key)}
21585 @kindex n @r{(SingleKey TUI key)}
21589 @kindex q @r{(SingleKey TUI key)}
21591 exit the SingleKey mode.
21593 @kindex r @r{(SingleKey TUI key)}
21597 @kindex s @r{(SingleKey TUI key)}
21601 @kindex u @r{(SingleKey TUI key)}
21605 @kindex v @r{(SingleKey TUI key)}
21609 @kindex w @r{(SingleKey TUI key)}
21614 Other keys temporarily switch to the @value{GDBN} command prompt.
21615 The key that was pressed is inserted in the editing buffer so that
21616 it is possible to type most @value{GDBN} commands without interaction
21617 with the TUI SingleKey mode. Once the command is entered the TUI
21618 SingleKey mode is restored. The only way to permanently leave
21619 this mode is by typing @kbd{q} or @kbd{C-x s}.
21623 @section TUI-specific Commands
21624 @cindex TUI commands
21626 The TUI has specific commands to control the text windows.
21627 These commands are always available, even when @value{GDBN} is not in
21628 the TUI mode. When @value{GDBN} is in the standard mode, most
21629 of these commands will automatically switch to the TUI mode.
21634 List and give the size of all displayed windows.
21638 Display the next layout.
21641 Display the previous layout.
21644 Display the source window only.
21647 Display the assembly window only.
21650 Display the source and assembly window.
21653 Display the register window together with the source or assembly window.
21657 Make the next window active for scrolling.
21660 Make the previous window active for scrolling.
21663 Make the source window active for scrolling.
21666 Make the assembly window active for scrolling.
21669 Make the register window active for scrolling.
21672 Make the command window active for scrolling.
21676 Refresh the screen. This is similar to typing @kbd{C-L}.
21678 @item tui reg float
21680 Show the floating point registers in the register window.
21682 @item tui reg general
21683 Show the general registers in the register window.
21686 Show the next register group. The list of register groups as well as
21687 their order is target specific. The predefined register groups are the
21688 following: @code{general}, @code{float}, @code{system}, @code{vector},
21689 @code{all}, @code{save}, @code{restore}.
21691 @item tui reg system
21692 Show the system registers in the register window.
21696 Update the source window and the current execution point.
21698 @item winheight @var{name} +@var{count}
21699 @itemx winheight @var{name} -@var{count}
21701 Change the height of the window @var{name} by @var{count}
21702 lines. Positive counts increase the height, while negative counts
21705 @item tabset @var{nchars}
21707 Set the width of tab stops to be @var{nchars} characters.
21710 @node TUI Configuration
21711 @section TUI Configuration Variables
21712 @cindex TUI configuration variables
21714 Several configuration variables control the appearance of TUI windows.
21717 @item set tui border-kind @var{kind}
21718 @kindex set tui border-kind
21719 Select the border appearance for the source, assembly and register windows.
21720 The possible values are the following:
21723 Use a space character to draw the border.
21726 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
21729 Use the Alternate Character Set to draw the border. The border is
21730 drawn using character line graphics if the terminal supports them.
21733 @item set tui border-mode @var{mode}
21734 @kindex set tui border-mode
21735 @itemx set tui active-border-mode @var{mode}
21736 @kindex set tui active-border-mode
21737 Select the display attributes for the borders of the inactive windows
21738 or the active window. The @var{mode} can be one of the following:
21741 Use normal attributes to display the border.
21747 Use reverse video mode.
21750 Use half bright mode.
21752 @item half-standout
21753 Use half bright and standout mode.
21756 Use extra bright or bold mode.
21758 @item bold-standout
21759 Use extra bright or bold and standout mode.
21764 @chapter Using @value{GDBN} under @sc{gnu} Emacs
21767 @cindex @sc{gnu} Emacs
21768 A special interface allows you to use @sc{gnu} Emacs to view (and
21769 edit) the source files for the program you are debugging with
21772 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
21773 executable file you want to debug as an argument. This command starts
21774 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
21775 created Emacs buffer.
21776 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
21778 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
21783 All ``terminal'' input and output goes through an Emacs buffer, called
21786 This applies both to @value{GDBN} commands and their output, and to the input
21787 and output done by the program you are debugging.
21789 This is useful because it means that you can copy the text of previous
21790 commands and input them again; you can even use parts of the output
21793 All the facilities of Emacs' Shell mode are available for interacting
21794 with your program. In particular, you can send signals the usual
21795 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
21799 @value{GDBN} displays source code through Emacs.
21801 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
21802 source file for that frame and puts an arrow (@samp{=>}) at the
21803 left margin of the current line. Emacs uses a separate buffer for
21804 source display, and splits the screen to show both your @value{GDBN} session
21807 Explicit @value{GDBN} @code{list} or search commands still produce output as
21808 usual, but you probably have no reason to use them from Emacs.
21811 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
21812 a graphical mode, enabled by default, which provides further buffers
21813 that can control the execution and describe the state of your program.
21814 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
21816 If you specify an absolute file name when prompted for the @kbd{M-x
21817 gdb} argument, then Emacs sets your current working directory to where
21818 your program resides. If you only specify the file name, then Emacs
21819 sets your current working directory to to the directory associated
21820 with the previous buffer. In this case, @value{GDBN} may find your
21821 program by searching your environment's @code{PATH} variable, but on
21822 some operating systems it might not find the source. So, although the
21823 @value{GDBN} input and output session proceeds normally, the auxiliary
21824 buffer does not display the current source and line of execution.
21826 The initial working directory of @value{GDBN} is printed on the top
21827 line of the GUD buffer and this serves as a default for the commands
21828 that specify files for @value{GDBN} to operate on. @xref{Files,
21829 ,Commands to Specify Files}.
21831 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
21832 need to call @value{GDBN} by a different name (for example, if you
21833 keep several configurations around, with different names) you can
21834 customize the Emacs variable @code{gud-gdb-command-name} to run the
21837 In the GUD buffer, you can use these special Emacs commands in
21838 addition to the standard Shell mode commands:
21842 Describe the features of Emacs' GUD Mode.
21845 Execute to another source line, like the @value{GDBN} @code{step} command; also
21846 update the display window to show the current file and location.
21849 Execute to next source line in this function, skipping all function
21850 calls, like the @value{GDBN} @code{next} command. Then update the display window
21851 to show the current file and location.
21854 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
21855 display window accordingly.
21858 Execute until exit from the selected stack frame, like the @value{GDBN}
21859 @code{finish} command.
21862 Continue execution of your program, like the @value{GDBN} @code{continue}
21866 Go up the number of frames indicated by the numeric argument
21867 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
21868 like the @value{GDBN} @code{up} command.
21871 Go down the number of frames indicated by the numeric argument, like the
21872 @value{GDBN} @code{down} command.
21875 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
21876 tells @value{GDBN} to set a breakpoint on the source line point is on.
21878 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
21879 separate frame which shows a backtrace when the GUD buffer is current.
21880 Move point to any frame in the stack and type @key{RET} to make it
21881 become the current frame and display the associated source in the
21882 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21883 selected frame become the current one. In graphical mode, the
21884 speedbar displays watch expressions.
21886 If you accidentally delete the source-display buffer, an easy way to get
21887 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21888 request a frame display; when you run under Emacs, this recreates
21889 the source buffer if necessary to show you the context of the current
21892 The source files displayed in Emacs are in ordinary Emacs buffers
21893 which are visiting the source files in the usual way. You can edit
21894 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21895 communicates with Emacs in terms of line numbers. If you add or
21896 delete lines from the text, the line numbers that @value{GDBN} knows cease
21897 to correspond properly with the code.
21899 A more detailed description of Emacs' interaction with @value{GDBN} is
21900 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21903 @c The following dropped because Epoch is nonstandard. Reactivate
21904 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21906 @kindex Emacs Epoch environment
21910 Version 18 of @sc{gnu} Emacs has a built-in window system
21911 called the @code{epoch}
21912 environment. Users of this environment can use a new command,
21913 @code{inspect} which performs identically to @code{print} except that
21914 each value is printed in its own window.
21919 @chapter The @sc{gdb/mi} Interface
21921 @unnumberedsec Function and Purpose
21923 @cindex @sc{gdb/mi}, its purpose
21924 @sc{gdb/mi} is a line based machine oriented text interface to
21925 @value{GDBN} and is activated by specifying using the
21926 @option{--interpreter} command line option (@pxref{Mode Options}). It
21927 is specifically intended to support the development of systems which
21928 use the debugger as just one small component of a larger system.
21930 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21931 in the form of a reference manual.
21933 Note that @sc{gdb/mi} is still under construction, so some of the
21934 features described below are incomplete and subject to change
21935 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21937 @unnumberedsec Notation and Terminology
21939 @cindex notational conventions, for @sc{gdb/mi}
21940 This chapter uses the following notation:
21944 @code{|} separates two alternatives.
21947 @code{[ @var{something} ]} indicates that @var{something} is optional:
21948 it may or may not be given.
21951 @code{( @var{group} )*} means that @var{group} inside the parentheses
21952 may repeat zero or more times.
21955 @code{( @var{group} )+} means that @var{group} inside the parentheses
21956 may repeat one or more times.
21959 @code{"@var{string}"} means a literal @var{string}.
21963 @heading Dependencies
21967 * GDB/MI General Design::
21968 * GDB/MI Command Syntax::
21969 * GDB/MI Compatibility with CLI::
21970 * GDB/MI Development and Front Ends::
21971 * GDB/MI Output Records::
21972 * GDB/MI Simple Examples::
21973 * GDB/MI Command Description Format::
21974 * GDB/MI Breakpoint Commands::
21975 * GDB/MI Program Context::
21976 * GDB/MI Thread Commands::
21977 * GDB/MI Program Execution::
21978 * GDB/MI Stack Manipulation::
21979 * GDB/MI Variable Objects::
21980 * GDB/MI Data Manipulation::
21981 * GDB/MI Tracepoint Commands::
21982 * GDB/MI Symbol Query::
21983 * GDB/MI File Commands::
21985 * GDB/MI Kod Commands::
21986 * GDB/MI Memory Overlay Commands::
21987 * GDB/MI Signal Handling Commands::
21989 * GDB/MI Target Manipulation::
21990 * GDB/MI File Transfer Commands::
21991 * GDB/MI Miscellaneous Commands::
21994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21995 @node GDB/MI General Design
21996 @section @sc{gdb/mi} General Design
21997 @cindex GDB/MI General Design
21999 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22000 parts---commands sent to @value{GDBN}, responses to those commands
22001 and notifications. Each command results in exactly one response,
22002 indicating either successful completion of the command, or an error.
22003 For the commands that do not resume the target, the response contains the
22004 requested information. For the commands that resume the target, the
22005 response only indicates whether the target was successfully resumed.
22006 Notifications is the mechanism for reporting changes in the state of the
22007 target, or in @value{GDBN} state, that cannot conveniently be associated with
22008 a command and reported as part of that command response.
22010 The important examples of notifications are:
22014 Exec notifications. These are used to report changes in
22015 target state---when a target is resumed, or stopped. It would not
22016 be feasible to include this information in response of resuming
22017 commands, because one resume commands can result in multiple events in
22018 different threads. Also, quite some time may pass before any event
22019 happens in the target, while a frontend needs to know whether the resuming
22020 command itself was successfully executed.
22023 Console output, and status notifications. Console output
22024 notifications are used to report output of CLI commands, as well as
22025 diagnostics for other commands. Status notifications are used to
22026 report the progress of a long-running operation. Naturally, including
22027 this information in command response would mean no output is produced
22028 until the command is finished, which is undesirable.
22031 General notifications. Commands may have various side effects on
22032 the @value{GDBN} or target state beyond their official purpose. For example,
22033 a command may change the selected thread. Although such changes can
22034 be included in command response, using notification allows for more
22035 orthogonal frontend design.
22039 There's no guarantee that whenever an MI command reports an error,
22040 @value{GDBN} or the target are in any specific state, and especially,
22041 the state is not reverted to the state before the MI command was
22042 processed. Therefore, whenever an MI command results in an error,
22043 we recommend that the frontend refreshes all the information shown in
22044 the user interface.
22048 * Context management::
22049 * Asynchronous and non-stop modes::
22053 @node Context management
22054 @subsection Context management
22056 In most cases when @value{GDBN} accesses the target, this access is
22057 done in context of a specific thread and frame (@pxref{Frames}).
22058 Often, even when accessing global data, the target requires that a thread
22059 be specified. The CLI interface maintains the selected thread and frame,
22060 and supplies them to target on each command. This is convenient,
22061 because a command line user would not want to specify that information
22062 explicitly on each command, and because user interacts with
22063 @value{GDBN} via a single terminal, so no confusion is possible as
22064 to what thread and frame are the current ones.
22066 In the case of MI, the concept of selected thread and frame is less
22067 useful. First, a frontend can easily remember this information
22068 itself. Second, a graphical frontend can have more than one window,
22069 each one used for debugging a different thread, and the frontend might
22070 want to access additional threads for internal purposes. This
22071 increases the risk that by relying on implicitly selected thread, the
22072 frontend may be operating on a wrong one. Therefore, each MI command
22073 should explicitly specify which thread and frame to operate on. To
22074 make it possible, each MI command accepts the @samp{--thread} and
22075 @samp{--frame} options, the value to each is @value{GDBN} identifier
22076 for thread and frame to operate on.
22078 Usually, each top-level window in a frontend allows the user to select
22079 a thread and a frame, and remembers the user selection for further
22080 operations. However, in some cases @value{GDBN} may suggest that the
22081 current thread be changed. For example, when stopping on a breakpoint
22082 it is reasonable to switch to the thread where breakpoint is hit. For
22083 another example, if the user issues the CLI @samp{thread} command via
22084 the frontend, it is desirable to change the frontend's selected thread to the
22085 one specified by user. @value{GDBN} communicates the suggestion to
22086 change current thread using the @samp{=thread-selected} notification.
22087 No such notification is available for the selected frame at the moment.
22089 Note that historically, MI shares the selected thread with CLI, so
22090 frontends used the @code{-thread-select} to execute commands in the
22091 right context. However, getting this to work right is cumbersome. The
22092 simplest way is for frontend to emit @code{-thread-select} command
22093 before every command. This doubles the number of commands that need
22094 to be sent. The alternative approach is to suppress @code{-thread-select}
22095 if the selected thread in @value{GDBN} is supposed to be identical to the
22096 thread the frontend wants to operate on. However, getting this
22097 optimization right can be tricky. In particular, if the frontend
22098 sends several commands to @value{GDBN}, and one of the commands changes the
22099 selected thread, then the behaviour of subsequent commands will
22100 change. So, a frontend should either wait for response from such
22101 problematic commands, or explicitly add @code{-thread-select} for
22102 all subsequent commands. No frontend is known to do this exactly
22103 right, so it is suggested to just always pass the @samp{--thread} and
22104 @samp{--frame} options.
22106 @node Asynchronous and non-stop modes
22107 @subsection Asynchronous command execution and non-stop mode
22109 On some targets, @value{GDBN} is capable of processing MI commands
22110 even while the target is running. This is called @dfn{asynchronous
22111 command execution} (@pxref{Background Execution}). The frontend may
22112 specify a preferrence for asynchronous execution using the
22113 @code{-gdb-set target-async 1} command, which should be emitted before
22114 either running the executable or attaching to the target. After the
22115 frontend has started the executable or attached to the target, it can
22116 find if asynchronous execution is enabled using the
22117 @code{-list-target-features} command.
22119 Even if @value{GDBN} can accept a command while target is running,
22120 many commands that access the target do not work when the target is
22121 running. Therefore, asynchronous command execution is most useful
22122 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22123 it is possible to examine the state of one thread, while other threads
22126 When a given thread is running, MI commands that try to access the
22127 target in the context of that thread may not work, or may work only on
22128 some targets. In particular, commands that try to operate on thread's
22129 stack will not work, on any target. Commands that read memory, or
22130 modify breakpoints, may work or not work, depending on the target. Note
22131 that even commands that operate on global state, such as @code{print},
22132 @code{set}, and breakpoint commands, still access the target in the
22133 context of a specific thread, so frontend should try to find a
22134 stopped thread and perform the operation on that thread (using the
22135 @samp{--thread} option).
22137 Which commands will work in the context of a running thread is
22138 highly target dependent. However, the two commands
22139 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22140 to find the state of a thread, will always work.
22142 @node Thread groups
22143 @subsection Thread groups
22144 @value{GDBN} may be used to debug several processes at the same time.
22145 On some platfroms, @value{GDBN} may support debugging of several
22146 hardware systems, each one having several cores with several different
22147 processes running on each core. This section describes the MI
22148 mechanism to support such debugging scenarios.
22150 The key observation is that regardless of the structure of the
22151 target, MI can have a global list of threads, because most commands that
22152 accept the @samp{--thread} option do not need to know what process that
22153 thread belongs to. Therefore, it is not necessary to introduce
22154 neither additional @samp{--process} option, nor an notion of the
22155 current process in the MI interface. The only strictly new feature
22156 that is required is the ability to find how the threads are grouped
22159 To allow the user to discover such grouping, and to support arbitrary
22160 hierarchy of machines/cores/processes, MI introduces the concept of a
22161 @dfn{thread group}. Thread group is a collection of threads and other
22162 thread groups. A thread group always has a string identifier, a type,
22163 and may have additional attributes specific to the type. A new
22164 command, @code{-list-thread-groups}, returns the list of top-level
22165 thread groups, which correspond to processes that @value{GDBN} is
22166 debugging at the moment. By passing an identifier of a thread group
22167 to the @code{-list-thread-groups} command, it is possible to obtain
22168 the members of specific thread group.
22170 To allow the user to easily discover processes, and other objects, he
22171 wishes to debug, a concept of @dfn{available thread group} is
22172 introduced. Available thread group is an thread group that
22173 @value{GDBN} is not debugging, but that can be attached to, using the
22174 @code{-target-attach} command. The list of available top-level thread
22175 groups can be obtained using @samp{-list-thread-groups --available}.
22176 In general, the content of a thread group may be only retrieved only
22177 after attaching to that thread group.
22179 Thread groups are related to inferiors (@pxref{Inferiors and
22180 Programs}). Each inferior corresponds to a thread group of a special
22181 type @samp{process}, and some additional operations are permitted on
22182 such thread groups.
22184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22185 @node GDB/MI Command Syntax
22186 @section @sc{gdb/mi} Command Syntax
22189 * GDB/MI Input Syntax::
22190 * GDB/MI Output Syntax::
22193 @node GDB/MI Input Syntax
22194 @subsection @sc{gdb/mi} Input Syntax
22196 @cindex input syntax for @sc{gdb/mi}
22197 @cindex @sc{gdb/mi}, input syntax
22199 @item @var{command} @expansion{}
22200 @code{@var{cli-command} | @var{mi-command}}
22202 @item @var{cli-command} @expansion{}
22203 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22204 @var{cli-command} is any existing @value{GDBN} CLI command.
22206 @item @var{mi-command} @expansion{}
22207 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22208 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22210 @item @var{token} @expansion{}
22211 "any sequence of digits"
22213 @item @var{option} @expansion{}
22214 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22216 @item @var{parameter} @expansion{}
22217 @code{@var{non-blank-sequence} | @var{c-string}}
22219 @item @var{operation} @expansion{}
22220 @emph{any of the operations described in this chapter}
22222 @item @var{non-blank-sequence} @expansion{}
22223 @emph{anything, provided it doesn't contain special characters such as
22224 "-", @var{nl}, """ and of course " "}
22226 @item @var{c-string} @expansion{}
22227 @code{""" @var{seven-bit-iso-c-string-content} """}
22229 @item @var{nl} @expansion{}
22238 The CLI commands are still handled by the @sc{mi} interpreter; their
22239 output is described below.
22242 The @code{@var{token}}, when present, is passed back when the command
22246 Some @sc{mi} commands accept optional arguments as part of the parameter
22247 list. Each option is identified by a leading @samp{-} (dash) and may be
22248 followed by an optional argument parameter. Options occur first in the
22249 parameter list and can be delimited from normal parameters using
22250 @samp{--} (this is useful when some parameters begin with a dash).
22257 We want easy access to the existing CLI syntax (for debugging).
22260 We want it to be easy to spot a @sc{mi} operation.
22263 @node GDB/MI Output Syntax
22264 @subsection @sc{gdb/mi} Output Syntax
22266 @cindex output syntax of @sc{gdb/mi}
22267 @cindex @sc{gdb/mi}, output syntax
22268 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22269 followed, optionally, by a single result record. This result record
22270 is for the most recent command. The sequence of output records is
22271 terminated by @samp{(gdb)}.
22273 If an input command was prefixed with a @code{@var{token}} then the
22274 corresponding output for that command will also be prefixed by that same
22278 @item @var{output} @expansion{}
22279 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22281 @item @var{result-record} @expansion{}
22282 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22284 @item @var{out-of-band-record} @expansion{}
22285 @code{@var{async-record} | @var{stream-record}}
22287 @item @var{async-record} @expansion{}
22288 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22290 @item @var{exec-async-output} @expansion{}
22291 @code{[ @var{token} ] "*" @var{async-output}}
22293 @item @var{status-async-output} @expansion{}
22294 @code{[ @var{token} ] "+" @var{async-output}}
22296 @item @var{notify-async-output} @expansion{}
22297 @code{[ @var{token} ] "=" @var{async-output}}
22299 @item @var{async-output} @expansion{}
22300 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22302 @item @var{result-class} @expansion{}
22303 @code{"done" | "running" | "connected" | "error" | "exit"}
22305 @item @var{async-class} @expansion{}
22306 @code{"stopped" | @var{others}} (where @var{others} will be added
22307 depending on the needs---this is still in development).
22309 @item @var{result} @expansion{}
22310 @code{ @var{variable} "=" @var{value}}
22312 @item @var{variable} @expansion{}
22313 @code{ @var{string} }
22315 @item @var{value} @expansion{}
22316 @code{ @var{const} | @var{tuple} | @var{list} }
22318 @item @var{const} @expansion{}
22319 @code{@var{c-string}}
22321 @item @var{tuple} @expansion{}
22322 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22324 @item @var{list} @expansion{}
22325 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22326 @var{result} ( "," @var{result} )* "]" }
22328 @item @var{stream-record} @expansion{}
22329 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22331 @item @var{console-stream-output} @expansion{}
22332 @code{"~" @var{c-string}}
22334 @item @var{target-stream-output} @expansion{}
22335 @code{"@@" @var{c-string}}
22337 @item @var{log-stream-output} @expansion{}
22338 @code{"&" @var{c-string}}
22340 @item @var{nl} @expansion{}
22343 @item @var{token} @expansion{}
22344 @emph{any sequence of digits}.
22352 All output sequences end in a single line containing a period.
22355 The @code{@var{token}} is from the corresponding request. Note that
22356 for all async output, while the token is allowed by the grammar and
22357 may be output by future versions of @value{GDBN} for select async
22358 output messages, it is generally omitted. Frontends should treat
22359 all async output as reporting general changes in the state of the
22360 target and there should be no need to associate async output to any
22364 @cindex status output in @sc{gdb/mi}
22365 @var{status-async-output} contains on-going status information about the
22366 progress of a slow operation. It can be discarded. All status output is
22367 prefixed by @samp{+}.
22370 @cindex async output in @sc{gdb/mi}
22371 @var{exec-async-output} contains asynchronous state change on the target
22372 (stopped, started, disappeared). All async output is prefixed by
22376 @cindex notify output in @sc{gdb/mi}
22377 @var{notify-async-output} contains supplementary information that the
22378 client should handle (e.g., a new breakpoint information). All notify
22379 output is prefixed by @samp{=}.
22382 @cindex console output in @sc{gdb/mi}
22383 @var{console-stream-output} is output that should be displayed as is in the
22384 console. It is the textual response to a CLI command. All the console
22385 output is prefixed by @samp{~}.
22388 @cindex target output in @sc{gdb/mi}
22389 @var{target-stream-output} is the output produced by the target program.
22390 All the target output is prefixed by @samp{@@}.
22393 @cindex log output in @sc{gdb/mi}
22394 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22395 instance messages that should be displayed as part of an error log. All
22396 the log output is prefixed by @samp{&}.
22399 @cindex list output in @sc{gdb/mi}
22400 New @sc{gdb/mi} commands should only output @var{lists} containing
22406 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22407 details about the various output records.
22409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22410 @node GDB/MI Compatibility with CLI
22411 @section @sc{gdb/mi} Compatibility with CLI
22413 @cindex compatibility, @sc{gdb/mi} and CLI
22414 @cindex @sc{gdb/mi}, compatibility with CLI
22416 For the developers convenience CLI commands can be entered directly,
22417 but there may be some unexpected behaviour. For example, commands
22418 that query the user will behave as if the user replied yes, breakpoint
22419 command lists are not executed and some CLI commands, such as
22420 @code{if}, @code{when} and @code{define}, prompt for further input with
22421 @samp{>}, which is not valid MI output.
22423 This feature may be removed at some stage in the future and it is
22424 recommended that front ends use the @code{-interpreter-exec} command
22425 (@pxref{-interpreter-exec}).
22427 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22428 @node GDB/MI Development and Front Ends
22429 @section @sc{gdb/mi} Development and Front Ends
22430 @cindex @sc{gdb/mi} development
22432 The application which takes the MI output and presents the state of the
22433 program being debugged to the user is called a @dfn{front end}.
22435 Although @sc{gdb/mi} is still incomplete, it is currently being used
22436 by a variety of front ends to @value{GDBN}. This makes it difficult
22437 to introduce new functionality without breaking existing usage. This
22438 section tries to minimize the problems by describing how the protocol
22441 Some changes in MI need not break a carefully designed front end, and
22442 for these the MI version will remain unchanged. The following is a
22443 list of changes that may occur within one level, so front ends should
22444 parse MI output in a way that can handle them:
22448 New MI commands may be added.
22451 New fields may be added to the output of any MI command.
22454 The range of values for fields with specified values, e.g.,
22455 @code{in_scope} (@pxref{-var-update}) may be extended.
22457 @c The format of field's content e.g type prefix, may change so parse it
22458 @c at your own risk. Yes, in general?
22460 @c The order of fields may change? Shouldn't really matter but it might
22461 @c resolve inconsistencies.
22464 If the changes are likely to break front ends, the MI version level
22465 will be increased by one. This will allow the front end to parse the
22466 output according to the MI version. Apart from mi0, new versions of
22467 @value{GDBN} will not support old versions of MI and it will be the
22468 responsibility of the front end to work with the new one.
22470 @c Starting with mi3, add a new command -mi-version that prints the MI
22473 The best way to avoid unexpected changes in MI that might break your front
22474 end is to make your project known to @value{GDBN} developers and
22475 follow development on @email{gdb@@sourceware.org} and
22476 @email{gdb-patches@@sourceware.org}.
22477 @cindex mailing lists
22479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22480 @node GDB/MI Output Records
22481 @section @sc{gdb/mi} Output Records
22484 * GDB/MI Result Records::
22485 * GDB/MI Stream Records::
22486 * GDB/MI Async Records::
22487 * GDB/MI Frame Information::
22488 * GDB/MI Thread Information::
22491 @node GDB/MI Result Records
22492 @subsection @sc{gdb/mi} Result Records
22494 @cindex result records in @sc{gdb/mi}
22495 @cindex @sc{gdb/mi}, result records
22496 In addition to a number of out-of-band notifications, the response to a
22497 @sc{gdb/mi} command includes one of the following result indications:
22501 @item "^done" [ "," @var{results} ]
22502 The synchronous operation was successful, @code{@var{results}} are the return
22507 This result record is equivalent to @samp{^done}. Historically, it
22508 was output instead of @samp{^done} if the command has resumed the
22509 target. This behaviour is maintained for backward compatibility, but
22510 all frontends should treat @samp{^done} and @samp{^running}
22511 identically and rely on the @samp{*running} output record to determine
22512 which threads are resumed.
22516 @value{GDBN} has connected to a remote target.
22518 @item "^error" "," @var{c-string}
22520 The operation failed. The @code{@var{c-string}} contains the corresponding
22525 @value{GDBN} has terminated.
22529 @node GDB/MI Stream Records
22530 @subsection @sc{gdb/mi} Stream Records
22532 @cindex @sc{gdb/mi}, stream records
22533 @cindex stream records in @sc{gdb/mi}
22534 @value{GDBN} internally maintains a number of output streams: the console, the
22535 target, and the log. The output intended for each of these streams is
22536 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
22538 Each stream record begins with a unique @dfn{prefix character} which
22539 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
22540 Syntax}). In addition to the prefix, each stream record contains a
22541 @code{@var{string-output}}. This is either raw text (with an implicit new
22542 line) or a quoted C string (which does not contain an implicit newline).
22545 @item "~" @var{string-output}
22546 The console output stream contains text that should be displayed in the
22547 CLI console window. It contains the textual responses to CLI commands.
22549 @item "@@" @var{string-output}
22550 The target output stream contains any textual output from the running
22551 target. This is only present when GDB's event loop is truly
22552 asynchronous, which is currently only the case for remote targets.
22554 @item "&" @var{string-output}
22555 The log stream contains debugging messages being produced by @value{GDBN}'s
22559 @node GDB/MI Async Records
22560 @subsection @sc{gdb/mi} Async Records
22562 @cindex async records in @sc{gdb/mi}
22563 @cindex @sc{gdb/mi}, async records
22564 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
22565 additional changes that have occurred. Those changes can either be a
22566 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
22567 target activity (e.g., target stopped).
22569 The following is the list of possible async records:
22573 @item *running,thread-id="@var{thread}"
22574 The target is now running. The @var{thread} field tells which
22575 specific thread is now running, and can be @samp{all} if all threads
22576 are running. The frontend should assume that no interaction with a
22577 running thread is possible after this notification is produced.
22578 The frontend should not assume that this notification is output
22579 only once for any command. @value{GDBN} may emit this notification
22580 several times, either for different threads, because it cannot resume
22581 all threads together, or even for a single thread, if the thread must
22582 be stepped though some code before letting it run freely.
22584 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
22585 The target has stopped. The @var{reason} field can have one of the
22589 @item breakpoint-hit
22590 A breakpoint was reached.
22591 @item watchpoint-trigger
22592 A watchpoint was triggered.
22593 @item read-watchpoint-trigger
22594 A read watchpoint was triggered.
22595 @item access-watchpoint-trigger
22596 An access watchpoint was triggered.
22597 @item function-finished
22598 An -exec-finish or similar CLI command was accomplished.
22599 @item location-reached
22600 An -exec-until or similar CLI command was accomplished.
22601 @item watchpoint-scope
22602 A watchpoint has gone out of scope.
22603 @item end-stepping-range
22604 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
22605 similar CLI command was accomplished.
22606 @item exited-signalled
22607 The inferior exited because of a signal.
22609 The inferior exited.
22610 @item exited-normally
22611 The inferior exited normally.
22612 @item signal-received
22613 A signal was received by the inferior.
22616 The @var{id} field identifies the thread that directly caused the stop
22617 -- for example by hitting a breakpoint. Depending on whether all-stop
22618 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
22619 stop all threads, or only the thread that directly triggered the stop.
22620 If all threads are stopped, the @var{stopped} field will have the
22621 value of @code{"all"}. Otherwise, the value of the @var{stopped}
22622 field will be a list of thread identifiers. Presently, this list will
22623 always include a single thread, but frontend should be prepared to see
22624 several threads in the list. The @var{core} field reports the
22625 processor core on which the stop event has happened. This field may be absent
22626 if such information is not available.
22628 @item =thread-group-added,id="@var{id}"
22629 @itemx =thread-group-removed,id="@var{id}"
22630 A thread group was either added or removed. The @var{id} field
22631 contains the @value{GDBN} identifier of the thread group. When a thread
22632 group is added, it generally might not be associated with a running
22633 process. When a thread group is removed, its id becomes invalid and
22634 cannot be used in any way.
22636 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
22637 A thread group became associated with a running program,
22638 either because the program was just started or the thread group
22639 was attached to a program. The @var{id} field contains the
22640 @value{GDBN} identifier of the thread group. The @var{pid} field
22641 contains process identifier, specific to the operating system.
22643 @itemx =thread-group-exited,id="@var{id}"
22644 A thread group is no longer associated with a running program,
22645 either because the program has exited, or because it was detached
22646 from. The @var{id} field contains the @value{GDBN} identifier of the
22649 @item =thread-created,id="@var{id}",group-id="@var{gid}"
22650 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
22651 A thread either was created, or has exited. The @var{id} field
22652 contains the @value{GDBN} identifier of the thread. The @var{gid}
22653 field identifies the thread group this thread belongs to.
22655 @item =thread-selected,id="@var{id}"
22656 Informs that the selected thread was changed as result of the last
22657 command. This notification is not emitted as result of @code{-thread-select}
22658 command but is emitted whenever an MI command that is not documented
22659 to change the selected thread actually changes it. In particular,
22660 invoking, directly or indirectly (via user-defined command), the CLI
22661 @code{thread} command, will generate this notification.
22663 We suggest that in response to this notification, front ends
22664 highlight the selected thread and cause subsequent commands to apply to
22667 @item =library-loaded,...
22668 Reports that a new library file was loaded by the program. This
22669 notification has 4 fields---@var{id}, @var{target-name},
22670 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
22671 opaque identifier of the library. For remote debugging case,
22672 @var{target-name} and @var{host-name} fields give the name of the
22673 library file on the target, and on the host respectively. For native
22674 debugging, both those fields have the same value. The
22675 @var{symbols-loaded} field reports if the debug symbols for this
22676 library are loaded. The @var{thread-group} field, if present,
22677 specifies the id of the thread group in whose context the library was loaded.
22678 If the field is absent, it means the library was loaded in the context
22679 of all present thread groups.
22681 @item =library-unloaded,...
22682 Reports that a library was unloaded by the program. This notification
22683 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
22684 the same meaning as for the @code{=library-loaded} notification.
22685 The @var{thread-group} field, if present, specifies the id of the
22686 thread group in whose context the library was unloaded. If the field is
22687 absent, it means the library was unloaded in the context of all present
22692 @node GDB/MI Frame Information
22693 @subsection @sc{gdb/mi} Frame Information
22695 Response from many MI commands includes an information about stack
22696 frame. This information is a tuple that may have the following
22701 The level of the stack frame. The innermost frame has the level of
22702 zero. This field is always present.
22705 The name of the function corresponding to the frame. This field may
22706 be absent if @value{GDBN} is unable to determine the function name.
22709 The code address for the frame. This field is always present.
22712 The name of the source files that correspond to the frame's code
22713 address. This field may be absent.
22716 The source line corresponding to the frames' code address. This field
22720 The name of the binary file (either executable or shared library) the
22721 corresponds to the frame's code address. This field may be absent.
22725 @node GDB/MI Thread Information
22726 @subsection @sc{gdb/mi} Thread Information
22728 Whenever @value{GDBN} has to report an information about a thread, it
22729 uses a tuple with the following fields:
22733 The numeric id assigned to the thread by @value{GDBN}. This field is
22737 Target-specific string identifying the thread. This field is always present.
22740 Additional information about the thread provided by the target.
22741 It is supposed to be human-readable and not interpreted by the
22742 frontend. This field is optional.
22745 Either @samp{stopped} or @samp{running}, depending on whether the
22746 thread is presently running. This field is always present.
22749 The value of this field is an integer number of the processor core the
22750 thread was last seen on. This field is optional.
22754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22755 @node GDB/MI Simple Examples
22756 @section Simple Examples of @sc{gdb/mi} Interaction
22757 @cindex @sc{gdb/mi}, simple examples
22759 This subsection presents several simple examples of interaction using
22760 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
22761 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
22762 the output received from @sc{gdb/mi}.
22764 Note the line breaks shown in the examples are here only for
22765 readability, they don't appear in the real output.
22767 @subheading Setting a Breakpoint
22769 Setting a breakpoint generates synchronous output which contains detailed
22770 information of the breakpoint.
22773 -> -break-insert main
22774 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22775 enabled="y",addr="0x08048564",func="main",file="myprog.c",
22776 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
22780 @subheading Program Execution
22782 Program execution generates asynchronous records and MI gives the
22783 reason that execution stopped.
22789 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22790 frame=@{addr="0x08048564",func="main",
22791 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
22792 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
22797 <- *stopped,reason="exited-normally"
22801 @subheading Quitting @value{GDBN}
22803 Quitting @value{GDBN} just prints the result class @samp{^exit}.
22811 Please note that @samp{^exit} is printed immediately, but it might
22812 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
22813 performs necessary cleanups, including killing programs being debugged
22814 or disconnecting from debug hardware, so the frontend should wait till
22815 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
22816 fails to exit in reasonable time.
22818 @subheading A Bad Command
22820 Here's what happens if you pass a non-existent command:
22824 <- ^error,msg="Undefined MI command: rubbish"
22829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22830 @node GDB/MI Command Description Format
22831 @section @sc{gdb/mi} Command Description Format
22833 The remaining sections describe blocks of commands. Each block of
22834 commands is laid out in a fashion similar to this section.
22836 @subheading Motivation
22838 The motivation for this collection of commands.
22840 @subheading Introduction
22842 A brief introduction to this collection of commands as a whole.
22844 @subheading Commands
22846 For each command in the block, the following is described:
22848 @subsubheading Synopsis
22851 -command @var{args}@dots{}
22854 @subsubheading Result
22856 @subsubheading @value{GDBN} Command
22858 The corresponding @value{GDBN} CLI command(s), if any.
22860 @subsubheading Example
22862 Example(s) formatted for readability. Some of the described commands have
22863 not been implemented yet and these are labeled N.A.@: (not available).
22866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22867 @node GDB/MI Breakpoint Commands
22868 @section @sc{gdb/mi} Breakpoint Commands
22870 @cindex breakpoint commands for @sc{gdb/mi}
22871 @cindex @sc{gdb/mi}, breakpoint commands
22872 This section documents @sc{gdb/mi} commands for manipulating
22875 @subheading The @code{-break-after} Command
22876 @findex -break-after
22878 @subsubheading Synopsis
22881 -break-after @var{number} @var{count}
22884 The breakpoint number @var{number} is not in effect until it has been
22885 hit @var{count} times. To see how this is reflected in the output of
22886 the @samp{-break-list} command, see the description of the
22887 @samp{-break-list} command below.
22889 @subsubheading @value{GDBN} Command
22891 The corresponding @value{GDBN} command is @samp{ignore}.
22893 @subsubheading Example
22898 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22899 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22900 fullname="/home/foo/hello.c",line="5",times="0"@}
22907 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22914 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22915 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22916 line="5",times="0",ignore="3"@}]@}
22921 @subheading The @code{-break-catch} Command
22922 @findex -break-catch
22925 @subheading The @code{-break-commands} Command
22926 @findex -break-commands
22928 @subsubheading Synopsis
22931 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
22934 Specifies the CLI commands that should be executed when breakpoint
22935 @var{number} is hit. The parameters @var{command1} to @var{commandN}
22936 are the commands. If no command is specified, any previously-set
22937 commands are cleared. @xref{Break Commands}. Typical use of this
22938 functionality is tracing a program, that is, printing of values of
22939 some variables whenever breakpoint is hit and then continuing.
22941 @subsubheading @value{GDBN} Command
22943 The corresponding @value{GDBN} command is @samp{commands}.
22945 @subsubheading Example
22950 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22951 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22952 fullname="/home/foo/hello.c",line="5",times="0"@}
22954 -break-commands 1 "print v" "continue"
22959 @subheading The @code{-break-condition} Command
22960 @findex -break-condition
22962 @subsubheading Synopsis
22965 -break-condition @var{number} @var{expr}
22968 Breakpoint @var{number} will stop the program only if the condition in
22969 @var{expr} is true. The condition becomes part of the
22970 @samp{-break-list} output (see the description of the @samp{-break-list}
22973 @subsubheading @value{GDBN} Command
22975 The corresponding @value{GDBN} command is @samp{condition}.
22977 @subsubheading Example
22981 -break-condition 1 1
22985 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22986 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22987 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22988 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22989 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22990 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22991 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22992 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22993 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22994 line="5",cond="1",times="0",ignore="3"@}]@}
22998 @subheading The @code{-break-delete} Command
22999 @findex -break-delete
23001 @subsubheading Synopsis
23004 -break-delete ( @var{breakpoint} )+
23007 Delete the breakpoint(s) whose number(s) are specified in the argument
23008 list. This is obviously reflected in the breakpoint list.
23010 @subsubheading @value{GDBN} Command
23012 The corresponding @value{GDBN} command is @samp{delete}.
23014 @subsubheading Example
23022 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23033 @subheading The @code{-break-disable} Command
23034 @findex -break-disable
23036 @subsubheading Synopsis
23039 -break-disable ( @var{breakpoint} )+
23042 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23043 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23045 @subsubheading @value{GDBN} Command
23047 The corresponding @value{GDBN} command is @samp{disable}.
23049 @subsubheading Example
23057 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23064 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23065 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23066 line="5",times="0"@}]@}
23070 @subheading The @code{-break-enable} Command
23071 @findex -break-enable
23073 @subsubheading Synopsis
23076 -break-enable ( @var{breakpoint} )+
23079 Enable (previously disabled) @var{breakpoint}(s).
23081 @subsubheading @value{GDBN} Command
23083 The corresponding @value{GDBN} command is @samp{enable}.
23085 @subsubheading Example
23093 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23094 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23095 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23096 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23097 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23098 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23099 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23100 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23101 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23102 line="5",times="0"@}]@}
23106 @subheading The @code{-break-info} Command
23107 @findex -break-info
23109 @subsubheading Synopsis
23112 -break-info @var{breakpoint}
23116 Get information about a single breakpoint.
23118 @subsubheading @value{GDBN} Command
23120 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23122 @subsubheading Example
23125 @subheading The @code{-break-insert} Command
23126 @findex -break-insert
23128 @subsubheading Synopsis
23131 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23132 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23133 [ -p @var{thread} ] [ @var{location} ]
23137 If specified, @var{location}, can be one of:
23144 @item filename:linenum
23145 @item filename:function
23149 The possible optional parameters of this command are:
23153 Insert a temporary breakpoint.
23155 Insert a hardware breakpoint.
23156 @item -c @var{condition}
23157 Make the breakpoint conditional on @var{condition}.
23158 @item -i @var{ignore-count}
23159 Initialize the @var{ignore-count}.
23161 If @var{location} cannot be parsed (for example if it
23162 refers to unknown files or functions), create a pending
23163 breakpoint. Without this flag, @value{GDBN} will report
23164 an error, and won't create a breakpoint, if @var{location}
23167 Create a disabled breakpoint.
23169 Create a tracepoint. @xref{Tracepoints}. When this parameter
23170 is used together with @samp{-h}, a fast tracepoint is created.
23173 @subsubheading Result
23175 The result is in the form:
23178 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23179 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23180 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23181 times="@var{times}"@}
23185 where @var{number} is the @value{GDBN} number for this breakpoint,
23186 @var{funcname} is the name of the function where the breakpoint was
23187 inserted, @var{filename} is the name of the source file which contains
23188 this function, @var{lineno} is the source line number within that file
23189 and @var{times} the number of times that the breakpoint has been hit
23190 (always 0 for -break-insert but may be greater for -break-info or -break-list
23191 which use the same output).
23193 Note: this format is open to change.
23194 @c An out-of-band breakpoint instead of part of the result?
23196 @subsubheading @value{GDBN} Command
23198 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23199 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23201 @subsubheading Example
23206 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23207 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23209 -break-insert -t foo
23210 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23211 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23214 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23215 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23216 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23217 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23218 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23219 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23220 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23221 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23222 addr="0x0001072c", func="main",file="recursive2.c",
23223 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23224 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23225 addr="0x00010774",func="foo",file="recursive2.c",
23226 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23228 -break-insert -r foo.*
23229 ~int foo(int, int);
23230 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23231 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23235 @subheading The @code{-break-list} Command
23236 @findex -break-list
23238 @subsubheading Synopsis
23244 Displays the list of inserted breakpoints, showing the following fields:
23248 number of the breakpoint
23250 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23252 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23255 is the breakpoint enabled or no: @samp{y} or @samp{n}
23257 memory location at which the breakpoint is set
23259 logical location of the breakpoint, expressed by function name, file
23262 number of times the breakpoint has been hit
23265 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23266 @code{body} field is an empty list.
23268 @subsubheading @value{GDBN} Command
23270 The corresponding @value{GDBN} command is @samp{info break}.
23272 @subsubheading Example
23277 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23278 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23279 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23280 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23281 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23282 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23283 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23284 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23285 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23286 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23287 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23288 line="13",times="0"@}]@}
23292 Here's an example of the result when there are no breakpoints:
23297 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23298 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23299 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23300 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23301 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23302 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23303 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23308 @subheading The @code{-break-passcount} Command
23309 @findex -break-passcount
23311 @subsubheading Synopsis
23314 -break-passcount @var{tracepoint-number} @var{passcount}
23317 Set the passcount for tracepoint @var{tracepoint-number} to
23318 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23319 is not a tracepoint, error is emitted. This corresponds to CLI
23320 command @samp{passcount}.
23322 @subheading The @code{-break-watch} Command
23323 @findex -break-watch
23325 @subsubheading Synopsis
23328 -break-watch [ -a | -r ]
23331 Create a watchpoint. With the @samp{-a} option it will create an
23332 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23333 read from or on a write to the memory location. With the @samp{-r}
23334 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23335 trigger only when the memory location is accessed for reading. Without
23336 either of the options, the watchpoint created is a regular watchpoint,
23337 i.e., it will trigger when the memory location is accessed for writing.
23338 @xref{Set Watchpoints, , Setting Watchpoints}.
23340 Note that @samp{-break-list} will report a single list of watchpoints and
23341 breakpoints inserted.
23343 @subsubheading @value{GDBN} Command
23345 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23348 @subsubheading Example
23350 Setting a watchpoint on a variable in the @code{main} function:
23355 ^done,wpt=@{number="2",exp="x"@}
23360 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23361 value=@{old="-268439212",new="55"@},
23362 frame=@{func="main",args=[],file="recursive2.c",
23363 fullname="/home/foo/bar/recursive2.c",line="5"@}
23367 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23368 the program execution twice: first for the variable changing value, then
23369 for the watchpoint going out of scope.
23374 ^done,wpt=@{number="5",exp="C"@}
23379 *stopped,reason="watchpoint-trigger",
23380 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23381 frame=@{func="callee4",args=[],
23382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23388 *stopped,reason="watchpoint-scope",wpnum="5",
23389 frame=@{func="callee3",args=[@{name="strarg",
23390 value="0x11940 \"A string argument.\""@}],
23391 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23392 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23396 Listing breakpoints and watchpoints, at different points in the program
23397 execution. Note that once the watchpoint goes out of scope, it is
23403 ^done,wpt=@{number="2",exp="C"@}
23406 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23407 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23408 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23409 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23410 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23411 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23412 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23413 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23414 addr="0x00010734",func="callee4",
23415 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23416 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23417 bkpt=@{number="2",type="watchpoint",disp="keep",
23418 enabled="y",addr="",what="C",times="0"@}]@}
23423 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
23424 value=@{old="-276895068",new="3"@},
23425 frame=@{func="callee4",args=[],
23426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23430 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23431 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23432 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23433 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23434 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23435 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23436 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23437 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23438 addr="0x00010734",func="callee4",
23439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23440 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
23441 bkpt=@{number="2",type="watchpoint",disp="keep",
23442 enabled="y",addr="",what="C",times="-5"@}]@}
23446 ^done,reason="watchpoint-scope",wpnum="2",
23447 frame=@{func="callee3",args=[@{name="strarg",
23448 value="0x11940 \"A string argument.\""@}],
23449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23450 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23453 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23454 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23455 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23456 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23457 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23458 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23459 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23460 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23461 addr="0x00010734",func="callee4",
23462 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23463 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
23468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23469 @node GDB/MI Program Context
23470 @section @sc{gdb/mi} Program Context
23472 @subheading The @code{-exec-arguments} Command
23473 @findex -exec-arguments
23476 @subsubheading Synopsis
23479 -exec-arguments @var{args}
23482 Set the inferior program arguments, to be used in the next
23485 @subsubheading @value{GDBN} Command
23487 The corresponding @value{GDBN} command is @samp{set args}.
23489 @subsubheading Example
23493 -exec-arguments -v word
23500 @subheading The @code{-exec-show-arguments} Command
23501 @findex -exec-show-arguments
23503 @subsubheading Synopsis
23506 -exec-show-arguments
23509 Print the arguments of the program.
23511 @subsubheading @value{GDBN} Command
23513 The corresponding @value{GDBN} command is @samp{show args}.
23515 @subsubheading Example
23520 @subheading The @code{-environment-cd} Command
23521 @findex -environment-cd
23523 @subsubheading Synopsis
23526 -environment-cd @var{pathdir}
23529 Set @value{GDBN}'s working directory.
23531 @subsubheading @value{GDBN} Command
23533 The corresponding @value{GDBN} command is @samp{cd}.
23535 @subsubheading Example
23539 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23545 @subheading The @code{-environment-directory} Command
23546 @findex -environment-directory
23548 @subsubheading Synopsis
23551 -environment-directory [ -r ] [ @var{pathdir} ]+
23554 Add directories @var{pathdir} to beginning of search path for source files.
23555 If the @samp{-r} option is used, the search path is reset to the default
23556 search path. If directories @var{pathdir} are supplied in addition to the
23557 @samp{-r} option, the search path is first reset and then addition
23559 Multiple directories may be specified, separated by blanks. Specifying
23560 multiple directories in a single command
23561 results in the directories added to the beginning of the
23562 search path in the same order they were presented in the command.
23563 If blanks are needed as
23564 part of a directory name, double-quotes should be used around
23565 the name. In the command output, the path will show up separated
23566 by the system directory-separator character. The directory-separator
23567 character must not be used
23568 in any directory name.
23569 If no directories are specified, the current search path is displayed.
23571 @subsubheading @value{GDBN} Command
23573 The corresponding @value{GDBN} command is @samp{dir}.
23575 @subsubheading Example
23579 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23580 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23582 -environment-directory ""
23583 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23585 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
23586 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
23588 -environment-directory -r
23589 ^done,source-path="$cdir:$cwd"
23594 @subheading The @code{-environment-path} Command
23595 @findex -environment-path
23597 @subsubheading Synopsis
23600 -environment-path [ -r ] [ @var{pathdir} ]+
23603 Add directories @var{pathdir} to beginning of search path for object files.
23604 If the @samp{-r} option is used, the search path is reset to the original
23605 search path that existed at gdb start-up. If directories @var{pathdir} are
23606 supplied in addition to the
23607 @samp{-r} option, the search path is first reset and then addition
23609 Multiple directories may be specified, separated by blanks. Specifying
23610 multiple directories in a single command
23611 results in the directories added to the beginning of the
23612 search path in the same order they were presented in the command.
23613 If blanks are needed as
23614 part of a directory name, double-quotes should be used around
23615 the name. In the command output, the path will show up separated
23616 by the system directory-separator character. The directory-separator
23617 character must not be used
23618 in any directory name.
23619 If no directories are specified, the current path is displayed.
23622 @subsubheading @value{GDBN} Command
23624 The corresponding @value{GDBN} command is @samp{path}.
23626 @subsubheading Example
23631 ^done,path="/usr/bin"
23633 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
23634 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
23636 -environment-path -r /usr/local/bin
23637 ^done,path="/usr/local/bin:/usr/bin"
23642 @subheading The @code{-environment-pwd} Command
23643 @findex -environment-pwd
23645 @subsubheading Synopsis
23651 Show the current working directory.
23653 @subsubheading @value{GDBN} Command
23655 The corresponding @value{GDBN} command is @samp{pwd}.
23657 @subsubheading Example
23662 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
23666 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23667 @node GDB/MI Thread Commands
23668 @section @sc{gdb/mi} Thread Commands
23671 @subheading The @code{-thread-info} Command
23672 @findex -thread-info
23674 @subsubheading Synopsis
23677 -thread-info [ @var{thread-id} ]
23680 Reports information about either a specific thread, if
23681 the @var{thread-id} parameter is present, or about all
23682 threads. When printing information about all threads,
23683 also reports the current thread.
23685 @subsubheading @value{GDBN} Command
23687 The @samp{info thread} command prints the same information
23690 @subsubheading Example
23695 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23696 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23697 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23698 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23699 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
23700 current-thread-id="1"
23704 The @samp{state} field may have the following values:
23708 The thread is stopped. Frame information is available for stopped
23712 The thread is running. There's no frame information for running
23717 @subheading The @code{-thread-list-ids} Command
23718 @findex -thread-list-ids
23720 @subsubheading Synopsis
23726 Produces a list of the currently known @value{GDBN} thread ids. At the
23727 end of the list it also prints the total number of such threads.
23729 This command is retained for historical reasons, the
23730 @code{-thread-info} command should be used instead.
23732 @subsubheading @value{GDBN} Command
23734 Part of @samp{info threads} supplies the same information.
23736 @subsubheading Example
23741 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23742 current-thread-id="1",number-of-threads="3"
23747 @subheading The @code{-thread-select} Command
23748 @findex -thread-select
23750 @subsubheading Synopsis
23753 -thread-select @var{threadnum}
23756 Make @var{threadnum} the current thread. It prints the number of the new
23757 current thread, and the topmost frame for that thread.
23759 This command is deprecated in favor of explicitly using the
23760 @samp{--thread} option to each command.
23762 @subsubheading @value{GDBN} Command
23764 The corresponding @value{GDBN} command is @samp{thread}.
23766 @subsubheading Example
23773 *stopped,reason="end-stepping-range",thread-id="2",line="187",
23774 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
23778 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23779 number-of-threads="3"
23782 ^done,new-thread-id="3",
23783 frame=@{level="0",func="vprintf",
23784 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
23785 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
23789 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23790 @node GDB/MI Program Execution
23791 @section @sc{gdb/mi} Program Execution
23793 These are the asynchronous commands which generate the out-of-band
23794 record @samp{*stopped}. Currently @value{GDBN} only really executes
23795 asynchronously with remote targets and this interaction is mimicked in
23798 @subheading The @code{-exec-continue} Command
23799 @findex -exec-continue
23801 @subsubheading Synopsis
23804 -exec-continue [--reverse] [--all|--thread-group N]
23807 Resumes the execution of the inferior program, which will continue
23808 to execute until it reaches a debugger stop event. If the
23809 @samp{--reverse} option is specified, execution resumes in reverse until
23810 it reaches a stop event. Stop events may include
23813 breakpoints or watchpoints
23815 signals or exceptions
23817 the end of the process (or its beginning under @samp{--reverse})
23819 the end or beginning of a replay log if one is being used.
23821 In all-stop mode (@pxref{All-Stop
23822 Mode}), may resume only one thread, or all threads, depending on the
23823 value of the @samp{scheduler-locking} variable. If @samp{--all} is
23824 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
23825 ignored in all-stop mode. If the @samp{--thread-group} options is
23826 specified, then all threads in that thread group are resumed.
23828 @subsubheading @value{GDBN} Command
23830 The corresponding @value{GDBN} corresponding is @samp{continue}.
23832 @subsubheading Example
23839 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
23840 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
23846 @subheading The @code{-exec-finish} Command
23847 @findex -exec-finish
23849 @subsubheading Synopsis
23852 -exec-finish [--reverse]
23855 Resumes the execution of the inferior program until the current
23856 function is exited. Displays the results returned by the function.
23857 If the @samp{--reverse} option is specified, resumes the reverse
23858 execution of the inferior program until the point where current
23859 function was called.
23861 @subsubheading @value{GDBN} Command
23863 The corresponding @value{GDBN} command is @samp{finish}.
23865 @subsubheading Example
23867 Function returning @code{void}.
23874 *stopped,reason="function-finished",frame=@{func="main",args=[],
23875 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
23879 Function returning other than @code{void}. The name of the internal
23880 @value{GDBN} variable storing the result is printed, together with the
23887 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
23888 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
23889 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23890 gdb-result-var="$1",return-value="0"
23895 @subheading The @code{-exec-interrupt} Command
23896 @findex -exec-interrupt
23898 @subsubheading Synopsis
23901 -exec-interrupt [--all|--thread-group N]
23904 Interrupts the background execution of the target. Note how the token
23905 associated with the stop message is the one for the execution command
23906 that has been interrupted. The token for the interrupt itself only
23907 appears in the @samp{^done} output. If the user is trying to
23908 interrupt a non-running program, an error message will be printed.
23910 Note that when asynchronous execution is enabled, this command is
23911 asynchronous just like other execution commands. That is, first the
23912 @samp{^done} response will be printed, and the target stop will be
23913 reported after that using the @samp{*stopped} notification.
23915 In non-stop mode, only the context thread is interrupted by default.
23916 All threads (in all inferiors) will be interrupted if the
23917 @samp{--all} option is specified. If the @samp{--thread-group}
23918 option is specified, all threads in that group will be interrupted.
23920 @subsubheading @value{GDBN} Command
23922 The corresponding @value{GDBN} command is @samp{interrupt}.
23924 @subsubheading Example
23935 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
23936 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
23937 fullname="/home/foo/bar/try.c",line="13"@}
23942 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
23946 @subheading The @code{-exec-jump} Command
23949 @subsubheading Synopsis
23952 -exec-jump @var{location}
23955 Resumes execution of the inferior program at the location specified by
23956 parameter. @xref{Specify Location}, for a description of the
23957 different forms of @var{location}.
23959 @subsubheading @value{GDBN} Command
23961 The corresponding @value{GDBN} command is @samp{jump}.
23963 @subsubheading Example
23966 -exec-jump foo.c:10
23967 *running,thread-id="all"
23972 @subheading The @code{-exec-next} Command
23975 @subsubheading Synopsis
23978 -exec-next [--reverse]
23981 Resumes execution of the inferior program, stopping when the beginning
23982 of the next source line is reached.
23984 If the @samp{--reverse} option is specified, resumes reverse execution
23985 of the inferior program, stopping at the beginning of the previous
23986 source line. If you issue this command on the first line of a
23987 function, it will take you back to the caller of that function, to the
23988 source line where the function was called.
23991 @subsubheading @value{GDBN} Command
23993 The corresponding @value{GDBN} command is @samp{next}.
23995 @subsubheading Example
24001 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24006 @subheading The @code{-exec-next-instruction} Command
24007 @findex -exec-next-instruction
24009 @subsubheading Synopsis
24012 -exec-next-instruction [--reverse]
24015 Executes one machine instruction. If the instruction is a function
24016 call, continues until the function returns. If the program stops at an
24017 instruction in the middle of a source line, the address will be
24020 If the @samp{--reverse} option is specified, resumes reverse execution
24021 of the inferior program, stopping at the previous instruction. If the
24022 previously executed instruction was a return from another function,
24023 it will continue to execute in reverse until the call to that function
24024 (from the current stack frame) is reached.
24026 @subsubheading @value{GDBN} Command
24028 The corresponding @value{GDBN} command is @samp{nexti}.
24030 @subsubheading Example
24034 -exec-next-instruction
24038 *stopped,reason="end-stepping-range",
24039 addr="0x000100d4",line="5",file="hello.c"
24044 @subheading The @code{-exec-return} Command
24045 @findex -exec-return
24047 @subsubheading Synopsis
24053 Makes current function return immediately. Doesn't execute the inferior.
24054 Displays the new current frame.
24056 @subsubheading @value{GDBN} Command
24058 The corresponding @value{GDBN} command is @samp{return}.
24060 @subsubheading Example
24064 200-break-insert callee4
24065 200^done,bkpt=@{number="1",addr="0x00010734",
24066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24071 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24072 frame=@{func="callee4",args=[],
24073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24074 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24080 111^done,frame=@{level="0",func="callee3",
24081 args=[@{name="strarg",
24082 value="0x11940 \"A string argument.\""@}],
24083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24084 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24089 @subheading The @code{-exec-run} Command
24092 @subsubheading Synopsis
24095 -exec-run [--all | --thread-group N]
24098 Starts execution of the inferior from the beginning. The inferior
24099 executes until either a breakpoint is encountered or the program
24100 exits. In the latter case the output will include an exit code, if
24101 the program has exited exceptionally.
24103 When no option is specified, the current inferior is started. If the
24104 @samp{--thread-group} option is specified, it should refer to a thread
24105 group of type @samp{process}, and that thread group will be started.
24106 If the @samp{--all} option is specified, then all inferiors will be started.
24108 @subsubheading @value{GDBN} Command
24110 The corresponding @value{GDBN} command is @samp{run}.
24112 @subsubheading Examples
24117 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24122 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24123 frame=@{func="main",args=[],file="recursive2.c",
24124 fullname="/home/foo/bar/recursive2.c",line="4"@}
24129 Program exited normally:
24137 *stopped,reason="exited-normally"
24142 Program exited exceptionally:
24150 *stopped,reason="exited",exit-code="01"
24154 Another way the program can terminate is if it receives a signal such as
24155 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24159 *stopped,reason="exited-signalled",signal-name="SIGINT",
24160 signal-meaning="Interrupt"
24164 @c @subheading -exec-signal
24167 @subheading The @code{-exec-step} Command
24170 @subsubheading Synopsis
24173 -exec-step [--reverse]
24176 Resumes execution of the inferior program, stopping when the beginning
24177 of the next source line is reached, if the next source line is not a
24178 function call. If it is, stop at the first instruction of the called
24179 function. If the @samp{--reverse} option is specified, resumes reverse
24180 execution of the inferior program, stopping at the beginning of the
24181 previously executed source line.
24183 @subsubheading @value{GDBN} Command
24185 The corresponding @value{GDBN} command is @samp{step}.
24187 @subsubheading Example
24189 Stepping into a function:
24195 *stopped,reason="end-stepping-range",
24196 frame=@{func="foo",args=[@{name="a",value="10"@},
24197 @{name="b",value="0"@}],file="recursive2.c",
24198 fullname="/home/foo/bar/recursive2.c",line="11"@}
24208 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24213 @subheading The @code{-exec-step-instruction} Command
24214 @findex -exec-step-instruction
24216 @subsubheading Synopsis
24219 -exec-step-instruction [--reverse]
24222 Resumes the inferior which executes one machine instruction. If the
24223 @samp{--reverse} option is specified, resumes reverse execution of the
24224 inferior program, stopping at the previously executed instruction.
24225 The output, once @value{GDBN} has stopped, will vary depending on
24226 whether we have stopped in the middle of a source line or not. In the
24227 former case, the address at which the program stopped will be printed
24230 @subsubheading @value{GDBN} Command
24232 The corresponding @value{GDBN} command is @samp{stepi}.
24234 @subsubheading Example
24238 -exec-step-instruction
24242 *stopped,reason="end-stepping-range",
24243 frame=@{func="foo",args=[],file="try.c",
24244 fullname="/home/foo/bar/try.c",line="10"@}
24246 -exec-step-instruction
24250 *stopped,reason="end-stepping-range",
24251 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24252 fullname="/home/foo/bar/try.c",line="10"@}
24257 @subheading The @code{-exec-until} Command
24258 @findex -exec-until
24260 @subsubheading Synopsis
24263 -exec-until [ @var{location} ]
24266 Executes the inferior until the @var{location} specified in the
24267 argument is reached. If there is no argument, the inferior executes
24268 until a source line greater than the current one is reached. The
24269 reason for stopping in this case will be @samp{location-reached}.
24271 @subsubheading @value{GDBN} Command
24273 The corresponding @value{GDBN} command is @samp{until}.
24275 @subsubheading Example
24279 -exec-until recursive2.c:6
24283 *stopped,reason="location-reached",frame=@{func="main",args=[],
24284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24289 @subheading -file-clear
24290 Is this going away????
24293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24294 @node GDB/MI Stack Manipulation
24295 @section @sc{gdb/mi} Stack Manipulation Commands
24298 @subheading The @code{-stack-info-frame} Command
24299 @findex -stack-info-frame
24301 @subsubheading Synopsis
24307 Get info on the selected frame.
24309 @subsubheading @value{GDBN} Command
24311 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24312 (without arguments).
24314 @subsubheading Example
24319 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24320 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24321 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24325 @subheading The @code{-stack-info-depth} Command
24326 @findex -stack-info-depth
24328 @subsubheading Synopsis
24331 -stack-info-depth [ @var{max-depth} ]
24334 Return the depth of the stack. If the integer argument @var{max-depth}
24335 is specified, do not count beyond @var{max-depth} frames.
24337 @subsubheading @value{GDBN} Command
24339 There's no equivalent @value{GDBN} command.
24341 @subsubheading Example
24343 For a stack with frame levels 0 through 11:
24350 -stack-info-depth 4
24353 -stack-info-depth 12
24356 -stack-info-depth 11
24359 -stack-info-depth 13
24364 @subheading The @code{-stack-list-arguments} Command
24365 @findex -stack-list-arguments
24367 @subsubheading Synopsis
24370 -stack-list-arguments @var{print-values}
24371 [ @var{low-frame} @var{high-frame} ]
24374 Display a list of the arguments for the frames between @var{low-frame}
24375 and @var{high-frame} (inclusive). If @var{low-frame} and
24376 @var{high-frame} are not provided, list the arguments for the whole
24377 call stack. If the two arguments are equal, show the single frame
24378 at the corresponding level. It is an error if @var{low-frame} is
24379 larger than the actual number of frames. On the other hand,
24380 @var{high-frame} may be larger than the actual number of frames, in
24381 which case only existing frames will be returned.
24383 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24384 the variables; if it is 1 or @code{--all-values}, print also their
24385 values; and if it is 2 or @code{--simple-values}, print the name,
24386 type and value for simple data types, and the name and type for arrays,
24387 structures and unions.
24389 Use of this command to obtain arguments in a single frame is
24390 deprecated in favor of the @samp{-stack-list-variables} command.
24392 @subsubheading @value{GDBN} Command
24394 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24395 @samp{gdb_get_args} command which partially overlaps with the
24396 functionality of @samp{-stack-list-arguments}.
24398 @subsubheading Example
24405 frame=@{level="0",addr="0x00010734",func="callee4",
24406 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24407 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24408 frame=@{level="1",addr="0x0001076c",func="callee3",
24409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24411 frame=@{level="2",addr="0x0001078c",func="callee2",
24412 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24413 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24414 frame=@{level="3",addr="0x000107b4",func="callee1",
24415 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24416 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24417 frame=@{level="4",addr="0x000107e0",func="main",
24418 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24419 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24421 -stack-list-arguments 0
24424 frame=@{level="0",args=[]@},
24425 frame=@{level="1",args=[name="strarg"]@},
24426 frame=@{level="2",args=[name="intarg",name="strarg"]@},
24427 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
24428 frame=@{level="4",args=[]@}]
24430 -stack-list-arguments 1
24433 frame=@{level="0",args=[]@},
24435 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24436 frame=@{level="2",args=[
24437 @{name="intarg",value="2"@},
24438 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24439 @{frame=@{level="3",args=[
24440 @{name="intarg",value="2"@},
24441 @{name="strarg",value="0x11940 \"A string argument.\""@},
24442 @{name="fltarg",value="3.5"@}]@},
24443 frame=@{level="4",args=[]@}]
24445 -stack-list-arguments 0 2 2
24446 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
24448 -stack-list-arguments 1 2 2
24449 ^done,stack-args=[frame=@{level="2",
24450 args=[@{name="intarg",value="2"@},
24451 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
24455 @c @subheading -stack-list-exception-handlers
24458 @subheading The @code{-stack-list-frames} Command
24459 @findex -stack-list-frames
24461 @subsubheading Synopsis
24464 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
24467 List the frames currently on the stack. For each frame it displays the
24472 The frame number, 0 being the topmost frame, i.e., the innermost function.
24474 The @code{$pc} value for that frame.
24478 File name of the source file where the function lives.
24480 Line number corresponding to the @code{$pc}.
24483 If invoked without arguments, this command prints a backtrace for the
24484 whole stack. If given two integer arguments, it shows the frames whose
24485 levels are between the two arguments (inclusive). If the two arguments
24486 are equal, it shows the single frame at the corresponding level. It is
24487 an error if @var{low-frame} is larger than the actual number of
24488 frames. On the other hand, @var{high-frame} may be larger than the
24489 actual number of frames, in which case only existing frames will be returned.
24491 @subsubheading @value{GDBN} Command
24493 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
24495 @subsubheading Example
24497 Full stack backtrace:
24503 [frame=@{level="0",addr="0x0001076c",func="foo",
24504 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
24505 frame=@{level="1",addr="0x000107a4",func="foo",
24506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24507 frame=@{level="2",addr="0x000107a4",func="foo",
24508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24509 frame=@{level="3",addr="0x000107a4",func="foo",
24510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24511 frame=@{level="4",addr="0x000107a4",func="foo",
24512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24513 frame=@{level="5",addr="0x000107a4",func="foo",
24514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24515 frame=@{level="6",addr="0x000107a4",func="foo",
24516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24517 frame=@{level="7",addr="0x000107a4",func="foo",
24518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24519 frame=@{level="8",addr="0x000107a4",func="foo",
24520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24521 frame=@{level="9",addr="0x000107a4",func="foo",
24522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24523 frame=@{level="10",addr="0x000107a4",func="foo",
24524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24525 frame=@{level="11",addr="0x00010738",func="main",
24526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
24530 Show frames between @var{low_frame} and @var{high_frame}:
24534 -stack-list-frames 3 5
24536 [frame=@{level="3",addr="0x000107a4",func="foo",
24537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24538 frame=@{level="4",addr="0x000107a4",func="foo",
24539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24540 frame=@{level="5",addr="0x000107a4",func="foo",
24541 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24545 Show a single frame:
24549 -stack-list-frames 3 3
24551 [frame=@{level="3",addr="0x000107a4",func="foo",
24552 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24557 @subheading The @code{-stack-list-locals} Command
24558 @findex -stack-list-locals
24560 @subsubheading Synopsis
24563 -stack-list-locals @var{print-values}
24566 Display the local variable names for the selected frame. If
24567 @var{print-values} is 0 or @code{--no-values}, print only the names of
24568 the variables; if it is 1 or @code{--all-values}, print also their
24569 values; and if it is 2 or @code{--simple-values}, print the name,
24570 type and value for simple data types, and the name and type for arrays,
24571 structures and unions. In this last case, a frontend can immediately
24572 display the value of simple data types and create variable objects for
24573 other data types when the user wishes to explore their values in
24576 This command is deprecated in favor of the
24577 @samp{-stack-list-variables} command.
24579 @subsubheading @value{GDBN} Command
24581 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
24583 @subsubheading Example
24587 -stack-list-locals 0
24588 ^done,locals=[name="A",name="B",name="C"]
24590 -stack-list-locals --all-values
24591 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
24592 @{name="C",value="@{1, 2, 3@}"@}]
24593 -stack-list-locals --simple-values
24594 ^done,locals=[@{name="A",type="int",value="1"@},
24595 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
24599 @subheading The @code{-stack-list-variables} Command
24600 @findex -stack-list-variables
24602 @subsubheading Synopsis
24605 -stack-list-variables @var{print-values}
24608 Display the names of local variables and function arguments for the selected frame. If
24609 @var{print-values} is 0 or @code{--no-values}, print only the names of
24610 the variables; if it is 1 or @code{--all-values}, print also their
24611 values; and if it is 2 or @code{--simple-values}, print the name,
24612 type and value for simple data types, and the name and type for arrays,
24613 structures and unions.
24615 @subsubheading Example
24619 -stack-list-variables --thread 1 --frame 0 --all-values
24620 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
24625 @subheading The @code{-stack-select-frame} Command
24626 @findex -stack-select-frame
24628 @subsubheading Synopsis
24631 -stack-select-frame @var{framenum}
24634 Change the selected frame. Select a different frame @var{framenum} on
24637 This command in deprecated in favor of passing the @samp{--frame}
24638 option to every command.
24640 @subsubheading @value{GDBN} Command
24642 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
24643 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
24645 @subsubheading Example
24649 -stack-select-frame 2
24654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24655 @node GDB/MI Variable Objects
24656 @section @sc{gdb/mi} Variable Objects
24660 @subheading Motivation for Variable Objects in @sc{gdb/mi}
24662 For the implementation of a variable debugger window (locals, watched
24663 expressions, etc.), we are proposing the adaptation of the existing code
24664 used by @code{Insight}.
24666 The two main reasons for that are:
24670 It has been proven in practice (it is already on its second generation).
24673 It will shorten development time (needless to say how important it is
24677 The original interface was designed to be used by Tcl code, so it was
24678 slightly changed so it could be used through @sc{gdb/mi}. This section
24679 describes the @sc{gdb/mi} operations that will be available and gives some
24680 hints about their use.
24682 @emph{Note}: In addition to the set of operations described here, we
24683 expect the @sc{gui} implementation of a variable window to require, at
24684 least, the following operations:
24687 @item @code{-gdb-show} @code{output-radix}
24688 @item @code{-stack-list-arguments}
24689 @item @code{-stack-list-locals}
24690 @item @code{-stack-select-frame}
24695 @subheading Introduction to Variable Objects
24697 @cindex variable objects in @sc{gdb/mi}
24699 Variable objects are "object-oriented" MI interface for examining and
24700 changing values of expressions. Unlike some other MI interfaces that
24701 work with expressions, variable objects are specifically designed for
24702 simple and efficient presentation in the frontend. A variable object
24703 is identified by string name. When a variable object is created, the
24704 frontend specifies the expression for that variable object. The
24705 expression can be a simple variable, or it can be an arbitrary complex
24706 expression, and can even involve CPU registers. After creating a
24707 variable object, the frontend can invoke other variable object
24708 operations---for example to obtain or change the value of a variable
24709 object, or to change display format.
24711 Variable objects have hierarchical tree structure. Any variable object
24712 that corresponds to a composite type, such as structure in C, has
24713 a number of child variable objects, for example corresponding to each
24714 element of a structure. A child variable object can itself have
24715 children, recursively. Recursion ends when we reach
24716 leaf variable objects, which always have built-in types. Child variable
24717 objects are created only by explicit request, so if a frontend
24718 is not interested in the children of a particular variable object, no
24719 child will be created.
24721 For a leaf variable object it is possible to obtain its value as a
24722 string, or set the value from a string. String value can be also
24723 obtained for a non-leaf variable object, but it's generally a string
24724 that only indicates the type of the object, and does not list its
24725 contents. Assignment to a non-leaf variable object is not allowed.
24727 A frontend does not need to read the values of all variable objects each time
24728 the program stops. Instead, MI provides an update command that lists all
24729 variable objects whose values has changed since the last update
24730 operation. This considerably reduces the amount of data that must
24731 be transferred to the frontend. As noted above, children variable
24732 objects are created on demand, and only leaf variable objects have a
24733 real value. As result, gdb will read target memory only for leaf
24734 variables that frontend has created.
24736 The automatic update is not always desirable. For example, a frontend
24737 might want to keep a value of some expression for future reference,
24738 and never update it. For another example, fetching memory is
24739 relatively slow for embedded targets, so a frontend might want
24740 to disable automatic update for the variables that are either not
24741 visible on the screen, or ``closed''. This is possible using so
24742 called ``frozen variable objects''. Such variable objects are never
24743 implicitly updated.
24745 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
24746 fixed variable object, the expression is parsed when the variable
24747 object is created, including associating identifiers to specific
24748 variables. The meaning of expression never changes. For a floating
24749 variable object the values of variables whose names appear in the
24750 expressions are re-evaluated every time in the context of the current
24751 frame. Consider this example:
24756 struct work_state state;
24763 If a fixed variable object for the @code{state} variable is created in
24764 this function, and we enter the recursive call, the the variable
24765 object will report the value of @code{state} in the top-level
24766 @code{do_work} invocation. On the other hand, a floating variable
24767 object will report the value of @code{state} in the current frame.
24769 If an expression specified when creating a fixed variable object
24770 refers to a local variable, the variable object becomes bound to the
24771 thread and frame in which the variable object is created. When such
24772 variable object is updated, @value{GDBN} makes sure that the
24773 thread/frame combination the variable object is bound to still exists,
24774 and re-evaluates the variable object in context of that thread/frame.
24776 The following is the complete set of @sc{gdb/mi} operations defined to
24777 access this functionality:
24779 @multitable @columnfractions .4 .6
24780 @item @strong{Operation}
24781 @tab @strong{Description}
24783 @item @code{-enable-pretty-printing}
24784 @tab enable Python-based pretty-printing
24785 @item @code{-var-create}
24786 @tab create a variable object
24787 @item @code{-var-delete}
24788 @tab delete the variable object and/or its children
24789 @item @code{-var-set-format}
24790 @tab set the display format of this variable
24791 @item @code{-var-show-format}
24792 @tab show the display format of this variable
24793 @item @code{-var-info-num-children}
24794 @tab tells how many children this object has
24795 @item @code{-var-list-children}
24796 @tab return a list of the object's children
24797 @item @code{-var-info-type}
24798 @tab show the type of this variable object
24799 @item @code{-var-info-expression}
24800 @tab print parent-relative expression that this variable object represents
24801 @item @code{-var-info-path-expression}
24802 @tab print full expression that this variable object represents
24803 @item @code{-var-show-attributes}
24804 @tab is this variable editable? does it exist here?
24805 @item @code{-var-evaluate-expression}
24806 @tab get the value of this variable
24807 @item @code{-var-assign}
24808 @tab set the value of this variable
24809 @item @code{-var-update}
24810 @tab update the variable and its children
24811 @item @code{-var-set-frozen}
24812 @tab set frozeness attribute
24813 @item @code{-var-set-update-range}
24814 @tab set range of children to display on update
24817 In the next subsection we describe each operation in detail and suggest
24818 how it can be used.
24820 @subheading Description And Use of Operations on Variable Objects
24822 @subheading The @code{-enable-pretty-printing} Command
24823 @findex -enable-pretty-printing
24826 -enable-pretty-printing
24829 @value{GDBN} allows Python-based visualizers to affect the output of the
24830 MI variable object commands. However, because there was no way to
24831 implement this in a fully backward-compatible way, a front end must
24832 request that this functionality be enabled.
24834 Once enabled, this feature cannot be disabled.
24836 Note that if Python support has not been compiled into @value{GDBN},
24837 this command will still succeed (and do nothing).
24839 This feature is currently (as of @value{GDBN} 7.0) experimental, and
24840 may work differently in future versions of @value{GDBN}.
24842 @subheading The @code{-var-create} Command
24843 @findex -var-create
24845 @subsubheading Synopsis
24848 -var-create @{@var{name} | "-"@}
24849 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
24852 This operation creates a variable object, which allows the monitoring of
24853 a variable, the result of an expression, a memory cell or a CPU
24856 The @var{name} parameter is the string by which the object can be
24857 referenced. It must be unique. If @samp{-} is specified, the varobj
24858 system will generate a string ``varNNNNNN'' automatically. It will be
24859 unique provided that one does not specify @var{name} of that format.
24860 The command fails if a duplicate name is found.
24862 The frame under which the expression should be evaluated can be
24863 specified by @var{frame-addr}. A @samp{*} indicates that the current
24864 frame should be used. A @samp{@@} indicates that a floating variable
24865 object must be created.
24867 @var{expression} is any expression valid on the current language set (must not
24868 begin with a @samp{*}), or one of the following:
24872 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
24875 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
24878 @samp{$@var{regname}} --- a CPU register name
24881 @cindex dynamic varobj
24882 A varobj's contents may be provided by a Python-based pretty-printer. In this
24883 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
24884 have slightly different semantics in some cases. If the
24885 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
24886 will never create a dynamic varobj. This ensures backward
24887 compatibility for existing clients.
24889 @subsubheading Result
24891 This operation returns attributes of the newly-created varobj. These
24896 The name of the varobj.
24899 The number of children of the varobj. This number is not necessarily
24900 reliable for a dynamic varobj. Instead, you must examine the
24901 @samp{has_more} attribute.
24904 The varobj's scalar value. For a varobj whose type is some sort of
24905 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
24906 will not be interesting.
24909 The varobj's type. This is a string representation of the type, as
24910 would be printed by the @value{GDBN} CLI.
24913 If a variable object is bound to a specific thread, then this is the
24914 thread's identifier.
24917 For a dynamic varobj, this indicates whether there appear to be any
24918 children available. For a non-dynamic varobj, this will be 0.
24921 This attribute will be present and have the value @samp{1} if the
24922 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24923 then this attribute will not be present.
24926 A dynamic varobj can supply a display hint to the front end. The
24927 value comes directly from the Python pretty-printer object's
24928 @code{display_hint} method. @xref{Pretty Printing}.
24931 Typical output will look like this:
24934 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
24935 has_more="@var{has_more}"
24939 @subheading The @code{-var-delete} Command
24940 @findex -var-delete
24942 @subsubheading Synopsis
24945 -var-delete [ -c ] @var{name}
24948 Deletes a previously created variable object and all of its children.
24949 With the @samp{-c} option, just deletes the children.
24951 Returns an error if the object @var{name} is not found.
24954 @subheading The @code{-var-set-format} Command
24955 @findex -var-set-format
24957 @subsubheading Synopsis
24960 -var-set-format @var{name} @var{format-spec}
24963 Sets the output format for the value of the object @var{name} to be
24966 @anchor{-var-set-format}
24967 The syntax for the @var{format-spec} is as follows:
24970 @var{format-spec} @expansion{}
24971 @{binary | decimal | hexadecimal | octal | natural@}
24974 The natural format is the default format choosen automatically
24975 based on the variable type (like decimal for an @code{int}, hex
24976 for pointers, etc.).
24978 For a variable with children, the format is set only on the
24979 variable itself, and the children are not affected.
24981 @subheading The @code{-var-show-format} Command
24982 @findex -var-show-format
24984 @subsubheading Synopsis
24987 -var-show-format @var{name}
24990 Returns the format used to display the value of the object @var{name}.
24993 @var{format} @expansion{}
24998 @subheading The @code{-var-info-num-children} Command
24999 @findex -var-info-num-children
25001 @subsubheading Synopsis
25004 -var-info-num-children @var{name}
25007 Returns the number of children of a variable object @var{name}:
25013 Note that this number is not completely reliable for a dynamic varobj.
25014 It will return the current number of children, but more children may
25018 @subheading The @code{-var-list-children} Command
25019 @findex -var-list-children
25021 @subsubheading Synopsis
25024 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25026 @anchor{-var-list-children}
25028 Return a list of the children of the specified variable object and
25029 create variable objects for them, if they do not already exist. With
25030 a single argument or if @var{print-values} has a value for of 0 or
25031 @code{--no-values}, print only the names of the variables; if
25032 @var{print-values} is 1 or @code{--all-values}, also print their
25033 values; and if it is 2 or @code{--simple-values} print the name and
25034 value for simple data types and just the name for arrays, structures
25037 @var{from} and @var{to}, if specified, indicate the range of children
25038 to report. If @var{from} or @var{to} is less than zero, the range is
25039 reset and all children will be reported. Otherwise, children starting
25040 at @var{from} (zero-based) and up to and excluding @var{to} will be
25043 If a child range is requested, it will only affect the current call to
25044 @code{-var-list-children}, but not future calls to @code{-var-update}.
25045 For this, you must instead use @code{-var-set-update-range}. The
25046 intent of this approach is to enable a front end to implement any
25047 update approach it likes; for example, scrolling a view may cause the
25048 front end to request more children with @code{-var-list-children}, and
25049 then the front end could call @code{-var-set-update-range} with a
25050 different range to ensure that future updates are restricted to just
25053 For each child the following results are returned:
25058 Name of the variable object created for this child.
25061 The expression to be shown to the user by the front end to designate this child.
25062 For example this may be the name of a structure member.
25064 For a dynamic varobj, this value cannot be used to form an
25065 expression. There is no way to do this at all with a dynamic varobj.
25067 For C/C@t{++} structures there are several pseudo children returned to
25068 designate access qualifiers. For these pseudo children @var{exp} is
25069 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25070 type and value are not present.
25072 A dynamic varobj will not report the access qualifying
25073 pseudo-children, regardless of the language. This information is not
25074 available at all with a dynamic varobj.
25077 Number of children this child has. For a dynamic varobj, this will be
25081 The type of the child.
25084 If values were requested, this is the value.
25087 If this variable object is associated with a thread, this is the thread id.
25088 Otherwise this result is not present.
25091 If the variable object is frozen, this variable will be present with a value of 1.
25094 The result may have its own attributes:
25098 A dynamic varobj can supply a display hint to the front end. The
25099 value comes directly from the Python pretty-printer object's
25100 @code{display_hint} method. @xref{Pretty Printing}.
25103 This is an integer attribute which is nonzero if there are children
25104 remaining after the end of the selected range.
25107 @subsubheading Example
25111 -var-list-children n
25112 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25113 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25115 -var-list-children --all-values n
25116 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25117 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25121 @subheading The @code{-var-info-type} Command
25122 @findex -var-info-type
25124 @subsubheading Synopsis
25127 -var-info-type @var{name}
25130 Returns the type of the specified variable @var{name}. The type is
25131 returned as a string in the same format as it is output by the
25135 type=@var{typename}
25139 @subheading The @code{-var-info-expression} Command
25140 @findex -var-info-expression
25142 @subsubheading Synopsis
25145 -var-info-expression @var{name}
25148 Returns a string that is suitable for presenting this
25149 variable object in user interface. The string is generally
25150 not valid expression in the current language, and cannot be evaluated.
25152 For example, if @code{a} is an array, and variable object
25153 @code{A} was created for @code{a}, then we'll get this output:
25156 (gdb) -var-info-expression A.1
25157 ^done,lang="C",exp="1"
25161 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25163 Note that the output of the @code{-var-list-children} command also
25164 includes those expressions, so the @code{-var-info-expression} command
25167 @subheading The @code{-var-info-path-expression} Command
25168 @findex -var-info-path-expression
25170 @subsubheading Synopsis
25173 -var-info-path-expression @var{name}
25176 Returns an expression that can be evaluated in the current
25177 context and will yield the same value that a variable object has.
25178 Compare this with the @code{-var-info-expression} command, which
25179 result can be used only for UI presentation. Typical use of
25180 the @code{-var-info-path-expression} command is creating a
25181 watchpoint from a variable object.
25183 This command is currently not valid for children of a dynamic varobj,
25184 and will give an error when invoked on one.
25186 For example, suppose @code{C} is a C@t{++} class, derived from class
25187 @code{Base}, and that the @code{Base} class has a member called
25188 @code{m_size}. Assume a variable @code{c} is has the type of
25189 @code{C} and a variable object @code{C} was created for variable
25190 @code{c}. Then, we'll get this output:
25192 (gdb) -var-info-path-expression C.Base.public.m_size
25193 ^done,path_expr=((Base)c).m_size)
25196 @subheading The @code{-var-show-attributes} Command
25197 @findex -var-show-attributes
25199 @subsubheading Synopsis
25202 -var-show-attributes @var{name}
25205 List attributes of the specified variable object @var{name}:
25208 status=@var{attr} [ ( ,@var{attr} )* ]
25212 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25214 @subheading The @code{-var-evaluate-expression} Command
25215 @findex -var-evaluate-expression
25217 @subsubheading Synopsis
25220 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25223 Evaluates the expression that is represented by the specified variable
25224 object and returns its value as a string. The format of the string
25225 can be specified with the @samp{-f} option. The possible values of
25226 this option are the same as for @code{-var-set-format}
25227 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25228 the current display format will be used. The current display format
25229 can be changed using the @code{-var-set-format} command.
25235 Note that one must invoke @code{-var-list-children} for a variable
25236 before the value of a child variable can be evaluated.
25238 @subheading The @code{-var-assign} Command
25239 @findex -var-assign
25241 @subsubheading Synopsis
25244 -var-assign @var{name} @var{expression}
25247 Assigns the value of @var{expression} to the variable object specified
25248 by @var{name}. The object must be @samp{editable}. If the variable's
25249 value is altered by the assign, the variable will show up in any
25250 subsequent @code{-var-update} list.
25252 @subsubheading Example
25260 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25264 @subheading The @code{-var-update} Command
25265 @findex -var-update
25267 @subsubheading Synopsis
25270 -var-update [@var{print-values}] @{@var{name} | "*"@}
25273 Reevaluate the expressions corresponding to the variable object
25274 @var{name} and all its direct and indirect children, and return the
25275 list of variable objects whose values have changed; @var{name} must
25276 be a root variable object. Here, ``changed'' means that the result of
25277 @code{-var-evaluate-expression} before and after the
25278 @code{-var-update} is different. If @samp{*} is used as the variable
25279 object names, all existing variable objects are updated, except
25280 for frozen ones (@pxref{-var-set-frozen}). The option
25281 @var{print-values} determines whether both names and values, or just
25282 names are printed. The possible values of this option are the same
25283 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25284 recommended to use the @samp{--all-values} option, to reduce the
25285 number of MI commands needed on each program stop.
25287 With the @samp{*} parameter, if a variable object is bound to a
25288 currently running thread, it will not be updated, without any
25291 If @code{-var-set-update-range} was previously used on a varobj, then
25292 only the selected range of children will be reported.
25294 @code{-var-update} reports all the changed varobjs in a tuple named
25297 Each item in the change list is itself a tuple holding:
25301 The name of the varobj.
25304 If values were requested for this update, then this field will be
25305 present and will hold the value of the varobj.
25308 @anchor{-var-update}
25309 This field is a string which may take one of three values:
25313 The variable object's current value is valid.
25316 The variable object does not currently hold a valid value but it may
25317 hold one in the future if its associated expression comes back into
25321 The variable object no longer holds a valid value.
25322 This can occur when the executable file being debugged has changed,
25323 either through recompilation or by using the @value{GDBN} @code{file}
25324 command. The front end should normally choose to delete these variable
25328 In the future new values may be added to this list so the front should
25329 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25332 This is only present if the varobj is still valid. If the type
25333 changed, then this will be the string @samp{true}; otherwise it will
25337 If the varobj's type changed, then this field will be present and will
25340 @item new_num_children
25341 For a dynamic varobj, if the number of children changed, or if the
25342 type changed, this will be the new number of children.
25344 The @samp{numchild} field in other varobj responses is generally not
25345 valid for a dynamic varobj -- it will show the number of children that
25346 @value{GDBN} knows about, but because dynamic varobjs lazily
25347 instantiate their children, this will not reflect the number of
25348 children which may be available.
25350 The @samp{new_num_children} attribute only reports changes to the
25351 number of children known by @value{GDBN}. This is the only way to
25352 detect whether an update has removed children (which necessarily can
25353 only happen at the end of the update range).
25356 The display hint, if any.
25359 This is an integer value, which will be 1 if there are more children
25360 available outside the varobj's update range.
25363 This attribute will be present and have the value @samp{1} if the
25364 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25365 then this attribute will not be present.
25368 If new children were added to a dynamic varobj within the selected
25369 update range (as set by @code{-var-set-update-range}), then they will
25370 be listed in this attribute.
25373 @subsubheading Example
25380 -var-update --all-values var1
25381 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25382 type_changed="false"@}]
25386 @subheading The @code{-var-set-frozen} Command
25387 @findex -var-set-frozen
25388 @anchor{-var-set-frozen}
25390 @subsubheading Synopsis
25393 -var-set-frozen @var{name} @var{flag}
25396 Set the frozenness flag on the variable object @var{name}. The
25397 @var{flag} parameter should be either @samp{1} to make the variable
25398 frozen or @samp{0} to make it unfrozen. If a variable object is
25399 frozen, then neither itself, nor any of its children, are
25400 implicitly updated by @code{-var-update} of
25401 a parent variable or by @code{-var-update *}. Only
25402 @code{-var-update} of the variable itself will update its value and
25403 values of its children. After a variable object is unfrozen, it is
25404 implicitly updated by all subsequent @code{-var-update} operations.
25405 Unfreezing a variable does not update it, only subsequent
25406 @code{-var-update} does.
25408 @subsubheading Example
25412 -var-set-frozen V 1
25417 @subheading The @code{-var-set-update-range} command
25418 @findex -var-set-update-range
25419 @anchor{-var-set-update-range}
25421 @subsubheading Synopsis
25424 -var-set-update-range @var{name} @var{from} @var{to}
25427 Set the range of children to be returned by future invocations of
25428 @code{-var-update}.
25430 @var{from} and @var{to} indicate the range of children to report. If
25431 @var{from} or @var{to} is less than zero, the range is reset and all
25432 children will be reported. Otherwise, children starting at @var{from}
25433 (zero-based) and up to and excluding @var{to} will be reported.
25435 @subsubheading Example
25439 -var-set-update-range V 1 2
25443 @subheading The @code{-var-set-visualizer} command
25444 @findex -var-set-visualizer
25445 @anchor{-var-set-visualizer}
25447 @subsubheading Synopsis
25450 -var-set-visualizer @var{name} @var{visualizer}
25453 Set a visualizer for the variable object @var{name}.
25455 @var{visualizer} is the visualizer to use. The special value
25456 @samp{None} means to disable any visualizer in use.
25458 If not @samp{None}, @var{visualizer} must be a Python expression.
25459 This expression must evaluate to a callable object which accepts a
25460 single argument. @value{GDBN} will call this object with the value of
25461 the varobj @var{name} as an argument (this is done so that the same
25462 Python pretty-printing code can be used for both the CLI and MI).
25463 When called, this object must return an object which conforms to the
25464 pretty-printing interface (@pxref{Pretty Printing}).
25466 The pre-defined function @code{gdb.default_visualizer} may be used to
25467 select a visualizer by following the built-in process
25468 (@pxref{Selecting Pretty-Printers}). This is done automatically when
25469 a varobj is created, and so ordinarily is not needed.
25471 This feature is only available if Python support is enabled. The MI
25472 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
25473 can be used to check this.
25475 @subsubheading Example
25477 Resetting the visualizer:
25481 -var-set-visualizer V None
25485 Reselecting the default (type-based) visualizer:
25489 -var-set-visualizer V gdb.default_visualizer
25493 Suppose @code{SomeClass} is a visualizer class. A lambda expression
25494 can be used to instantiate this class for a varobj:
25498 -var-set-visualizer V "lambda val: SomeClass()"
25502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25503 @node GDB/MI Data Manipulation
25504 @section @sc{gdb/mi} Data Manipulation
25506 @cindex data manipulation, in @sc{gdb/mi}
25507 @cindex @sc{gdb/mi}, data manipulation
25508 This section describes the @sc{gdb/mi} commands that manipulate data:
25509 examine memory and registers, evaluate expressions, etc.
25511 @c REMOVED FROM THE INTERFACE.
25512 @c @subheading -data-assign
25513 @c Change the value of a program variable. Plenty of side effects.
25514 @c @subsubheading GDB Command
25516 @c @subsubheading Example
25519 @subheading The @code{-data-disassemble} Command
25520 @findex -data-disassemble
25522 @subsubheading Synopsis
25526 [ -s @var{start-addr} -e @var{end-addr} ]
25527 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
25535 @item @var{start-addr}
25536 is the beginning address (or @code{$pc})
25537 @item @var{end-addr}
25539 @item @var{filename}
25540 is the name of the file to disassemble
25541 @item @var{linenum}
25542 is the line number to disassemble around
25544 is the number of disassembly lines to be produced. If it is -1,
25545 the whole function will be disassembled, in case no @var{end-addr} is
25546 specified. If @var{end-addr} is specified as a non-zero value, and
25547 @var{lines} is lower than the number of disassembly lines between
25548 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
25549 displayed; if @var{lines} is higher than the number of lines between
25550 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
25553 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
25557 @subsubheading Result
25559 The output for each instruction is composed of four fields:
25568 Note that whatever included in the instruction field, is not manipulated
25569 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
25571 @subsubheading @value{GDBN} Command
25573 There's no direct mapping from this command to the CLI.
25575 @subsubheading Example
25577 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
25581 -data-disassemble -s $pc -e "$pc + 20" -- 0
25584 @{address="0x000107c0",func-name="main",offset="4",
25585 inst="mov 2, %o0"@},
25586 @{address="0x000107c4",func-name="main",offset="8",
25587 inst="sethi %hi(0x11800), %o2"@},
25588 @{address="0x000107c8",func-name="main",offset="12",
25589 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
25590 @{address="0x000107cc",func-name="main",offset="16",
25591 inst="sethi %hi(0x11800), %o2"@},
25592 @{address="0x000107d0",func-name="main",offset="20",
25593 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
25597 Disassemble the whole @code{main} function. Line 32 is part of
25601 -data-disassemble -f basics.c -l 32 -- 0
25603 @{address="0x000107bc",func-name="main",offset="0",
25604 inst="save %sp, -112, %sp"@},
25605 @{address="0x000107c0",func-name="main",offset="4",
25606 inst="mov 2, %o0"@},
25607 @{address="0x000107c4",func-name="main",offset="8",
25608 inst="sethi %hi(0x11800), %o2"@},
25610 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
25611 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
25615 Disassemble 3 instructions from the start of @code{main}:
25619 -data-disassemble -f basics.c -l 32 -n 3 -- 0
25621 @{address="0x000107bc",func-name="main",offset="0",
25622 inst="save %sp, -112, %sp"@},
25623 @{address="0x000107c0",func-name="main",offset="4",
25624 inst="mov 2, %o0"@},
25625 @{address="0x000107c4",func-name="main",offset="8",
25626 inst="sethi %hi(0x11800), %o2"@}]
25630 Disassemble 3 instructions from the start of @code{main} in mixed mode:
25634 -data-disassemble -f basics.c -l 32 -n 3 -- 1
25636 src_and_asm_line=@{line="31",
25637 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25638 testsuite/gdb.mi/basics.c",line_asm_insn=[
25639 @{address="0x000107bc",func-name="main",offset="0",
25640 inst="save %sp, -112, %sp"@}]@},
25641 src_and_asm_line=@{line="32",
25642 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25643 testsuite/gdb.mi/basics.c",line_asm_insn=[
25644 @{address="0x000107c0",func-name="main",offset="4",
25645 inst="mov 2, %o0"@},
25646 @{address="0x000107c4",func-name="main",offset="8",
25647 inst="sethi %hi(0x11800), %o2"@}]@}]
25652 @subheading The @code{-data-evaluate-expression} Command
25653 @findex -data-evaluate-expression
25655 @subsubheading Synopsis
25658 -data-evaluate-expression @var{expr}
25661 Evaluate @var{expr} as an expression. The expression could contain an
25662 inferior function call. The function call will execute synchronously.
25663 If the expression contains spaces, it must be enclosed in double quotes.
25665 @subsubheading @value{GDBN} Command
25667 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
25668 @samp{call}. In @code{gdbtk} only, there's a corresponding
25669 @samp{gdb_eval} command.
25671 @subsubheading Example
25673 In the following example, the numbers that precede the commands are the
25674 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
25675 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
25679 211-data-evaluate-expression A
25682 311-data-evaluate-expression &A
25683 311^done,value="0xefffeb7c"
25685 411-data-evaluate-expression A+3
25688 511-data-evaluate-expression "A + 3"
25694 @subheading The @code{-data-list-changed-registers} Command
25695 @findex -data-list-changed-registers
25697 @subsubheading Synopsis
25700 -data-list-changed-registers
25703 Display a list of the registers that have changed.
25705 @subsubheading @value{GDBN} Command
25707 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
25708 has the corresponding command @samp{gdb_changed_register_list}.
25710 @subsubheading Example
25712 On a PPC MBX board:
25720 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
25721 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
25724 -data-list-changed-registers
25725 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
25726 "10","11","13","14","15","16","17","18","19","20","21","22","23",
25727 "24","25","26","27","28","30","31","64","65","66","67","69"]
25732 @subheading The @code{-data-list-register-names} Command
25733 @findex -data-list-register-names
25735 @subsubheading Synopsis
25738 -data-list-register-names [ ( @var{regno} )+ ]
25741 Show a list of register names for the current target. If no arguments
25742 are given, it shows a list of the names of all the registers. If
25743 integer numbers are given as arguments, it will print a list of the
25744 names of the registers corresponding to the arguments. To ensure
25745 consistency between a register name and its number, the output list may
25746 include empty register names.
25748 @subsubheading @value{GDBN} Command
25750 @value{GDBN} does not have a command which corresponds to
25751 @samp{-data-list-register-names}. In @code{gdbtk} there is a
25752 corresponding command @samp{gdb_regnames}.
25754 @subsubheading Example
25756 For the PPC MBX board:
25759 -data-list-register-names
25760 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
25761 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
25762 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
25763 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
25764 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
25765 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
25766 "", "pc","ps","cr","lr","ctr","xer"]
25768 -data-list-register-names 1 2 3
25769 ^done,register-names=["r1","r2","r3"]
25773 @subheading The @code{-data-list-register-values} Command
25774 @findex -data-list-register-values
25776 @subsubheading Synopsis
25779 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
25782 Display the registers' contents. @var{fmt} is the format according to
25783 which the registers' contents are to be returned, followed by an optional
25784 list of numbers specifying the registers to display. A missing list of
25785 numbers indicates that the contents of all the registers must be returned.
25787 Allowed formats for @var{fmt} are:
25804 @subsubheading @value{GDBN} Command
25806 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
25807 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
25809 @subsubheading Example
25811 For a PPC MBX board (note: line breaks are for readability only, they
25812 don't appear in the actual output):
25816 -data-list-register-values r 64 65
25817 ^done,register-values=[@{number="64",value="0xfe00a300"@},
25818 @{number="65",value="0x00029002"@}]
25820 -data-list-register-values x
25821 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
25822 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
25823 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
25824 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
25825 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
25826 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
25827 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
25828 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
25829 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
25830 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
25831 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
25832 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
25833 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
25834 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
25835 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
25836 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
25837 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
25838 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
25839 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
25840 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
25841 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
25842 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
25843 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
25844 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
25845 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
25846 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
25847 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
25848 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
25849 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
25850 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
25851 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
25852 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
25853 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
25854 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
25855 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
25856 @{number="69",value="0x20002b03"@}]
25861 @subheading The @code{-data-read-memory} Command
25862 @findex -data-read-memory
25864 @subsubheading Synopsis
25867 -data-read-memory [ -o @var{byte-offset} ]
25868 @var{address} @var{word-format} @var{word-size}
25869 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
25876 @item @var{address}
25877 An expression specifying the address of the first memory word to be
25878 read. Complex expressions containing embedded white space should be
25879 quoted using the C convention.
25881 @item @var{word-format}
25882 The format to be used to print the memory words. The notation is the
25883 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
25886 @item @var{word-size}
25887 The size of each memory word in bytes.
25889 @item @var{nr-rows}
25890 The number of rows in the output table.
25892 @item @var{nr-cols}
25893 The number of columns in the output table.
25896 If present, indicates that each row should include an @sc{ascii} dump. The
25897 value of @var{aschar} is used as a padding character when a byte is not a
25898 member of the printable @sc{ascii} character set (printable @sc{ascii}
25899 characters are those whose code is between 32 and 126, inclusively).
25901 @item @var{byte-offset}
25902 An offset to add to the @var{address} before fetching memory.
25905 This command displays memory contents as a table of @var{nr-rows} by
25906 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
25907 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
25908 (returned as @samp{total-bytes}). Should less than the requested number
25909 of bytes be returned by the target, the missing words are identified
25910 using @samp{N/A}. The number of bytes read from the target is returned
25911 in @samp{nr-bytes} and the starting address used to read memory in
25914 The address of the next/previous row or page is available in
25915 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
25918 @subsubheading @value{GDBN} Command
25920 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
25921 @samp{gdb_get_mem} memory read command.
25923 @subsubheading Example
25925 Read six bytes of memory starting at @code{bytes+6} but then offset by
25926 @code{-6} bytes. Format as three rows of two columns. One byte per
25927 word. Display each word in hex.
25931 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
25932 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
25933 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
25934 prev-page="0x0000138a",memory=[
25935 @{addr="0x00001390",data=["0x00","0x01"]@},
25936 @{addr="0x00001392",data=["0x02","0x03"]@},
25937 @{addr="0x00001394",data=["0x04","0x05"]@}]
25941 Read two bytes of memory starting at address @code{shorts + 64} and
25942 display as a single word formatted in decimal.
25946 5-data-read-memory shorts+64 d 2 1 1
25947 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
25948 next-row="0x00001512",prev-row="0x0000150e",
25949 next-page="0x00001512",prev-page="0x0000150e",memory=[
25950 @{addr="0x00001510",data=["128"]@}]
25954 Read thirty two bytes of memory starting at @code{bytes+16} and format
25955 as eight rows of four columns. Include a string encoding with @samp{x}
25956 used as the non-printable character.
25960 4-data-read-memory bytes+16 x 1 8 4 x
25961 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
25962 next-row="0x000013c0",prev-row="0x0000139c",
25963 next-page="0x000013c0",prev-page="0x00001380",memory=[
25964 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
25965 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
25966 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
25967 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
25968 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
25969 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
25970 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
25971 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
25975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25976 @node GDB/MI Tracepoint Commands
25977 @section @sc{gdb/mi} Tracepoint Commands
25979 The commands defined in this section implement MI support for
25980 tracepoints. For detailed introduction, see @ref{Tracepoints}.
25982 @subheading The @code{-trace-find} Command
25983 @findex -trace-find
25985 @subsubheading Synopsis
25988 -trace-find @var{mode} [@var{parameters}@dots{}]
25991 Find a trace frame using criteria defined by @var{mode} and
25992 @var{parameters}. The following table lists permissible
25993 modes and their parameters. For details of operation, see @ref{tfind}.
25998 No parameters are required. Stops examining trace frames.
26001 An integer is required as parameter. Selects tracepoint frame with
26004 @item tracepoint-number
26005 An integer is required as parameter. Finds next
26006 trace frame that corresponds to tracepoint with the specified number.
26009 An address is required as parameter. Finds
26010 next trace frame that corresponds to any tracepoint at the specified
26013 @item pc-inside-range
26014 Two addresses are required as parameters. Finds next trace
26015 frame that corresponds to a tracepoint at an address inside the
26016 specified range. Both bounds are considered to be inside the range.
26018 @item pc-outside-range
26019 Two addresses are required as parameters. Finds
26020 next trace frame that corresponds to a tracepoint at an address outside
26021 the specified range. Both bounds are considered to be inside the range.
26024 Line specification is required as parameter. @xref{Specify Location}.
26025 Finds next trace frame that corresponds to a tracepoint at
26026 the specified location.
26030 If @samp{none} was passed as @var{mode}, the response does not
26031 have fields. Otherwise, the response may have the following fields:
26035 This field has either @samp{0} or @samp{1} as the value, depending
26036 on whether a matching tracepoint was found.
26039 The index of the found traceframe. This field is present iff
26040 the @samp{found} field has value of @samp{1}.
26043 The index of the found tracepoint. This field is present iff
26044 the @samp{found} field has value of @samp{1}.
26047 The information about the frame corresponding to the found trace
26048 frame. This field is present only if a trace frame was found.
26049 @xref{GDB/MI Frame Information} for description of this field.
26053 @subheading -trace-define-variable
26054 @findex -trace-define-variable
26056 @subsubheading Synopsis
26059 -trace-define-variable @var{name} [ @var{value} ]
26062 Create trace variable @var{name} if it does not exist. If
26063 @var{value} is specified, sets the initial value of the specified
26064 trace variable to that value. Note that the @var{name} should start
26065 with the @samp{$} character.
26067 @subheading -trace-list-variables
26068 @findex -trace-list-variables
26070 @subsubheading Synopsis
26073 -trace-list-variables
26076 Return a table of all defined trace variables. Each element of the
26077 table has the following fields:
26081 The name of the trace variable. This field is always present.
26084 The initial value. This is a 64-bit signed integer. This
26085 field is always present.
26088 The value the trace variable has at the moment. This is a 64-bit
26089 signed integer. This field is absent iff current value is
26090 not defined, for example if the trace was never run, or is
26095 @subsubheading Example
26099 -trace-list-variables
26100 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26101 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26102 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26103 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26104 body=[variable=@{name="$trace_timestamp",initial="0"@}
26105 variable=@{name="$foo",initial="10",current="15"@}]@}
26109 @subheading -trace-save
26110 @findex -trace-save
26112 @subsubheading Synopsis
26115 -trace-save [-r ] @var{filename}
26118 Saves the collected trace data to @var{filename}. Without the
26119 @samp{-r} option, the data is downloaded from the target and saved
26120 in a local file. With the @samp{-r} option the target is asked
26121 to perform the save.
26124 @subheading -trace-start
26125 @findex -trace-start
26127 @subsubheading Synopsis
26133 Starts a tracing experiments. The result of this command does not
26136 @subheading -trace-status
26137 @findex -trace-status
26139 @subsubheading Synopsis
26145 Obtains the status of a tracing experiement. The result may include
26146 the following fields:
26151 May have a value of either @samp{0}, when no tracing operations are
26152 supported, @samp{1}, when all tracing operations are supported, or
26153 @samp{file} when examining trace file. In the latter case, examining
26154 of trace frame is possible but new tracing experiement cannot be
26155 started. This field is always present.
26158 May have a value of either @samp{0} or @samp{1} depending on whether
26159 tracing experiement is in progress on target. This field is present
26160 if @samp{supported} field is not @samp{0}.
26163 Report the reason why the tracing was stopped last time. This field
26164 may be absent iff tracing was never stopped on target yet. The
26165 value of @samp{request} means the tracing was stopped as result of
26166 the @code{-trace-stop} command. The value of @samp{overflow} means
26167 the tracing buffer is full. The value of @samp{disconnection} means
26168 tracing was automatically stopped when @value{GDBN} has disconnected.
26169 The value of @samp{passcount} means tracing was stopped when a
26170 tracepoint was passed a maximal number of times for that tracepoint.
26171 This field is present if @samp{supported} field is not @samp{0}.
26173 @item stopping-tracepoint
26174 The number of tracepoint whose passcount as exceeded. This field is
26175 present iff the @samp{stop-reason} field has the value of
26179 This field is an integer number of currently collected frames. This
26184 These fields tell the current size of the tracing buffer and the
26185 remaining space. These field is optional.
26189 @subheading -trace-stop
26190 @findex -trace-stop
26192 @subsubheading Synopsis
26198 Stops a tracing experiment. The result of this command has the same
26199 fields as @code{-trace-status}, except that the @samp{supported} and
26200 @samp{running} fields are not output.
26203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26204 @node GDB/MI Symbol Query
26205 @section @sc{gdb/mi} Symbol Query Commands
26209 @subheading The @code{-symbol-info-address} Command
26210 @findex -symbol-info-address
26212 @subsubheading Synopsis
26215 -symbol-info-address @var{symbol}
26218 Describe where @var{symbol} is stored.
26220 @subsubheading @value{GDBN} Command
26222 The corresponding @value{GDBN} command is @samp{info address}.
26224 @subsubheading Example
26228 @subheading The @code{-symbol-info-file} Command
26229 @findex -symbol-info-file
26231 @subsubheading Synopsis
26237 Show the file for the symbol.
26239 @subsubheading @value{GDBN} Command
26241 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26242 @samp{gdb_find_file}.
26244 @subsubheading Example
26248 @subheading The @code{-symbol-info-function} Command
26249 @findex -symbol-info-function
26251 @subsubheading Synopsis
26254 -symbol-info-function
26257 Show which function the symbol lives in.
26259 @subsubheading @value{GDBN} Command
26261 @samp{gdb_get_function} in @code{gdbtk}.
26263 @subsubheading Example
26267 @subheading The @code{-symbol-info-line} Command
26268 @findex -symbol-info-line
26270 @subsubheading Synopsis
26276 Show the core addresses of the code for a source line.
26278 @subsubheading @value{GDBN} Command
26280 The corresponding @value{GDBN} command is @samp{info line}.
26281 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26283 @subsubheading Example
26287 @subheading The @code{-symbol-info-symbol} Command
26288 @findex -symbol-info-symbol
26290 @subsubheading Synopsis
26293 -symbol-info-symbol @var{addr}
26296 Describe what symbol is at location @var{addr}.
26298 @subsubheading @value{GDBN} Command
26300 The corresponding @value{GDBN} command is @samp{info symbol}.
26302 @subsubheading Example
26306 @subheading The @code{-symbol-list-functions} Command
26307 @findex -symbol-list-functions
26309 @subsubheading Synopsis
26312 -symbol-list-functions
26315 List the functions in the executable.
26317 @subsubheading @value{GDBN} Command
26319 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26320 @samp{gdb_search} in @code{gdbtk}.
26322 @subsubheading Example
26327 @subheading The @code{-symbol-list-lines} Command
26328 @findex -symbol-list-lines
26330 @subsubheading Synopsis
26333 -symbol-list-lines @var{filename}
26336 Print the list of lines that contain code and their associated program
26337 addresses for the given source filename. The entries are sorted in
26338 ascending PC order.
26340 @subsubheading @value{GDBN} Command
26342 There is no corresponding @value{GDBN} command.
26344 @subsubheading Example
26347 -symbol-list-lines basics.c
26348 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26354 @subheading The @code{-symbol-list-types} Command
26355 @findex -symbol-list-types
26357 @subsubheading Synopsis
26363 List all the type names.
26365 @subsubheading @value{GDBN} Command
26367 The corresponding commands are @samp{info types} in @value{GDBN},
26368 @samp{gdb_search} in @code{gdbtk}.
26370 @subsubheading Example
26374 @subheading The @code{-symbol-list-variables} Command
26375 @findex -symbol-list-variables
26377 @subsubheading Synopsis
26380 -symbol-list-variables
26383 List all the global and static variable names.
26385 @subsubheading @value{GDBN} Command
26387 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
26389 @subsubheading Example
26393 @subheading The @code{-symbol-locate} Command
26394 @findex -symbol-locate
26396 @subsubheading Synopsis
26402 @subsubheading @value{GDBN} Command
26404 @samp{gdb_loc} in @code{gdbtk}.
26406 @subsubheading Example
26410 @subheading The @code{-symbol-type} Command
26411 @findex -symbol-type
26413 @subsubheading Synopsis
26416 -symbol-type @var{variable}
26419 Show type of @var{variable}.
26421 @subsubheading @value{GDBN} Command
26423 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
26424 @samp{gdb_obj_variable}.
26426 @subsubheading Example
26431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26432 @node GDB/MI File Commands
26433 @section @sc{gdb/mi} File Commands
26435 This section describes the GDB/MI commands to specify executable file names
26436 and to read in and obtain symbol table information.
26438 @subheading The @code{-file-exec-and-symbols} Command
26439 @findex -file-exec-and-symbols
26441 @subsubheading Synopsis
26444 -file-exec-and-symbols @var{file}
26447 Specify the executable file to be debugged. This file is the one from
26448 which the symbol table is also read. If no file is specified, the
26449 command clears the executable and symbol information. If breakpoints
26450 are set when using this command with no arguments, @value{GDBN} will produce
26451 error messages. Otherwise, no output is produced, except a completion
26454 @subsubheading @value{GDBN} Command
26456 The corresponding @value{GDBN} command is @samp{file}.
26458 @subsubheading Example
26462 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26468 @subheading The @code{-file-exec-file} Command
26469 @findex -file-exec-file
26471 @subsubheading Synopsis
26474 -file-exec-file @var{file}
26477 Specify the executable file to be debugged. Unlike
26478 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
26479 from this file. If used without argument, @value{GDBN} clears the information
26480 about the executable file. No output is produced, except a completion
26483 @subsubheading @value{GDBN} Command
26485 The corresponding @value{GDBN} command is @samp{exec-file}.
26487 @subsubheading Example
26491 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26498 @subheading The @code{-file-list-exec-sections} Command
26499 @findex -file-list-exec-sections
26501 @subsubheading Synopsis
26504 -file-list-exec-sections
26507 List the sections of the current executable file.
26509 @subsubheading @value{GDBN} Command
26511 The @value{GDBN} command @samp{info file} shows, among the rest, the same
26512 information as this command. @code{gdbtk} has a corresponding command
26513 @samp{gdb_load_info}.
26515 @subsubheading Example
26520 @subheading The @code{-file-list-exec-source-file} Command
26521 @findex -file-list-exec-source-file
26523 @subsubheading Synopsis
26526 -file-list-exec-source-file
26529 List the line number, the current source file, and the absolute path
26530 to the current source file for the current executable. The macro
26531 information field has a value of @samp{1} or @samp{0} depending on
26532 whether or not the file includes preprocessor macro information.
26534 @subsubheading @value{GDBN} Command
26536 The @value{GDBN} equivalent is @samp{info source}
26538 @subsubheading Example
26542 123-file-list-exec-source-file
26543 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
26548 @subheading The @code{-file-list-exec-source-files} Command
26549 @findex -file-list-exec-source-files
26551 @subsubheading Synopsis
26554 -file-list-exec-source-files
26557 List the source files for the current executable.
26559 It will always output the filename, but only when @value{GDBN} can find
26560 the absolute file name of a source file, will it output the fullname.
26562 @subsubheading @value{GDBN} Command
26564 The @value{GDBN} equivalent is @samp{info sources}.
26565 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
26567 @subsubheading Example
26570 -file-list-exec-source-files
26572 @{file=foo.c,fullname=/home/foo.c@},
26573 @{file=/home/bar.c,fullname=/home/bar.c@},
26574 @{file=gdb_could_not_find_fullpath.c@}]
26579 @subheading The @code{-file-list-shared-libraries} Command
26580 @findex -file-list-shared-libraries
26582 @subsubheading Synopsis
26585 -file-list-shared-libraries
26588 List the shared libraries in the program.
26590 @subsubheading @value{GDBN} Command
26592 The corresponding @value{GDBN} command is @samp{info shared}.
26594 @subsubheading Example
26598 @subheading The @code{-file-list-symbol-files} Command
26599 @findex -file-list-symbol-files
26601 @subsubheading Synopsis
26604 -file-list-symbol-files
26609 @subsubheading @value{GDBN} Command
26611 The corresponding @value{GDBN} command is @samp{info file} (part of it).
26613 @subsubheading Example
26618 @subheading The @code{-file-symbol-file} Command
26619 @findex -file-symbol-file
26621 @subsubheading Synopsis
26624 -file-symbol-file @var{file}
26627 Read symbol table info from the specified @var{file} argument. When
26628 used without arguments, clears @value{GDBN}'s symbol table info. No output is
26629 produced, except for a completion notification.
26631 @subsubheading @value{GDBN} Command
26633 The corresponding @value{GDBN} command is @samp{symbol-file}.
26635 @subsubheading Example
26639 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26646 @node GDB/MI Memory Overlay Commands
26647 @section @sc{gdb/mi} Memory Overlay Commands
26649 The memory overlay commands are not implemented.
26651 @c @subheading -overlay-auto
26653 @c @subheading -overlay-list-mapping-state
26655 @c @subheading -overlay-list-overlays
26657 @c @subheading -overlay-map
26659 @c @subheading -overlay-off
26661 @c @subheading -overlay-on
26663 @c @subheading -overlay-unmap
26665 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26666 @node GDB/MI Signal Handling Commands
26667 @section @sc{gdb/mi} Signal Handling Commands
26669 Signal handling commands are not implemented.
26671 @c @subheading -signal-handle
26673 @c @subheading -signal-list-handle-actions
26675 @c @subheading -signal-list-signal-types
26679 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26680 @node GDB/MI Target Manipulation
26681 @section @sc{gdb/mi} Target Manipulation Commands
26684 @subheading The @code{-target-attach} Command
26685 @findex -target-attach
26687 @subsubheading Synopsis
26690 -target-attach @var{pid} | @var{gid} | @var{file}
26693 Attach to a process @var{pid} or a file @var{file} outside of
26694 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
26695 group, the id previously returned by
26696 @samp{-list-thread-groups --available} must be used.
26698 @subsubheading @value{GDBN} Command
26700 The corresponding @value{GDBN} command is @samp{attach}.
26702 @subsubheading Example
26706 =thread-created,id="1"
26707 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
26713 @subheading The @code{-target-compare-sections} Command
26714 @findex -target-compare-sections
26716 @subsubheading Synopsis
26719 -target-compare-sections [ @var{section} ]
26722 Compare data of section @var{section} on target to the exec file.
26723 Without the argument, all sections are compared.
26725 @subsubheading @value{GDBN} Command
26727 The @value{GDBN} equivalent is @samp{compare-sections}.
26729 @subsubheading Example
26734 @subheading The @code{-target-detach} Command
26735 @findex -target-detach
26737 @subsubheading Synopsis
26740 -target-detach [ @var{pid} | @var{gid} ]
26743 Detach from the remote target which normally resumes its execution.
26744 If either @var{pid} or @var{gid} is specified, detaches from either
26745 the specified process, or specified thread group. There's no output.
26747 @subsubheading @value{GDBN} Command
26749 The corresponding @value{GDBN} command is @samp{detach}.
26751 @subsubheading Example
26761 @subheading The @code{-target-disconnect} Command
26762 @findex -target-disconnect
26764 @subsubheading Synopsis
26770 Disconnect from the remote target. There's no output and the target is
26771 generally not resumed.
26773 @subsubheading @value{GDBN} Command
26775 The corresponding @value{GDBN} command is @samp{disconnect}.
26777 @subsubheading Example
26787 @subheading The @code{-target-download} Command
26788 @findex -target-download
26790 @subsubheading Synopsis
26796 Loads the executable onto the remote target.
26797 It prints out an update message every half second, which includes the fields:
26801 The name of the section.
26803 The size of what has been sent so far for that section.
26805 The size of the section.
26807 The total size of what was sent so far (the current and the previous sections).
26809 The size of the overall executable to download.
26813 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
26814 @sc{gdb/mi} Output Syntax}).
26816 In addition, it prints the name and size of the sections, as they are
26817 downloaded. These messages include the following fields:
26821 The name of the section.
26823 The size of the section.
26825 The size of the overall executable to download.
26829 At the end, a summary is printed.
26831 @subsubheading @value{GDBN} Command
26833 The corresponding @value{GDBN} command is @samp{load}.
26835 @subsubheading Example
26837 Note: each status message appears on a single line. Here the messages
26838 have been broken down so that they can fit onto a page.
26843 +download,@{section=".text",section-size="6668",total-size="9880"@}
26844 +download,@{section=".text",section-sent="512",section-size="6668",
26845 total-sent="512",total-size="9880"@}
26846 +download,@{section=".text",section-sent="1024",section-size="6668",
26847 total-sent="1024",total-size="9880"@}
26848 +download,@{section=".text",section-sent="1536",section-size="6668",
26849 total-sent="1536",total-size="9880"@}
26850 +download,@{section=".text",section-sent="2048",section-size="6668",
26851 total-sent="2048",total-size="9880"@}
26852 +download,@{section=".text",section-sent="2560",section-size="6668",
26853 total-sent="2560",total-size="9880"@}
26854 +download,@{section=".text",section-sent="3072",section-size="6668",
26855 total-sent="3072",total-size="9880"@}
26856 +download,@{section=".text",section-sent="3584",section-size="6668",
26857 total-sent="3584",total-size="9880"@}
26858 +download,@{section=".text",section-sent="4096",section-size="6668",
26859 total-sent="4096",total-size="9880"@}
26860 +download,@{section=".text",section-sent="4608",section-size="6668",
26861 total-sent="4608",total-size="9880"@}
26862 +download,@{section=".text",section-sent="5120",section-size="6668",
26863 total-sent="5120",total-size="9880"@}
26864 +download,@{section=".text",section-sent="5632",section-size="6668",
26865 total-sent="5632",total-size="9880"@}
26866 +download,@{section=".text",section-sent="6144",section-size="6668",
26867 total-sent="6144",total-size="9880"@}
26868 +download,@{section=".text",section-sent="6656",section-size="6668",
26869 total-sent="6656",total-size="9880"@}
26870 +download,@{section=".init",section-size="28",total-size="9880"@}
26871 +download,@{section=".fini",section-size="28",total-size="9880"@}
26872 +download,@{section=".data",section-size="3156",total-size="9880"@}
26873 +download,@{section=".data",section-sent="512",section-size="3156",
26874 total-sent="7236",total-size="9880"@}
26875 +download,@{section=".data",section-sent="1024",section-size="3156",
26876 total-sent="7748",total-size="9880"@}
26877 +download,@{section=".data",section-sent="1536",section-size="3156",
26878 total-sent="8260",total-size="9880"@}
26879 +download,@{section=".data",section-sent="2048",section-size="3156",
26880 total-sent="8772",total-size="9880"@}
26881 +download,@{section=".data",section-sent="2560",section-size="3156",
26882 total-sent="9284",total-size="9880"@}
26883 +download,@{section=".data",section-sent="3072",section-size="3156",
26884 total-sent="9796",total-size="9880"@}
26885 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
26892 @subheading The @code{-target-exec-status} Command
26893 @findex -target-exec-status
26895 @subsubheading Synopsis
26898 -target-exec-status
26901 Provide information on the state of the target (whether it is running or
26902 not, for instance).
26904 @subsubheading @value{GDBN} Command
26906 There's no equivalent @value{GDBN} command.
26908 @subsubheading Example
26912 @subheading The @code{-target-list-available-targets} Command
26913 @findex -target-list-available-targets
26915 @subsubheading Synopsis
26918 -target-list-available-targets
26921 List the possible targets to connect to.
26923 @subsubheading @value{GDBN} Command
26925 The corresponding @value{GDBN} command is @samp{help target}.
26927 @subsubheading Example
26931 @subheading The @code{-target-list-current-targets} Command
26932 @findex -target-list-current-targets
26934 @subsubheading Synopsis
26937 -target-list-current-targets
26940 Describe the current target.
26942 @subsubheading @value{GDBN} Command
26944 The corresponding information is printed by @samp{info file} (among
26947 @subsubheading Example
26951 @subheading The @code{-target-list-parameters} Command
26952 @findex -target-list-parameters
26954 @subsubheading Synopsis
26957 -target-list-parameters
26963 @subsubheading @value{GDBN} Command
26967 @subsubheading Example
26971 @subheading The @code{-target-select} Command
26972 @findex -target-select
26974 @subsubheading Synopsis
26977 -target-select @var{type} @var{parameters @dots{}}
26980 Connect @value{GDBN} to the remote target. This command takes two args:
26984 The type of target, for instance @samp{remote}, etc.
26985 @item @var{parameters}
26986 Device names, host names and the like. @xref{Target Commands, ,
26987 Commands for Managing Targets}, for more details.
26990 The output is a connection notification, followed by the address at
26991 which the target program is, in the following form:
26994 ^connected,addr="@var{address}",func="@var{function name}",
26995 args=[@var{arg list}]
26998 @subsubheading @value{GDBN} Command
27000 The corresponding @value{GDBN} command is @samp{target}.
27002 @subsubheading Example
27006 -target-select remote /dev/ttya
27007 ^connected,addr="0xfe00a300",func="??",args=[]
27011 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27012 @node GDB/MI File Transfer Commands
27013 @section @sc{gdb/mi} File Transfer Commands
27016 @subheading The @code{-target-file-put} Command
27017 @findex -target-file-put
27019 @subsubheading Synopsis
27022 -target-file-put @var{hostfile} @var{targetfile}
27025 Copy file @var{hostfile} from the host system (the machine running
27026 @value{GDBN}) to @var{targetfile} on the target system.
27028 @subsubheading @value{GDBN} Command
27030 The corresponding @value{GDBN} command is @samp{remote put}.
27032 @subsubheading Example
27036 -target-file-put localfile remotefile
27042 @subheading The @code{-target-file-get} Command
27043 @findex -target-file-get
27045 @subsubheading Synopsis
27048 -target-file-get @var{targetfile} @var{hostfile}
27051 Copy file @var{targetfile} from the target system to @var{hostfile}
27052 on the host system.
27054 @subsubheading @value{GDBN} Command
27056 The corresponding @value{GDBN} command is @samp{remote get}.
27058 @subsubheading Example
27062 -target-file-get remotefile localfile
27068 @subheading The @code{-target-file-delete} Command
27069 @findex -target-file-delete
27071 @subsubheading Synopsis
27074 -target-file-delete @var{targetfile}
27077 Delete @var{targetfile} from the target system.
27079 @subsubheading @value{GDBN} Command
27081 The corresponding @value{GDBN} command is @samp{remote delete}.
27083 @subsubheading Example
27087 -target-file-delete remotefile
27093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27094 @node GDB/MI Miscellaneous Commands
27095 @section Miscellaneous @sc{gdb/mi} Commands
27097 @c @subheading -gdb-complete
27099 @subheading The @code{-gdb-exit} Command
27102 @subsubheading Synopsis
27108 Exit @value{GDBN} immediately.
27110 @subsubheading @value{GDBN} Command
27112 Approximately corresponds to @samp{quit}.
27114 @subsubheading Example
27124 @subheading The @code{-exec-abort} Command
27125 @findex -exec-abort
27127 @subsubheading Synopsis
27133 Kill the inferior running program.
27135 @subsubheading @value{GDBN} Command
27137 The corresponding @value{GDBN} command is @samp{kill}.
27139 @subsubheading Example
27144 @subheading The @code{-gdb-set} Command
27147 @subsubheading Synopsis
27153 Set an internal @value{GDBN} variable.
27154 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27156 @subsubheading @value{GDBN} Command
27158 The corresponding @value{GDBN} command is @samp{set}.
27160 @subsubheading Example
27170 @subheading The @code{-gdb-show} Command
27173 @subsubheading Synopsis
27179 Show the current value of a @value{GDBN} variable.
27181 @subsubheading @value{GDBN} Command
27183 The corresponding @value{GDBN} command is @samp{show}.
27185 @subsubheading Example
27194 @c @subheading -gdb-source
27197 @subheading The @code{-gdb-version} Command
27198 @findex -gdb-version
27200 @subsubheading Synopsis
27206 Show version information for @value{GDBN}. Used mostly in testing.
27208 @subsubheading @value{GDBN} Command
27210 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27211 default shows this information when you start an interactive session.
27213 @subsubheading Example
27215 @c This example modifies the actual output from GDB to avoid overfull
27221 ~Copyright 2000 Free Software Foundation, Inc.
27222 ~GDB is free software, covered by the GNU General Public License, and
27223 ~you are welcome to change it and/or distribute copies of it under
27224 ~ certain conditions.
27225 ~Type "show copying" to see the conditions.
27226 ~There is absolutely no warranty for GDB. Type "show warranty" for
27228 ~This GDB was configured as
27229 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27234 @subheading The @code{-list-features} Command
27235 @findex -list-features
27237 Returns a list of particular features of the MI protocol that
27238 this version of gdb implements. A feature can be a command,
27239 or a new field in an output of some command, or even an
27240 important bugfix. While a frontend can sometimes detect presence
27241 of a feature at runtime, it is easier to perform detection at debugger
27244 The command returns a list of strings, with each string naming an
27245 available feature. Each returned string is just a name, it does not
27246 have any internal structure. The list of possible feature names
27252 (gdb) -list-features
27253 ^done,result=["feature1","feature2"]
27256 The current list of features is:
27259 @item frozen-varobjs
27260 Indicates presence of the @code{-var-set-frozen} command, as well
27261 as possible presense of the @code{frozen} field in the output
27262 of @code{-varobj-create}.
27263 @item pending-breakpoints
27264 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27266 Indicates presence of Python scripting support, Python-based
27267 pretty-printing commands, and possible presence of the
27268 @samp{display_hint} field in the output of @code{-var-list-children}
27270 Indicates presence of the @code{-thread-info} command.
27274 @subheading The @code{-list-target-features} Command
27275 @findex -list-target-features
27277 Returns a list of particular features that are supported by the
27278 target. Those features affect the permitted MI commands, but
27279 unlike the features reported by the @code{-list-features} command, the
27280 features depend on which target GDB is using at the moment. Whenever
27281 a target can change, due to commands such as @code{-target-select},
27282 @code{-target-attach} or @code{-exec-run}, the list of target features
27283 may change, and the frontend should obtain it again.
27287 (gdb) -list-features
27288 ^done,result=["async"]
27291 The current list of features is:
27295 Indicates that the target is capable of asynchronous command
27296 execution, which means that @value{GDBN} will accept further commands
27297 while the target is running.
27301 @subheading The @code{-list-thread-groups} Command
27302 @findex -list-thread-groups
27304 @subheading Synopsis
27307 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27310 Lists thread groups (@pxref{Thread groups}). When a single thread
27311 group is passed as the argument, lists the children of that group.
27312 When several thread group are passed, lists information about those
27313 thread groups. Without any parameters, lists information about all
27314 top-level thread groups.
27316 Normally, thread groups that are being debugged are reported.
27317 With the @samp{--available} option, @value{GDBN} reports thread groups
27318 available on the target.
27320 The output of this command may have either a @samp{threads} result or
27321 a @samp{groups} result. The @samp{thread} result has a list of tuples
27322 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27323 Information}). The @samp{groups} result has a list of tuples as value,
27324 each tuple describing a thread group. If top-level groups are
27325 requested (that is, no parameter is passed), or when several groups
27326 are passed, the output always has a @samp{groups} result. The format
27327 of the @samp{group} result is described below.
27329 To reduce the number of roundtrips it's possible to list thread groups
27330 together with their children, by passing the @samp{--recurse} option
27331 and the recursion depth. Presently, only recursion depth of 1 is
27332 permitted. If this option is present, then every reported thread group
27333 will also include its children, either as @samp{group} or
27334 @samp{threads} field.
27336 In general, any combination of option and parameters is permitted, with
27337 the following caveats:
27341 When a single thread group is passed, the output will typically
27342 be the @samp{threads} result. Because threads may not contain
27343 anything, the @samp{recurse} option will be ignored.
27346 When the @samp{--available} option is passed, limited information may
27347 be available. In particular, the list of threads of a process might
27348 be inaccessible. Further, specifying specific thread groups might
27349 not give any performance advantage over listing all thread groups.
27350 The frontend should assume that @samp{-list-thread-groups --available}
27351 is always an expensive operation and cache the results.
27355 The @samp{groups} result is a list of tuples, where each tuple may
27356 have the following fields:
27360 Identifier of the thread group. This field is always present.
27361 The identifier is an opaque string; frontends should not try to
27362 convert it to an integer, even though it might look like one.
27365 The type of the thread group. At present, only @samp{process} is a
27369 The target-specific process identifier. This field is only present
27370 for thread groups of type @samp{process} and only if the process exists.
27373 The number of children this thread group has. This field may be
27374 absent for an available thread group.
27377 This field has a list of tuples as value, each tuple describing a
27378 thread. It may be present if the @samp{--recurse} option is
27379 specified, and it's actually possible to obtain the threads.
27382 This field is a list of integers, each identifying a core that one
27383 thread of the group is running on. This field may be absent if
27384 such information is not available.
27387 The name of the executable file that corresponds to this thread group.
27388 The field is only present for thread groups of type @samp{process},
27389 and only if there is a corresponding executable file.
27393 @subheading Example
27397 -list-thread-groups
27398 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
27399 -list-thread-groups 17
27400 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27401 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
27402 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27403 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
27404 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
27405 -list-thread-groups --available
27406 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
27407 -list-thread-groups --available --recurse 1
27408 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27409 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27410 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
27411 -list-thread-groups --available --recurse 1 17 18
27412 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27413 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27414 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
27418 @subheading The @code{-add-inferior} Command
27419 @findex -add-inferior
27421 @subheading Synopsis
27427 Creates a new inferior (@pxref{Inferiors and Programs}). The created
27428 inferior is not associated with any executable. Such association may
27429 be established with the @samp{-file-exec-and-symbols} command
27430 (@pxref{GDB/MI File Commands}). The command response has a single
27431 field, @samp{thread-group}, whose value is the identifier of the
27432 thread group corresponding to the new inferior.
27434 @subheading Example
27439 ^done,thread-group="i3"
27442 @subheading The @code{-interpreter-exec} Command
27443 @findex -interpreter-exec
27445 @subheading Synopsis
27448 -interpreter-exec @var{interpreter} @var{command}
27450 @anchor{-interpreter-exec}
27452 Execute the specified @var{command} in the given @var{interpreter}.
27454 @subheading @value{GDBN} Command
27456 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
27458 @subheading Example
27462 -interpreter-exec console "break main"
27463 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
27464 &"During symbol reading, bad structure-type format.\n"
27465 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
27470 @subheading The @code{-inferior-tty-set} Command
27471 @findex -inferior-tty-set
27473 @subheading Synopsis
27476 -inferior-tty-set /dev/pts/1
27479 Set terminal for future runs of the program being debugged.
27481 @subheading @value{GDBN} Command
27483 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
27485 @subheading Example
27489 -inferior-tty-set /dev/pts/1
27494 @subheading The @code{-inferior-tty-show} Command
27495 @findex -inferior-tty-show
27497 @subheading Synopsis
27503 Show terminal for future runs of program being debugged.
27505 @subheading @value{GDBN} Command
27507 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
27509 @subheading Example
27513 -inferior-tty-set /dev/pts/1
27517 ^done,inferior_tty_terminal="/dev/pts/1"
27521 @subheading The @code{-enable-timings} Command
27522 @findex -enable-timings
27524 @subheading Synopsis
27527 -enable-timings [yes | no]
27530 Toggle the printing of the wallclock, user and system times for an MI
27531 command as a field in its output. This command is to help frontend
27532 developers optimize the performance of their code. No argument is
27533 equivalent to @samp{yes}.
27535 @subheading @value{GDBN} Command
27539 @subheading Example
27547 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27548 addr="0x080484ed",func="main",file="myprog.c",
27549 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
27550 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
27558 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27559 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
27560 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
27561 fullname="/home/nickrob/myprog.c",line="73"@}
27566 @chapter @value{GDBN} Annotations
27568 This chapter describes annotations in @value{GDBN}. Annotations were
27569 designed to interface @value{GDBN} to graphical user interfaces or other
27570 similar programs which want to interact with @value{GDBN} at a
27571 relatively high level.
27573 The annotation mechanism has largely been superseded by @sc{gdb/mi}
27577 This is Edition @value{EDITION}, @value{DATE}.
27581 * Annotations Overview:: What annotations are; the general syntax.
27582 * Server Prefix:: Issuing a command without affecting user state.
27583 * Prompting:: Annotations marking @value{GDBN}'s need for input.
27584 * Errors:: Annotations for error messages.
27585 * Invalidation:: Some annotations describe things now invalid.
27586 * Annotations for Running::
27587 Whether the program is running, how it stopped, etc.
27588 * Source Annotations:: Annotations describing source code.
27591 @node Annotations Overview
27592 @section What is an Annotation?
27593 @cindex annotations
27595 Annotations start with a newline character, two @samp{control-z}
27596 characters, and the name of the annotation. If there is no additional
27597 information associated with this annotation, the name of the annotation
27598 is followed immediately by a newline. If there is additional
27599 information, the name of the annotation is followed by a space, the
27600 additional information, and a newline. The additional information
27601 cannot contain newline characters.
27603 Any output not beginning with a newline and two @samp{control-z}
27604 characters denotes literal output from @value{GDBN}. Currently there is
27605 no need for @value{GDBN} to output a newline followed by two
27606 @samp{control-z} characters, but if there was such a need, the
27607 annotations could be extended with an @samp{escape} annotation which
27608 means those three characters as output.
27610 The annotation @var{level}, which is specified using the
27611 @option{--annotate} command line option (@pxref{Mode Options}), controls
27612 how much information @value{GDBN} prints together with its prompt,
27613 values of expressions, source lines, and other types of output. Level 0
27614 is for no annotations, level 1 is for use when @value{GDBN} is run as a
27615 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
27616 for programs that control @value{GDBN}, and level 2 annotations have
27617 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
27618 Interface, annotate, GDB's Obsolete Annotations}).
27621 @kindex set annotate
27622 @item set annotate @var{level}
27623 The @value{GDBN} command @code{set annotate} sets the level of
27624 annotations to the specified @var{level}.
27626 @item show annotate
27627 @kindex show annotate
27628 Show the current annotation level.
27631 This chapter describes level 3 annotations.
27633 A simple example of starting up @value{GDBN} with annotations is:
27636 $ @kbd{gdb --annotate=3}
27638 Copyright 2003 Free Software Foundation, Inc.
27639 GDB is free software, covered by the GNU General Public License,
27640 and you are welcome to change it and/or distribute copies of it
27641 under certain conditions.
27642 Type "show copying" to see the conditions.
27643 There is absolutely no warranty for GDB. Type "show warranty"
27645 This GDB was configured as "i386-pc-linux-gnu"
27656 Here @samp{quit} is input to @value{GDBN}; the rest is output from
27657 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
27658 denotes a @samp{control-z} character) are annotations; the rest is
27659 output from @value{GDBN}.
27661 @node Server Prefix
27662 @section The Server Prefix
27663 @cindex server prefix
27665 If you prefix a command with @samp{server } then it will not affect
27666 the command history, nor will it affect @value{GDBN}'s notion of which
27667 command to repeat if @key{RET} is pressed on a line by itself. This
27668 means that commands can be run behind a user's back by a front-end in
27669 a transparent manner.
27671 The @code{server } prefix does not affect the recording of values into
27672 the value history; to print a value without recording it into the
27673 value history, use the @code{output} command instead of the
27674 @code{print} command.
27676 Using this prefix also disables confirmation requests
27677 (@pxref{confirmation requests}).
27680 @section Annotation for @value{GDBN} Input
27682 @cindex annotations for prompts
27683 When @value{GDBN} prompts for input, it annotates this fact so it is possible
27684 to know when to send output, when the output from a given command is
27687 Different kinds of input each have a different @dfn{input type}. Each
27688 input type has three annotations: a @code{pre-} annotation, which
27689 denotes the beginning of any prompt which is being output, a plain
27690 annotation, which denotes the end of the prompt, and then a @code{post-}
27691 annotation which denotes the end of any echo which may (or may not) be
27692 associated with the input. For example, the @code{prompt} input type
27693 features the following annotations:
27701 The input types are
27704 @findex pre-prompt annotation
27705 @findex prompt annotation
27706 @findex post-prompt annotation
27708 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
27710 @findex pre-commands annotation
27711 @findex commands annotation
27712 @findex post-commands annotation
27714 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
27715 command. The annotations are repeated for each command which is input.
27717 @findex pre-overload-choice annotation
27718 @findex overload-choice annotation
27719 @findex post-overload-choice annotation
27720 @item overload-choice
27721 When @value{GDBN} wants the user to select between various overloaded functions.
27723 @findex pre-query annotation
27724 @findex query annotation
27725 @findex post-query annotation
27727 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
27729 @findex pre-prompt-for-continue annotation
27730 @findex prompt-for-continue annotation
27731 @findex post-prompt-for-continue annotation
27732 @item prompt-for-continue
27733 When @value{GDBN} is asking the user to press return to continue. Note: Don't
27734 expect this to work well; instead use @code{set height 0} to disable
27735 prompting. This is because the counting of lines is buggy in the
27736 presence of annotations.
27741 @cindex annotations for errors, warnings and interrupts
27743 @findex quit annotation
27748 This annotation occurs right before @value{GDBN} responds to an interrupt.
27750 @findex error annotation
27755 This annotation occurs right before @value{GDBN} responds to an error.
27757 Quit and error annotations indicate that any annotations which @value{GDBN} was
27758 in the middle of may end abruptly. For example, if a
27759 @code{value-history-begin} annotation is followed by a @code{error}, one
27760 cannot expect to receive the matching @code{value-history-end}. One
27761 cannot expect not to receive it either, however; an error annotation
27762 does not necessarily mean that @value{GDBN} is immediately returning all the way
27765 @findex error-begin annotation
27766 A quit or error annotation may be preceded by
27772 Any output between that and the quit or error annotation is the error
27775 Warning messages are not yet annotated.
27776 @c If we want to change that, need to fix warning(), type_error(),
27777 @c range_error(), and possibly other places.
27780 @section Invalidation Notices
27782 @cindex annotations for invalidation messages
27783 The following annotations say that certain pieces of state may have
27787 @findex frames-invalid annotation
27788 @item ^Z^Zframes-invalid
27790 The frames (for example, output from the @code{backtrace} command) may
27793 @findex breakpoints-invalid annotation
27794 @item ^Z^Zbreakpoints-invalid
27796 The breakpoints may have changed. For example, the user just added or
27797 deleted a breakpoint.
27800 @node Annotations for Running
27801 @section Running the Program
27802 @cindex annotations for running programs
27804 @findex starting annotation
27805 @findex stopping annotation
27806 When the program starts executing due to a @value{GDBN} command such as
27807 @code{step} or @code{continue},
27813 is output. When the program stops,
27819 is output. Before the @code{stopped} annotation, a variety of
27820 annotations describe how the program stopped.
27823 @findex exited annotation
27824 @item ^Z^Zexited @var{exit-status}
27825 The program exited, and @var{exit-status} is the exit status (zero for
27826 successful exit, otherwise nonzero).
27828 @findex signalled annotation
27829 @findex signal-name annotation
27830 @findex signal-name-end annotation
27831 @findex signal-string annotation
27832 @findex signal-string-end annotation
27833 @item ^Z^Zsignalled
27834 The program exited with a signal. After the @code{^Z^Zsignalled}, the
27835 annotation continues:
27841 ^Z^Zsignal-name-end
27845 ^Z^Zsignal-string-end
27850 where @var{name} is the name of the signal, such as @code{SIGILL} or
27851 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
27852 as @code{Illegal Instruction} or @code{Segmentation fault}.
27853 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
27854 user's benefit and have no particular format.
27856 @findex signal annotation
27858 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
27859 just saying that the program received the signal, not that it was
27860 terminated with it.
27862 @findex breakpoint annotation
27863 @item ^Z^Zbreakpoint @var{number}
27864 The program hit breakpoint number @var{number}.
27866 @findex watchpoint annotation
27867 @item ^Z^Zwatchpoint @var{number}
27868 The program hit watchpoint number @var{number}.
27871 @node Source Annotations
27872 @section Displaying Source
27873 @cindex annotations for source display
27875 @findex source annotation
27876 The following annotation is used instead of displaying source code:
27879 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
27882 where @var{filename} is an absolute file name indicating which source
27883 file, @var{line} is the line number within that file (where 1 is the
27884 first line in the file), @var{character} is the character position
27885 within the file (where 0 is the first character in the file) (for most
27886 debug formats this will necessarily point to the beginning of a line),
27887 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
27888 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
27889 @var{addr} is the address in the target program associated with the
27890 source which is being displayed. @var{addr} is in the form @samp{0x}
27891 followed by one or more lowercase hex digits (note that this does not
27892 depend on the language).
27894 @node JIT Interface
27895 @chapter JIT Compilation Interface
27896 @cindex just-in-time compilation
27897 @cindex JIT compilation interface
27899 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
27900 interface. A JIT compiler is a program or library that generates native
27901 executable code at runtime and executes it, usually in order to achieve good
27902 performance while maintaining platform independence.
27904 Programs that use JIT compilation are normally difficult to debug because
27905 portions of their code are generated at runtime, instead of being loaded from
27906 object files, which is where @value{GDBN} normally finds the program's symbols
27907 and debug information. In order to debug programs that use JIT compilation,
27908 @value{GDBN} has an interface that allows the program to register in-memory
27909 symbol files with @value{GDBN} at runtime.
27911 If you are using @value{GDBN} to debug a program that uses this interface, then
27912 it should work transparently so long as you have not stripped the binary. If
27913 you are developing a JIT compiler, then the interface is documented in the rest
27914 of this chapter. At this time, the only known client of this interface is the
27917 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
27918 JIT compiler communicates with @value{GDBN} by writing data into a global
27919 variable and calling a fuction at a well-known symbol. When @value{GDBN}
27920 attaches, it reads a linked list of symbol files from the global variable to
27921 find existing code, and puts a breakpoint in the function so that it can find
27922 out about additional code.
27925 * Declarations:: Relevant C struct declarations
27926 * Registering Code:: Steps to register code
27927 * Unregistering Code:: Steps to unregister code
27931 @section JIT Declarations
27933 These are the relevant struct declarations that a C program should include to
27934 implement the interface:
27944 struct jit_code_entry
27946 struct jit_code_entry *next_entry;
27947 struct jit_code_entry *prev_entry;
27948 const char *symfile_addr;
27949 uint64_t symfile_size;
27952 struct jit_descriptor
27955 /* This type should be jit_actions_t, but we use uint32_t
27956 to be explicit about the bitwidth. */
27957 uint32_t action_flag;
27958 struct jit_code_entry *relevant_entry;
27959 struct jit_code_entry *first_entry;
27962 /* GDB puts a breakpoint in this function. */
27963 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
27965 /* Make sure to specify the version statically, because the
27966 debugger may check the version before we can set it. */
27967 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
27970 If the JIT is multi-threaded, then it is important that the JIT synchronize any
27971 modifications to this global data properly, which can easily be done by putting
27972 a global mutex around modifications to these structures.
27974 @node Registering Code
27975 @section Registering Code
27977 To register code with @value{GDBN}, the JIT should follow this protocol:
27981 Generate an object file in memory with symbols and other desired debug
27982 information. The file must include the virtual addresses of the sections.
27985 Create a code entry for the file, which gives the start and size of the symbol
27989 Add it to the linked list in the JIT descriptor.
27992 Point the relevant_entry field of the descriptor at the entry.
27995 Set @code{action_flag} to @code{JIT_REGISTER} and call
27996 @code{__jit_debug_register_code}.
27999 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28000 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28001 new code. However, the linked list must still be maintained in order to allow
28002 @value{GDBN} to attach to a running process and still find the symbol files.
28004 @node Unregistering Code
28005 @section Unregistering Code
28007 If code is freed, then the JIT should use the following protocol:
28011 Remove the code entry corresponding to the code from the linked list.
28014 Point the @code{relevant_entry} field of the descriptor at the code entry.
28017 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28018 @code{__jit_debug_register_code}.
28021 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28022 and the JIT will leak the memory used for the associated symbol files.
28025 @chapter Reporting Bugs in @value{GDBN}
28026 @cindex bugs in @value{GDBN}
28027 @cindex reporting bugs in @value{GDBN}
28029 Your bug reports play an essential role in making @value{GDBN} reliable.
28031 Reporting a bug may help you by bringing a solution to your problem, or it
28032 may not. But in any case the principal function of a bug report is to help
28033 the entire community by making the next version of @value{GDBN} work better. Bug
28034 reports are your contribution to the maintenance of @value{GDBN}.
28036 In order for a bug report to serve its purpose, you must include the
28037 information that enables us to fix the bug.
28040 * Bug Criteria:: Have you found a bug?
28041 * Bug Reporting:: How to report bugs
28045 @section Have You Found a Bug?
28046 @cindex bug criteria
28048 If you are not sure whether you have found a bug, here are some guidelines:
28051 @cindex fatal signal
28052 @cindex debugger crash
28053 @cindex crash of debugger
28055 If the debugger gets a fatal signal, for any input whatever, that is a
28056 @value{GDBN} bug. Reliable debuggers never crash.
28058 @cindex error on valid input
28060 If @value{GDBN} produces an error message for valid input, that is a
28061 bug. (Note that if you're cross debugging, the problem may also be
28062 somewhere in the connection to the target.)
28064 @cindex invalid input
28066 If @value{GDBN} does not produce an error message for invalid input,
28067 that is a bug. However, you should note that your idea of
28068 ``invalid input'' might be our idea of ``an extension'' or ``support
28069 for traditional practice''.
28072 If you are an experienced user of debugging tools, your suggestions
28073 for improvement of @value{GDBN} are welcome in any case.
28076 @node Bug Reporting
28077 @section How to Report Bugs
28078 @cindex bug reports
28079 @cindex @value{GDBN} bugs, reporting
28081 A number of companies and individuals offer support for @sc{gnu} products.
28082 If you obtained @value{GDBN} from a support organization, we recommend you
28083 contact that organization first.
28085 You can find contact information for many support companies and
28086 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28088 @c should add a web page ref...
28091 @ifset BUGURL_DEFAULT
28092 In any event, we also recommend that you submit bug reports for
28093 @value{GDBN}. The preferred method is to submit them directly using
28094 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28095 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28098 @strong{Do not send bug reports to @samp{info-gdb}, or to
28099 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28100 not want to receive bug reports. Those that do have arranged to receive
28103 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28104 serves as a repeater. The mailing list and the newsgroup carry exactly
28105 the same messages. Often people think of posting bug reports to the
28106 newsgroup instead of mailing them. This appears to work, but it has one
28107 problem which can be crucial: a newsgroup posting often lacks a mail
28108 path back to the sender. Thus, if we need to ask for more information,
28109 we may be unable to reach you. For this reason, it is better to send
28110 bug reports to the mailing list.
28112 @ifclear BUGURL_DEFAULT
28113 In any event, we also recommend that you submit bug reports for
28114 @value{GDBN} to @value{BUGURL}.
28118 The fundamental principle of reporting bugs usefully is this:
28119 @strong{report all the facts}. If you are not sure whether to state a
28120 fact or leave it out, state it!
28122 Often people omit facts because they think they know what causes the
28123 problem and assume that some details do not matter. Thus, you might
28124 assume that the name of the variable you use in an example does not matter.
28125 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28126 stray memory reference which happens to fetch from the location where that
28127 name is stored in memory; perhaps, if the name were different, the contents
28128 of that location would fool the debugger into doing the right thing despite
28129 the bug. Play it safe and give a specific, complete example. That is the
28130 easiest thing for you to do, and the most helpful.
28132 Keep in mind that the purpose of a bug report is to enable us to fix the
28133 bug. It may be that the bug has been reported previously, but neither
28134 you nor we can know that unless your bug report is complete and
28137 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28138 bell?'' Those bug reports are useless, and we urge everyone to
28139 @emph{refuse to respond to them} except to chide the sender to report
28142 To enable us to fix the bug, you should include all these things:
28146 The version of @value{GDBN}. @value{GDBN} announces it if you start
28147 with no arguments; you can also print it at any time using @code{show
28150 Without this, we will not know whether there is any point in looking for
28151 the bug in the current version of @value{GDBN}.
28154 The type of machine you are using, and the operating system name and
28158 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28159 ``@value{GCC}--2.8.1''.
28162 What compiler (and its version) was used to compile the program you are
28163 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28164 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28165 to get this information; for other compilers, see the documentation for
28169 The command arguments you gave the compiler to compile your example and
28170 observe the bug. For example, did you use @samp{-O}? To guarantee
28171 you will not omit something important, list them all. A copy of the
28172 Makefile (or the output from make) is sufficient.
28174 If we were to try to guess the arguments, we would probably guess wrong
28175 and then we might not encounter the bug.
28178 A complete input script, and all necessary source files, that will
28182 A description of what behavior you observe that you believe is
28183 incorrect. For example, ``It gets a fatal signal.''
28185 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28186 will certainly notice it. But if the bug is incorrect output, we might
28187 not notice unless it is glaringly wrong. You might as well not give us
28188 a chance to make a mistake.
28190 Even if the problem you experience is a fatal signal, you should still
28191 say so explicitly. Suppose something strange is going on, such as, your
28192 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28193 the C library on your system. (This has happened!) Your copy might
28194 crash and ours would not. If you told us to expect a crash, then when
28195 ours fails to crash, we would know that the bug was not happening for
28196 us. If you had not told us to expect a crash, then we would not be able
28197 to draw any conclusion from our observations.
28200 @cindex recording a session script
28201 To collect all this information, you can use a session recording program
28202 such as @command{script}, which is available on many Unix systems.
28203 Just run your @value{GDBN} session inside @command{script} and then
28204 include the @file{typescript} file with your bug report.
28206 Another way to record a @value{GDBN} session is to run @value{GDBN}
28207 inside Emacs and then save the entire buffer to a file.
28210 If you wish to suggest changes to the @value{GDBN} source, send us context
28211 diffs. If you even discuss something in the @value{GDBN} source, refer to
28212 it by context, not by line number.
28214 The line numbers in our development sources will not match those in your
28215 sources. Your line numbers would convey no useful information to us.
28219 Here are some things that are not necessary:
28223 A description of the envelope of the bug.
28225 Often people who encounter a bug spend a lot of time investigating
28226 which changes to the input file will make the bug go away and which
28227 changes will not affect it.
28229 This is often time consuming and not very useful, because the way we
28230 will find the bug is by running a single example under the debugger
28231 with breakpoints, not by pure deduction from a series of examples.
28232 We recommend that you save your time for something else.
28234 Of course, if you can find a simpler example to report @emph{instead}
28235 of the original one, that is a convenience for us. Errors in the
28236 output will be easier to spot, running under the debugger will take
28237 less time, and so on.
28239 However, simplification is not vital; if you do not want to do this,
28240 report the bug anyway and send us the entire test case you used.
28243 A patch for the bug.
28245 A patch for the bug does help us if it is a good one. But do not omit
28246 the necessary information, such as the test case, on the assumption that
28247 a patch is all we need. We might see problems with your patch and decide
28248 to fix the problem another way, or we might not understand it at all.
28250 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28251 construct an example that will make the program follow a certain path
28252 through the code. If you do not send us the example, we will not be able
28253 to construct one, so we will not be able to verify that the bug is fixed.
28255 And if we cannot understand what bug you are trying to fix, or why your
28256 patch should be an improvement, we will not install it. A test case will
28257 help us to understand.
28260 A guess about what the bug is or what it depends on.
28262 Such guesses are usually wrong. Even we cannot guess right about such
28263 things without first using the debugger to find the facts.
28266 @c The readline documentation is distributed with the readline code
28267 @c and consists of the two following files:
28269 @c inc-hist.texinfo
28270 @c Use -I with makeinfo to point to the appropriate directory,
28271 @c environment var TEXINPUTS with TeX.
28272 @include rluser.texi
28273 @include inc-hist.texinfo
28276 @node Formatting Documentation
28277 @appendix Formatting Documentation
28279 @cindex @value{GDBN} reference card
28280 @cindex reference card
28281 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28282 for printing with PostScript or Ghostscript, in the @file{gdb}
28283 subdirectory of the main source directory@footnote{In
28284 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28285 release.}. If you can use PostScript or Ghostscript with your printer,
28286 you can print the reference card immediately with @file{refcard.ps}.
28288 The release also includes the source for the reference card. You
28289 can format it, using @TeX{}, by typing:
28295 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28296 mode on US ``letter'' size paper;
28297 that is, on a sheet 11 inches wide by 8.5 inches
28298 high. You will need to specify this form of printing as an option to
28299 your @sc{dvi} output program.
28301 @cindex documentation
28303 All the documentation for @value{GDBN} comes as part of the machine-readable
28304 distribution. The documentation is written in Texinfo format, which is
28305 a documentation system that uses a single source file to produce both
28306 on-line information and a printed manual. You can use one of the Info
28307 formatting commands to create the on-line version of the documentation
28308 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28310 @value{GDBN} includes an already formatted copy of the on-line Info
28311 version of this manual in the @file{gdb} subdirectory. The main Info
28312 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28313 subordinate files matching @samp{gdb.info*} in the same directory. If
28314 necessary, you can print out these files, or read them with any editor;
28315 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28316 Emacs or the standalone @code{info} program, available as part of the
28317 @sc{gnu} Texinfo distribution.
28319 If you want to format these Info files yourself, you need one of the
28320 Info formatting programs, such as @code{texinfo-format-buffer} or
28323 If you have @code{makeinfo} installed, and are in the top level
28324 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28325 version @value{GDBVN}), you can make the Info file by typing:
28332 If you want to typeset and print copies of this manual, you need @TeX{},
28333 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28334 Texinfo definitions file.
28336 @TeX{} is a typesetting program; it does not print files directly, but
28337 produces output files called @sc{dvi} files. To print a typeset
28338 document, you need a program to print @sc{dvi} files. If your system
28339 has @TeX{} installed, chances are it has such a program. The precise
28340 command to use depends on your system; @kbd{lpr -d} is common; another
28341 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28342 require a file name without any extension or a @samp{.dvi} extension.
28344 @TeX{} also requires a macro definitions file called
28345 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28346 written in Texinfo format. On its own, @TeX{} cannot either read or
28347 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28348 and is located in the @file{gdb-@var{version-number}/texinfo}
28351 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28352 typeset and print this manual. First switch to the @file{gdb}
28353 subdirectory of the main source directory (for example, to
28354 @file{gdb-@value{GDBVN}/gdb}) and type:
28360 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28362 @node Installing GDB
28363 @appendix Installing @value{GDBN}
28364 @cindex installation
28367 * Requirements:: Requirements for building @value{GDBN}
28368 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28369 * Separate Objdir:: Compiling @value{GDBN} in another directory
28370 * Config Names:: Specifying names for hosts and targets
28371 * Configure Options:: Summary of options for configure
28372 * System-wide configuration:: Having a system-wide init file
28376 @section Requirements for Building @value{GDBN}
28377 @cindex building @value{GDBN}, requirements for
28379 Building @value{GDBN} requires various tools and packages to be available.
28380 Other packages will be used only if they are found.
28382 @heading Tools/Packages Necessary for Building @value{GDBN}
28384 @item ISO C90 compiler
28385 @value{GDBN} is written in ISO C90. It should be buildable with any
28386 working C90 compiler, e.g.@: GCC.
28390 @heading Tools/Packages Optional for Building @value{GDBN}
28394 @value{GDBN} can use the Expat XML parsing library. This library may be
28395 included with your operating system distribution; if it is not, you
28396 can get the latest version from @url{http://expat.sourceforge.net}.
28397 The @file{configure} script will search for this library in several
28398 standard locations; if it is installed in an unusual path, you can
28399 use the @option{--with-libexpat-prefix} option to specify its location.
28405 Remote protocol memory maps (@pxref{Memory Map Format})
28407 Target descriptions (@pxref{Target Descriptions})
28409 Remote shared library lists (@pxref{Library List Format})
28411 MS-Windows shared libraries (@pxref{Shared Libraries})
28415 @cindex compressed debug sections
28416 @value{GDBN} will use the @samp{zlib} library, if available, to read
28417 compressed debug sections. Some linkers, such as GNU gold, are capable
28418 of producing binaries with compressed debug sections. If @value{GDBN}
28419 is compiled with @samp{zlib}, it will be able to read the debug
28420 information in such binaries.
28422 The @samp{zlib} library is likely included with your operating system
28423 distribution; if it is not, you can get the latest version from
28424 @url{http://zlib.net}.
28427 @value{GDBN}'s features related to character sets (@pxref{Character
28428 Sets}) require a functioning @code{iconv} implementation. If you are
28429 on a GNU system, then this is provided by the GNU C Library. Some
28430 other systems also provide a working @code{iconv}.
28432 On systems with @code{iconv}, you can install GNU Libiconv. If you
28433 have previously installed Libiconv, you can use the
28434 @option{--with-libiconv-prefix} option to configure.
28436 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
28437 arrange to build Libiconv if a directory named @file{libiconv} appears
28438 in the top-most source directory. If Libiconv is built this way, and
28439 if the operating system does not provide a suitable @code{iconv}
28440 implementation, then the just-built library will automatically be used
28441 by @value{GDBN}. One easy way to set this up is to download GNU
28442 Libiconv, unpack it, and then rename the directory holding the
28443 Libiconv source code to @samp{libiconv}.
28446 @node Running Configure
28447 @section Invoking the @value{GDBN} @file{configure} Script
28448 @cindex configuring @value{GDBN}
28449 @value{GDBN} comes with a @file{configure} script that automates the process
28450 of preparing @value{GDBN} for installation; you can then use @code{make} to
28451 build the @code{gdb} program.
28453 @c irrelevant in info file; it's as current as the code it lives with.
28454 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
28455 look at the @file{README} file in the sources; we may have improved the
28456 installation procedures since publishing this manual.}
28459 The @value{GDBN} distribution includes all the source code you need for
28460 @value{GDBN} in a single directory, whose name is usually composed by
28461 appending the version number to @samp{gdb}.
28463 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
28464 @file{gdb-@value{GDBVN}} directory. That directory contains:
28467 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
28468 script for configuring @value{GDBN} and all its supporting libraries
28470 @item gdb-@value{GDBVN}/gdb
28471 the source specific to @value{GDBN} itself
28473 @item gdb-@value{GDBVN}/bfd
28474 source for the Binary File Descriptor library
28476 @item gdb-@value{GDBVN}/include
28477 @sc{gnu} include files
28479 @item gdb-@value{GDBVN}/libiberty
28480 source for the @samp{-liberty} free software library
28482 @item gdb-@value{GDBVN}/opcodes
28483 source for the library of opcode tables and disassemblers
28485 @item gdb-@value{GDBVN}/readline
28486 source for the @sc{gnu} command-line interface
28488 @item gdb-@value{GDBVN}/glob
28489 source for the @sc{gnu} filename pattern-matching subroutine
28491 @item gdb-@value{GDBVN}/mmalloc
28492 source for the @sc{gnu} memory-mapped malloc package
28495 The simplest way to configure and build @value{GDBN} is to run @file{configure}
28496 from the @file{gdb-@var{version-number}} source directory, which in
28497 this example is the @file{gdb-@value{GDBVN}} directory.
28499 First switch to the @file{gdb-@var{version-number}} source directory
28500 if you are not already in it; then run @file{configure}. Pass the
28501 identifier for the platform on which @value{GDBN} will run as an
28507 cd gdb-@value{GDBVN}
28508 ./configure @var{host}
28513 where @var{host} is an identifier such as @samp{sun4} or
28514 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
28515 (You can often leave off @var{host}; @file{configure} tries to guess the
28516 correct value by examining your system.)
28518 Running @samp{configure @var{host}} and then running @code{make} builds the
28519 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
28520 libraries, then @code{gdb} itself. The configured source files, and the
28521 binaries, are left in the corresponding source directories.
28524 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
28525 system does not recognize this automatically when you run a different
28526 shell, you may need to run @code{sh} on it explicitly:
28529 sh configure @var{host}
28532 If you run @file{configure} from a directory that contains source
28533 directories for multiple libraries or programs, such as the
28534 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
28536 creates configuration files for every directory level underneath (unless
28537 you tell it not to, with the @samp{--norecursion} option).
28539 You should run the @file{configure} script from the top directory in the
28540 source tree, the @file{gdb-@var{version-number}} directory. If you run
28541 @file{configure} from one of the subdirectories, you will configure only
28542 that subdirectory. That is usually not what you want. In particular,
28543 if you run the first @file{configure} from the @file{gdb} subdirectory
28544 of the @file{gdb-@var{version-number}} directory, you will omit the
28545 configuration of @file{bfd}, @file{readline}, and other sibling
28546 directories of the @file{gdb} subdirectory. This leads to build errors
28547 about missing include files such as @file{bfd/bfd.h}.
28549 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
28550 However, you should make sure that the shell on your path (named by
28551 the @samp{SHELL} environment variable) is publicly readable. Remember
28552 that @value{GDBN} uses the shell to start your program---some systems refuse to
28553 let @value{GDBN} debug child processes whose programs are not readable.
28555 @node Separate Objdir
28556 @section Compiling @value{GDBN} in Another Directory
28558 If you want to run @value{GDBN} versions for several host or target machines,
28559 you need a different @code{gdb} compiled for each combination of
28560 host and target. @file{configure} is designed to make this easy by
28561 allowing you to generate each configuration in a separate subdirectory,
28562 rather than in the source directory. If your @code{make} program
28563 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
28564 @code{make} in each of these directories builds the @code{gdb}
28565 program specified there.
28567 To build @code{gdb} in a separate directory, run @file{configure}
28568 with the @samp{--srcdir} option to specify where to find the source.
28569 (You also need to specify a path to find @file{configure}
28570 itself from your working directory. If the path to @file{configure}
28571 would be the same as the argument to @samp{--srcdir}, you can leave out
28572 the @samp{--srcdir} option; it is assumed.)
28574 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
28575 separate directory for a Sun 4 like this:
28579 cd gdb-@value{GDBVN}
28582 ../gdb-@value{GDBVN}/configure sun4
28587 When @file{configure} builds a configuration using a remote source
28588 directory, it creates a tree for the binaries with the same structure
28589 (and using the same names) as the tree under the source directory. In
28590 the example, you'd find the Sun 4 library @file{libiberty.a} in the
28591 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
28592 @file{gdb-sun4/gdb}.
28594 Make sure that your path to the @file{configure} script has just one
28595 instance of @file{gdb} in it. If your path to @file{configure} looks
28596 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
28597 one subdirectory of @value{GDBN}, not the whole package. This leads to
28598 build errors about missing include files such as @file{bfd/bfd.h}.
28600 One popular reason to build several @value{GDBN} configurations in separate
28601 directories is to configure @value{GDBN} for cross-compiling (where
28602 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
28603 programs that run on another machine---the @dfn{target}).
28604 You specify a cross-debugging target by
28605 giving the @samp{--target=@var{target}} option to @file{configure}.
28607 When you run @code{make} to build a program or library, you must run
28608 it in a configured directory---whatever directory you were in when you
28609 called @file{configure} (or one of its subdirectories).
28611 The @code{Makefile} that @file{configure} generates in each source
28612 directory also runs recursively. If you type @code{make} in a source
28613 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
28614 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
28615 will build all the required libraries, and then build GDB.
28617 When you have multiple hosts or targets configured in separate
28618 directories, you can run @code{make} on them in parallel (for example,
28619 if they are NFS-mounted on each of the hosts); they will not interfere
28623 @section Specifying Names for Hosts and Targets
28625 The specifications used for hosts and targets in the @file{configure}
28626 script are based on a three-part naming scheme, but some short predefined
28627 aliases are also supported. The full naming scheme encodes three pieces
28628 of information in the following pattern:
28631 @var{architecture}-@var{vendor}-@var{os}
28634 For example, you can use the alias @code{sun4} as a @var{host} argument,
28635 or as the value for @var{target} in a @code{--target=@var{target}}
28636 option. The equivalent full name is @samp{sparc-sun-sunos4}.
28638 The @file{configure} script accompanying @value{GDBN} does not provide
28639 any query facility to list all supported host and target names or
28640 aliases. @file{configure} calls the Bourne shell script
28641 @code{config.sub} to map abbreviations to full names; you can read the
28642 script, if you wish, or you can use it to test your guesses on
28643 abbreviations---for example:
28646 % sh config.sub i386-linux
28648 % sh config.sub alpha-linux
28649 alpha-unknown-linux-gnu
28650 % sh config.sub hp9k700
28652 % sh config.sub sun4
28653 sparc-sun-sunos4.1.1
28654 % sh config.sub sun3
28655 m68k-sun-sunos4.1.1
28656 % sh config.sub i986v
28657 Invalid configuration `i986v': machine `i986v' not recognized
28661 @code{config.sub} is also distributed in the @value{GDBN} source
28662 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
28664 @node Configure Options
28665 @section @file{configure} Options
28667 Here is a summary of the @file{configure} options and arguments that
28668 are most often useful for building @value{GDBN}. @file{configure} also has
28669 several other options not listed here. @inforef{What Configure
28670 Does,,configure.info}, for a full explanation of @file{configure}.
28673 configure @r{[}--help@r{]}
28674 @r{[}--prefix=@var{dir}@r{]}
28675 @r{[}--exec-prefix=@var{dir}@r{]}
28676 @r{[}--srcdir=@var{dirname}@r{]}
28677 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
28678 @r{[}--target=@var{target}@r{]}
28683 You may introduce options with a single @samp{-} rather than
28684 @samp{--} if you prefer; but you may abbreviate option names if you use
28689 Display a quick summary of how to invoke @file{configure}.
28691 @item --prefix=@var{dir}
28692 Configure the source to install programs and files under directory
28695 @item --exec-prefix=@var{dir}
28696 Configure the source to install programs under directory
28699 @c avoid splitting the warning from the explanation:
28701 @item --srcdir=@var{dirname}
28702 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
28703 @code{make} that implements the @code{VPATH} feature.}@*
28704 Use this option to make configurations in directories separate from the
28705 @value{GDBN} source directories. Among other things, you can use this to
28706 build (or maintain) several configurations simultaneously, in separate
28707 directories. @file{configure} writes configuration-specific files in
28708 the current directory, but arranges for them to use the source in the
28709 directory @var{dirname}. @file{configure} creates directories under
28710 the working directory in parallel to the source directories below
28713 @item --norecursion
28714 Configure only the directory level where @file{configure} is executed; do not
28715 propagate configuration to subdirectories.
28717 @item --target=@var{target}
28718 Configure @value{GDBN} for cross-debugging programs running on the specified
28719 @var{target}. Without this option, @value{GDBN} is configured to debug
28720 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
28722 There is no convenient way to generate a list of all available targets.
28724 @item @var{host} @dots{}
28725 Configure @value{GDBN} to run on the specified @var{host}.
28727 There is no convenient way to generate a list of all available hosts.
28730 There are many other options available as well, but they are generally
28731 needed for special purposes only.
28733 @node System-wide configuration
28734 @section System-wide configuration and settings
28735 @cindex system-wide init file
28737 @value{GDBN} can be configured to have a system-wide init file;
28738 this file will be read and executed at startup (@pxref{Startup, , What
28739 @value{GDBN} does during startup}).
28741 Here is the corresponding configure option:
28744 @item --with-system-gdbinit=@var{file}
28745 Specify that the default location of the system-wide init file is
28749 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
28750 it may be subject to relocation. Two possible cases:
28754 If the default location of this init file contains @file{$prefix},
28755 it will be subject to relocation. Suppose that the configure options
28756 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
28757 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
28758 init file is looked for as @file{$install/etc/gdbinit} instead of
28759 @file{$prefix/etc/gdbinit}.
28762 By contrast, if the default location does not contain the prefix,
28763 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
28764 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
28765 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
28766 wherever @value{GDBN} is installed.
28769 @node Maintenance Commands
28770 @appendix Maintenance Commands
28771 @cindex maintenance commands
28772 @cindex internal commands
28774 In addition to commands intended for @value{GDBN} users, @value{GDBN}
28775 includes a number of commands intended for @value{GDBN} developers,
28776 that are not documented elsewhere in this manual. These commands are
28777 provided here for reference. (For commands that turn on debugging
28778 messages, see @ref{Debugging Output}.)
28781 @kindex maint agent
28782 @kindex maint agent-eval
28783 @item maint agent @var{expression}
28784 @itemx maint agent-eval @var{expression}
28785 Translate the given @var{expression} into remote agent bytecodes.
28786 This command is useful for debugging the Agent Expression mechanism
28787 (@pxref{Agent Expressions}). The @samp{agent} version produces an
28788 expression useful for data collection, such as by tracepoints, while
28789 @samp{maint agent-eval} produces an expression that evaluates directly
28790 to a result. For instance, a collection expression for @code{globa +
28791 globb} will include bytecodes to record four bytes of memory at each
28792 of the addresses of @code{globa} and @code{globb}, while discarding
28793 the result of the addition, while an evaluation expression will do the
28794 addition and return the sum.
28796 @kindex maint info breakpoints
28797 @item @anchor{maint info breakpoints}maint info breakpoints
28798 Using the same format as @samp{info breakpoints}, display both the
28799 breakpoints you've set explicitly, and those @value{GDBN} is using for
28800 internal purposes. Internal breakpoints are shown with negative
28801 breakpoint numbers. The type column identifies what kind of breakpoint
28806 Normal, explicitly set breakpoint.
28809 Normal, explicitly set watchpoint.
28812 Internal breakpoint, used to handle correctly stepping through
28813 @code{longjmp} calls.
28815 @item longjmp resume
28816 Internal breakpoint at the target of a @code{longjmp}.
28819 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
28822 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
28825 Shared library events.
28829 @kindex set displaced-stepping
28830 @kindex show displaced-stepping
28831 @cindex displaced stepping support
28832 @cindex out-of-line single-stepping
28833 @item set displaced-stepping
28834 @itemx show displaced-stepping
28835 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
28836 if the target supports it. Displaced stepping is a way to single-step
28837 over breakpoints without removing them from the inferior, by executing
28838 an out-of-line copy of the instruction that was originally at the
28839 breakpoint location. It is also known as out-of-line single-stepping.
28842 @item set displaced-stepping on
28843 If the target architecture supports it, @value{GDBN} will use
28844 displaced stepping to step over breakpoints.
28846 @item set displaced-stepping off
28847 @value{GDBN} will not use displaced stepping to step over breakpoints,
28848 even if such is supported by the target architecture.
28850 @cindex non-stop mode, and @samp{set displaced-stepping}
28851 @item set displaced-stepping auto
28852 This is the default mode. @value{GDBN} will use displaced stepping
28853 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
28854 architecture supports displaced stepping.
28857 @kindex maint check-symtabs
28858 @item maint check-symtabs
28859 Check the consistency of psymtabs and symtabs.
28861 @kindex maint cplus first_component
28862 @item maint cplus first_component @var{name}
28863 Print the first C@t{++} class/namespace component of @var{name}.
28865 @kindex maint cplus namespace
28866 @item maint cplus namespace
28867 Print the list of possible C@t{++} namespaces.
28869 @kindex maint demangle
28870 @item maint demangle @var{name}
28871 Demangle a C@t{++} or Objective-C mangled @var{name}.
28873 @kindex maint deprecate
28874 @kindex maint undeprecate
28875 @cindex deprecated commands
28876 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
28877 @itemx maint undeprecate @var{command}
28878 Deprecate or undeprecate the named @var{command}. Deprecated commands
28879 cause @value{GDBN} to issue a warning when you use them. The optional
28880 argument @var{replacement} says which newer command should be used in
28881 favor of the deprecated one; if it is given, @value{GDBN} will mention
28882 the replacement as part of the warning.
28884 @kindex maint dump-me
28885 @item maint dump-me
28886 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
28887 Cause a fatal signal in the debugger and force it to dump its core.
28888 This is supported only on systems which support aborting a program
28889 with the @code{SIGQUIT} signal.
28891 @kindex maint internal-error
28892 @kindex maint internal-warning
28893 @item maint internal-error @r{[}@var{message-text}@r{]}
28894 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
28895 Cause @value{GDBN} to call the internal function @code{internal_error}
28896 or @code{internal_warning} and hence behave as though an internal error
28897 or internal warning has been detected. In addition to reporting the
28898 internal problem, these functions give the user the opportunity to
28899 either quit @value{GDBN} or create a core file of the current
28900 @value{GDBN} session.
28902 These commands take an optional parameter @var{message-text} that is
28903 used as the text of the error or warning message.
28905 Here's an example of using @code{internal-error}:
28908 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
28909 @dots{}/maint.c:121: internal-error: testing, 1, 2
28910 A problem internal to GDB has been detected. Further
28911 debugging may prove unreliable.
28912 Quit this debugging session? (y or n) @kbd{n}
28913 Create a core file? (y or n) @kbd{n}
28917 @cindex @value{GDBN} internal error
28918 @cindex internal errors, control of @value{GDBN} behavior
28920 @kindex maint set internal-error
28921 @kindex maint show internal-error
28922 @kindex maint set internal-warning
28923 @kindex maint show internal-warning
28924 @item maint set internal-error @var{action} [ask|yes|no]
28925 @itemx maint show internal-error @var{action}
28926 @itemx maint set internal-warning @var{action} [ask|yes|no]
28927 @itemx maint show internal-warning @var{action}
28928 When @value{GDBN} reports an internal problem (error or warning) it
28929 gives the user the opportunity to both quit @value{GDBN} and create a
28930 core file of the current @value{GDBN} session. These commands let you
28931 override the default behaviour for each particular @var{action},
28932 described in the table below.
28936 You can specify that @value{GDBN} should always (yes) or never (no)
28937 quit. The default is to ask the user what to do.
28940 You can specify that @value{GDBN} should always (yes) or never (no)
28941 create a core file. The default is to ask the user what to do.
28944 @kindex maint packet
28945 @item maint packet @var{text}
28946 If @value{GDBN} is talking to an inferior via the serial protocol,
28947 then this command sends the string @var{text} to the inferior, and
28948 displays the response packet. @value{GDBN} supplies the initial
28949 @samp{$} character, the terminating @samp{#} character, and the
28952 @kindex maint print architecture
28953 @item maint print architecture @r{[}@var{file}@r{]}
28954 Print the entire architecture configuration. The optional argument
28955 @var{file} names the file where the output goes.
28957 @kindex maint print c-tdesc
28958 @item maint print c-tdesc
28959 Print the current target description (@pxref{Target Descriptions}) as
28960 a C source file. The created source file can be used in @value{GDBN}
28961 when an XML parser is not available to parse the description.
28963 @kindex maint print dummy-frames
28964 @item maint print dummy-frames
28965 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
28968 (@value{GDBP}) @kbd{b add}
28970 (@value{GDBP}) @kbd{print add(2,3)}
28971 Breakpoint 2, add (a=2, b=3) at @dots{}
28973 The program being debugged stopped while in a function called from GDB.
28975 (@value{GDBP}) @kbd{maint print dummy-frames}
28976 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
28977 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
28978 call_lo=0x01014000 call_hi=0x01014001
28982 Takes an optional file parameter.
28984 @kindex maint print registers
28985 @kindex maint print raw-registers
28986 @kindex maint print cooked-registers
28987 @kindex maint print register-groups
28988 @item maint print registers @r{[}@var{file}@r{]}
28989 @itemx maint print raw-registers @r{[}@var{file}@r{]}
28990 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
28991 @itemx maint print register-groups @r{[}@var{file}@r{]}
28992 Print @value{GDBN}'s internal register data structures.
28994 The command @code{maint print raw-registers} includes the contents of
28995 the raw register cache; the command @code{maint print cooked-registers}
28996 includes the (cooked) value of all registers; and the command
28997 @code{maint print register-groups} includes the groups that each
28998 register is a member of. @xref{Registers,, Registers, gdbint,
28999 @value{GDBN} Internals}.
29001 These commands take an optional parameter, a file name to which to
29002 write the information.
29004 @kindex maint print reggroups
29005 @item maint print reggroups @r{[}@var{file}@r{]}
29006 Print @value{GDBN}'s internal register group data structures. The
29007 optional argument @var{file} tells to what file to write the
29010 The register groups info looks like this:
29013 (@value{GDBP}) @kbd{maint print reggroups}
29026 This command forces @value{GDBN} to flush its internal register cache.
29028 @kindex maint print objfiles
29029 @cindex info for known object files
29030 @item maint print objfiles
29031 Print a dump of all known object files. For each object file, this
29032 command prints its name, address in memory, and all of its psymtabs
29035 @kindex maint print statistics
29036 @cindex bcache statistics
29037 @item maint print statistics
29038 This command prints, for each object file in the program, various data
29039 about that object file followed by the byte cache (@dfn{bcache})
29040 statistics for the object file. The objfile data includes the number
29041 of minimal, partial, full, and stabs symbols, the number of types
29042 defined by the objfile, the number of as yet unexpanded psym tables,
29043 the number of line tables and string tables, and the amount of memory
29044 used by the various tables. The bcache statistics include the counts,
29045 sizes, and counts of duplicates of all and unique objects, max,
29046 average, and median entry size, total memory used and its overhead and
29047 savings, and various measures of the hash table size and chain
29050 @kindex maint print target-stack
29051 @cindex target stack description
29052 @item maint print target-stack
29053 A @dfn{target} is an interface between the debugger and a particular
29054 kind of file or process. Targets can be stacked in @dfn{strata},
29055 so that more than one target can potentially respond to a request.
29056 In particular, memory accesses will walk down the stack of targets
29057 until they find a target that is interested in handling that particular
29060 This command prints a short description of each layer that was pushed on
29061 the @dfn{target stack}, starting from the top layer down to the bottom one.
29063 @kindex maint print type
29064 @cindex type chain of a data type
29065 @item maint print type @var{expr}
29066 Print the type chain for a type specified by @var{expr}. The argument
29067 can be either a type name or a symbol. If it is a symbol, the type of
29068 that symbol is described. The type chain produced by this command is
29069 a recursive definition of the data type as stored in @value{GDBN}'s
29070 data structures, including its flags and contained types.
29072 @kindex maint set dwarf2 max-cache-age
29073 @kindex maint show dwarf2 max-cache-age
29074 @item maint set dwarf2 max-cache-age
29075 @itemx maint show dwarf2 max-cache-age
29076 Control the DWARF 2 compilation unit cache.
29078 @cindex DWARF 2 compilation units cache
29079 In object files with inter-compilation-unit references, such as those
29080 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29081 reader needs to frequently refer to previously read compilation units.
29082 This setting controls how long a compilation unit will remain in the
29083 cache if it is not referenced. A higher limit means that cached
29084 compilation units will be stored in memory longer, and more total
29085 memory will be used. Setting it to zero disables caching, which will
29086 slow down @value{GDBN} startup, but reduce memory consumption.
29088 @kindex maint set profile
29089 @kindex maint show profile
29090 @cindex profiling GDB
29091 @item maint set profile
29092 @itemx maint show profile
29093 Control profiling of @value{GDBN}.
29095 Profiling will be disabled until you use the @samp{maint set profile}
29096 command to enable it. When you enable profiling, the system will begin
29097 collecting timing and execution count data; when you disable profiling or
29098 exit @value{GDBN}, the results will be written to a log file. Remember that
29099 if you use profiling, @value{GDBN} will overwrite the profiling log file
29100 (often called @file{gmon.out}). If you have a record of important profiling
29101 data in a @file{gmon.out} file, be sure to move it to a safe location.
29103 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29104 compiled with the @samp{-pg} compiler option.
29106 @kindex maint set show-debug-regs
29107 @kindex maint show show-debug-regs
29108 @cindex hardware debug registers
29109 @item maint set show-debug-regs
29110 @itemx maint show show-debug-regs
29111 Control whether to show variables that mirror the hardware debug
29112 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29113 enabled, the debug registers values are shown when @value{GDBN} inserts or
29114 removes a hardware breakpoint or watchpoint, and when the inferior
29115 triggers a hardware-assisted breakpoint or watchpoint.
29117 @kindex maint space
29118 @cindex memory used by commands
29120 Control whether to display memory usage for each command. If set to a
29121 nonzero value, @value{GDBN} will display how much memory each command
29122 took, following the command's own output. This can also be requested
29123 by invoking @value{GDBN} with the @option{--statistics} command-line
29124 switch (@pxref{Mode Options}).
29127 @cindex time of command execution
29129 Control whether to display the execution time for each command. If
29130 set to a nonzero value, @value{GDBN} will display how much time it
29131 took to execute each command, following the command's own output.
29132 The time is not printed for the commands that run the target, since
29133 there's no mechanism currently to compute how much time was spend
29134 by @value{GDBN} and how much time was spend by the program been debugged.
29135 it's not possibly currently
29136 This can also be requested by invoking @value{GDBN} with the
29137 @option{--statistics} command-line switch (@pxref{Mode Options}).
29139 @kindex maint translate-address
29140 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29141 Find the symbol stored at the location specified by the address
29142 @var{addr} and an optional section name @var{section}. If found,
29143 @value{GDBN} prints the name of the closest symbol and an offset from
29144 the symbol's location to the specified address. This is similar to
29145 the @code{info address} command (@pxref{Symbols}), except that this
29146 command also allows to find symbols in other sections.
29148 If section was not specified, the section in which the symbol was found
29149 is also printed. For dynamically linked executables, the name of
29150 executable or shared library containing the symbol is printed as well.
29154 The following command is useful for non-interactive invocations of
29155 @value{GDBN}, such as in the test suite.
29158 @item set watchdog @var{nsec}
29159 @kindex set watchdog
29160 @cindex watchdog timer
29161 @cindex timeout for commands
29162 Set the maximum number of seconds @value{GDBN} will wait for the
29163 target operation to finish. If this time expires, @value{GDBN}
29164 reports and error and the command is aborted.
29166 @item show watchdog
29167 Show the current setting of the target wait timeout.
29170 @node Remote Protocol
29171 @appendix @value{GDBN} Remote Serial Protocol
29176 * Stop Reply Packets::
29177 * General Query Packets::
29178 * Architecture-Specific Protocol Details::
29179 * Tracepoint Packets::
29180 * Host I/O Packets::
29182 * Notification Packets::
29183 * Remote Non-Stop::
29184 * Packet Acknowledgment::
29186 * File-I/O Remote Protocol Extension::
29187 * Library List Format::
29188 * Memory Map Format::
29189 * Thread List Format::
29195 There may be occasions when you need to know something about the
29196 protocol---for example, if there is only one serial port to your target
29197 machine, you might want your program to do something special if it
29198 recognizes a packet meant for @value{GDBN}.
29200 In the examples below, @samp{->} and @samp{<-} are used to indicate
29201 transmitted and received data, respectively.
29203 @cindex protocol, @value{GDBN} remote serial
29204 @cindex serial protocol, @value{GDBN} remote
29205 @cindex remote serial protocol
29206 All @value{GDBN} commands and responses (other than acknowledgments
29207 and notifications, see @ref{Notification Packets}) are sent as a
29208 @var{packet}. A @var{packet} is introduced with the character
29209 @samp{$}, the actual @var{packet-data}, and the terminating character
29210 @samp{#} followed by a two-digit @var{checksum}:
29213 @code{$}@var{packet-data}@code{#}@var{checksum}
29217 @cindex checksum, for @value{GDBN} remote
29219 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29220 characters between the leading @samp{$} and the trailing @samp{#} (an
29221 eight bit unsigned checksum).
29223 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29224 specification also included an optional two-digit @var{sequence-id}:
29227 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29230 @cindex sequence-id, for @value{GDBN} remote
29232 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29233 has never output @var{sequence-id}s. Stubs that handle packets added
29234 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29236 When either the host or the target machine receives a packet, the first
29237 response expected is an acknowledgment: either @samp{+} (to indicate
29238 the package was received correctly) or @samp{-} (to request
29242 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29247 The @samp{+}/@samp{-} acknowledgments can be disabled
29248 once a connection is established.
29249 @xref{Packet Acknowledgment}, for details.
29251 The host (@value{GDBN}) sends @var{command}s, and the target (the
29252 debugging stub incorporated in your program) sends a @var{response}. In
29253 the case of step and continue @var{command}s, the response is only sent
29254 when the operation has completed, and the target has again stopped all
29255 threads in all attached processes. This is the default all-stop mode
29256 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29257 execution mode; see @ref{Remote Non-Stop}, for details.
29259 @var{packet-data} consists of a sequence of characters with the
29260 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29263 @cindex remote protocol, field separator
29264 Fields within the packet should be separated using @samp{,} @samp{;} or
29265 @samp{:}. Except where otherwise noted all numbers are represented in
29266 @sc{hex} with leading zeros suppressed.
29268 Implementors should note that prior to @value{GDBN} 5.0, the character
29269 @samp{:} could not appear as the third character in a packet (as it
29270 would potentially conflict with the @var{sequence-id}).
29272 @cindex remote protocol, binary data
29273 @anchor{Binary Data}
29274 Binary data in most packets is encoded either as two hexadecimal
29275 digits per byte of binary data. This allowed the traditional remote
29276 protocol to work over connections which were only seven-bit clean.
29277 Some packets designed more recently assume an eight-bit clean
29278 connection, and use a more efficient encoding to send and receive
29281 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29282 as an escape character. Any escaped byte is transmitted as the escape
29283 character followed by the original character XORed with @code{0x20}.
29284 For example, the byte @code{0x7d} would be transmitted as the two
29285 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29286 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29287 @samp{@}}) must always be escaped. Responses sent by the stub
29288 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29289 is not interpreted as the start of a run-length encoded sequence
29292 Response @var{data} can be run-length encoded to save space.
29293 Run-length encoding replaces runs of identical characters with one
29294 instance of the repeated character, followed by a @samp{*} and a
29295 repeat count. The repeat count is itself sent encoded, to avoid
29296 binary characters in @var{data}: a value of @var{n} is sent as
29297 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29298 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29299 code 32) for a repeat count of 3. (This is because run-length
29300 encoding starts to win for counts 3 or more.) Thus, for example,
29301 @samp{0* } is a run-length encoding of ``0000'': the space character
29302 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29305 The printable characters @samp{#} and @samp{$} or with a numeric value
29306 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29307 seven repeats (@samp{$}) can be expanded using a repeat count of only
29308 five (@samp{"}). For example, @samp{00000000} can be encoded as
29311 The error response returned for some packets includes a two character
29312 error number. That number is not well defined.
29314 @cindex empty response, for unsupported packets
29315 For any @var{command} not supported by the stub, an empty response
29316 (@samp{$#00}) should be returned. That way it is possible to extend the
29317 protocol. A newer @value{GDBN} can tell if a packet is supported based
29320 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29321 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29327 The following table provides a complete list of all currently defined
29328 @var{command}s and their corresponding response @var{data}.
29329 @xref{File-I/O Remote Protocol Extension}, for details about the File
29330 I/O extension of the remote protocol.
29332 Each packet's description has a template showing the packet's overall
29333 syntax, followed by an explanation of the packet's meaning. We
29334 include spaces in some of the templates for clarity; these are not
29335 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29336 separate its components. For example, a template like @samp{foo
29337 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29338 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29339 @var{baz}. @value{GDBN} does not transmit a space character between the
29340 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29343 @cindex @var{thread-id}, in remote protocol
29344 @anchor{thread-id syntax}
29345 Several packets and replies include a @var{thread-id} field to identify
29346 a thread. Normally these are positive numbers with a target-specific
29347 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29348 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29351 In addition, the remote protocol supports a multiprocess feature in
29352 which the @var{thread-id} syntax is extended to optionally include both
29353 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29354 The @var{pid} (process) and @var{tid} (thread) components each have the
29355 format described above: a positive number with target-specific
29356 interpretation formatted as a big-endian hex string, literal @samp{-1}
29357 to indicate all processes or threads (respectively), or @samp{0} to
29358 indicate an arbitrary process or thread. Specifying just a process, as
29359 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29360 error to specify all processes but a specific thread, such as
29361 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
29362 for those packets and replies explicitly documented to include a process
29363 ID, rather than a @var{thread-id}.
29365 The multiprocess @var{thread-id} syntax extensions are only used if both
29366 @value{GDBN} and the stub report support for the @samp{multiprocess}
29367 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
29370 Note that all packet forms beginning with an upper- or lower-case
29371 letter, other than those described here, are reserved for future use.
29373 Here are the packet descriptions.
29378 @cindex @samp{!} packet
29379 @anchor{extended mode}
29380 Enable extended mode. In extended mode, the remote server is made
29381 persistent. The @samp{R} packet is used to restart the program being
29387 The remote target both supports and has enabled extended mode.
29391 @cindex @samp{?} packet
29392 Indicate the reason the target halted. The reply is the same as for
29393 step and continue. This packet has a special interpretation when the
29394 target is in non-stop mode; see @ref{Remote Non-Stop}.
29397 @xref{Stop Reply Packets}, for the reply specifications.
29399 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
29400 @cindex @samp{A} packet
29401 Initialized @code{argv[]} array passed into program. @var{arglen}
29402 specifies the number of bytes in the hex encoded byte stream
29403 @var{arg}. See @code{gdbserver} for more details.
29408 The arguments were set.
29414 @cindex @samp{b} packet
29415 (Don't use this packet; its behavior is not well-defined.)
29416 Change the serial line speed to @var{baud}.
29418 JTC: @emph{When does the transport layer state change? When it's
29419 received, or after the ACK is transmitted. In either case, there are
29420 problems if the command or the acknowledgment packet is dropped.}
29422 Stan: @emph{If people really wanted to add something like this, and get
29423 it working for the first time, they ought to modify ser-unix.c to send
29424 some kind of out-of-band message to a specially-setup stub and have the
29425 switch happen "in between" packets, so that from remote protocol's point
29426 of view, nothing actually happened.}
29428 @item B @var{addr},@var{mode}
29429 @cindex @samp{B} packet
29430 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
29431 breakpoint at @var{addr}.
29433 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
29434 (@pxref{insert breakpoint or watchpoint packet}).
29436 @cindex @samp{bc} packet
29439 Backward continue. Execute the target system in reverse. No parameter.
29440 @xref{Reverse Execution}, for more information.
29443 @xref{Stop Reply Packets}, for the reply specifications.
29445 @cindex @samp{bs} packet
29448 Backward single step. Execute one instruction in reverse. No parameter.
29449 @xref{Reverse Execution}, for more information.
29452 @xref{Stop Reply Packets}, for the reply specifications.
29454 @item c @r{[}@var{addr}@r{]}
29455 @cindex @samp{c} packet
29456 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
29457 resume at current address.
29460 @xref{Stop Reply Packets}, for the reply specifications.
29462 @item C @var{sig}@r{[};@var{addr}@r{]}
29463 @cindex @samp{C} packet
29464 Continue with signal @var{sig} (hex signal number). If
29465 @samp{;@var{addr}} is omitted, resume at same address.
29468 @xref{Stop Reply Packets}, for the reply specifications.
29471 @cindex @samp{d} packet
29474 Don't use this packet; instead, define a general set packet
29475 (@pxref{General Query Packets}).
29479 @cindex @samp{D} packet
29480 The first form of the packet is used to detach @value{GDBN} from the
29481 remote system. It is sent to the remote target
29482 before @value{GDBN} disconnects via the @code{detach} command.
29484 The second form, including a process ID, is used when multiprocess
29485 protocol extensions are enabled (@pxref{multiprocess extensions}), to
29486 detach only a specific process. The @var{pid} is specified as a
29487 big-endian hex string.
29497 @item F @var{RC},@var{EE},@var{CF};@var{XX}
29498 @cindex @samp{F} packet
29499 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
29500 This is part of the File-I/O protocol extension. @xref{File-I/O
29501 Remote Protocol Extension}, for the specification.
29504 @anchor{read registers packet}
29505 @cindex @samp{g} packet
29506 Read general registers.
29510 @item @var{XX@dots{}}
29511 Each byte of register data is described by two hex digits. The bytes
29512 with the register are transmitted in target byte order. The size of
29513 each register and their position within the @samp{g} packet are
29514 determined by the @value{GDBN} internal gdbarch functions
29515 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
29516 specification of several standard @samp{g} packets is specified below.
29521 @item G @var{XX@dots{}}
29522 @cindex @samp{G} packet
29523 Write general registers. @xref{read registers packet}, for a
29524 description of the @var{XX@dots{}} data.
29534 @item H @var{c} @var{thread-id}
29535 @cindex @samp{H} packet
29536 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
29537 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
29538 should be @samp{c} for step and continue operations, @samp{g} for other
29539 operations. The thread designator @var{thread-id} has the format and
29540 interpretation described in @ref{thread-id syntax}.
29551 @c 'H': How restrictive (or permissive) is the thread model. If a
29552 @c thread is selected and stopped, are other threads allowed
29553 @c to continue to execute? As I mentioned above, I think the
29554 @c semantics of each command when a thread is selected must be
29555 @c described. For example:
29557 @c 'g': If the stub supports threads and a specific thread is
29558 @c selected, returns the register block from that thread;
29559 @c otherwise returns current registers.
29561 @c 'G' If the stub supports threads and a specific thread is
29562 @c selected, sets the registers of the register block of
29563 @c that thread; otherwise sets current registers.
29565 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
29566 @anchor{cycle step packet}
29567 @cindex @samp{i} packet
29568 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
29569 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
29570 step starting at that address.
29573 @cindex @samp{I} packet
29574 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
29578 @cindex @samp{k} packet
29581 FIXME: @emph{There is no description of how to operate when a specific
29582 thread context has been selected (i.e.@: does 'k' kill only that
29585 @item m @var{addr},@var{length}
29586 @cindex @samp{m} packet
29587 Read @var{length} bytes of memory starting at address @var{addr}.
29588 Note that @var{addr} may not be aligned to any particular boundary.
29590 The stub need not use any particular size or alignment when gathering
29591 data from memory for the response; even if @var{addr} is word-aligned
29592 and @var{length} is a multiple of the word size, the stub is free to
29593 use byte accesses, or not. For this reason, this packet may not be
29594 suitable for accessing memory-mapped I/O devices.
29595 @cindex alignment of remote memory accesses
29596 @cindex size of remote memory accesses
29597 @cindex memory, alignment and size of remote accesses
29601 @item @var{XX@dots{}}
29602 Memory contents; each byte is transmitted as a two-digit hexadecimal
29603 number. The reply may contain fewer bytes than requested if the
29604 server was able to read only part of the region of memory.
29609 @item M @var{addr},@var{length}:@var{XX@dots{}}
29610 @cindex @samp{M} packet
29611 Write @var{length} bytes of memory starting at address @var{addr}.
29612 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
29613 hexadecimal number.
29620 for an error (this includes the case where only part of the data was
29625 @cindex @samp{p} packet
29626 Read the value of register @var{n}; @var{n} is in hex.
29627 @xref{read registers packet}, for a description of how the returned
29628 register value is encoded.
29632 @item @var{XX@dots{}}
29633 the register's value
29637 Indicating an unrecognized @var{query}.
29640 @item P @var{n@dots{}}=@var{r@dots{}}
29641 @anchor{write register packet}
29642 @cindex @samp{P} packet
29643 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
29644 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
29645 digits for each byte in the register (target byte order).
29655 @item q @var{name} @var{params}@dots{}
29656 @itemx Q @var{name} @var{params}@dots{}
29657 @cindex @samp{q} packet
29658 @cindex @samp{Q} packet
29659 General query (@samp{q}) and set (@samp{Q}). These packets are
29660 described fully in @ref{General Query Packets}.
29663 @cindex @samp{r} packet
29664 Reset the entire system.
29666 Don't use this packet; use the @samp{R} packet instead.
29669 @cindex @samp{R} packet
29670 Restart the program being debugged. @var{XX}, while needed, is ignored.
29671 This packet is only available in extended mode (@pxref{extended mode}).
29673 The @samp{R} packet has no reply.
29675 @item s @r{[}@var{addr}@r{]}
29676 @cindex @samp{s} packet
29677 Single step. @var{addr} is the address at which to resume. If
29678 @var{addr} is omitted, resume at same address.
29681 @xref{Stop Reply Packets}, for the reply specifications.
29683 @item S @var{sig}@r{[};@var{addr}@r{]}
29684 @anchor{step with signal packet}
29685 @cindex @samp{S} packet
29686 Step with signal. This is analogous to the @samp{C} packet, but
29687 requests a single-step, rather than a normal resumption of execution.
29690 @xref{Stop Reply Packets}, for the reply specifications.
29692 @item t @var{addr}:@var{PP},@var{MM}
29693 @cindex @samp{t} packet
29694 Search backwards starting at address @var{addr} for a match with pattern
29695 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
29696 @var{addr} must be at least 3 digits.
29698 @item T @var{thread-id}
29699 @cindex @samp{T} packet
29700 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
29705 thread is still alive
29711 Packets starting with @samp{v} are identified by a multi-letter name,
29712 up to the first @samp{;} or @samp{?} (or the end of the packet).
29714 @item vAttach;@var{pid}
29715 @cindex @samp{vAttach} packet
29716 Attach to a new process with the specified process ID @var{pid}.
29717 The process ID is a
29718 hexadecimal integer identifying the process. In all-stop mode, all
29719 threads in the attached process are stopped; in non-stop mode, it may be
29720 attached without being stopped if that is supported by the target.
29722 @c In non-stop mode, on a successful vAttach, the stub should set the
29723 @c current thread to a thread of the newly-attached process. After
29724 @c attaching, GDB queries for the attached process's thread ID with qC.
29725 @c Also note that, from a user perspective, whether or not the
29726 @c target is stopped on attach in non-stop mode depends on whether you
29727 @c use the foreground or background version of the attach command, not
29728 @c on what vAttach does; GDB does the right thing with respect to either
29729 @c stopping or restarting threads.
29731 This packet is only available in extended mode (@pxref{extended mode}).
29737 @item @r{Any stop packet}
29738 for success in all-stop mode (@pxref{Stop Reply Packets})
29740 for success in non-stop mode (@pxref{Remote Non-Stop})
29743 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
29744 @cindex @samp{vCont} packet
29745 Resume the inferior, specifying different actions for each thread.
29746 If an action is specified with no @var{thread-id}, then it is applied to any
29747 threads that don't have a specific action specified; if no default action is
29748 specified then other threads should remain stopped in all-stop mode and
29749 in their current state in non-stop mode.
29750 Specifying multiple
29751 default actions is an error; specifying no actions is also an error.
29752 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
29754 Currently supported actions are:
29760 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
29764 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
29769 The optional argument @var{addr} normally associated with the
29770 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
29771 not supported in @samp{vCont}.
29773 The @samp{t} action is only relevant in non-stop mode
29774 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
29775 A stop reply should be generated for any affected thread not already stopped.
29776 When a thread is stopped by means of a @samp{t} action,
29777 the corresponding stop reply should indicate that the thread has stopped with
29778 signal @samp{0}, regardless of whether the target uses some other signal
29779 as an implementation detail.
29782 @xref{Stop Reply Packets}, for the reply specifications.
29785 @cindex @samp{vCont?} packet
29786 Request a list of actions supported by the @samp{vCont} packet.
29790 @item vCont@r{[};@var{action}@dots{}@r{]}
29791 The @samp{vCont} packet is supported. Each @var{action} is a supported
29792 command in the @samp{vCont} packet.
29794 The @samp{vCont} packet is not supported.
29797 @item vFile:@var{operation}:@var{parameter}@dots{}
29798 @cindex @samp{vFile} packet
29799 Perform a file operation on the target system. For details,
29800 see @ref{Host I/O Packets}.
29802 @item vFlashErase:@var{addr},@var{length}
29803 @cindex @samp{vFlashErase} packet
29804 Direct the stub to erase @var{length} bytes of flash starting at
29805 @var{addr}. The region may enclose any number of flash blocks, but
29806 its start and end must fall on block boundaries, as indicated by the
29807 flash block size appearing in the memory map (@pxref{Memory Map
29808 Format}). @value{GDBN} groups flash memory programming operations
29809 together, and sends a @samp{vFlashDone} request after each group; the
29810 stub is allowed to delay erase operation until the @samp{vFlashDone}
29811 packet is received.
29813 The stub must support @samp{vCont} if it reports support for
29814 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
29815 this case @samp{vCont} actions can be specified to apply to all threads
29816 in a process by using the @samp{p@var{pid}.-1} form of the
29827 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
29828 @cindex @samp{vFlashWrite} packet
29829 Direct the stub to write data to flash address @var{addr}. The data
29830 is passed in binary form using the same encoding as for the @samp{X}
29831 packet (@pxref{Binary Data}). The memory ranges specified by
29832 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
29833 not overlap, and must appear in order of increasing addresses
29834 (although @samp{vFlashErase} packets for higher addresses may already
29835 have been received; the ordering is guaranteed only between
29836 @samp{vFlashWrite} packets). If a packet writes to an address that was
29837 neither erased by a preceding @samp{vFlashErase} packet nor by some other
29838 target-specific method, the results are unpredictable.
29846 for vFlashWrite addressing non-flash memory
29852 @cindex @samp{vFlashDone} packet
29853 Indicate to the stub that flash programming operation is finished.
29854 The stub is permitted to delay or batch the effects of a group of
29855 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
29856 @samp{vFlashDone} packet is received. The contents of the affected
29857 regions of flash memory are unpredictable until the @samp{vFlashDone}
29858 request is completed.
29860 @item vKill;@var{pid}
29861 @cindex @samp{vKill} packet
29862 Kill the process with the specified process ID. @var{pid} is a
29863 hexadecimal integer identifying the process. This packet is used in
29864 preference to @samp{k} when multiprocess protocol extensions are
29865 supported; see @ref{multiprocess extensions}.
29875 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
29876 @cindex @samp{vRun} packet
29877 Run the program @var{filename}, passing it each @var{argument} on its
29878 command line. The file and arguments are hex-encoded strings. If
29879 @var{filename} is an empty string, the stub may use a default program
29880 (e.g.@: the last program run). The program is created in the stopped
29883 @c FIXME: What about non-stop mode?
29885 This packet is only available in extended mode (@pxref{extended mode}).
29891 @item @r{Any stop packet}
29892 for success (@pxref{Stop Reply Packets})
29896 @anchor{vStopped packet}
29897 @cindex @samp{vStopped} packet
29899 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
29900 reply and prompt for the stub to report another one.
29904 @item @r{Any stop packet}
29905 if there is another unreported stop event (@pxref{Stop Reply Packets})
29907 if there are no unreported stop events
29910 @item X @var{addr},@var{length}:@var{XX@dots{}}
29912 @cindex @samp{X} packet
29913 Write data to memory, where the data is transmitted in binary.
29914 @var{addr} is address, @var{length} is number of bytes,
29915 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
29925 @item z @var{type},@var{addr},@var{kind}
29926 @itemx Z @var{type},@var{addr},@var{kind}
29927 @anchor{insert breakpoint or watchpoint packet}
29928 @cindex @samp{z} packet
29929 @cindex @samp{Z} packets
29930 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
29931 watchpoint starting at address @var{address} of kind @var{kind}.
29933 Each breakpoint and watchpoint packet @var{type} is documented
29936 @emph{Implementation notes: A remote target shall return an empty string
29937 for an unrecognized breakpoint or watchpoint packet @var{type}. A
29938 remote target shall support either both or neither of a given
29939 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
29940 avoid potential problems with duplicate packets, the operations should
29941 be implemented in an idempotent way.}
29943 @item z0,@var{addr},@var{kind}
29944 @itemx Z0,@var{addr},@var{kind}
29945 @cindex @samp{z0} packet
29946 @cindex @samp{Z0} packet
29947 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
29948 @var{addr} of type @var{kind}.
29950 A memory breakpoint is implemented by replacing the instruction at
29951 @var{addr} with a software breakpoint or trap instruction. The
29952 @var{kind} is target-specific and typically indicates the size of
29953 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
29954 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
29955 architectures have additional meanings for @var{kind};
29956 see @ref{Architecture-Specific Protocol Details}.
29958 @emph{Implementation note: It is possible for a target to copy or move
29959 code that contains memory breakpoints (e.g., when implementing
29960 overlays). The behavior of this packet, in the presence of such a
29961 target, is not defined.}
29973 @item z1,@var{addr},@var{kind}
29974 @itemx Z1,@var{addr},@var{kind}
29975 @cindex @samp{z1} packet
29976 @cindex @samp{Z1} packet
29977 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
29978 address @var{addr}.
29980 A hardware breakpoint is implemented using a mechanism that is not
29981 dependant on being able to modify the target's memory. @var{kind}
29982 has the same meaning as in @samp{Z0} packets.
29984 @emph{Implementation note: A hardware breakpoint is not affected by code
29997 @item z2,@var{addr},@var{kind}
29998 @itemx Z2,@var{addr},@var{kind}
29999 @cindex @samp{z2} packet
30000 @cindex @samp{Z2} packet
30001 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30002 @var{kind} is interpreted as the number of bytes to watch.
30014 @item z3,@var{addr},@var{kind}
30015 @itemx Z3,@var{addr},@var{kind}
30016 @cindex @samp{z3} packet
30017 @cindex @samp{Z3} packet
30018 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30019 @var{kind} is interpreted as the number of bytes to watch.
30031 @item z4,@var{addr},@var{kind}
30032 @itemx Z4,@var{addr},@var{kind}
30033 @cindex @samp{z4} packet
30034 @cindex @samp{Z4} packet
30035 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30036 @var{kind} is interpreted as the number of bytes to watch.
30050 @node Stop Reply Packets
30051 @section Stop Reply Packets
30052 @cindex stop reply packets
30054 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30055 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30056 receive any of the below as a reply. Except for @samp{?}
30057 and @samp{vStopped}, that reply is only returned
30058 when the target halts. In the below the exact meaning of @dfn{signal
30059 number} is defined by the header @file{include/gdb/signals.h} in the
30060 @value{GDBN} source code.
30062 As in the description of request packets, we include spaces in the
30063 reply templates for clarity; these are not part of the reply packet's
30064 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30070 The program received signal number @var{AA} (a two-digit hexadecimal
30071 number). This is equivalent to a @samp{T} response with no
30072 @var{n}:@var{r} pairs.
30074 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30075 @cindex @samp{T} packet reply
30076 The program received signal number @var{AA} (a two-digit hexadecimal
30077 number). This is equivalent to an @samp{S} response, except that the
30078 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30079 and other information directly in the stop reply packet, reducing
30080 round-trip latency. Single-step and breakpoint traps are reported
30081 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30085 If @var{n} is a hexadecimal number, it is a register number, and the
30086 corresponding @var{r} gives that register's value. @var{r} is a
30087 series of bytes in target byte order, with each byte given by a
30088 two-digit hex number.
30091 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30092 the stopped thread, as specified in @ref{thread-id syntax}.
30095 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30096 the core on which the stop event was detected.
30099 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30100 specific event that stopped the target. The currently defined stop
30101 reasons are listed below. @var{aa} should be @samp{05}, the trap
30102 signal. At most one stop reason should be present.
30105 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30106 and go on to the next; this allows us to extend the protocol in the
30110 The currently defined stop reasons are:
30116 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30119 @cindex shared library events, remote reply
30121 The packet indicates that the loaded libraries have changed.
30122 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30123 list of loaded libraries. @var{r} is ignored.
30125 @cindex replay log events, remote reply
30127 The packet indicates that the target cannot continue replaying
30128 logged execution events, because it has reached the end (or the
30129 beginning when executing backward) of the log. The value of @var{r}
30130 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30131 for more information.
30135 @itemx W @var{AA} ; process:@var{pid}
30136 The process exited, and @var{AA} is the exit status. This is only
30137 applicable to certain targets.
30139 The second form of the response, including the process ID of the exited
30140 process, can be used only when @value{GDBN} has reported support for
30141 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30142 The @var{pid} is formatted as a big-endian hex string.
30145 @itemx X @var{AA} ; process:@var{pid}
30146 The process terminated with signal @var{AA}.
30148 The second form of the response, including the process ID of the
30149 terminated process, can be used only when @value{GDBN} has reported
30150 support for multiprocess protocol extensions; see @ref{multiprocess
30151 extensions}. The @var{pid} is formatted as a big-endian hex string.
30153 @item O @var{XX}@dots{}
30154 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30155 written as the program's console output. This can happen at any time
30156 while the program is running and the debugger should continue to wait
30157 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30159 @item F @var{call-id},@var{parameter}@dots{}
30160 @var{call-id} is the identifier which says which host system call should
30161 be called. This is just the name of the function. Translation into the
30162 correct system call is only applicable as it's defined in @value{GDBN}.
30163 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30166 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30167 this very system call.
30169 The target replies with this packet when it expects @value{GDBN} to
30170 call a host system call on behalf of the target. @value{GDBN} replies
30171 with an appropriate @samp{F} packet and keeps up waiting for the next
30172 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30173 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30174 Protocol Extension}, for more details.
30178 @node General Query Packets
30179 @section General Query Packets
30180 @cindex remote query requests
30182 Packets starting with @samp{q} are @dfn{general query packets};
30183 packets starting with @samp{Q} are @dfn{general set packets}. General
30184 query and set packets are a semi-unified form for retrieving and
30185 sending information to and from the stub.
30187 The initial letter of a query or set packet is followed by a name
30188 indicating what sort of thing the packet applies to. For example,
30189 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30190 definitions with the stub. These packet names follow some
30195 The name must not contain commas, colons or semicolons.
30197 Most @value{GDBN} query and set packets have a leading upper case
30200 The names of custom vendor packets should use a company prefix, in
30201 lower case, followed by a period. For example, packets designed at
30202 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30203 foos) or @samp{Qacme.bar} (for setting bars).
30206 The name of a query or set packet should be separated from any
30207 parameters by a @samp{:}; the parameters themselves should be
30208 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30209 full packet name, and check for a separator or the end of the packet,
30210 in case two packet names share a common prefix. New packets should not begin
30211 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30212 packets predate these conventions, and have arguments without any terminator
30213 for the packet name; we suspect they are in widespread use in places that
30214 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30215 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30218 Like the descriptions of the other packets, each description here
30219 has a template showing the packet's overall syntax, followed by an
30220 explanation of the packet's meaning. We include spaces in some of the
30221 templates for clarity; these are not part of the packet's syntax. No
30222 @value{GDBN} packet uses spaces to separate its components.
30224 Here are the currently defined query and set packets:
30229 @cindex current thread, remote request
30230 @cindex @samp{qC} packet
30231 Return the current thread ID.
30235 @item QC @var{thread-id}
30236 Where @var{thread-id} is a thread ID as documented in
30237 @ref{thread-id syntax}.
30238 @item @r{(anything else)}
30239 Any other reply implies the old thread ID.
30242 @item qCRC:@var{addr},@var{length}
30243 @cindex CRC of memory block, remote request
30244 @cindex @samp{qCRC} packet
30245 Compute the CRC checksum of a block of memory using CRC-32 defined in
30246 IEEE 802.3. The CRC is computed byte at a time, taking the most
30247 significant bit of each byte first. The initial pattern code
30248 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30250 @emph{Note:} This is the same CRC used in validating separate debug
30251 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30252 Files}). However the algorithm is slightly different. When validating
30253 separate debug files, the CRC is computed taking the @emph{least}
30254 significant bit of each byte first, and the final result is inverted to
30255 detect trailing zeros.
30260 An error (such as memory fault)
30261 @item C @var{crc32}
30262 The specified memory region's checksum is @var{crc32}.
30266 @itemx qsThreadInfo
30267 @cindex list active threads, remote request
30268 @cindex @samp{qfThreadInfo} packet
30269 @cindex @samp{qsThreadInfo} packet
30270 Obtain a list of all active thread IDs from the target (OS). Since there
30271 may be too many active threads to fit into one reply packet, this query
30272 works iteratively: it may require more than one query/reply sequence to
30273 obtain the entire list of threads. The first query of the sequence will
30274 be the @samp{qfThreadInfo} query; subsequent queries in the
30275 sequence will be the @samp{qsThreadInfo} query.
30277 NOTE: This packet replaces the @samp{qL} query (see below).
30281 @item m @var{thread-id}
30283 @item m @var{thread-id},@var{thread-id}@dots{}
30284 a comma-separated list of thread IDs
30286 (lower case letter @samp{L}) denotes end of list.
30289 In response to each query, the target will reply with a list of one or
30290 more thread IDs, separated by commas.
30291 @value{GDBN} will respond to each reply with a request for more thread
30292 ids (using the @samp{qs} form of the query), until the target responds
30293 with @samp{l} (lower-case el, for @dfn{last}).
30294 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30297 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30298 @cindex get thread-local storage address, remote request
30299 @cindex @samp{qGetTLSAddr} packet
30300 Fetch the address associated with thread local storage specified
30301 by @var{thread-id}, @var{offset}, and @var{lm}.
30303 @var{thread-id} is the thread ID associated with the
30304 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30306 @var{offset} is the (big endian, hex encoded) offset associated with the
30307 thread local variable. (This offset is obtained from the debug
30308 information associated with the variable.)
30310 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30311 the load module associated with the thread local storage. For example,
30312 a @sc{gnu}/Linux system will pass the link map address of the shared
30313 object associated with the thread local storage under consideration.
30314 Other operating environments may choose to represent the load module
30315 differently, so the precise meaning of this parameter will vary.
30319 @item @var{XX}@dots{}
30320 Hex encoded (big endian) bytes representing the address of the thread
30321 local storage requested.
30324 An error occurred. @var{nn} are hex digits.
30327 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30330 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30331 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30332 digit) is one to indicate the first query and zero to indicate a
30333 subsequent query; @var{threadcount} (two hex digits) is the maximum
30334 number of threads the response packet can contain; and @var{nextthread}
30335 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30336 returned in the response as @var{argthread}.
30338 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
30342 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
30343 Where: @var{count} (two hex digits) is the number of threads being
30344 returned; @var{done} (one hex digit) is zero to indicate more threads
30345 and one indicates no further threads; @var{argthreadid} (eight hex
30346 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
30347 is a sequence of thread IDs from the target. @var{threadid} (eight hex
30348 digits). See @code{remote.c:parse_threadlist_response()}.
30352 @cindex section offsets, remote request
30353 @cindex @samp{qOffsets} packet
30354 Get section offsets that the target used when relocating the downloaded
30359 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
30360 Relocate the @code{Text} section by @var{xxx} from its original address.
30361 Relocate the @code{Data} section by @var{yyy} from its original address.
30362 If the object file format provides segment information (e.g.@: @sc{elf}
30363 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
30364 segments by the supplied offsets.
30366 @emph{Note: while a @code{Bss} offset may be included in the response,
30367 @value{GDBN} ignores this and instead applies the @code{Data} offset
30368 to the @code{Bss} section.}
30370 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
30371 Relocate the first segment of the object file, which conventionally
30372 contains program code, to a starting address of @var{xxx}. If
30373 @samp{DataSeg} is specified, relocate the second segment, which
30374 conventionally contains modifiable data, to a starting address of
30375 @var{yyy}. @value{GDBN} will report an error if the object file
30376 does not contain segment information, or does not contain at least
30377 as many segments as mentioned in the reply. Extra segments are
30378 kept at fixed offsets relative to the last relocated segment.
30381 @item qP @var{mode} @var{thread-id}
30382 @cindex thread information, remote request
30383 @cindex @samp{qP} packet
30384 Returns information on @var{thread-id}. Where: @var{mode} is a hex
30385 encoded 32 bit mode; @var{thread-id} is a thread ID
30386 (@pxref{thread-id syntax}).
30388 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
30391 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
30395 @cindex non-stop mode, remote request
30396 @cindex @samp{QNonStop} packet
30398 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
30399 @xref{Remote Non-Stop}, for more information.
30404 The request succeeded.
30407 An error occurred. @var{nn} are hex digits.
30410 An empty reply indicates that @samp{QNonStop} is not supported by
30414 This packet is not probed by default; the remote stub must request it,
30415 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30416 Use of this packet is controlled by the @code{set non-stop} command;
30417 @pxref{Non-Stop Mode}.
30419 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
30420 @cindex pass signals to inferior, remote request
30421 @cindex @samp{QPassSignals} packet
30422 @anchor{QPassSignals}
30423 Each listed @var{signal} should be passed directly to the inferior process.
30424 Signals are numbered identically to continue packets and stop replies
30425 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
30426 strictly greater than the previous item. These signals do not need to stop
30427 the inferior, or be reported to @value{GDBN}. All other signals should be
30428 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
30429 combine; any earlier @samp{QPassSignals} list is completely replaced by the
30430 new list. This packet improves performance when using @samp{handle
30431 @var{signal} nostop noprint pass}.
30436 The request succeeded.
30439 An error occurred. @var{nn} are hex digits.
30442 An empty reply indicates that @samp{QPassSignals} is not supported by
30446 Use of this packet is controlled by the @code{set remote pass-signals}
30447 command (@pxref{Remote Configuration, set remote pass-signals}).
30448 This packet is not probed by default; the remote stub must request it,
30449 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30451 @item qRcmd,@var{command}
30452 @cindex execute remote command, remote request
30453 @cindex @samp{qRcmd} packet
30454 @var{command} (hex encoded) is passed to the local interpreter for
30455 execution. Invalid commands should be reported using the output
30456 string. Before the final result packet, the target may also respond
30457 with a number of intermediate @samp{O@var{output}} console output
30458 packets. @emph{Implementors should note that providing access to a
30459 stubs's interpreter may have security implications}.
30464 A command response with no output.
30466 A command response with the hex encoded output string @var{OUTPUT}.
30468 Indicate a badly formed request.
30470 An empty reply indicates that @samp{qRcmd} is not recognized.
30473 (Note that the @code{qRcmd} packet's name is separated from the
30474 command by a @samp{,}, not a @samp{:}, contrary to the naming
30475 conventions above. Please don't use this packet as a model for new
30478 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
30479 @cindex searching memory, in remote debugging
30480 @cindex @samp{qSearch:memory} packet
30481 @anchor{qSearch memory}
30482 Search @var{length} bytes at @var{address} for @var{search-pattern}.
30483 @var{address} and @var{length} are encoded in hex.
30484 @var{search-pattern} is a sequence of bytes, hex encoded.
30489 The pattern was not found.
30491 The pattern was found at @var{address}.
30493 A badly formed request or an error was encountered while searching memory.
30495 An empty reply indicates that @samp{qSearch:memory} is not recognized.
30498 @item QStartNoAckMode
30499 @cindex @samp{QStartNoAckMode} packet
30500 @anchor{QStartNoAckMode}
30501 Request that the remote stub disable the normal @samp{+}/@samp{-}
30502 protocol acknowledgments (@pxref{Packet Acknowledgment}).
30507 The stub has switched to no-acknowledgment mode.
30508 @value{GDBN} acknowledges this reponse,
30509 but neither the stub nor @value{GDBN} shall send or expect further
30510 @samp{+}/@samp{-} acknowledgments in the current connection.
30512 An empty reply indicates that the stub does not support no-acknowledgment mode.
30515 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
30516 @cindex supported packets, remote query
30517 @cindex features of the remote protocol
30518 @cindex @samp{qSupported} packet
30519 @anchor{qSupported}
30520 Tell the remote stub about features supported by @value{GDBN}, and
30521 query the stub for features it supports. This packet allows
30522 @value{GDBN} and the remote stub to take advantage of each others'
30523 features. @samp{qSupported} also consolidates multiple feature probes
30524 at startup, to improve @value{GDBN} performance---a single larger
30525 packet performs better than multiple smaller probe packets on
30526 high-latency links. Some features may enable behavior which must not
30527 be on by default, e.g.@: because it would confuse older clients or
30528 stubs. Other features may describe packets which could be
30529 automatically probed for, but are not. These features must be
30530 reported before @value{GDBN} will use them. This ``default
30531 unsupported'' behavior is not appropriate for all packets, but it
30532 helps to keep the initial connection time under control with new
30533 versions of @value{GDBN} which support increasing numbers of packets.
30537 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
30538 The stub supports or does not support each returned @var{stubfeature},
30539 depending on the form of each @var{stubfeature} (see below for the
30542 An empty reply indicates that @samp{qSupported} is not recognized,
30543 or that no features needed to be reported to @value{GDBN}.
30546 The allowed forms for each feature (either a @var{gdbfeature} in the
30547 @samp{qSupported} packet, or a @var{stubfeature} in the response)
30551 @item @var{name}=@var{value}
30552 The remote protocol feature @var{name} is supported, and associated
30553 with the specified @var{value}. The format of @var{value} depends
30554 on the feature, but it must not include a semicolon.
30556 The remote protocol feature @var{name} is supported, and does not
30557 need an associated value.
30559 The remote protocol feature @var{name} is not supported.
30561 The remote protocol feature @var{name} may be supported, and
30562 @value{GDBN} should auto-detect support in some other way when it is
30563 needed. This form will not be used for @var{gdbfeature} notifications,
30564 but may be used for @var{stubfeature} responses.
30567 Whenever the stub receives a @samp{qSupported} request, the
30568 supplied set of @value{GDBN} features should override any previous
30569 request. This allows @value{GDBN} to put the stub in a known
30570 state, even if the stub had previously been communicating with
30571 a different version of @value{GDBN}.
30573 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
30578 This feature indicates whether @value{GDBN} supports multiprocess
30579 extensions to the remote protocol. @value{GDBN} does not use such
30580 extensions unless the stub also reports that it supports them by
30581 including @samp{multiprocess+} in its @samp{qSupported} reply.
30582 @xref{multiprocess extensions}, for details.
30585 Stubs should ignore any unknown values for
30586 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
30587 packet supports receiving packets of unlimited length (earlier
30588 versions of @value{GDBN} may reject overly long responses). Additional values
30589 for @var{gdbfeature} may be defined in the future to let the stub take
30590 advantage of new features in @value{GDBN}, e.g.@: incompatible
30591 improvements in the remote protocol---the @samp{multiprocess} feature is
30592 an example of such a feature. The stub's reply should be independent
30593 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
30594 describes all the features it supports, and then the stub replies with
30595 all the features it supports.
30597 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
30598 responses, as long as each response uses one of the standard forms.
30600 Some features are flags. A stub which supports a flag feature
30601 should respond with a @samp{+} form response. Other features
30602 require values, and the stub should respond with an @samp{=}
30605 Each feature has a default value, which @value{GDBN} will use if
30606 @samp{qSupported} is not available or if the feature is not mentioned
30607 in the @samp{qSupported} response. The default values are fixed; a
30608 stub is free to omit any feature responses that match the defaults.
30610 Not all features can be probed, but for those which can, the probing
30611 mechanism is useful: in some cases, a stub's internal
30612 architecture may not allow the protocol layer to know some information
30613 about the underlying target in advance. This is especially common in
30614 stubs which may be configured for multiple targets.
30616 These are the currently defined stub features and their properties:
30618 @multitable @columnfractions 0.35 0.2 0.12 0.2
30619 @c NOTE: The first row should be @headitem, but we do not yet require
30620 @c a new enough version of Texinfo (4.7) to use @headitem.
30622 @tab Value Required
30626 @item @samp{PacketSize}
30631 @item @samp{qXfer:auxv:read}
30636 @item @samp{qXfer:features:read}
30641 @item @samp{qXfer:libraries:read}
30646 @item @samp{qXfer:memory-map:read}
30651 @item @samp{qXfer:spu:read}
30656 @item @samp{qXfer:spu:write}
30661 @item @samp{qXfer:siginfo:read}
30666 @item @samp{qXfer:siginfo:write}
30671 @item @samp{qXfer:threads:read}
30677 @item @samp{QNonStop}
30682 @item @samp{QPassSignals}
30687 @item @samp{QStartNoAckMode}
30692 @item @samp{multiprocess}
30697 @item @samp{ConditionalTracepoints}
30702 @item @samp{ReverseContinue}
30707 @item @samp{ReverseStep}
30714 These are the currently defined stub features, in more detail:
30717 @cindex packet size, remote protocol
30718 @item PacketSize=@var{bytes}
30719 The remote stub can accept packets up to at least @var{bytes} in
30720 length. @value{GDBN} will send packets up to this size for bulk
30721 transfers, and will never send larger packets. This is a limit on the
30722 data characters in the packet, including the frame and checksum.
30723 There is no trailing NUL byte in a remote protocol packet; if the stub
30724 stores packets in a NUL-terminated format, it should allow an extra
30725 byte in its buffer for the NUL. If this stub feature is not supported,
30726 @value{GDBN} guesses based on the size of the @samp{g} packet response.
30728 @item qXfer:auxv:read
30729 The remote stub understands the @samp{qXfer:auxv:read} packet
30730 (@pxref{qXfer auxiliary vector read}).
30732 @item qXfer:features:read
30733 The remote stub understands the @samp{qXfer:features:read} packet
30734 (@pxref{qXfer target description read}).
30736 @item qXfer:libraries:read
30737 The remote stub understands the @samp{qXfer:libraries:read} packet
30738 (@pxref{qXfer library list read}).
30740 @item qXfer:memory-map:read
30741 The remote stub understands the @samp{qXfer:memory-map:read} packet
30742 (@pxref{qXfer memory map read}).
30744 @item qXfer:spu:read
30745 The remote stub understands the @samp{qXfer:spu:read} packet
30746 (@pxref{qXfer spu read}).
30748 @item qXfer:spu:write
30749 The remote stub understands the @samp{qXfer:spu:write} packet
30750 (@pxref{qXfer spu write}).
30752 @item qXfer:siginfo:read
30753 The remote stub understands the @samp{qXfer:siginfo:read} packet
30754 (@pxref{qXfer siginfo read}).
30756 @item qXfer:siginfo:write
30757 The remote stub understands the @samp{qXfer:siginfo:write} packet
30758 (@pxref{qXfer siginfo write}).
30760 @item qXfer:threads:read
30761 The remote stub understands the @samp{qXfer:threads:read} packet
30762 (@pxref{qXfer threads read}).
30765 The remote stub understands the @samp{QNonStop} packet
30766 (@pxref{QNonStop}).
30769 The remote stub understands the @samp{QPassSignals} packet
30770 (@pxref{QPassSignals}).
30772 @item QStartNoAckMode
30773 The remote stub understands the @samp{QStartNoAckMode} packet and
30774 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
30777 @anchor{multiprocess extensions}
30778 @cindex multiprocess extensions, in remote protocol
30779 The remote stub understands the multiprocess extensions to the remote
30780 protocol syntax. The multiprocess extensions affect the syntax of
30781 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
30782 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
30783 replies. Note that reporting this feature indicates support for the
30784 syntactic extensions only, not that the stub necessarily supports
30785 debugging of more than one process at a time. The stub must not use
30786 multiprocess extensions in packet replies unless @value{GDBN} has also
30787 indicated it supports them in its @samp{qSupported} request.
30789 @item qXfer:osdata:read
30790 The remote stub understands the @samp{qXfer:osdata:read} packet
30791 ((@pxref{qXfer osdata read}).
30793 @item ConditionalTracepoints
30794 The remote stub accepts and implements conditional expressions defined
30795 for tracepoints (@pxref{Tracepoint Conditions}).
30797 @item ReverseContinue
30798 The remote stub accepts and implements the reverse continue packet
30802 The remote stub accepts and implements the reverse step packet
30808 @cindex symbol lookup, remote request
30809 @cindex @samp{qSymbol} packet
30810 Notify the target that @value{GDBN} is prepared to serve symbol lookup
30811 requests. Accept requests from the target for the values of symbols.
30816 The target does not need to look up any (more) symbols.
30817 @item qSymbol:@var{sym_name}
30818 The target requests the value of symbol @var{sym_name} (hex encoded).
30819 @value{GDBN} may provide the value by using the
30820 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
30824 @item qSymbol:@var{sym_value}:@var{sym_name}
30825 Set the value of @var{sym_name} to @var{sym_value}.
30827 @var{sym_name} (hex encoded) is the name of a symbol whose value the
30828 target has previously requested.
30830 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
30831 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
30837 The target does not need to look up any (more) symbols.
30838 @item qSymbol:@var{sym_name}
30839 The target requests the value of a new symbol @var{sym_name} (hex
30840 encoded). @value{GDBN} will continue to supply the values of symbols
30841 (if available), until the target ceases to request them.
30846 @item QTDisconnected
30852 @xref{Tracepoint Packets}.
30854 @item qThreadExtraInfo,@var{thread-id}
30855 @cindex thread attributes info, remote request
30856 @cindex @samp{qThreadExtraInfo} packet
30857 Obtain a printable string description of a thread's attributes from
30858 the target OS. @var{thread-id} is a thread ID;
30859 see @ref{thread-id syntax}. This
30860 string may contain anything that the target OS thinks is interesting
30861 for @value{GDBN} to tell the user about the thread. The string is
30862 displayed in @value{GDBN}'s @code{info threads} display. Some
30863 examples of possible thread extra info strings are @samp{Runnable}, or
30864 @samp{Blocked on Mutex}.
30868 @item @var{XX}@dots{}
30869 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
30870 comprising the printable string containing the extra information about
30871 the thread's attributes.
30874 (Note that the @code{qThreadExtraInfo} packet's name is separated from
30875 the command by a @samp{,}, not a @samp{:}, contrary to the naming
30876 conventions above. Please don't use this packet as a model for new
30888 @xref{Tracepoint Packets}.
30890 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
30891 @cindex read special object, remote request
30892 @cindex @samp{qXfer} packet
30893 @anchor{qXfer read}
30894 Read uninterpreted bytes from the target's special data area
30895 identified by the keyword @var{object}. Request @var{length} bytes
30896 starting at @var{offset} bytes into the data. The content and
30897 encoding of @var{annex} is specific to @var{object}; it can supply
30898 additional details about what data to access.
30900 Here are the specific requests of this form defined so far. All
30901 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
30902 formats, listed below.
30905 @item qXfer:auxv:read::@var{offset},@var{length}
30906 @anchor{qXfer auxiliary vector read}
30907 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
30908 auxiliary vector}. Note @var{annex} must be empty.
30910 This packet is not probed by default; the remote stub must request it,
30911 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30913 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
30914 @anchor{qXfer target description read}
30915 Access the @dfn{target description}. @xref{Target Descriptions}. The
30916 annex specifies which XML document to access. The main description is
30917 always loaded from the @samp{target.xml} annex.
30919 This packet is not probed by default; the remote stub must request it,
30920 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30922 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
30923 @anchor{qXfer library list read}
30924 Access the target's list of loaded libraries. @xref{Library List Format}.
30925 The annex part of the generic @samp{qXfer} packet must be empty
30926 (@pxref{qXfer read}).
30928 Targets which maintain a list of libraries in the program's memory do
30929 not need to implement this packet; it is designed for platforms where
30930 the operating system manages the list of loaded libraries.
30932 This packet is not probed by default; the remote stub must request it,
30933 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30935 @item qXfer:memory-map:read::@var{offset},@var{length}
30936 @anchor{qXfer memory map read}
30937 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
30938 annex part of the generic @samp{qXfer} packet must be empty
30939 (@pxref{qXfer read}).
30941 This packet is not probed by default; the remote stub must request it,
30942 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30944 @item qXfer:siginfo:read::@var{offset},@var{length}
30945 @anchor{qXfer siginfo read}
30946 Read contents of the extra signal information on the target
30947 system. The annex part of the generic @samp{qXfer} packet must be
30948 empty (@pxref{qXfer read}).
30950 This packet is not probed by default; the remote stub must request it,
30951 by supplying an appropriate @samp{qSupported} response
30952 (@pxref{qSupported}).
30954 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
30955 @anchor{qXfer spu read}
30956 Read contents of an @code{spufs} file on the target system. The
30957 annex specifies which file to read; it must be of the form
30958 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
30959 in the target process, and @var{name} identifes the @code{spufs} file
30960 in that context to be accessed.
30962 This packet is not probed by default; the remote stub must request it,
30963 by supplying an appropriate @samp{qSupported} response
30964 (@pxref{qSupported}).
30966 @item qXfer:threads:read::@var{offset},@var{length}
30967 @anchor{qXfer threads read}
30968 Access the list of threads on target. @xref{Thread List Format}. The
30969 annex part of the generic @samp{qXfer} packet must be empty
30970 (@pxref{qXfer read}).
30972 This packet is not probed by default; the remote stub must request it,
30973 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30975 @item qXfer:osdata:read::@var{offset},@var{length}
30976 @anchor{qXfer osdata read}
30977 Access the target's @dfn{operating system information}.
30978 @xref{Operating System Information}.
30985 Data @var{data} (@pxref{Binary Data}) has been read from the
30986 target. There may be more data at a higher address (although
30987 it is permitted to return @samp{m} even for the last valid
30988 block of data, as long as at least one byte of data was read).
30989 @var{data} may have fewer bytes than the @var{length} in the
30993 Data @var{data} (@pxref{Binary Data}) has been read from the target.
30994 There is no more data to be read. @var{data} may have fewer bytes
30995 than the @var{length} in the request.
30998 The @var{offset} in the request is at the end of the data.
30999 There is no more data to be read.
31002 The request was malformed, or @var{annex} was invalid.
31005 The offset was invalid, or there was an error encountered reading the data.
31006 @var{nn} is a hex-encoded @code{errno} value.
31009 An empty reply indicates the @var{object} string was not recognized by
31010 the stub, or that the object does not support reading.
31013 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31014 @cindex write data into object, remote request
31015 @anchor{qXfer write}
31016 Write uninterpreted bytes into the target's special data area
31017 identified by the keyword @var{object}, starting at @var{offset} bytes
31018 into the data. @var{data}@dots{} is the binary-encoded data
31019 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31020 is specific to @var{object}; it can supply additional details about what data
31023 Here are the specific requests of this form defined so far. All
31024 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31025 formats, listed below.
31028 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31029 @anchor{qXfer siginfo write}
31030 Write @var{data} to the extra signal information on the target system.
31031 The annex part of the generic @samp{qXfer} packet must be
31032 empty (@pxref{qXfer write}).
31034 This packet is not probed by default; the remote stub must request it,
31035 by supplying an appropriate @samp{qSupported} response
31036 (@pxref{qSupported}).
31038 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31039 @anchor{qXfer spu write}
31040 Write @var{data} to an @code{spufs} file on the target system. The
31041 annex specifies which file to write; it must be of the form
31042 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31043 in the target process, and @var{name} identifes the @code{spufs} file
31044 in that context to be accessed.
31046 This packet is not probed by default; the remote stub must request it,
31047 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31053 @var{nn} (hex encoded) is the number of bytes written.
31054 This may be fewer bytes than supplied in the request.
31057 The request was malformed, or @var{annex} was invalid.
31060 The offset was invalid, or there was an error encountered writing the data.
31061 @var{nn} is a hex-encoded @code{errno} value.
31064 An empty reply indicates the @var{object} string was not
31065 recognized by the stub, or that the object does not support writing.
31068 @item qXfer:@var{object}:@var{operation}:@dots{}
31069 Requests of this form may be added in the future. When a stub does
31070 not recognize the @var{object} keyword, or its support for
31071 @var{object} does not recognize the @var{operation} keyword, the stub
31072 must respond with an empty packet.
31074 @item qAttached:@var{pid}
31075 @cindex query attached, remote request
31076 @cindex @samp{qAttached} packet
31077 Return an indication of whether the remote server attached to an
31078 existing process or created a new process. When the multiprocess
31079 protocol extensions are supported (@pxref{multiprocess extensions}),
31080 @var{pid} is an integer in hexadecimal format identifying the target
31081 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31082 the query packet will be simplified as @samp{qAttached}.
31084 This query is used, for example, to know whether the remote process
31085 should be detached or killed when a @value{GDBN} session is ended with
31086 the @code{quit} command.
31091 The remote server attached to an existing process.
31093 The remote server created a new process.
31095 A badly formed request or an error was encountered.
31100 @node Architecture-Specific Protocol Details
31101 @section Architecture-Specific Protocol Details
31103 This section describes how the remote protocol is applied to specific
31104 target architectures. Also see @ref{Standard Target Features}, for
31105 details of XML target descriptions for each architecture.
31109 @subsubsection Breakpoint Kinds
31111 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31116 16-bit Thumb mode breakpoint.
31119 32-bit Thumb mode (Thumb-2) breakpoint.
31122 32-bit ARM mode breakpoint.
31128 @subsubsection Register Packet Format
31130 The following @code{g}/@code{G} packets have previously been defined.
31131 In the below, some thirty-two bit registers are transferred as
31132 sixty-four bits. Those registers should be zero/sign extended (which?)
31133 to fill the space allocated. Register bytes are transferred in target
31134 byte order. The two nibbles within a register byte are transferred
31135 most-significant - least-significant.
31141 All registers are transferred as thirty-two bit quantities in the order:
31142 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31143 registers; fsr; fir; fp.
31147 All registers are transferred as sixty-four bit quantities (including
31148 thirty-two bit registers such as @code{sr}). The ordering is the same
31153 @node Tracepoint Packets
31154 @section Tracepoint Packets
31155 @cindex tracepoint packets
31156 @cindex packets, tracepoint
31158 Here we describe the packets @value{GDBN} uses to implement
31159 tracepoints (@pxref{Tracepoints}).
31163 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31164 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31165 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31166 the tracepoint is disabled. @var{step} is the tracepoint's step
31167 count, and @var{pass} is its pass count. If an @samp{F} is present,
31168 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31169 the number of bytes that the target should copy elsewhere to make room
31170 for the tracepoint. If an @samp{X} is present, it introduces a
31171 tracepoint condition, which consists of a hexadecimal length, followed
31172 by a comma and hex-encoded bytes, in a manner similar to action
31173 encodings as described below. If the trailing @samp{-} is present,
31174 further @samp{QTDP} packets will follow to specify this tracepoint's
31180 The packet was understood and carried out.
31182 The packet was not recognized.
31185 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31186 Define actions to be taken when a tracepoint is hit. @var{n} and
31187 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31188 this tracepoint. This packet may only be sent immediately after
31189 another @samp{QTDP} packet that ended with a @samp{-}. If the
31190 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31191 specifying more actions for this tracepoint.
31193 In the series of action packets for a given tracepoint, at most one
31194 can have an @samp{S} before its first @var{action}. If such a packet
31195 is sent, it and the following packets define ``while-stepping''
31196 actions. Any prior packets define ordinary actions --- that is, those
31197 taken when the tracepoint is first hit. If no action packet has an
31198 @samp{S}, then all the packets in the series specify ordinary
31199 tracepoint actions.
31201 The @samp{@var{action}@dots{}} portion of the packet is a series of
31202 actions, concatenated without separators. Each action has one of the
31208 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31209 a hexadecimal number whose @var{i}'th bit is set if register number
31210 @var{i} should be collected. (The least significant bit is numbered
31211 zero.) Note that @var{mask} may be any number of digits long; it may
31212 not fit in a 32-bit word.
31214 @item M @var{basereg},@var{offset},@var{len}
31215 Collect @var{len} bytes of memory starting at the address in register
31216 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31217 @samp{-1}, then the range has a fixed address: @var{offset} is the
31218 address of the lowest byte to collect. The @var{basereg},
31219 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31220 values (the @samp{-1} value for @var{basereg} is a special case).
31222 @item X @var{len},@var{expr}
31223 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31224 it directs. @var{expr} is an agent expression, as described in
31225 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31226 two-digit hex number in the packet; @var{len} is the number of bytes
31227 in the expression (and thus one-half the number of hex digits in the
31232 Any number of actions may be packed together in a single @samp{QTDP}
31233 packet, as long as the packet does not exceed the maximum packet
31234 length (400 bytes, for many stubs). There may be only one @samp{R}
31235 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31236 actions. Any registers referred to by @samp{M} and @samp{X} actions
31237 must be collected by a preceding @samp{R} action. (The
31238 ``while-stepping'' actions are treated as if they were attached to a
31239 separate tracepoint, as far as these restrictions are concerned.)
31244 The packet was understood and carried out.
31246 The packet was not recognized.
31249 @item QTDV:@var{n}:@var{value}
31250 @cindex define trace state variable, remote request
31251 @cindex @samp{QTDV} packet
31252 Create a new trace state variable, number @var{n}, with an initial
31253 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31254 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31255 the option of not using this packet for initial values of zero; the
31256 target should simply create the trace state variables as they are
31257 mentioned in expressions.
31259 @item QTFrame:@var{n}
31260 Select the @var{n}'th tracepoint frame from the buffer, and use the
31261 register and memory contents recorded there to answer subsequent
31262 request packets from @value{GDBN}.
31264 A successful reply from the stub indicates that the stub has found the
31265 requested frame. The response is a series of parts, concatenated
31266 without separators, describing the frame we selected. Each part has
31267 one of the following forms:
31271 The selected frame is number @var{n} in the trace frame buffer;
31272 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31273 was no frame matching the criteria in the request packet.
31276 The selected trace frame records a hit of tracepoint number @var{t};
31277 @var{t} is a hexadecimal number.
31281 @item QTFrame:pc:@var{addr}
31282 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31283 currently selected frame whose PC is @var{addr};
31284 @var{addr} is a hexadecimal number.
31286 @item QTFrame:tdp:@var{t}
31287 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31288 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31289 is a hexadecimal number.
31291 @item QTFrame:range:@var{start}:@var{end}
31292 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31293 currently selected frame whose PC is between @var{start} (inclusive)
31294 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
31297 @item QTFrame:outside:@var{start}:@var{end}
31298 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
31299 frame @emph{outside} the given range of addresses (exclusive).
31302 Begin the tracepoint experiment. Begin collecting data from tracepoint
31303 hits in the trace frame buffer.
31306 End the tracepoint experiment. Stop collecting trace frames.
31309 Clear the table of tracepoints, and empty the trace frame buffer.
31311 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
31312 Establish the given ranges of memory as ``transparent''. The stub
31313 will answer requests for these ranges from memory's current contents,
31314 if they were not collected as part of the tracepoint hit.
31316 @value{GDBN} uses this to mark read-only regions of memory, like those
31317 containing program code. Since these areas never change, they should
31318 still have the same contents they did when the tracepoint was hit, so
31319 there's no reason for the stub to refuse to provide their contents.
31321 @item QTDisconnected:@var{value}
31322 Set the choice to what to do with the tracing run when @value{GDBN}
31323 disconnects from the target. A @var{value} of 1 directs the target to
31324 continue the tracing run, while 0 tells the target to stop tracing if
31325 @value{GDBN} is no longer in the picture.
31328 Ask the stub if there is a trace experiment running right now.
31330 The reply has the form:
31334 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
31335 @var{running} is a single digit @code{1} if the trace is presently
31336 running, or @code{0} if not. It is followed by semicolon-separated
31337 optional fields that an agent may use to report additional status.
31341 If the trace is not running, the agent may report any of several
31342 explanations as one of the optional fields:
31347 No trace has been run yet.
31350 The trace was stopped by a user-originated stop command.
31353 The trace stopped because the trace buffer filled up.
31355 @item tdisconnected:0
31356 The trace stopped because @value{GDBN} disconnected from the target.
31358 @item tpasscount:@var{tpnum}
31359 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
31362 The trace stopped for some other reason.
31366 Additional optional fields supply statistical information. Although
31367 not required, they are extremely useful for users monitoring the
31368 progress of a trace run. If a trace has stopped, and these numbers
31369 are reported, they must reflect the state of the just-stopped trace.
31373 @item tframes:@var{n}
31374 The number of trace frames in the buffer.
31376 @item tcreated:@var{n}
31377 The total number of trace frames created during the run. This may
31378 be larger than the trace frame count, if the buffer is circular.
31380 @item tsize:@var{n}
31381 The total size of the trace buffer, in bytes.
31383 @item tfree:@var{n}
31384 The number of bytes still unused in the buffer.
31388 @item qTV:@var{var}
31389 @cindex trace state variable value, remote request
31390 @cindex @samp{qTV} packet
31391 Ask the stub for the value of the trace state variable number @var{var}.
31396 The value of the variable is @var{value}. This will be the current
31397 value of the variable if the user is examining a running target, or a
31398 saved value if the variable was collected in the trace frame that the
31399 user is looking at. Note that multiple requests may result in
31400 different reply values, such as when requesting values while the
31401 program is running.
31404 The value of the variable is unknown. This would occur, for example,
31405 if the user is examining a trace frame in which the requested variable
31411 These packets request data about tracepoints that are being used by
31412 the target. @value{GDBN} sends @code{qTfP} to get the first piece
31413 of data, and multiple @code{qTsP} to get additional pieces. Replies
31414 to these packets generally take the form of the @code{QTDP} packets
31415 that define tracepoints. (FIXME add detailed syntax)
31419 These packets request data about trace state variables that are on the
31420 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
31421 and multiple @code{qTsV} to get additional variables. Replies to
31422 these packets follow the syntax of the @code{QTDV} packets that define
31423 trace state variables.
31425 @item QTSave:@var{filename}
31426 This packet directs the target to save trace data to the file name
31427 @var{filename} in the target's filesystem. @var{filename} is encoded
31428 as a hex string; the interpretation of the file name (relative vs
31429 absolute, wild cards, etc) is up to the target.
31431 @item qTBuffer:@var{offset},@var{len}
31432 Return up to @var{len} bytes of the current contents of trace buffer,
31433 starting at @var{offset}. The trace buffer is treated as if it were
31434 a contiguous collection of traceframes, as per the trace file format.
31435 The reply consists as many hex-encoded bytes as the target can deliver
31436 in a packet; it is not an error to return fewer than were asked for.
31437 A reply consisting of just @code{l} indicates that no bytes are
31440 @item QTBuffer:circular:@var{value}
31441 This packet directs the target to use a circular trace buffer if
31442 @var{value} is 1, or a linear buffer if the value is 0.
31446 @node Host I/O Packets
31447 @section Host I/O Packets
31448 @cindex Host I/O, remote protocol
31449 @cindex file transfer, remote protocol
31451 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
31452 operations on the far side of a remote link. For example, Host I/O is
31453 used to upload and download files to a remote target with its own
31454 filesystem. Host I/O uses the same constant values and data structure
31455 layout as the target-initiated File-I/O protocol. However, the
31456 Host I/O packets are structured differently. The target-initiated
31457 protocol relies on target memory to store parameters and buffers.
31458 Host I/O requests are initiated by @value{GDBN}, and the
31459 target's memory is not involved. @xref{File-I/O Remote Protocol
31460 Extension}, for more details on the target-initiated protocol.
31462 The Host I/O request packets all encode a single operation along with
31463 its arguments. They have this format:
31467 @item vFile:@var{operation}: @var{parameter}@dots{}
31468 @var{operation} is the name of the particular request; the target
31469 should compare the entire packet name up to the second colon when checking
31470 for a supported operation. The format of @var{parameter} depends on
31471 the operation. Numbers are always passed in hexadecimal. Negative
31472 numbers have an explicit minus sign (i.e.@: two's complement is not
31473 used). Strings (e.g.@: filenames) are encoded as a series of
31474 hexadecimal bytes. The last argument to a system call may be a
31475 buffer of escaped binary data (@pxref{Binary Data}).
31479 The valid responses to Host I/O packets are:
31483 @item F @var{result} [, @var{errno}] [; @var{attachment}]
31484 @var{result} is the integer value returned by this operation, usually
31485 non-negative for success and -1 for errors. If an error has occured,
31486 @var{errno} will be included in the result. @var{errno} will have a
31487 value defined by the File-I/O protocol (@pxref{Errno Values}). For
31488 operations which return data, @var{attachment} supplies the data as a
31489 binary buffer. Binary buffers in response packets are escaped in the
31490 normal way (@pxref{Binary Data}). See the individual packet
31491 documentation for the interpretation of @var{result} and
31495 An empty response indicates that this operation is not recognized.
31499 These are the supported Host I/O operations:
31502 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
31503 Open a file at @var{pathname} and return a file descriptor for it, or
31504 return -1 if an error occurs. @var{pathname} is a string,
31505 @var{flags} is an integer indicating a mask of open flags
31506 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
31507 of mode bits to use if the file is created (@pxref{mode_t Values}).
31508 @xref{open}, for details of the open flags and mode values.
31510 @item vFile:close: @var{fd}
31511 Close the open file corresponding to @var{fd} and return 0, or
31512 -1 if an error occurs.
31514 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
31515 Read data from the open file corresponding to @var{fd}. Up to
31516 @var{count} bytes will be read from the file, starting at @var{offset}
31517 relative to the start of the file. The target may read fewer bytes;
31518 common reasons include packet size limits and an end-of-file
31519 condition. The number of bytes read is returned. Zero should only be
31520 returned for a successful read at the end of the file, or if
31521 @var{count} was zero.
31523 The data read should be returned as a binary attachment on success.
31524 If zero bytes were read, the response should include an empty binary
31525 attachment (i.e.@: a trailing semicolon). The return value is the
31526 number of target bytes read; the binary attachment may be longer if
31527 some characters were escaped.
31529 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
31530 Write @var{data} (a binary buffer) to the open file corresponding
31531 to @var{fd}. Start the write at @var{offset} from the start of the
31532 file. Unlike many @code{write} system calls, there is no
31533 separate @var{count} argument; the length of @var{data} in the
31534 packet is used. @samp{vFile:write} returns the number of bytes written,
31535 which may be shorter than the length of @var{data}, or -1 if an
31538 @item vFile:unlink: @var{pathname}
31539 Delete the file at @var{pathname} on the target. Return 0,
31540 or -1 if an error occurs. @var{pathname} is a string.
31545 @section Interrupts
31546 @cindex interrupts (remote protocol)
31548 When a program on the remote target is running, @value{GDBN} may
31549 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
31550 a @code{BREAK} followed by @code{g},
31551 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
31553 The precise meaning of @code{BREAK} is defined by the transport
31554 mechanism and may, in fact, be undefined. @value{GDBN} does not
31555 currently define a @code{BREAK} mechanism for any of the network
31556 interfaces except for TCP, in which case @value{GDBN} sends the
31557 @code{telnet} BREAK sequence.
31559 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
31560 transport mechanisms. It is represented by sending the single byte
31561 @code{0x03} without any of the usual packet overhead described in
31562 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
31563 transmitted as part of a packet, it is considered to be packet data
31564 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
31565 (@pxref{X packet}), used for binary downloads, may include an unescaped
31566 @code{0x03} as part of its packet.
31568 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
31569 When Linux kernel receives this sequence from serial port,
31570 it stops execution and connects to gdb.
31572 Stubs are not required to recognize these interrupt mechanisms and the
31573 precise meaning associated with receipt of the interrupt is
31574 implementation defined. If the target supports debugging of multiple
31575 threads and/or processes, it should attempt to interrupt all
31576 currently-executing threads and processes.
31577 If the stub is successful at interrupting the
31578 running program, it should send one of the stop
31579 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
31580 of successfully stopping the program in all-stop mode, and a stop reply
31581 for each stopped thread in non-stop mode.
31582 Interrupts received while the
31583 program is stopped are discarded.
31585 @node Notification Packets
31586 @section Notification Packets
31587 @cindex notification packets
31588 @cindex packets, notification
31590 The @value{GDBN} remote serial protocol includes @dfn{notifications},
31591 packets that require no acknowledgment. Both the GDB and the stub
31592 may send notifications (although the only notifications defined at
31593 present are sent by the stub). Notifications carry information
31594 without incurring the round-trip latency of an acknowledgment, and so
31595 are useful for low-impact communications where occasional packet loss
31598 A notification packet has the form @samp{% @var{data} #
31599 @var{checksum}}, where @var{data} is the content of the notification,
31600 and @var{checksum} is a checksum of @var{data}, computed and formatted
31601 as for ordinary @value{GDBN} packets. A notification's @var{data}
31602 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
31603 receiving a notification, the recipient sends no @samp{+} or @samp{-}
31604 to acknowledge the notification's receipt or to report its corruption.
31606 Every notification's @var{data} begins with a name, which contains no
31607 colon characters, followed by a colon character.
31609 Recipients should silently ignore corrupted notifications and
31610 notifications they do not understand. Recipients should restart
31611 timeout periods on receipt of a well-formed notification, whether or
31612 not they understand it.
31614 Senders should only send the notifications described here when this
31615 protocol description specifies that they are permitted. In the
31616 future, we may extend the protocol to permit existing notifications in
31617 new contexts; this rule helps older senders avoid confusing newer
31620 (Older versions of @value{GDBN} ignore bytes received until they see
31621 the @samp{$} byte that begins an ordinary packet, so new stubs may
31622 transmit notifications without fear of confusing older clients. There
31623 are no notifications defined for @value{GDBN} to send at the moment, but we
31624 assume that most older stubs would ignore them, as well.)
31626 The following notification packets from the stub to @value{GDBN} are
31630 @item Stop: @var{reply}
31631 Report an asynchronous stop event in non-stop mode.
31632 The @var{reply} has the form of a stop reply, as
31633 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
31634 for information on how these notifications are acknowledged by
31638 @node Remote Non-Stop
31639 @section Remote Protocol Support for Non-Stop Mode
31641 @value{GDBN}'s remote protocol supports non-stop debugging of
31642 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
31643 supports non-stop mode, it should report that to @value{GDBN} by including
31644 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
31646 @value{GDBN} typically sends a @samp{QNonStop} packet only when
31647 establishing a new connection with the stub. Entering non-stop mode
31648 does not alter the state of any currently-running threads, but targets
31649 must stop all threads in any already-attached processes when entering
31650 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
31651 probe the target state after a mode change.
31653 In non-stop mode, when an attached process encounters an event that
31654 would otherwise be reported with a stop reply, it uses the
31655 asynchronous notification mechanism (@pxref{Notification Packets}) to
31656 inform @value{GDBN}. In contrast to all-stop mode, where all threads
31657 in all processes are stopped when a stop reply is sent, in non-stop
31658 mode only the thread reporting the stop event is stopped. That is,
31659 when reporting a @samp{S} or @samp{T} response to indicate completion
31660 of a step operation, hitting a breakpoint, or a fault, only the
31661 affected thread is stopped; any other still-running threads continue
31662 to run. When reporting a @samp{W} or @samp{X} response, all running
31663 threads belonging to other attached processes continue to run.
31665 Only one stop reply notification at a time may be pending; if
31666 additional stop events occur before @value{GDBN} has acknowledged the
31667 previous notification, they must be queued by the stub for later
31668 synchronous transmission in response to @samp{vStopped} packets from
31669 @value{GDBN}. Because the notification mechanism is unreliable,
31670 the stub is permitted to resend a stop reply notification
31671 if it believes @value{GDBN} may not have received it. @value{GDBN}
31672 ignores additional stop reply notifications received before it has
31673 finished processing a previous notification and the stub has completed
31674 sending any queued stop events.
31676 Otherwise, @value{GDBN} must be prepared to receive a stop reply
31677 notification at any time. Specifically, they may appear when
31678 @value{GDBN} is not otherwise reading input from the stub, or when
31679 @value{GDBN} is expecting to read a normal synchronous response or a
31680 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
31681 Notification packets are distinct from any other communication from
31682 the stub so there is no ambiguity.
31684 After receiving a stop reply notification, @value{GDBN} shall
31685 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
31686 as a regular, synchronous request to the stub. Such acknowledgment
31687 is not required to happen immediately, as @value{GDBN} is permitted to
31688 send other, unrelated packets to the stub first, which the stub should
31691 Upon receiving a @samp{vStopped} packet, if the stub has other queued
31692 stop events to report to @value{GDBN}, it shall respond by sending a
31693 normal stop reply response. @value{GDBN} shall then send another
31694 @samp{vStopped} packet to solicit further responses; again, it is
31695 permitted to send other, unrelated packets as well which the stub
31696 should process normally.
31698 If the stub receives a @samp{vStopped} packet and there are no
31699 additional stop events to report, the stub shall return an @samp{OK}
31700 response. At this point, if further stop events occur, the stub shall
31701 send a new stop reply notification, @value{GDBN} shall accept the
31702 notification, and the process shall be repeated.
31704 In non-stop mode, the target shall respond to the @samp{?} packet as
31705 follows. First, any incomplete stop reply notification/@samp{vStopped}
31706 sequence in progress is abandoned. The target must begin a new
31707 sequence reporting stop events for all stopped threads, whether or not
31708 it has previously reported those events to @value{GDBN}. The first
31709 stop reply is sent as a synchronous reply to the @samp{?} packet, and
31710 subsequent stop replies are sent as responses to @samp{vStopped} packets
31711 using the mechanism described above. The target must not send
31712 asynchronous stop reply notifications until the sequence is complete.
31713 If all threads are running when the target receives the @samp{?} packet,
31714 or if the target is not attached to any process, it shall respond
31717 @node Packet Acknowledgment
31718 @section Packet Acknowledgment
31720 @cindex acknowledgment, for @value{GDBN} remote
31721 @cindex packet acknowledgment, for @value{GDBN} remote
31722 By default, when either the host or the target machine receives a packet,
31723 the first response expected is an acknowledgment: either @samp{+} (to indicate
31724 the package was received correctly) or @samp{-} (to request retransmission).
31725 This mechanism allows the @value{GDBN} remote protocol to operate over
31726 unreliable transport mechanisms, such as a serial line.
31728 In cases where the transport mechanism is itself reliable (such as a pipe or
31729 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
31730 It may be desirable to disable them in that case to reduce communication
31731 overhead, or for other reasons. This can be accomplished by means of the
31732 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
31734 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
31735 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
31736 and response format still includes the normal checksum, as described in
31737 @ref{Overview}, but the checksum may be ignored by the receiver.
31739 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
31740 no-acknowledgment mode, it should report that to @value{GDBN}
31741 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
31742 @pxref{qSupported}.
31743 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
31744 disabled via the @code{set remote noack-packet off} command
31745 (@pxref{Remote Configuration}),
31746 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
31747 Only then may the stub actually turn off packet acknowledgments.
31748 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
31749 response, which can be safely ignored by the stub.
31751 Note that @code{set remote noack-packet} command only affects negotiation
31752 between @value{GDBN} and the stub when subsequent connections are made;
31753 it does not affect the protocol acknowledgment state for any current
31755 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
31756 new connection is established,
31757 there is also no protocol request to re-enable the acknowledgments
31758 for the current connection, once disabled.
31763 Example sequence of a target being re-started. Notice how the restart
31764 does not get any direct output:
31769 @emph{target restarts}
31772 <- @code{T001:1234123412341234}
31776 Example sequence of a target being stepped by a single instruction:
31779 -> @code{G1445@dots{}}
31784 <- @code{T001:1234123412341234}
31788 <- @code{1455@dots{}}
31792 @node File-I/O Remote Protocol Extension
31793 @section File-I/O Remote Protocol Extension
31794 @cindex File-I/O remote protocol extension
31797 * File-I/O Overview::
31798 * Protocol Basics::
31799 * The F Request Packet::
31800 * The F Reply Packet::
31801 * The Ctrl-C Message::
31803 * List of Supported Calls::
31804 * Protocol-specific Representation of Datatypes::
31806 * File-I/O Examples::
31809 @node File-I/O Overview
31810 @subsection File-I/O Overview
31811 @cindex file-i/o overview
31813 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
31814 target to use the host's file system and console I/O to perform various
31815 system calls. System calls on the target system are translated into a
31816 remote protocol packet to the host system, which then performs the needed
31817 actions and returns a response packet to the target system.
31818 This simulates file system operations even on targets that lack file systems.
31820 The protocol is defined to be independent of both the host and target systems.
31821 It uses its own internal representation of datatypes and values. Both
31822 @value{GDBN} and the target's @value{GDBN} stub are responsible for
31823 translating the system-dependent value representations into the internal
31824 protocol representations when data is transmitted.
31826 The communication is synchronous. A system call is possible only when
31827 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
31828 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
31829 the target is stopped to allow deterministic access to the target's
31830 memory. Therefore File-I/O is not interruptible by target signals. On
31831 the other hand, it is possible to interrupt File-I/O by a user interrupt
31832 (@samp{Ctrl-C}) within @value{GDBN}.
31834 The target's request to perform a host system call does not finish
31835 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
31836 after finishing the system call, the target returns to continuing the
31837 previous activity (continue, step). No additional continue or step
31838 request from @value{GDBN} is required.
31841 (@value{GDBP}) continue
31842 <- target requests 'system call X'
31843 target is stopped, @value{GDBN} executes system call
31844 -> @value{GDBN} returns result
31845 ... target continues, @value{GDBN} returns to wait for the target
31846 <- target hits breakpoint and sends a Txx packet
31849 The protocol only supports I/O on the console and to regular files on
31850 the host file system. Character or block special devices, pipes,
31851 named pipes, sockets or any other communication method on the host
31852 system are not supported by this protocol.
31854 File I/O is not supported in non-stop mode.
31856 @node Protocol Basics
31857 @subsection Protocol Basics
31858 @cindex protocol basics, file-i/o
31860 The File-I/O protocol uses the @code{F} packet as the request as well
31861 as reply packet. Since a File-I/O system call can only occur when
31862 @value{GDBN} is waiting for a response from the continuing or stepping target,
31863 the File-I/O request is a reply that @value{GDBN} has to expect as a result
31864 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
31865 This @code{F} packet contains all information needed to allow @value{GDBN}
31866 to call the appropriate host system call:
31870 A unique identifier for the requested system call.
31873 All parameters to the system call. Pointers are given as addresses
31874 in the target memory address space. Pointers to strings are given as
31875 pointer/length pair. Numerical values are given as they are.
31876 Numerical control flags are given in a protocol-specific representation.
31880 At this point, @value{GDBN} has to perform the following actions.
31884 If the parameters include pointer values to data needed as input to a
31885 system call, @value{GDBN} requests this data from the target with a
31886 standard @code{m} packet request. This additional communication has to be
31887 expected by the target implementation and is handled as any other @code{m}
31891 @value{GDBN} translates all value from protocol representation to host
31892 representation as needed. Datatypes are coerced into the host types.
31895 @value{GDBN} calls the system call.
31898 It then coerces datatypes back to protocol representation.
31901 If the system call is expected to return data in buffer space specified
31902 by pointer parameters to the call, the data is transmitted to the
31903 target using a @code{M} or @code{X} packet. This packet has to be expected
31904 by the target implementation and is handled as any other @code{M} or @code{X}
31909 Eventually @value{GDBN} replies with another @code{F} packet which contains all
31910 necessary information for the target to continue. This at least contains
31917 @code{errno}, if has been changed by the system call.
31924 After having done the needed type and value coercion, the target continues
31925 the latest continue or step action.
31927 @node The F Request Packet
31928 @subsection The @code{F} Request Packet
31929 @cindex file-i/o request packet
31930 @cindex @code{F} request packet
31932 The @code{F} request packet has the following format:
31935 @item F@var{call-id},@var{parameter@dots{}}
31937 @var{call-id} is the identifier to indicate the host system call to be called.
31938 This is just the name of the function.
31940 @var{parameter@dots{}} are the parameters to the system call.
31941 Parameters are hexadecimal integer values, either the actual values in case
31942 of scalar datatypes, pointers to target buffer space in case of compound
31943 datatypes and unspecified memory areas, or pointer/length pairs in case
31944 of string parameters. These are appended to the @var{call-id} as a
31945 comma-delimited list. All values are transmitted in ASCII
31946 string representation, pointer/length pairs separated by a slash.
31952 @node The F Reply Packet
31953 @subsection The @code{F} Reply Packet
31954 @cindex file-i/o reply packet
31955 @cindex @code{F} reply packet
31957 The @code{F} reply packet has the following format:
31961 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
31963 @var{retcode} is the return code of the system call as hexadecimal value.
31965 @var{errno} is the @code{errno} set by the call, in protocol-specific
31967 This parameter can be omitted if the call was successful.
31969 @var{Ctrl-C flag} is only sent if the user requested a break. In this
31970 case, @var{errno} must be sent as well, even if the call was successful.
31971 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
31978 or, if the call was interrupted before the host call has been performed:
31985 assuming 4 is the protocol-specific representation of @code{EINTR}.
31990 @node The Ctrl-C Message
31991 @subsection The @samp{Ctrl-C} Message
31992 @cindex ctrl-c message, in file-i/o protocol
31994 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
31995 reply packet (@pxref{The F Reply Packet}),
31996 the target should behave as if it had
31997 gotten a break message. The meaning for the target is ``system call
31998 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
31999 (as with a break message) and return to @value{GDBN} with a @code{T02}
32002 It's important for the target to know in which
32003 state the system call was interrupted. There are two possible cases:
32007 The system call hasn't been performed on the host yet.
32010 The system call on the host has been finished.
32014 These two states can be distinguished by the target by the value of the
32015 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32016 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32017 on POSIX systems. In any other case, the target may presume that the
32018 system call has been finished --- successfully or not --- and should behave
32019 as if the break message arrived right after the system call.
32021 @value{GDBN} must behave reliably. If the system call has not been called
32022 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32023 @code{errno} in the packet. If the system call on the host has been finished
32024 before the user requests a break, the full action must be finished by
32025 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32026 The @code{F} packet may only be sent when either nothing has happened
32027 or the full action has been completed.
32030 @subsection Console I/O
32031 @cindex console i/o as part of file-i/o
32033 By default and if not explicitly closed by the target system, the file
32034 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32035 on the @value{GDBN} console is handled as any other file output operation
32036 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32037 by @value{GDBN} so that after the target read request from file descriptor
32038 0 all following typing is buffered until either one of the following
32043 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32045 system call is treated as finished.
32048 The user presses @key{RET}. This is treated as end of input with a trailing
32052 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32053 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32057 If the user has typed more characters than fit in the buffer given to
32058 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32059 either another @code{read(0, @dots{})} is requested by the target, or debugging
32060 is stopped at the user's request.
32063 @node List of Supported Calls
32064 @subsection List of Supported Calls
32065 @cindex list of supported file-i/o calls
32082 @unnumberedsubsubsec open
32083 @cindex open, file-i/o system call
32088 int open(const char *pathname, int flags);
32089 int open(const char *pathname, int flags, mode_t mode);
32093 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32096 @var{flags} is the bitwise @code{OR} of the following values:
32100 If the file does not exist it will be created. The host
32101 rules apply as far as file ownership and time stamps
32105 When used with @code{O_CREAT}, if the file already exists it is
32106 an error and open() fails.
32109 If the file already exists and the open mode allows
32110 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32111 truncated to zero length.
32114 The file is opened in append mode.
32117 The file is opened for reading only.
32120 The file is opened for writing only.
32123 The file is opened for reading and writing.
32127 Other bits are silently ignored.
32131 @var{mode} is the bitwise @code{OR} of the following values:
32135 User has read permission.
32138 User has write permission.
32141 Group has read permission.
32144 Group has write permission.
32147 Others have read permission.
32150 Others have write permission.
32154 Other bits are silently ignored.
32157 @item Return value:
32158 @code{open} returns the new file descriptor or -1 if an error
32165 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32168 @var{pathname} refers to a directory.
32171 The requested access is not allowed.
32174 @var{pathname} was too long.
32177 A directory component in @var{pathname} does not exist.
32180 @var{pathname} refers to a device, pipe, named pipe or socket.
32183 @var{pathname} refers to a file on a read-only filesystem and
32184 write access was requested.
32187 @var{pathname} is an invalid pointer value.
32190 No space on device to create the file.
32193 The process already has the maximum number of files open.
32196 The limit on the total number of files open on the system
32200 The call was interrupted by the user.
32206 @unnumberedsubsubsec close
32207 @cindex close, file-i/o system call
32216 @samp{Fclose,@var{fd}}
32218 @item Return value:
32219 @code{close} returns zero on success, or -1 if an error occurred.
32225 @var{fd} isn't a valid open file descriptor.
32228 The call was interrupted by the user.
32234 @unnumberedsubsubsec read
32235 @cindex read, file-i/o system call
32240 int read(int fd, void *buf, unsigned int count);
32244 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32246 @item Return value:
32247 On success, the number of bytes read is returned.
32248 Zero indicates end of file. If count is zero, read
32249 returns zero as well. On error, -1 is returned.
32255 @var{fd} is not a valid file descriptor or is not open for
32259 @var{bufptr} is an invalid pointer value.
32262 The call was interrupted by the user.
32268 @unnumberedsubsubsec write
32269 @cindex write, file-i/o system call
32274 int write(int fd, const void *buf, unsigned int count);
32278 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
32280 @item Return value:
32281 On success, the number of bytes written are returned.
32282 Zero indicates nothing was written. On error, -1
32289 @var{fd} is not a valid file descriptor or is not open for
32293 @var{bufptr} is an invalid pointer value.
32296 An attempt was made to write a file that exceeds the
32297 host-specific maximum file size allowed.
32300 No space on device to write the data.
32303 The call was interrupted by the user.
32309 @unnumberedsubsubsec lseek
32310 @cindex lseek, file-i/o system call
32315 long lseek (int fd, long offset, int flag);
32319 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
32321 @var{flag} is one of:
32325 The offset is set to @var{offset} bytes.
32328 The offset is set to its current location plus @var{offset}
32332 The offset is set to the size of the file plus @var{offset}
32336 @item Return value:
32337 On success, the resulting unsigned offset in bytes from
32338 the beginning of the file is returned. Otherwise, a
32339 value of -1 is returned.
32345 @var{fd} is not a valid open file descriptor.
32348 @var{fd} is associated with the @value{GDBN} console.
32351 @var{flag} is not a proper value.
32354 The call was interrupted by the user.
32360 @unnumberedsubsubsec rename
32361 @cindex rename, file-i/o system call
32366 int rename(const char *oldpath, const char *newpath);
32370 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
32372 @item Return value:
32373 On success, zero is returned. On error, -1 is returned.
32379 @var{newpath} is an existing directory, but @var{oldpath} is not a
32383 @var{newpath} is a non-empty directory.
32386 @var{oldpath} or @var{newpath} is a directory that is in use by some
32390 An attempt was made to make a directory a subdirectory
32394 A component used as a directory in @var{oldpath} or new
32395 path is not a directory. Or @var{oldpath} is a directory
32396 and @var{newpath} exists but is not a directory.
32399 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
32402 No access to the file or the path of the file.
32406 @var{oldpath} or @var{newpath} was too long.
32409 A directory component in @var{oldpath} or @var{newpath} does not exist.
32412 The file is on a read-only filesystem.
32415 The device containing the file has no room for the new
32419 The call was interrupted by the user.
32425 @unnumberedsubsubsec unlink
32426 @cindex unlink, file-i/o system call
32431 int unlink(const char *pathname);
32435 @samp{Funlink,@var{pathnameptr}/@var{len}}
32437 @item Return value:
32438 On success, zero is returned. On error, -1 is returned.
32444 No access to the file or the path of the file.
32447 The system does not allow unlinking of directories.
32450 The file @var{pathname} cannot be unlinked because it's
32451 being used by another process.
32454 @var{pathnameptr} is an invalid pointer value.
32457 @var{pathname} was too long.
32460 A directory component in @var{pathname} does not exist.
32463 A component of the path is not a directory.
32466 The file is on a read-only filesystem.
32469 The call was interrupted by the user.
32475 @unnumberedsubsubsec stat/fstat
32476 @cindex fstat, file-i/o system call
32477 @cindex stat, file-i/o system call
32482 int stat(const char *pathname, struct stat *buf);
32483 int fstat(int fd, struct stat *buf);
32487 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
32488 @samp{Ffstat,@var{fd},@var{bufptr}}
32490 @item Return value:
32491 On success, zero is returned. On error, -1 is returned.
32497 @var{fd} is not a valid open file.
32500 A directory component in @var{pathname} does not exist or the
32501 path is an empty string.
32504 A component of the path is not a directory.
32507 @var{pathnameptr} is an invalid pointer value.
32510 No access to the file or the path of the file.
32513 @var{pathname} was too long.
32516 The call was interrupted by the user.
32522 @unnumberedsubsubsec gettimeofday
32523 @cindex gettimeofday, file-i/o system call
32528 int gettimeofday(struct timeval *tv, void *tz);
32532 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
32534 @item Return value:
32535 On success, 0 is returned, -1 otherwise.
32541 @var{tz} is a non-NULL pointer.
32544 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
32550 @unnumberedsubsubsec isatty
32551 @cindex isatty, file-i/o system call
32556 int isatty(int fd);
32560 @samp{Fisatty,@var{fd}}
32562 @item Return value:
32563 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
32569 The call was interrupted by the user.
32574 Note that the @code{isatty} call is treated as a special case: it returns
32575 1 to the target if the file descriptor is attached
32576 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
32577 would require implementing @code{ioctl} and would be more complex than
32582 @unnumberedsubsubsec system
32583 @cindex system, file-i/o system call
32588 int system(const char *command);
32592 @samp{Fsystem,@var{commandptr}/@var{len}}
32594 @item Return value:
32595 If @var{len} is zero, the return value indicates whether a shell is
32596 available. A zero return value indicates a shell is not available.
32597 For non-zero @var{len}, the value returned is -1 on error and the
32598 return status of the command otherwise. Only the exit status of the
32599 command is returned, which is extracted from the host's @code{system}
32600 return value by calling @code{WEXITSTATUS(retval)}. In case
32601 @file{/bin/sh} could not be executed, 127 is returned.
32607 The call was interrupted by the user.
32612 @value{GDBN} takes over the full task of calling the necessary host calls
32613 to perform the @code{system} call. The return value of @code{system} on
32614 the host is simplified before it's returned
32615 to the target. Any termination signal information from the child process
32616 is discarded, and the return value consists
32617 entirely of the exit status of the called command.
32619 Due to security concerns, the @code{system} call is by default refused
32620 by @value{GDBN}. The user has to allow this call explicitly with the
32621 @code{set remote system-call-allowed 1} command.
32624 @item set remote system-call-allowed
32625 @kindex set remote system-call-allowed
32626 Control whether to allow the @code{system} calls in the File I/O
32627 protocol for the remote target. The default is zero (disabled).
32629 @item show remote system-call-allowed
32630 @kindex show remote system-call-allowed
32631 Show whether the @code{system} calls are allowed in the File I/O
32635 @node Protocol-specific Representation of Datatypes
32636 @subsection Protocol-specific Representation of Datatypes
32637 @cindex protocol-specific representation of datatypes, in file-i/o protocol
32640 * Integral Datatypes::
32642 * Memory Transfer::
32647 @node Integral Datatypes
32648 @unnumberedsubsubsec Integral Datatypes
32649 @cindex integral datatypes, in file-i/o protocol
32651 The integral datatypes used in the system calls are @code{int},
32652 @code{unsigned int}, @code{long}, @code{unsigned long},
32653 @code{mode_t}, and @code{time_t}.
32655 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
32656 implemented as 32 bit values in this protocol.
32658 @code{long} and @code{unsigned long} are implemented as 64 bit types.
32660 @xref{Limits}, for corresponding MIN and MAX values (similar to those
32661 in @file{limits.h}) to allow range checking on host and target.
32663 @code{time_t} datatypes are defined as seconds since the Epoch.
32665 All integral datatypes transferred as part of a memory read or write of a
32666 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
32669 @node Pointer Values
32670 @unnumberedsubsubsec Pointer Values
32671 @cindex pointer values, in file-i/o protocol
32673 Pointers to target data are transmitted as they are. An exception
32674 is made for pointers to buffers for which the length isn't
32675 transmitted as part of the function call, namely strings. Strings
32676 are transmitted as a pointer/length pair, both as hex values, e.g.@:
32683 which is a pointer to data of length 18 bytes at position 0x1aaf.
32684 The length is defined as the full string length in bytes, including
32685 the trailing null byte. For example, the string @code{"hello world"}
32686 at address 0x123456 is transmitted as
32692 @node Memory Transfer
32693 @unnumberedsubsubsec Memory Transfer
32694 @cindex memory transfer, in file-i/o protocol
32696 Structured data which is transferred using a memory read or write (for
32697 example, a @code{struct stat}) is expected to be in a protocol-specific format
32698 with all scalar multibyte datatypes being big endian. Translation to
32699 this representation needs to be done both by the target before the @code{F}
32700 packet is sent, and by @value{GDBN} before
32701 it transfers memory to the target. Transferred pointers to structured
32702 data should point to the already-coerced data at any time.
32706 @unnumberedsubsubsec struct stat
32707 @cindex struct stat, in file-i/o protocol
32709 The buffer of type @code{struct stat} used by the target and @value{GDBN}
32710 is defined as follows:
32714 unsigned int st_dev; /* device */
32715 unsigned int st_ino; /* inode */
32716 mode_t st_mode; /* protection */
32717 unsigned int st_nlink; /* number of hard links */
32718 unsigned int st_uid; /* user ID of owner */
32719 unsigned int st_gid; /* group ID of owner */
32720 unsigned int st_rdev; /* device type (if inode device) */
32721 unsigned long st_size; /* total size, in bytes */
32722 unsigned long st_blksize; /* blocksize for filesystem I/O */
32723 unsigned long st_blocks; /* number of blocks allocated */
32724 time_t st_atime; /* time of last access */
32725 time_t st_mtime; /* time of last modification */
32726 time_t st_ctime; /* time of last change */
32730 The integral datatypes conform to the definitions given in the
32731 appropriate section (see @ref{Integral Datatypes}, for details) so this
32732 structure is of size 64 bytes.
32734 The values of several fields have a restricted meaning and/or
32740 A value of 0 represents a file, 1 the console.
32743 No valid meaning for the target. Transmitted unchanged.
32746 Valid mode bits are described in @ref{Constants}. Any other
32747 bits have currently no meaning for the target.
32752 No valid meaning for the target. Transmitted unchanged.
32757 These values have a host and file system dependent
32758 accuracy. Especially on Windows hosts, the file system may not
32759 support exact timing values.
32762 The target gets a @code{struct stat} of the above representation and is
32763 responsible for coercing it to the target representation before
32766 Note that due to size differences between the host, target, and protocol
32767 representations of @code{struct stat} members, these members could eventually
32768 get truncated on the target.
32770 @node struct timeval
32771 @unnumberedsubsubsec struct timeval
32772 @cindex struct timeval, in file-i/o protocol
32774 The buffer of type @code{struct timeval} used by the File-I/O protocol
32775 is defined as follows:
32779 time_t tv_sec; /* second */
32780 long tv_usec; /* microsecond */
32784 The integral datatypes conform to the definitions given in the
32785 appropriate section (see @ref{Integral Datatypes}, for details) so this
32786 structure is of size 8 bytes.
32789 @subsection Constants
32790 @cindex constants, in file-i/o protocol
32792 The following values are used for the constants inside of the
32793 protocol. @value{GDBN} and target are responsible for translating these
32794 values before and after the call as needed.
32805 @unnumberedsubsubsec Open Flags
32806 @cindex open flags, in file-i/o protocol
32808 All values are given in hexadecimal representation.
32820 @node mode_t Values
32821 @unnumberedsubsubsec mode_t Values
32822 @cindex mode_t values, in file-i/o protocol
32824 All values are given in octal representation.
32841 @unnumberedsubsubsec Errno Values
32842 @cindex errno values, in file-i/o protocol
32844 All values are given in decimal representation.
32869 @code{EUNKNOWN} is used as a fallback error value if a host system returns
32870 any error value not in the list of supported error numbers.
32873 @unnumberedsubsubsec Lseek Flags
32874 @cindex lseek flags, in file-i/o protocol
32883 @unnumberedsubsubsec Limits
32884 @cindex limits, in file-i/o protocol
32886 All values are given in decimal representation.
32889 INT_MIN -2147483648
32891 UINT_MAX 4294967295
32892 LONG_MIN -9223372036854775808
32893 LONG_MAX 9223372036854775807
32894 ULONG_MAX 18446744073709551615
32897 @node File-I/O Examples
32898 @subsection File-I/O Examples
32899 @cindex file-i/o examples
32901 Example sequence of a write call, file descriptor 3, buffer is at target
32902 address 0x1234, 6 bytes should be written:
32905 <- @code{Fwrite,3,1234,6}
32906 @emph{request memory read from target}
32909 @emph{return "6 bytes written"}
32913 Example sequence of a read call, file descriptor 3, buffer is at target
32914 address 0x1234, 6 bytes should be read:
32917 <- @code{Fread,3,1234,6}
32918 @emph{request memory write to target}
32919 -> @code{X1234,6:XXXXXX}
32920 @emph{return "6 bytes read"}
32924 Example sequence of a read call, call fails on the host due to invalid
32925 file descriptor (@code{EBADF}):
32928 <- @code{Fread,3,1234,6}
32932 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
32936 <- @code{Fread,3,1234,6}
32941 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
32945 <- @code{Fread,3,1234,6}
32946 -> @code{X1234,6:XXXXXX}
32950 @node Library List Format
32951 @section Library List Format
32952 @cindex library list format, remote protocol
32954 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
32955 same process as your application to manage libraries. In this case,
32956 @value{GDBN} can use the loader's symbol table and normal memory
32957 operations to maintain a list of shared libraries. On other
32958 platforms, the operating system manages loaded libraries.
32959 @value{GDBN} can not retrieve the list of currently loaded libraries
32960 through memory operations, so it uses the @samp{qXfer:libraries:read}
32961 packet (@pxref{qXfer library list read}) instead. The remote stub
32962 queries the target's operating system and reports which libraries
32965 The @samp{qXfer:libraries:read} packet returns an XML document which
32966 lists loaded libraries and their offsets. Each library has an
32967 associated name and one or more segment or section base addresses,
32968 which report where the library was loaded in memory.
32970 For the common case of libraries that are fully linked binaries, the
32971 library should have a list of segments. If the target supports
32972 dynamic linking of a relocatable object file, its library XML element
32973 should instead include a list of allocated sections. The segment or
32974 section bases are start addresses, not relocation offsets; they do not
32975 depend on the library's link-time base addresses.
32977 @value{GDBN} must be linked with the Expat library to support XML
32978 library lists. @xref{Expat}.
32980 A simple memory map, with one loaded library relocated by a single
32981 offset, looks like this:
32985 <library name="/lib/libc.so.6">
32986 <segment address="0x10000000"/>
32991 Another simple memory map, with one loaded library with three
32992 allocated sections (.text, .data, .bss), looks like this:
32996 <library name="sharedlib.o">
32997 <section address="0x10000000"/>
32998 <section address="0x20000000"/>
32999 <section address="0x30000000"/>
33004 The format of a library list is described by this DTD:
33007 <!-- library-list: Root element with versioning -->
33008 <!ELEMENT library-list (library)*>
33009 <!ATTLIST library-list version CDATA #FIXED "1.0">
33010 <!ELEMENT library (segment*, section*)>
33011 <!ATTLIST library name CDATA #REQUIRED>
33012 <!ELEMENT segment EMPTY>
33013 <!ATTLIST segment address CDATA #REQUIRED>
33014 <!ELEMENT section EMPTY>
33015 <!ATTLIST section address CDATA #REQUIRED>
33018 In addition, segments and section descriptors cannot be mixed within a
33019 single library element, and you must supply at least one segment or
33020 section for each library.
33022 @node Memory Map Format
33023 @section Memory Map Format
33024 @cindex memory map format
33026 To be able to write into flash memory, @value{GDBN} needs to obtain a
33027 memory map from the target. This section describes the format of the
33030 The memory map is obtained using the @samp{qXfer:memory-map:read}
33031 (@pxref{qXfer memory map read}) packet and is an XML document that
33032 lists memory regions.
33034 @value{GDBN} must be linked with the Expat library to support XML
33035 memory maps. @xref{Expat}.
33037 The top-level structure of the document is shown below:
33040 <?xml version="1.0"?>
33041 <!DOCTYPE memory-map
33042 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33043 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33049 Each region can be either:
33054 A region of RAM starting at @var{addr} and extending for @var{length}
33058 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33063 A region of read-only memory:
33066 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33071 A region of flash memory, with erasure blocks @var{blocksize}
33075 <memory type="flash" start="@var{addr}" length="@var{length}">
33076 <property name="blocksize">@var{blocksize}</property>
33082 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33083 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33084 packets to write to addresses in such ranges.
33086 The formal DTD for memory map format is given below:
33089 <!-- ................................................... -->
33090 <!-- Memory Map XML DTD ................................ -->
33091 <!-- File: memory-map.dtd .............................. -->
33092 <!-- .................................... .............. -->
33093 <!-- memory-map.dtd -->
33094 <!-- memory-map: Root element with versioning -->
33095 <!ELEMENT memory-map (memory | property)>
33096 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33097 <!ELEMENT memory (property)>
33098 <!-- memory: Specifies a memory region,
33099 and its type, or device. -->
33100 <!ATTLIST memory type CDATA #REQUIRED
33101 start CDATA #REQUIRED
33102 length CDATA #REQUIRED
33103 device CDATA #IMPLIED>
33104 <!-- property: Generic attribute tag -->
33105 <!ELEMENT property (#PCDATA | property)*>
33106 <!ATTLIST property name CDATA #REQUIRED>
33109 @node Thread List Format
33110 @section Thread List Format
33111 @cindex thread list format
33113 To efficiently update the list of threads and their attributes,
33114 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33115 (@pxref{qXfer threads read}) and obtains the XML document with
33116 the following structure:
33119 <?xml version="1.0"?>
33121 <thread id="id" core="0">
33122 ... description ...
33127 Each @samp{thread} element must have the @samp{id} attribute that
33128 identifies the thread (@pxref{thread-id syntax}). The
33129 @samp{core} attribute, if present, specifies which processor core
33130 the thread was last executing on. The content of the of @samp{thread}
33131 element is interpreted as human-readable auxilliary information.
33133 @include agentexpr.texi
33135 @node Trace File Format
33136 @appendix Trace File Format
33137 @cindex trace file format
33139 The trace file comes in three parts: a header, a textual description
33140 section, and a trace frame section with binary data.
33142 The header has the form @code{\x7fTRACE0\n}. The first byte is
33143 @code{0x7f} so as to indicate that the file contains binary data,
33144 while the @code{0} is a version number that may have different values
33147 The description section consists of multiple lines of @sc{ascii} text
33148 separated by newline characters (@code{0xa}). The lines may include a
33149 variety of optional descriptive or context-setting information, such
33150 as tracepoint definitions or register set size. @value{GDBN} will
33151 ignore any line that it does not recognize. An empty line marks the end
33154 @c FIXME add some specific types of data
33156 The trace frame section consists of a number of consecutive frames.
33157 Each frame begins with a two-byte tracepoint number, followed by a
33158 four-byte size giving the amount of data in the frame. The data in
33159 the frame consists of a number of blocks, each introduced by a
33160 character indicating its type (at least register, memory, and trace
33161 state variable). The data in this section is raw binary, not a
33162 hexadecimal or other encoding; its endianness matches the target's
33165 @c FIXME bi-arch may require endianness/arch info in description section
33168 @item R @var{bytes}
33169 Register block. The number and ordering of bytes matches that of a
33170 @code{g} packet in the remote protocol. Note that these are the
33171 actual bytes, in target order and @value{GDBN} register order, not a
33172 hexadecimal encoding.
33174 @item M @var{address} @var{length} @var{bytes}...
33175 Memory block. This is a contiguous block of memory, at the 8-byte
33176 address @var{address}, with a 2-byte length @var{length}, followed by
33177 @var{length} bytes.
33179 @item V @var{number} @var{value}
33180 Trace state variable block. This records the 8-byte signed value
33181 @var{value} of trace state variable numbered @var{number}.
33185 Future enhancements of the trace file format may include additional types
33188 @node Target Descriptions
33189 @appendix Target Descriptions
33190 @cindex target descriptions
33192 @strong{Warning:} target descriptions are still under active development,
33193 and the contents and format may change between @value{GDBN} releases.
33194 The format is expected to stabilize in the future.
33196 One of the challenges of using @value{GDBN} to debug embedded systems
33197 is that there are so many minor variants of each processor
33198 architecture in use. It is common practice for vendors to start with
33199 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33200 and then make changes to adapt it to a particular market niche. Some
33201 architectures have hundreds of variants, available from dozens of
33202 vendors. This leads to a number of problems:
33206 With so many different customized processors, it is difficult for
33207 the @value{GDBN} maintainers to keep up with the changes.
33209 Since individual variants may have short lifetimes or limited
33210 audiences, it may not be worthwhile to carry information about every
33211 variant in the @value{GDBN} source tree.
33213 When @value{GDBN} does support the architecture of the embedded system
33214 at hand, the task of finding the correct architecture name to give the
33215 @command{set architecture} command can be error-prone.
33218 To address these problems, the @value{GDBN} remote protocol allows a
33219 target system to not only identify itself to @value{GDBN}, but to
33220 actually describe its own features. This lets @value{GDBN} support
33221 processor variants it has never seen before --- to the extent that the
33222 descriptions are accurate, and that @value{GDBN} understands them.
33224 @value{GDBN} must be linked with the Expat library to support XML
33225 target descriptions. @xref{Expat}.
33228 * Retrieving Descriptions:: How descriptions are fetched from a target.
33229 * Target Description Format:: The contents of a target description.
33230 * Predefined Target Types:: Standard types available for target
33232 * Standard Target Features:: Features @value{GDBN} knows about.
33235 @node Retrieving Descriptions
33236 @section Retrieving Descriptions
33238 Target descriptions can be read from the target automatically, or
33239 specified by the user manually. The default behavior is to read the
33240 description from the target. @value{GDBN} retrieves it via the remote
33241 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33242 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33243 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33244 XML document, of the form described in @ref{Target Description
33247 Alternatively, you can specify a file to read for the target description.
33248 If a file is set, the target will not be queried. The commands to
33249 specify a file are:
33252 @cindex set tdesc filename
33253 @item set tdesc filename @var{path}
33254 Read the target description from @var{path}.
33256 @cindex unset tdesc filename
33257 @item unset tdesc filename
33258 Do not read the XML target description from a file. @value{GDBN}
33259 will use the description supplied by the current target.
33261 @cindex show tdesc filename
33262 @item show tdesc filename
33263 Show the filename to read for a target description, if any.
33267 @node Target Description Format
33268 @section Target Description Format
33269 @cindex target descriptions, XML format
33271 A target description annex is an @uref{http://www.w3.org/XML/, XML}
33272 document which complies with the Document Type Definition provided in
33273 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
33274 means you can use generally available tools like @command{xmllint} to
33275 check that your feature descriptions are well-formed and valid.
33276 However, to help people unfamiliar with XML write descriptions for
33277 their targets, we also describe the grammar here.
33279 Target descriptions can identify the architecture of the remote target
33280 and (for some architectures) provide information about custom register
33281 sets. They can also identify the OS ABI of the remote target.
33282 @value{GDBN} can use this information to autoconfigure for your
33283 target, or to warn you if you connect to an unsupported target.
33285 Here is a simple target description:
33288 <target version="1.0">
33289 <architecture>i386:x86-64</architecture>
33294 This minimal description only says that the target uses
33295 the x86-64 architecture.
33297 A target description has the following overall form, with [ ] marking
33298 optional elements and @dots{} marking repeatable elements. The elements
33299 are explained further below.
33302 <?xml version="1.0"?>
33303 <!DOCTYPE target SYSTEM "gdb-target.dtd">
33304 <target version="1.0">
33305 @r{[}@var{architecture}@r{]}
33306 @r{[}@var{osabi}@r{]}
33307 @r{[}@var{compatible}@r{]}
33308 @r{[}@var{feature}@dots{}@r{]}
33313 The description is generally insensitive to whitespace and line
33314 breaks, under the usual common-sense rules. The XML version
33315 declaration and document type declaration can generally be omitted
33316 (@value{GDBN} does not require them), but specifying them may be
33317 useful for XML validation tools. The @samp{version} attribute for
33318 @samp{<target>} may also be omitted, but we recommend
33319 including it; if future versions of @value{GDBN} use an incompatible
33320 revision of @file{gdb-target.dtd}, they will detect and report
33321 the version mismatch.
33323 @subsection Inclusion
33324 @cindex target descriptions, inclusion
33327 @cindex <xi:include>
33330 It can sometimes be valuable to split a target description up into
33331 several different annexes, either for organizational purposes, or to
33332 share files between different possible target descriptions. You can
33333 divide a description into multiple files by replacing any element of
33334 the target description with an inclusion directive of the form:
33337 <xi:include href="@var{document}"/>
33341 When @value{GDBN} encounters an element of this form, it will retrieve
33342 the named XML @var{document}, and replace the inclusion directive with
33343 the contents of that document. If the current description was read
33344 using @samp{qXfer}, then so will be the included document;
33345 @var{document} will be interpreted as the name of an annex. If the
33346 current description was read from a file, @value{GDBN} will look for
33347 @var{document} as a file in the same directory where it found the
33348 original description.
33350 @subsection Architecture
33351 @cindex <architecture>
33353 An @samp{<architecture>} element has this form:
33356 <architecture>@var{arch}</architecture>
33359 @var{arch} is one of the architectures from the set accepted by
33360 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33363 @cindex @code{<osabi>}
33365 This optional field was introduced in @value{GDBN} version 7.0.
33366 Previous versions of @value{GDBN} ignore it.
33368 An @samp{<osabi>} element has this form:
33371 <osabi>@var{abi-name}</osabi>
33374 @var{abi-name} is an OS ABI name from the same selection accepted by
33375 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
33377 @subsection Compatible Architecture
33378 @cindex @code{<compatible>}
33380 This optional field was introduced in @value{GDBN} version 7.0.
33381 Previous versions of @value{GDBN} ignore it.
33383 A @samp{<compatible>} element has this form:
33386 <compatible>@var{arch}</compatible>
33389 @var{arch} is one of the architectures from the set accepted by
33390 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33392 A @samp{<compatible>} element is used to specify that the target
33393 is able to run binaries in some other than the main target architecture
33394 given by the @samp{<architecture>} element. For example, on the
33395 Cell Broadband Engine, the main architecture is @code{powerpc:common}
33396 or @code{powerpc:common64}, but the system is able to run binaries
33397 in the @code{spu} architecture as well. The way to describe this
33398 capability with @samp{<compatible>} is as follows:
33401 <architecture>powerpc:common</architecture>
33402 <compatible>spu</compatible>
33405 @subsection Features
33408 Each @samp{<feature>} describes some logical portion of the target
33409 system. Features are currently used to describe available CPU
33410 registers and the types of their contents. A @samp{<feature>} element
33414 <feature name="@var{name}">
33415 @r{[}@var{type}@dots{}@r{]}
33421 Each feature's name should be unique within the description. The name
33422 of a feature does not matter unless @value{GDBN} has some special
33423 knowledge of the contents of that feature; if it does, the feature
33424 should have its standard name. @xref{Standard Target Features}.
33428 Any register's value is a collection of bits which @value{GDBN} must
33429 interpret. The default interpretation is a two's complement integer,
33430 but other types can be requested by name in the register description.
33431 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
33432 Target Types}), and the description can define additional composite types.
33434 Each type element must have an @samp{id} attribute, which gives
33435 a unique (within the containing @samp{<feature>}) name to the type.
33436 Types must be defined before they are used.
33439 Some targets offer vector registers, which can be treated as arrays
33440 of scalar elements. These types are written as @samp{<vector>} elements,
33441 specifying the array element type, @var{type}, and the number of elements,
33445 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
33449 If a register's value is usefully viewed in multiple ways, define it
33450 with a union type containing the useful representations. The
33451 @samp{<union>} element contains one or more @samp{<field>} elements,
33452 each of which has a @var{name} and a @var{type}:
33455 <union id="@var{id}">
33456 <field name="@var{name}" type="@var{type}"/>
33462 If a register's value is composed from several separate values, define
33463 it with a structure type. There are two forms of the @samp{<struct>}
33464 element; a @samp{<struct>} element must either contain only bitfields
33465 or contain no bitfields. If the structure contains only bitfields,
33466 its total size in bytes must be specified, each bitfield must have an
33467 explicit start and end, and bitfields are automatically assigned an
33468 integer type. The field's @var{start} should be less than or
33469 equal to its @var{end}, and zero represents the least significant bit.
33472 <struct id="@var{id}" size="@var{size}">
33473 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33478 If the structure contains no bitfields, then each field has an
33479 explicit type, and no implicit padding is added.
33482 <struct id="@var{id}">
33483 <field name="@var{name}" type="@var{type}"/>
33489 If a register's value is a series of single-bit flags, define it with
33490 a flags type. The @samp{<flags>} element has an explicit @var{size}
33491 and contains one or more @samp{<field>} elements. Each field has a
33492 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
33496 <flags id="@var{id}" size="@var{size}">
33497 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33502 @subsection Registers
33505 Each register is represented as an element with this form:
33508 <reg name="@var{name}"
33509 bitsize="@var{size}"
33510 @r{[}regnum="@var{num}"@r{]}
33511 @r{[}save-restore="@var{save-restore}"@r{]}
33512 @r{[}type="@var{type}"@r{]}
33513 @r{[}group="@var{group}"@r{]}/>
33517 The components are as follows:
33522 The register's name; it must be unique within the target description.
33525 The register's size, in bits.
33528 The register's number. If omitted, a register's number is one greater
33529 than that of the previous register (either in the current feature or in
33530 a preceeding feature); the first register in the target description
33531 defaults to zero. This register number is used to read or write
33532 the register; e.g.@: it is used in the remote @code{p} and @code{P}
33533 packets, and registers appear in the @code{g} and @code{G} packets
33534 in order of increasing register number.
33537 Whether the register should be preserved across inferior function
33538 calls; this must be either @code{yes} or @code{no}. The default is
33539 @code{yes}, which is appropriate for most registers except for
33540 some system control registers; this is not related to the target's
33544 The type of the register. @var{type} may be a predefined type, a type
33545 defined in the current feature, or one of the special types @code{int}
33546 and @code{float}. @code{int} is an integer type of the correct size
33547 for @var{bitsize}, and @code{float} is a floating point type (in the
33548 architecture's normal floating point format) of the correct size for
33549 @var{bitsize}. The default is @code{int}.
33552 The register group to which this register belongs. @var{group} must
33553 be either @code{general}, @code{float}, or @code{vector}. If no
33554 @var{group} is specified, @value{GDBN} will not display the register
33555 in @code{info registers}.
33559 @node Predefined Target Types
33560 @section Predefined Target Types
33561 @cindex target descriptions, predefined types
33563 Type definitions in the self-description can build up composite types
33564 from basic building blocks, but can not define fundamental types. Instead,
33565 standard identifiers are provided by @value{GDBN} for the fundamental
33566 types. The currently supported types are:
33575 Signed integer types holding the specified number of bits.
33582 Unsigned integer types holding the specified number of bits.
33586 Pointers to unspecified code and data. The program counter and
33587 any dedicated return address register may be marked as code
33588 pointers; printing a code pointer converts it into a symbolic
33589 address. The stack pointer and any dedicated address registers
33590 may be marked as data pointers.
33593 Single precision IEEE floating point.
33596 Double precision IEEE floating point.
33599 The 12-byte extended precision format used by ARM FPA registers.
33602 The 10-byte extended precision format used by x87 registers.
33605 32bit @sc{eflags} register used by x86.
33608 32bit @sc{mxcsr} register used by x86.
33612 @node Standard Target Features
33613 @section Standard Target Features
33614 @cindex target descriptions, standard features
33616 A target description must contain either no registers or all the
33617 target's registers. If the description contains no registers, then
33618 @value{GDBN} will assume a default register layout, selected based on
33619 the architecture. If the description contains any registers, the
33620 default layout will not be used; the standard registers must be
33621 described in the target description, in such a way that @value{GDBN}
33622 can recognize them.
33624 This is accomplished by giving specific names to feature elements
33625 which contain standard registers. @value{GDBN} will look for features
33626 with those names and verify that they contain the expected registers;
33627 if any known feature is missing required registers, or if any required
33628 feature is missing, @value{GDBN} will reject the target
33629 description. You can add additional registers to any of the
33630 standard features --- @value{GDBN} will display them just as if
33631 they were added to an unrecognized feature.
33633 This section lists the known features and their expected contents.
33634 Sample XML documents for these features are included in the
33635 @value{GDBN} source tree, in the directory @file{gdb/features}.
33637 Names recognized by @value{GDBN} should include the name of the
33638 company or organization which selected the name, and the overall
33639 architecture to which the feature applies; so e.g.@: the feature
33640 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
33642 The names of registers are not case sensitive for the purpose
33643 of recognizing standard features, but @value{GDBN} will only display
33644 registers using the capitalization used in the description.
33651 * PowerPC Features::
33656 @subsection ARM Features
33657 @cindex target descriptions, ARM features
33659 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
33660 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
33661 @samp{lr}, @samp{pc}, and @samp{cpsr}.
33663 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
33664 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
33666 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
33667 it should contain at least registers @samp{wR0} through @samp{wR15} and
33668 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
33669 @samp{wCSSF}, and @samp{wCASF} registers are optional.
33671 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
33672 should contain at least registers @samp{d0} through @samp{d15}. If
33673 they are present, @samp{d16} through @samp{d31} should also be included.
33674 @value{GDBN} will synthesize the single-precision registers from
33675 halves of the double-precision registers.
33677 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
33678 need to contain registers; it instructs @value{GDBN} to display the
33679 VFP double-precision registers as vectors and to synthesize the
33680 quad-precision registers from pairs of double-precision registers.
33681 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
33682 be present and include 32 double-precision registers.
33684 @node i386 Features
33685 @subsection i386 Features
33686 @cindex target descriptions, i386 features
33688 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
33689 targets. It should describe the following registers:
33693 @samp{eax} through @samp{edi} plus @samp{eip} for i386
33695 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
33697 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
33698 @samp{fs}, @samp{gs}
33700 @samp{st0} through @samp{st7}
33702 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
33703 @samp{foseg}, @samp{fooff} and @samp{fop}
33706 The register sets may be different, depending on the target.
33708 The @samp{org.gnu.gdb.i386.sse} feature is required. It should
33709 describe registers:
33713 @samp{xmm0} through @samp{xmm7} for i386
33715 @samp{xmm0} through @samp{xmm15} for amd64
33720 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
33721 describe a single register, @samp{orig_eax}.
33723 @node MIPS Features
33724 @subsection MIPS Features
33725 @cindex target descriptions, MIPS features
33727 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
33728 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
33729 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
33732 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
33733 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
33734 registers. They may be 32-bit or 64-bit depending on the target.
33736 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
33737 it may be optional in a future version of @value{GDBN}. It should
33738 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
33739 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
33741 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
33742 contain a single register, @samp{restart}, which is used by the
33743 Linux kernel to control restartable syscalls.
33745 @node M68K Features
33746 @subsection M68K Features
33747 @cindex target descriptions, M68K features
33750 @item @samp{org.gnu.gdb.m68k.core}
33751 @itemx @samp{org.gnu.gdb.coldfire.core}
33752 @itemx @samp{org.gnu.gdb.fido.core}
33753 One of those features must be always present.
33754 The feature that is present determines which flavor of m68k is
33755 used. The feature that is present should contain registers
33756 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
33757 @samp{sp}, @samp{ps} and @samp{pc}.
33759 @item @samp{org.gnu.gdb.coldfire.fp}
33760 This feature is optional. If present, it should contain registers
33761 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
33765 @node PowerPC Features
33766 @subsection PowerPC Features
33767 @cindex target descriptions, PowerPC features
33769 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
33770 targets. It should contain registers @samp{r0} through @samp{r31},
33771 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
33772 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
33774 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
33775 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
33777 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
33778 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
33781 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
33782 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
33783 will combine these registers with the floating point registers
33784 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
33785 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
33786 through @samp{vs63}, the set of vector registers for POWER7.
33788 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
33789 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
33790 @samp{spefscr}. SPE targets should provide 32-bit registers in
33791 @samp{org.gnu.gdb.power.core} and provide the upper halves in
33792 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
33793 these to present registers @samp{ev0} through @samp{ev31} to the
33796 @node Operating System Information
33797 @appendix Operating System Information
33798 @cindex operating system information
33804 Users of @value{GDBN} often wish to obtain information about the state of
33805 the operating system running on the target---for example the list of
33806 processes, or the list of open files. This section describes the
33807 mechanism that makes it possible. This mechanism is similar to the
33808 target features mechanism (@pxref{Target Descriptions}), but focuses
33809 on a different aspect of target.
33811 Operating system information is retrived from the target via the
33812 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
33813 read}). The object name in the request should be @samp{osdata}, and
33814 the @var{annex} identifies the data to be fetched.
33817 @appendixsection Process list
33818 @cindex operating system information, process list
33820 When requesting the process list, the @var{annex} field in the
33821 @samp{qXfer} request should be @samp{processes}. The returned data is
33822 an XML document. The formal syntax of this document is defined in
33823 @file{gdb/features/osdata.dtd}.
33825 An example document is:
33828 <?xml version="1.0"?>
33829 <!DOCTYPE target SYSTEM "osdata.dtd">
33830 <osdata type="processes">
33832 <column name="pid">1</column>
33833 <column name="user">root</column>
33834 <column name="command">/sbin/init</column>
33835 <column name="cores">1,2,3</column>
33840 Each item should include a column whose name is @samp{pid}. The value
33841 of that column should identify the process on the target. The
33842 @samp{user} and @samp{command} columns are optional, and will be
33843 displayed by @value{GDBN}. The @samp{cores} column, if present,
33844 should contain a comma-separated list of cores that this process
33845 is running on. Target may provide additional columns,
33846 which @value{GDBN} currently ignores.
33860 % I think something like @colophon should be in texinfo. In the
33862 \long\def\colophon{\hbox to0pt{}\vfill
33863 \centerline{The body of this manual is set in}
33864 \centerline{\fontname\tenrm,}
33865 \centerline{with headings in {\bf\fontname\tenbf}}
33866 \centerline{and examples in {\tt\fontname\tentt}.}
33867 \centerline{{\it\fontname\tenit\/},}
33868 \centerline{{\bf\fontname\tenbf}, and}
33869 \centerline{{\sl\fontname\tensl\/}}
33870 \centerline{are used for emphasis.}\vfill}
33872 % Blame: doc@cygnus.com, 1991.