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 1.3 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++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination;
1035 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1036 effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}, and remove it from the inferior list.
2486 @kindex kill inferior @var{infno}
2487 @item kill inferior @var{infno}
2488 Kill the inferior identified by @value{GDBN} inferior number
2489 @var{infno}, and remove it from the inferior list.
2492 After the successful completion of a command such as @code{detach},
2493 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2494 a normal process exit, the inferior is still valid and listed with
2495 @code{info inferiors}, ready to be restarted.
2498 To be notified when inferiors are started or exit under @value{GDBN}'s
2499 control use @w{@code{set print inferior-events}}:
2502 @kindex set print inferior-events
2503 @cindex print messages on inferior start and exit
2504 @item set print inferior-events
2505 @itemx set print inferior-events on
2506 @itemx set print inferior-events off
2507 The @code{set print inferior-events} command allows you to enable or
2508 disable printing of messages when @value{GDBN} notices that new
2509 inferiors have started or that inferiors have exited or have been
2510 detached. By default, these messages will not be printed.
2512 @kindex show print inferior-events
2513 @item show print inferior-events
2514 Show whether messages will be printed when @value{GDBN} detects that
2515 inferiors have started, exited or have been detached.
2518 Many commands will work the same with multiple programs as with a
2519 single program: e.g., @code{print myglobal} will simply display the
2520 value of @code{myglobal} in the current inferior.
2523 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2524 get more info about the relationship of inferiors, programs, address
2525 spaces in a debug session. You can do that with the @w{@code{maint
2526 info program-spaces}} command.
2529 @kindex maint info program-spaces
2530 @item maint info program-spaces
2531 Print a list of all program spaces currently being managed by
2534 @value{GDBN} displays for each program space (in this order):
2538 the program space number assigned by @value{GDBN}
2541 the name of the executable loaded into the program space, with e.g.,
2542 the @code{file} command.
2547 An asterisk @samp{*} preceding the @value{GDBN} program space number
2548 indicates the current program space.
2550 In addition, below each program space line, @value{GDBN} prints extra
2551 information that isn't suitable to display in tabular form. For
2552 example, the list of inferiors bound to the program space.
2555 (@value{GDBP}) maint info program-spaces
2558 Bound inferiors: ID 1 (process 21561)
2562 Here we can see that no inferior is running the program @code{hello},
2563 while @code{process 21561} is running the program @code{goodbye}. On
2564 some targets, it is possible that multiple inferiors are bound to the
2565 same program space. The most common example is that of debugging both
2566 the parent and child processes of a @code{vfork} call. For example,
2569 (@value{GDBP}) maint info program-spaces
2572 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2575 Here, both inferior 2 and inferior 1 are running in the same program
2576 space as a result of inferior 1 having executed a @code{vfork} call.
2580 @section Debugging Programs with Multiple Threads
2582 @cindex threads of execution
2583 @cindex multiple threads
2584 @cindex switching threads
2585 In some operating systems, such as HP-UX and Solaris, a single program
2586 may have more than one @dfn{thread} of execution. The precise semantics
2587 of threads differ from one operating system to another, but in general
2588 the threads of a single program are akin to multiple processes---except
2589 that they share one address space (that is, they can all examine and
2590 modify the same variables). On the other hand, each thread has its own
2591 registers and execution stack, and perhaps private memory.
2593 @value{GDBN} provides these facilities for debugging multi-thread
2597 @item automatic notification of new threads
2598 @item @samp{thread @var{threadno}}, a command to switch among threads
2599 @item @samp{info threads}, a command to inquire about existing threads
2600 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2601 a command to apply a command to a list of threads
2602 @item thread-specific breakpoints
2603 @item @samp{set print thread-events}, which controls printing of
2604 messages on thread start and exit.
2605 @item @samp{set libthread-db-search-path @var{path}}, which lets
2606 the user specify which @code{libthread_db} to use if the default choice
2607 isn't compatible with the program.
2611 @emph{Warning:} These facilities are not yet available on every
2612 @value{GDBN} configuration where the operating system supports threads.
2613 If your @value{GDBN} does not support threads, these commands have no
2614 effect. For example, a system without thread support shows no output
2615 from @samp{info threads}, and always rejects the @code{thread} command,
2619 (@value{GDBP}) info threads
2620 (@value{GDBP}) thread 1
2621 Thread ID 1 not known. Use the "info threads" command to
2622 see the IDs of currently known threads.
2624 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2625 @c doesn't support threads"?
2628 @cindex focus of debugging
2629 @cindex current thread
2630 The @value{GDBN} thread debugging facility allows you to observe all
2631 threads while your program runs---but whenever @value{GDBN} takes
2632 control, one thread in particular is always the focus of debugging.
2633 This thread is called the @dfn{current thread}. Debugging commands show
2634 program information from the perspective of the current thread.
2636 @cindex @code{New} @var{systag} message
2637 @cindex thread identifier (system)
2638 @c FIXME-implementors!! It would be more helpful if the [New...] message
2639 @c included GDB's numeric thread handle, so you could just go to that
2640 @c thread without first checking `info threads'.
2641 Whenever @value{GDBN} detects a new thread in your program, it displays
2642 the target system's identification for the thread with a message in the
2643 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2644 whose form varies depending on the particular system. For example, on
2645 @sc{gnu}/Linux, you might see
2648 [New Thread 46912507313328 (LWP 25582)]
2652 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2653 the @var{systag} is simply something like @samp{process 368}, with no
2656 @c FIXME!! (1) Does the [New...] message appear even for the very first
2657 @c thread of a program, or does it only appear for the
2658 @c second---i.e.@: when it becomes obvious we have a multithread
2660 @c (2) *Is* there necessarily a first thread always? Or do some
2661 @c multithread systems permit starting a program with multiple
2662 @c threads ab initio?
2664 @cindex thread number
2665 @cindex thread identifier (GDB)
2666 For debugging purposes, @value{GDBN} associates its own thread
2667 number---always a single integer---with each thread in your program.
2670 @kindex info threads
2672 Display a summary of all threads currently in your
2673 program. @value{GDBN} displays for each thread (in this order):
2677 the thread number assigned by @value{GDBN}
2680 the target system's thread identifier (@var{systag})
2683 the current stack frame summary for that thread
2687 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2688 indicates the current thread.
2692 @c end table here to get a little more width for example
2695 (@value{GDBP}) info threads
2696 3 process 35 thread 27 0x34e5 in sigpause ()
2697 2 process 35 thread 23 0x34e5 in sigpause ()
2698 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2704 @cindex debugging multithreaded programs (on HP-UX)
2705 @cindex thread identifier (GDB), on HP-UX
2706 For debugging purposes, @value{GDBN} associates its own thread
2707 number---a small integer assigned in thread-creation order---with each
2708 thread in your program.
2710 @cindex @code{New} @var{systag} message, on HP-UX
2711 @cindex thread identifier (system), on HP-UX
2712 @c FIXME-implementors!! It would be more helpful if the [New...] message
2713 @c included GDB's numeric thread handle, so you could just go to that
2714 @c thread without first checking `info threads'.
2715 Whenever @value{GDBN} detects a new thread in your program, it displays
2716 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2717 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2718 whose form varies depending on the particular system. For example, on
2722 [New thread 2 (system thread 26594)]
2726 when @value{GDBN} notices a new thread.
2729 @kindex info threads (HP-UX)
2731 Display a summary of all threads currently in your
2732 program. @value{GDBN} displays for each thread (in this order):
2735 @item the thread number assigned by @value{GDBN}
2737 @item the target system's thread identifier (@var{systag})
2739 @item the current stack frame summary for that thread
2743 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2744 indicates the current thread.
2748 @c end table here to get a little more width for example
2751 (@value{GDBP}) info threads
2752 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2754 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2755 from /usr/lib/libc.2
2756 1 system thread 27905 0x7b003498 in _brk () \@*
2757 from /usr/lib/libc.2
2760 On Solaris, you can display more information about user threads with a
2761 Solaris-specific command:
2764 @item maint info sol-threads
2765 @kindex maint info sol-threads
2766 @cindex thread info (Solaris)
2767 Display info on Solaris user threads.
2771 @kindex thread @var{threadno}
2772 @item thread @var{threadno}
2773 Make thread number @var{threadno} the current thread. The command
2774 argument @var{threadno} is the internal @value{GDBN} thread number, as
2775 shown in the first field of the @samp{info threads} display.
2776 @value{GDBN} responds by displaying the system identifier of the thread
2777 you selected, and its current stack frame summary:
2780 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2781 (@value{GDBP}) thread 2
2782 [Switching to process 35 thread 23]
2783 0x34e5 in sigpause ()
2787 As with the @samp{[New @dots{}]} message, the form of the text after
2788 @samp{Switching to} depends on your system's conventions for identifying
2791 @vindex $_thread@r{, convenience variable}
2792 The debugger convenience variable @samp{$_thread} contains the number
2793 of the current thread. You may find this useful in writing breakpoint
2794 conditional expressions, command scripts, and so forth. See
2795 @xref{Convenience Vars,, Convenience Variables}, for general
2796 information on convenience variables.
2798 @kindex thread apply
2799 @cindex apply command to several threads
2800 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2801 The @code{thread apply} command allows you to apply the named
2802 @var{command} to one or more threads. Specify the numbers of the
2803 threads that you want affected with the command argument
2804 @var{threadno}. It can be a single thread number, one of the numbers
2805 shown in the first field of the @samp{info threads} display; or it
2806 could be a range of thread numbers, as in @code{2-4}. To apply a
2807 command to all threads, type @kbd{thread apply all @var{command}}.
2809 @kindex set print thread-events
2810 @cindex print messages on thread start and exit
2811 @item set print thread-events
2812 @itemx set print thread-events on
2813 @itemx set print thread-events off
2814 The @code{set print thread-events} command allows you to enable or
2815 disable printing of messages when @value{GDBN} notices that new threads have
2816 started or that threads have exited. By default, these messages will
2817 be printed if detection of these events is supported by the target.
2818 Note that these messages cannot be disabled on all targets.
2820 @kindex show print thread-events
2821 @item show print thread-events
2822 Show whether messages will be printed when @value{GDBN} detects that threads
2823 have started and exited.
2826 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2827 more information about how @value{GDBN} behaves when you stop and start
2828 programs with multiple threads.
2830 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2831 watchpoints in programs with multiple threads.
2834 @kindex set libthread-db-search-path
2835 @cindex search path for @code{libthread_db}
2836 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2837 If this variable is set, @var{path} is a colon-separated list of
2838 directories @value{GDBN} will use to search for @code{libthread_db}.
2839 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2842 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2843 @code{libthread_db} library to obtain information about threads in the
2844 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2845 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2846 with default system shared library directories, and finally the directory
2847 from which @code{libpthread} was loaded in the inferior process.
2849 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2850 @value{GDBN} attempts to initialize it with the current inferior process.
2851 If this initialization fails (which could happen because of a version
2852 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2853 will unload @code{libthread_db}, and continue with the next directory.
2854 If none of @code{libthread_db} libraries initialize successfully,
2855 @value{GDBN} will issue a warning and thread debugging will be disabled.
2857 Setting @code{libthread-db-search-path} is currently implemented
2858 only on some platforms.
2860 @kindex show libthread-db-search-path
2861 @item show libthread-db-search-path
2862 Display current libthread_db search path.
2866 @section Debugging Forks
2868 @cindex fork, debugging programs which call
2869 @cindex multiple processes
2870 @cindex processes, multiple
2871 On most systems, @value{GDBN} has no special support for debugging
2872 programs which create additional processes using the @code{fork}
2873 function. When a program forks, @value{GDBN} will continue to debug the
2874 parent process and the child process will run unimpeded. If you have
2875 set a breakpoint in any code which the child then executes, the child
2876 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2877 will cause it to terminate.
2879 However, if you want to debug the child process there is a workaround
2880 which isn't too painful. Put a call to @code{sleep} in the code which
2881 the child process executes after the fork. It may be useful to sleep
2882 only if a certain environment variable is set, or a certain file exists,
2883 so that the delay need not occur when you don't want to run @value{GDBN}
2884 on the child. While the child is sleeping, use the @code{ps} program to
2885 get its process ID. Then tell @value{GDBN} (a new invocation of
2886 @value{GDBN} if you are also debugging the parent process) to attach to
2887 the child process (@pxref{Attach}). From that point on you can debug
2888 the child process just like any other process which you attached to.
2890 On some systems, @value{GDBN} provides support for debugging programs that
2891 create additional processes using the @code{fork} or @code{vfork} functions.
2892 Currently, the only platforms with this feature are HP-UX (11.x and later
2893 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2895 By default, when a program forks, @value{GDBN} will continue to debug
2896 the parent process and the child process will run unimpeded.
2898 If you want to follow the child process instead of the parent process,
2899 use the command @w{@code{set follow-fork-mode}}.
2902 @kindex set follow-fork-mode
2903 @item set follow-fork-mode @var{mode}
2904 Set the debugger response to a program call of @code{fork} or
2905 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2906 process. The @var{mode} argument can be:
2910 The original process is debugged after a fork. The child process runs
2911 unimpeded. This is the default.
2914 The new process is debugged after a fork. The parent process runs
2919 @kindex show follow-fork-mode
2920 @item show follow-fork-mode
2921 Display the current debugger response to a @code{fork} or @code{vfork} call.
2924 @cindex debugging multiple processes
2925 On Linux, if you want to debug both the parent and child processes, use the
2926 command @w{@code{set detach-on-fork}}.
2929 @kindex set detach-on-fork
2930 @item set detach-on-fork @var{mode}
2931 Tells gdb whether to detach one of the processes after a fork, or
2932 retain debugger control over them both.
2936 The child process (or parent process, depending on the value of
2937 @code{follow-fork-mode}) will be detached and allowed to run
2938 independently. This is the default.
2941 Both processes will be held under the control of @value{GDBN}.
2942 One process (child or parent, depending on the value of
2943 @code{follow-fork-mode}) is debugged as usual, while the other
2948 @kindex show detach-on-fork
2949 @item show detach-on-fork
2950 Show whether detach-on-fork mode is on/off.
2953 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2954 will retain control of all forked processes (including nested forks).
2955 You can list the forked processes under the control of @value{GDBN} by
2956 using the @w{@code{info inferiors}} command, and switch from one fork
2957 to another by using the @code{inferior} command (@pxref{Inferiors and
2958 Programs, ,Debugging Multiple Inferiors and Programs}).
2960 To quit debugging one of the forked processes, you can either detach
2961 from it by using the @w{@code{detach inferior}} command (allowing it
2962 to run independently), or kill it using the @w{@code{kill inferior}}
2963 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2966 If you ask to debug a child process and a @code{vfork} is followed by an
2967 @code{exec}, @value{GDBN} executes the new target up to the first
2968 breakpoint in the new target. If you have a breakpoint set on
2969 @code{main} in your original program, the breakpoint will also be set on
2970 the child process's @code{main}.
2972 On some systems, when a child process is spawned by @code{vfork}, you
2973 cannot debug the child or parent until an @code{exec} call completes.
2975 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2976 call executes, the new target restarts. To restart the parent
2977 process, use the @code{file} command with the parent executable name
2978 as its argument. By default, after an @code{exec} call executes,
2979 @value{GDBN} discards the symbols of the previous executable image.
2980 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2984 @kindex set follow-exec-mode
2985 @item set follow-exec-mode @var{mode}
2987 Set debugger response to a program call of @code{exec}. An
2988 @code{exec} call replaces the program image of a process.
2990 @code{follow-exec-mode} can be:
2994 @value{GDBN} creates a new inferior and rebinds the process to this
2995 new inferior. The program the process was running before the
2996 @code{exec} call can be restarted afterwards by restarting the
3002 (@value{GDBP}) info inferiors
3004 Id Description Executable
3007 process 12020 is executing new program: prog2
3008 Program exited normally.
3009 (@value{GDBP}) info inferiors
3010 Id Description Executable
3016 @value{GDBN} keeps the process bound to the same inferior. The new
3017 executable image replaces the previous executable loaded in the
3018 inferior. Restarting the inferior after the @code{exec} call, with
3019 e.g., the @code{run} command, restarts the executable the process was
3020 running after the @code{exec} call. This is the default mode.
3025 (@value{GDBP}) info inferiors
3026 Id Description Executable
3029 process 12020 is executing new program: prog2
3030 Program exited normally.
3031 (@value{GDBP}) info inferiors
3032 Id Description Executable
3039 You can use the @code{catch} command to make @value{GDBN} stop whenever
3040 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3041 Catchpoints, ,Setting Catchpoints}.
3043 @node Checkpoint/Restart
3044 @section Setting a @emph{Bookmark} to Return to Later
3049 @cindex snapshot of a process
3050 @cindex rewind program state
3052 On certain operating systems@footnote{Currently, only
3053 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3054 program's state, called a @dfn{checkpoint}, and come back to it
3057 Returning to a checkpoint effectively undoes everything that has
3058 happened in the program since the @code{checkpoint} was saved. This
3059 includes changes in memory, registers, and even (within some limits)
3060 system state. Effectively, it is like going back in time to the
3061 moment when the checkpoint was saved.
3063 Thus, if you're stepping thru a program and you think you're
3064 getting close to the point where things go wrong, you can save
3065 a checkpoint. Then, if you accidentally go too far and miss
3066 the critical statement, instead of having to restart your program
3067 from the beginning, you can just go back to the checkpoint and
3068 start again from there.
3070 This can be especially useful if it takes a lot of time or
3071 steps to reach the point where you think the bug occurs.
3073 To use the @code{checkpoint}/@code{restart} method of debugging:
3078 Save a snapshot of the debugged program's current execution state.
3079 The @code{checkpoint} command takes no arguments, but each checkpoint
3080 is assigned a small integer id, similar to a breakpoint id.
3082 @kindex info checkpoints
3083 @item info checkpoints
3084 List the checkpoints that have been saved in the current debugging
3085 session. For each checkpoint, the following information will be
3092 @item Source line, or label
3095 @kindex restart @var{checkpoint-id}
3096 @item restart @var{checkpoint-id}
3097 Restore the program state that was saved as checkpoint number
3098 @var{checkpoint-id}. All program variables, registers, stack frames
3099 etc.@: will be returned to the values that they had when the checkpoint
3100 was saved. In essence, gdb will ``wind back the clock'' to the point
3101 in time when the checkpoint was saved.
3103 Note that breakpoints, @value{GDBN} variables, command history etc.
3104 are not affected by restoring a checkpoint. In general, a checkpoint
3105 only restores things that reside in the program being debugged, not in
3108 @kindex delete checkpoint @var{checkpoint-id}
3109 @item delete checkpoint @var{checkpoint-id}
3110 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3114 Returning to a previously saved checkpoint will restore the user state
3115 of the program being debugged, plus a significant subset of the system
3116 (OS) state, including file pointers. It won't ``un-write'' data from
3117 a file, but it will rewind the file pointer to the previous location,
3118 so that the previously written data can be overwritten. For files
3119 opened in read mode, the pointer will also be restored so that the
3120 previously read data can be read again.
3122 Of course, characters that have been sent to a printer (or other
3123 external device) cannot be ``snatched back'', and characters received
3124 from eg.@: a serial device can be removed from internal program buffers,
3125 but they cannot be ``pushed back'' into the serial pipeline, ready to
3126 be received again. Similarly, the actual contents of files that have
3127 been changed cannot be restored (at this time).
3129 However, within those constraints, you actually can ``rewind'' your
3130 program to a previously saved point in time, and begin debugging it
3131 again --- and you can change the course of events so as to debug a
3132 different execution path this time.
3134 @cindex checkpoints and process id
3135 Finally, there is one bit of internal program state that will be
3136 different when you return to a checkpoint --- the program's process
3137 id. Each checkpoint will have a unique process id (or @var{pid}),
3138 and each will be different from the program's original @var{pid}.
3139 If your program has saved a local copy of its process id, this could
3140 potentially pose a problem.
3142 @subsection A Non-obvious Benefit of Using Checkpoints
3144 On some systems such as @sc{gnu}/Linux, address space randomization
3145 is performed on new processes for security reasons. This makes it
3146 difficult or impossible to set a breakpoint, or watchpoint, on an
3147 absolute address if you have to restart the program, since the
3148 absolute location of a symbol will change from one execution to the
3151 A checkpoint, however, is an @emph{identical} copy of a process.
3152 Therefore if you create a checkpoint at (eg.@:) the start of main,
3153 and simply return to that checkpoint instead of restarting the
3154 process, you can avoid the effects of address randomization and
3155 your symbols will all stay in the same place.
3158 @chapter Stopping and Continuing
3160 The principal purposes of using a debugger are so that you can stop your
3161 program before it terminates; or so that, if your program runs into
3162 trouble, you can investigate and find out why.
3164 Inside @value{GDBN}, your program may stop for any of several reasons,
3165 such as a signal, a breakpoint, or reaching a new line after a
3166 @value{GDBN} command such as @code{step}. You may then examine and
3167 change variables, set new breakpoints or remove old ones, and then
3168 continue execution. Usually, the messages shown by @value{GDBN} provide
3169 ample explanation of the status of your program---but you can also
3170 explicitly request this information at any time.
3173 @kindex info program
3175 Display information about the status of your program: whether it is
3176 running or not, what process it is, and why it stopped.
3180 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3181 * Continuing and Stepping:: Resuming execution
3183 * Thread Stops:: Stopping and starting multi-thread programs
3187 @section Breakpoints, Watchpoints, and Catchpoints
3190 A @dfn{breakpoint} makes your program stop whenever a certain point in
3191 the program is reached. For each breakpoint, you can add conditions to
3192 control in finer detail whether your program stops. You can set
3193 breakpoints with the @code{break} command and its variants (@pxref{Set
3194 Breaks, ,Setting Breakpoints}), to specify the place where your program
3195 should stop by line number, function name or exact address in the
3198 On some systems, you can set breakpoints in shared libraries before
3199 the executable is run. There is a minor limitation on HP-UX systems:
3200 you must wait until the executable is run in order to set breakpoints
3201 in shared library routines that are not called directly by the program
3202 (for example, routines that are arguments in a @code{pthread_create}
3206 @cindex data breakpoints
3207 @cindex memory tracing
3208 @cindex breakpoint on memory address
3209 @cindex breakpoint on variable modification
3210 A @dfn{watchpoint} is a special breakpoint that stops your program
3211 when the value of an expression changes. The expression may be a value
3212 of a variable, or it could involve values of one or more variables
3213 combined by operators, such as @samp{a + b}. This is sometimes called
3214 @dfn{data breakpoints}. You must use a different command to set
3215 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3216 from that, you can manage a watchpoint like any other breakpoint: you
3217 enable, disable, and delete both breakpoints and watchpoints using the
3220 You can arrange to have values from your program displayed automatically
3221 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3225 @cindex breakpoint on events
3226 A @dfn{catchpoint} is another special breakpoint that stops your program
3227 when a certain kind of event occurs, such as the throwing of a C@t{++}
3228 exception or the loading of a library. As with watchpoints, you use a
3229 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3230 Catchpoints}), but aside from that, you can manage a catchpoint like any
3231 other breakpoint. (To stop when your program receives a signal, use the
3232 @code{handle} command; see @ref{Signals, ,Signals}.)
3234 @cindex breakpoint numbers
3235 @cindex numbers for breakpoints
3236 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3237 catchpoint when you create it; these numbers are successive integers
3238 starting with one. In many of the commands for controlling various
3239 features of breakpoints you use the breakpoint number to say which
3240 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3241 @dfn{disabled}; if disabled, it has no effect on your program until you
3244 @cindex breakpoint ranges
3245 @cindex ranges of breakpoints
3246 Some @value{GDBN} commands accept a range of breakpoints on which to
3247 operate. A breakpoint range is either a single breakpoint number, like
3248 @samp{5}, or two such numbers, in increasing order, separated by a
3249 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3250 all breakpoints in that range are operated on.
3253 * Set Breaks:: Setting breakpoints
3254 * Set Watchpoints:: Setting watchpoints
3255 * Set Catchpoints:: Setting catchpoints
3256 * Delete Breaks:: Deleting breakpoints
3257 * Disabling:: Disabling breakpoints
3258 * Conditions:: Break conditions
3259 * Break Commands:: Breakpoint command lists
3260 * Save Breakpoints:: How to save breakpoints in a file
3261 * Error in Breakpoints:: ``Cannot insert breakpoints''
3262 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3266 @subsection Setting Breakpoints
3268 @c FIXME LMB what does GDB do if no code on line of breakpt?
3269 @c consider in particular declaration with/without initialization.
3271 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3274 @kindex b @r{(@code{break})}
3275 @vindex $bpnum@r{, convenience variable}
3276 @cindex latest breakpoint
3277 Breakpoints are set with the @code{break} command (abbreviated
3278 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3279 number of the breakpoint you've set most recently; see @ref{Convenience
3280 Vars,, Convenience Variables}, for a discussion of what you can do with
3281 convenience variables.
3284 @item break @var{location}
3285 Set a breakpoint at the given @var{location}, which can specify a
3286 function name, a line number, or an address of an instruction.
3287 (@xref{Specify Location}, for a list of all the possible ways to
3288 specify a @var{location}.) The breakpoint will stop your program just
3289 before it executes any of the code in the specified @var{location}.
3291 When using source languages that permit overloading of symbols, such as
3292 C@t{++}, a function name may refer to more than one possible place to break.
3293 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3296 It is also possible to insert a breakpoint that will stop the program
3297 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3298 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3301 When called without any arguments, @code{break} sets a breakpoint at
3302 the next instruction to be executed in the selected stack frame
3303 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3304 innermost, this makes your program stop as soon as control
3305 returns to that frame. This is similar to the effect of a
3306 @code{finish} command in the frame inside the selected frame---except
3307 that @code{finish} does not leave an active breakpoint. If you use
3308 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3309 the next time it reaches the current location; this may be useful
3312 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3313 least one instruction has been executed. If it did not do this, you
3314 would be unable to proceed past a breakpoint without first disabling the
3315 breakpoint. This rule applies whether or not the breakpoint already
3316 existed when your program stopped.
3318 @item break @dots{} if @var{cond}
3319 Set a breakpoint with condition @var{cond}; evaluate the expression
3320 @var{cond} each time the breakpoint is reached, and stop only if the
3321 value is nonzero---that is, if @var{cond} evaluates as true.
3322 @samp{@dots{}} stands for one of the possible arguments described
3323 above (or no argument) specifying where to break. @xref{Conditions,
3324 ,Break Conditions}, for more information on breakpoint conditions.
3327 @item tbreak @var{args}
3328 Set a breakpoint enabled only for one stop. @var{args} are the
3329 same as for the @code{break} command, and the breakpoint is set in the same
3330 way, but the breakpoint is automatically deleted after the first time your
3331 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3334 @cindex hardware breakpoints
3335 @item hbreak @var{args}
3336 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3337 @code{break} command and the breakpoint is set in the same way, but the
3338 breakpoint requires hardware support and some target hardware may not
3339 have this support. The main purpose of this is EPROM/ROM code
3340 debugging, so you can set a breakpoint at an instruction without
3341 changing the instruction. This can be used with the new trap-generation
3342 provided by SPARClite DSU and most x86-based targets. These targets
3343 will generate traps when a program accesses some data or instruction
3344 address that is assigned to the debug registers. However the hardware
3345 breakpoint registers can take a limited number of breakpoints. For
3346 example, on the DSU, only two data breakpoints can be set at a time, and
3347 @value{GDBN} will reject this command if more than two are used. Delete
3348 or disable unused hardware breakpoints before setting new ones
3349 (@pxref{Disabling, ,Disabling Breakpoints}).
3350 @xref{Conditions, ,Break Conditions}.
3351 For remote targets, you can restrict the number of hardware
3352 breakpoints @value{GDBN} will use, see @ref{set remote
3353 hardware-breakpoint-limit}.
3356 @item thbreak @var{args}
3357 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3358 are the same as for the @code{hbreak} command and the breakpoint is set in
3359 the same way. However, like the @code{tbreak} command,
3360 the breakpoint is automatically deleted after the
3361 first time your program stops there. Also, like the @code{hbreak}
3362 command, the breakpoint requires hardware support and some target hardware
3363 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3364 See also @ref{Conditions, ,Break Conditions}.
3367 @cindex regular expression
3368 @cindex breakpoints at functions matching a regexp
3369 @cindex set breakpoints in many functions
3370 @item rbreak @var{regex}
3371 Set breakpoints on all functions matching the regular expression
3372 @var{regex}. This command sets an unconditional breakpoint on all
3373 matches, printing a list of all breakpoints it set. Once these
3374 breakpoints are set, they are treated just like the breakpoints set with
3375 the @code{break} command. You can delete them, disable them, or make
3376 them conditional the same way as any other breakpoint.
3378 The syntax of the regular expression is the standard one used with tools
3379 like @file{grep}. Note that this is different from the syntax used by
3380 shells, so for instance @code{foo*} matches all functions that include
3381 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3382 @code{.*} leading and trailing the regular expression you supply, so to
3383 match only functions that begin with @code{foo}, use @code{^foo}.
3385 @cindex non-member C@t{++} functions, set breakpoint in
3386 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3387 breakpoints on overloaded functions that are not members of any special
3390 @cindex set breakpoints on all functions
3391 The @code{rbreak} command can be used to set breakpoints in
3392 @strong{all} the functions in a program, like this:
3395 (@value{GDBP}) rbreak .
3398 @item rbreak @var{file}:@var{regex}
3399 If @code{rbreak} is called with a filename qualification, it limits
3400 the search for functions matching the given regular expression to the
3401 specified @var{file}. This can be used, for example, to set breakpoints on
3402 every function in a given file:
3405 (@value{GDBP}) rbreak file.c:.
3408 The colon separating the filename qualifier from the regex may
3409 optionally be surrounded by spaces.
3411 @kindex info breakpoints
3412 @cindex @code{$_} and @code{info breakpoints}
3413 @item info breakpoints @r{[}@var{n}@r{]}
3414 @itemx info break @r{[}@var{n}@r{]}
3415 Print a table of all breakpoints, watchpoints, and catchpoints set and
3416 not deleted. Optional argument @var{n} means print information only
3417 about the specified breakpoint (or watchpoint or catchpoint). For
3418 each breakpoint, following columns are printed:
3421 @item Breakpoint Numbers
3423 Breakpoint, watchpoint, or catchpoint.
3425 Whether the breakpoint is marked to be disabled or deleted when hit.
3426 @item Enabled or Disabled
3427 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3428 that are not enabled.
3430 Where the breakpoint is in your program, as a memory address. For a
3431 pending breakpoint whose address is not yet known, this field will
3432 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3433 library that has the symbol or line referred by breakpoint is loaded.
3434 See below for details. A breakpoint with several locations will
3435 have @samp{<MULTIPLE>} in this field---see below for details.
3437 Where the breakpoint is in the source for your program, as a file and
3438 line number. For a pending breakpoint, the original string passed to
3439 the breakpoint command will be listed as it cannot be resolved until
3440 the appropriate shared library is loaded in the future.
3444 If a breakpoint is conditional, @code{info break} shows the condition on
3445 the line following the affected breakpoint; breakpoint commands, if any,
3446 are listed after that. A pending breakpoint is allowed to have a condition
3447 specified for it. The condition is not parsed for validity until a shared
3448 library is loaded that allows the pending breakpoint to resolve to a
3452 @code{info break} with a breakpoint
3453 number @var{n} as argument lists only that breakpoint. The
3454 convenience variable @code{$_} and the default examining-address for
3455 the @code{x} command are set to the address of the last breakpoint
3456 listed (@pxref{Memory, ,Examining Memory}).
3459 @code{info break} displays a count of the number of times the breakpoint
3460 has been hit. This is especially useful in conjunction with the
3461 @code{ignore} command. You can ignore a large number of breakpoint
3462 hits, look at the breakpoint info to see how many times the breakpoint
3463 was hit, and then run again, ignoring one less than that number. This
3464 will get you quickly to the last hit of that breakpoint.
3467 @value{GDBN} allows you to set any number of breakpoints at the same place in
3468 your program. There is nothing silly or meaningless about this. When
3469 the breakpoints are conditional, this is even useful
3470 (@pxref{Conditions, ,Break Conditions}).
3472 @cindex multiple locations, breakpoints
3473 @cindex breakpoints, multiple locations
3474 It is possible that a breakpoint corresponds to several locations
3475 in your program. Examples of this situation are:
3479 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3480 instances of the function body, used in different cases.
3483 For a C@t{++} template function, a given line in the function can
3484 correspond to any number of instantiations.
3487 For an inlined function, a given source line can correspond to
3488 several places where that function is inlined.
3491 In all those cases, @value{GDBN} will insert a breakpoint at all
3492 the relevant locations@footnote{
3493 As of this writing, multiple-location breakpoints work only if there's
3494 line number information for all the locations. This means that they
3495 will generally not work in system libraries, unless you have debug
3496 info with line numbers for them.}.
3498 A breakpoint with multiple locations is displayed in the breakpoint
3499 table using several rows---one header row, followed by one row for
3500 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3501 address column. The rows for individual locations contain the actual
3502 addresses for locations, and show the functions to which those
3503 locations belong. The number column for a location is of the form
3504 @var{breakpoint-number}.@var{location-number}.
3509 Num Type Disp Enb Address What
3510 1 breakpoint keep y <MULTIPLE>
3512 breakpoint already hit 1 time
3513 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3514 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3517 Each location can be individually enabled or disabled by passing
3518 @var{breakpoint-number}.@var{location-number} as argument to the
3519 @code{enable} and @code{disable} commands. Note that you cannot
3520 delete the individual locations from the list, you can only delete the
3521 entire list of locations that belong to their parent breakpoint (with
3522 the @kbd{delete @var{num}} command, where @var{num} is the number of
3523 the parent breakpoint, 1 in the above example). Disabling or enabling
3524 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3525 that belong to that breakpoint.
3527 @cindex pending breakpoints
3528 It's quite common to have a breakpoint inside a shared library.
3529 Shared libraries can be loaded and unloaded explicitly,
3530 and possibly repeatedly, as the program is executed. To support
3531 this use case, @value{GDBN} updates breakpoint locations whenever
3532 any shared library is loaded or unloaded. Typically, you would
3533 set a breakpoint in a shared library at the beginning of your
3534 debugging session, when the library is not loaded, and when the
3535 symbols from the library are not available. When you try to set
3536 breakpoint, @value{GDBN} will ask you if you want to set
3537 a so called @dfn{pending breakpoint}---breakpoint whose address
3538 is not yet resolved.
3540 After the program is run, whenever a new shared library is loaded,
3541 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3542 shared library contains the symbol or line referred to by some
3543 pending breakpoint, that breakpoint is resolved and becomes an
3544 ordinary breakpoint. When a library is unloaded, all breakpoints
3545 that refer to its symbols or source lines become pending again.
3547 This logic works for breakpoints with multiple locations, too. For
3548 example, if you have a breakpoint in a C@t{++} template function, and
3549 a newly loaded shared library has an instantiation of that template,
3550 a new location is added to the list of locations for the breakpoint.
3552 Except for having unresolved address, pending breakpoints do not
3553 differ from regular breakpoints. You can set conditions or commands,
3554 enable and disable them and perform other breakpoint operations.
3556 @value{GDBN} provides some additional commands for controlling what
3557 happens when the @samp{break} command cannot resolve breakpoint
3558 address specification to an address:
3560 @kindex set breakpoint pending
3561 @kindex show breakpoint pending
3563 @item set breakpoint pending auto
3564 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3565 location, it queries you whether a pending breakpoint should be created.
3567 @item set breakpoint pending on
3568 This indicates that an unrecognized breakpoint location should automatically
3569 result in a pending breakpoint being created.
3571 @item set breakpoint pending off
3572 This indicates that pending breakpoints are not to be created. Any
3573 unrecognized breakpoint location results in an error. This setting does
3574 not affect any pending breakpoints previously created.
3576 @item show breakpoint pending
3577 Show the current behavior setting for creating pending breakpoints.
3580 The settings above only affect the @code{break} command and its
3581 variants. Once breakpoint is set, it will be automatically updated
3582 as shared libraries are loaded and unloaded.
3584 @cindex automatic hardware breakpoints
3585 For some targets, @value{GDBN} can automatically decide if hardware or
3586 software breakpoints should be used, depending on whether the
3587 breakpoint address is read-only or read-write. This applies to
3588 breakpoints set with the @code{break} command as well as to internal
3589 breakpoints set by commands like @code{next} and @code{finish}. For
3590 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3593 You can control this automatic behaviour with the following commands::
3595 @kindex set breakpoint auto-hw
3596 @kindex show breakpoint auto-hw
3598 @item set breakpoint auto-hw on
3599 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3600 will try to use the target memory map to decide if software or hardware
3601 breakpoint must be used.
3603 @item set breakpoint auto-hw off
3604 This indicates @value{GDBN} should not automatically select breakpoint
3605 type. If the target provides a memory map, @value{GDBN} will warn when
3606 trying to set software breakpoint at a read-only address.
3609 @value{GDBN} normally implements breakpoints by replacing the program code
3610 at the breakpoint address with a special instruction, which, when
3611 executed, given control to the debugger. By default, the program
3612 code is so modified only when the program is resumed. As soon as
3613 the program stops, @value{GDBN} restores the original instructions. This
3614 behaviour guards against leaving breakpoints inserted in the
3615 target should gdb abrubptly disconnect. However, with slow remote
3616 targets, inserting and removing breakpoint can reduce the performance.
3617 This behavior can be controlled with the following commands::
3619 @kindex set breakpoint always-inserted
3620 @kindex show breakpoint always-inserted
3622 @item set breakpoint always-inserted off
3623 All breakpoints, including newly added by the user, are inserted in
3624 the target only when the target is resumed. All breakpoints are
3625 removed from the target when it stops.
3627 @item set breakpoint always-inserted on
3628 Causes all breakpoints to be inserted in the target at all times. If
3629 the user adds a new breakpoint, or changes an existing breakpoint, the
3630 breakpoints in the target are updated immediately. A breakpoint is
3631 removed from the target only when breakpoint itself is removed.
3633 @cindex non-stop mode, and @code{breakpoint always-inserted}
3634 @item set breakpoint always-inserted auto
3635 This is the default mode. If @value{GDBN} is controlling the inferior
3636 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3637 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3638 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3639 @code{breakpoint always-inserted} mode is off.
3642 @cindex negative breakpoint numbers
3643 @cindex internal @value{GDBN} breakpoints
3644 @value{GDBN} itself sometimes sets breakpoints in your program for
3645 special purposes, such as proper handling of @code{longjmp} (in C
3646 programs). These internal breakpoints are assigned negative numbers,
3647 starting with @code{-1}; @samp{info breakpoints} does not display them.
3648 You can see these breakpoints with the @value{GDBN} maintenance command
3649 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3652 @node Set Watchpoints
3653 @subsection Setting Watchpoints
3655 @cindex setting watchpoints
3656 You can use a watchpoint to stop execution whenever the value of an
3657 expression changes, without having to predict a particular place where
3658 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3659 The expression may be as simple as the value of a single variable, or
3660 as complex as many variables combined by operators. Examples include:
3664 A reference to the value of a single variable.
3667 An address cast to an appropriate data type. For example,
3668 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3669 address (assuming an @code{int} occupies 4 bytes).
3672 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3673 expression can use any operators valid in the program's native
3674 language (@pxref{Languages}).
3677 You can set a watchpoint on an expression even if the expression can
3678 not be evaluated yet. For instance, you can set a watchpoint on
3679 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3680 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3681 the expression produces a valid value. If the expression becomes
3682 valid in some other way than changing a variable (e.g.@: if the memory
3683 pointed to by @samp{*global_ptr} becomes readable as the result of a
3684 @code{malloc} call), @value{GDBN} may not stop until the next time
3685 the expression changes.
3687 @cindex software watchpoints
3688 @cindex hardware watchpoints
3689 Depending on your system, watchpoints may be implemented in software or
3690 hardware. @value{GDBN} does software watchpointing by single-stepping your
3691 program and testing the variable's value each time, which is hundreds of
3692 times slower than normal execution. (But this may still be worth it, to
3693 catch errors where you have no clue what part of your program is the
3696 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3697 x86-based targets, @value{GDBN} includes support for hardware
3698 watchpoints, which do not slow down the running of your program.
3702 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint for an expression. @value{GDBN} will break when the
3704 expression @var{expr} is written into by the program and its value
3705 changes. The simplest (and the most popular) use of this command is
3706 to watch the value of a single variable:
3709 (@value{GDBP}) watch foo
3712 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3713 clause, @value{GDBN} breaks only when the thread identified by
3714 @var{threadnum} changes the value of @var{expr}. If any other threads
3715 change the value of @var{expr}, @value{GDBN} will not break. Note
3716 that watchpoints restricted to a single thread in this way only work
3717 with Hardware Watchpoints.
3720 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3721 Set a watchpoint that will break when the value of @var{expr} is read
3725 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3726 Set a watchpoint that will break when @var{expr} is either read from
3727 or written into by the program.
3729 @kindex info watchpoints @r{[}@var{n}@r{]}
3730 @item info watchpoints
3731 This command prints a list of watchpoints, using the same format as
3732 @code{info break} (@pxref{Set Breaks}).
3735 If you watch for a change in a numerically entered address you need to
3736 dereference it, as the address itself is just a constant number which will
3737 never change. @value{GDBN} refuses to create a watchpoint that watches
3738 a never-changing value:
3741 (@value{GDBP}) watch 0x600850
3742 Cannot watch constant value 0x600850.
3743 (@value{GDBP}) watch *(int *) 0x600850
3744 Watchpoint 1: *(int *) 6293584
3747 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3748 watchpoints execute very quickly, and the debugger reports a change in
3749 value at the exact instruction where the change occurs. If @value{GDBN}
3750 cannot set a hardware watchpoint, it sets a software watchpoint, which
3751 executes more slowly and reports the change in value at the next
3752 @emph{statement}, not the instruction, after the change occurs.
3754 @cindex use only software watchpoints
3755 You can force @value{GDBN} to use only software watchpoints with the
3756 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3757 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3758 the underlying system supports them. (Note that hardware-assisted
3759 watchpoints that were set @emph{before} setting
3760 @code{can-use-hw-watchpoints} to zero will still use the hardware
3761 mechanism of watching expression values.)
3764 @item set can-use-hw-watchpoints
3765 @kindex set can-use-hw-watchpoints
3766 Set whether or not to use hardware watchpoints.
3768 @item show can-use-hw-watchpoints
3769 @kindex show can-use-hw-watchpoints
3770 Show the current mode of using hardware watchpoints.
3773 For remote targets, you can restrict the number of hardware
3774 watchpoints @value{GDBN} will use, see @ref{set remote
3775 hardware-breakpoint-limit}.
3777 When you issue the @code{watch} command, @value{GDBN} reports
3780 Hardware watchpoint @var{num}: @var{expr}
3784 if it was able to set a hardware watchpoint.
3786 Currently, the @code{awatch} and @code{rwatch} commands can only set
3787 hardware watchpoints, because accesses to data that don't change the
3788 value of the watched expression cannot be detected without examining
3789 every instruction as it is being executed, and @value{GDBN} does not do
3790 that currently. If @value{GDBN} finds that it is unable to set a
3791 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3792 will print a message like this:
3795 Expression cannot be implemented with read/access watchpoint.
3798 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3799 data type of the watched expression is wider than what a hardware
3800 watchpoint on the target machine can handle. For example, some systems
3801 can only watch regions that are up to 4 bytes wide; on such systems you
3802 cannot set hardware watchpoints for an expression that yields a
3803 double-precision floating-point number (which is typically 8 bytes
3804 wide). As a work-around, it might be possible to break the large region
3805 into a series of smaller ones and watch them with separate watchpoints.
3807 If you set too many hardware watchpoints, @value{GDBN} might be unable
3808 to insert all of them when you resume the execution of your program.
3809 Since the precise number of active watchpoints is unknown until such
3810 time as the program is about to be resumed, @value{GDBN} might not be
3811 able to warn you about this when you set the watchpoints, and the
3812 warning will be printed only when the program is resumed:
3815 Hardware watchpoint @var{num}: Could not insert watchpoint
3819 If this happens, delete or disable some of the watchpoints.
3821 Watching complex expressions that reference many variables can also
3822 exhaust the resources available for hardware-assisted watchpoints.
3823 That's because @value{GDBN} needs to watch every variable in the
3824 expression with separately allocated resources.
3826 If you call a function interactively using @code{print} or @code{call},
3827 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3828 kind of breakpoint or the call completes.
3830 @value{GDBN} automatically deletes watchpoints that watch local
3831 (automatic) variables, or expressions that involve such variables, when
3832 they go out of scope, that is, when the execution leaves the block in
3833 which these variables were defined. In particular, when the program
3834 being debugged terminates, @emph{all} local variables go out of scope,
3835 and so only watchpoints that watch global variables remain set. If you
3836 rerun the program, you will need to set all such watchpoints again. One
3837 way of doing that would be to set a code breakpoint at the entry to the
3838 @code{main} function and when it breaks, set all the watchpoints.
3840 @cindex watchpoints and threads
3841 @cindex threads and watchpoints
3842 In multi-threaded programs, watchpoints will detect changes to the
3843 watched expression from every thread.
3846 @emph{Warning:} In multi-threaded programs, software watchpoints
3847 have only limited usefulness. If @value{GDBN} creates a software
3848 watchpoint, it can only watch the value of an expression @emph{in a
3849 single thread}. If you are confident that the expression can only
3850 change due to the current thread's activity (and if you are also
3851 confident that no other thread can become current), then you can use
3852 software watchpoints as usual. However, @value{GDBN} may not notice
3853 when a non-current thread's activity changes the expression. (Hardware
3854 watchpoints, in contrast, watch an expression in all threads.)
3857 @xref{set remote hardware-watchpoint-limit}.
3859 @node Set Catchpoints
3860 @subsection Setting Catchpoints
3861 @cindex catchpoints, setting
3862 @cindex exception handlers
3863 @cindex event handling
3865 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3866 kinds of program events, such as C@t{++} exceptions or the loading of a
3867 shared library. Use the @code{catch} command to set a catchpoint.
3871 @item catch @var{event}
3872 Stop when @var{event} occurs. @var{event} can be any of the following:
3875 @cindex stop on C@t{++} exceptions
3876 The throwing of a C@t{++} exception.
3879 The catching of a C@t{++} exception.
3882 @cindex Ada exception catching
3883 @cindex catch Ada exceptions
3884 An Ada exception being raised. If an exception name is specified
3885 at the end of the command (eg @code{catch exception Program_Error}),
3886 the debugger will stop only when this specific exception is raised.
3887 Otherwise, the debugger stops execution when any Ada exception is raised.
3889 When inserting an exception catchpoint on a user-defined exception whose
3890 name is identical to one of the exceptions defined by the language, the
3891 fully qualified name must be used as the exception name. Otherwise,
3892 @value{GDBN} will assume that it should stop on the pre-defined exception
3893 rather than the user-defined one. For instance, assuming an exception
3894 called @code{Constraint_Error} is defined in package @code{Pck}, then
3895 the command to use to catch such exceptions is @kbd{catch exception
3896 Pck.Constraint_Error}.
3898 @item exception unhandled
3899 An exception that was raised but is not handled by the program.
3902 A failed Ada assertion.
3905 @cindex break on fork/exec
3906 A call to @code{exec}. This is currently only available for HP-UX
3910 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3911 @cindex break on a system call.
3912 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3913 syscall is a mechanism for application programs to request a service
3914 from the operating system (OS) or one of the OS system services.
3915 @value{GDBN} can catch some or all of the syscalls issued by the
3916 debuggee, and show the related information for each syscall. If no
3917 argument is specified, calls to and returns from all system calls
3920 @var{name} can be any system call name that is valid for the
3921 underlying OS. Just what syscalls are valid depends on the OS. On
3922 GNU and Unix systems, you can find the full list of valid syscall
3923 names on @file{/usr/include/asm/unistd.h}.
3925 @c For MS-Windows, the syscall names and the corresponding numbers
3926 @c can be found, e.g., on this URL:
3927 @c http://www.metasploit.com/users/opcode/syscalls.html
3928 @c but we don't support Windows syscalls yet.
3930 Normally, @value{GDBN} knows in advance which syscalls are valid for
3931 each OS, so you can use the @value{GDBN} command-line completion
3932 facilities (@pxref{Completion,, command completion}) to list the
3935 You may also specify the system call numerically. A syscall's
3936 number is the value passed to the OS's syscall dispatcher to
3937 identify the requested service. When you specify the syscall by its
3938 name, @value{GDBN} uses its database of syscalls to convert the name
3939 into the corresponding numeric code, but using the number directly
3940 may be useful if @value{GDBN}'s database does not have the complete
3941 list of syscalls on your system (e.g., because @value{GDBN} lags
3942 behind the OS upgrades).
3944 The example below illustrates how this command works if you don't provide
3948 (@value{GDBP}) catch syscall
3949 Catchpoint 1 (syscall)
3951 Starting program: /tmp/catch-syscall
3953 Catchpoint 1 (call to syscall 'close'), \
3954 0xffffe424 in __kernel_vsyscall ()
3958 Catchpoint 1 (returned from syscall 'close'), \
3959 0xffffe424 in __kernel_vsyscall ()
3963 Here is an example of catching a system call by name:
3966 (@value{GDBP}) catch syscall chroot
3967 Catchpoint 1 (syscall 'chroot' [61])
3969 Starting program: /tmp/catch-syscall
3971 Catchpoint 1 (call to syscall 'chroot'), \
3972 0xffffe424 in __kernel_vsyscall ()
3976 Catchpoint 1 (returned from syscall 'chroot'), \
3977 0xffffe424 in __kernel_vsyscall ()
3981 An example of specifying a system call numerically. In the case
3982 below, the syscall number has a corresponding entry in the XML
3983 file, so @value{GDBN} finds its name and prints it:
3986 (@value{GDBP}) catch syscall 252
3987 Catchpoint 1 (syscall(s) 'exit_group')
3989 Starting program: /tmp/catch-syscall
3991 Catchpoint 1 (call to syscall 'exit_group'), \
3992 0xffffe424 in __kernel_vsyscall ()
3996 Program exited normally.
4000 However, there can be situations when there is no corresponding name
4001 in XML file for that syscall number. In this case, @value{GDBN} prints
4002 a warning message saying that it was not able to find the syscall name,
4003 but the catchpoint will be set anyway. See the example below:
4006 (@value{GDBP}) catch syscall 764
4007 warning: The number '764' does not represent a known syscall.
4008 Catchpoint 2 (syscall 764)
4012 If you configure @value{GDBN} using the @samp{--without-expat} option,
4013 it will not be able to display syscall names. Also, if your
4014 architecture does not have an XML file describing its system calls,
4015 you will not be able to see the syscall names. It is important to
4016 notice that these two features are used for accessing the syscall
4017 name database. In either case, you will see a warning like this:
4020 (@value{GDBP}) catch syscall
4021 warning: Could not open "syscalls/i386-linux.xml"
4022 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4023 GDB will not be able to display syscall names.
4024 Catchpoint 1 (syscall)
4028 Of course, the file name will change depending on your architecture and system.
4030 Still using the example above, you can also try to catch a syscall by its
4031 number. In this case, you would see something like:
4034 (@value{GDBP}) catch syscall 252
4035 Catchpoint 1 (syscall(s) 252)
4038 Again, in this case @value{GDBN} would not be able to display syscall's names.
4041 A call to @code{fork}. This is currently only available for HP-UX
4045 A call to @code{vfork}. This is currently only available for HP-UX
4050 @item tcatch @var{event}
4051 Set a catchpoint that is enabled only for one stop. The catchpoint is
4052 automatically deleted after the first time the event is caught.
4056 Use the @code{info break} command to list the current catchpoints.
4058 There are currently some limitations to C@t{++} exception handling
4059 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4063 If you call a function interactively, @value{GDBN} normally returns
4064 control to you when the function has finished executing. If the call
4065 raises an exception, however, the call may bypass the mechanism that
4066 returns control to you and cause your program either to abort or to
4067 simply continue running until it hits a breakpoint, catches a signal
4068 that @value{GDBN} is listening for, or exits. This is the case even if
4069 you set a catchpoint for the exception; catchpoints on exceptions are
4070 disabled within interactive calls.
4073 You cannot raise an exception interactively.
4076 You cannot install an exception handler interactively.
4079 @cindex raise exceptions
4080 Sometimes @code{catch} is not the best way to debug exception handling:
4081 if you need to know exactly where an exception is raised, it is better to
4082 stop @emph{before} the exception handler is called, since that way you
4083 can see the stack before any unwinding takes place. If you set a
4084 breakpoint in an exception handler instead, it may not be easy to find
4085 out where the exception was raised.
4087 To stop just before an exception handler is called, you need some
4088 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4089 raised by calling a library function named @code{__raise_exception}
4090 which has the following ANSI C interface:
4093 /* @var{addr} is where the exception identifier is stored.
4094 @var{id} is the exception identifier. */
4095 void __raise_exception (void **addr, void *id);
4099 To make the debugger catch all exceptions before any stack
4100 unwinding takes place, set a breakpoint on @code{__raise_exception}
4101 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4103 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4104 that depends on the value of @var{id}, you can stop your program when
4105 a specific exception is raised. You can use multiple conditional
4106 breakpoints to stop your program when any of a number of exceptions are
4111 @subsection Deleting Breakpoints
4113 @cindex clearing breakpoints, watchpoints, catchpoints
4114 @cindex deleting breakpoints, watchpoints, catchpoints
4115 It is often necessary to eliminate a breakpoint, watchpoint, or
4116 catchpoint once it has done its job and you no longer want your program
4117 to stop there. This is called @dfn{deleting} the breakpoint. A
4118 breakpoint that has been deleted no longer exists; it is forgotten.
4120 With the @code{clear} command you can delete breakpoints according to
4121 where they are in your program. With the @code{delete} command you can
4122 delete individual breakpoints, watchpoints, or catchpoints by specifying
4123 their breakpoint numbers.
4125 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4126 automatically ignores breakpoints on the first instruction to be executed
4127 when you continue execution without changing the execution address.
4132 Delete any breakpoints at the next instruction to be executed in the
4133 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4134 the innermost frame is selected, this is a good way to delete a
4135 breakpoint where your program just stopped.
4137 @item clear @var{location}
4138 Delete any breakpoints set at the specified @var{location}.
4139 @xref{Specify Location}, for the various forms of @var{location}; the
4140 most useful ones are listed below:
4143 @item clear @var{function}
4144 @itemx clear @var{filename}:@var{function}
4145 Delete any breakpoints set at entry to the named @var{function}.
4147 @item clear @var{linenum}
4148 @itemx clear @var{filename}:@var{linenum}
4149 Delete any breakpoints set at or within the code of the specified
4150 @var{linenum} of the specified @var{filename}.
4153 @cindex delete breakpoints
4155 @kindex d @r{(@code{delete})}
4156 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4157 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4158 ranges specified as arguments. If no argument is specified, delete all
4159 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4160 confirm off}). You can abbreviate this command as @code{d}.
4164 @subsection Disabling Breakpoints
4166 @cindex enable/disable a breakpoint
4167 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4168 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4169 it had been deleted, but remembers the information on the breakpoint so
4170 that you can @dfn{enable} it again later.
4172 You disable and enable breakpoints, watchpoints, and catchpoints with
4173 the @code{enable} and @code{disable} commands, optionally specifying
4174 one or more breakpoint numbers as arguments. Use @code{info break} to
4175 print a list of all breakpoints, watchpoints, and catchpoints if you
4176 do not know which numbers to use.
4178 Disabling and enabling a breakpoint that has multiple locations
4179 affects all of its locations.
4181 A breakpoint, watchpoint, or catchpoint can have any of four different
4182 states of enablement:
4186 Enabled. The breakpoint stops your program. A breakpoint set
4187 with the @code{break} command starts out in this state.
4189 Disabled. The breakpoint has no effect on your program.
4191 Enabled once. The breakpoint stops your program, but then becomes
4194 Enabled for deletion. The breakpoint stops your program, but
4195 immediately after it does so it is deleted permanently. A breakpoint
4196 set with the @code{tbreak} command starts out in this state.
4199 You can use the following commands to enable or disable breakpoints,
4200 watchpoints, and catchpoints:
4204 @kindex dis @r{(@code{disable})}
4205 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4206 Disable the specified breakpoints---or all breakpoints, if none are
4207 listed. A disabled breakpoint has no effect but is not forgotten. All
4208 options such as ignore-counts, conditions and commands are remembered in
4209 case the breakpoint is enabled again later. You may abbreviate
4210 @code{disable} as @code{dis}.
4213 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4214 Enable the specified breakpoints (or all defined breakpoints). They
4215 become effective once again in stopping your program.
4217 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4218 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4219 of these breakpoints immediately after stopping your program.
4221 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4222 Enable the specified breakpoints to work once, then die. @value{GDBN}
4223 deletes any of these breakpoints as soon as your program stops there.
4224 Breakpoints set by the @code{tbreak} command start out in this state.
4227 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4228 @c confusing: tbreak is also initially enabled.
4229 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4230 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4231 subsequently, they become disabled or enabled only when you use one of
4232 the commands above. (The command @code{until} can set and delete a
4233 breakpoint of its own, but it does not change the state of your other
4234 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4238 @subsection Break Conditions
4239 @cindex conditional breakpoints
4240 @cindex breakpoint conditions
4242 @c FIXME what is scope of break condition expr? Context where wanted?
4243 @c in particular for a watchpoint?
4244 The simplest sort of breakpoint breaks every time your program reaches a
4245 specified place. You can also specify a @dfn{condition} for a
4246 breakpoint. A condition is just a Boolean expression in your
4247 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4248 a condition evaluates the expression each time your program reaches it,
4249 and your program stops only if the condition is @emph{true}.
4251 This is the converse of using assertions for program validation; in that
4252 situation, you want to stop when the assertion is violated---that is,
4253 when the condition is false. In C, if you want to test an assertion expressed
4254 by the condition @var{assert}, you should set the condition
4255 @samp{! @var{assert}} on the appropriate breakpoint.
4257 Conditions are also accepted for watchpoints; you may not need them,
4258 since a watchpoint is inspecting the value of an expression anyhow---but
4259 it might be simpler, say, to just set a watchpoint on a variable name,
4260 and specify a condition that tests whether the new value is an interesting
4263 Break conditions can have side effects, and may even call functions in
4264 your program. This can be useful, for example, to activate functions
4265 that log program progress, or to use your own print functions to
4266 format special data structures. The effects are completely predictable
4267 unless there is another enabled breakpoint at the same address. (In
4268 that case, @value{GDBN} might see the other breakpoint first and stop your
4269 program without checking the condition of this one.) Note that
4270 breakpoint commands are usually more convenient and flexible than break
4272 purpose of performing side effects when a breakpoint is reached
4273 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4275 Break conditions can be specified when a breakpoint is set, by using
4276 @samp{if} in the arguments to the @code{break} command. @xref{Set
4277 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4278 with the @code{condition} command.
4280 You can also use the @code{if} keyword with the @code{watch} command.
4281 The @code{catch} command does not recognize the @code{if} keyword;
4282 @code{condition} is the only way to impose a further condition on a
4287 @item condition @var{bnum} @var{expression}
4288 Specify @var{expression} as the break condition for breakpoint,
4289 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4290 breakpoint @var{bnum} stops your program only if the value of
4291 @var{expression} is true (nonzero, in C). When you use
4292 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4293 syntactic correctness, and to determine whether symbols in it have
4294 referents in the context of your breakpoint. If @var{expression} uses
4295 symbols not referenced in the context of the breakpoint, @value{GDBN}
4296 prints an error message:
4299 No symbol "foo" in current context.
4304 not actually evaluate @var{expression} at the time the @code{condition}
4305 command (or a command that sets a breakpoint with a condition, like
4306 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4308 @item condition @var{bnum}
4309 Remove the condition from breakpoint number @var{bnum}. It becomes
4310 an ordinary unconditional breakpoint.
4313 @cindex ignore count (of breakpoint)
4314 A special case of a breakpoint condition is to stop only when the
4315 breakpoint has been reached a certain number of times. This is so
4316 useful that there is a special way to do it, using the @dfn{ignore
4317 count} of the breakpoint. Every breakpoint has an ignore count, which
4318 is an integer. Most of the time, the ignore count is zero, and
4319 therefore has no effect. But if your program reaches a breakpoint whose
4320 ignore count is positive, then instead of stopping, it just decrements
4321 the ignore count by one and continues. As a result, if the ignore count
4322 value is @var{n}, the breakpoint does not stop the next @var{n} times
4323 your program reaches it.
4327 @item ignore @var{bnum} @var{count}
4328 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4329 The next @var{count} times the breakpoint is reached, your program's
4330 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4333 To make the breakpoint stop the next time it is reached, specify
4336 When you use @code{continue} to resume execution of your program from a
4337 breakpoint, you can specify an ignore count directly as an argument to
4338 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4339 Stepping,,Continuing and Stepping}.
4341 If a breakpoint has a positive ignore count and a condition, the
4342 condition is not checked. Once the ignore count reaches zero,
4343 @value{GDBN} resumes checking the condition.
4345 You could achieve the effect of the ignore count with a condition such
4346 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4347 is decremented each time. @xref{Convenience Vars, ,Convenience
4351 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4354 @node Break Commands
4355 @subsection Breakpoint Command Lists
4357 @cindex breakpoint commands
4358 You can give any breakpoint (or watchpoint or catchpoint) a series of
4359 commands to execute when your program stops due to that breakpoint. For
4360 example, you might want to print the values of certain expressions, or
4361 enable other breakpoints.
4365 @kindex end@r{ (breakpoint commands)}
4366 @item commands @r{[}@var{range}@dots{}@r{]}
4367 @itemx @dots{} @var{command-list} @dots{}
4369 Specify a list of commands for the given breakpoints. The commands
4370 themselves appear on the following lines. Type a line containing just
4371 @code{end} to terminate the commands.
4373 To remove all commands from a breakpoint, type @code{commands} and
4374 follow it immediately with @code{end}; that is, give no commands.
4376 With no argument, @code{commands} refers to the last breakpoint,
4377 watchpoint, or catchpoint set (not to the breakpoint most recently
4378 encountered). If the most recent breakpoints were set with a single
4379 command, then the @code{commands} will apply to all the breakpoints
4380 set by that command. This applies to breakpoints set by
4381 @code{rbreak}, and also applies when a single @code{break} command
4382 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4386 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4387 disabled within a @var{command-list}.
4389 You can use breakpoint commands to start your program up again. Simply
4390 use the @code{continue} command, or @code{step}, or any other command
4391 that resumes execution.
4393 Any other commands in the command list, after a command that resumes
4394 execution, are ignored. This is because any time you resume execution
4395 (even with a simple @code{next} or @code{step}), you may encounter
4396 another breakpoint---which could have its own command list, leading to
4397 ambiguities about which list to execute.
4400 If the first command you specify in a command list is @code{silent}, the
4401 usual message about stopping at a breakpoint is not printed. This may
4402 be desirable for breakpoints that are to print a specific message and
4403 then continue. If none of the remaining commands print anything, you
4404 see no sign that the breakpoint was reached. @code{silent} is
4405 meaningful only at the beginning of a breakpoint command list.
4407 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4408 print precisely controlled output, and are often useful in silent
4409 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4411 For example, here is how you could use breakpoint commands to print the
4412 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4418 printf "x is %d\n",x
4423 One application for breakpoint commands is to compensate for one bug so
4424 you can test for another. Put a breakpoint just after the erroneous line
4425 of code, give it a condition to detect the case in which something
4426 erroneous has been done, and give it commands to assign correct values
4427 to any variables that need them. End with the @code{continue} command
4428 so that your program does not stop, and start with the @code{silent}
4429 command so that no output is produced. Here is an example:
4440 @node Save Breakpoints
4441 @subsection How to save breakpoints to a file
4443 To save breakpoint definitions to a file use the @w{@code{save
4444 breakpoints}} command.
4447 @kindex save breakpoints
4448 @cindex save breakpoints to a file for future sessions
4449 @item save breakpoints [@var{filename}]
4450 This command saves all current breakpoint definitions together with
4451 their commands and ignore counts, into a file @file{@var{filename}}
4452 suitable for use in a later debugging session. This includes all
4453 types of breakpoints (breakpoints, watchpoints, catchpoints,
4454 tracepoints). To read the saved breakpoint definitions, use the
4455 @code{source} command (@pxref{Command Files}). Note that watchpoints
4456 with expressions involving local variables may fail to be recreated
4457 because it may not be possible to access the context where the
4458 watchpoint is valid anymore. Because the saved breakpoint definitions
4459 are simply a sequence of @value{GDBN} commands that recreate the
4460 breakpoints, you can edit the file in your favorite editing program,
4461 and remove the breakpoint definitions you're not interested in, or
4462 that can no longer be recreated.
4465 @c @ifclear BARETARGET
4466 @node Error in Breakpoints
4467 @subsection ``Cannot insert breakpoints''
4469 If you request too many active hardware-assisted breakpoints and
4470 watchpoints, you will see this error message:
4472 @c FIXME: the precise wording of this message may change; the relevant
4473 @c source change is not committed yet (Sep 3, 1999).
4475 Stopped; cannot insert breakpoints.
4476 You may have requested too many hardware breakpoints and watchpoints.
4480 This message is printed when you attempt to resume the program, since
4481 only then @value{GDBN} knows exactly how many hardware breakpoints and
4482 watchpoints it needs to insert.
4484 When this message is printed, you need to disable or remove some of the
4485 hardware-assisted breakpoints and watchpoints, and then continue.
4487 @node Breakpoint-related Warnings
4488 @subsection ``Breakpoint address adjusted...''
4489 @cindex breakpoint address adjusted
4491 Some processor architectures place constraints on the addresses at
4492 which breakpoints may be placed. For architectures thus constrained,
4493 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4494 with the constraints dictated by the architecture.
4496 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4497 a VLIW architecture in which a number of RISC-like instructions may be
4498 bundled together for parallel execution. The FR-V architecture
4499 constrains the location of a breakpoint instruction within such a
4500 bundle to the instruction with the lowest address. @value{GDBN}
4501 honors this constraint by adjusting a breakpoint's address to the
4502 first in the bundle.
4504 It is not uncommon for optimized code to have bundles which contain
4505 instructions from different source statements, thus it may happen that
4506 a breakpoint's address will be adjusted from one source statement to
4507 another. Since this adjustment may significantly alter @value{GDBN}'s
4508 breakpoint related behavior from what the user expects, a warning is
4509 printed when the breakpoint is first set and also when the breakpoint
4512 A warning like the one below is printed when setting a breakpoint
4513 that's been subject to address adjustment:
4516 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4519 Such warnings are printed both for user settable and @value{GDBN}'s
4520 internal breakpoints. If you see one of these warnings, you should
4521 verify that a breakpoint set at the adjusted address will have the
4522 desired affect. If not, the breakpoint in question may be removed and
4523 other breakpoints may be set which will have the desired behavior.
4524 E.g., it may be sufficient to place the breakpoint at a later
4525 instruction. A conditional breakpoint may also be useful in some
4526 cases to prevent the breakpoint from triggering too often.
4528 @value{GDBN} will also issue a warning when stopping at one of these
4529 adjusted breakpoints:
4532 warning: Breakpoint 1 address previously adjusted from 0x00010414
4536 When this warning is encountered, it may be too late to take remedial
4537 action except in cases where the breakpoint is hit earlier or more
4538 frequently than expected.
4540 @node Continuing and Stepping
4541 @section Continuing and Stepping
4545 @cindex resuming execution
4546 @dfn{Continuing} means resuming program execution until your program
4547 completes normally. In contrast, @dfn{stepping} means executing just
4548 one more ``step'' of your program, where ``step'' may mean either one
4549 line of source code, or one machine instruction (depending on what
4550 particular command you use). Either when continuing or when stepping,
4551 your program may stop even sooner, due to a breakpoint or a signal. (If
4552 it stops due to a signal, you may want to use @code{handle}, or use
4553 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4557 @kindex c @r{(@code{continue})}
4558 @kindex fg @r{(resume foreground execution)}
4559 @item continue @r{[}@var{ignore-count}@r{]}
4560 @itemx c @r{[}@var{ignore-count}@r{]}
4561 @itemx fg @r{[}@var{ignore-count}@r{]}
4562 Resume program execution, at the address where your program last stopped;
4563 any breakpoints set at that address are bypassed. The optional argument
4564 @var{ignore-count} allows you to specify a further number of times to
4565 ignore a breakpoint at this location; its effect is like that of
4566 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4568 The argument @var{ignore-count} is meaningful only when your program
4569 stopped due to a breakpoint. At other times, the argument to
4570 @code{continue} is ignored.
4572 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4573 debugged program is deemed to be the foreground program) are provided
4574 purely for convenience, and have exactly the same behavior as
4578 To resume execution at a different place, you can use @code{return}
4579 (@pxref{Returning, ,Returning from a Function}) to go back to the
4580 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4581 Different Address}) to go to an arbitrary location in your program.
4583 A typical technique for using stepping is to set a breakpoint
4584 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4585 beginning of the function or the section of your program where a problem
4586 is believed to lie, run your program until it stops at that breakpoint,
4587 and then step through the suspect area, examining the variables that are
4588 interesting, until you see the problem happen.
4592 @kindex s @r{(@code{step})}
4594 Continue running your program until control reaches a different source
4595 line, then stop it and return control to @value{GDBN}. This command is
4596 abbreviated @code{s}.
4599 @c "without debugging information" is imprecise; actually "without line
4600 @c numbers in the debugging information". (gcc -g1 has debugging info but
4601 @c not line numbers). But it seems complex to try to make that
4602 @c distinction here.
4603 @emph{Warning:} If you use the @code{step} command while control is
4604 within a function that was compiled without debugging information,
4605 execution proceeds until control reaches a function that does have
4606 debugging information. Likewise, it will not step into a function which
4607 is compiled without debugging information. To step through functions
4608 without debugging information, use the @code{stepi} command, described
4612 The @code{step} command only stops at the first instruction of a source
4613 line. This prevents the multiple stops that could otherwise occur in
4614 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4615 to stop if a function that has debugging information is called within
4616 the line. In other words, @code{step} @emph{steps inside} any functions
4617 called within the line.
4619 Also, the @code{step} command only enters a function if there is line
4620 number information for the function. Otherwise it acts like the
4621 @code{next} command. This avoids problems when using @code{cc -gl}
4622 on MIPS machines. Previously, @code{step} entered subroutines if there
4623 was any debugging information about the routine.
4625 @item step @var{count}
4626 Continue running as in @code{step}, but do so @var{count} times. If a
4627 breakpoint is reached, or a signal not related to stepping occurs before
4628 @var{count} steps, stepping stops right away.
4631 @kindex n @r{(@code{next})}
4632 @item next @r{[}@var{count}@r{]}
4633 Continue to the next source line in the current (innermost) stack frame.
4634 This is similar to @code{step}, but function calls that appear within
4635 the line of code are executed without stopping. Execution stops when
4636 control reaches a different line of code at the original stack level
4637 that was executing when you gave the @code{next} command. This command
4638 is abbreviated @code{n}.
4640 An argument @var{count} is a repeat count, as for @code{step}.
4643 @c FIX ME!! Do we delete this, or is there a way it fits in with
4644 @c the following paragraph? --- Vctoria
4646 @c @code{next} within a function that lacks debugging information acts like
4647 @c @code{step}, but any function calls appearing within the code of the
4648 @c function are executed without stopping.
4650 The @code{next} command only stops at the first instruction of a
4651 source line. This prevents multiple stops that could otherwise occur in
4652 @code{switch} statements, @code{for} loops, etc.
4654 @kindex set step-mode
4656 @cindex functions without line info, and stepping
4657 @cindex stepping into functions with no line info
4658 @itemx set step-mode on
4659 The @code{set step-mode on} command causes the @code{step} command to
4660 stop at the first instruction of a function which contains no debug line
4661 information rather than stepping over it.
4663 This is useful in cases where you may be interested in inspecting the
4664 machine instructions of a function which has no symbolic info and do not
4665 want @value{GDBN} to automatically skip over this function.
4667 @item set step-mode off
4668 Causes the @code{step} command to step over any functions which contains no
4669 debug information. This is the default.
4671 @item show step-mode
4672 Show whether @value{GDBN} will stop in or step over functions without
4673 source line debug information.
4676 @kindex fin @r{(@code{finish})}
4678 Continue running until just after function in the selected stack frame
4679 returns. Print the returned value (if any). This command can be
4680 abbreviated as @code{fin}.
4682 Contrast this with the @code{return} command (@pxref{Returning,
4683 ,Returning from a Function}).
4686 @kindex u @r{(@code{until})}
4687 @cindex run until specified location
4690 Continue running until a source line past the current line, in the
4691 current stack frame, is reached. This command is used to avoid single
4692 stepping through a loop more than once. It is like the @code{next}
4693 command, except that when @code{until} encounters a jump, it
4694 automatically continues execution until the program counter is greater
4695 than the address of the jump.
4697 This means that when you reach the end of a loop after single stepping
4698 though it, @code{until} makes your program continue execution until it
4699 exits the loop. In contrast, a @code{next} command at the end of a loop
4700 simply steps back to the beginning of the loop, which forces you to step
4701 through the next iteration.
4703 @code{until} always stops your program if it attempts to exit the current
4706 @code{until} may produce somewhat counterintuitive results if the order
4707 of machine code does not match the order of the source lines. For
4708 example, in the following excerpt from a debugging session, the @code{f}
4709 (@code{frame}) command shows that execution is stopped at line
4710 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4714 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4716 (@value{GDBP}) until
4717 195 for ( ; argc > 0; NEXTARG) @{
4720 This happened because, for execution efficiency, the compiler had
4721 generated code for the loop closure test at the end, rather than the
4722 start, of the loop---even though the test in a C @code{for}-loop is
4723 written before the body of the loop. The @code{until} command appeared
4724 to step back to the beginning of the loop when it advanced to this
4725 expression; however, it has not really gone to an earlier
4726 statement---not in terms of the actual machine code.
4728 @code{until} with no argument works by means of single
4729 instruction stepping, and hence is slower than @code{until} with an
4732 @item until @var{location}
4733 @itemx u @var{location}
4734 Continue running your program until either the specified location is
4735 reached, or the current stack frame returns. @var{location} is any of
4736 the forms described in @ref{Specify Location}.
4737 This form of the command uses temporary breakpoints, and
4738 hence is quicker than @code{until} without an argument. The specified
4739 location is actually reached only if it is in the current frame. This
4740 implies that @code{until} can be used to skip over recursive function
4741 invocations. For instance in the code below, if the current location is
4742 line @code{96}, issuing @code{until 99} will execute the program up to
4743 line @code{99} in the same invocation of factorial, i.e., after the inner
4744 invocations have returned.
4747 94 int factorial (int value)
4749 96 if (value > 1) @{
4750 97 value *= factorial (value - 1);
4757 @kindex advance @var{location}
4758 @itemx advance @var{location}
4759 Continue running the program up to the given @var{location}. An argument is
4760 required, which should be of one of the forms described in
4761 @ref{Specify Location}.
4762 Execution will also stop upon exit from the current stack
4763 frame. This command is similar to @code{until}, but @code{advance} will
4764 not skip over recursive function calls, and the target location doesn't
4765 have to be in the same frame as the current one.
4769 @kindex si @r{(@code{stepi})}
4771 @itemx stepi @var{arg}
4773 Execute one machine instruction, then stop and return to the debugger.
4775 It is often useful to do @samp{display/i $pc} when stepping by machine
4776 instructions. This makes @value{GDBN} automatically display the next
4777 instruction to be executed, each time your program stops. @xref{Auto
4778 Display,, Automatic Display}.
4780 An argument is a repeat count, as in @code{step}.
4784 @kindex ni @r{(@code{nexti})}
4786 @itemx nexti @var{arg}
4788 Execute one machine instruction, but if it is a function call,
4789 proceed until the function returns.
4791 An argument is a repeat count, as in @code{next}.
4798 A signal is an asynchronous event that can happen in a program. The
4799 operating system defines the possible kinds of signals, and gives each
4800 kind a name and a number. For example, in Unix @code{SIGINT} is the
4801 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4802 @code{SIGSEGV} is the signal a program gets from referencing a place in
4803 memory far away from all the areas in use; @code{SIGALRM} occurs when
4804 the alarm clock timer goes off (which happens only if your program has
4805 requested an alarm).
4807 @cindex fatal signals
4808 Some signals, including @code{SIGALRM}, are a normal part of the
4809 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4810 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4811 program has not specified in advance some other way to handle the signal.
4812 @code{SIGINT} does not indicate an error in your program, but it is normally
4813 fatal so it can carry out the purpose of the interrupt: to kill the program.
4815 @value{GDBN} has the ability to detect any occurrence of a signal in your
4816 program. You can tell @value{GDBN} in advance what to do for each kind of
4819 @cindex handling signals
4820 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4821 @code{SIGALRM} be silently passed to your program
4822 (so as not to interfere with their role in the program's functioning)
4823 but to stop your program immediately whenever an error signal happens.
4824 You can change these settings with the @code{handle} command.
4827 @kindex info signals
4831 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4832 handle each one. You can use this to see the signal numbers of all
4833 the defined types of signals.
4835 @item info signals @var{sig}
4836 Similar, but print information only about the specified signal number.
4838 @code{info handle} is an alias for @code{info signals}.
4841 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4842 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4843 can be the number of a signal or its name (with or without the
4844 @samp{SIG} at the beginning); a list of signal numbers of the form
4845 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4846 known signals. Optional arguments @var{keywords}, described below,
4847 say what change to make.
4851 The keywords allowed by the @code{handle} command can be abbreviated.
4852 Their full names are:
4856 @value{GDBN} should not stop your program when this signal happens. It may
4857 still print a message telling you that the signal has come in.
4860 @value{GDBN} should stop your program when this signal happens. This implies
4861 the @code{print} keyword as well.
4864 @value{GDBN} should print a message when this signal happens.
4867 @value{GDBN} should not mention the occurrence of the signal at all. This
4868 implies the @code{nostop} keyword as well.
4872 @value{GDBN} should allow your program to see this signal; your program
4873 can handle the signal, or else it may terminate if the signal is fatal
4874 and not handled. @code{pass} and @code{noignore} are synonyms.
4878 @value{GDBN} should not allow your program to see this signal.
4879 @code{nopass} and @code{ignore} are synonyms.
4883 When a signal stops your program, the signal is not visible to the
4885 continue. Your program sees the signal then, if @code{pass} is in
4886 effect for the signal in question @emph{at that time}. In other words,
4887 after @value{GDBN} reports a signal, you can use the @code{handle}
4888 command with @code{pass} or @code{nopass} to control whether your
4889 program sees that signal when you continue.
4891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4896 You can also use the @code{signal} command to prevent your program from
4897 seeing a signal, or cause it to see a signal it normally would not see,
4898 or to give it any signal at any time. For example, if your program stopped
4899 due to some sort of memory reference error, you might store correct
4900 values into the erroneous variables and continue, hoping to see more
4901 execution; but your program would probably terminate immediately as
4902 a result of the fatal signal once it saw the signal. To prevent this,
4903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4906 @cindex extra signal information
4907 @anchor{extra signal information}
4909 On some targets, @value{GDBN} can inspect extra signal information
4910 associated with the intercepted signal, before it is actually
4911 delivered to the program being debugged. This information is exported
4912 by the convenience variable @code{$_siginfo}, and consists of data
4913 that is passed by the kernel to the signal handler at the time of the
4914 receipt of a signal. The data type of the information itself is
4915 target dependent. You can see the data type using the @code{ptype
4916 $_siginfo} command. On Unix systems, it typically corresponds to the
4917 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4920 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4921 referenced address that raised a segmentation fault.
4925 (@value{GDBP}) continue
4926 Program received signal SIGSEGV, Segmentation fault.
4927 0x0000000000400766 in main ()
4929 (@value{GDBP}) ptype $_siginfo
4936 struct @{...@} _kill;
4937 struct @{...@} _timer;
4939 struct @{...@} _sigchld;
4940 struct @{...@} _sigfault;
4941 struct @{...@} _sigpoll;
4944 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4948 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4949 $1 = (void *) 0x7ffff7ff7000
4953 Depending on target support, @code{$_siginfo} may also be writable.
4956 @section Stopping and Starting Multi-thread Programs
4958 @cindex stopped threads
4959 @cindex threads, stopped
4961 @cindex continuing threads
4962 @cindex threads, continuing
4964 @value{GDBN} supports debugging programs with multiple threads
4965 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4966 are two modes of controlling execution of your program within the
4967 debugger. In the default mode, referred to as @dfn{all-stop mode},
4968 when any thread in your program stops (for example, at a breakpoint
4969 or while being stepped), all other threads in the program are also stopped by
4970 @value{GDBN}. On some targets, @value{GDBN} also supports
4971 @dfn{non-stop mode}, in which other threads can continue to run freely while
4972 you examine the stopped thread in the debugger.
4975 * All-Stop Mode:: All threads stop when GDB takes control
4976 * Non-Stop Mode:: Other threads continue to execute
4977 * Background Execution:: Running your program asynchronously
4978 * Thread-Specific Breakpoints:: Controlling breakpoints
4979 * Interrupted System Calls:: GDB may interfere with system calls
4980 * Observer Mode:: GDB does not alter program behavior
4984 @subsection All-Stop Mode
4986 @cindex all-stop mode
4988 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4989 @emph{all} threads of execution stop, not just the current thread. This
4990 allows you to examine the overall state of the program, including
4991 switching between threads, without worrying that things may change
4994 Conversely, whenever you restart the program, @emph{all} threads start
4995 executing. @emph{This is true even when single-stepping} with commands
4996 like @code{step} or @code{next}.
4998 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4999 Since thread scheduling is up to your debugging target's operating
5000 system (not controlled by @value{GDBN}), other threads may
5001 execute more than one statement while the current thread completes a
5002 single step. Moreover, in general other threads stop in the middle of a
5003 statement, rather than at a clean statement boundary, when the program
5006 You might even find your program stopped in another thread after
5007 continuing or even single-stepping. This happens whenever some other
5008 thread runs into a breakpoint, a signal, or an exception before the
5009 first thread completes whatever you requested.
5011 @cindex automatic thread selection
5012 @cindex switching threads automatically
5013 @cindex threads, automatic switching
5014 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5015 signal, it automatically selects the thread where that breakpoint or
5016 signal happened. @value{GDBN} alerts you to the context switch with a
5017 message such as @samp{[Switching to Thread @var{n}]} to identify the
5020 On some OSes, you can modify @value{GDBN}'s default behavior by
5021 locking the OS scheduler to allow only a single thread to run.
5024 @item set scheduler-locking @var{mode}
5025 @cindex scheduler locking mode
5026 @cindex lock scheduler
5027 Set the scheduler locking mode. If it is @code{off}, then there is no
5028 locking and any thread may run at any time. If @code{on}, then only the
5029 current thread may run when the inferior is resumed. The @code{step}
5030 mode optimizes for single-stepping; it prevents other threads
5031 from preempting the current thread while you are stepping, so that
5032 the focus of debugging does not change unexpectedly.
5033 Other threads only rarely (or never) get a chance to run
5034 when you step. They are more likely to run when you @samp{next} over a
5035 function call, and they are completely free to run when you use commands
5036 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5037 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5038 the current thread away from the thread that you are debugging.
5040 @item show scheduler-locking
5041 Display the current scheduler locking mode.
5044 @cindex resume threads of multiple processes simultaneously
5045 By default, when you issue one of the execution commands such as
5046 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5047 threads of the current inferior to run. For example, if @value{GDBN}
5048 is attached to two inferiors, each with two threads, the
5049 @code{continue} command resumes only the two threads of the current
5050 inferior. This is useful, for example, when you debug a program that
5051 forks and you want to hold the parent stopped (so that, for instance,
5052 it doesn't run to exit), while you debug the child. In other
5053 situations, you may not be interested in inspecting the current state
5054 of any of the processes @value{GDBN} is attached to, and you may want
5055 to resume them all until some breakpoint is hit. In the latter case,
5056 you can instruct @value{GDBN} to allow all threads of all the
5057 inferiors to run with the @w{@code{set schedule-multiple}} command.
5060 @kindex set schedule-multiple
5061 @item set schedule-multiple
5062 Set the mode for allowing threads of multiple processes to be resumed
5063 when an execution command is issued. When @code{on}, all threads of
5064 all processes are allowed to run. When @code{off}, only the threads
5065 of the current process are resumed. The default is @code{off}. The
5066 @code{scheduler-locking} mode takes precedence when set to @code{on},
5067 or while you are stepping and set to @code{step}.
5069 @item show schedule-multiple
5070 Display the current mode for resuming the execution of threads of
5075 @subsection Non-Stop Mode
5077 @cindex non-stop mode
5079 @c This section is really only a place-holder, and needs to be expanded
5080 @c with more details.
5082 For some multi-threaded targets, @value{GDBN} supports an optional
5083 mode of operation in which you can examine stopped program threads in
5084 the debugger while other threads continue to execute freely. This
5085 minimizes intrusion when debugging live systems, such as programs
5086 where some threads have real-time constraints or must continue to
5087 respond to external events. This is referred to as @dfn{non-stop} mode.
5089 In non-stop mode, when a thread stops to report a debugging event,
5090 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5091 threads as well, in contrast to the all-stop mode behavior. Additionally,
5092 execution commands such as @code{continue} and @code{step} apply by default
5093 only to the current thread in non-stop mode, rather than all threads as
5094 in all-stop mode. This allows you to control threads explicitly in
5095 ways that are not possible in all-stop mode --- for example, stepping
5096 one thread while allowing others to run freely, stepping
5097 one thread while holding all others stopped, or stepping several threads
5098 independently and simultaneously.
5100 To enter non-stop mode, use this sequence of commands before you run
5101 or attach to your program:
5104 # Enable the async interface.
5107 # If using the CLI, pagination breaks non-stop.
5110 # Finally, turn it on!
5114 You can use these commands to manipulate the non-stop mode setting:
5117 @kindex set non-stop
5118 @item set non-stop on
5119 Enable selection of non-stop mode.
5120 @item set non-stop off
5121 Disable selection of non-stop mode.
5122 @kindex show non-stop
5124 Show the current non-stop enablement setting.
5127 Note these commands only reflect whether non-stop mode is enabled,
5128 not whether the currently-executing program is being run in non-stop mode.
5129 In particular, the @code{set non-stop} preference is only consulted when
5130 @value{GDBN} starts or connects to the target program, and it is generally
5131 not possible to switch modes once debugging has started. Furthermore,
5132 since not all targets support non-stop mode, even when you have enabled
5133 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5136 In non-stop mode, all execution commands apply only to the current thread
5137 by default. That is, @code{continue} only continues one thread.
5138 To continue all threads, issue @code{continue -a} or @code{c -a}.
5140 You can use @value{GDBN}'s background execution commands
5141 (@pxref{Background Execution}) to run some threads in the background
5142 while you continue to examine or step others from @value{GDBN}.
5143 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5144 always executed asynchronously in non-stop mode.
5146 Suspending execution is done with the @code{interrupt} command when
5147 running in the background, or @kbd{Ctrl-c} during foreground execution.
5148 In all-stop mode, this stops the whole process;
5149 but in non-stop mode the interrupt applies only to the current thread.
5150 To stop the whole program, use @code{interrupt -a}.
5152 Other execution commands do not currently support the @code{-a} option.
5154 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5155 that thread current, as it does in all-stop mode. This is because the
5156 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5157 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5158 changed to a different thread just as you entered a command to operate on the
5159 previously current thread.
5161 @node Background Execution
5162 @subsection Background Execution
5164 @cindex foreground execution
5165 @cindex background execution
5166 @cindex asynchronous execution
5167 @cindex execution, foreground, background and asynchronous
5169 @value{GDBN}'s execution commands have two variants: the normal
5170 foreground (synchronous) behavior, and a background
5171 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5172 the program to report that some thread has stopped before prompting for
5173 another command. In background execution, @value{GDBN} immediately gives
5174 a command prompt so that you can issue other commands while your program runs.
5176 You need to explicitly enable asynchronous mode before you can use
5177 background execution commands. You can use these commands to
5178 manipulate the asynchronous mode setting:
5181 @kindex set target-async
5182 @item set target-async on
5183 Enable asynchronous mode.
5184 @item set target-async off
5185 Disable asynchronous mode.
5186 @kindex show target-async
5187 @item show target-async
5188 Show the current target-async setting.
5191 If the target doesn't support async mode, @value{GDBN} issues an error
5192 message if you attempt to use the background execution commands.
5194 To specify background execution, add a @code{&} to the command. For example,
5195 the background form of the @code{continue} command is @code{continue&}, or
5196 just @code{c&}. The execution commands that accept background execution
5202 @xref{Starting, , Starting your Program}.
5206 @xref{Attach, , Debugging an Already-running Process}.
5210 @xref{Continuing and Stepping, step}.
5214 @xref{Continuing and Stepping, stepi}.
5218 @xref{Continuing and Stepping, next}.
5222 @xref{Continuing and Stepping, nexti}.
5226 @xref{Continuing and Stepping, continue}.
5230 @xref{Continuing and Stepping, finish}.
5234 @xref{Continuing and Stepping, until}.
5238 Background execution is especially useful in conjunction with non-stop
5239 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5240 However, you can also use these commands in the normal all-stop mode with
5241 the restriction that you cannot issue another execution command until the
5242 previous one finishes. Examples of commands that are valid in all-stop
5243 mode while the program is running include @code{help} and @code{info break}.
5245 You can interrupt your program while it is running in the background by
5246 using the @code{interrupt} command.
5253 Suspend execution of the running program. In all-stop mode,
5254 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5255 only the current thread. To stop the whole program in non-stop mode,
5256 use @code{interrupt -a}.
5259 @node Thread-Specific Breakpoints
5260 @subsection Thread-Specific Breakpoints
5262 When your program has multiple threads (@pxref{Threads,, Debugging
5263 Programs with Multiple Threads}), you can choose whether to set
5264 breakpoints on all threads, or on a particular thread.
5267 @cindex breakpoints and threads
5268 @cindex thread breakpoints
5269 @kindex break @dots{} thread @var{threadno}
5270 @item break @var{linespec} thread @var{threadno}
5271 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5272 @var{linespec} specifies source lines; there are several ways of
5273 writing them (@pxref{Specify Location}), but the effect is always to
5274 specify some source line.
5276 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5277 to specify that you only want @value{GDBN} to stop the program when a
5278 particular thread reaches this breakpoint. @var{threadno} is one of the
5279 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5280 column of the @samp{info threads} display.
5282 If you do not specify @samp{thread @var{threadno}} when you set a
5283 breakpoint, the breakpoint applies to @emph{all} threads of your
5286 You can use the @code{thread} qualifier on conditional breakpoints as
5287 well; in this case, place @samp{thread @var{threadno}} before or
5288 after the breakpoint condition, like this:
5291 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5296 @node Interrupted System Calls
5297 @subsection Interrupted System Calls
5299 @cindex thread breakpoints and system calls
5300 @cindex system calls and thread breakpoints
5301 @cindex premature return from system calls
5302 There is an unfortunate side effect when using @value{GDBN} to debug
5303 multi-threaded programs. If one thread stops for a
5304 breakpoint, or for some other reason, and another thread is blocked in a
5305 system call, then the system call may return prematurely. This is a
5306 consequence of the interaction between multiple threads and the signals
5307 that @value{GDBN} uses to implement breakpoints and other events that
5310 To handle this problem, your program should check the return value of
5311 each system call and react appropriately. This is good programming
5314 For example, do not write code like this:
5320 The call to @code{sleep} will return early if a different thread stops
5321 at a breakpoint or for some other reason.
5323 Instead, write this:
5328 unslept = sleep (unslept);
5331 A system call is allowed to return early, so the system is still
5332 conforming to its specification. But @value{GDBN} does cause your
5333 multi-threaded program to behave differently than it would without
5336 Also, @value{GDBN} uses internal breakpoints in the thread library to
5337 monitor certain events such as thread creation and thread destruction.
5338 When such an event happens, a system call in another thread may return
5339 prematurely, even though your program does not appear to stop.
5342 @subsection Observer Mode
5344 If you want to build on non-stop mode and observe program behavior
5345 without any chance of disruption by @value{GDBN}, you can set
5346 variables to disable all of the debugger's attempts to modify state,
5347 whether by writing memory, inserting breakpoints, etc. These operate
5348 at a low level, intercepting operations from all commands.
5350 When all of these are set to @code{off}, then @value{GDBN} is said to
5351 be @dfn{observer mode}. As a convenience, the variable
5352 @code{observer} can be set to disable these, plus enable non-stop
5355 Note that @value{GDBN} will not prevent you from making nonsensical
5356 combinations of these settings. For instance, if you have enabled
5357 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5358 then breakpoints that work by writing trap instructions into the code
5359 stream will still not be able to be placed.
5364 @item set observer on
5365 @itemx set observer off
5366 When set to @code{on}, this disables all the permission variables
5367 below (except for @code{insert-fast-tracepoints}), plus enables
5368 non-stop debugging. Setting this to @code{off} switches back to
5369 normal debugging, though remaining in non-stop mode.
5372 Show whether observer mode is on or off.
5374 @kindex may-write-registers
5375 @item set may-write-registers on
5376 @itemx set may-write-registers off
5377 This controls whether @value{GDBN} will attempt to alter the values of
5378 registers, such as with assignment expressions in @code{print}, or the
5379 @code{jump} command. It defaults to @code{on}.
5381 @item show may-write-registers
5382 Show the current permission to write registers.
5384 @kindex may-write-memory
5385 @item set may-write-memory on
5386 @itemx set may-write-memory off
5387 This controls whether @value{GDBN} will attempt to alter the contents
5388 of memory, such as with assignment expressions in @code{print}. It
5389 defaults to @code{on}.
5391 @item show may-write-memory
5392 Show the current permission to write memory.
5394 @kindex may-insert-breakpoints
5395 @item set may-insert-breakpoints on
5396 @itemx set may-insert-breakpoints off
5397 This controls whether @value{GDBN} will attempt to insert breakpoints.
5398 This affects all breakpoints, including internal breakpoints defined
5399 by @value{GDBN}. It defaults to @code{on}.
5401 @item show may-insert-breakpoints
5402 Show the current permission to insert breakpoints.
5404 @kindex may-insert-tracepoints
5405 @item set may-insert-tracepoints on
5406 @itemx set may-insert-tracepoints off
5407 This controls whether @value{GDBN} will attempt to insert (regular)
5408 tracepoints at the beginning of a tracing experiment. It affects only
5409 non-fast tracepoints, fast tracepoints being under the control of
5410 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5412 @item show may-insert-tracepoints
5413 Show the current permission to insert tracepoints.
5415 @kindex may-insert-fast-tracepoints
5416 @item set may-insert-fast-tracepoints on
5417 @itemx set may-insert-fast-tracepoints off
5418 This controls whether @value{GDBN} will attempt to insert fast
5419 tracepoints at the beginning of a tracing experiment. It affects only
5420 fast tracepoints, regular (non-fast) tracepoints being under the
5421 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5423 @item show may-insert-fast-tracepoints
5424 Show the current permission to insert fast tracepoints.
5426 @kindex may-interrupt
5427 @item set may-interrupt on
5428 @itemx set may-interrupt off
5429 This controls whether @value{GDBN} will attempt to interrupt or stop
5430 program execution. When this variable is @code{off}, the
5431 @code{interrupt} command will have no effect, nor will
5432 @kbd{Ctrl-c}. It defaults to @code{on}.
5434 @item show may-interrupt
5435 Show the current permission to interrupt or stop the program.
5439 @node Reverse Execution
5440 @chapter Running programs backward
5441 @cindex reverse execution
5442 @cindex running programs backward
5444 When you are debugging a program, it is not unusual to realize that
5445 you have gone too far, and some event of interest has already happened.
5446 If the target environment supports it, @value{GDBN} can allow you to
5447 ``rewind'' the program by running it backward.
5449 A target environment that supports reverse execution should be able
5450 to ``undo'' the changes in machine state that have taken place as the
5451 program was executing normally. Variables, registers etc.@: should
5452 revert to their previous values. Obviously this requires a great
5453 deal of sophistication on the part of the target environment; not
5454 all target environments can support reverse execution.
5456 When a program is executed in reverse, the instructions that
5457 have most recently been executed are ``un-executed'', in reverse
5458 order. The program counter runs backward, following the previous
5459 thread of execution in reverse. As each instruction is ``un-executed'',
5460 the values of memory and/or registers that were changed by that
5461 instruction are reverted to their previous states. After executing
5462 a piece of source code in reverse, all side effects of that code
5463 should be ``undone'', and all variables should be returned to their
5464 prior values@footnote{
5465 Note that some side effects are easier to undo than others. For instance,
5466 memory and registers are relatively easy, but device I/O is hard. Some
5467 targets may be able undo things like device I/O, and some may not.
5469 The contract between @value{GDBN} and the reverse executing target
5470 requires only that the target do something reasonable when
5471 @value{GDBN} tells it to execute backwards, and then report the
5472 results back to @value{GDBN}. Whatever the target reports back to
5473 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5474 assumes that the memory and registers that the target reports are in a
5475 consistant state, but @value{GDBN} accepts whatever it is given.
5478 If you are debugging in a target environment that supports
5479 reverse execution, @value{GDBN} provides the following commands.
5482 @kindex reverse-continue
5483 @kindex rc @r{(@code{reverse-continue})}
5484 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5485 @itemx rc @r{[}@var{ignore-count}@r{]}
5486 Beginning at the point where your program last stopped, start executing
5487 in reverse. Reverse execution will stop for breakpoints and synchronous
5488 exceptions (signals), just like normal execution. Behavior of
5489 asynchronous signals depends on the target environment.
5491 @kindex reverse-step
5492 @kindex rs @r{(@code{step})}
5493 @item reverse-step @r{[}@var{count}@r{]}
5494 Run the program backward until control reaches the start of a
5495 different source line; then stop it, and return control to @value{GDBN}.
5497 Like the @code{step} command, @code{reverse-step} will only stop
5498 at the beginning of a source line. It ``un-executes'' the previously
5499 executed source line. If the previous source line included calls to
5500 debuggable functions, @code{reverse-step} will step (backward) into
5501 the called function, stopping at the beginning of the @emph{last}
5502 statement in the called function (typically a return statement).
5504 Also, as with the @code{step} command, if non-debuggable functions are
5505 called, @code{reverse-step} will run thru them backward without stopping.
5507 @kindex reverse-stepi
5508 @kindex rsi @r{(@code{reverse-stepi})}
5509 @item reverse-stepi @r{[}@var{count}@r{]}
5510 Reverse-execute one machine instruction. Note that the instruction
5511 to be reverse-executed is @emph{not} the one pointed to by the program
5512 counter, but the instruction executed prior to that one. For instance,
5513 if the last instruction was a jump, @code{reverse-stepi} will take you
5514 back from the destination of the jump to the jump instruction itself.
5516 @kindex reverse-next
5517 @kindex rn @r{(@code{reverse-next})}
5518 @item reverse-next @r{[}@var{count}@r{]}
5519 Run backward to the beginning of the previous line executed in
5520 the current (innermost) stack frame. If the line contains function
5521 calls, they will be ``un-executed'' without stopping. Starting from
5522 the first line of a function, @code{reverse-next} will take you back
5523 to the caller of that function, @emph{before} the function was called,
5524 just as the normal @code{next} command would take you from the last
5525 line of a function back to its return to its caller
5526 @footnote{Unless the code is too heavily optimized.}.
5528 @kindex reverse-nexti
5529 @kindex rni @r{(@code{reverse-nexti})}
5530 @item reverse-nexti @r{[}@var{count}@r{]}
5531 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5532 in reverse, except that called functions are ``un-executed'' atomically.
5533 That is, if the previously executed instruction was a return from
5534 another function, @code{reverse-nexti} will continue to execute
5535 in reverse until the call to that function (from the current stack
5538 @kindex reverse-finish
5539 @item reverse-finish
5540 Just as the @code{finish} command takes you to the point where the
5541 current function returns, @code{reverse-finish} takes you to the point
5542 where it was called. Instead of ending up at the end of the current
5543 function invocation, you end up at the beginning.
5545 @kindex set exec-direction
5546 @item set exec-direction
5547 Set the direction of target execution.
5548 @itemx set exec-direction reverse
5549 @cindex execute forward or backward in time
5550 @value{GDBN} will perform all execution commands in reverse, until the
5551 exec-direction mode is changed to ``forward''. Affected commands include
5552 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5553 command cannot be used in reverse mode.
5554 @item set exec-direction forward
5555 @value{GDBN} will perform all execution commands in the normal fashion.
5556 This is the default.
5560 @node Process Record and Replay
5561 @chapter Recording Inferior's Execution and Replaying It
5562 @cindex process record and replay
5563 @cindex recording inferior's execution and replaying it
5565 On some platforms, @value{GDBN} provides a special @dfn{process record
5566 and replay} target that can record a log of the process execution, and
5567 replay it later with both forward and reverse execution commands.
5570 When this target is in use, if the execution log includes the record
5571 for the next instruction, @value{GDBN} will debug in @dfn{replay
5572 mode}. In the replay mode, the inferior does not really execute code
5573 instructions. Instead, all the events that normally happen during
5574 code execution are taken from the execution log. While code is not
5575 really executed in replay mode, the values of registers (including the
5576 program counter register) and the memory of the inferior are still
5577 changed as they normally would. Their contents are taken from the
5581 If the record for the next instruction is not in the execution log,
5582 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5583 inferior executes normally, and @value{GDBN} records the execution log
5586 The process record and replay target supports reverse execution
5587 (@pxref{Reverse Execution}), even if the platform on which the
5588 inferior runs does not. However, the reverse execution is limited in
5589 this case by the range of the instructions recorded in the execution
5590 log. In other words, reverse execution on platforms that don't
5591 support it directly can only be done in the replay mode.
5593 When debugging in the reverse direction, @value{GDBN} will work in
5594 replay mode as long as the execution log includes the record for the
5595 previous instruction; otherwise, it will work in record mode, if the
5596 platform supports reverse execution, or stop if not.
5598 For architecture environments that support process record and replay,
5599 @value{GDBN} provides the following commands:
5602 @kindex target record
5606 This command starts the process record and replay target. The process
5607 record and replay target can only debug a process that is already
5608 running. Therefore, you need first to start the process with the
5609 @kbd{run} or @kbd{start} commands, and then start the recording with
5610 the @kbd{target record} command.
5612 Both @code{record} and @code{rec} are aliases of @code{target record}.
5614 @cindex displaced stepping, and process record and replay
5615 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5616 will be automatically disabled when process record and replay target
5617 is started. That's because the process record and replay target
5618 doesn't support displaced stepping.
5620 @cindex non-stop mode, and process record and replay
5621 @cindex asynchronous execution, and process record and replay
5622 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5623 the asynchronous execution mode (@pxref{Background Execution}), the
5624 process record and replay target cannot be started because it doesn't
5625 support these two modes.
5630 Stop the process record and replay target. When process record and
5631 replay target stops, the entire execution log will be deleted and the
5632 inferior will either be terminated, or will remain in its final state.
5634 When you stop the process record and replay target in record mode (at
5635 the end of the execution log), the inferior will be stopped at the
5636 next instruction that would have been recorded. In other words, if
5637 you record for a while and then stop recording, the inferior process
5638 will be left in the same state as if the recording never happened.
5640 On the other hand, if the process record and replay target is stopped
5641 while in replay mode (that is, not at the end of the execution log,
5642 but at some earlier point), the inferior process will become ``live''
5643 at that earlier state, and it will then be possible to continue the
5644 usual ``live'' debugging of the process from that state.
5646 When the inferior process exits, or @value{GDBN} detaches from it,
5647 process record and replay target will automatically stop itself.
5650 @item record save @var{filename}
5651 Save the execution log to a file @file{@var{filename}}.
5652 Default filename is @file{gdb_record.@var{process_id}}, where
5653 @var{process_id} is the process ID of the inferior.
5655 @kindex record restore
5656 @item record restore @var{filename}
5657 Restore the execution log from a file @file{@var{filename}}.
5658 File must have been created with @code{record save}.
5660 @kindex set record insn-number-max
5661 @item set record insn-number-max @var{limit}
5662 Set the limit of instructions to be recorded. Default value is 200000.
5664 If @var{limit} is a positive number, then @value{GDBN} will start
5665 deleting instructions from the log once the number of the record
5666 instructions becomes greater than @var{limit}. For every new recorded
5667 instruction, @value{GDBN} will delete the earliest recorded
5668 instruction to keep the number of recorded instructions at the limit.
5669 (Since deleting recorded instructions loses information, @value{GDBN}
5670 lets you control what happens when the limit is reached, by means of
5671 the @code{stop-at-limit} option, described below.)
5673 If @var{limit} is zero, @value{GDBN} will never delete recorded
5674 instructions from the execution log. The number of recorded
5675 instructions is unlimited in this case.
5677 @kindex show record insn-number-max
5678 @item show record insn-number-max
5679 Show the limit of instructions to be recorded.
5681 @kindex set record stop-at-limit
5682 @item set record stop-at-limit
5683 Control the behavior when the number of recorded instructions reaches
5684 the limit. If ON (the default), @value{GDBN} will stop when the limit
5685 is reached for the first time and ask you whether you want to stop the
5686 inferior or continue running it and recording the execution log. If
5687 you decide to continue recording, each new recorded instruction will
5688 cause the oldest one to be deleted.
5690 If this option is OFF, @value{GDBN} will automatically delete the
5691 oldest record to make room for each new one, without asking.
5693 @kindex show record stop-at-limit
5694 @item show record stop-at-limit
5695 Show the current setting of @code{stop-at-limit}.
5697 @kindex set record memory-query
5698 @item set record memory-query
5699 Control the behavior when @value{GDBN} is unable to record memory
5700 changes caused by an instruction. If ON, @value{GDBN} will query
5701 whether to stop the inferior in that case.
5703 If this option is OFF (the default), @value{GDBN} will automatically
5704 ignore the effect of such instructions on memory. Later, when
5705 @value{GDBN} replays this execution log, it will mark the log of this
5706 instruction as not accessible, and it will not affect the replay
5709 @kindex show record memory-query
5710 @item show record memory-query
5711 Show the current setting of @code{memory-query}.
5715 Show various statistics about the state of process record and its
5716 in-memory execution log buffer, including:
5720 Whether in record mode or replay mode.
5722 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5724 Highest recorded instruction number.
5726 Current instruction about to be replayed (if in replay mode).
5728 Number of instructions contained in the execution log.
5730 Maximum number of instructions that may be contained in the execution log.
5733 @kindex record delete
5736 When record target runs in replay mode (``in the past''), delete the
5737 subsequent execution log and begin to record a new execution log starting
5738 from the current address. This means you will abandon the previously
5739 recorded ``future'' and begin recording a new ``future''.
5744 @chapter Examining the Stack
5746 When your program has stopped, the first thing you need to know is where it
5747 stopped and how it got there.
5750 Each time your program performs a function call, information about the call
5752 That information includes the location of the call in your program,
5753 the arguments of the call,
5754 and the local variables of the function being called.
5755 The information is saved in a block of data called a @dfn{stack frame}.
5756 The stack frames are allocated in a region of memory called the @dfn{call
5759 When your program stops, the @value{GDBN} commands for examining the
5760 stack allow you to see all of this information.
5762 @cindex selected frame
5763 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5764 @value{GDBN} commands refer implicitly to the selected frame. In
5765 particular, whenever you ask @value{GDBN} for the value of a variable in
5766 your program, the value is found in the selected frame. There are
5767 special @value{GDBN} commands to select whichever frame you are
5768 interested in. @xref{Selection, ,Selecting a Frame}.
5770 When your program stops, @value{GDBN} automatically selects the
5771 currently executing frame and describes it briefly, similar to the
5772 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5775 * Frames:: Stack frames
5776 * Backtrace:: Backtraces
5777 * Selection:: Selecting a frame
5778 * Frame Info:: Information on a frame
5783 @section Stack Frames
5785 @cindex frame, definition
5787 The call stack is divided up into contiguous pieces called @dfn{stack
5788 frames}, or @dfn{frames} for short; each frame is the data associated
5789 with one call to one function. The frame contains the arguments given
5790 to the function, the function's local variables, and the address at
5791 which the function is executing.
5793 @cindex initial frame
5794 @cindex outermost frame
5795 @cindex innermost frame
5796 When your program is started, the stack has only one frame, that of the
5797 function @code{main}. This is called the @dfn{initial} frame or the
5798 @dfn{outermost} frame. Each time a function is called, a new frame is
5799 made. Each time a function returns, the frame for that function invocation
5800 is eliminated. If a function is recursive, there can be many frames for
5801 the same function. The frame for the function in which execution is
5802 actually occurring is called the @dfn{innermost} frame. This is the most
5803 recently created of all the stack frames that still exist.
5805 @cindex frame pointer
5806 Inside your program, stack frames are identified by their addresses. A
5807 stack frame consists of many bytes, each of which has its own address; each
5808 kind of computer has a convention for choosing one byte whose
5809 address serves as the address of the frame. Usually this address is kept
5810 in a register called the @dfn{frame pointer register}
5811 (@pxref{Registers, $fp}) while execution is going on in that frame.
5813 @cindex frame number
5814 @value{GDBN} assigns numbers to all existing stack frames, starting with
5815 zero for the innermost frame, one for the frame that called it,
5816 and so on upward. These numbers do not really exist in your program;
5817 they are assigned by @value{GDBN} to give you a way of designating stack
5818 frames in @value{GDBN} commands.
5820 @c The -fomit-frame-pointer below perennially causes hbox overflow
5821 @c underflow problems.
5822 @cindex frameless execution
5823 Some compilers provide a way to compile functions so that they operate
5824 without stack frames. (For example, the @value{NGCC} option
5826 @samp{-fomit-frame-pointer}
5828 generates functions without a frame.)
5829 This is occasionally done with heavily used library functions to save
5830 the frame setup time. @value{GDBN} has limited facilities for dealing
5831 with these function invocations. If the innermost function invocation
5832 has no stack frame, @value{GDBN} nevertheless regards it as though
5833 it had a separate frame, which is numbered zero as usual, allowing
5834 correct tracing of the function call chain. However, @value{GDBN} has
5835 no provision for frameless functions elsewhere in the stack.
5838 @kindex frame@r{, command}
5839 @cindex current stack frame
5840 @item frame @var{args}
5841 The @code{frame} command allows you to move from one stack frame to another,
5842 and to print the stack frame you select. @var{args} may be either the
5843 address of the frame or the stack frame number. Without an argument,
5844 @code{frame} prints the current stack frame.
5846 @kindex select-frame
5847 @cindex selecting frame silently
5849 The @code{select-frame} command allows you to move from one stack frame
5850 to another without printing the frame. This is the silent version of
5858 @cindex call stack traces
5859 A backtrace is a summary of how your program got where it is. It shows one
5860 line per frame, for many frames, starting with the currently executing
5861 frame (frame zero), followed by its caller (frame one), and on up the
5866 @kindex bt @r{(@code{backtrace})}
5869 Print a backtrace of the entire stack: one line per frame for all
5870 frames in the stack.
5872 You can stop the backtrace at any time by typing the system interrupt
5873 character, normally @kbd{Ctrl-c}.
5875 @item backtrace @var{n}
5877 Similar, but print only the innermost @var{n} frames.
5879 @item backtrace -@var{n}
5881 Similar, but print only the outermost @var{n} frames.
5883 @item backtrace full
5885 @itemx bt full @var{n}
5886 @itemx bt full -@var{n}
5887 Print the values of the local variables also. @var{n} specifies the
5888 number of frames to print, as described above.
5893 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5894 are additional aliases for @code{backtrace}.
5896 @cindex multiple threads, backtrace
5897 In a multi-threaded program, @value{GDBN} by default shows the
5898 backtrace only for the current thread. To display the backtrace for
5899 several or all of the threads, use the command @code{thread apply}
5900 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5901 apply all backtrace}, @value{GDBN} will display the backtrace for all
5902 the threads; this is handy when you debug a core dump of a
5903 multi-threaded program.
5905 Each line in the backtrace shows the frame number and the function name.
5906 The program counter value is also shown---unless you use @code{set
5907 print address off}. The backtrace also shows the source file name and
5908 line number, as well as the arguments to the function. The program
5909 counter value is omitted if it is at the beginning of the code for that
5912 Here is an example of a backtrace. It was made with the command
5913 @samp{bt 3}, so it shows the innermost three frames.
5917 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5919 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5920 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5922 (More stack frames follow...)
5927 The display for frame zero does not begin with a program counter
5928 value, indicating that your program has stopped at the beginning of the
5929 code for line @code{993} of @code{builtin.c}.
5932 The value of parameter @code{data} in frame 1 has been replaced by
5933 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5934 only if it is a scalar (integer, pointer, enumeration, etc). See command
5935 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5936 on how to configure the way function parameter values are printed.
5938 @cindex value optimized out, in backtrace
5939 @cindex function call arguments, optimized out
5940 If your program was compiled with optimizations, some compilers will
5941 optimize away arguments passed to functions if those arguments are
5942 never used after the call. Such optimizations generate code that
5943 passes arguments through registers, but doesn't store those arguments
5944 in the stack frame. @value{GDBN} has no way of displaying such
5945 arguments in stack frames other than the innermost one. Here's what
5946 such a backtrace might look like:
5950 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5952 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5953 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5955 (More stack frames follow...)
5960 The values of arguments that were not saved in their stack frames are
5961 shown as @samp{<value optimized out>}.
5963 If you need to display the values of such optimized-out arguments,
5964 either deduce that from other variables whose values depend on the one
5965 you are interested in, or recompile without optimizations.
5967 @cindex backtrace beyond @code{main} function
5968 @cindex program entry point
5969 @cindex startup code, and backtrace
5970 Most programs have a standard user entry point---a place where system
5971 libraries and startup code transition into user code. For C this is
5972 @code{main}@footnote{
5973 Note that embedded programs (the so-called ``free-standing''
5974 environment) are not required to have a @code{main} function as the
5975 entry point. They could even have multiple entry points.}.
5976 When @value{GDBN} finds the entry function in a backtrace
5977 it will terminate the backtrace, to avoid tracing into highly
5978 system-specific (and generally uninteresting) code.
5980 If you need to examine the startup code, or limit the number of levels
5981 in a backtrace, you can change this behavior:
5984 @item set backtrace past-main
5985 @itemx set backtrace past-main on
5986 @kindex set backtrace
5987 Backtraces will continue past the user entry point.
5989 @item set backtrace past-main off
5990 Backtraces will stop when they encounter the user entry point. This is the
5993 @item show backtrace past-main
5994 @kindex show backtrace
5995 Display the current user entry point backtrace policy.
5997 @item set backtrace past-entry
5998 @itemx set backtrace past-entry on
5999 Backtraces will continue past the internal entry point of an application.
6000 This entry point is encoded by the linker when the application is built,
6001 and is likely before the user entry point @code{main} (or equivalent) is called.
6003 @item set backtrace past-entry off
6004 Backtraces will stop when they encounter the internal entry point of an
6005 application. This is the default.
6007 @item show backtrace past-entry
6008 Display the current internal entry point backtrace policy.
6010 @item set backtrace limit @var{n}
6011 @itemx set backtrace limit 0
6012 @cindex backtrace limit
6013 Limit the backtrace to @var{n} levels. A value of zero means
6016 @item show backtrace limit
6017 Display the current limit on backtrace levels.
6021 @section Selecting a Frame
6023 Most commands for examining the stack and other data in your program work on
6024 whichever stack frame is selected at the moment. Here are the commands for
6025 selecting a stack frame; all of them finish by printing a brief description
6026 of the stack frame just selected.
6029 @kindex frame@r{, selecting}
6030 @kindex f @r{(@code{frame})}
6033 Select frame number @var{n}. Recall that frame zero is the innermost
6034 (currently executing) frame, frame one is the frame that called the
6035 innermost one, and so on. The highest-numbered frame is the one for
6038 @item frame @var{addr}
6040 Select the frame at address @var{addr}. This is useful mainly if the
6041 chaining of stack frames has been damaged by a bug, making it
6042 impossible for @value{GDBN} to assign numbers properly to all frames. In
6043 addition, this can be useful when your program has multiple stacks and
6044 switches between them.
6046 On the SPARC architecture, @code{frame} needs two addresses to
6047 select an arbitrary frame: a frame pointer and a stack pointer.
6049 On the MIPS and Alpha architecture, it needs two addresses: a stack
6050 pointer and a program counter.
6052 On the 29k architecture, it needs three addresses: a register stack
6053 pointer, a program counter, and a memory stack pointer.
6057 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6058 advances toward the outermost frame, to higher frame numbers, to frames
6059 that have existed longer. @var{n} defaults to one.
6062 @kindex do @r{(@code{down})}
6064 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6065 advances toward the innermost frame, to lower frame numbers, to frames
6066 that were created more recently. @var{n} defaults to one. You may
6067 abbreviate @code{down} as @code{do}.
6070 All of these commands end by printing two lines of output describing the
6071 frame. The first line shows the frame number, the function name, the
6072 arguments, and the source file and line number of execution in that
6073 frame. The second line shows the text of that source line.
6081 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6083 10 read_input_file (argv[i]);
6087 After such a printout, the @code{list} command with no arguments
6088 prints ten lines centered on the point of execution in the frame.
6089 You can also edit the program at the point of execution with your favorite
6090 editing program by typing @code{edit}.
6091 @xref{List, ,Printing Source Lines},
6095 @kindex down-silently
6097 @item up-silently @var{n}
6098 @itemx down-silently @var{n}
6099 These two commands are variants of @code{up} and @code{down},
6100 respectively; they differ in that they do their work silently, without
6101 causing display of the new frame. They are intended primarily for use
6102 in @value{GDBN} command scripts, where the output might be unnecessary and
6107 @section Information About a Frame
6109 There are several other commands to print information about the selected
6115 When used without any argument, this command does not change which
6116 frame is selected, but prints a brief description of the currently
6117 selected stack frame. It can be abbreviated @code{f}. With an
6118 argument, this command is used to select a stack frame.
6119 @xref{Selection, ,Selecting a Frame}.
6122 @kindex info f @r{(@code{info frame})}
6125 This command prints a verbose description of the selected stack frame,
6130 the address of the frame
6132 the address of the next frame down (called by this frame)
6134 the address of the next frame up (caller of this frame)
6136 the language in which the source code corresponding to this frame is written
6138 the address of the frame's arguments
6140 the address of the frame's local variables
6142 the program counter saved in it (the address of execution in the caller frame)
6144 which registers were saved in the frame
6147 @noindent The verbose description is useful when
6148 something has gone wrong that has made the stack format fail to fit
6149 the usual conventions.
6151 @item info frame @var{addr}
6152 @itemx info f @var{addr}
6153 Print a verbose description of the frame at address @var{addr}, without
6154 selecting that frame. The selected frame remains unchanged by this
6155 command. This requires the same kind of address (more than one for some
6156 architectures) that you specify in the @code{frame} command.
6157 @xref{Selection, ,Selecting a Frame}.
6161 Print the arguments of the selected frame, each on a separate line.
6165 Print the local variables of the selected frame, each on a separate
6166 line. These are all variables (declared either static or automatic)
6167 accessible at the point of execution of the selected frame.
6170 @cindex catch exceptions, list active handlers
6171 @cindex exception handlers, how to list
6173 Print a list of all the exception handlers that are active in the
6174 current stack frame at the current point of execution. To see other
6175 exception handlers, visit the associated frame (using the @code{up},
6176 @code{down}, or @code{frame} commands); then type @code{info catch}.
6177 @xref{Set Catchpoints, , Setting Catchpoints}.
6183 @chapter Examining Source Files
6185 @value{GDBN} can print parts of your program's source, since the debugging
6186 information recorded in the program tells @value{GDBN} what source files were
6187 used to build it. When your program stops, @value{GDBN} spontaneously prints
6188 the line where it stopped. Likewise, when you select a stack frame
6189 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6190 execution in that frame has stopped. You can print other portions of
6191 source files by explicit command.
6193 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6194 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6195 @value{GDBN} under @sc{gnu} Emacs}.
6198 * List:: Printing source lines
6199 * Specify Location:: How to specify code locations
6200 * Edit:: Editing source files
6201 * Search:: Searching source files
6202 * Source Path:: Specifying source directories
6203 * Machine Code:: Source and machine code
6207 @section Printing Source Lines
6210 @kindex l @r{(@code{list})}
6211 To print lines from a source file, use the @code{list} command
6212 (abbreviated @code{l}). By default, ten lines are printed.
6213 There are several ways to specify what part of the file you want to
6214 print; see @ref{Specify Location}, for the full list.
6216 Here are the forms of the @code{list} command most commonly used:
6219 @item list @var{linenum}
6220 Print lines centered around line number @var{linenum} in the
6221 current source file.
6223 @item list @var{function}
6224 Print lines centered around the beginning of function
6228 Print more lines. If the last lines printed were printed with a
6229 @code{list} command, this prints lines following the last lines
6230 printed; however, if the last line printed was a solitary line printed
6231 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6232 Stack}), this prints lines centered around that line.
6235 Print lines just before the lines last printed.
6238 @cindex @code{list}, how many lines to display
6239 By default, @value{GDBN} prints ten source lines with any of these forms of
6240 the @code{list} command. You can change this using @code{set listsize}:
6243 @kindex set listsize
6244 @item set listsize @var{count}
6245 Make the @code{list} command display @var{count} source lines (unless
6246 the @code{list} argument explicitly specifies some other number).
6248 @kindex show listsize
6250 Display the number of lines that @code{list} prints.
6253 Repeating a @code{list} command with @key{RET} discards the argument,
6254 so it is equivalent to typing just @code{list}. This is more useful
6255 than listing the same lines again. An exception is made for an
6256 argument of @samp{-}; that argument is preserved in repetition so that
6257 each repetition moves up in the source file.
6259 In general, the @code{list} command expects you to supply zero, one or two
6260 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6261 of writing them (@pxref{Specify Location}), but the effect is always
6262 to specify some source line.
6264 Here is a complete description of the possible arguments for @code{list}:
6267 @item list @var{linespec}
6268 Print lines centered around the line specified by @var{linespec}.
6270 @item list @var{first},@var{last}
6271 Print lines from @var{first} to @var{last}. Both arguments are
6272 linespecs. When a @code{list} command has two linespecs, and the
6273 source file of the second linespec is omitted, this refers to
6274 the same source file as the first linespec.
6276 @item list ,@var{last}
6277 Print lines ending with @var{last}.
6279 @item list @var{first},
6280 Print lines starting with @var{first}.
6283 Print lines just after the lines last printed.
6286 Print lines just before the lines last printed.
6289 As described in the preceding table.
6292 @node Specify Location
6293 @section Specifying a Location
6294 @cindex specifying location
6297 Several @value{GDBN} commands accept arguments that specify a location
6298 of your program's code. Since @value{GDBN} is a source-level
6299 debugger, a location usually specifies some line in the source code;
6300 for that reason, locations are also known as @dfn{linespecs}.
6302 Here are all the different ways of specifying a code location that
6303 @value{GDBN} understands:
6307 Specifies the line number @var{linenum} of the current source file.
6310 @itemx +@var{offset}
6311 Specifies the line @var{offset} lines before or after the @dfn{current
6312 line}. For the @code{list} command, the current line is the last one
6313 printed; for the breakpoint commands, this is the line at which
6314 execution stopped in the currently selected @dfn{stack frame}
6315 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6316 used as the second of the two linespecs in a @code{list} command,
6317 this specifies the line @var{offset} lines up or down from the first
6320 @item @var{filename}:@var{linenum}
6321 Specifies the line @var{linenum} in the source file @var{filename}.
6323 @item @var{function}
6324 Specifies the line that begins the body of the function @var{function}.
6325 For example, in C, this is the line with the open brace.
6327 @item @var{filename}:@var{function}
6328 Specifies the line that begins the body of the function @var{function}
6329 in the file @var{filename}. You only need the file name with a
6330 function name to avoid ambiguity when there are identically named
6331 functions in different source files.
6333 @item *@var{address}
6334 Specifies the program address @var{address}. For line-oriented
6335 commands, such as @code{list} and @code{edit}, this specifies a source
6336 line that contains @var{address}. For @code{break} and other
6337 breakpoint oriented commands, this can be used to set breakpoints in
6338 parts of your program which do not have debugging information or
6341 Here @var{address} may be any expression valid in the current working
6342 language (@pxref{Languages, working language}) that specifies a code
6343 address. In addition, as a convenience, @value{GDBN} extends the
6344 semantics of expressions used in locations to cover the situations
6345 that frequently happen during debugging. Here are the various forms
6349 @item @var{expression}
6350 Any expression valid in the current working language.
6352 @item @var{funcaddr}
6353 An address of a function or procedure derived from its name. In C,
6354 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6355 simply the function's name @var{function} (and actually a special case
6356 of a valid expression). In Pascal and Modula-2, this is
6357 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6358 (although the Pascal form also works).
6360 This form specifies the address of the function's first instruction,
6361 before the stack frame and arguments have been set up.
6363 @item '@var{filename}'::@var{funcaddr}
6364 Like @var{funcaddr} above, but also specifies the name of the source
6365 file explicitly. This is useful if the name of the function does not
6366 specify the function unambiguously, e.g., if there are several
6367 functions with identical names in different source files.
6374 @section Editing Source Files
6375 @cindex editing source files
6378 @kindex e @r{(@code{edit})}
6379 To edit the lines in a source file, use the @code{edit} command.
6380 The editing program of your choice
6381 is invoked with the current line set to
6382 the active line in the program.
6383 Alternatively, there are several ways to specify what part of the file you
6384 want to print if you want to see other parts of the program:
6387 @item edit @var{location}
6388 Edit the source file specified by @code{location}. Editing starts at
6389 that @var{location}, e.g., at the specified source line of the
6390 specified file. @xref{Specify Location}, for all the possible forms
6391 of the @var{location} argument; here are the forms of the @code{edit}
6392 command most commonly used:
6395 @item edit @var{number}
6396 Edit the current source file with @var{number} as the active line number.
6398 @item edit @var{function}
6399 Edit the file containing @var{function} at the beginning of its definition.
6404 @subsection Choosing your Editor
6405 You can customize @value{GDBN} to use any editor you want
6407 The only restriction is that your editor (say @code{ex}), recognizes the
6408 following command-line syntax:
6410 ex +@var{number} file
6412 The optional numeric value +@var{number} specifies the number of the line in
6413 the file where to start editing.}.
6414 By default, it is @file{@value{EDITOR}}, but you can change this
6415 by setting the environment variable @code{EDITOR} before using
6416 @value{GDBN}. For example, to configure @value{GDBN} to use the
6417 @code{vi} editor, you could use these commands with the @code{sh} shell:
6423 or in the @code{csh} shell,
6425 setenv EDITOR /usr/bin/vi
6430 @section Searching Source Files
6431 @cindex searching source files
6433 There are two commands for searching through the current source file for a
6438 @kindex forward-search
6439 @item forward-search @var{regexp}
6440 @itemx search @var{regexp}
6441 The command @samp{forward-search @var{regexp}} checks each line,
6442 starting with the one following the last line listed, for a match for
6443 @var{regexp}. It lists the line that is found. You can use the
6444 synonym @samp{search @var{regexp}} or abbreviate the command name as
6447 @kindex reverse-search
6448 @item reverse-search @var{regexp}
6449 The command @samp{reverse-search @var{regexp}} checks each line, starting
6450 with the one before the last line listed and going backward, for a match
6451 for @var{regexp}. It lists the line that is found. You can abbreviate
6452 this command as @code{rev}.
6456 @section Specifying Source Directories
6459 @cindex directories for source files
6460 Executable programs sometimes do not record the directories of the source
6461 files from which they were compiled, just the names. Even when they do,
6462 the directories could be moved between the compilation and your debugging
6463 session. @value{GDBN} has a list of directories to search for source files;
6464 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6465 it tries all the directories in the list, in the order they are present
6466 in the list, until it finds a file with the desired name.
6468 For example, suppose an executable references the file
6469 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6470 @file{/mnt/cross}. The file is first looked up literally; if this
6471 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6472 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6473 message is printed. @value{GDBN} does not look up the parts of the
6474 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6475 Likewise, the subdirectories of the source path are not searched: if
6476 the source path is @file{/mnt/cross}, and the binary refers to
6477 @file{foo.c}, @value{GDBN} would not find it under
6478 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6480 Plain file names, relative file names with leading directories, file
6481 names containing dots, etc.@: are all treated as described above; for
6482 instance, if the source path is @file{/mnt/cross}, and the source file
6483 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6484 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6485 that---@file{/mnt/cross/foo.c}.
6487 Note that the executable search path is @emph{not} used to locate the
6490 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6491 any information it has cached about where source files are found and where
6492 each line is in the file.
6496 When you start @value{GDBN}, its source path includes only @samp{cdir}
6497 and @samp{cwd}, in that order.
6498 To add other directories, use the @code{directory} command.
6500 The search path is used to find both program source files and @value{GDBN}
6501 script files (read using the @samp{-command} option and @samp{source} command).
6503 In addition to the source path, @value{GDBN} provides a set of commands
6504 that manage a list of source path substitution rules. A @dfn{substitution
6505 rule} specifies how to rewrite source directories stored in the program's
6506 debug information in case the sources were moved to a different
6507 directory between compilation and debugging. A rule is made of
6508 two strings, the first specifying what needs to be rewritten in
6509 the path, and the second specifying how it should be rewritten.
6510 In @ref{set substitute-path}, we name these two parts @var{from} and
6511 @var{to} respectively. @value{GDBN} does a simple string replacement
6512 of @var{from} with @var{to} at the start of the directory part of the
6513 source file name, and uses that result instead of the original file
6514 name to look up the sources.
6516 Using the previous example, suppose the @file{foo-1.0} tree has been
6517 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6518 @value{GDBN} to replace @file{/usr/src} in all source path names with
6519 @file{/mnt/cross}. The first lookup will then be
6520 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6521 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6522 substitution rule, use the @code{set substitute-path} command
6523 (@pxref{set substitute-path}).
6525 To avoid unexpected substitution results, a rule is applied only if the
6526 @var{from} part of the directory name ends at a directory separator.
6527 For instance, a rule substituting @file{/usr/source} into
6528 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6529 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6530 is applied only at the beginning of the directory name, this rule will
6531 not be applied to @file{/root/usr/source/baz.c} either.
6533 In many cases, you can achieve the same result using the @code{directory}
6534 command. However, @code{set substitute-path} can be more efficient in
6535 the case where the sources are organized in a complex tree with multiple
6536 subdirectories. With the @code{directory} command, you need to add each
6537 subdirectory of your project. If you moved the entire tree while
6538 preserving its internal organization, then @code{set substitute-path}
6539 allows you to direct the debugger to all the sources with one single
6542 @code{set substitute-path} is also more than just a shortcut command.
6543 The source path is only used if the file at the original location no
6544 longer exists. On the other hand, @code{set substitute-path} modifies
6545 the debugger behavior to look at the rewritten location instead. So, if
6546 for any reason a source file that is not relevant to your executable is
6547 located at the original location, a substitution rule is the only
6548 method available to point @value{GDBN} at the new location.
6550 @cindex @samp{--with-relocated-sources}
6551 @cindex default source path substitution
6552 You can configure a default source path substitution rule by
6553 configuring @value{GDBN} with the
6554 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6555 should be the name of a directory under @value{GDBN}'s configured
6556 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6557 directory names in debug information under @var{dir} will be adjusted
6558 automatically if the installed @value{GDBN} is moved to a new
6559 location. This is useful if @value{GDBN}, libraries or executables
6560 with debug information and corresponding source code are being moved
6564 @item directory @var{dirname} @dots{}
6565 @item dir @var{dirname} @dots{}
6566 Add directory @var{dirname} to the front of the source path. Several
6567 directory names may be given to this command, separated by @samp{:}
6568 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6569 part of absolute file names) or
6570 whitespace. You may specify a directory that is already in the source
6571 path; this moves it forward, so @value{GDBN} searches it sooner.
6575 @vindex $cdir@r{, convenience variable}
6576 @vindex $cwd@r{, convenience variable}
6577 @cindex compilation directory
6578 @cindex current directory
6579 @cindex working directory
6580 @cindex directory, current
6581 @cindex directory, compilation
6582 You can use the string @samp{$cdir} to refer to the compilation
6583 directory (if one is recorded), and @samp{$cwd} to refer to the current
6584 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6585 tracks the current working directory as it changes during your @value{GDBN}
6586 session, while the latter is immediately expanded to the current
6587 directory at the time you add an entry to the source path.
6590 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6592 @c RET-repeat for @code{directory} is explicitly disabled, but since
6593 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6595 @item show directories
6596 @kindex show directories
6597 Print the source path: show which directories it contains.
6599 @anchor{set substitute-path}
6600 @item set substitute-path @var{from} @var{to}
6601 @kindex set substitute-path
6602 Define a source path substitution rule, and add it at the end of the
6603 current list of existing substitution rules. If a rule with the same
6604 @var{from} was already defined, then the old rule is also deleted.
6606 For example, if the file @file{/foo/bar/baz.c} was moved to
6607 @file{/mnt/cross/baz.c}, then the command
6610 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6614 will tell @value{GDBN} to replace @samp{/usr/src} with
6615 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6616 @file{baz.c} even though it was moved.
6618 In the case when more than one substitution rule have been defined,
6619 the rules are evaluated one by one in the order where they have been
6620 defined. The first one matching, if any, is selected to perform
6623 For instance, if we had entered the following commands:
6626 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6627 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6631 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6632 @file{/mnt/include/defs.h} by using the first rule. However, it would
6633 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6634 @file{/mnt/src/lib/foo.c}.
6637 @item unset substitute-path [path]
6638 @kindex unset substitute-path
6639 If a path is specified, search the current list of substitution rules
6640 for a rule that would rewrite that path. Delete that rule if found.
6641 A warning is emitted by the debugger if no rule could be found.
6643 If no path is specified, then all substitution rules are deleted.
6645 @item show substitute-path [path]
6646 @kindex show substitute-path
6647 If a path is specified, then print the source path substitution rule
6648 which would rewrite that path, if any.
6650 If no path is specified, then print all existing source path substitution
6655 If your source path is cluttered with directories that are no longer of
6656 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6657 versions of source. You can correct the situation as follows:
6661 Use @code{directory} with no argument to reset the source path to its default value.
6664 Use @code{directory} with suitable arguments to reinstall the
6665 directories you want in the source path. You can add all the
6666 directories in one command.
6670 @section Source and Machine Code
6671 @cindex source line and its code address
6673 You can use the command @code{info line} to map source lines to program
6674 addresses (and vice versa), and the command @code{disassemble} to display
6675 a range of addresses as machine instructions. You can use the command
6676 @code{set disassemble-next-line} to set whether to disassemble next
6677 source line when execution stops. When run under @sc{gnu} Emacs
6678 mode, the @code{info line} command causes the arrow to point to the
6679 line specified. Also, @code{info line} prints addresses in symbolic form as
6684 @item info line @var{linespec}
6685 Print the starting and ending addresses of the compiled code for
6686 source line @var{linespec}. You can specify source lines in any of
6687 the ways documented in @ref{Specify Location}.
6690 For example, we can use @code{info line} to discover the location of
6691 the object code for the first line of function
6692 @code{m4_changequote}:
6694 @c FIXME: I think this example should also show the addresses in
6695 @c symbolic form, as they usually would be displayed.
6697 (@value{GDBP}) info line m4_changequote
6698 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6702 @cindex code address and its source line
6703 We can also inquire (using @code{*@var{addr}} as the form for
6704 @var{linespec}) what source line covers a particular address:
6706 (@value{GDBP}) info line *0x63ff
6707 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6710 @cindex @code{$_} and @code{info line}
6711 @cindex @code{x} command, default address
6712 @kindex x@r{(examine), and} info line
6713 After @code{info line}, the default address for the @code{x} command
6714 is changed to the starting address of the line, so that @samp{x/i} is
6715 sufficient to begin examining the machine code (@pxref{Memory,
6716 ,Examining Memory}). Also, this address is saved as the value of the
6717 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6722 @cindex assembly instructions
6723 @cindex instructions, assembly
6724 @cindex machine instructions
6725 @cindex listing machine instructions
6727 @itemx disassemble /m
6728 @itemx disassemble /r
6729 This specialized command dumps a range of memory as machine
6730 instructions. It can also print mixed source+disassembly by specifying
6731 the @code{/m} modifier and print the raw instructions in hex as well as
6732 in symbolic form by specifying the @code{/r}.
6733 The default memory range is the function surrounding the
6734 program counter of the selected frame. A single argument to this
6735 command is a program counter value; @value{GDBN} dumps the function
6736 surrounding this value. When two arguments are given, they should
6737 be separated by a comma, possibly surrounded by whitespace. The
6738 arguments specify a range of addresses (first inclusive, second exclusive)
6739 to dump. In that case, the name of the function is also printed (since
6740 there could be several functions in the given range).
6742 The argument(s) can be any expression yielding a numeric value, such as
6743 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6745 If the range of memory being disassembled contains current program counter,
6746 the instruction at that location is shown with a @code{=>} marker.
6749 The following example shows the disassembly of a range of addresses of
6750 HP PA-RISC 2.0 code:
6753 (@value{GDBP}) disas 0x32c4, 0x32e4
6754 Dump of assembler code from 0x32c4 to 0x32e4:
6755 0x32c4 <main+204>: addil 0,dp
6756 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6757 0x32cc <main+212>: ldil 0x3000,r31
6758 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6759 0x32d4 <main+220>: ldo 0(r31),rp
6760 0x32d8 <main+224>: addil -0x800,dp
6761 0x32dc <main+228>: ldo 0x588(r1),r26
6762 0x32e0 <main+232>: ldil 0x3000,r31
6763 End of assembler dump.
6766 Here is an example showing mixed source+assembly for Intel x86, when the
6767 program is stopped just after function prologue:
6770 (@value{GDBP}) disas /m main
6771 Dump of assembler code for function main:
6773 0x08048330 <+0>: push %ebp
6774 0x08048331 <+1>: mov %esp,%ebp
6775 0x08048333 <+3>: sub $0x8,%esp
6776 0x08048336 <+6>: and $0xfffffff0,%esp
6777 0x08048339 <+9>: sub $0x10,%esp
6779 6 printf ("Hello.\n");
6780 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6781 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6785 0x08048348 <+24>: mov $0x0,%eax
6786 0x0804834d <+29>: leave
6787 0x0804834e <+30>: ret
6789 End of assembler dump.
6792 Some architectures have more than one commonly-used set of instruction
6793 mnemonics or other syntax.
6795 For programs that were dynamically linked and use shared libraries,
6796 instructions that call functions or branch to locations in the shared
6797 libraries might show a seemingly bogus location---it's actually a
6798 location of the relocation table. On some architectures, @value{GDBN}
6799 might be able to resolve these to actual function names.
6802 @kindex set disassembly-flavor
6803 @cindex Intel disassembly flavor
6804 @cindex AT&T disassembly flavor
6805 @item set disassembly-flavor @var{instruction-set}
6806 Select the instruction set to use when disassembling the
6807 program via the @code{disassemble} or @code{x/i} commands.
6809 Currently this command is only defined for the Intel x86 family. You
6810 can set @var{instruction-set} to either @code{intel} or @code{att}.
6811 The default is @code{att}, the AT&T flavor used by default by Unix
6812 assemblers for x86-based targets.
6814 @kindex show disassembly-flavor
6815 @item show disassembly-flavor
6816 Show the current setting of the disassembly flavor.
6820 @kindex set disassemble-next-line
6821 @kindex show disassemble-next-line
6822 @item set disassemble-next-line
6823 @itemx show disassemble-next-line
6824 Control whether or not @value{GDBN} will disassemble the next source
6825 line or instruction when execution stops. If ON, @value{GDBN} will
6826 display disassembly of the next source line when execution of the
6827 program being debugged stops. This is @emph{in addition} to
6828 displaying the source line itself, which @value{GDBN} always does if
6829 possible. If the next source line cannot be displayed for some reason
6830 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6831 info in the debug info), @value{GDBN} will display disassembly of the
6832 next @emph{instruction} instead of showing the next source line. If
6833 AUTO, @value{GDBN} will display disassembly of next instruction only
6834 if the source line cannot be displayed. This setting causes
6835 @value{GDBN} to display some feedback when you step through a function
6836 with no line info or whose source file is unavailable. The default is
6837 OFF, which means never display the disassembly of the next line or
6843 @chapter Examining Data
6845 @cindex printing data
6846 @cindex examining data
6849 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6850 @c document because it is nonstandard... Under Epoch it displays in a
6851 @c different window or something like that.
6852 The usual way to examine data in your program is with the @code{print}
6853 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6854 evaluates and prints the value of an expression of the language your
6855 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6856 Different Languages}). It may also print the expression using a
6857 Python-based pretty-printer (@pxref{Pretty Printing}).
6860 @item print @var{expr}
6861 @itemx print /@var{f} @var{expr}
6862 @var{expr} is an expression (in the source language). By default the
6863 value of @var{expr} is printed in a format appropriate to its data type;
6864 you can choose a different format by specifying @samp{/@var{f}}, where
6865 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6869 @itemx print /@var{f}
6870 @cindex reprint the last value
6871 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6872 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6873 conveniently inspect the same value in an alternative format.
6876 A more low-level way of examining data is with the @code{x} command.
6877 It examines data in memory at a specified address and prints it in a
6878 specified format. @xref{Memory, ,Examining Memory}.
6880 If you are interested in information about types, or about how the
6881 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6882 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6886 * Expressions:: Expressions
6887 * Ambiguous Expressions:: Ambiguous Expressions
6888 * Variables:: Program variables
6889 * Arrays:: Artificial arrays
6890 * Output Formats:: Output formats
6891 * Memory:: Examining memory
6892 * Auto Display:: Automatic display
6893 * Print Settings:: Print settings
6894 * Pretty Printing:: Python pretty printing
6895 * Value History:: Value history
6896 * Convenience Vars:: Convenience variables
6897 * Registers:: Registers
6898 * Floating Point Hardware:: Floating point hardware
6899 * Vector Unit:: Vector Unit
6900 * OS Information:: Auxiliary data provided by operating system
6901 * Memory Region Attributes:: Memory region attributes
6902 * Dump/Restore Files:: Copy between memory and a file
6903 * Core File Generation:: Cause a program dump its core
6904 * Character Sets:: Debugging programs that use a different
6905 character set than GDB does
6906 * Caching Remote Data:: Data caching for remote targets
6907 * Searching Memory:: Searching memory for a sequence of bytes
6911 @section Expressions
6914 @code{print} and many other @value{GDBN} commands accept an expression and
6915 compute its value. Any kind of constant, variable or operator defined
6916 by the programming language you are using is valid in an expression in
6917 @value{GDBN}. This includes conditional expressions, function calls,
6918 casts, and string constants. It also includes preprocessor macros, if
6919 you compiled your program to include this information; see
6922 @cindex arrays in expressions
6923 @value{GDBN} supports array constants in expressions input by
6924 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6925 you can use the command @code{print @{1, 2, 3@}} to create an array
6926 of three integers. If you pass an array to a function or assign it
6927 to a program variable, @value{GDBN} copies the array to memory that
6928 is @code{malloc}ed in the target program.
6930 Because C is so widespread, most of the expressions shown in examples in
6931 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6932 Languages}, for information on how to use expressions in other
6935 In this section, we discuss operators that you can use in @value{GDBN}
6936 expressions regardless of your programming language.
6938 @cindex casts, in expressions
6939 Casts are supported in all languages, not just in C, because it is so
6940 useful to cast a number into a pointer in order to examine a structure
6941 at that address in memory.
6942 @c FIXME: casts supported---Mod2 true?
6944 @value{GDBN} supports these operators, in addition to those common
6945 to programming languages:
6949 @samp{@@} is a binary operator for treating parts of memory as arrays.
6950 @xref{Arrays, ,Artificial Arrays}, for more information.
6953 @samp{::} allows you to specify a variable in terms of the file or
6954 function where it is defined. @xref{Variables, ,Program Variables}.
6956 @cindex @{@var{type}@}
6957 @cindex type casting memory
6958 @cindex memory, viewing as typed object
6959 @cindex casts, to view memory
6960 @item @{@var{type}@} @var{addr}
6961 Refers to an object of type @var{type} stored at address @var{addr} in
6962 memory. @var{addr} may be any expression whose value is an integer or
6963 pointer (but parentheses are required around binary operators, just as in
6964 a cast). This construct is allowed regardless of what kind of data is
6965 normally supposed to reside at @var{addr}.
6968 @node Ambiguous Expressions
6969 @section Ambiguous Expressions
6970 @cindex ambiguous expressions
6972 Expressions can sometimes contain some ambiguous elements. For instance,
6973 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6974 a single function name to be defined several times, for application in
6975 different contexts. This is called @dfn{overloading}. Another example
6976 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6977 templates and is typically instantiated several times, resulting in
6978 the same function name being defined in different contexts.
6980 In some cases and depending on the language, it is possible to adjust
6981 the expression to remove the ambiguity. For instance in C@t{++}, you
6982 can specify the signature of the function you want to break on, as in
6983 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6984 qualified name of your function often makes the expression unambiguous
6987 When an ambiguity that needs to be resolved is detected, the debugger
6988 has the capability to display a menu of numbered choices for each
6989 possibility, and then waits for the selection with the prompt @samp{>}.
6990 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6991 aborts the current command. If the command in which the expression was
6992 used allows more than one choice to be selected, the next option in the
6993 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6996 For example, the following session excerpt shows an attempt to set a
6997 breakpoint at the overloaded symbol @code{String::after}.
6998 We choose three particular definitions of that function name:
7000 @c FIXME! This is likely to change to show arg type lists, at least
7003 (@value{GDBP}) b String::after
7006 [2] file:String.cc; line number:867
7007 [3] file:String.cc; line number:860
7008 [4] file:String.cc; line number:875
7009 [5] file:String.cc; line number:853
7010 [6] file:String.cc; line number:846
7011 [7] file:String.cc; line number:735
7013 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7014 Breakpoint 2 at 0xb344: file String.cc, line 875.
7015 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7016 Multiple breakpoints were set.
7017 Use the "delete" command to delete unwanted
7024 @kindex set multiple-symbols
7025 @item set multiple-symbols @var{mode}
7026 @cindex multiple-symbols menu
7028 This option allows you to adjust the debugger behavior when an expression
7031 By default, @var{mode} is set to @code{all}. If the command with which
7032 the expression is used allows more than one choice, then @value{GDBN}
7033 automatically selects all possible choices. For instance, inserting
7034 a breakpoint on a function using an ambiguous name results in a breakpoint
7035 inserted on each possible match. However, if a unique choice must be made,
7036 then @value{GDBN} uses the menu to help you disambiguate the expression.
7037 For instance, printing the address of an overloaded function will result
7038 in the use of the menu.
7040 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7041 when an ambiguity is detected.
7043 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7044 an error due to the ambiguity and the command is aborted.
7046 @kindex show multiple-symbols
7047 @item show multiple-symbols
7048 Show the current value of the @code{multiple-symbols} setting.
7052 @section Program Variables
7054 The most common kind of expression to use is the name of a variable
7057 Variables in expressions are understood in the selected stack frame
7058 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7062 global (or file-static)
7069 visible according to the scope rules of the
7070 programming language from the point of execution in that frame
7073 @noindent This means that in the function
7088 you can examine and use the variable @code{a} whenever your program is
7089 executing within the function @code{foo}, but you can only use or
7090 examine the variable @code{b} while your program is executing inside
7091 the block where @code{b} is declared.
7093 @cindex variable name conflict
7094 There is an exception: you can refer to a variable or function whose
7095 scope is a single source file even if the current execution point is not
7096 in this file. But it is possible to have more than one such variable or
7097 function with the same name (in different source files). If that
7098 happens, referring to that name has unpredictable effects. If you wish,
7099 you can specify a static variable in a particular function or file,
7100 using the colon-colon (@code{::}) notation:
7102 @cindex colon-colon, context for variables/functions
7104 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7105 @cindex @code{::}, context for variables/functions
7108 @var{file}::@var{variable}
7109 @var{function}::@var{variable}
7113 Here @var{file} or @var{function} is the name of the context for the
7114 static @var{variable}. In the case of file names, you can use quotes to
7115 make sure @value{GDBN} parses the file name as a single word---for example,
7116 to print a global value of @code{x} defined in @file{f2.c}:
7119 (@value{GDBP}) p 'f2.c'::x
7122 @cindex C@t{++} scope resolution
7123 This use of @samp{::} is very rarely in conflict with the very similar
7124 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7125 scope resolution operator in @value{GDBN} expressions.
7126 @c FIXME: Um, so what happens in one of those rare cases where it's in
7129 @cindex wrong values
7130 @cindex variable values, wrong
7131 @cindex function entry/exit, wrong values of variables
7132 @cindex optimized code, wrong values of variables
7134 @emph{Warning:} Occasionally, a local variable may appear to have the
7135 wrong value at certain points in a function---just after entry to a new
7136 scope, and just before exit.
7138 You may see this problem when you are stepping by machine instructions.
7139 This is because, on most machines, it takes more than one instruction to
7140 set up a stack frame (including local variable definitions); if you are
7141 stepping by machine instructions, variables may appear to have the wrong
7142 values until the stack frame is completely built. On exit, it usually
7143 also takes more than one machine instruction to destroy a stack frame;
7144 after you begin stepping through that group of instructions, local
7145 variable definitions may be gone.
7147 This may also happen when the compiler does significant optimizations.
7148 To be sure of always seeing accurate values, turn off all optimization
7151 @cindex ``No symbol "foo" in current context''
7152 Another possible effect of compiler optimizations is to optimize
7153 unused variables out of existence, or assign variables to registers (as
7154 opposed to memory addresses). Depending on the support for such cases
7155 offered by the debug info format used by the compiler, @value{GDBN}
7156 might not be able to display values for such local variables. If that
7157 happens, @value{GDBN} will print a message like this:
7160 No symbol "foo" in current context.
7163 To solve such problems, either recompile without optimizations, or use a
7164 different debug info format, if the compiler supports several such
7165 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7166 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7167 produces debug info in a format that is superior to formats such as
7168 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7169 an effective form for debug info. @xref{Debugging Options,,Options
7170 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7171 Compiler Collection (GCC)}.
7172 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7173 that are best suited to C@t{++} programs.
7175 If you ask to print an object whose contents are unknown to
7176 @value{GDBN}, e.g., because its data type is not completely specified
7177 by the debug information, @value{GDBN} will say @samp{<incomplete
7178 type>}. @xref{Symbols, incomplete type}, for more about this.
7180 Strings are identified as arrays of @code{char} values without specified
7181 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7182 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7183 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7184 defines literal string type @code{"char"} as @code{char} without a sign.
7189 signed char var1[] = "A";
7192 You get during debugging
7197 $2 = @{65 'A', 0 '\0'@}
7201 @section Artificial Arrays
7203 @cindex artificial array
7205 @kindex @@@r{, referencing memory as an array}
7206 It is often useful to print out several successive objects of the
7207 same type in memory; a section of an array, or an array of
7208 dynamically determined size for which only a pointer exists in the
7211 You can do this by referring to a contiguous span of memory as an
7212 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7213 operand of @samp{@@} should be the first element of the desired array
7214 and be an individual object. The right operand should be the desired length
7215 of the array. The result is an array value whose elements are all of
7216 the type of the left argument. The first element is actually the left
7217 argument; the second element comes from bytes of memory immediately
7218 following those that hold the first element, and so on. Here is an
7219 example. If a program says
7222 int *array = (int *) malloc (len * sizeof (int));
7226 you can print the contents of @code{array} with
7232 The left operand of @samp{@@} must reside in memory. Array values made
7233 with @samp{@@} in this way behave just like other arrays in terms of
7234 subscripting, and are coerced to pointers when used in expressions.
7235 Artificial arrays most often appear in expressions via the value history
7236 (@pxref{Value History, ,Value History}), after printing one out.
7238 Another way to create an artificial array is to use a cast.
7239 This re-interprets a value as if it were an array.
7240 The value need not be in memory:
7242 (@value{GDBP}) p/x (short[2])0x12345678
7243 $1 = @{0x1234, 0x5678@}
7246 As a convenience, if you leave the array length out (as in
7247 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7248 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7250 (@value{GDBP}) p/x (short[])0x12345678
7251 $2 = @{0x1234, 0x5678@}
7254 Sometimes the artificial array mechanism is not quite enough; in
7255 moderately complex data structures, the elements of interest may not
7256 actually be adjacent---for example, if you are interested in the values
7257 of pointers in an array. One useful work-around in this situation is
7258 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7259 Variables}) as a counter in an expression that prints the first
7260 interesting value, and then repeat that expression via @key{RET}. For
7261 instance, suppose you have an array @code{dtab} of pointers to
7262 structures, and you are interested in the values of a field @code{fv}
7263 in each structure. Here is an example of what you might type:
7273 @node Output Formats
7274 @section Output Formats
7276 @cindex formatted output
7277 @cindex output formats
7278 By default, @value{GDBN} prints a value according to its data type. Sometimes
7279 this is not what you want. For example, you might want to print a number
7280 in hex, or a pointer in decimal. Or you might want to view data in memory
7281 at a certain address as a character string or as an instruction. To do
7282 these things, specify an @dfn{output format} when you print a value.
7284 The simplest use of output formats is to say how to print a value
7285 already computed. This is done by starting the arguments of the
7286 @code{print} command with a slash and a format letter. The format
7287 letters supported are:
7291 Regard the bits of the value as an integer, and print the integer in
7295 Print as integer in signed decimal.
7298 Print as integer in unsigned decimal.
7301 Print as integer in octal.
7304 Print as integer in binary. The letter @samp{t} stands for ``two''.
7305 @footnote{@samp{b} cannot be used because these format letters are also
7306 used with the @code{x} command, where @samp{b} stands for ``byte'';
7307 see @ref{Memory,,Examining Memory}.}
7310 @cindex unknown address, locating
7311 @cindex locate address
7312 Print as an address, both absolute in hexadecimal and as an offset from
7313 the nearest preceding symbol. You can use this format used to discover
7314 where (in what function) an unknown address is located:
7317 (@value{GDBP}) p/a 0x54320
7318 $3 = 0x54320 <_initialize_vx+396>
7322 The command @code{info symbol 0x54320} yields similar results.
7323 @xref{Symbols, info symbol}.
7326 Regard as an integer and print it as a character constant. This
7327 prints both the numerical value and its character representation. The
7328 character representation is replaced with the octal escape @samp{\nnn}
7329 for characters outside the 7-bit @sc{ascii} range.
7331 Without this format, @value{GDBN} displays @code{char},
7332 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7333 constants. Single-byte members of vectors are displayed as integer
7337 Regard the bits of the value as a floating point number and print
7338 using typical floating point syntax.
7341 @cindex printing strings
7342 @cindex printing byte arrays
7343 Regard as a string, if possible. With this format, pointers to single-byte
7344 data are displayed as null-terminated strings and arrays of single-byte data
7345 are displayed as fixed-length strings. Other values are displayed in their
7348 Without this format, @value{GDBN} displays pointers to and arrays of
7349 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7350 strings. Single-byte members of a vector are displayed as an integer
7354 @cindex raw printing
7355 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7356 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7357 Printing}). This typically results in a higher-level display of the
7358 value's contents. The @samp{r} format bypasses any Python
7359 pretty-printer which might exist.
7362 For example, to print the program counter in hex (@pxref{Registers}), type
7369 Note that no space is required before the slash; this is because command
7370 names in @value{GDBN} cannot contain a slash.
7372 To reprint the last value in the value history with a different format,
7373 you can use the @code{print} command with just a format and no
7374 expression. For example, @samp{p/x} reprints the last value in hex.
7377 @section Examining Memory
7379 You can use the command @code{x} (for ``examine'') to examine memory in
7380 any of several formats, independently of your program's data types.
7382 @cindex examining memory
7384 @kindex x @r{(examine memory)}
7385 @item x/@var{nfu} @var{addr}
7388 Use the @code{x} command to examine memory.
7391 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7392 much memory to display and how to format it; @var{addr} is an
7393 expression giving the address where you want to start displaying memory.
7394 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7395 Several commands set convenient defaults for @var{addr}.
7398 @item @var{n}, the repeat count
7399 The repeat count is a decimal integer; the default is 1. It specifies
7400 how much memory (counting by units @var{u}) to display.
7401 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7404 @item @var{f}, the display format
7405 The display format is one of the formats used by @code{print}
7406 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7407 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7408 The default is @samp{x} (hexadecimal) initially. The default changes
7409 each time you use either @code{x} or @code{print}.
7411 @item @var{u}, the unit size
7412 The unit size is any of
7418 Halfwords (two bytes).
7420 Words (four bytes). This is the initial default.
7422 Giant words (eight bytes).
7425 Each time you specify a unit size with @code{x}, that size becomes the
7426 default unit the next time you use @code{x}. For the @samp{i} format,
7427 the unit size is ignored and is normally not written. For the @samp{s} format,
7428 the unit size defaults to @samp{b}, unless it is explicitly given.
7429 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7430 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7431 Note that the results depend on the programming language of the
7432 current compilation unit. If the language is C, the @samp{s}
7433 modifier will use the UTF-16 encoding while @samp{w} will use
7434 UTF-32. The encoding is set by the programming language and cannot
7437 @item @var{addr}, starting display address
7438 @var{addr} is the address where you want @value{GDBN} to begin displaying
7439 memory. The expression need not have a pointer value (though it may);
7440 it is always interpreted as an integer address of a byte of memory.
7441 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7442 @var{addr} is usually just after the last address examined---but several
7443 other commands also set the default address: @code{info breakpoints} (to
7444 the address of the last breakpoint listed), @code{info line} (to the
7445 starting address of a line), and @code{print} (if you use it to display
7446 a value from memory).
7449 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7450 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7451 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7452 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7453 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7455 Since the letters indicating unit sizes are all distinct from the
7456 letters specifying output formats, you do not have to remember whether
7457 unit size or format comes first; either order works. The output
7458 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7459 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7461 Even though the unit size @var{u} is ignored for the formats @samp{s}
7462 and @samp{i}, you might still want to use a count @var{n}; for example,
7463 @samp{3i} specifies that you want to see three machine instructions,
7464 including any operands. For convenience, especially when used with
7465 the @code{display} command, the @samp{i} format also prints branch delay
7466 slot instructions, if any, beyond the count specified, which immediately
7467 follow the last instruction that is within the count. The command
7468 @code{disassemble} gives an alternative way of inspecting machine
7469 instructions; see @ref{Machine Code,,Source and Machine Code}.
7471 All the defaults for the arguments to @code{x} are designed to make it
7472 easy to continue scanning memory with minimal specifications each time
7473 you use @code{x}. For example, after you have inspected three machine
7474 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7475 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7476 the repeat count @var{n} is used again; the other arguments default as
7477 for successive uses of @code{x}.
7479 When examining machine instructions, the instruction at current program
7480 counter is shown with a @code{=>} marker. For example:
7483 (@value{GDBP}) x/5i $pc-6
7484 0x804837f <main+11>: mov %esp,%ebp
7485 0x8048381 <main+13>: push %ecx
7486 0x8048382 <main+14>: sub $0x4,%esp
7487 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7488 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7491 @cindex @code{$_}, @code{$__}, and value history
7492 The addresses and contents printed by the @code{x} command are not saved
7493 in the value history because there is often too much of them and they
7494 would get in the way. Instead, @value{GDBN} makes these values available for
7495 subsequent use in expressions as values of the convenience variables
7496 @code{$_} and @code{$__}. After an @code{x} command, the last address
7497 examined is available for use in expressions in the convenience variable
7498 @code{$_}. The contents of that address, as examined, are available in
7499 the convenience variable @code{$__}.
7501 If the @code{x} command has a repeat count, the address and contents saved
7502 are from the last memory unit printed; this is not the same as the last
7503 address printed if several units were printed on the last line of output.
7505 @cindex remote memory comparison
7506 @cindex verify remote memory image
7507 When you are debugging a program running on a remote target machine
7508 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7509 remote machine's memory against the executable file you downloaded to
7510 the target. The @code{compare-sections} command is provided for such
7514 @kindex compare-sections
7515 @item compare-sections @r{[}@var{section-name}@r{]}
7516 Compare the data of a loadable section @var{section-name} in the
7517 executable file of the program being debugged with the same section in
7518 the remote machine's memory, and report any mismatches. With no
7519 arguments, compares all loadable sections. This command's
7520 availability depends on the target's support for the @code{"qCRC"}
7525 @section Automatic Display
7526 @cindex automatic display
7527 @cindex display of expressions
7529 If you find that you want to print the value of an expression frequently
7530 (to see how it changes), you might want to add it to the @dfn{automatic
7531 display list} so that @value{GDBN} prints its value each time your program stops.
7532 Each expression added to the list is given a number to identify it;
7533 to remove an expression from the list, you specify that number.
7534 The automatic display looks like this:
7538 3: bar[5] = (struct hack *) 0x3804
7542 This display shows item numbers, expressions and their current values. As with
7543 displays you request manually using @code{x} or @code{print}, you can
7544 specify the output format you prefer; in fact, @code{display} decides
7545 whether to use @code{print} or @code{x} depending your format
7546 specification---it uses @code{x} if you specify either the @samp{i}
7547 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7551 @item display @var{expr}
7552 Add the expression @var{expr} to the list of expressions to display
7553 each time your program stops. @xref{Expressions, ,Expressions}.
7555 @code{display} does not repeat if you press @key{RET} again after using it.
7557 @item display/@var{fmt} @var{expr}
7558 For @var{fmt} specifying only a display format and not a size or
7559 count, add the expression @var{expr} to the auto-display list but
7560 arrange to display it each time in the specified format @var{fmt}.
7561 @xref{Output Formats,,Output Formats}.
7563 @item display/@var{fmt} @var{addr}
7564 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7565 number of units, add the expression @var{addr} as a memory address to
7566 be examined each time your program stops. Examining means in effect
7567 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7570 For example, @samp{display/i $pc} can be helpful, to see the machine
7571 instruction about to be executed each time execution stops (@samp{$pc}
7572 is a common name for the program counter; @pxref{Registers, ,Registers}).
7575 @kindex delete display
7577 @item undisplay @var{dnums}@dots{}
7578 @itemx delete display @var{dnums}@dots{}
7579 Remove item numbers @var{dnums} from the list of expressions to display.
7581 @code{undisplay} does not repeat if you press @key{RET} after using it.
7582 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7584 @kindex disable display
7585 @item disable display @var{dnums}@dots{}
7586 Disable the display of item numbers @var{dnums}. A disabled display
7587 item is not printed automatically, but is not forgotten. It may be
7588 enabled again later.
7590 @kindex enable display
7591 @item enable display @var{dnums}@dots{}
7592 Enable display of item numbers @var{dnums}. It becomes effective once
7593 again in auto display of its expression, until you specify otherwise.
7596 Display the current values of the expressions on the list, just as is
7597 done when your program stops.
7599 @kindex info display
7601 Print the list of expressions previously set up to display
7602 automatically, each one with its item number, but without showing the
7603 values. This includes disabled expressions, which are marked as such.
7604 It also includes expressions which would not be displayed right now
7605 because they refer to automatic variables not currently available.
7608 @cindex display disabled out of scope
7609 If a display expression refers to local variables, then it does not make
7610 sense outside the lexical context for which it was set up. Such an
7611 expression is disabled when execution enters a context where one of its
7612 variables is not defined. For example, if you give the command
7613 @code{display last_char} while inside a function with an argument
7614 @code{last_char}, @value{GDBN} displays this argument while your program
7615 continues to stop inside that function. When it stops elsewhere---where
7616 there is no variable @code{last_char}---the display is disabled
7617 automatically. The next time your program stops where @code{last_char}
7618 is meaningful, you can enable the display expression once again.
7620 @node Print Settings
7621 @section Print Settings
7623 @cindex format options
7624 @cindex print settings
7625 @value{GDBN} provides the following ways to control how arrays, structures,
7626 and symbols are printed.
7629 These settings are useful for debugging programs in any language:
7633 @item set print address
7634 @itemx set print address on
7635 @cindex print/don't print memory addresses
7636 @value{GDBN} prints memory addresses showing the location of stack
7637 traces, structure values, pointer values, breakpoints, and so forth,
7638 even when it also displays the contents of those addresses. The default
7639 is @code{on}. For example, this is what a stack frame display looks like with
7640 @code{set print address on}:
7645 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7647 530 if (lquote != def_lquote)
7651 @item set print address off
7652 Do not print addresses when displaying their contents. For example,
7653 this is the same stack frame displayed with @code{set print address off}:
7657 (@value{GDBP}) set print addr off
7659 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7660 530 if (lquote != def_lquote)
7664 You can use @samp{set print address off} to eliminate all machine
7665 dependent displays from the @value{GDBN} interface. For example, with
7666 @code{print address off}, you should get the same text for backtraces on
7667 all machines---whether or not they involve pointer arguments.
7670 @item show print address
7671 Show whether or not addresses are to be printed.
7674 When @value{GDBN} prints a symbolic address, it normally prints the
7675 closest earlier symbol plus an offset. If that symbol does not uniquely
7676 identify the address (for example, it is a name whose scope is a single
7677 source file), you may need to clarify. One way to do this is with
7678 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7679 you can set @value{GDBN} to print the source file and line number when
7680 it prints a symbolic address:
7683 @item set print symbol-filename on
7684 @cindex source file and line of a symbol
7685 @cindex symbol, source file and line
7686 Tell @value{GDBN} to print the source file name and line number of a
7687 symbol in the symbolic form of an address.
7689 @item set print symbol-filename off
7690 Do not print source file name and line number of a symbol. This is the
7693 @item show print symbol-filename
7694 Show whether or not @value{GDBN} will print the source file name and
7695 line number of a symbol in the symbolic form of an address.
7698 Another situation where it is helpful to show symbol filenames and line
7699 numbers is when disassembling code; @value{GDBN} shows you the line
7700 number and source file that corresponds to each instruction.
7702 Also, you may wish to see the symbolic form only if the address being
7703 printed is reasonably close to the closest earlier symbol:
7706 @item set print max-symbolic-offset @var{max-offset}
7707 @cindex maximum value for offset of closest symbol
7708 Tell @value{GDBN} to only display the symbolic form of an address if the
7709 offset between the closest earlier symbol and the address is less than
7710 @var{max-offset}. The default is 0, which tells @value{GDBN}
7711 to always print the symbolic form of an address if any symbol precedes it.
7713 @item show print max-symbolic-offset
7714 Ask how large the maximum offset is that @value{GDBN} prints in a
7718 @cindex wild pointer, interpreting
7719 @cindex pointer, finding referent
7720 If you have a pointer and you are not sure where it points, try
7721 @samp{set print symbol-filename on}. Then you can determine the name
7722 and source file location of the variable where it points, using
7723 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7724 For example, here @value{GDBN} shows that a variable @code{ptt} points
7725 at another variable @code{t}, defined in @file{hi2.c}:
7728 (@value{GDBP}) set print symbol-filename on
7729 (@value{GDBP}) p/a ptt
7730 $4 = 0xe008 <t in hi2.c>
7734 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7735 does not show the symbol name and filename of the referent, even with
7736 the appropriate @code{set print} options turned on.
7739 Other settings control how different kinds of objects are printed:
7742 @item set print array
7743 @itemx set print array on
7744 @cindex pretty print arrays
7745 Pretty print arrays. This format is more convenient to read,
7746 but uses more space. The default is off.
7748 @item set print array off
7749 Return to compressed format for arrays.
7751 @item show print array
7752 Show whether compressed or pretty format is selected for displaying
7755 @cindex print array indexes
7756 @item set print array-indexes
7757 @itemx set print array-indexes on
7758 Print the index of each element when displaying arrays. May be more
7759 convenient to locate a given element in the array or quickly find the
7760 index of a given element in that printed array. The default is off.
7762 @item set print array-indexes off
7763 Stop printing element indexes when displaying arrays.
7765 @item show print array-indexes
7766 Show whether the index of each element is printed when displaying
7769 @item set print elements @var{number-of-elements}
7770 @cindex number of array elements to print
7771 @cindex limit on number of printed array elements
7772 Set a limit on how many elements of an array @value{GDBN} will print.
7773 If @value{GDBN} is printing a large array, it stops printing after it has
7774 printed the number of elements set by the @code{set print elements} command.
7775 This limit also applies to the display of strings.
7776 When @value{GDBN} starts, this limit is set to 200.
7777 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7779 @item show print elements
7780 Display the number of elements of a large array that @value{GDBN} will print.
7781 If the number is 0, then the printing is unlimited.
7783 @item set print frame-arguments @var{value}
7784 @kindex set print frame-arguments
7785 @cindex printing frame argument values
7786 @cindex print all frame argument values
7787 @cindex print frame argument values for scalars only
7788 @cindex do not print frame argument values
7789 This command allows to control how the values of arguments are printed
7790 when the debugger prints a frame (@pxref{Frames}). The possible
7795 The values of all arguments are printed.
7798 Print the value of an argument only if it is a scalar. The value of more
7799 complex arguments such as arrays, structures, unions, etc, is replaced
7800 by @code{@dots{}}. This is the default. Here is an example where
7801 only scalar arguments are shown:
7804 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7809 None of the argument values are printed. Instead, the value of each argument
7810 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7813 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7818 By default, only scalar arguments are printed. This command can be used
7819 to configure the debugger to print the value of all arguments, regardless
7820 of their type. However, it is often advantageous to not print the value
7821 of more complex parameters. For instance, it reduces the amount of
7822 information printed in each frame, making the backtrace more readable.
7823 Also, it improves performance when displaying Ada frames, because
7824 the computation of large arguments can sometimes be CPU-intensive,
7825 especially in large applications. Setting @code{print frame-arguments}
7826 to @code{scalars} (the default) or @code{none} avoids this computation,
7827 thus speeding up the display of each Ada frame.
7829 @item show print frame-arguments
7830 Show how the value of arguments should be displayed when printing a frame.
7832 @item set print repeats
7833 @cindex repeated array elements
7834 Set the threshold for suppressing display of repeated array
7835 elements. When the number of consecutive identical elements of an
7836 array exceeds the threshold, @value{GDBN} prints the string
7837 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7838 identical repetitions, instead of displaying the identical elements
7839 themselves. Setting the threshold to zero will cause all elements to
7840 be individually printed. The default threshold is 10.
7842 @item show print repeats
7843 Display the current threshold for printing repeated identical
7846 @item set print null-stop
7847 @cindex @sc{null} elements in arrays
7848 Cause @value{GDBN} to stop printing the characters of an array when the first
7849 @sc{null} is encountered. This is useful when large arrays actually
7850 contain only short strings.
7853 @item show print null-stop
7854 Show whether @value{GDBN} stops printing an array on the first
7855 @sc{null} character.
7857 @item set print pretty on
7858 @cindex print structures in indented form
7859 @cindex indentation in structure display
7860 Cause @value{GDBN} to print structures in an indented format with one member
7861 per line, like this:
7876 @item set print pretty off
7877 Cause @value{GDBN} to print structures in a compact format, like this:
7881 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7882 meat = 0x54 "Pork"@}
7887 This is the default format.
7889 @item show print pretty
7890 Show which format @value{GDBN} is using to print structures.
7892 @item set print sevenbit-strings on
7893 @cindex eight-bit characters in strings
7894 @cindex octal escapes in strings
7895 Print using only seven-bit characters; if this option is set,
7896 @value{GDBN} displays any eight-bit characters (in strings or
7897 character values) using the notation @code{\}@var{nnn}. This setting is
7898 best if you are working in English (@sc{ascii}) and you use the
7899 high-order bit of characters as a marker or ``meta'' bit.
7901 @item set print sevenbit-strings off
7902 Print full eight-bit characters. This allows the use of more
7903 international character sets, and is the default.
7905 @item show print sevenbit-strings
7906 Show whether or not @value{GDBN} is printing only seven-bit characters.
7908 @item set print union on
7909 @cindex unions in structures, printing
7910 Tell @value{GDBN} to print unions which are contained in structures
7911 and other unions. This is the default setting.
7913 @item set print union off
7914 Tell @value{GDBN} not to print unions which are contained in
7915 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7918 @item show print union
7919 Ask @value{GDBN} whether or not it will print unions which are contained in
7920 structures and other unions.
7922 For example, given the declarations
7925 typedef enum @{Tree, Bug@} Species;
7926 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7927 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7938 struct thing foo = @{Tree, @{Acorn@}@};
7942 with @code{set print union on} in effect @samp{p foo} would print
7945 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7949 and with @code{set print union off} in effect it would print
7952 $1 = @{it = Tree, form = @{...@}@}
7956 @code{set print union} affects programs written in C-like languages
7962 These settings are of interest when debugging C@t{++} programs:
7965 @cindex demangling C@t{++} names
7966 @item set print demangle
7967 @itemx set print demangle on
7968 Print C@t{++} names in their source form rather than in the encoded
7969 (``mangled'') form passed to the assembler and linker for type-safe
7970 linkage. The default is on.
7972 @item show print demangle
7973 Show whether C@t{++} names are printed in mangled or demangled form.
7975 @item set print asm-demangle
7976 @itemx set print asm-demangle on
7977 Print C@t{++} names in their source form rather than their mangled form, even
7978 in assembler code printouts such as instruction disassemblies.
7981 @item show print asm-demangle
7982 Show whether C@t{++} names in assembly listings are printed in mangled
7985 @cindex C@t{++} symbol decoding style
7986 @cindex symbol decoding style, C@t{++}
7987 @kindex set demangle-style
7988 @item set demangle-style @var{style}
7989 Choose among several encoding schemes used by different compilers to
7990 represent C@t{++} names. The choices for @var{style} are currently:
7994 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7997 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7998 This is the default.
8001 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8004 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8007 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8008 @strong{Warning:} this setting alone is not sufficient to allow
8009 debugging @code{cfront}-generated executables. @value{GDBN} would
8010 require further enhancement to permit that.
8013 If you omit @var{style}, you will see a list of possible formats.
8015 @item show demangle-style
8016 Display the encoding style currently in use for decoding C@t{++} symbols.
8018 @item set print object
8019 @itemx set print object on
8020 @cindex derived type of an object, printing
8021 @cindex display derived types
8022 When displaying a pointer to an object, identify the @emph{actual}
8023 (derived) type of the object rather than the @emph{declared} type, using
8024 the virtual function table.
8026 @item set print object off
8027 Display only the declared type of objects, without reference to the
8028 virtual function table. This is the default setting.
8030 @item show print object
8031 Show whether actual, or declared, object types are displayed.
8033 @item set print static-members
8034 @itemx set print static-members on
8035 @cindex static members of C@t{++} objects
8036 Print static members when displaying a C@t{++} object. The default is on.
8038 @item set print static-members off
8039 Do not print static members when displaying a C@t{++} object.
8041 @item show print static-members
8042 Show whether C@t{++} static members are printed or not.
8044 @item set print pascal_static-members
8045 @itemx set print pascal_static-members on
8046 @cindex static members of Pascal objects
8047 @cindex Pascal objects, static members display
8048 Print static members when displaying a Pascal object. The default is on.
8050 @item set print pascal_static-members off
8051 Do not print static members when displaying a Pascal object.
8053 @item show print pascal_static-members
8054 Show whether Pascal static members are printed or not.
8056 @c These don't work with HP ANSI C++ yet.
8057 @item set print vtbl
8058 @itemx set print vtbl on
8059 @cindex pretty print C@t{++} virtual function tables
8060 @cindex virtual functions (C@t{++}) display
8061 @cindex VTBL display
8062 Pretty print C@t{++} virtual function tables. The default is off.
8063 (The @code{vtbl} commands do not work on programs compiled with the HP
8064 ANSI C@t{++} compiler (@code{aCC}).)
8066 @item set print vtbl off
8067 Do not pretty print C@t{++} virtual function tables.
8069 @item show print vtbl
8070 Show whether C@t{++} virtual function tables are pretty printed, or not.
8073 @node Pretty Printing
8074 @section Pretty Printing
8076 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8077 Python code. It greatly simplifies the display of complex objects. This
8078 mechanism works for both MI and the CLI.
8080 For example, here is how a C@t{++} @code{std::string} looks without a
8084 (@value{GDBP}) print s
8086 static npos = 4294967295,
8088 <std::allocator<char>> = @{
8089 <__gnu_cxx::new_allocator<char>> = @{
8090 <No data fields>@}, <No data fields>
8092 members of std::basic_string<char, std::char_traits<char>,
8093 std::allocator<char> >::_Alloc_hider:
8094 _M_p = 0x804a014 "abcd"
8099 With a pretty-printer for @code{std::string} only the contents are printed:
8102 (@value{GDBP}) print s
8106 For implementing pretty printers for new types you should read the Python API
8107 details (@pxref{Pretty Printing API}).
8110 @section Value History
8112 @cindex value history
8113 @cindex history of values printed by @value{GDBN}
8114 Values printed by the @code{print} command are saved in the @value{GDBN}
8115 @dfn{value history}. This allows you to refer to them in other expressions.
8116 Values are kept until the symbol table is re-read or discarded
8117 (for example with the @code{file} or @code{symbol-file} commands).
8118 When the symbol table changes, the value history is discarded,
8119 since the values may contain pointers back to the types defined in the
8124 @cindex history number
8125 The values printed are given @dfn{history numbers} by which you can
8126 refer to them. These are successive integers starting with one.
8127 @code{print} shows you the history number assigned to a value by
8128 printing @samp{$@var{num} = } before the value; here @var{num} is the
8131 To refer to any previous value, use @samp{$} followed by the value's
8132 history number. The way @code{print} labels its output is designed to
8133 remind you of this. Just @code{$} refers to the most recent value in
8134 the history, and @code{$$} refers to the value before that.
8135 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8136 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8137 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8139 For example, suppose you have just printed a pointer to a structure and
8140 want to see the contents of the structure. It suffices to type
8146 If you have a chain of structures where the component @code{next} points
8147 to the next one, you can print the contents of the next one with this:
8154 You can print successive links in the chain by repeating this
8155 command---which you can do by just typing @key{RET}.
8157 Note that the history records values, not expressions. If the value of
8158 @code{x} is 4 and you type these commands:
8166 then the value recorded in the value history by the @code{print} command
8167 remains 4 even though the value of @code{x} has changed.
8172 Print the last ten values in the value history, with their item numbers.
8173 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8174 values} does not change the history.
8176 @item show values @var{n}
8177 Print ten history values centered on history item number @var{n}.
8180 Print ten history values just after the values last printed. If no more
8181 values are available, @code{show values +} produces no display.
8184 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8185 same effect as @samp{show values +}.
8187 @node Convenience Vars
8188 @section Convenience Variables
8190 @cindex convenience variables
8191 @cindex user-defined variables
8192 @value{GDBN} provides @dfn{convenience variables} that you can use within
8193 @value{GDBN} to hold on to a value and refer to it later. These variables
8194 exist entirely within @value{GDBN}; they are not part of your program, and
8195 setting a convenience variable has no direct effect on further execution
8196 of your program. That is why you can use them freely.
8198 Convenience variables are prefixed with @samp{$}. Any name preceded by
8199 @samp{$} can be used for a convenience variable, unless it is one of
8200 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8201 (Value history references, in contrast, are @emph{numbers} preceded
8202 by @samp{$}. @xref{Value History, ,Value History}.)
8204 You can save a value in a convenience variable with an assignment
8205 expression, just as you would set a variable in your program.
8209 set $foo = *object_ptr
8213 would save in @code{$foo} the value contained in the object pointed to by
8216 Using a convenience variable for the first time creates it, but its
8217 value is @code{void} until you assign a new value. You can alter the
8218 value with another assignment at any time.
8220 Convenience variables have no fixed types. You can assign a convenience
8221 variable any type of value, including structures and arrays, even if
8222 that variable already has a value of a different type. The convenience
8223 variable, when used as an expression, has the type of its current value.
8226 @kindex show convenience
8227 @cindex show all user variables
8228 @item show convenience
8229 Print a list of convenience variables used so far, and their values.
8230 Abbreviated @code{show conv}.
8232 @kindex init-if-undefined
8233 @cindex convenience variables, initializing
8234 @item init-if-undefined $@var{variable} = @var{expression}
8235 Set a convenience variable if it has not already been set. This is useful
8236 for user-defined commands that keep some state. It is similar, in concept,
8237 to using local static variables with initializers in C (except that
8238 convenience variables are global). It can also be used to allow users to
8239 override default values used in a command script.
8241 If the variable is already defined then the expression is not evaluated so
8242 any side-effects do not occur.
8245 One of the ways to use a convenience variable is as a counter to be
8246 incremented or a pointer to be advanced. For example, to print
8247 a field from successive elements of an array of structures:
8251 print bar[$i++]->contents
8255 Repeat that command by typing @key{RET}.
8257 Some convenience variables are created automatically by @value{GDBN} and given
8258 values likely to be useful.
8261 @vindex $_@r{, convenience variable}
8263 The variable @code{$_} is automatically set by the @code{x} command to
8264 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8265 commands which provide a default address for @code{x} to examine also
8266 set @code{$_} to that address; these commands include @code{info line}
8267 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8268 except when set by the @code{x} command, in which case it is a pointer
8269 to the type of @code{$__}.
8271 @vindex $__@r{, convenience variable}
8273 The variable @code{$__} is automatically set by the @code{x} command
8274 to the value found in the last address examined. Its type is chosen
8275 to match the format in which the data was printed.
8278 @vindex $_exitcode@r{, convenience variable}
8279 The variable @code{$_exitcode} is automatically set to the exit code when
8280 the program being debugged terminates.
8283 @vindex $_siginfo@r{, convenience variable}
8284 The variable @code{$_siginfo} contains extra signal information
8285 (@pxref{extra signal information}). Note that @code{$_siginfo}
8286 could be empty, if the application has not yet received any signals.
8287 For example, it will be empty before you execute the @code{run} command.
8290 @vindex $_tlb@r{, convenience variable}
8291 The variable @code{$_tlb} is automatically set when debugging
8292 applications running on MS-Windows in native mode or connected to
8293 gdbserver that supports the @code{qGetTIBAddr} request.
8294 @xref{General Query Packets}.
8295 This variable contains the address of the thread information block.
8299 On HP-UX systems, if you refer to a function or variable name that
8300 begins with a dollar sign, @value{GDBN} searches for a user or system
8301 name first, before it searches for a convenience variable.
8303 @cindex convenience functions
8304 @value{GDBN} also supplies some @dfn{convenience functions}. These
8305 have a syntax similar to convenience variables. A convenience
8306 function can be used in an expression just like an ordinary function;
8307 however, a convenience function is implemented internally to
8312 @kindex help function
8313 @cindex show all convenience functions
8314 Print a list of all convenience functions.
8321 You can refer to machine register contents, in expressions, as variables
8322 with names starting with @samp{$}. The names of registers are different
8323 for each machine; use @code{info registers} to see the names used on
8327 @kindex info registers
8328 @item info registers
8329 Print the names and values of all registers except floating-point
8330 and vector registers (in the selected stack frame).
8332 @kindex info all-registers
8333 @cindex floating point registers
8334 @item info all-registers
8335 Print the names and values of all registers, including floating-point
8336 and vector registers (in the selected stack frame).
8338 @item info registers @var{regname} @dots{}
8339 Print the @dfn{relativized} value of each specified register @var{regname}.
8340 As discussed in detail below, register values are normally relative to
8341 the selected stack frame. @var{regname} may be any register name valid on
8342 the machine you are using, with or without the initial @samp{$}.
8345 @cindex stack pointer register
8346 @cindex program counter register
8347 @cindex process status register
8348 @cindex frame pointer register
8349 @cindex standard registers
8350 @value{GDBN} has four ``standard'' register names that are available (in
8351 expressions) on most machines---whenever they do not conflict with an
8352 architecture's canonical mnemonics for registers. The register names
8353 @code{$pc} and @code{$sp} are used for the program counter register and
8354 the stack pointer. @code{$fp} is used for a register that contains a
8355 pointer to the current stack frame, and @code{$ps} is used for a
8356 register that contains the processor status. For example,
8357 you could print the program counter in hex with
8364 or print the instruction to be executed next with
8371 or add four to the stack pointer@footnote{This is a way of removing
8372 one word from the stack, on machines where stacks grow downward in
8373 memory (most machines, nowadays). This assumes that the innermost
8374 stack frame is selected; setting @code{$sp} is not allowed when other
8375 stack frames are selected. To pop entire frames off the stack,
8376 regardless of machine architecture, use @code{return};
8377 see @ref{Returning, ,Returning from a Function}.} with
8383 Whenever possible, these four standard register names are available on
8384 your machine even though the machine has different canonical mnemonics,
8385 so long as there is no conflict. The @code{info registers} command
8386 shows the canonical names. For example, on the SPARC, @code{info
8387 registers} displays the processor status register as @code{$psr} but you
8388 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8389 is an alias for the @sc{eflags} register.
8391 @value{GDBN} always considers the contents of an ordinary register as an
8392 integer when the register is examined in this way. Some machines have
8393 special registers which can hold nothing but floating point; these
8394 registers are considered to have floating point values. There is no way
8395 to refer to the contents of an ordinary register as floating point value
8396 (although you can @emph{print} it as a floating point value with
8397 @samp{print/f $@var{regname}}).
8399 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8400 means that the data format in which the register contents are saved by
8401 the operating system is not the same one that your program normally
8402 sees. For example, the registers of the 68881 floating point
8403 coprocessor are always saved in ``extended'' (raw) format, but all C
8404 programs expect to work with ``double'' (virtual) format. In such
8405 cases, @value{GDBN} normally works with the virtual format only (the format
8406 that makes sense for your program), but the @code{info registers} command
8407 prints the data in both formats.
8409 @cindex SSE registers (x86)
8410 @cindex MMX registers (x86)
8411 Some machines have special registers whose contents can be interpreted
8412 in several different ways. For example, modern x86-based machines
8413 have SSE and MMX registers that can hold several values packed
8414 together in several different formats. @value{GDBN} refers to such
8415 registers in @code{struct} notation:
8418 (@value{GDBP}) print $xmm1
8420 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8421 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8422 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8423 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8424 v4_int32 = @{0, 20657912, 11, 13@},
8425 v2_int64 = @{88725056443645952, 55834574859@},
8426 uint128 = 0x0000000d0000000b013b36f800000000
8431 To set values of such registers, you need to tell @value{GDBN} which
8432 view of the register you wish to change, as if you were assigning
8433 value to a @code{struct} member:
8436 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8439 Normally, register values are relative to the selected stack frame
8440 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8441 value that the register would contain if all stack frames farther in
8442 were exited and their saved registers restored. In order to see the
8443 true contents of hardware registers, you must select the innermost
8444 frame (with @samp{frame 0}).
8446 However, @value{GDBN} must deduce where registers are saved, from the machine
8447 code generated by your compiler. If some registers are not saved, or if
8448 @value{GDBN} is unable to locate the saved registers, the selected stack
8449 frame makes no difference.
8451 @node Floating Point Hardware
8452 @section Floating Point Hardware
8453 @cindex floating point
8455 Depending on the configuration, @value{GDBN} may be able to give
8456 you more information about the status of the floating point hardware.
8461 Display hardware-dependent information about the floating
8462 point unit. The exact contents and layout vary depending on the
8463 floating point chip. Currently, @samp{info float} is supported on
8464 the ARM and x86 machines.
8468 @section Vector Unit
8471 Depending on the configuration, @value{GDBN} may be able to give you
8472 more information about the status of the vector unit.
8477 Display information about the vector unit. The exact contents and
8478 layout vary depending on the hardware.
8481 @node OS Information
8482 @section Operating System Auxiliary Information
8483 @cindex OS information
8485 @value{GDBN} provides interfaces to useful OS facilities that can help
8486 you debug your program.
8488 @cindex @code{ptrace} system call
8489 @cindex @code{struct user} contents
8490 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8491 machines), it interfaces with the inferior via the @code{ptrace}
8492 system call. The operating system creates a special sata structure,
8493 called @code{struct user}, for this interface. You can use the
8494 command @code{info udot} to display the contents of this data
8500 Display the contents of the @code{struct user} maintained by the OS
8501 kernel for the program being debugged. @value{GDBN} displays the
8502 contents of @code{struct user} as a list of hex numbers, similar to
8503 the @code{examine} command.
8506 @cindex auxiliary vector
8507 @cindex vector, auxiliary
8508 Some operating systems supply an @dfn{auxiliary vector} to programs at
8509 startup. This is akin to the arguments and environment that you
8510 specify for a program, but contains a system-dependent variety of
8511 binary values that tell system libraries important details about the
8512 hardware, operating system, and process. Each value's purpose is
8513 identified by an integer tag; the meanings are well-known but system-specific.
8514 Depending on the configuration and operating system facilities,
8515 @value{GDBN} may be able to show you this information. For remote
8516 targets, this functionality may further depend on the remote stub's
8517 support of the @samp{qXfer:auxv:read} packet, see
8518 @ref{qXfer auxiliary vector read}.
8523 Display the auxiliary vector of the inferior, which can be either a
8524 live process or a core dump file. @value{GDBN} prints each tag value
8525 numerically, and also shows names and text descriptions for recognized
8526 tags. Some values in the vector are numbers, some bit masks, and some
8527 pointers to strings or other data. @value{GDBN} displays each value in the
8528 most appropriate form for a recognized tag, and in hexadecimal for
8529 an unrecognized tag.
8532 On some targets, @value{GDBN} can access operating-system-specific information
8533 and display it to user, without interpretation. For remote targets,
8534 this functionality depends on the remote stub's support of the
8535 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8540 List the types of OS information available for the target. If the
8541 target does not return a list of possible types, this command will
8544 @kindex info os processes
8545 @item info os processes
8546 Display the list of processes on the target. For each process,
8547 @value{GDBN} prints the process identifier, the name of the user, and
8548 the command corresponding to the process.
8551 @node Memory Region Attributes
8552 @section Memory Region Attributes
8553 @cindex memory region attributes
8555 @dfn{Memory region attributes} allow you to describe special handling
8556 required by regions of your target's memory. @value{GDBN} uses
8557 attributes to determine whether to allow certain types of memory
8558 accesses; whether to use specific width accesses; and whether to cache
8559 target memory. By default the description of memory regions is
8560 fetched from the target (if the current target supports this), but the
8561 user can override the fetched regions.
8563 Defined memory regions can be individually enabled and disabled. When a
8564 memory region is disabled, @value{GDBN} uses the default attributes when
8565 accessing memory in that region. Similarly, if no memory regions have
8566 been defined, @value{GDBN} uses the default attributes when accessing
8569 When a memory region is defined, it is given a number to identify it;
8570 to enable, disable, or remove a memory region, you specify that number.
8574 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8575 Define a memory region bounded by @var{lower} and @var{upper} with
8576 attributes @var{attributes}@dots{}, and add it to the list of regions
8577 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8578 case: it is treated as the target's maximum memory address.
8579 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8582 Discard any user changes to the memory regions and use target-supplied
8583 regions, if available, or no regions if the target does not support.
8586 @item delete mem @var{nums}@dots{}
8587 Remove memory regions @var{nums}@dots{} from the list of regions
8588 monitored by @value{GDBN}.
8591 @item disable mem @var{nums}@dots{}
8592 Disable monitoring of memory regions @var{nums}@dots{}.
8593 A disabled memory region is not forgotten.
8594 It may be enabled again later.
8597 @item enable mem @var{nums}@dots{}
8598 Enable monitoring of memory regions @var{nums}@dots{}.
8602 Print a table of all defined memory regions, with the following columns
8606 @item Memory Region Number
8607 @item Enabled or Disabled.
8608 Enabled memory regions are marked with @samp{y}.
8609 Disabled memory regions are marked with @samp{n}.
8612 The address defining the inclusive lower bound of the memory region.
8615 The address defining the exclusive upper bound of the memory region.
8618 The list of attributes set for this memory region.
8623 @subsection Attributes
8625 @subsubsection Memory Access Mode
8626 The access mode attributes set whether @value{GDBN} may make read or
8627 write accesses to a memory region.
8629 While these attributes prevent @value{GDBN} from performing invalid
8630 memory accesses, they do nothing to prevent the target system, I/O DMA,
8631 etc.@: from accessing memory.
8635 Memory is read only.
8637 Memory is write only.
8639 Memory is read/write. This is the default.
8642 @subsubsection Memory Access Size
8643 The access size attribute tells @value{GDBN} to use specific sized
8644 accesses in the memory region. Often memory mapped device registers
8645 require specific sized accesses. If no access size attribute is
8646 specified, @value{GDBN} may use accesses of any size.
8650 Use 8 bit memory accesses.
8652 Use 16 bit memory accesses.
8654 Use 32 bit memory accesses.
8656 Use 64 bit memory accesses.
8659 @c @subsubsection Hardware/Software Breakpoints
8660 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8661 @c will use hardware or software breakpoints for the internal breakpoints
8662 @c used by the step, next, finish, until, etc. commands.
8666 @c Always use hardware breakpoints
8667 @c @item swbreak (default)
8670 @subsubsection Data Cache
8671 The data cache attributes set whether @value{GDBN} will cache target
8672 memory. While this generally improves performance by reducing debug
8673 protocol overhead, it can lead to incorrect results because @value{GDBN}
8674 does not know about volatile variables or memory mapped device
8679 Enable @value{GDBN} to cache target memory.
8681 Disable @value{GDBN} from caching target memory. This is the default.
8684 @subsection Memory Access Checking
8685 @value{GDBN} can be instructed to refuse accesses to memory that is
8686 not explicitly described. This can be useful if accessing such
8687 regions has undesired effects for a specific target, or to provide
8688 better error checking. The following commands control this behaviour.
8691 @kindex set mem inaccessible-by-default
8692 @item set mem inaccessible-by-default [on|off]
8693 If @code{on} is specified, make @value{GDBN} treat memory not
8694 explicitly described by the memory ranges as non-existent and refuse accesses
8695 to such memory. The checks are only performed if there's at least one
8696 memory range defined. If @code{off} is specified, make @value{GDBN}
8697 treat the memory not explicitly described by the memory ranges as RAM.
8698 The default value is @code{on}.
8699 @kindex show mem inaccessible-by-default
8700 @item show mem inaccessible-by-default
8701 Show the current handling of accesses to unknown memory.
8705 @c @subsubsection Memory Write Verification
8706 @c The memory write verification attributes set whether @value{GDBN}
8707 @c will re-reads data after each write to verify the write was successful.
8711 @c @item noverify (default)
8714 @node Dump/Restore Files
8715 @section Copy Between Memory and a File
8716 @cindex dump/restore files
8717 @cindex append data to a file
8718 @cindex dump data to a file
8719 @cindex restore data from a file
8721 You can use the commands @code{dump}, @code{append}, and
8722 @code{restore} to copy data between target memory and a file. The
8723 @code{dump} and @code{append} commands write data to a file, and the
8724 @code{restore} command reads data from a file back into the inferior's
8725 memory. Files may be in binary, Motorola S-record, Intel hex, or
8726 Tektronix Hex format; however, @value{GDBN} can only append to binary
8732 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8733 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8734 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8735 or the value of @var{expr}, to @var{filename} in the given format.
8737 The @var{format} parameter may be any one of:
8744 Motorola S-record format.
8746 Tektronix Hex format.
8749 @value{GDBN} uses the same definitions of these formats as the
8750 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8751 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8755 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8756 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8757 Append the contents of memory from @var{start_addr} to @var{end_addr},
8758 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8759 (@value{GDBN} can only append data to files in raw binary form.)
8762 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8763 Restore the contents of file @var{filename} into memory. The
8764 @code{restore} command can automatically recognize any known @sc{bfd}
8765 file format, except for raw binary. To restore a raw binary file you
8766 must specify the optional keyword @code{binary} after the filename.
8768 If @var{bias} is non-zero, its value will be added to the addresses
8769 contained in the file. Binary files always start at address zero, so
8770 they will be restored at address @var{bias}. Other bfd files have
8771 a built-in location; they will be restored at offset @var{bias}
8774 If @var{start} and/or @var{end} are non-zero, then only data between
8775 file offset @var{start} and file offset @var{end} will be restored.
8776 These offsets are relative to the addresses in the file, before
8777 the @var{bias} argument is applied.
8781 @node Core File Generation
8782 @section How to Produce a Core File from Your Program
8783 @cindex dump core from inferior
8785 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8786 image of a running process and its process status (register values
8787 etc.). Its primary use is post-mortem debugging of a program that
8788 crashed while it ran outside a debugger. A program that crashes
8789 automatically produces a core file, unless this feature is disabled by
8790 the user. @xref{Files}, for information on invoking @value{GDBN} in
8791 the post-mortem debugging mode.
8793 Occasionally, you may wish to produce a core file of the program you
8794 are debugging in order to preserve a snapshot of its state.
8795 @value{GDBN} has a special command for that.
8799 @kindex generate-core-file
8800 @item generate-core-file [@var{file}]
8801 @itemx gcore [@var{file}]
8802 Produce a core dump of the inferior process. The optional argument
8803 @var{file} specifies the file name where to put the core dump. If not
8804 specified, the file name defaults to @file{core.@var{pid}}, where
8805 @var{pid} is the inferior process ID.
8807 Note that this command is implemented only for some systems (as of
8808 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8811 @node Character Sets
8812 @section Character Sets
8813 @cindex character sets
8815 @cindex translating between character sets
8816 @cindex host character set
8817 @cindex target character set
8819 If the program you are debugging uses a different character set to
8820 represent characters and strings than the one @value{GDBN} uses itself,
8821 @value{GDBN} can automatically translate between the character sets for
8822 you. The character set @value{GDBN} uses we call the @dfn{host
8823 character set}; the one the inferior program uses we call the
8824 @dfn{target character set}.
8826 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8827 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8828 remote protocol (@pxref{Remote Debugging}) to debug a program
8829 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8830 then the host character set is Latin-1, and the target character set is
8831 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8832 target-charset EBCDIC-US}, then @value{GDBN} translates between
8833 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8834 character and string literals in expressions.
8836 @value{GDBN} has no way to automatically recognize which character set
8837 the inferior program uses; you must tell it, using the @code{set
8838 target-charset} command, described below.
8840 Here are the commands for controlling @value{GDBN}'s character set
8844 @item set target-charset @var{charset}
8845 @kindex set target-charset
8846 Set the current target character set to @var{charset}. To display the
8847 list of supported target character sets, type
8848 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8850 @item set host-charset @var{charset}
8851 @kindex set host-charset
8852 Set the current host character set to @var{charset}.
8854 By default, @value{GDBN} uses a host character set appropriate to the
8855 system it is running on; you can override that default using the
8856 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8857 automatically determine the appropriate host character set. In this
8858 case, @value{GDBN} uses @samp{UTF-8}.
8860 @value{GDBN} can only use certain character sets as its host character
8861 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8862 @value{GDBN} will list the host character sets it supports.
8864 @item set charset @var{charset}
8866 Set the current host and target character sets to @var{charset}. As
8867 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8868 @value{GDBN} will list the names of the character sets that can be used
8869 for both host and target.
8872 @kindex show charset
8873 Show the names of the current host and target character sets.
8875 @item show host-charset
8876 @kindex show host-charset
8877 Show the name of the current host character set.
8879 @item show target-charset
8880 @kindex show target-charset
8881 Show the name of the current target character set.
8883 @item set target-wide-charset @var{charset}
8884 @kindex set target-wide-charset
8885 Set the current target's wide character set to @var{charset}. This is
8886 the character set used by the target's @code{wchar_t} type. To
8887 display the list of supported wide character sets, type
8888 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8890 @item show target-wide-charset
8891 @kindex show target-wide-charset
8892 Show the name of the current target's wide character set.
8895 Here is an example of @value{GDBN}'s character set support in action.
8896 Assume that the following source code has been placed in the file
8897 @file{charset-test.c}:
8903 = @{72, 101, 108, 108, 111, 44, 32, 119,
8904 111, 114, 108, 100, 33, 10, 0@};
8905 char ibm1047_hello[]
8906 = @{200, 133, 147, 147, 150, 107, 64, 166,
8907 150, 153, 147, 132, 90, 37, 0@};
8911 printf ("Hello, world!\n");
8915 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8916 containing the string @samp{Hello, world!} followed by a newline,
8917 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8919 We compile the program, and invoke the debugger on it:
8922 $ gcc -g charset-test.c -o charset-test
8923 $ gdb -nw charset-test
8924 GNU gdb 2001-12-19-cvs
8925 Copyright 2001 Free Software Foundation, Inc.
8930 We can use the @code{show charset} command to see what character sets
8931 @value{GDBN} is currently using to interpret and display characters and
8935 (@value{GDBP}) show charset
8936 The current host and target character set is `ISO-8859-1'.
8940 For the sake of printing this manual, let's use @sc{ascii} as our
8941 initial character set:
8943 (@value{GDBP}) set charset ASCII
8944 (@value{GDBP}) show charset
8945 The current host and target character set is `ASCII'.
8949 Let's assume that @sc{ascii} is indeed the correct character set for our
8950 host system --- in other words, let's assume that if @value{GDBN} prints
8951 characters using the @sc{ascii} character set, our terminal will display
8952 them properly. Since our current target character set is also
8953 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8956 (@value{GDBP}) print ascii_hello
8957 $1 = 0x401698 "Hello, world!\n"
8958 (@value{GDBP}) print ascii_hello[0]
8963 @value{GDBN} uses the target character set for character and string
8964 literals you use in expressions:
8967 (@value{GDBP}) print '+'
8972 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8975 @value{GDBN} relies on the user to tell it which character set the
8976 target program uses. If we print @code{ibm1047_hello} while our target
8977 character set is still @sc{ascii}, we get jibberish:
8980 (@value{GDBP}) print ibm1047_hello
8981 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8982 (@value{GDBP}) print ibm1047_hello[0]
8987 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8988 @value{GDBN} tells us the character sets it supports:
8991 (@value{GDBP}) set target-charset
8992 ASCII EBCDIC-US IBM1047 ISO-8859-1
8993 (@value{GDBP}) set target-charset
8996 We can select @sc{ibm1047} as our target character set, and examine the
8997 program's strings again. Now the @sc{ascii} string is wrong, but
8998 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8999 target character set, @sc{ibm1047}, to the host character set,
9000 @sc{ascii}, and they display correctly:
9003 (@value{GDBP}) set target-charset IBM1047
9004 (@value{GDBP}) show charset
9005 The current host character set is `ASCII'.
9006 The current target character set is `IBM1047'.
9007 (@value{GDBP}) print ascii_hello
9008 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9009 (@value{GDBP}) print ascii_hello[0]
9011 (@value{GDBP}) print ibm1047_hello
9012 $8 = 0x4016a8 "Hello, world!\n"
9013 (@value{GDBP}) print ibm1047_hello[0]
9018 As above, @value{GDBN} uses the target character set for character and
9019 string literals you use in expressions:
9022 (@value{GDBP}) print '+'
9027 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9030 @node Caching Remote Data
9031 @section Caching Data of Remote Targets
9032 @cindex caching data of remote targets
9034 @value{GDBN} caches data exchanged between the debugger and a
9035 remote target (@pxref{Remote Debugging}). Such caching generally improves
9036 performance, because it reduces the overhead of the remote protocol by
9037 bundling memory reads and writes into large chunks. Unfortunately, simply
9038 caching everything would lead to incorrect results, since @value{GDBN}
9039 does not necessarily know anything about volatile values, memory-mapped I/O
9040 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9041 memory can be changed @emph{while} a gdb command is executing.
9042 Therefore, by default, @value{GDBN} only caches data
9043 known to be on the stack@footnote{In non-stop mode, it is moderately
9044 rare for a running thread to modify the stack of a stopped thread
9045 in a way that would interfere with a backtrace, and caching of
9046 stack reads provides a significant speed up of remote backtraces.}.
9047 Other regions of memory can be explicitly marked as
9048 cacheable; see @pxref{Memory Region Attributes}.
9051 @kindex set remotecache
9052 @item set remotecache on
9053 @itemx set remotecache off
9054 This option no longer does anything; it exists for compatibility
9057 @kindex show remotecache
9058 @item show remotecache
9059 Show the current state of the obsolete remotecache flag.
9061 @kindex set stack-cache
9062 @item set stack-cache on
9063 @itemx set stack-cache off
9064 Enable or disable caching of stack accesses. When @code{ON}, use
9065 caching. By default, this option is @code{ON}.
9067 @kindex show stack-cache
9068 @item show stack-cache
9069 Show the current state of data caching for memory accesses.
9072 @item info dcache @r{[}line@r{]}
9073 Print the information about the data cache performance. The
9074 information displayed includes the dcache width and depth, and for
9075 each cache line, its number, address, and how many times it was
9076 referenced. This command is useful for debugging the data cache
9079 If a line number is specified, the contents of that line will be
9083 @node Searching Memory
9084 @section Search Memory
9085 @cindex searching memory
9087 Memory can be searched for a particular sequence of bytes with the
9088 @code{find} command.
9092 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9093 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9094 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9095 etc. The search begins at address @var{start_addr} and continues for either
9096 @var{len} bytes or through to @var{end_addr} inclusive.
9099 @var{s} and @var{n} are optional parameters.
9100 They may be specified in either order, apart or together.
9103 @item @var{s}, search query size
9104 The size of each search query value.
9110 halfwords (two bytes)
9114 giant words (eight bytes)
9117 All values are interpreted in the current language.
9118 This means, for example, that if the current source language is C/C@t{++}
9119 then searching for the string ``hello'' includes the trailing '\0'.
9121 If the value size is not specified, it is taken from the
9122 value's type in the current language.
9123 This is useful when one wants to specify the search
9124 pattern as a mixture of types.
9125 Note that this means, for example, that in the case of C-like languages
9126 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9127 which is typically four bytes.
9129 @item @var{n}, maximum number of finds
9130 The maximum number of matches to print. The default is to print all finds.
9133 You can use strings as search values. Quote them with double-quotes
9135 The string value is copied into the search pattern byte by byte,
9136 regardless of the endianness of the target and the size specification.
9138 The address of each match found is printed as well as a count of the
9139 number of matches found.
9141 The address of the last value found is stored in convenience variable
9143 A count of the number of matches is stored in @samp{$numfound}.
9145 For example, if stopped at the @code{printf} in this function:
9151 static char hello[] = "hello-hello";
9152 static struct @{ char c; short s; int i; @}
9153 __attribute__ ((packed)) mixed
9154 = @{ 'c', 0x1234, 0x87654321 @};
9155 printf ("%s\n", hello);
9160 you get during debugging:
9163 (gdb) find &hello[0], +sizeof(hello), "hello"
9164 0x804956d <hello.1620+6>
9166 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9167 0x8049567 <hello.1620>
9168 0x804956d <hello.1620+6>
9170 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9171 0x8049567 <hello.1620>
9173 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9174 0x8049560 <mixed.1625>
9176 (gdb) print $numfound
9179 $2 = (void *) 0x8049560
9182 @node Optimized Code
9183 @chapter Debugging Optimized Code
9184 @cindex optimized code, debugging
9185 @cindex debugging optimized code
9187 Almost all compilers support optimization. With optimization
9188 disabled, the compiler generates assembly code that corresponds
9189 directly to your source code, in a simplistic way. As the compiler
9190 applies more powerful optimizations, the generated assembly code
9191 diverges from your original source code. With help from debugging
9192 information generated by the compiler, @value{GDBN} can map from
9193 the running program back to constructs from your original source.
9195 @value{GDBN} is more accurate with optimization disabled. If you
9196 can recompile without optimization, it is easier to follow the
9197 progress of your program during debugging. But, there are many cases
9198 where you may need to debug an optimized version.
9200 When you debug a program compiled with @samp{-g -O}, remember that the
9201 optimizer has rearranged your code; the debugger shows you what is
9202 really there. Do not be too surprised when the execution path does not
9203 exactly match your source file! An extreme example: if you define a
9204 variable, but never use it, @value{GDBN} never sees that
9205 variable---because the compiler optimizes it out of existence.
9207 Some things do not work as well with @samp{-g -O} as with just
9208 @samp{-g}, particularly on machines with instruction scheduling. If in
9209 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9210 please report it to us as a bug (including a test case!).
9211 @xref{Variables}, for more information about debugging optimized code.
9214 * Inline Functions:: How @value{GDBN} presents inlining
9217 @node Inline Functions
9218 @section Inline Functions
9219 @cindex inline functions, debugging
9221 @dfn{Inlining} is an optimization that inserts a copy of the function
9222 body directly at each call site, instead of jumping to a shared
9223 routine. @value{GDBN} displays inlined functions just like
9224 non-inlined functions. They appear in backtraces. You can view their
9225 arguments and local variables, step into them with @code{step}, skip
9226 them with @code{next}, and escape from them with @code{finish}.
9227 You can check whether a function was inlined by using the
9228 @code{info frame} command.
9230 For @value{GDBN} to support inlined functions, the compiler must
9231 record information about inlining in the debug information ---
9232 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9233 other compilers do also. @value{GDBN} only supports inlined functions
9234 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9235 do not emit two required attributes (@samp{DW_AT_call_file} and
9236 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9237 function calls with earlier versions of @value{NGCC}. It instead
9238 displays the arguments and local variables of inlined functions as
9239 local variables in the caller.
9241 The body of an inlined function is directly included at its call site;
9242 unlike a non-inlined function, there are no instructions devoted to
9243 the call. @value{GDBN} still pretends that the call site and the
9244 start of the inlined function are different instructions. Stepping to
9245 the call site shows the call site, and then stepping again shows
9246 the first line of the inlined function, even though no additional
9247 instructions are executed.
9249 This makes source-level debugging much clearer; you can see both the
9250 context of the call and then the effect of the call. Only stepping by
9251 a single instruction using @code{stepi} or @code{nexti} does not do
9252 this; single instruction steps always show the inlined body.
9254 There are some ways that @value{GDBN} does not pretend that inlined
9255 function calls are the same as normal calls:
9259 You cannot set breakpoints on inlined functions. @value{GDBN}
9260 either reports that there is no symbol with that name, or else sets the
9261 breakpoint only on non-inlined copies of the function. This limitation
9262 will be removed in a future version of @value{GDBN}; until then,
9263 set a breakpoint by line number on the first line of the inlined
9267 Setting breakpoints at the call site of an inlined function may not
9268 work, because the call site does not contain any code. @value{GDBN}
9269 may incorrectly move the breakpoint to the next line of the enclosing
9270 function, after the call. This limitation will be removed in a future
9271 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9272 or inside the inlined function instead.
9275 @value{GDBN} cannot locate the return value of inlined calls after
9276 using the @code{finish} command. This is a limitation of compiler-generated
9277 debugging information; after @code{finish}, you can step to the next line
9278 and print a variable where your program stored the return value.
9284 @chapter C Preprocessor Macros
9286 Some languages, such as C and C@t{++}, provide a way to define and invoke
9287 ``preprocessor macros'' which expand into strings of tokens.
9288 @value{GDBN} can evaluate expressions containing macro invocations, show
9289 the result of macro expansion, and show a macro's definition, including
9290 where it was defined.
9292 You may need to compile your program specially to provide @value{GDBN}
9293 with information about preprocessor macros. Most compilers do not
9294 include macros in their debugging information, even when you compile
9295 with the @option{-g} flag. @xref{Compilation}.
9297 A program may define a macro at one point, remove that definition later,
9298 and then provide a different definition after that. Thus, at different
9299 points in the program, a macro may have different definitions, or have
9300 no definition at all. If there is a current stack frame, @value{GDBN}
9301 uses the macros in scope at that frame's source code line. Otherwise,
9302 @value{GDBN} uses the macros in scope at the current listing location;
9305 Whenever @value{GDBN} evaluates an expression, it always expands any
9306 macro invocations present in the expression. @value{GDBN} also provides
9307 the following commands for working with macros explicitly.
9311 @kindex macro expand
9312 @cindex macro expansion, showing the results of preprocessor
9313 @cindex preprocessor macro expansion, showing the results of
9314 @cindex expanding preprocessor macros
9315 @item macro expand @var{expression}
9316 @itemx macro exp @var{expression}
9317 Show the results of expanding all preprocessor macro invocations in
9318 @var{expression}. Since @value{GDBN} simply expands macros, but does
9319 not parse the result, @var{expression} need not be a valid expression;
9320 it can be any string of tokens.
9323 @item macro expand-once @var{expression}
9324 @itemx macro exp1 @var{expression}
9325 @cindex expand macro once
9326 @i{(This command is not yet implemented.)} Show the results of
9327 expanding those preprocessor macro invocations that appear explicitly in
9328 @var{expression}. Macro invocations appearing in that expansion are
9329 left unchanged. This command allows you to see the effect of a
9330 particular macro more clearly, without being confused by further
9331 expansions. Since @value{GDBN} simply expands macros, but does not
9332 parse the result, @var{expression} need not be a valid expression; it
9333 can be any string of tokens.
9336 @cindex macro definition, showing
9337 @cindex definition, showing a macro's
9338 @item info macro @var{macro}
9339 Show the definition of the macro named @var{macro}, and describe the
9340 source location or compiler command-line where that definition was established.
9342 @kindex macro define
9343 @cindex user-defined macros
9344 @cindex defining macros interactively
9345 @cindex macros, user-defined
9346 @item macro define @var{macro} @var{replacement-list}
9347 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9348 Introduce a definition for a preprocessor macro named @var{macro},
9349 invocations of which are replaced by the tokens given in
9350 @var{replacement-list}. The first form of this command defines an
9351 ``object-like'' macro, which takes no arguments; the second form
9352 defines a ``function-like'' macro, which takes the arguments given in
9355 A definition introduced by this command is in scope in every
9356 expression evaluated in @value{GDBN}, until it is removed with the
9357 @code{macro undef} command, described below. The definition overrides
9358 all definitions for @var{macro} present in the program being debugged,
9359 as well as any previous user-supplied definition.
9362 @item macro undef @var{macro}
9363 Remove any user-supplied definition for the macro named @var{macro}.
9364 This command only affects definitions provided with the @code{macro
9365 define} command, described above; it cannot remove definitions present
9366 in the program being debugged.
9370 List all the macros defined using the @code{macro define} command.
9373 @cindex macros, example of debugging with
9374 Here is a transcript showing the above commands in action. First, we
9375 show our source files:
9383 #define ADD(x) (M + x)
9388 printf ("Hello, world!\n");
9390 printf ("We're so creative.\n");
9392 printf ("Goodbye, world!\n");
9399 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9400 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9401 compiler includes information about preprocessor macros in the debugging
9405 $ gcc -gdwarf-2 -g3 sample.c -o sample
9409 Now, we start @value{GDBN} on our sample program:
9413 GNU gdb 2002-05-06-cvs
9414 Copyright 2002 Free Software Foundation, Inc.
9415 GDB is free software, @dots{}
9419 We can expand macros and examine their definitions, even when the
9420 program is not running. @value{GDBN} uses the current listing position
9421 to decide which macro definitions are in scope:
9424 (@value{GDBP}) list main
9427 5 #define ADD(x) (M + x)
9432 10 printf ("Hello, world!\n");
9434 12 printf ("We're so creative.\n");
9435 (@value{GDBP}) info macro ADD
9436 Defined at /home/jimb/gdb/macros/play/sample.c:5
9437 #define ADD(x) (M + x)
9438 (@value{GDBP}) info macro Q
9439 Defined at /home/jimb/gdb/macros/play/sample.h:1
9440 included at /home/jimb/gdb/macros/play/sample.c:2
9442 (@value{GDBP}) macro expand ADD(1)
9443 expands to: (42 + 1)
9444 (@value{GDBP}) macro expand-once ADD(1)
9445 expands to: once (M + 1)
9449 In the example above, note that @code{macro expand-once} expands only
9450 the macro invocation explicit in the original text --- the invocation of
9451 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9452 which was introduced by @code{ADD}.
9454 Once the program is running, @value{GDBN} uses the macro definitions in
9455 force at the source line of the current stack frame:
9458 (@value{GDBP}) break main
9459 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9461 Starting program: /home/jimb/gdb/macros/play/sample
9463 Breakpoint 1, main () at sample.c:10
9464 10 printf ("Hello, world!\n");
9468 At line 10, the definition of the macro @code{N} at line 9 is in force:
9471 (@value{GDBP}) info macro N
9472 Defined at /home/jimb/gdb/macros/play/sample.c:9
9474 (@value{GDBP}) macro expand N Q M
9476 (@value{GDBP}) print N Q M
9481 As we step over directives that remove @code{N}'s definition, and then
9482 give it a new definition, @value{GDBN} finds the definition (or lack
9483 thereof) in force at each point:
9488 12 printf ("We're so creative.\n");
9489 (@value{GDBP}) info macro N
9490 The symbol `N' has no definition as a C/C++ preprocessor macro
9491 at /home/jimb/gdb/macros/play/sample.c:12
9494 14 printf ("Goodbye, world!\n");
9495 (@value{GDBP}) info macro N
9496 Defined at /home/jimb/gdb/macros/play/sample.c:13
9498 (@value{GDBP}) macro expand N Q M
9499 expands to: 1729 < 42
9500 (@value{GDBP}) print N Q M
9505 In addition to source files, macros can be defined on the compilation command
9506 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9507 such a way, @value{GDBN} displays the location of their definition as line zero
9508 of the source file submitted to the compiler.
9511 (@value{GDBP}) info macro __STDC__
9512 Defined at /home/jimb/gdb/macros/play/sample.c:0
9519 @chapter Tracepoints
9520 @c This chapter is based on the documentation written by Michael
9521 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9524 In some applications, it is not feasible for the debugger to interrupt
9525 the program's execution long enough for the developer to learn
9526 anything helpful about its behavior. If the program's correctness
9527 depends on its real-time behavior, delays introduced by a debugger
9528 might cause the program to change its behavior drastically, or perhaps
9529 fail, even when the code itself is correct. It is useful to be able
9530 to observe the program's behavior without interrupting it.
9532 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9533 specify locations in the program, called @dfn{tracepoints}, and
9534 arbitrary expressions to evaluate when those tracepoints are reached.
9535 Later, using the @code{tfind} command, you can examine the values
9536 those expressions had when the program hit the tracepoints. The
9537 expressions may also denote objects in memory---structures or arrays,
9538 for example---whose values @value{GDBN} should record; while visiting
9539 a particular tracepoint, you may inspect those objects as if they were
9540 in memory at that moment. However, because @value{GDBN} records these
9541 values without interacting with you, it can do so quickly and
9542 unobtrusively, hopefully not disturbing the program's behavior.
9544 The tracepoint facility is currently available only for remote
9545 targets. @xref{Targets}. In addition, your remote target must know
9546 how to collect trace data. This functionality is implemented in the
9547 remote stub; however, none of the stubs distributed with @value{GDBN}
9548 support tracepoints as of this writing. The format of the remote
9549 packets used to implement tracepoints are described in @ref{Tracepoint
9552 It is also possible to get trace data from a file, in a manner reminiscent
9553 of corefiles; you specify the filename, and use @code{tfind} to search
9554 through the file. @xref{Trace Files}, for more details.
9556 This chapter describes the tracepoint commands and features.
9560 * Analyze Collected Data::
9561 * Tracepoint Variables::
9565 @node Set Tracepoints
9566 @section Commands to Set Tracepoints
9568 Before running such a @dfn{trace experiment}, an arbitrary number of
9569 tracepoints can be set. A tracepoint is actually a special type of
9570 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9571 standard breakpoint commands. For instance, as with breakpoints,
9572 tracepoint numbers are successive integers starting from one, and many
9573 of the commands associated with tracepoints take the tracepoint number
9574 as their argument, to identify which tracepoint to work on.
9576 For each tracepoint, you can specify, in advance, some arbitrary set
9577 of data that you want the target to collect in the trace buffer when
9578 it hits that tracepoint. The collected data can include registers,
9579 local variables, or global data. Later, you can use @value{GDBN}
9580 commands to examine the values these data had at the time the
9583 Tracepoints do not support every breakpoint feature. Ignore counts on
9584 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9585 commands when they are hit. Tracepoints may not be thread-specific
9588 @cindex fast tracepoints
9589 Some targets may support @dfn{fast tracepoints}, which are inserted in
9590 a different way (such as with a jump instead of a trap), that is
9591 faster but possibly restricted in where they may be installed.
9593 @code{gdbserver} supports tracepoints on some target systems.
9594 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9596 This section describes commands to set tracepoints and associated
9597 conditions and actions.
9600 * Create and Delete Tracepoints::
9601 * Enable and Disable Tracepoints::
9602 * Tracepoint Passcounts::
9603 * Tracepoint Conditions::
9604 * Trace State Variables::
9605 * Tracepoint Actions::
9606 * Listing Tracepoints::
9607 * Starting and Stopping Trace Experiments::
9608 * Tracepoint Restrictions::
9611 @node Create and Delete Tracepoints
9612 @subsection Create and Delete Tracepoints
9615 @cindex set tracepoint
9617 @item trace @var{location}
9618 The @code{trace} command is very similar to the @code{break} command.
9619 Its argument @var{location} can be a source line, a function name, or
9620 an address in the target program. @xref{Specify Location}. The
9621 @code{trace} command defines a tracepoint, which is a point in the
9622 target program where the debugger will briefly stop, collect some
9623 data, and then allow the program to continue. Setting a tracepoint or
9624 changing its actions doesn't take effect until the next @code{tstart}
9625 command, and once a trace experiment is running, further changes will
9626 not have any effect until the next trace experiment starts.
9628 Here are some examples of using the @code{trace} command:
9631 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9633 (@value{GDBP}) @b{trace +2} // 2 lines forward
9635 (@value{GDBP}) @b{trace my_function} // first source line of function
9637 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9639 (@value{GDBP}) @b{trace *0x2117c4} // an address
9643 You can abbreviate @code{trace} as @code{tr}.
9645 @item trace @var{location} if @var{cond}
9646 Set a tracepoint with condition @var{cond}; evaluate the expression
9647 @var{cond} each time the tracepoint is reached, and collect data only
9648 if the value is nonzero---that is, if @var{cond} evaluates as true.
9649 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9650 information on tracepoint conditions.
9652 @item ftrace @var{location} [ if @var{cond} ]
9653 @cindex set fast tracepoint
9655 The @code{ftrace} command sets a fast tracepoint. For targets that
9656 support them, fast tracepoints will use a more efficient but possibly
9657 less general technique to trigger data collection, such as a jump
9658 instruction instead of a trap, or some sort of hardware support. It
9659 may not be possible to create a fast tracepoint at the desired
9660 location, in which case the command will exit with an explanatory
9663 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9667 @cindex last tracepoint number
9668 @cindex recent tracepoint number
9669 @cindex tracepoint number
9670 The convenience variable @code{$tpnum} records the tracepoint number
9671 of the most recently set tracepoint.
9673 @kindex delete tracepoint
9674 @cindex tracepoint deletion
9675 @item delete tracepoint @r{[}@var{num}@r{]}
9676 Permanently delete one or more tracepoints. With no argument, the
9677 default is to delete all tracepoints. Note that the regular
9678 @code{delete} command can remove tracepoints also.
9683 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9685 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9689 You can abbreviate this command as @code{del tr}.
9692 @node Enable and Disable Tracepoints
9693 @subsection Enable and Disable Tracepoints
9695 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9698 @kindex disable tracepoint
9699 @item disable tracepoint @r{[}@var{num}@r{]}
9700 Disable tracepoint @var{num}, or all tracepoints if no argument
9701 @var{num} is given. A disabled tracepoint will have no effect during
9702 the next trace experiment, but it is not forgotten. You can re-enable
9703 a disabled tracepoint using the @code{enable tracepoint} command.
9705 @kindex enable tracepoint
9706 @item enable tracepoint @r{[}@var{num}@r{]}
9707 Enable tracepoint @var{num}, or all tracepoints. The enabled
9708 tracepoints will become effective the next time a trace experiment is
9712 @node Tracepoint Passcounts
9713 @subsection Tracepoint Passcounts
9717 @cindex tracepoint pass count
9718 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9719 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9720 automatically stop a trace experiment. If a tracepoint's passcount is
9721 @var{n}, then the trace experiment will be automatically stopped on
9722 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9723 @var{num} is not specified, the @code{passcount} command sets the
9724 passcount of the most recently defined tracepoint. If no passcount is
9725 given, the trace experiment will run until stopped explicitly by the
9731 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9732 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9734 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9735 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9736 (@value{GDBP}) @b{trace foo}
9737 (@value{GDBP}) @b{pass 3}
9738 (@value{GDBP}) @b{trace bar}
9739 (@value{GDBP}) @b{pass 2}
9740 (@value{GDBP}) @b{trace baz}
9741 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9742 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9743 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9744 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9748 @node Tracepoint Conditions
9749 @subsection Tracepoint Conditions
9750 @cindex conditional tracepoints
9751 @cindex tracepoint conditions
9753 The simplest sort of tracepoint collects data every time your program
9754 reaches a specified place. You can also specify a @dfn{condition} for
9755 a tracepoint. A condition is just a Boolean expression in your
9756 programming language (@pxref{Expressions, ,Expressions}). A
9757 tracepoint with a condition evaluates the expression each time your
9758 program reaches it, and data collection happens only if the condition
9761 Tracepoint conditions can be specified when a tracepoint is set, by
9762 using @samp{if} in the arguments to the @code{trace} command.
9763 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9764 also be set or changed at any time with the @code{condition} command,
9765 just as with breakpoints.
9767 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9768 the conditional expression itself. Instead, @value{GDBN} encodes the
9769 expression into an agent expression (@pxref{Agent Expressions}
9770 suitable for execution on the target, independently of @value{GDBN}.
9771 Global variables become raw memory locations, locals become stack
9772 accesses, and so forth.
9774 For instance, suppose you have a function that is usually called
9775 frequently, but should not be called after an error has occurred. You
9776 could use the following tracepoint command to collect data about calls
9777 of that function that happen while the error code is propagating
9778 through the program; an unconditional tracepoint could end up
9779 collecting thousands of useless trace frames that you would have to
9783 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9786 @node Trace State Variables
9787 @subsection Trace State Variables
9788 @cindex trace state variables
9790 A @dfn{trace state variable} is a special type of variable that is
9791 created and managed by target-side code. The syntax is the same as
9792 that for GDB's convenience variables (a string prefixed with ``$''),
9793 but they are stored on the target. They must be created explicitly,
9794 using a @code{tvariable} command. They are always 64-bit signed
9797 Trace state variables are remembered by @value{GDBN}, and downloaded
9798 to the target along with tracepoint information when the trace
9799 experiment starts. There are no intrinsic limits on the number of
9800 trace state variables, beyond memory limitations of the target.
9802 @cindex convenience variables, and trace state variables
9803 Although trace state variables are managed by the target, you can use
9804 them in print commands and expressions as if they were convenience
9805 variables; @value{GDBN} will get the current value from the target
9806 while the trace experiment is running. Trace state variables share
9807 the same namespace as other ``$'' variables, which means that you
9808 cannot have trace state variables with names like @code{$23} or
9809 @code{$pc}, nor can you have a trace state variable and a convenience
9810 variable with the same name.
9814 @item tvariable $@var{name} [ = @var{expression} ]
9816 The @code{tvariable} command creates a new trace state variable named
9817 @code{$@var{name}}, and optionally gives it an initial value of
9818 @var{expression}. @var{expression} is evaluated when this command is
9819 entered; the result will be converted to an integer if possible,
9820 otherwise @value{GDBN} will report an error. A subsequent
9821 @code{tvariable} command specifying the same name does not create a
9822 variable, but instead assigns the supplied initial value to the
9823 existing variable of that name, overwriting any previous initial
9824 value. The default initial value is 0.
9826 @item info tvariables
9827 @kindex info tvariables
9828 List all the trace state variables along with their initial values.
9829 Their current values may also be displayed, if the trace experiment is
9832 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9833 @kindex delete tvariable
9834 Delete the given trace state variables, or all of them if no arguments
9839 @node Tracepoint Actions
9840 @subsection Tracepoint Action Lists
9844 @cindex tracepoint actions
9845 @item actions @r{[}@var{num}@r{]}
9846 This command will prompt for a list of actions to be taken when the
9847 tracepoint is hit. If the tracepoint number @var{num} is not
9848 specified, this command sets the actions for the one that was most
9849 recently defined (so that you can define a tracepoint and then say
9850 @code{actions} without bothering about its number). You specify the
9851 actions themselves on the following lines, one action at a time, and
9852 terminate the actions list with a line containing just @code{end}. So
9853 far, the only defined actions are @code{collect}, @code{teval}, and
9854 @code{while-stepping}.
9856 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9857 Commands, ,Breakpoint Command Lists}), except that only the defined
9858 actions are allowed; any other @value{GDBN} command is rejected.
9860 @cindex remove actions from a tracepoint
9861 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9862 and follow it immediately with @samp{end}.
9865 (@value{GDBP}) @b{collect @var{data}} // collect some data
9867 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9869 (@value{GDBP}) @b{end} // signals the end of actions.
9872 In the following example, the action list begins with @code{collect}
9873 commands indicating the things to be collected when the tracepoint is
9874 hit. Then, in order to single-step and collect additional data
9875 following the tracepoint, a @code{while-stepping} command is used,
9876 followed by the list of things to be collected after each step in a
9877 sequence of single steps. The @code{while-stepping} command is
9878 terminated by its own separate @code{end} command. Lastly, the action
9879 list is terminated by an @code{end} command.
9882 (@value{GDBP}) @b{trace foo}
9883 (@value{GDBP}) @b{actions}
9884 Enter actions for tracepoint 1, one per line:
9888 > collect $pc, arr[i]
9893 @kindex collect @r{(tracepoints)}
9894 @item collect @var{expr1}, @var{expr2}, @dots{}
9895 Collect values of the given expressions when the tracepoint is hit.
9896 This command accepts a comma-separated list of any valid expressions.
9897 In addition to global, static, or local variables, the following
9898 special arguments are supported:
9902 collect all registers
9905 collect all function arguments
9908 collect all local variables.
9911 You can give several consecutive @code{collect} commands, each one
9912 with a single argument, or one @code{collect} command with several
9913 arguments separated by commas; the effect is the same.
9915 The command @code{info scope} (@pxref{Symbols, info scope}) is
9916 particularly useful for figuring out what data to collect.
9918 @kindex teval @r{(tracepoints)}
9919 @item teval @var{expr1}, @var{expr2}, @dots{}
9920 Evaluate the given expressions when the tracepoint is hit. This
9921 command accepts a comma-separated list of expressions. The results
9922 are discarded, so this is mainly useful for assigning values to trace
9923 state variables (@pxref{Trace State Variables}) without adding those
9924 values to the trace buffer, as would be the case if the @code{collect}
9927 @kindex while-stepping @r{(tracepoints)}
9928 @item while-stepping @var{n}
9929 Perform @var{n} single-step instruction traces after the tracepoint,
9930 collecting new data after each step. The @code{while-stepping}
9931 command is followed by the list of what to collect while stepping
9932 (followed by its own @code{end} command):
9936 > collect $regs, myglobal
9942 Note that @code{$pc} is not automatically collected by
9943 @code{while-stepping}; you need to explicitly collect that register if
9944 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9947 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9948 @kindex set default-collect
9949 @cindex default collection action
9950 This variable is a list of expressions to collect at each tracepoint
9951 hit. It is effectively an additional @code{collect} action prepended
9952 to every tracepoint action list. The expressions are parsed
9953 individually for each tracepoint, so for instance a variable named
9954 @code{xyz} may be interpreted as a global for one tracepoint, and a
9955 local for another, as appropriate to the tracepoint's location.
9957 @item show default-collect
9958 @kindex show default-collect
9959 Show the list of expressions that are collected by default at each
9964 @node Listing Tracepoints
9965 @subsection Listing Tracepoints
9968 @kindex info tracepoints
9970 @cindex information about tracepoints
9971 @item info tracepoints @r{[}@var{num}@r{]}
9972 Display information about the tracepoint @var{num}. If you don't
9973 specify a tracepoint number, displays information about all the
9974 tracepoints defined so far. The format is similar to that used for
9975 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9976 command, simply restricting itself to tracepoints.
9978 A tracepoint's listing may include additional information specific to
9983 its passcount as given by the @code{passcount @var{n}} command
9987 (@value{GDBP}) @b{info trace}
9988 Num Type Disp Enb Address What
9989 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9991 collect globfoo, $regs
10000 This command can be abbreviated @code{info tp}.
10003 @node Starting and Stopping Trace Experiments
10004 @subsection Starting and Stopping Trace Experiments
10008 @cindex start a new trace experiment
10009 @cindex collected data discarded
10011 This command takes no arguments. It starts the trace experiment, and
10012 begins collecting data. This has the side effect of discarding all
10013 the data collected in the trace buffer during the previous trace
10017 @cindex stop a running trace experiment
10019 This command takes no arguments. It ends the trace experiment, and
10020 stops collecting data.
10022 @strong{Note}: a trace experiment and data collection may stop
10023 automatically if any tracepoint's passcount is reached
10024 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10027 @cindex status of trace data collection
10028 @cindex trace experiment, status of
10030 This command displays the status of the current trace data
10034 Here is an example of the commands we described so far:
10037 (@value{GDBP}) @b{trace gdb_c_test}
10038 (@value{GDBP}) @b{actions}
10039 Enter actions for tracepoint #1, one per line.
10040 > collect $regs,$locals,$args
10041 > while-stepping 11
10045 (@value{GDBP}) @b{tstart}
10046 [time passes @dots{}]
10047 (@value{GDBP}) @b{tstop}
10050 @cindex disconnected tracing
10051 You can choose to continue running the trace experiment even if
10052 @value{GDBN} disconnects from the target, voluntarily or
10053 involuntarily. For commands such as @code{detach}, the debugger will
10054 ask what you want to do with the trace. But for unexpected
10055 terminations (@value{GDBN} crash, network outage), it would be
10056 unfortunate to lose hard-won trace data, so the variable
10057 @code{disconnected-tracing} lets you decide whether the trace should
10058 continue running without @value{GDBN}.
10061 @item set disconnected-tracing on
10062 @itemx set disconnected-tracing off
10063 @kindex set disconnected-tracing
10064 Choose whether a tracing run should continue to run if @value{GDBN}
10065 has disconnected from the target. Note that @code{detach} or
10066 @code{quit} will ask you directly what to do about a running trace no
10067 matter what this variable's setting, so the variable is mainly useful
10068 for handling unexpected situations, such as loss of the network.
10070 @item show disconnected-tracing
10071 @kindex show disconnected-tracing
10072 Show the current choice for disconnected tracing.
10076 When you reconnect to the target, the trace experiment may or may not
10077 still be running; it might have filled the trace buffer in the
10078 meantime, or stopped for one of the other reasons. If it is running,
10079 it will continue after reconnection.
10081 Upon reconnection, the target will upload information about the
10082 tracepoints in effect. @value{GDBN} will then compare that
10083 information to the set of tracepoints currently defined, and attempt
10084 to match them up, allowing for the possibility that the numbers may
10085 have changed due to creation and deletion in the meantime. If one of
10086 the target's tracepoints does not match any in @value{GDBN}, the
10087 debugger will create a new tracepoint, so that you have a number with
10088 which to specify that tracepoint. This matching-up process is
10089 necessarily heuristic, and it may result in useless tracepoints being
10090 created; you may simply delete them if they are of no use.
10092 @cindex circular trace buffer
10093 If your target agent supports a @dfn{circular trace buffer}, then you
10094 can run a trace experiment indefinitely without filling the trace
10095 buffer; when space runs out, the agent deletes already-collected trace
10096 frames, oldest first, until there is enough room to continue
10097 collecting. This is especially useful if your tracepoints are being
10098 hit too often, and your trace gets terminated prematurely because the
10099 buffer is full. To ask for a circular trace buffer, simply set
10100 @samp{circular_trace_buffer} to on. You can set this at any time,
10101 including during tracing; if the agent can do it, it will change
10102 buffer handling on the fly, otherwise it will not take effect until
10106 @item set circular-trace-buffer on
10107 @itemx set circular-trace-buffer off
10108 @kindex set circular-trace-buffer
10109 Choose whether a tracing run should use a linear or circular buffer
10110 for trace data. A linear buffer will not lose any trace data, but may
10111 fill up prematurely, while a circular buffer will discard old trace
10112 data, but it will have always room for the latest tracepoint hits.
10114 @item show circular-trace-buffer
10115 @kindex show circular-trace-buffer
10116 Show the current choice for the trace buffer. Note that this may not
10117 match the agent's current buffer handling, nor is it guaranteed to
10118 match the setting that might have been in effect during a past run,
10119 for instance if you are looking at frames from a trace file.
10123 @node Tracepoint Restrictions
10124 @subsection Tracepoint Restrictions
10126 @cindex tracepoint restrictions
10127 There are a number of restrictions on the use of tracepoints. As
10128 described above, tracepoint data gathering occurs on the target
10129 without interaction from @value{GDBN}. Thus the full capabilities of
10130 the debugger are not available during data gathering, and then at data
10131 examination time, you will be limited by only having what was
10132 collected. The following items describe some common problems, but it
10133 is not exhaustive, and you may run into additional difficulties not
10139 Tracepoint expressions are intended to gather objects (lvalues). Thus
10140 the full flexibility of GDB's expression evaluator is not available.
10141 You cannot call functions, cast objects to aggregate types, access
10142 convenience variables or modify values (except by assignment to trace
10143 state variables). Some language features may implicitly call
10144 functions (for instance Objective-C fields with accessors), and therefore
10145 cannot be collected either.
10148 Collection of local variables, either individually or in bulk with
10149 @code{$locals} or @code{$args}, during @code{while-stepping} may
10150 behave erratically. The stepping action may enter a new scope (for
10151 instance by stepping into a function), or the location of the variable
10152 may change (for instance it is loaded into a register). The
10153 tracepoint data recorded uses the location information for the
10154 variables that is correct for the tracepoint location. When the
10155 tracepoint is created, it is not possible, in general, to determine
10156 where the steps of a @code{while-stepping} sequence will advance the
10157 program---particularly if a conditional branch is stepped.
10160 Collection of an incompletely-initialized or partially-destroyed object
10161 may result in something that @value{GDBN} cannot display, or displays
10162 in a misleading way.
10165 When @value{GDBN} displays a pointer to character it automatically
10166 dereferences the pointer to also display characters of the string
10167 being pointed to. However, collecting the pointer during tracing does
10168 not automatically collect the string. You need to explicitly
10169 dereference the pointer and provide size information if you want to
10170 collect not only the pointer, but the memory pointed to. For example,
10171 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10175 It is not possible to collect a complete stack backtrace at a
10176 tracepoint. Instead, you may collect the registers and a few hundred
10177 bytes from the stack pointer with something like @code{*$esp@@300}
10178 (adjust to use the name of the actual stack pointer register on your
10179 target architecture, and the amount of stack you wish to capture).
10180 Then the @code{backtrace} command will show a partial backtrace when
10181 using a trace frame. The number of stack frames that can be examined
10182 depends on the sizes of the frames in the collected stack. Note that
10183 if you ask for a block so large that it goes past the bottom of the
10184 stack, the target agent may report an error trying to read from an
10188 If you do not collect registers at a tracepoint, @value{GDBN} can
10189 infer that the value of @code{$pc} must be the same as the address of
10190 the tracepoint and use that when you are looking at a trace frame
10191 for that tracepoint. However, this cannot work if the tracepoint has
10192 multiple locations (for instance if it was set in a function that was
10193 inlined), or if it has a @code{while-stepping} loop. In those cases
10194 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10199 @node Analyze Collected Data
10200 @section Using the Collected Data
10202 After the tracepoint experiment ends, you use @value{GDBN} commands
10203 for examining the trace data. The basic idea is that each tracepoint
10204 collects a trace @dfn{snapshot} every time it is hit and another
10205 snapshot every time it single-steps. All these snapshots are
10206 consecutively numbered from zero and go into a buffer, and you can
10207 examine them later. The way you examine them is to @dfn{focus} on a
10208 specific trace snapshot. When the remote stub is focused on a trace
10209 snapshot, it will respond to all @value{GDBN} requests for memory and
10210 registers by reading from the buffer which belongs to that snapshot,
10211 rather than from @emph{real} memory or registers of the program being
10212 debugged. This means that @strong{all} @value{GDBN} commands
10213 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10214 behave as if we were currently debugging the program state as it was
10215 when the tracepoint occurred. Any requests for data that are not in
10216 the buffer will fail.
10219 * tfind:: How to select a trace snapshot
10220 * tdump:: How to display all data for a snapshot
10221 * save tracepoints:: How to save tracepoints for a future run
10225 @subsection @code{tfind @var{n}}
10228 @cindex select trace snapshot
10229 @cindex find trace snapshot
10230 The basic command for selecting a trace snapshot from the buffer is
10231 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10232 counting from zero. If no argument @var{n} is given, the next
10233 snapshot is selected.
10235 Here are the various forms of using the @code{tfind} command.
10239 Find the first snapshot in the buffer. This is a synonym for
10240 @code{tfind 0} (since 0 is the number of the first snapshot).
10243 Stop debugging trace snapshots, resume @emph{live} debugging.
10246 Same as @samp{tfind none}.
10249 No argument means find the next trace snapshot.
10252 Find the previous trace snapshot before the current one. This permits
10253 retracing earlier steps.
10255 @item tfind tracepoint @var{num}
10256 Find the next snapshot associated with tracepoint @var{num}. Search
10257 proceeds forward from the last examined trace snapshot. If no
10258 argument @var{num} is given, it means find the next snapshot collected
10259 for the same tracepoint as the current snapshot.
10261 @item tfind pc @var{addr}
10262 Find the next snapshot associated with the value @var{addr} of the
10263 program counter. Search proceeds forward from the last examined trace
10264 snapshot. If no argument @var{addr} is given, it means find the next
10265 snapshot with the same value of PC as the current snapshot.
10267 @item tfind outside @var{addr1}, @var{addr2}
10268 Find the next snapshot whose PC is outside the given range of
10269 addresses (exclusive).
10271 @item tfind range @var{addr1}, @var{addr2}
10272 Find the next snapshot whose PC is between @var{addr1} and
10273 @var{addr2} (inclusive).
10275 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10276 Find the next snapshot associated with the source line @var{n}. If
10277 the optional argument @var{file} is given, refer to line @var{n} in
10278 that source file. Search proceeds forward from the last examined
10279 trace snapshot. If no argument @var{n} is given, it means find the
10280 next line other than the one currently being examined; thus saying
10281 @code{tfind line} repeatedly can appear to have the same effect as
10282 stepping from line to line in a @emph{live} debugging session.
10285 The default arguments for the @code{tfind} commands are specifically
10286 designed to make it easy to scan through the trace buffer. For
10287 instance, @code{tfind} with no argument selects the next trace
10288 snapshot, and @code{tfind -} with no argument selects the previous
10289 trace snapshot. So, by giving one @code{tfind} command, and then
10290 simply hitting @key{RET} repeatedly you can examine all the trace
10291 snapshots in order. Or, by saying @code{tfind -} and then hitting
10292 @key{RET} repeatedly you can examine the snapshots in reverse order.
10293 The @code{tfind line} command with no argument selects the snapshot
10294 for the next source line executed. The @code{tfind pc} command with
10295 no argument selects the next snapshot with the same program counter
10296 (PC) as the current frame. The @code{tfind tracepoint} command with
10297 no argument selects the next trace snapshot collected by the same
10298 tracepoint as the current one.
10300 In addition to letting you scan through the trace buffer manually,
10301 these commands make it easy to construct @value{GDBN} scripts that
10302 scan through the trace buffer and print out whatever collected data
10303 you are interested in. Thus, if we want to examine the PC, FP, and SP
10304 registers from each trace frame in the buffer, we can say this:
10307 (@value{GDBP}) @b{tfind start}
10308 (@value{GDBP}) @b{while ($trace_frame != -1)}
10309 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10310 $trace_frame, $pc, $sp, $fp
10314 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10315 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10316 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10317 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10318 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10319 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10320 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10321 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10322 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10323 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10324 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10327 Or, if we want to examine the variable @code{X} at each source line in
10331 (@value{GDBP}) @b{tfind start}
10332 (@value{GDBP}) @b{while ($trace_frame != -1)}
10333 > printf "Frame %d, X == %d\n", $trace_frame, X
10343 @subsection @code{tdump}
10345 @cindex dump all data collected at tracepoint
10346 @cindex tracepoint data, display
10348 This command takes no arguments. It prints all the data collected at
10349 the current trace snapshot.
10352 (@value{GDBP}) @b{trace 444}
10353 (@value{GDBP}) @b{actions}
10354 Enter actions for tracepoint #2, one per line:
10355 > collect $regs, $locals, $args, gdb_long_test
10358 (@value{GDBP}) @b{tstart}
10360 (@value{GDBP}) @b{tfind line 444}
10361 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10363 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10365 (@value{GDBP}) @b{tdump}
10366 Data collected at tracepoint 2, trace frame 1:
10367 d0 0xc4aa0085 -995491707
10371 d4 0x71aea3d 119204413
10374 d7 0x380035 3670069
10375 a0 0x19e24a 1696330
10376 a1 0x3000668 50333288
10378 a3 0x322000 3284992
10379 a4 0x3000698 50333336
10380 a5 0x1ad3cc 1758156
10381 fp 0x30bf3c 0x30bf3c
10382 sp 0x30bf34 0x30bf34
10384 pc 0x20b2c8 0x20b2c8
10388 p = 0x20e5b4 "gdb-test"
10395 gdb_long_test = 17 '\021'
10400 @code{tdump} works by scanning the tracepoint's current collection
10401 actions and printing the value of each expression listed. So
10402 @code{tdump} can fail, if after a run, you change the tracepoint's
10403 actions to mention variables that were not collected during the run.
10405 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10406 uses the collected value of @code{$pc} to distinguish between trace
10407 frames that were collected at the tracepoint hit, and frames that were
10408 collected while stepping. This allows it to correctly choose whether
10409 to display the basic list of collections, or the collections from the
10410 body of the while-stepping loop. However, if @code{$pc} was not collected,
10411 then @code{tdump} will always attempt to dump using the basic collection
10412 list, and may fail if a while-stepping frame does not include all the
10413 same data that is collected at the tracepoint hit.
10414 @c This is getting pretty arcane, example would be good.
10416 @node save tracepoints
10417 @subsection @code{save tracepoints @var{filename}}
10418 @kindex save tracepoints
10419 @kindex save-tracepoints
10420 @cindex save tracepoints for future sessions
10422 This command saves all current tracepoint definitions together with
10423 their actions and passcounts, into a file @file{@var{filename}}
10424 suitable for use in a later debugging session. To read the saved
10425 tracepoint definitions, use the @code{source} command (@pxref{Command
10426 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10427 alias for @w{@code{save tracepoints}}
10429 @node Tracepoint Variables
10430 @section Convenience Variables for Tracepoints
10431 @cindex tracepoint variables
10432 @cindex convenience variables for tracepoints
10435 @vindex $trace_frame
10436 @item (int) $trace_frame
10437 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10438 snapshot is selected.
10440 @vindex $tracepoint
10441 @item (int) $tracepoint
10442 The tracepoint for the current trace snapshot.
10444 @vindex $trace_line
10445 @item (int) $trace_line
10446 The line number for the current trace snapshot.
10448 @vindex $trace_file
10449 @item (char []) $trace_file
10450 The source file for the current trace snapshot.
10452 @vindex $trace_func
10453 @item (char []) $trace_func
10454 The name of the function containing @code{$tracepoint}.
10457 Note: @code{$trace_file} is not suitable for use in @code{printf},
10458 use @code{output} instead.
10460 Here's a simple example of using these convenience variables for
10461 stepping through all the trace snapshots and printing some of their
10462 data. Note that these are not the same as trace state variables,
10463 which are managed by the target.
10466 (@value{GDBP}) @b{tfind start}
10468 (@value{GDBP}) @b{while $trace_frame != -1}
10469 > output $trace_file
10470 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10476 @section Using Trace Files
10477 @cindex trace files
10479 In some situations, the target running a trace experiment may no
10480 longer be available; perhaps it crashed, or the hardware was needed
10481 for a different activity. To handle these cases, you can arrange to
10482 dump the trace data into a file, and later use that file as a source
10483 of trace data, via the @code{target tfile} command.
10488 @item tsave [ -r ] @var{filename}
10489 Save the trace data to @var{filename}. By default, this command
10490 assumes that @var{filename} refers to the host filesystem, so if
10491 necessary @value{GDBN} will copy raw trace data up from the target and
10492 then save it. If the target supports it, you can also supply the
10493 optional argument @code{-r} (``remote'') to direct the target to save
10494 the data directly into @var{filename} in its own filesystem, which may be
10495 more efficient if the trace buffer is very large. (Note, however, that
10496 @code{target tfile} can only read from files accessible to the host.)
10498 @kindex target tfile
10500 @item target tfile @var{filename}
10501 Use the file named @var{filename} as a source of trace data. Commands
10502 that examine data work as they do with a live target, but it is not
10503 possible to run any new trace experiments. @code{tstatus} will report
10504 the state of the trace run at the moment the data was saved, as well
10505 as the current trace frame you are examining. @var{filename} must be
10506 on a filesystem accessible to the host.
10511 @chapter Debugging Programs That Use Overlays
10514 If your program is too large to fit completely in your target system's
10515 memory, you can sometimes use @dfn{overlays} to work around this
10516 problem. @value{GDBN} provides some support for debugging programs that
10520 * How Overlays Work:: A general explanation of overlays.
10521 * Overlay Commands:: Managing overlays in @value{GDBN}.
10522 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10523 mapped by asking the inferior.
10524 * Overlay Sample Program:: A sample program using overlays.
10527 @node How Overlays Work
10528 @section How Overlays Work
10529 @cindex mapped overlays
10530 @cindex unmapped overlays
10531 @cindex load address, overlay's
10532 @cindex mapped address
10533 @cindex overlay area
10535 Suppose you have a computer whose instruction address space is only 64
10536 kilobytes long, but which has much more memory which can be accessed by
10537 other means: special instructions, segment registers, or memory
10538 management hardware, for example. Suppose further that you want to
10539 adapt a program which is larger than 64 kilobytes to run on this system.
10541 One solution is to identify modules of your program which are relatively
10542 independent, and need not call each other directly; call these modules
10543 @dfn{overlays}. Separate the overlays from the main program, and place
10544 their machine code in the larger memory. Place your main program in
10545 instruction memory, but leave at least enough space there to hold the
10546 largest overlay as well.
10548 Now, to call a function located in an overlay, you must first copy that
10549 overlay's machine code from the large memory into the space set aside
10550 for it in the instruction memory, and then jump to its entry point
10553 @c NB: In the below the mapped area's size is greater or equal to the
10554 @c size of all overlays. This is intentional to remind the developer
10555 @c that overlays don't necessarily need to be the same size.
10559 Data Instruction Larger
10560 Address Space Address Space Address Space
10561 +-----------+ +-----------+ +-----------+
10563 +-----------+ +-----------+ +-----------+<-- overlay 1
10564 | program | | main | .----| overlay 1 | load address
10565 | variables | | program | | +-----------+
10566 | and heap | | | | | |
10567 +-----------+ | | | +-----------+<-- overlay 2
10568 | | +-----------+ | | | load address
10569 +-----------+ | | | .-| overlay 2 |
10571 mapped --->+-----------+ | | +-----------+
10572 address | | | | | |
10573 | overlay | <-' | | |
10574 | area | <---' +-----------+<-- overlay 3
10575 | | <---. | | load address
10576 +-----------+ `--| overlay 3 |
10583 @anchor{A code overlay}A code overlay
10587 The diagram (@pxref{A code overlay}) shows a system with separate data
10588 and instruction address spaces. To map an overlay, the program copies
10589 its code from the larger address space to the instruction address space.
10590 Since the overlays shown here all use the same mapped address, only one
10591 may be mapped at a time. For a system with a single address space for
10592 data and instructions, the diagram would be similar, except that the
10593 program variables and heap would share an address space with the main
10594 program and the overlay area.
10596 An overlay loaded into instruction memory and ready for use is called a
10597 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10598 instruction memory. An overlay not present (or only partially present)
10599 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10600 is its address in the larger memory. The mapped address is also called
10601 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10602 called the @dfn{load memory address}, or @dfn{LMA}.
10604 Unfortunately, overlays are not a completely transparent way to adapt a
10605 program to limited instruction memory. They introduce a new set of
10606 global constraints you must keep in mind as you design your program:
10611 Before calling or returning to a function in an overlay, your program
10612 must make sure that overlay is actually mapped. Otherwise, the call or
10613 return will transfer control to the right address, but in the wrong
10614 overlay, and your program will probably crash.
10617 If the process of mapping an overlay is expensive on your system, you
10618 will need to choose your overlays carefully to minimize their effect on
10619 your program's performance.
10622 The executable file you load onto your system must contain each
10623 overlay's instructions, appearing at the overlay's load address, not its
10624 mapped address. However, each overlay's instructions must be relocated
10625 and its symbols defined as if the overlay were at its mapped address.
10626 You can use GNU linker scripts to specify different load and relocation
10627 addresses for pieces of your program; see @ref{Overlay Description,,,
10628 ld.info, Using ld: the GNU linker}.
10631 The procedure for loading executable files onto your system must be able
10632 to load their contents into the larger address space as well as the
10633 instruction and data spaces.
10637 The overlay system described above is rather simple, and could be
10638 improved in many ways:
10643 If your system has suitable bank switch registers or memory management
10644 hardware, you could use those facilities to make an overlay's load area
10645 contents simply appear at their mapped address in instruction space.
10646 This would probably be faster than copying the overlay to its mapped
10647 area in the usual way.
10650 If your overlays are small enough, you could set aside more than one
10651 overlay area, and have more than one overlay mapped at a time.
10654 You can use overlays to manage data, as well as instructions. In
10655 general, data overlays are even less transparent to your design than
10656 code overlays: whereas code overlays only require care when you call or
10657 return to functions, data overlays require care every time you access
10658 the data. Also, if you change the contents of a data overlay, you
10659 must copy its contents back out to its load address before you can copy a
10660 different data overlay into the same mapped area.
10665 @node Overlay Commands
10666 @section Overlay Commands
10668 To use @value{GDBN}'s overlay support, each overlay in your program must
10669 correspond to a separate section of the executable file. The section's
10670 virtual memory address and load memory address must be the overlay's
10671 mapped and load addresses. Identifying overlays with sections allows
10672 @value{GDBN} to determine the appropriate address of a function or
10673 variable, depending on whether the overlay is mapped or not.
10675 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10676 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10681 Disable @value{GDBN}'s overlay support. When overlay support is
10682 disabled, @value{GDBN} assumes that all functions and variables are
10683 always present at their mapped addresses. By default, @value{GDBN}'s
10684 overlay support is disabled.
10686 @item overlay manual
10687 @cindex manual overlay debugging
10688 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10689 relies on you to tell it which overlays are mapped, and which are not,
10690 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10691 commands described below.
10693 @item overlay map-overlay @var{overlay}
10694 @itemx overlay map @var{overlay}
10695 @cindex map an overlay
10696 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10697 be the name of the object file section containing the overlay. When an
10698 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10699 functions and variables at their mapped addresses. @value{GDBN} assumes
10700 that any other overlays whose mapped ranges overlap that of
10701 @var{overlay} are now unmapped.
10703 @item overlay unmap-overlay @var{overlay}
10704 @itemx overlay unmap @var{overlay}
10705 @cindex unmap an overlay
10706 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10707 must be the name of the object file section containing the overlay.
10708 When an overlay is unmapped, @value{GDBN} assumes it can find the
10709 overlay's functions and variables at their load addresses.
10712 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10713 consults a data structure the overlay manager maintains in the inferior
10714 to see which overlays are mapped. For details, see @ref{Automatic
10715 Overlay Debugging}.
10717 @item overlay load-target
10718 @itemx overlay load
10719 @cindex reloading the overlay table
10720 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10721 re-reads the table @value{GDBN} automatically each time the inferior
10722 stops, so this command should only be necessary if you have changed the
10723 overlay mapping yourself using @value{GDBN}. This command is only
10724 useful when using automatic overlay debugging.
10726 @item overlay list-overlays
10727 @itemx overlay list
10728 @cindex listing mapped overlays
10729 Display a list of the overlays currently mapped, along with their mapped
10730 addresses, load addresses, and sizes.
10734 Normally, when @value{GDBN} prints a code address, it includes the name
10735 of the function the address falls in:
10738 (@value{GDBP}) print main
10739 $3 = @{int ()@} 0x11a0 <main>
10742 When overlay debugging is enabled, @value{GDBN} recognizes code in
10743 unmapped overlays, and prints the names of unmapped functions with
10744 asterisks around them. For example, if @code{foo} is a function in an
10745 unmapped overlay, @value{GDBN} prints it this way:
10748 (@value{GDBP}) overlay list
10749 No sections are mapped.
10750 (@value{GDBP}) print foo
10751 $5 = @{int (int)@} 0x100000 <*foo*>
10754 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10758 (@value{GDBP}) overlay list
10759 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10760 mapped at 0x1016 - 0x104a
10761 (@value{GDBP}) print foo
10762 $6 = @{int (int)@} 0x1016 <foo>
10765 When overlay debugging is enabled, @value{GDBN} can find the correct
10766 address for functions and variables in an overlay, whether or not the
10767 overlay is mapped. This allows most @value{GDBN} commands, like
10768 @code{break} and @code{disassemble}, to work normally, even on unmapped
10769 code. However, @value{GDBN}'s breakpoint support has some limitations:
10773 @cindex breakpoints in overlays
10774 @cindex overlays, setting breakpoints in
10775 You can set breakpoints in functions in unmapped overlays, as long as
10776 @value{GDBN} can write to the overlay at its load address.
10778 @value{GDBN} can not set hardware or simulator-based breakpoints in
10779 unmapped overlays. However, if you set a breakpoint at the end of your
10780 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10781 you are using manual overlay management), @value{GDBN} will re-set its
10782 breakpoints properly.
10786 @node Automatic Overlay Debugging
10787 @section Automatic Overlay Debugging
10788 @cindex automatic overlay debugging
10790 @value{GDBN} can automatically track which overlays are mapped and which
10791 are not, given some simple co-operation from the overlay manager in the
10792 inferior. If you enable automatic overlay debugging with the
10793 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10794 looks in the inferior's memory for certain variables describing the
10795 current state of the overlays.
10797 Here are the variables your overlay manager must define to support
10798 @value{GDBN}'s automatic overlay debugging:
10802 @item @code{_ovly_table}:
10803 This variable must be an array of the following structures:
10808 /* The overlay's mapped address. */
10811 /* The size of the overlay, in bytes. */
10812 unsigned long size;
10814 /* The overlay's load address. */
10817 /* Non-zero if the overlay is currently mapped;
10819 unsigned long mapped;
10823 @item @code{_novlys}:
10824 This variable must be a four-byte signed integer, holding the total
10825 number of elements in @code{_ovly_table}.
10829 To decide whether a particular overlay is mapped or not, @value{GDBN}
10830 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10831 @code{lma} members equal the VMA and LMA of the overlay's section in the
10832 executable file. When @value{GDBN} finds a matching entry, it consults
10833 the entry's @code{mapped} member to determine whether the overlay is
10836 In addition, your overlay manager may define a function called
10837 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10838 will silently set a breakpoint there. If the overlay manager then
10839 calls this function whenever it has changed the overlay table, this
10840 will enable @value{GDBN} to accurately keep track of which overlays
10841 are in program memory, and update any breakpoints that may be set
10842 in overlays. This will allow breakpoints to work even if the
10843 overlays are kept in ROM or other non-writable memory while they
10844 are not being executed.
10846 @node Overlay Sample Program
10847 @section Overlay Sample Program
10848 @cindex overlay example program
10850 When linking a program which uses overlays, you must place the overlays
10851 at their load addresses, while relocating them to run at their mapped
10852 addresses. To do this, you must write a linker script (@pxref{Overlay
10853 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10854 since linker scripts are specific to a particular host system, target
10855 architecture, and target memory layout, this manual cannot provide
10856 portable sample code demonstrating @value{GDBN}'s overlay support.
10858 However, the @value{GDBN} source distribution does contain an overlaid
10859 program, with linker scripts for a few systems, as part of its test
10860 suite. The program consists of the following files from
10861 @file{gdb/testsuite/gdb.base}:
10865 The main program file.
10867 A simple overlay manager, used by @file{overlays.c}.
10872 Overlay modules, loaded and used by @file{overlays.c}.
10875 Linker scripts for linking the test program on the @code{d10v-elf}
10876 and @code{m32r-elf} targets.
10879 You can build the test program using the @code{d10v-elf} GCC
10880 cross-compiler like this:
10883 $ d10v-elf-gcc -g -c overlays.c
10884 $ d10v-elf-gcc -g -c ovlymgr.c
10885 $ d10v-elf-gcc -g -c foo.c
10886 $ d10v-elf-gcc -g -c bar.c
10887 $ d10v-elf-gcc -g -c baz.c
10888 $ d10v-elf-gcc -g -c grbx.c
10889 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10890 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10893 The build process is identical for any other architecture, except that
10894 you must substitute the appropriate compiler and linker script for the
10895 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10899 @chapter Using @value{GDBN} with Different Languages
10902 Although programming languages generally have common aspects, they are
10903 rarely expressed in the same manner. For instance, in ANSI C,
10904 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10905 Modula-2, it is accomplished by @code{p^}. Values can also be
10906 represented (and displayed) differently. Hex numbers in C appear as
10907 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10909 @cindex working language
10910 Language-specific information is built into @value{GDBN} for some languages,
10911 allowing you to express operations like the above in your program's
10912 native language, and allowing @value{GDBN} to output values in a manner
10913 consistent with the syntax of your program's native language. The
10914 language you use to build expressions is called the @dfn{working
10918 * Setting:: Switching between source languages
10919 * Show:: Displaying the language
10920 * Checks:: Type and range checks
10921 * Supported Languages:: Supported languages
10922 * Unsupported Languages:: Unsupported languages
10926 @section Switching Between Source Languages
10928 There are two ways to control the working language---either have @value{GDBN}
10929 set it automatically, or select it manually yourself. You can use the
10930 @code{set language} command for either purpose. On startup, @value{GDBN}
10931 defaults to setting the language automatically. The working language is
10932 used to determine how expressions you type are interpreted, how values
10935 In addition to the working language, every source file that
10936 @value{GDBN} knows about has its own working language. For some object
10937 file formats, the compiler might indicate which language a particular
10938 source file is in. However, most of the time @value{GDBN} infers the
10939 language from the name of the file. The language of a source file
10940 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10941 show each frame appropriately for its own language. There is no way to
10942 set the language of a source file from within @value{GDBN}, but you can
10943 set the language associated with a filename extension. @xref{Show, ,
10944 Displaying the Language}.
10946 This is most commonly a problem when you use a program, such
10947 as @code{cfront} or @code{f2c}, that generates C but is written in
10948 another language. In that case, make the
10949 program use @code{#line} directives in its C output; that way
10950 @value{GDBN} will know the correct language of the source code of the original
10951 program, and will display that source code, not the generated C code.
10954 * Filenames:: Filename extensions and languages.
10955 * Manually:: Setting the working language manually
10956 * Automatically:: Having @value{GDBN} infer the source language
10960 @subsection List of Filename Extensions and Languages
10962 If a source file name ends in one of the following extensions, then
10963 @value{GDBN} infers that its language is the one indicated.
10981 C@t{++} source file
10987 Objective-C source file
10991 Fortran source file
10994 Modula-2 source file
10998 Assembler source file. This actually behaves almost like C, but
10999 @value{GDBN} does not skip over function prologues when stepping.
11002 In addition, you may set the language associated with a filename
11003 extension. @xref{Show, , Displaying the Language}.
11006 @subsection Setting the Working Language
11008 If you allow @value{GDBN} to set the language automatically,
11009 expressions are interpreted the same way in your debugging session and
11012 @kindex set language
11013 If you wish, you may set the language manually. To do this, issue the
11014 command @samp{set language @var{lang}}, where @var{lang} is the name of
11015 a language, such as
11016 @code{c} or @code{modula-2}.
11017 For a list of the supported languages, type @samp{set language}.
11019 Setting the language manually prevents @value{GDBN} from updating the working
11020 language automatically. This can lead to confusion if you try
11021 to debug a program when the working language is not the same as the
11022 source language, when an expression is acceptable to both
11023 languages---but means different things. For instance, if the current
11024 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11032 might not have the effect you intended. In C, this means to add
11033 @code{b} and @code{c} and place the result in @code{a}. The result
11034 printed would be the value of @code{a}. In Modula-2, this means to compare
11035 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11037 @node Automatically
11038 @subsection Having @value{GDBN} Infer the Source Language
11040 To have @value{GDBN} set the working language automatically, use
11041 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11042 then infers the working language. That is, when your program stops in a
11043 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11044 working language to the language recorded for the function in that
11045 frame. If the language for a frame is unknown (that is, if the function
11046 or block corresponding to the frame was defined in a source file that
11047 does not have a recognized extension), the current working language is
11048 not changed, and @value{GDBN} issues a warning.
11050 This may not seem necessary for most programs, which are written
11051 entirely in one source language. However, program modules and libraries
11052 written in one source language can be used by a main program written in
11053 a different source language. Using @samp{set language auto} in this
11054 case frees you from having to set the working language manually.
11057 @section Displaying the Language
11059 The following commands help you find out which language is the
11060 working language, and also what language source files were written in.
11063 @item show language
11064 @kindex show language
11065 Display the current working language. This is the
11066 language you can use with commands such as @code{print} to
11067 build and compute expressions that may involve variables in your program.
11070 @kindex info frame@r{, show the source language}
11071 Display the source language for this frame. This language becomes the
11072 working language if you use an identifier from this frame.
11073 @xref{Frame Info, ,Information about a Frame}, to identify the other
11074 information listed here.
11077 @kindex info source@r{, show the source language}
11078 Display the source language of this source file.
11079 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11080 information listed here.
11083 In unusual circumstances, you may have source files with extensions
11084 not in the standard list. You can then set the extension associated
11085 with a language explicitly:
11088 @item set extension-language @var{ext} @var{language}
11089 @kindex set extension-language
11090 Tell @value{GDBN} that source files with extension @var{ext} are to be
11091 assumed as written in the source language @var{language}.
11093 @item info extensions
11094 @kindex info extensions
11095 List all the filename extensions and the associated languages.
11099 @section Type and Range Checking
11102 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11103 checking are included, but they do not yet have any effect. This
11104 section documents the intended facilities.
11106 @c FIXME remove warning when type/range code added
11108 Some languages are designed to guard you against making seemingly common
11109 errors through a series of compile- and run-time checks. These include
11110 checking the type of arguments to functions and operators, and making
11111 sure mathematical overflows are caught at run time. Checks such as
11112 these help to ensure a program's correctness once it has been compiled
11113 by eliminating type mismatches, and providing active checks for range
11114 errors when your program is running.
11116 @value{GDBN} can check for conditions like the above if you wish.
11117 Although @value{GDBN} does not check the statements in your program,
11118 it can check expressions entered directly into @value{GDBN} for
11119 evaluation via the @code{print} command, for example. As with the
11120 working language, @value{GDBN} can also decide whether or not to check
11121 automatically based on your program's source language.
11122 @xref{Supported Languages, ,Supported Languages}, for the default
11123 settings of supported languages.
11126 * Type Checking:: An overview of type checking
11127 * Range Checking:: An overview of range checking
11130 @cindex type checking
11131 @cindex checks, type
11132 @node Type Checking
11133 @subsection An Overview of Type Checking
11135 Some languages, such as Modula-2, are strongly typed, meaning that the
11136 arguments to operators and functions have to be of the correct type,
11137 otherwise an error occurs. These checks prevent type mismatch
11138 errors from ever causing any run-time problems. For example,
11146 The second example fails because the @code{CARDINAL} 1 is not
11147 type-compatible with the @code{REAL} 2.3.
11149 For the expressions you use in @value{GDBN} commands, you can tell the
11150 @value{GDBN} type checker to skip checking;
11151 to treat any mismatches as errors and abandon the expression;
11152 or to only issue warnings when type mismatches occur,
11153 but evaluate the expression anyway. When you choose the last of
11154 these, @value{GDBN} evaluates expressions like the second example above, but
11155 also issues a warning.
11157 Even if you turn type checking off, there may be other reasons
11158 related to type that prevent @value{GDBN} from evaluating an expression.
11159 For instance, @value{GDBN} does not know how to add an @code{int} and
11160 a @code{struct foo}. These particular type errors have nothing to do
11161 with the language in use, and usually arise from expressions, such as
11162 the one described above, which make little sense to evaluate anyway.
11164 Each language defines to what degree it is strict about type. For
11165 instance, both Modula-2 and C require the arguments to arithmetical
11166 operators to be numbers. In C, enumerated types and pointers can be
11167 represented as numbers, so that they are valid arguments to mathematical
11168 operators. @xref{Supported Languages, ,Supported Languages}, for further
11169 details on specific languages.
11171 @value{GDBN} provides some additional commands for controlling the type checker:
11173 @kindex set check type
11174 @kindex show check type
11176 @item set check type auto
11177 Set type checking on or off based on the current working language.
11178 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11181 @item set check type on
11182 @itemx set check type off
11183 Set type checking on or off, overriding the default setting for the
11184 current working language. Issue a warning if the setting does not
11185 match the language default. If any type mismatches occur in
11186 evaluating an expression while type checking is on, @value{GDBN} prints a
11187 message and aborts evaluation of the expression.
11189 @item set check type warn
11190 Cause the type checker to issue warnings, but to always attempt to
11191 evaluate the expression. Evaluating the expression may still
11192 be impossible for other reasons. For example, @value{GDBN} cannot add
11193 numbers and structures.
11196 Show the current setting of the type checker, and whether or not @value{GDBN}
11197 is setting it automatically.
11200 @cindex range checking
11201 @cindex checks, range
11202 @node Range Checking
11203 @subsection An Overview of Range Checking
11205 In some languages (such as Modula-2), it is an error to exceed the
11206 bounds of a type; this is enforced with run-time checks. Such range
11207 checking is meant to ensure program correctness by making sure
11208 computations do not overflow, or indices on an array element access do
11209 not exceed the bounds of the array.
11211 For expressions you use in @value{GDBN} commands, you can tell
11212 @value{GDBN} to treat range errors in one of three ways: ignore them,
11213 always treat them as errors and abandon the expression, or issue
11214 warnings but evaluate the expression anyway.
11216 A range error can result from numerical overflow, from exceeding an
11217 array index bound, or when you type a constant that is not a member
11218 of any type. Some languages, however, do not treat overflows as an
11219 error. In many implementations of C, mathematical overflow causes the
11220 result to ``wrap around'' to lower values---for example, if @var{m} is
11221 the largest integer value, and @var{s} is the smallest, then
11224 @var{m} + 1 @result{} @var{s}
11227 This, too, is specific to individual languages, and in some cases
11228 specific to individual compilers or machines. @xref{Supported Languages, ,
11229 Supported Languages}, for further details on specific languages.
11231 @value{GDBN} provides some additional commands for controlling the range checker:
11233 @kindex set check range
11234 @kindex show check range
11236 @item set check range auto
11237 Set range checking on or off based on the current working language.
11238 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11241 @item set check range on
11242 @itemx set check range off
11243 Set range checking on or off, overriding the default setting for the
11244 current working language. A warning is issued if the setting does not
11245 match the language default. If a range error occurs and range checking is on,
11246 then a message is printed and evaluation of the expression is aborted.
11248 @item set check range warn
11249 Output messages when the @value{GDBN} range checker detects a range error,
11250 but attempt to evaluate the expression anyway. Evaluating the
11251 expression may still be impossible for other reasons, such as accessing
11252 memory that the process does not own (a typical example from many Unix
11256 Show the current setting of the range checker, and whether or not it is
11257 being set automatically by @value{GDBN}.
11260 @node Supported Languages
11261 @section Supported Languages
11263 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11264 assembly, Modula-2, and Ada.
11265 @c This is false ...
11266 Some @value{GDBN} features may be used in expressions regardless of the
11267 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11268 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11269 ,Expressions}) can be used with the constructs of any supported
11272 The following sections detail to what degree each source language is
11273 supported by @value{GDBN}. These sections are not meant to be language
11274 tutorials or references, but serve only as a reference guide to what the
11275 @value{GDBN} expression parser accepts, and what input and output
11276 formats should look like for different languages. There are many good
11277 books written on each of these languages; please look to these for a
11278 language reference or tutorial.
11281 * C:: C and C@t{++}
11283 * Objective-C:: Objective-C
11284 * Fortran:: Fortran
11286 * Modula-2:: Modula-2
11291 @subsection C and C@t{++}
11293 @cindex C and C@t{++}
11294 @cindex expressions in C or C@t{++}
11296 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11297 to both languages. Whenever this is the case, we discuss those languages
11301 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11302 @cindex @sc{gnu} C@t{++}
11303 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11304 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11305 effectively, you must compile your C@t{++} programs with a supported
11306 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11307 compiler (@code{aCC}).
11309 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11310 format; if it doesn't work on your system, try the stabs+ debugging
11311 format. You can select those formats explicitly with the @code{g++}
11312 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11313 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11314 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11317 * C Operators:: C and C@t{++} operators
11318 * C Constants:: C and C@t{++} constants
11319 * C Plus Plus Expressions:: C@t{++} expressions
11320 * C Defaults:: Default settings for C and C@t{++}
11321 * C Checks:: C and C@t{++} type and range checks
11322 * Debugging C:: @value{GDBN} and C
11323 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11324 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11328 @subsubsection C and C@t{++} Operators
11330 @cindex C and C@t{++} operators
11332 Operators must be defined on values of specific types. For instance,
11333 @code{+} is defined on numbers, but not on structures. Operators are
11334 often defined on groups of types.
11336 For the purposes of C and C@t{++}, the following definitions hold:
11341 @emph{Integral types} include @code{int} with any of its storage-class
11342 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11345 @emph{Floating-point types} include @code{float}, @code{double}, and
11346 @code{long double} (if supported by the target platform).
11349 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11352 @emph{Scalar types} include all of the above.
11357 The following operators are supported. They are listed here
11358 in order of increasing precedence:
11362 The comma or sequencing operator. Expressions in a comma-separated list
11363 are evaluated from left to right, with the result of the entire
11364 expression being the last expression evaluated.
11367 Assignment. The value of an assignment expression is the value
11368 assigned. Defined on scalar types.
11371 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11372 and translated to @w{@code{@var{a} = @var{a op b}}}.
11373 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11374 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11375 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11378 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11379 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11383 Logical @sc{or}. Defined on integral types.
11386 Logical @sc{and}. Defined on integral types.
11389 Bitwise @sc{or}. Defined on integral types.
11392 Bitwise exclusive-@sc{or}. Defined on integral types.
11395 Bitwise @sc{and}. Defined on integral types.
11398 Equality and inequality. Defined on scalar types. The value of these
11399 expressions is 0 for false and non-zero for true.
11401 @item <@r{, }>@r{, }<=@r{, }>=
11402 Less than, greater than, less than or equal, greater than or equal.
11403 Defined on scalar types. The value of these expressions is 0 for false
11404 and non-zero for true.
11407 left shift, and right shift. Defined on integral types.
11410 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11413 Addition and subtraction. Defined on integral types, floating-point types and
11416 @item *@r{, }/@r{, }%
11417 Multiplication, division, and modulus. Multiplication and division are
11418 defined on integral and floating-point types. Modulus is defined on
11422 Increment and decrement. When appearing before a variable, the
11423 operation is performed before the variable is used in an expression;
11424 when appearing after it, the variable's value is used before the
11425 operation takes place.
11428 Pointer dereferencing. Defined on pointer types. Same precedence as
11432 Address operator. Defined on variables. Same precedence as @code{++}.
11434 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11435 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11436 to examine the address
11437 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11441 Negative. Defined on integral and floating-point types. Same
11442 precedence as @code{++}.
11445 Logical negation. Defined on integral types. Same precedence as
11449 Bitwise complement operator. Defined on integral types. Same precedence as
11454 Structure member, and pointer-to-structure member. For convenience,
11455 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11456 pointer based on the stored type information.
11457 Defined on @code{struct} and @code{union} data.
11460 Dereferences of pointers to members.
11463 Array indexing. @code{@var{a}[@var{i}]} is defined as
11464 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11467 Function parameter list. Same precedence as @code{->}.
11470 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11471 and @code{class} types.
11474 Doubled colons also represent the @value{GDBN} scope operator
11475 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11479 If an operator is redefined in the user code, @value{GDBN} usually
11480 attempts to invoke the redefined version instead of using the operator's
11481 predefined meaning.
11484 @subsubsection C and C@t{++} Constants
11486 @cindex C and C@t{++} constants
11488 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11493 Integer constants are a sequence of digits. Octal constants are
11494 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11495 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11496 @samp{l}, specifying that the constant should be treated as a
11500 Floating point constants are a sequence of digits, followed by a decimal
11501 point, followed by a sequence of digits, and optionally followed by an
11502 exponent. An exponent is of the form:
11503 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11504 sequence of digits. The @samp{+} is optional for positive exponents.
11505 A floating-point constant may also end with a letter @samp{f} or
11506 @samp{F}, specifying that the constant should be treated as being of
11507 the @code{float} (as opposed to the default @code{double}) type; or with
11508 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11512 Enumerated constants consist of enumerated identifiers, or their
11513 integral equivalents.
11516 Character constants are a single character surrounded by single quotes
11517 (@code{'}), or a number---the ordinal value of the corresponding character
11518 (usually its @sc{ascii} value). Within quotes, the single character may
11519 be represented by a letter or by @dfn{escape sequences}, which are of
11520 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11521 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11522 @samp{@var{x}} is a predefined special character---for example,
11523 @samp{\n} for newline.
11526 String constants are a sequence of character constants surrounded by
11527 double quotes (@code{"}). Any valid character constant (as described
11528 above) may appear. Double quotes within the string must be preceded by
11529 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11533 Pointer constants are an integral value. You can also write pointers
11534 to constants using the C operator @samp{&}.
11537 Array constants are comma-separated lists surrounded by braces @samp{@{}
11538 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11539 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11540 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11543 @node C Plus Plus Expressions
11544 @subsubsection C@t{++} Expressions
11546 @cindex expressions in C@t{++}
11547 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11549 @cindex debugging C@t{++} programs
11550 @cindex C@t{++} compilers
11551 @cindex debug formats and C@t{++}
11552 @cindex @value{NGCC} and C@t{++}
11554 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11555 proper compiler and the proper debug format. Currently, @value{GDBN}
11556 works best when debugging C@t{++} code that is compiled with
11557 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11558 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11559 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11560 stabs+ as their default debug format, so you usually don't need to
11561 specify a debug format explicitly. Other compilers and/or debug formats
11562 are likely to work badly or not at all when using @value{GDBN} to debug
11568 @cindex member functions
11570 Member function calls are allowed; you can use expressions like
11573 count = aml->GetOriginal(x, y)
11576 @vindex this@r{, inside C@t{++} member functions}
11577 @cindex namespace in C@t{++}
11579 While a member function is active (in the selected stack frame), your
11580 expressions have the same namespace available as the member function;
11581 that is, @value{GDBN} allows implicit references to the class instance
11582 pointer @code{this} following the same rules as C@t{++}.
11584 @cindex call overloaded functions
11585 @cindex overloaded functions, calling
11586 @cindex type conversions in C@t{++}
11588 You can call overloaded functions; @value{GDBN} resolves the function
11589 call to the right definition, with some restrictions. @value{GDBN} does not
11590 perform overload resolution involving user-defined type conversions,
11591 calls to constructors, or instantiations of templates that do not exist
11592 in the program. It also cannot handle ellipsis argument lists or
11595 It does perform integral conversions and promotions, floating-point
11596 promotions, arithmetic conversions, pointer conversions, conversions of
11597 class objects to base classes, and standard conversions such as those of
11598 functions or arrays to pointers; it requires an exact match on the
11599 number of function arguments.
11601 Overload resolution is always performed, unless you have specified
11602 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11603 ,@value{GDBN} Features for C@t{++}}.
11605 You must specify @code{set overload-resolution off} in order to use an
11606 explicit function signature to call an overloaded function, as in
11608 p 'foo(char,int)'('x', 13)
11611 The @value{GDBN} command-completion facility can simplify this;
11612 see @ref{Completion, ,Command Completion}.
11614 @cindex reference declarations
11616 @value{GDBN} understands variables declared as C@t{++} references; you can use
11617 them in expressions just as you do in C@t{++} source---they are automatically
11620 In the parameter list shown when @value{GDBN} displays a frame, the values of
11621 reference variables are not displayed (unlike other variables); this
11622 avoids clutter, since references are often used for large structures.
11623 The @emph{address} of a reference variable is always shown, unless
11624 you have specified @samp{set print address off}.
11627 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11628 expressions can use it just as expressions in your program do. Since
11629 one scope may be defined in another, you can use @code{::} repeatedly if
11630 necessary, for example in an expression like
11631 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11632 resolving name scope by reference to source files, in both C and C@t{++}
11633 debugging (@pxref{Variables, ,Program Variables}).
11636 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11637 calling virtual functions correctly, printing out virtual bases of
11638 objects, calling functions in a base subobject, casting objects, and
11639 invoking user-defined operators.
11642 @subsubsection C and C@t{++} Defaults
11644 @cindex C and C@t{++} defaults
11646 If you allow @value{GDBN} to set type and range checking automatically, they
11647 both default to @code{off} whenever the working language changes to
11648 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11649 selects the working language.
11651 If you allow @value{GDBN} to set the language automatically, it
11652 recognizes source files whose names end with @file{.c}, @file{.C}, or
11653 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11654 these files, it sets the working language to C or C@t{++}.
11655 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11656 for further details.
11658 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11659 @c unimplemented. If (b) changes, it might make sense to let this node
11660 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11663 @subsubsection C and C@t{++} Type and Range Checks
11665 @cindex C and C@t{++} checks
11667 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11668 is not used. However, if you turn type checking on, @value{GDBN}
11669 considers two variables type equivalent if:
11673 The two variables are structured and have the same structure, union, or
11677 The two variables have the same type name, or types that have been
11678 declared equivalent through @code{typedef}.
11681 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11684 The two @code{struct}, @code{union}, or @code{enum} variables are
11685 declared in the same declaration. (Note: this may not be true for all C
11690 Range checking, if turned on, is done on mathematical operations. Array
11691 indices are not checked, since they are often used to index a pointer
11692 that is not itself an array.
11695 @subsubsection @value{GDBN} and C
11697 The @code{set print union} and @code{show print union} commands apply to
11698 the @code{union} type. When set to @samp{on}, any @code{union} that is
11699 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11700 appears as @samp{@{...@}}.
11702 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11703 with pointers and a memory allocation function. @xref{Expressions,
11706 @node Debugging C Plus Plus
11707 @subsubsection @value{GDBN} Features for C@t{++}
11709 @cindex commands for C@t{++}
11711 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11712 designed specifically for use with C@t{++}. Here is a summary:
11715 @cindex break in overloaded functions
11716 @item @r{breakpoint menus}
11717 When you want a breakpoint in a function whose name is overloaded,
11718 @value{GDBN} has the capability to display a menu of possible breakpoint
11719 locations to help you specify which function definition you want.
11720 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11722 @cindex overloading in C@t{++}
11723 @item rbreak @var{regex}
11724 Setting breakpoints using regular expressions is helpful for setting
11725 breakpoints on overloaded functions that are not members of any special
11727 @xref{Set Breaks, ,Setting Breakpoints}.
11729 @cindex C@t{++} exception handling
11732 Debug C@t{++} exception handling using these commands. @xref{Set
11733 Catchpoints, , Setting Catchpoints}.
11735 @cindex inheritance
11736 @item ptype @var{typename}
11737 Print inheritance relationships as well as other information for type
11739 @xref{Symbols, ,Examining the Symbol Table}.
11741 @cindex C@t{++} symbol display
11742 @item set print demangle
11743 @itemx show print demangle
11744 @itemx set print asm-demangle
11745 @itemx show print asm-demangle
11746 Control whether C@t{++} symbols display in their source form, both when
11747 displaying code as C@t{++} source and when displaying disassemblies.
11748 @xref{Print Settings, ,Print Settings}.
11750 @item set print object
11751 @itemx show print object
11752 Choose whether to print derived (actual) or declared types of objects.
11753 @xref{Print Settings, ,Print Settings}.
11755 @item set print vtbl
11756 @itemx show print vtbl
11757 Control the format for printing virtual function tables.
11758 @xref{Print Settings, ,Print Settings}.
11759 (The @code{vtbl} commands do not work on programs compiled with the HP
11760 ANSI C@t{++} compiler (@code{aCC}).)
11762 @kindex set overload-resolution
11763 @cindex overloaded functions, overload resolution
11764 @item set overload-resolution on
11765 Enable overload resolution for C@t{++} expression evaluation. The default
11766 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11767 and searches for a function whose signature matches the argument types,
11768 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11769 Expressions, ,C@t{++} Expressions}, for details).
11770 If it cannot find a match, it emits a message.
11772 @item set overload-resolution off
11773 Disable overload resolution for C@t{++} expression evaluation. For
11774 overloaded functions that are not class member functions, @value{GDBN}
11775 chooses the first function of the specified name that it finds in the
11776 symbol table, whether or not its arguments are of the correct type. For
11777 overloaded functions that are class member functions, @value{GDBN}
11778 searches for a function whose signature @emph{exactly} matches the
11781 @kindex show overload-resolution
11782 @item show overload-resolution
11783 Show the current setting of overload resolution.
11785 @item @r{Overloaded symbol names}
11786 You can specify a particular definition of an overloaded symbol, using
11787 the same notation that is used to declare such symbols in C@t{++}: type
11788 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11789 also use the @value{GDBN} command-line word completion facilities to list the
11790 available choices, or to finish the type list for you.
11791 @xref{Completion,, Command Completion}, for details on how to do this.
11794 @node Decimal Floating Point
11795 @subsubsection Decimal Floating Point format
11796 @cindex decimal floating point format
11798 @value{GDBN} can examine, set and perform computations with numbers in
11799 decimal floating point format, which in the C language correspond to the
11800 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11801 specified by the extension to support decimal floating-point arithmetic.
11803 There are two encodings in use, depending on the architecture: BID (Binary
11804 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11805 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11808 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11809 to manipulate decimal floating point numbers, it is not possible to convert
11810 (using a cast, for example) integers wider than 32-bit to decimal float.
11812 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11813 point computations, error checking in decimal float operations ignores
11814 underflow, overflow and divide by zero exceptions.
11816 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11817 to inspect @code{_Decimal128} values stored in floating point registers.
11818 See @ref{PowerPC,,PowerPC} for more details.
11824 @value{GDBN} can be used to debug programs written in D and compiled with
11825 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11826 specific feature --- dynamic arrays.
11829 @subsection Objective-C
11831 @cindex Objective-C
11832 This section provides information about some commands and command
11833 options that are useful for debugging Objective-C code. See also
11834 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11835 few more commands specific to Objective-C support.
11838 * Method Names in Commands::
11839 * The Print Command with Objective-C::
11842 @node Method Names in Commands
11843 @subsubsection Method Names in Commands
11845 The following commands have been extended to accept Objective-C method
11846 names as line specifications:
11848 @kindex clear@r{, and Objective-C}
11849 @kindex break@r{, and Objective-C}
11850 @kindex info line@r{, and Objective-C}
11851 @kindex jump@r{, and Objective-C}
11852 @kindex list@r{, and Objective-C}
11856 @item @code{info line}
11861 A fully qualified Objective-C method name is specified as
11864 -[@var{Class} @var{methodName}]
11867 where the minus sign is used to indicate an instance method and a
11868 plus sign (not shown) is used to indicate a class method. The class
11869 name @var{Class} and method name @var{methodName} are enclosed in
11870 brackets, similar to the way messages are specified in Objective-C
11871 source code. For example, to set a breakpoint at the @code{create}
11872 instance method of class @code{Fruit} in the program currently being
11876 break -[Fruit create]
11879 To list ten program lines around the @code{initialize} class method,
11883 list +[NSText initialize]
11886 In the current version of @value{GDBN}, the plus or minus sign is
11887 required. In future versions of @value{GDBN}, the plus or minus
11888 sign will be optional, but you can use it to narrow the search. It
11889 is also possible to specify just a method name:
11895 You must specify the complete method name, including any colons. If
11896 your program's source files contain more than one @code{create} method,
11897 you'll be presented with a numbered list of classes that implement that
11898 method. Indicate your choice by number, or type @samp{0} to exit if
11901 As another example, to clear a breakpoint established at the
11902 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11905 clear -[NSWindow makeKeyAndOrderFront:]
11908 @node The Print Command with Objective-C
11909 @subsubsection The Print Command With Objective-C
11910 @cindex Objective-C, print objects
11911 @kindex print-object
11912 @kindex po @r{(@code{print-object})}
11914 The print command has also been extended to accept methods. For example:
11917 print -[@var{object} hash]
11920 @cindex print an Objective-C object description
11921 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11923 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11924 and print the result. Also, an additional command has been added,
11925 @code{print-object} or @code{po} for short, which is meant to print
11926 the description of an object. However, this command may only work
11927 with certain Objective-C libraries that have a particular hook
11928 function, @code{_NSPrintForDebugger}, defined.
11931 @subsection Fortran
11932 @cindex Fortran-specific support in @value{GDBN}
11934 @value{GDBN} can be used to debug programs written in Fortran, but it
11935 currently supports only the features of Fortran 77 language.
11937 @cindex trailing underscore, in Fortran symbols
11938 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11939 among them) append an underscore to the names of variables and
11940 functions. When you debug programs compiled by those compilers, you
11941 will need to refer to variables and functions with a trailing
11945 * Fortran Operators:: Fortran operators and expressions
11946 * Fortran Defaults:: Default settings for Fortran
11947 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11950 @node Fortran Operators
11951 @subsubsection Fortran Operators and Expressions
11953 @cindex Fortran operators and expressions
11955 Operators must be defined on values of specific types. For instance,
11956 @code{+} is defined on numbers, but not on characters or other non-
11957 arithmetic types. Operators are often defined on groups of types.
11961 The exponentiation operator. It raises the first operand to the power
11965 The range operator. Normally used in the form of array(low:high) to
11966 represent a section of array.
11969 The access component operator. Normally used to access elements in derived
11970 types. Also suitable for unions. As unions aren't part of regular Fortran,
11971 this can only happen when accessing a register that uses a gdbarch-defined
11975 @node Fortran Defaults
11976 @subsubsection Fortran Defaults
11978 @cindex Fortran Defaults
11980 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11981 default uses case-insensitive matches for Fortran symbols. You can
11982 change that with the @samp{set case-insensitive} command, see
11983 @ref{Symbols}, for the details.
11985 @node Special Fortran Commands
11986 @subsubsection Special Fortran Commands
11988 @cindex Special Fortran commands
11990 @value{GDBN} has some commands to support Fortran-specific features,
11991 such as displaying common blocks.
11994 @cindex @code{COMMON} blocks, Fortran
11995 @kindex info common
11996 @item info common @r{[}@var{common-name}@r{]}
11997 This command prints the values contained in the Fortran @code{COMMON}
11998 block whose name is @var{common-name}. With no argument, the names of
11999 all @code{COMMON} blocks visible at the current program location are
12006 @cindex Pascal support in @value{GDBN}, limitations
12007 Debugging Pascal programs which use sets, subranges, file variables, or
12008 nested functions does not currently work. @value{GDBN} does not support
12009 entering expressions, printing values, or similar features using Pascal
12012 The Pascal-specific command @code{set print pascal_static-members}
12013 controls whether static members of Pascal objects are displayed.
12014 @xref{Print Settings, pascal_static-members}.
12017 @subsection Modula-2
12019 @cindex Modula-2, @value{GDBN} support
12021 The extensions made to @value{GDBN} to support Modula-2 only support
12022 output from the @sc{gnu} Modula-2 compiler (which is currently being
12023 developed). Other Modula-2 compilers are not currently supported, and
12024 attempting to debug executables produced by them is most likely
12025 to give an error as @value{GDBN} reads in the executable's symbol
12028 @cindex expressions in Modula-2
12030 * M2 Operators:: Built-in operators
12031 * Built-In Func/Proc:: Built-in functions and procedures
12032 * M2 Constants:: Modula-2 constants
12033 * M2 Types:: Modula-2 types
12034 * M2 Defaults:: Default settings for Modula-2
12035 * Deviations:: Deviations from standard Modula-2
12036 * M2 Checks:: Modula-2 type and range checks
12037 * M2 Scope:: The scope operators @code{::} and @code{.}
12038 * GDB/M2:: @value{GDBN} and Modula-2
12042 @subsubsection Operators
12043 @cindex Modula-2 operators
12045 Operators must be defined on values of specific types. For instance,
12046 @code{+} is defined on numbers, but not on structures. Operators are
12047 often defined on groups of types. For the purposes of Modula-2, the
12048 following definitions hold:
12053 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12057 @emph{Character types} consist of @code{CHAR} and its subranges.
12060 @emph{Floating-point types} consist of @code{REAL}.
12063 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12067 @emph{Scalar types} consist of all of the above.
12070 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12073 @emph{Boolean types} consist of @code{BOOLEAN}.
12077 The following operators are supported, and appear in order of
12078 increasing precedence:
12082 Function argument or array index separator.
12085 Assignment. The value of @var{var} @code{:=} @var{value} is
12089 Less than, greater than on integral, floating-point, or enumerated
12093 Less than or equal to, greater than or equal to
12094 on integral, floating-point and enumerated types, or set inclusion on
12095 set types. Same precedence as @code{<}.
12097 @item =@r{, }<>@r{, }#
12098 Equality and two ways of expressing inequality, valid on scalar types.
12099 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12100 available for inequality, since @code{#} conflicts with the script
12104 Set membership. Defined on set types and the types of their members.
12105 Same precedence as @code{<}.
12108 Boolean disjunction. Defined on boolean types.
12111 Boolean conjunction. Defined on boolean types.
12114 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12117 Addition and subtraction on integral and floating-point types, or union
12118 and difference on set types.
12121 Multiplication on integral and floating-point types, or set intersection
12125 Division on floating-point types, or symmetric set difference on set
12126 types. Same precedence as @code{*}.
12129 Integer division and remainder. Defined on integral types. Same
12130 precedence as @code{*}.
12133 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12136 Pointer dereferencing. Defined on pointer types.
12139 Boolean negation. Defined on boolean types. Same precedence as
12143 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12144 precedence as @code{^}.
12147 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12150 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12154 @value{GDBN} and Modula-2 scope operators.
12158 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12159 treats the use of the operator @code{IN}, or the use of operators
12160 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12161 @code{<=}, and @code{>=} on sets as an error.
12165 @node Built-In Func/Proc
12166 @subsubsection Built-in Functions and Procedures
12167 @cindex Modula-2 built-ins
12169 Modula-2 also makes available several built-in procedures and functions.
12170 In describing these, the following metavariables are used:
12175 represents an @code{ARRAY} variable.
12178 represents a @code{CHAR} constant or variable.
12181 represents a variable or constant of integral type.
12184 represents an identifier that belongs to a set. Generally used in the
12185 same function with the metavariable @var{s}. The type of @var{s} should
12186 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12189 represents a variable or constant of integral or floating-point type.
12192 represents a variable or constant of floating-point type.
12198 represents a variable.
12201 represents a variable or constant of one of many types. See the
12202 explanation of the function for details.
12205 All Modula-2 built-in procedures also return a result, described below.
12209 Returns the absolute value of @var{n}.
12212 If @var{c} is a lower case letter, it returns its upper case
12213 equivalent, otherwise it returns its argument.
12216 Returns the character whose ordinal value is @var{i}.
12219 Decrements the value in the variable @var{v} by one. Returns the new value.
12221 @item DEC(@var{v},@var{i})
12222 Decrements the value in the variable @var{v} by @var{i}. Returns the
12225 @item EXCL(@var{m},@var{s})
12226 Removes the element @var{m} from the set @var{s}. Returns the new
12229 @item FLOAT(@var{i})
12230 Returns the floating point equivalent of the integer @var{i}.
12232 @item HIGH(@var{a})
12233 Returns the index of the last member of @var{a}.
12236 Increments the value in the variable @var{v} by one. Returns the new value.
12238 @item INC(@var{v},@var{i})
12239 Increments the value in the variable @var{v} by @var{i}. Returns the
12242 @item INCL(@var{m},@var{s})
12243 Adds the element @var{m} to the set @var{s} if it is not already
12244 there. Returns the new set.
12247 Returns the maximum value of the type @var{t}.
12250 Returns the minimum value of the type @var{t}.
12253 Returns boolean TRUE if @var{i} is an odd number.
12256 Returns the ordinal value of its argument. For example, the ordinal
12257 value of a character is its @sc{ascii} value (on machines supporting the
12258 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12259 integral, character and enumerated types.
12261 @item SIZE(@var{x})
12262 Returns the size of its argument. @var{x} can be a variable or a type.
12264 @item TRUNC(@var{r})
12265 Returns the integral part of @var{r}.
12267 @item TSIZE(@var{x})
12268 Returns the size of its argument. @var{x} can be a variable or a type.
12270 @item VAL(@var{t},@var{i})
12271 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12275 @emph{Warning:} Sets and their operations are not yet supported, so
12276 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12280 @cindex Modula-2 constants
12282 @subsubsection Constants
12284 @value{GDBN} allows you to express the constants of Modula-2 in the following
12290 Integer constants are simply a sequence of digits. When used in an
12291 expression, a constant is interpreted to be type-compatible with the
12292 rest of the expression. Hexadecimal integers are specified by a
12293 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12296 Floating point constants appear as a sequence of digits, followed by a
12297 decimal point and another sequence of digits. An optional exponent can
12298 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12299 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12300 digits of the floating point constant must be valid decimal (base 10)
12304 Character constants consist of a single character enclosed by a pair of
12305 like quotes, either single (@code{'}) or double (@code{"}). They may
12306 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12307 followed by a @samp{C}.
12310 String constants consist of a sequence of characters enclosed by a
12311 pair of like quotes, either single (@code{'}) or double (@code{"}).
12312 Escape sequences in the style of C are also allowed. @xref{C
12313 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12317 Enumerated constants consist of an enumerated identifier.
12320 Boolean constants consist of the identifiers @code{TRUE} and
12324 Pointer constants consist of integral values only.
12327 Set constants are not yet supported.
12331 @subsubsection Modula-2 Types
12332 @cindex Modula-2 types
12334 Currently @value{GDBN} can print the following data types in Modula-2
12335 syntax: array types, record types, set types, pointer types, procedure
12336 types, enumerated types, subrange types and base types. You can also
12337 print the contents of variables declared using these type.
12338 This section gives a number of simple source code examples together with
12339 sample @value{GDBN} sessions.
12341 The first example contains the following section of code:
12350 and you can request @value{GDBN} to interrogate the type and value of
12351 @code{r} and @code{s}.
12354 (@value{GDBP}) print s
12356 (@value{GDBP}) ptype s
12358 (@value{GDBP}) print r
12360 (@value{GDBP}) ptype r
12365 Likewise if your source code declares @code{s} as:
12369 s: SET ['A'..'Z'] ;
12373 then you may query the type of @code{s} by:
12376 (@value{GDBP}) ptype s
12377 type = SET ['A'..'Z']
12381 Note that at present you cannot interactively manipulate set
12382 expressions using the debugger.
12384 The following example shows how you might declare an array in Modula-2
12385 and how you can interact with @value{GDBN} to print its type and contents:
12389 s: ARRAY [-10..10] OF CHAR ;
12393 (@value{GDBP}) ptype s
12394 ARRAY [-10..10] OF CHAR
12397 Note that the array handling is not yet complete and although the type
12398 is printed correctly, expression handling still assumes that all
12399 arrays have a lower bound of zero and not @code{-10} as in the example
12402 Here are some more type related Modula-2 examples:
12406 colour = (blue, red, yellow, green) ;
12407 t = [blue..yellow] ;
12415 The @value{GDBN} interaction shows how you can query the data type
12416 and value of a variable.
12419 (@value{GDBP}) print s
12421 (@value{GDBP}) ptype t
12422 type = [blue..yellow]
12426 In this example a Modula-2 array is declared and its contents
12427 displayed. Observe that the contents are written in the same way as
12428 their @code{C} counterparts.
12432 s: ARRAY [1..5] OF CARDINAL ;
12438 (@value{GDBP}) print s
12439 $1 = @{1, 0, 0, 0, 0@}
12440 (@value{GDBP}) ptype s
12441 type = ARRAY [1..5] OF CARDINAL
12444 The Modula-2 language interface to @value{GDBN} also understands
12445 pointer types as shown in this example:
12449 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12456 and you can request that @value{GDBN} describes the type of @code{s}.
12459 (@value{GDBP}) ptype s
12460 type = POINTER TO ARRAY [1..5] OF CARDINAL
12463 @value{GDBN} handles compound types as we can see in this example.
12464 Here we combine array types, record types, pointer types and subrange
12475 myarray = ARRAY myrange OF CARDINAL ;
12476 myrange = [-2..2] ;
12478 s: POINTER TO ARRAY myrange OF foo ;
12482 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12486 (@value{GDBP}) ptype s
12487 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12490 f3 : ARRAY [-2..2] OF CARDINAL;
12495 @subsubsection Modula-2 Defaults
12496 @cindex Modula-2 defaults
12498 If type and range checking are set automatically by @value{GDBN}, they
12499 both default to @code{on} whenever the working language changes to
12500 Modula-2. This happens regardless of whether you or @value{GDBN}
12501 selected the working language.
12503 If you allow @value{GDBN} to set the language automatically, then entering
12504 code compiled from a file whose name ends with @file{.mod} sets the
12505 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12506 Infer the Source Language}, for further details.
12509 @subsubsection Deviations from Standard Modula-2
12510 @cindex Modula-2, deviations from
12512 A few changes have been made to make Modula-2 programs easier to debug.
12513 This is done primarily via loosening its type strictness:
12517 Unlike in standard Modula-2, pointer constants can be formed by
12518 integers. This allows you to modify pointer variables during
12519 debugging. (In standard Modula-2, the actual address contained in a
12520 pointer variable is hidden from you; it can only be modified
12521 through direct assignment to another pointer variable or expression that
12522 returned a pointer.)
12525 C escape sequences can be used in strings and characters to represent
12526 non-printable characters. @value{GDBN} prints out strings with these
12527 escape sequences embedded. Single non-printable characters are
12528 printed using the @samp{CHR(@var{nnn})} format.
12531 The assignment operator (@code{:=}) returns the value of its right-hand
12535 All built-in procedures both modify @emph{and} return their argument.
12539 @subsubsection Modula-2 Type and Range Checks
12540 @cindex Modula-2 checks
12543 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12546 @c FIXME remove warning when type/range checks added
12548 @value{GDBN} considers two Modula-2 variables type equivalent if:
12552 They are of types that have been declared equivalent via a @code{TYPE
12553 @var{t1} = @var{t2}} statement
12556 They have been declared on the same line. (Note: This is true of the
12557 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12560 As long as type checking is enabled, any attempt to combine variables
12561 whose types are not equivalent is an error.
12563 Range checking is done on all mathematical operations, assignment, array
12564 index bounds, and all built-in functions and procedures.
12567 @subsubsection The Scope Operators @code{::} and @code{.}
12569 @cindex @code{.}, Modula-2 scope operator
12570 @cindex colon, doubled as scope operator
12572 @vindex colon-colon@r{, in Modula-2}
12573 @c Info cannot handle :: but TeX can.
12576 @vindex ::@r{, in Modula-2}
12579 There are a few subtle differences between the Modula-2 scope operator
12580 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12585 @var{module} . @var{id}
12586 @var{scope} :: @var{id}
12590 where @var{scope} is the name of a module or a procedure,
12591 @var{module} the name of a module, and @var{id} is any declared
12592 identifier within your program, except another module.
12594 Using the @code{::} operator makes @value{GDBN} search the scope
12595 specified by @var{scope} for the identifier @var{id}. If it is not
12596 found in the specified scope, then @value{GDBN} searches all scopes
12597 enclosing the one specified by @var{scope}.
12599 Using the @code{.} operator makes @value{GDBN} search the current scope for
12600 the identifier specified by @var{id} that was imported from the
12601 definition module specified by @var{module}. With this operator, it is
12602 an error if the identifier @var{id} was not imported from definition
12603 module @var{module}, or if @var{id} is not an identifier in
12607 @subsubsection @value{GDBN} and Modula-2
12609 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12610 Five subcommands of @code{set print} and @code{show print} apply
12611 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12612 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12613 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12614 analogue in Modula-2.
12616 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12617 with any language, is not useful with Modula-2. Its
12618 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12619 created in Modula-2 as they can in C or C@t{++}. However, because an
12620 address can be specified by an integral constant, the construct
12621 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12623 @cindex @code{#} in Modula-2
12624 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12625 interpreted as the beginning of a comment. Use @code{<>} instead.
12631 The extensions made to @value{GDBN} for Ada only support
12632 output from the @sc{gnu} Ada (GNAT) compiler.
12633 Other Ada compilers are not currently supported, and
12634 attempting to debug executables produced by them is most likely
12638 @cindex expressions in Ada
12640 * Ada Mode Intro:: General remarks on the Ada syntax
12641 and semantics supported by Ada mode
12643 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12644 * Additions to Ada:: Extensions of the Ada expression syntax.
12645 * Stopping Before Main Program:: Debugging the program during elaboration.
12646 * Ada Tasks:: Listing and setting breakpoints in tasks.
12647 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12648 * Ada Glitches:: Known peculiarities of Ada mode.
12651 @node Ada Mode Intro
12652 @subsubsection Introduction
12653 @cindex Ada mode, general
12655 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12656 syntax, with some extensions.
12657 The philosophy behind the design of this subset is
12661 That @value{GDBN} should provide basic literals and access to operations for
12662 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12663 leaving more sophisticated computations to subprograms written into the
12664 program (which therefore may be called from @value{GDBN}).
12667 That type safety and strict adherence to Ada language restrictions
12668 are not particularly important to the @value{GDBN} user.
12671 That brevity is important to the @value{GDBN} user.
12674 Thus, for brevity, the debugger acts as if all names declared in
12675 user-written packages are directly visible, even if they are not visible
12676 according to Ada rules, thus making it unnecessary to fully qualify most
12677 names with their packages, regardless of context. Where this causes
12678 ambiguity, @value{GDBN} asks the user's intent.
12680 The debugger will start in Ada mode if it detects an Ada main program.
12681 As for other languages, it will enter Ada mode when stopped in a program that
12682 was translated from an Ada source file.
12684 While in Ada mode, you may use `@t{--}' for comments. This is useful
12685 mostly for documenting command files. The standard @value{GDBN} comment
12686 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12687 middle (to allow based literals).
12689 The debugger supports limited overloading. Given a subprogram call in which
12690 the function symbol has multiple definitions, it will use the number of
12691 actual parameters and some information about their types to attempt to narrow
12692 the set of definitions. It also makes very limited use of context, preferring
12693 procedures to functions in the context of the @code{call} command, and
12694 functions to procedures elsewhere.
12696 @node Omissions from Ada
12697 @subsubsection Omissions from Ada
12698 @cindex Ada, omissions from
12700 Here are the notable omissions from the subset:
12704 Only a subset of the attributes are supported:
12708 @t{'First}, @t{'Last}, and @t{'Length}
12709 on array objects (not on types and subtypes).
12712 @t{'Min} and @t{'Max}.
12715 @t{'Pos} and @t{'Val}.
12721 @t{'Range} on array objects (not subtypes), but only as the right
12722 operand of the membership (@code{in}) operator.
12725 @t{'Access}, @t{'Unchecked_Access}, and
12726 @t{'Unrestricted_Access} (a GNAT extension).
12734 @code{Characters.Latin_1} are not available and
12735 concatenation is not implemented. Thus, escape characters in strings are
12736 not currently available.
12739 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12740 equality of representations. They will generally work correctly
12741 for strings and arrays whose elements have integer or enumeration types.
12742 They may not work correctly for arrays whose element
12743 types have user-defined equality, for arrays of real values
12744 (in particular, IEEE-conformant floating point, because of negative
12745 zeroes and NaNs), and for arrays whose elements contain unused bits with
12746 indeterminate values.
12749 The other component-by-component array operations (@code{and}, @code{or},
12750 @code{xor}, @code{not}, and relational tests other than equality)
12751 are not implemented.
12754 @cindex array aggregates (Ada)
12755 @cindex record aggregates (Ada)
12756 @cindex aggregates (Ada)
12757 There is limited support for array and record aggregates. They are
12758 permitted only on the right sides of assignments, as in these examples:
12761 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12762 (@value{GDBP}) set An_Array := (1, others => 0)
12763 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12764 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12765 (@value{GDBP}) set A_Record := (1, "Peter", True);
12766 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12770 discriminant's value by assigning an aggregate has an
12771 undefined effect if that discriminant is used within the record.
12772 However, you can first modify discriminants by directly assigning to
12773 them (which normally would not be allowed in Ada), and then performing an
12774 aggregate assignment. For example, given a variable @code{A_Rec}
12775 declared to have a type such as:
12778 type Rec (Len : Small_Integer := 0) is record
12780 Vals : IntArray (1 .. Len);
12784 you can assign a value with a different size of @code{Vals} with two
12788 (@value{GDBP}) set A_Rec.Len := 4
12789 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12792 As this example also illustrates, @value{GDBN} is very loose about the usual
12793 rules concerning aggregates. You may leave out some of the
12794 components of an array or record aggregate (such as the @code{Len}
12795 component in the assignment to @code{A_Rec} above); they will retain their
12796 original values upon assignment. You may freely use dynamic values as
12797 indices in component associations. You may even use overlapping or
12798 redundant component associations, although which component values are
12799 assigned in such cases is not defined.
12802 Calls to dispatching subprograms are not implemented.
12805 The overloading algorithm is much more limited (i.e., less selective)
12806 than that of real Ada. It makes only limited use of the context in
12807 which a subexpression appears to resolve its meaning, and it is much
12808 looser in its rules for allowing type matches. As a result, some
12809 function calls will be ambiguous, and the user will be asked to choose
12810 the proper resolution.
12813 The @code{new} operator is not implemented.
12816 Entry calls are not implemented.
12819 Aside from printing, arithmetic operations on the native VAX floating-point
12820 formats are not supported.
12823 It is not possible to slice a packed array.
12826 The names @code{True} and @code{False}, when not part of a qualified name,
12827 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12829 Should your program
12830 redefine these names in a package or procedure (at best a dubious practice),
12831 you will have to use fully qualified names to access their new definitions.
12834 @node Additions to Ada
12835 @subsubsection Additions to Ada
12836 @cindex Ada, deviations from
12838 As it does for other languages, @value{GDBN} makes certain generic
12839 extensions to Ada (@pxref{Expressions}):
12843 If the expression @var{E} is a variable residing in memory (typically
12844 a local variable or array element) and @var{N} is a positive integer,
12845 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12846 @var{N}-1 adjacent variables following it in memory as an array. In
12847 Ada, this operator is generally not necessary, since its prime use is
12848 in displaying parts of an array, and slicing will usually do this in
12849 Ada. However, there are occasional uses when debugging programs in
12850 which certain debugging information has been optimized away.
12853 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12854 appears in function or file @var{B}.'' When @var{B} is a file name,
12855 you must typically surround it in single quotes.
12858 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12859 @var{type} that appears at address @var{addr}.''
12862 A name starting with @samp{$} is a convenience variable
12863 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12866 In addition, @value{GDBN} provides a few other shortcuts and outright
12867 additions specific to Ada:
12871 The assignment statement is allowed as an expression, returning
12872 its right-hand operand as its value. Thus, you may enter
12875 (@value{GDBP}) set x := y + 3
12876 (@value{GDBP}) print A(tmp := y + 1)
12880 The semicolon is allowed as an ``operator,'' returning as its value
12881 the value of its right-hand operand.
12882 This allows, for example,
12883 complex conditional breaks:
12886 (@value{GDBP}) break f
12887 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12891 Rather than use catenation and symbolic character names to introduce special
12892 characters into strings, one may instead use a special bracket notation,
12893 which is also used to print strings. A sequence of characters of the form
12894 @samp{["@var{XX}"]} within a string or character literal denotes the
12895 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12896 sequence of characters @samp{["""]} also denotes a single quotation mark
12897 in strings. For example,
12899 "One line.["0a"]Next line.["0a"]"
12902 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12906 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12907 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12911 (@value{GDBP}) print 'max(x, y)
12915 When printing arrays, @value{GDBN} uses positional notation when the
12916 array has a lower bound of 1, and uses a modified named notation otherwise.
12917 For example, a one-dimensional array of three integers with a lower bound
12918 of 3 might print as
12925 That is, in contrast to valid Ada, only the first component has a @code{=>}
12929 You may abbreviate attributes in expressions with any unique,
12930 multi-character subsequence of
12931 their names (an exact match gets preference).
12932 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12933 in place of @t{a'length}.
12936 @cindex quoting Ada internal identifiers
12937 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12938 to lower case. The GNAT compiler uses upper-case characters for
12939 some of its internal identifiers, which are normally of no interest to users.
12940 For the rare occasions when you actually have to look at them,
12941 enclose them in angle brackets to avoid the lower-case mapping.
12944 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12948 Printing an object of class-wide type or dereferencing an
12949 access-to-class-wide value will display all the components of the object's
12950 specific type (as indicated by its run-time tag). Likewise, component
12951 selection on such a value will operate on the specific type of the
12956 @node Stopping Before Main Program
12957 @subsubsection Stopping at the Very Beginning
12959 @cindex breakpointing Ada elaboration code
12960 It is sometimes necessary to debug the program during elaboration, and
12961 before reaching the main procedure.
12962 As defined in the Ada Reference
12963 Manual, the elaboration code is invoked from a procedure called
12964 @code{adainit}. To run your program up to the beginning of
12965 elaboration, simply use the following two commands:
12966 @code{tbreak adainit} and @code{run}.
12969 @subsubsection Extensions for Ada Tasks
12970 @cindex Ada, tasking
12972 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12973 @value{GDBN} provides the following task-related commands:
12978 This command shows a list of current Ada tasks, as in the following example:
12985 (@value{GDBP}) info tasks
12986 ID TID P-ID Pri State Name
12987 1 8088000 0 15 Child Activation Wait main_task
12988 2 80a4000 1 15 Accept Statement b
12989 3 809a800 1 15 Child Activation Wait a
12990 * 4 80ae800 3 15 Runnable c
12995 In this listing, the asterisk before the last task indicates it to be the
12996 task currently being inspected.
13000 Represents @value{GDBN}'s internal task number.
13006 The parent's task ID (@value{GDBN}'s internal task number).
13009 The base priority of the task.
13012 Current state of the task.
13016 The task has been created but has not been activated. It cannot be
13020 The task is not blocked for any reason known to Ada. (It may be waiting
13021 for a mutex, though.) It is conceptually "executing" in normal mode.
13024 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13025 that were waiting on terminate alternatives have been awakened and have
13026 terminated themselves.
13028 @item Child Activation Wait
13029 The task is waiting for created tasks to complete activation.
13031 @item Accept Statement
13032 The task is waiting on an accept or selective wait statement.
13034 @item Waiting on entry call
13035 The task is waiting on an entry call.
13037 @item Async Select Wait
13038 The task is waiting to start the abortable part of an asynchronous
13042 The task is waiting on a select statement with only a delay
13045 @item Child Termination Wait
13046 The task is sleeping having completed a master within itself, and is
13047 waiting for the tasks dependent on that master to become terminated or
13048 waiting on a terminate Phase.
13050 @item Wait Child in Term Alt
13051 The task is sleeping waiting for tasks on terminate alternatives to
13052 finish terminating.
13054 @item Accepting RV with @var{taskno}
13055 The task is accepting a rendez-vous with the task @var{taskno}.
13059 Name of the task in the program.
13063 @kindex info task @var{taskno}
13064 @item info task @var{taskno}
13065 This command shows detailled informations on the specified task, as in
13066 the following example:
13071 (@value{GDBP}) info tasks
13072 ID TID P-ID Pri State Name
13073 1 8077880 0 15 Child Activation Wait main_task
13074 * 2 807c468 1 15 Runnable task_1
13075 (@value{GDBP}) info task 2
13076 Ada Task: 0x807c468
13079 Parent: 1 (main_task)
13085 @kindex task@r{ (Ada)}
13086 @cindex current Ada task ID
13087 This command prints the ID of the current task.
13093 (@value{GDBP}) info tasks
13094 ID TID P-ID Pri State Name
13095 1 8077870 0 15 Child Activation Wait main_task
13096 * 2 807c458 1 15 Runnable t
13097 (@value{GDBP}) task
13098 [Current task is 2]
13101 @item task @var{taskno}
13102 @cindex Ada task switching
13103 This command is like the @code{thread @var{threadno}}
13104 command (@pxref{Threads}). It switches the context of debugging
13105 from the current task to the given task.
13111 (@value{GDBP}) info tasks
13112 ID TID P-ID Pri State Name
13113 1 8077870 0 15 Child Activation Wait main_task
13114 * 2 807c458 1 15 Runnable t
13115 (@value{GDBP}) task 1
13116 [Switching to task 1]
13117 #0 0x8067726 in pthread_cond_wait ()
13119 #0 0x8067726 in pthread_cond_wait ()
13120 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13121 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13122 #3 0x806153e in system.tasking.stages.activate_tasks ()
13123 #4 0x804aacc in un () at un.adb:5
13126 @item break @var{linespec} task @var{taskno}
13127 @itemx break @var{linespec} task @var{taskno} if @dots{}
13128 @cindex breakpoints and tasks, in Ada
13129 @cindex task breakpoints, in Ada
13130 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13131 These commands are like the @code{break @dots{} thread @dots{}}
13132 command (@pxref{Thread Stops}).
13133 @var{linespec} specifies source lines, as described
13134 in @ref{Specify Location}.
13136 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13137 to specify that you only want @value{GDBN} to stop the program when a
13138 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13139 numeric task identifiers assigned by @value{GDBN}, shown in the first
13140 column of the @samp{info tasks} display.
13142 If you do not specify @samp{task @var{taskno}} when you set a
13143 breakpoint, the breakpoint applies to @emph{all} tasks of your
13146 You can use the @code{task} qualifier on conditional breakpoints as
13147 well; in this case, place @samp{task @var{taskno}} before the
13148 breakpoint condition (before the @code{if}).
13156 (@value{GDBP}) info tasks
13157 ID TID P-ID Pri State Name
13158 1 140022020 0 15 Child Activation Wait main_task
13159 2 140045060 1 15 Accept/Select Wait t2
13160 3 140044840 1 15 Runnable t1
13161 * 4 140056040 1 15 Runnable t3
13162 (@value{GDBP}) b 15 task 2
13163 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13164 (@value{GDBP}) cont
13169 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13171 (@value{GDBP}) info tasks
13172 ID TID P-ID Pri State Name
13173 1 140022020 0 15 Child Activation Wait main_task
13174 * 2 140045060 1 15 Runnable t2
13175 3 140044840 1 15 Runnable t1
13176 4 140056040 1 15 Delay Sleep t3
13180 @node Ada Tasks and Core Files
13181 @subsubsection Tasking Support when Debugging Core Files
13182 @cindex Ada tasking and core file debugging
13184 When inspecting a core file, as opposed to debugging a live program,
13185 tasking support may be limited or even unavailable, depending on
13186 the platform being used.
13187 For instance, on x86-linux, the list of tasks is available, but task
13188 switching is not supported. On Tru64, however, task switching will work
13191 On certain platforms, including Tru64, the debugger needs to perform some
13192 memory writes in order to provide Ada tasking support. When inspecting
13193 a core file, this means that the core file must be opened with read-write
13194 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13195 Under these circumstances, you should make a backup copy of the core
13196 file before inspecting it with @value{GDBN}.
13199 @subsubsection Known Peculiarities of Ada Mode
13200 @cindex Ada, problems
13202 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13203 we know of several problems with and limitations of Ada mode in
13205 some of which will be fixed with planned future releases of the debugger
13206 and the GNU Ada compiler.
13210 Currently, the debugger
13211 has insufficient information to determine whether certain pointers represent
13212 pointers to objects or the objects themselves.
13213 Thus, the user may have to tack an extra @code{.all} after an expression
13214 to get it printed properly.
13217 Static constants that the compiler chooses not to materialize as objects in
13218 storage are invisible to the debugger.
13221 Named parameter associations in function argument lists are ignored (the
13222 argument lists are treated as positional).
13225 Many useful library packages are currently invisible to the debugger.
13228 Fixed-point arithmetic, conversions, input, and output is carried out using
13229 floating-point arithmetic, and may give results that only approximate those on
13233 The GNAT compiler never generates the prefix @code{Standard} for any of
13234 the standard symbols defined by the Ada language. @value{GDBN} knows about
13235 this: it will strip the prefix from names when you use it, and will never
13236 look for a name you have so qualified among local symbols, nor match against
13237 symbols in other packages or subprograms. If you have
13238 defined entities anywhere in your program other than parameters and
13239 local variables whose simple names match names in @code{Standard},
13240 GNAT's lack of qualification here can cause confusion. When this happens,
13241 you can usually resolve the confusion
13242 by qualifying the problematic names with package
13243 @code{Standard} explicitly.
13246 Older versions of the compiler sometimes generate erroneous debugging
13247 information, resulting in the debugger incorrectly printing the value
13248 of affected entities. In some cases, the debugger is able to work
13249 around an issue automatically. In other cases, the debugger is able
13250 to work around the issue, but the work-around has to be specifically
13253 @kindex set ada trust-PAD-over-XVS
13254 @kindex show ada trust-PAD-over-XVS
13257 @item set ada trust-PAD-over-XVS on
13258 Configure GDB to strictly follow the GNAT encoding when computing the
13259 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13260 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13261 a complete description of the encoding used by the GNAT compiler).
13262 This is the default.
13264 @item set ada trust-PAD-over-XVS off
13265 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13266 sometimes prints the wrong value for certain entities, changing @code{ada
13267 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13268 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13269 @code{off}, but this incurs a slight performance penalty, so it is
13270 recommended to leave this setting to @code{on} unless necessary.
13274 @node Unsupported Languages
13275 @section Unsupported Languages
13277 @cindex unsupported languages
13278 @cindex minimal language
13279 In addition to the other fully-supported programming languages,
13280 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13281 It does not represent a real programming language, but provides a set
13282 of capabilities close to what the C or assembly languages provide.
13283 This should allow most simple operations to be performed while debugging
13284 an application that uses a language currently not supported by @value{GDBN}.
13286 If the language is set to @code{auto}, @value{GDBN} will automatically
13287 select this language if the current frame corresponds to an unsupported
13291 @chapter Examining the Symbol Table
13293 The commands described in this chapter allow you to inquire about the
13294 symbols (names of variables, functions and types) defined in your
13295 program. This information is inherent in the text of your program and
13296 does not change as your program executes. @value{GDBN} finds it in your
13297 program's symbol table, in the file indicated when you started @value{GDBN}
13298 (@pxref{File Options, ,Choosing Files}), or by one of the
13299 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13301 @cindex symbol names
13302 @cindex names of symbols
13303 @cindex quoting names
13304 Occasionally, you may need to refer to symbols that contain unusual
13305 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13306 most frequent case is in referring to static variables in other
13307 source files (@pxref{Variables,,Program Variables}). File names
13308 are recorded in object files as debugging symbols, but @value{GDBN} would
13309 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13310 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13311 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13318 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13321 @cindex case-insensitive symbol names
13322 @cindex case sensitivity in symbol names
13323 @kindex set case-sensitive
13324 @item set case-sensitive on
13325 @itemx set case-sensitive off
13326 @itemx set case-sensitive auto
13327 Normally, when @value{GDBN} looks up symbols, it matches their names
13328 with case sensitivity determined by the current source language.
13329 Occasionally, you may wish to control that. The command @code{set
13330 case-sensitive} lets you do that by specifying @code{on} for
13331 case-sensitive matches or @code{off} for case-insensitive ones. If
13332 you specify @code{auto}, case sensitivity is reset to the default
13333 suitable for the source language. The default is case-sensitive
13334 matches for all languages except for Fortran, for which the default is
13335 case-insensitive matches.
13337 @kindex show case-sensitive
13338 @item show case-sensitive
13339 This command shows the current setting of case sensitivity for symbols
13342 @kindex info address
13343 @cindex address of a symbol
13344 @item info address @var{symbol}
13345 Describe where the data for @var{symbol} is stored. For a register
13346 variable, this says which register it is kept in. For a non-register
13347 local variable, this prints the stack-frame offset at which the variable
13350 Note the contrast with @samp{print &@var{symbol}}, which does not work
13351 at all for a register variable, and for a stack local variable prints
13352 the exact address of the current instantiation of the variable.
13354 @kindex info symbol
13355 @cindex symbol from address
13356 @cindex closest symbol and offset for an address
13357 @item info symbol @var{addr}
13358 Print the name of a symbol which is stored at the address @var{addr}.
13359 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13360 nearest symbol and an offset from it:
13363 (@value{GDBP}) info symbol 0x54320
13364 _initialize_vx + 396 in section .text
13368 This is the opposite of the @code{info address} command. You can use
13369 it to find out the name of a variable or a function given its address.
13371 For dynamically linked executables, the name of executable or shared
13372 library containing the symbol is also printed:
13375 (@value{GDBP}) info symbol 0x400225
13376 _start + 5 in section .text of /tmp/a.out
13377 (@value{GDBP}) info symbol 0x2aaaac2811cf
13378 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13382 @item whatis [@var{arg}]
13383 Print the data type of @var{arg}, which can be either an expression or
13384 a data type. With no argument, print the data type of @code{$}, the
13385 last value in the value history. If @var{arg} is an expression, it is
13386 not actually evaluated, and any side-effecting operations (such as
13387 assignments or function calls) inside it do not take place. If
13388 @var{arg} is a type name, it may be the name of a type or typedef, or
13389 for C code it may have the form @samp{class @var{class-name}},
13390 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13391 @samp{enum @var{enum-tag}}.
13392 @xref{Expressions, ,Expressions}.
13395 @item ptype [@var{arg}]
13396 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13397 detailed description of the type, instead of just the name of the type.
13398 @xref{Expressions, ,Expressions}.
13400 For example, for this variable declaration:
13403 struct complex @{double real; double imag;@} v;
13407 the two commands give this output:
13411 (@value{GDBP}) whatis v
13412 type = struct complex
13413 (@value{GDBP}) ptype v
13414 type = struct complex @{
13422 As with @code{whatis}, using @code{ptype} without an argument refers to
13423 the type of @code{$}, the last value in the value history.
13425 @cindex incomplete type
13426 Sometimes, programs use opaque data types or incomplete specifications
13427 of complex data structure. If the debug information included in the
13428 program does not allow @value{GDBN} to display a full declaration of
13429 the data type, it will say @samp{<incomplete type>}. For example,
13430 given these declarations:
13434 struct foo *fooptr;
13438 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13441 (@value{GDBP}) ptype foo
13442 $1 = <incomplete type>
13446 ``Incomplete type'' is C terminology for data types that are not
13447 completely specified.
13450 @item info types @var{regexp}
13452 Print a brief description of all types whose names match the regular
13453 expression @var{regexp} (or all types in your program, if you supply
13454 no argument). Each complete typename is matched as though it were a
13455 complete line; thus, @samp{i type value} gives information on all
13456 types in your program whose names include the string @code{value}, but
13457 @samp{i type ^value$} gives information only on types whose complete
13458 name is @code{value}.
13460 This command differs from @code{ptype} in two ways: first, like
13461 @code{whatis}, it does not print a detailed description; second, it
13462 lists all source files where a type is defined.
13465 @cindex local variables
13466 @item info scope @var{location}
13467 List all the variables local to a particular scope. This command
13468 accepts a @var{location} argument---a function name, a source line, or
13469 an address preceded by a @samp{*}, and prints all the variables local
13470 to the scope defined by that location. (@xref{Specify Location}, for
13471 details about supported forms of @var{location}.) For example:
13474 (@value{GDBP}) @b{info scope command_line_handler}
13475 Scope for command_line_handler:
13476 Symbol rl is an argument at stack/frame offset 8, length 4.
13477 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13478 Symbol linelength is in static storage at address 0x150a1c, length 4.
13479 Symbol p is a local variable in register $esi, length 4.
13480 Symbol p1 is a local variable in register $ebx, length 4.
13481 Symbol nline is a local variable in register $edx, length 4.
13482 Symbol repeat is a local variable at frame offset -8, length 4.
13486 This command is especially useful for determining what data to collect
13487 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13490 @kindex info source
13492 Show information about the current source file---that is, the source file for
13493 the function containing the current point of execution:
13496 the name of the source file, and the directory containing it,
13498 the directory it was compiled in,
13500 its length, in lines,
13502 which programming language it is written in,
13504 whether the executable includes debugging information for that file, and
13505 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13507 whether the debugging information includes information about
13508 preprocessor macros.
13512 @kindex info sources
13514 Print the names of all source files in your program for which there is
13515 debugging information, organized into two lists: files whose symbols
13516 have already been read, and files whose symbols will be read when needed.
13518 @kindex info functions
13519 @item info functions
13520 Print the names and data types of all defined functions.
13522 @item info functions @var{regexp}
13523 Print the names and data types of all defined functions
13524 whose names contain a match for regular expression @var{regexp}.
13525 Thus, @samp{info fun step} finds all functions whose names
13526 include @code{step}; @samp{info fun ^step} finds those whose names
13527 start with @code{step}. If a function name contains characters
13528 that conflict with the regular expression language (e.g.@:
13529 @samp{operator*()}), they may be quoted with a backslash.
13531 @kindex info variables
13532 @item info variables
13533 Print the names and data types of all variables that are defined
13534 outside of functions (i.e.@: excluding local variables).
13536 @item info variables @var{regexp}
13537 Print the names and data types of all variables (except for local
13538 variables) whose names contain a match for regular expression
13541 @kindex info classes
13542 @cindex Objective-C, classes and selectors
13544 @itemx info classes @var{regexp}
13545 Display all Objective-C classes in your program, or
13546 (with the @var{regexp} argument) all those matching a particular regular
13549 @kindex info selectors
13550 @item info selectors
13551 @itemx info selectors @var{regexp}
13552 Display all Objective-C selectors in your program, or
13553 (with the @var{regexp} argument) all those matching a particular regular
13557 This was never implemented.
13558 @kindex info methods
13560 @itemx info methods @var{regexp}
13561 The @code{info methods} command permits the user to examine all defined
13562 methods within C@t{++} program, or (with the @var{regexp} argument) a
13563 specific set of methods found in the various C@t{++} classes. Many
13564 C@t{++} classes provide a large number of methods. Thus, the output
13565 from the @code{ptype} command can be overwhelming and hard to use. The
13566 @code{info-methods} command filters the methods, printing only those
13567 which match the regular-expression @var{regexp}.
13570 @cindex reloading symbols
13571 Some systems allow individual object files that make up your program to
13572 be replaced without stopping and restarting your program. For example,
13573 in VxWorks you can simply recompile a defective object file and keep on
13574 running. If you are running on one of these systems, you can allow
13575 @value{GDBN} to reload the symbols for automatically relinked modules:
13578 @kindex set symbol-reloading
13579 @item set symbol-reloading on
13580 Replace symbol definitions for the corresponding source file when an
13581 object file with a particular name is seen again.
13583 @item set symbol-reloading off
13584 Do not replace symbol definitions when encountering object files of the
13585 same name more than once. This is the default state; if you are not
13586 running on a system that permits automatic relinking of modules, you
13587 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13588 may discard symbols when linking large programs, that may contain
13589 several modules (from different directories or libraries) with the same
13592 @kindex show symbol-reloading
13593 @item show symbol-reloading
13594 Show the current @code{on} or @code{off} setting.
13597 @cindex opaque data types
13598 @kindex set opaque-type-resolution
13599 @item set opaque-type-resolution on
13600 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13601 declared as a pointer to a @code{struct}, @code{class}, or
13602 @code{union}---for example, @code{struct MyType *}---that is used in one
13603 source file although the full declaration of @code{struct MyType} is in
13604 another source file. The default is on.
13606 A change in the setting of this subcommand will not take effect until
13607 the next time symbols for a file are loaded.
13609 @item set opaque-type-resolution off
13610 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13611 is printed as follows:
13613 @{<no data fields>@}
13616 @kindex show opaque-type-resolution
13617 @item show opaque-type-resolution
13618 Show whether opaque types are resolved or not.
13620 @kindex maint print symbols
13621 @cindex symbol dump
13622 @kindex maint print psymbols
13623 @cindex partial symbol dump
13624 @item maint print symbols @var{filename}
13625 @itemx maint print psymbols @var{filename}
13626 @itemx maint print msymbols @var{filename}
13627 Write a dump of debugging symbol data into the file @var{filename}.
13628 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13629 symbols with debugging data are included. If you use @samp{maint print
13630 symbols}, @value{GDBN} includes all the symbols for which it has already
13631 collected full details: that is, @var{filename} reflects symbols for
13632 only those files whose symbols @value{GDBN} has read. You can use the
13633 command @code{info sources} to find out which files these are. If you
13634 use @samp{maint print psymbols} instead, the dump shows information about
13635 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13636 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13637 @samp{maint print msymbols} dumps just the minimal symbol information
13638 required for each object file from which @value{GDBN} has read some symbols.
13639 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13640 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13642 @kindex maint info symtabs
13643 @kindex maint info psymtabs
13644 @cindex listing @value{GDBN}'s internal symbol tables
13645 @cindex symbol tables, listing @value{GDBN}'s internal
13646 @cindex full symbol tables, listing @value{GDBN}'s internal
13647 @cindex partial symbol tables, listing @value{GDBN}'s internal
13648 @item maint info symtabs @r{[} @var{regexp} @r{]}
13649 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13651 List the @code{struct symtab} or @code{struct partial_symtab}
13652 structures whose names match @var{regexp}. If @var{regexp} is not
13653 given, list them all. The output includes expressions which you can
13654 copy into a @value{GDBN} debugging this one to examine a particular
13655 structure in more detail. For example:
13658 (@value{GDBP}) maint info psymtabs dwarf2read
13659 @{ objfile /home/gnu/build/gdb/gdb
13660 ((struct objfile *) 0x82e69d0)
13661 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13662 ((struct partial_symtab *) 0x8474b10)
13665 text addresses 0x814d3c8 -- 0x8158074
13666 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13667 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13668 dependencies (none)
13671 (@value{GDBP}) maint info symtabs
13675 We see that there is one partial symbol table whose filename contains
13676 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13677 and we see that @value{GDBN} has not read in any symtabs yet at all.
13678 If we set a breakpoint on a function, that will cause @value{GDBN} to
13679 read the symtab for the compilation unit containing that function:
13682 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13683 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13685 (@value{GDBP}) maint info symtabs
13686 @{ objfile /home/gnu/build/gdb/gdb
13687 ((struct objfile *) 0x82e69d0)
13688 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13689 ((struct symtab *) 0x86c1f38)
13692 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13693 linetable ((struct linetable *) 0x8370fa0)
13694 debugformat DWARF 2
13703 @chapter Altering Execution
13705 Once you think you have found an error in your program, you might want to
13706 find out for certain whether correcting the apparent error would lead to
13707 correct results in the rest of the run. You can find the answer by
13708 experiment, using the @value{GDBN} features for altering execution of the
13711 For example, you can store new values into variables or memory
13712 locations, give your program a signal, restart it at a different
13713 address, or even return prematurely from a function.
13716 * Assignment:: Assignment to variables
13717 * Jumping:: Continuing at a different address
13718 * Signaling:: Giving your program a signal
13719 * Returning:: Returning from a function
13720 * Calling:: Calling your program's functions
13721 * Patching:: Patching your program
13725 @section Assignment to Variables
13728 @cindex setting variables
13729 To alter the value of a variable, evaluate an assignment expression.
13730 @xref{Expressions, ,Expressions}. For example,
13737 stores the value 4 into the variable @code{x}, and then prints the
13738 value of the assignment expression (which is 4).
13739 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13740 information on operators in supported languages.
13742 @kindex set variable
13743 @cindex variables, setting
13744 If you are not interested in seeing the value of the assignment, use the
13745 @code{set} command instead of the @code{print} command. @code{set} is
13746 really the same as @code{print} except that the expression's value is
13747 not printed and is not put in the value history (@pxref{Value History,
13748 ,Value History}). The expression is evaluated only for its effects.
13750 If the beginning of the argument string of the @code{set} command
13751 appears identical to a @code{set} subcommand, use the @code{set
13752 variable} command instead of just @code{set}. This command is identical
13753 to @code{set} except for its lack of subcommands. For example, if your
13754 program has a variable @code{width}, you get an error if you try to set
13755 a new value with just @samp{set width=13}, because @value{GDBN} has the
13756 command @code{set width}:
13759 (@value{GDBP}) whatis width
13761 (@value{GDBP}) p width
13763 (@value{GDBP}) set width=47
13764 Invalid syntax in expression.
13768 The invalid expression, of course, is @samp{=47}. In
13769 order to actually set the program's variable @code{width}, use
13772 (@value{GDBP}) set var width=47
13775 Because the @code{set} command has many subcommands that can conflict
13776 with the names of program variables, it is a good idea to use the
13777 @code{set variable} command instead of just @code{set}. For example, if
13778 your program has a variable @code{g}, you run into problems if you try
13779 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13780 the command @code{set gnutarget}, abbreviated @code{set g}:
13784 (@value{GDBP}) whatis g
13788 (@value{GDBP}) set g=4
13792 The program being debugged has been started already.
13793 Start it from the beginning? (y or n) y
13794 Starting program: /home/smith/cc_progs/a.out
13795 "/home/smith/cc_progs/a.out": can't open to read symbols:
13796 Invalid bfd target.
13797 (@value{GDBP}) show g
13798 The current BFD target is "=4".
13803 The program variable @code{g} did not change, and you silently set the
13804 @code{gnutarget} to an invalid value. In order to set the variable
13808 (@value{GDBP}) set var g=4
13811 @value{GDBN} allows more implicit conversions in assignments than C; you can
13812 freely store an integer value into a pointer variable or vice versa,
13813 and you can convert any structure to any other structure that is the
13814 same length or shorter.
13815 @comment FIXME: how do structs align/pad in these conversions?
13816 @comment /doc@cygnus.com 18dec1990
13818 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13819 construct to generate a value of specified type at a specified address
13820 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13821 to memory location @code{0x83040} as an integer (which implies a certain size
13822 and representation in memory), and
13825 set @{int@}0x83040 = 4
13829 stores the value 4 into that memory location.
13832 @section Continuing at a Different Address
13834 Ordinarily, when you continue your program, you do so at the place where
13835 it stopped, with the @code{continue} command. You can instead continue at
13836 an address of your own choosing, with the following commands:
13840 @item jump @var{linespec}
13841 @itemx jump @var{location}
13842 Resume execution at line @var{linespec} or at address given by
13843 @var{location}. Execution stops again immediately if there is a
13844 breakpoint there. @xref{Specify Location}, for a description of the
13845 different forms of @var{linespec} and @var{location}. It is common
13846 practice to use the @code{tbreak} command in conjunction with
13847 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13849 The @code{jump} command does not change the current stack frame, or
13850 the stack pointer, or the contents of any memory location or any
13851 register other than the program counter. If line @var{linespec} is in
13852 a different function from the one currently executing, the results may
13853 be bizarre if the two functions expect different patterns of arguments or
13854 of local variables. For this reason, the @code{jump} command requests
13855 confirmation if the specified line is not in the function currently
13856 executing. However, even bizarre results are predictable if you are
13857 well acquainted with the machine-language code of your program.
13860 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13861 On many systems, you can get much the same effect as the @code{jump}
13862 command by storing a new value into the register @code{$pc}. The
13863 difference is that this does not start your program running; it only
13864 changes the address of where it @emph{will} run when you continue. For
13872 makes the next @code{continue} command or stepping command execute at
13873 address @code{0x485}, rather than at the address where your program stopped.
13874 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13876 The most common occasion to use the @code{jump} command is to back
13877 up---perhaps with more breakpoints set---over a portion of a program
13878 that has already executed, in order to examine its execution in more
13883 @section Giving your Program a Signal
13884 @cindex deliver a signal to a program
13888 @item signal @var{signal}
13889 Resume execution where your program stopped, but immediately give it the
13890 signal @var{signal}. @var{signal} can be the name or the number of a
13891 signal. For example, on many systems @code{signal 2} and @code{signal
13892 SIGINT} are both ways of sending an interrupt signal.
13894 Alternatively, if @var{signal} is zero, continue execution without
13895 giving a signal. This is useful when your program stopped on account of
13896 a signal and would ordinary see the signal when resumed with the
13897 @code{continue} command; @samp{signal 0} causes it to resume without a
13900 @code{signal} does not repeat when you press @key{RET} a second time
13901 after executing the command.
13905 Invoking the @code{signal} command is not the same as invoking the
13906 @code{kill} utility from the shell. Sending a signal with @code{kill}
13907 causes @value{GDBN} to decide what to do with the signal depending on
13908 the signal handling tables (@pxref{Signals}). The @code{signal} command
13909 passes the signal directly to your program.
13913 @section Returning from a Function
13916 @cindex returning from a function
13919 @itemx return @var{expression}
13920 You can cancel execution of a function call with the @code{return}
13921 command. If you give an
13922 @var{expression} argument, its value is used as the function's return
13926 When you use @code{return}, @value{GDBN} discards the selected stack frame
13927 (and all frames within it). You can think of this as making the
13928 discarded frame return prematurely. If you wish to specify a value to
13929 be returned, give that value as the argument to @code{return}.
13931 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13932 Frame}), and any other frames inside of it, leaving its caller as the
13933 innermost remaining frame. That frame becomes selected. The
13934 specified value is stored in the registers used for returning values
13937 The @code{return} command does not resume execution; it leaves the
13938 program stopped in the state that would exist if the function had just
13939 returned. In contrast, the @code{finish} command (@pxref{Continuing
13940 and Stepping, ,Continuing and Stepping}) resumes execution until the
13941 selected stack frame returns naturally.
13943 @value{GDBN} needs to know how the @var{expression} argument should be set for
13944 the inferior. The concrete registers assignment depends on the OS ABI and the
13945 type being returned by the selected stack frame. For example it is common for
13946 OS ABI to return floating point values in FPU registers while integer values in
13947 CPU registers. Still some ABIs return even floating point values in CPU
13948 registers. Larger integer widths (such as @code{long long int}) also have
13949 specific placement rules. @value{GDBN} already knows the OS ABI from its
13950 current target so it needs to find out also the type being returned to make the
13951 assignment into the right register(s).
13953 Normally, the selected stack frame has debug info. @value{GDBN} will always
13954 use the debug info instead of the implicit type of @var{expression} when the
13955 debug info is available. For example, if you type @kbd{return -1}, and the
13956 function in the current stack frame is declared to return a @code{long long
13957 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13958 into a @code{long long int}:
13961 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13963 (@value{GDBP}) return -1
13964 Make func return now? (y or n) y
13965 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13966 43 printf ("result=%lld\n", func ());
13970 However, if the selected stack frame does not have a debug info, e.g., if the
13971 function was compiled without debug info, @value{GDBN} has to find out the type
13972 to return from user. Specifying a different type by mistake may set the value
13973 in different inferior registers than the caller code expects. For example,
13974 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13975 of a @code{long long int} result for a debug info less function (on 32-bit
13976 architectures). Therefore the user is required to specify the return type by
13977 an appropriate cast explicitly:
13980 Breakpoint 2, 0x0040050b in func ()
13981 (@value{GDBP}) return -1
13982 Return value type not available for selected stack frame.
13983 Please use an explicit cast of the value to return.
13984 (@value{GDBP}) return (long long int) -1
13985 Make selected stack frame return now? (y or n) y
13986 #0 0x00400526 in main ()
13991 @section Calling Program Functions
13994 @cindex calling functions
13995 @cindex inferior functions, calling
13996 @item print @var{expr}
13997 Evaluate the expression @var{expr} and display the resulting value.
13998 @var{expr} may include calls to functions in the program being
14002 @item call @var{expr}
14003 Evaluate the expression @var{expr} without displaying @code{void}
14006 You can use this variant of the @code{print} command if you want to
14007 execute a function from your program that does not return anything
14008 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14009 with @code{void} returned values that @value{GDBN} will otherwise
14010 print. If the result is not void, it is printed and saved in the
14014 It is possible for the function you call via the @code{print} or
14015 @code{call} command to generate a signal (e.g., if there's a bug in
14016 the function, or if you passed it incorrect arguments). What happens
14017 in that case is controlled by the @code{set unwindonsignal} command.
14019 Similarly, with a C@t{++} program it is possible for the function you
14020 call via the @code{print} or @code{call} command to generate an
14021 exception that is not handled due to the constraints of the dummy
14022 frame. In this case, any exception that is raised in the frame, but has
14023 an out-of-frame exception handler will not be found. GDB builds a
14024 dummy-frame for the inferior function call, and the unwinder cannot
14025 seek for exception handlers outside of this dummy-frame. What happens
14026 in that case is controlled by the
14027 @code{set unwind-on-terminating-exception} command.
14030 @item set unwindonsignal
14031 @kindex set unwindonsignal
14032 @cindex unwind stack in called functions
14033 @cindex call dummy stack unwinding
14034 Set unwinding of the stack if a signal is received while in a function
14035 that @value{GDBN} called in the program being debugged. If set to on,
14036 @value{GDBN} unwinds the stack it created for the call and restores
14037 the context to what it was before the call. If set to off (the
14038 default), @value{GDBN} stops in the frame where the signal was
14041 @item show unwindonsignal
14042 @kindex show unwindonsignal
14043 Show the current setting of stack unwinding in the functions called by
14046 @item set unwind-on-terminating-exception
14047 @kindex set unwind-on-terminating-exception
14048 @cindex unwind stack in called functions with unhandled exceptions
14049 @cindex call dummy stack unwinding on unhandled exception.
14050 Set unwinding of the stack if a C@t{++} exception is raised, but left
14051 unhandled while in a function that @value{GDBN} called in the program being
14052 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14053 it created for the call and restores the context to what it was before
14054 the call. If set to off, @value{GDBN} the exception is delivered to
14055 the default C@t{++} exception handler and the inferior terminated.
14057 @item show unwind-on-terminating-exception
14058 @kindex show unwind-on-terminating-exception
14059 Show the current setting of stack unwinding in the functions called by
14064 @cindex weak alias functions
14065 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14066 for another function. In such case, @value{GDBN} might not pick up
14067 the type information, including the types of the function arguments,
14068 which causes @value{GDBN} to call the inferior function incorrectly.
14069 As a result, the called function will function erroneously and may
14070 even crash. A solution to that is to use the name of the aliased
14074 @section Patching Programs
14076 @cindex patching binaries
14077 @cindex writing into executables
14078 @cindex writing into corefiles
14080 By default, @value{GDBN} opens the file containing your program's
14081 executable code (or the corefile) read-only. This prevents accidental
14082 alterations to machine code; but it also prevents you from intentionally
14083 patching your program's binary.
14085 If you'd like to be able to patch the binary, you can specify that
14086 explicitly with the @code{set write} command. For example, you might
14087 want to turn on internal debugging flags, or even to make emergency
14093 @itemx set write off
14094 If you specify @samp{set write on}, @value{GDBN} opens executable and
14095 core files for both reading and writing; if you specify @kbd{set write
14096 off} (the default), @value{GDBN} opens them read-only.
14098 If you have already loaded a file, you must load it again (using the
14099 @code{exec-file} or @code{core-file} command) after changing @code{set
14100 write}, for your new setting to take effect.
14104 Display whether executable files and core files are opened for writing
14105 as well as reading.
14109 @chapter @value{GDBN} Files
14111 @value{GDBN} needs to know the file name of the program to be debugged,
14112 both in order to read its symbol table and in order to start your
14113 program. To debug a core dump of a previous run, you must also tell
14114 @value{GDBN} the name of the core dump file.
14117 * Files:: Commands to specify files
14118 * Separate Debug Files:: Debugging information in separate files
14119 * Symbol Errors:: Errors reading symbol files
14120 * Data Files:: GDB data files
14124 @section Commands to Specify Files
14126 @cindex symbol table
14127 @cindex core dump file
14129 You may want to specify executable and core dump file names. The usual
14130 way to do this is at start-up time, using the arguments to
14131 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14132 Out of @value{GDBN}}).
14134 Occasionally it is necessary to change to a different file during a
14135 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14136 specify a file you want to use. Or you are debugging a remote target
14137 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14138 Program}). In these situations the @value{GDBN} commands to specify
14139 new files are useful.
14142 @cindex executable file
14144 @item file @var{filename}
14145 Use @var{filename} as the program to be debugged. It is read for its
14146 symbols and for the contents of pure memory. It is also the program
14147 executed when you use the @code{run} command. If you do not specify a
14148 directory and the file is not found in the @value{GDBN} working directory,
14149 @value{GDBN} uses the environment variable @code{PATH} as a list of
14150 directories to search, just as the shell does when looking for a program
14151 to run. You can change the value of this variable, for both @value{GDBN}
14152 and your program, using the @code{path} command.
14154 @cindex unlinked object files
14155 @cindex patching object files
14156 You can load unlinked object @file{.o} files into @value{GDBN} using
14157 the @code{file} command. You will not be able to ``run'' an object
14158 file, but you can disassemble functions and inspect variables. Also,
14159 if the underlying BFD functionality supports it, you could use
14160 @kbd{gdb -write} to patch object files using this technique. Note
14161 that @value{GDBN} can neither interpret nor modify relocations in this
14162 case, so branches and some initialized variables will appear to go to
14163 the wrong place. But this feature is still handy from time to time.
14166 @code{file} with no argument makes @value{GDBN} discard any information it
14167 has on both executable file and the symbol table.
14170 @item exec-file @r{[} @var{filename} @r{]}
14171 Specify that the program to be run (but not the symbol table) is found
14172 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14173 if necessary to locate your program. Omitting @var{filename} means to
14174 discard information on the executable file.
14176 @kindex symbol-file
14177 @item symbol-file @r{[} @var{filename} @r{]}
14178 Read symbol table information from file @var{filename}. @code{PATH} is
14179 searched when necessary. Use the @code{file} command to get both symbol
14180 table and program to run from the same file.
14182 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14183 program's symbol table.
14185 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14186 some breakpoints and auto-display expressions. This is because they may
14187 contain pointers to the internal data recording symbols and data types,
14188 which are part of the old symbol table data being discarded inside
14191 @code{symbol-file} does not repeat if you press @key{RET} again after
14194 When @value{GDBN} is configured for a particular environment, it
14195 understands debugging information in whatever format is the standard
14196 generated for that environment; you may use either a @sc{gnu} compiler, or
14197 other compilers that adhere to the local conventions.
14198 Best results are usually obtained from @sc{gnu} compilers; for example,
14199 using @code{@value{NGCC}} you can generate debugging information for
14202 For most kinds of object files, with the exception of old SVR3 systems
14203 using COFF, the @code{symbol-file} command does not normally read the
14204 symbol table in full right away. Instead, it scans the symbol table
14205 quickly to find which source files and which symbols are present. The
14206 details are read later, one source file at a time, as they are needed.
14208 The purpose of this two-stage reading strategy is to make @value{GDBN}
14209 start up faster. For the most part, it is invisible except for
14210 occasional pauses while the symbol table details for a particular source
14211 file are being read. (The @code{set verbose} command can turn these
14212 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14213 Warnings and Messages}.)
14215 We have not implemented the two-stage strategy for COFF yet. When the
14216 symbol table is stored in COFF format, @code{symbol-file} reads the
14217 symbol table data in full right away. Note that ``stabs-in-COFF''
14218 still does the two-stage strategy, since the debug info is actually
14222 @cindex reading symbols immediately
14223 @cindex symbols, reading immediately
14224 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14225 @itemx file @r{[} -readnow @r{]} @var{filename}
14226 You can override the @value{GDBN} two-stage strategy for reading symbol
14227 tables by using the @samp{-readnow} option with any of the commands that
14228 load symbol table information, if you want to be sure @value{GDBN} has the
14229 entire symbol table available.
14231 @c FIXME: for now no mention of directories, since this seems to be in
14232 @c flux. 13mar1992 status is that in theory GDB would look either in
14233 @c current dir or in same dir as myprog; but issues like competing
14234 @c GDB's, or clutter in system dirs, mean that in practice right now
14235 @c only current dir is used. FFish says maybe a special GDB hierarchy
14236 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14240 @item core-file @r{[}@var{filename}@r{]}
14242 Specify the whereabouts of a core dump file to be used as the ``contents
14243 of memory''. Traditionally, core files contain only some parts of the
14244 address space of the process that generated them; @value{GDBN} can access the
14245 executable file itself for other parts.
14247 @code{core-file} with no argument specifies that no core file is
14250 Note that the core file is ignored when your program is actually running
14251 under @value{GDBN}. So, if you have been running your program and you
14252 wish to debug a core file instead, you must kill the subprocess in which
14253 the program is running. To do this, use the @code{kill} command
14254 (@pxref{Kill Process, ,Killing the Child Process}).
14256 @kindex add-symbol-file
14257 @cindex dynamic linking
14258 @item add-symbol-file @var{filename} @var{address}
14259 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14260 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14261 The @code{add-symbol-file} command reads additional symbol table
14262 information from the file @var{filename}. You would use this command
14263 when @var{filename} has been dynamically loaded (by some other means)
14264 into the program that is running. @var{address} should be the memory
14265 address at which the file has been loaded; @value{GDBN} cannot figure
14266 this out for itself. You can additionally specify an arbitrary number
14267 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14268 section name and base address for that section. You can specify any
14269 @var{address} as an expression.
14271 The symbol table of the file @var{filename} is added to the symbol table
14272 originally read with the @code{symbol-file} command. You can use the
14273 @code{add-symbol-file} command any number of times; the new symbol data
14274 thus read keeps adding to the old. To discard all old symbol data
14275 instead, use the @code{symbol-file} command without any arguments.
14277 @cindex relocatable object files, reading symbols from
14278 @cindex object files, relocatable, reading symbols from
14279 @cindex reading symbols from relocatable object files
14280 @cindex symbols, reading from relocatable object files
14281 @cindex @file{.o} files, reading symbols from
14282 Although @var{filename} is typically a shared library file, an
14283 executable file, or some other object file which has been fully
14284 relocated for loading into a process, you can also load symbolic
14285 information from relocatable @file{.o} files, as long as:
14289 the file's symbolic information refers only to linker symbols defined in
14290 that file, not to symbols defined by other object files,
14292 every section the file's symbolic information refers to has actually
14293 been loaded into the inferior, as it appears in the file, and
14295 you can determine the address at which every section was loaded, and
14296 provide these to the @code{add-symbol-file} command.
14300 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14301 relocatable files into an already running program; such systems
14302 typically make the requirements above easy to meet. However, it's
14303 important to recognize that many native systems use complex link
14304 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14305 assembly, for example) that make the requirements difficult to meet. In
14306 general, one cannot assume that using @code{add-symbol-file} to read a
14307 relocatable object file's symbolic information will have the same effect
14308 as linking the relocatable object file into the program in the normal
14311 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14313 @kindex add-symbol-file-from-memory
14314 @cindex @code{syscall DSO}
14315 @cindex load symbols from memory
14316 @item add-symbol-file-from-memory @var{address}
14317 Load symbols from the given @var{address} in a dynamically loaded
14318 object file whose image is mapped directly into the inferior's memory.
14319 For example, the Linux kernel maps a @code{syscall DSO} into each
14320 process's address space; this DSO provides kernel-specific code for
14321 some system calls. The argument can be any expression whose
14322 evaluation yields the address of the file's shared object file header.
14323 For this command to work, you must have used @code{symbol-file} or
14324 @code{exec-file} commands in advance.
14326 @kindex add-shared-symbol-files
14328 @item add-shared-symbol-files @var{library-file}
14329 @itemx assf @var{library-file}
14330 The @code{add-shared-symbol-files} command can currently be used only
14331 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14332 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14333 @value{GDBN} automatically looks for shared libraries, however if
14334 @value{GDBN} does not find yours, you can invoke
14335 @code{add-shared-symbol-files}. It takes one argument: the shared
14336 library's file name. @code{assf} is a shorthand alias for
14337 @code{add-shared-symbol-files}.
14340 @item section @var{section} @var{addr}
14341 The @code{section} command changes the base address of the named
14342 @var{section} of the exec file to @var{addr}. This can be used if the
14343 exec file does not contain section addresses, (such as in the
14344 @code{a.out} format), or when the addresses specified in the file
14345 itself are wrong. Each section must be changed separately. The
14346 @code{info files} command, described below, lists all the sections and
14350 @kindex info target
14353 @code{info files} and @code{info target} are synonymous; both print the
14354 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14355 including the names of the executable and core dump files currently in
14356 use by @value{GDBN}, and the files from which symbols were loaded. The
14357 command @code{help target} lists all possible targets rather than
14360 @kindex maint info sections
14361 @item maint info sections
14362 Another command that can give you extra information about program sections
14363 is @code{maint info sections}. In addition to the section information
14364 displayed by @code{info files}, this command displays the flags and file
14365 offset of each section in the executable and core dump files. In addition,
14366 @code{maint info sections} provides the following command options (which
14367 may be arbitrarily combined):
14371 Display sections for all loaded object files, including shared libraries.
14372 @item @var{sections}
14373 Display info only for named @var{sections}.
14374 @item @var{section-flags}
14375 Display info only for sections for which @var{section-flags} are true.
14376 The section flags that @value{GDBN} currently knows about are:
14379 Section will have space allocated in the process when loaded.
14380 Set for all sections except those containing debug information.
14382 Section will be loaded from the file into the child process memory.
14383 Set for pre-initialized code and data, clear for @code{.bss} sections.
14385 Section needs to be relocated before loading.
14387 Section cannot be modified by the child process.
14389 Section contains executable code only.
14391 Section contains data only (no executable code).
14393 Section will reside in ROM.
14395 Section contains data for constructor/destructor lists.
14397 Section is not empty.
14399 An instruction to the linker to not output the section.
14400 @item COFF_SHARED_LIBRARY
14401 A notification to the linker that the section contains
14402 COFF shared library information.
14404 Section contains common symbols.
14407 @kindex set trust-readonly-sections
14408 @cindex read-only sections
14409 @item set trust-readonly-sections on
14410 Tell @value{GDBN} that readonly sections in your object file
14411 really are read-only (i.e.@: that their contents will not change).
14412 In that case, @value{GDBN} can fetch values from these sections
14413 out of the object file, rather than from the target program.
14414 For some targets (notably embedded ones), this can be a significant
14415 enhancement to debugging performance.
14417 The default is off.
14419 @item set trust-readonly-sections off
14420 Tell @value{GDBN} not to trust readonly sections. This means that
14421 the contents of the section might change while the program is running,
14422 and must therefore be fetched from the target when needed.
14424 @item show trust-readonly-sections
14425 Show the current setting of trusting readonly sections.
14428 All file-specifying commands allow both absolute and relative file names
14429 as arguments. @value{GDBN} always converts the file name to an absolute file
14430 name and remembers it that way.
14432 @cindex shared libraries
14433 @anchor{Shared Libraries}
14434 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14435 and IBM RS/6000 AIX shared libraries.
14437 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14438 shared libraries. @xref{Expat}.
14440 @value{GDBN} automatically loads symbol definitions from shared libraries
14441 when you use the @code{run} command, or when you examine a core file.
14442 (Before you issue the @code{run} command, @value{GDBN} does not understand
14443 references to a function in a shared library, however---unless you are
14444 debugging a core file).
14446 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14447 automatically loads the symbols at the time of the @code{shl_load} call.
14449 @c FIXME: some @value{GDBN} release may permit some refs to undef
14450 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14451 @c FIXME...lib; check this from time to time when updating manual
14453 There are times, however, when you may wish to not automatically load
14454 symbol definitions from shared libraries, such as when they are
14455 particularly large or there are many of them.
14457 To control the automatic loading of shared library symbols, use the
14461 @kindex set auto-solib-add
14462 @item set auto-solib-add @var{mode}
14463 If @var{mode} is @code{on}, symbols from all shared object libraries
14464 will be loaded automatically when the inferior begins execution, you
14465 attach to an independently started inferior, or when the dynamic linker
14466 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14467 is @code{off}, symbols must be loaded manually, using the
14468 @code{sharedlibrary} command. The default value is @code{on}.
14470 @cindex memory used for symbol tables
14471 If your program uses lots of shared libraries with debug info that
14472 takes large amounts of memory, you can decrease the @value{GDBN}
14473 memory footprint by preventing it from automatically loading the
14474 symbols from shared libraries. To that end, type @kbd{set
14475 auto-solib-add off} before running the inferior, then load each
14476 library whose debug symbols you do need with @kbd{sharedlibrary
14477 @var{regexp}}, where @var{regexp} is a regular expression that matches
14478 the libraries whose symbols you want to be loaded.
14480 @kindex show auto-solib-add
14481 @item show auto-solib-add
14482 Display the current autoloading mode.
14485 @cindex load shared library
14486 To explicitly load shared library symbols, use the @code{sharedlibrary}
14490 @kindex info sharedlibrary
14492 @item info share @var{regex}
14493 @itemx info sharedlibrary @var{regex}
14494 Print the names of the shared libraries which are currently loaded
14495 that match @var{regex}. If @var{regex} is omitted then print
14496 all shared libraries that are loaded.
14498 @kindex sharedlibrary
14500 @item sharedlibrary @var{regex}
14501 @itemx share @var{regex}
14502 Load shared object library symbols for files matching a
14503 Unix regular expression.
14504 As with files loaded automatically, it only loads shared libraries
14505 required by your program for a core file or after typing @code{run}. If
14506 @var{regex} is omitted all shared libraries required by your program are
14509 @item nosharedlibrary
14510 @kindex nosharedlibrary
14511 @cindex unload symbols from shared libraries
14512 Unload all shared object library symbols. This discards all symbols
14513 that have been loaded from all shared libraries. Symbols from shared
14514 libraries that were loaded by explicit user requests are not
14518 Sometimes you may wish that @value{GDBN} stops and gives you control
14519 when any of shared library events happen. Use the @code{set
14520 stop-on-solib-events} command for this:
14523 @item set stop-on-solib-events
14524 @kindex set stop-on-solib-events
14525 This command controls whether @value{GDBN} should give you control
14526 when the dynamic linker notifies it about some shared library event.
14527 The most common event of interest is loading or unloading of a new
14530 @item show stop-on-solib-events
14531 @kindex show stop-on-solib-events
14532 Show whether @value{GDBN} stops and gives you control when shared
14533 library events happen.
14536 Shared libraries are also supported in many cross or remote debugging
14537 configurations. @value{GDBN} needs to have access to the target's libraries;
14538 this can be accomplished either by providing copies of the libraries
14539 on the host system, or by asking @value{GDBN} to automatically retrieve the
14540 libraries from the target. If copies of the target libraries are
14541 provided, they need to be the same as the target libraries, although the
14542 copies on the target can be stripped as long as the copies on the host are
14545 @cindex where to look for shared libraries
14546 For remote debugging, you need to tell @value{GDBN} where the target
14547 libraries are, so that it can load the correct copies---otherwise, it
14548 may try to load the host's libraries. @value{GDBN} has two variables
14549 to specify the search directories for target libraries.
14552 @cindex prefix for shared library file names
14553 @cindex system root, alternate
14554 @kindex set solib-absolute-prefix
14555 @kindex set sysroot
14556 @item set sysroot @var{path}
14557 Use @var{path} as the system root for the program being debugged. Any
14558 absolute shared library paths will be prefixed with @var{path}; many
14559 runtime loaders store the absolute paths to the shared library in the
14560 target program's memory. If you use @code{set sysroot} to find shared
14561 libraries, they need to be laid out in the same way that they are on
14562 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14565 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14566 retrieve the target libraries from the remote system. This is only
14567 supported when using a remote target that supports the @code{remote get}
14568 command (@pxref{File Transfer,,Sending files to a remote system}).
14569 The part of @var{path} following the initial @file{remote:}
14570 (if present) is used as system root prefix on the remote file system.
14571 @footnote{If you want to specify a local system root using a directory
14572 that happens to be named @file{remote:}, you need to use some equivalent
14573 variant of the name like @file{./remote:}.}
14575 For targets with an MS-DOS based filesystem, such as MS-Windows and
14576 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14577 absolute file name with @var{path}. But first, on Unix hosts,
14578 @value{GDBN} converts all backslash directory separators into forward
14579 slashes, because the backslash is not a directory separator on Unix:
14582 c:\foo\bar.dll @result{} c:/foo/bar.dll
14585 Then, @value{GDBN} attempts prefixing the target file name with
14586 @var{path}, and looks for the resulting file name in the host file
14590 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14593 If that does not find the shared library, @value{GDBN} tries removing
14594 the @samp{:} character from the drive spec, both for convenience, and,
14595 for the case of the host file system not supporting file names with
14599 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14602 This makes it possible to have a system root that mirrors a target
14603 with more than one drive. E.g., you may want to setup your local
14604 copies of the target system shared libraries like so (note @samp{c} vs
14608 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14609 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14610 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14614 and point the system root at @file{/path/to/sysroot}, so that
14615 @value{GDBN} can find the correct copies of both
14616 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14618 If that still does not find the shared library, @value{GDBN} tries
14619 removing the whole drive spec from the target file name:
14622 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14625 This last lookup makes it possible to not care about the drive name,
14626 if you don't want or need to.
14628 The @code{set solib-absolute-prefix} command is an alias for @code{set
14631 @cindex default system root
14632 @cindex @samp{--with-sysroot}
14633 You can set the default system root by using the configure-time
14634 @samp{--with-sysroot} option. If the system root is inside
14635 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14636 @samp{--exec-prefix}), then the default system root will be updated
14637 automatically if the installed @value{GDBN} is moved to a new
14640 @kindex show sysroot
14642 Display the current shared library prefix.
14644 @kindex set solib-search-path
14645 @item set solib-search-path @var{path}
14646 If this variable is set, @var{path} is a colon-separated list of
14647 directories to search for shared libraries. @samp{solib-search-path}
14648 is used after @samp{sysroot} fails to locate the library, or if the
14649 path to the library is relative instead of absolute. If you want to
14650 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14651 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14652 finding your host's libraries. @samp{sysroot} is preferred; setting
14653 it to a nonexistent directory may interfere with automatic loading
14654 of shared library symbols.
14656 @kindex show solib-search-path
14657 @item show solib-search-path
14658 Display the current shared library search path.
14660 @cindex DOS file-name semantics of file names.
14661 @kindex set target-file-system-kind (unix|dos-based|auto)
14662 @kindex show target-file-system-kind
14663 @item set target-file-system-kind @var{kind}
14664 Set assumed file system kind for target reported file names.
14666 Shared library file names as reported by the target system may not
14667 make sense as is on the system @value{GDBN} is running on. For
14668 example, when remote debugging a target that has MS-DOS based file
14669 system semantics, from a Unix host, the target may be reporting to
14670 @value{GDBN} a list of loaded shared libraries with file names such as
14671 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14672 drive letters, so the @samp{c:\} prefix is not normally understood as
14673 indicating an absolute file name, and neither is the backslash
14674 normally considered a directory separator character. In that case,
14675 the native file system would interpret this whole absolute file name
14676 as a relative file name with no directory components. This would make
14677 it impossible to point @value{GDBN} at a copy of the remote target's
14678 shared libraries on the host using @code{set sysroot}, and impractical
14679 with @code{set solib-search-path}. Setting
14680 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14681 to interpret such file names similarly to how the target would, and to
14682 map them to file names valid on @value{GDBN}'s native file system
14683 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14684 to one of the supported file system kinds. In that case, @value{GDBN}
14685 tries to determine the appropriate file system variant based on the
14686 current target's operating system (@pxref{ABI, ,Configuring the
14687 Current ABI}). The supported file system settings are:
14691 Instruct @value{GDBN} to assume the target file system is of Unix
14692 kind. Only file names starting the forward slash (@samp{/}) character
14693 are considered absolute, and the directory separator character is also
14697 Instruct @value{GDBN} to assume the target file system is DOS based.
14698 File names starting with either a forward slash, or a drive letter
14699 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14700 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14701 considered directory separators.
14704 Instruct @value{GDBN} to use the file system kind associated with the
14705 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14706 This is the default.
14711 @node Separate Debug Files
14712 @section Debugging Information in Separate Files
14713 @cindex separate debugging information files
14714 @cindex debugging information in separate files
14715 @cindex @file{.debug} subdirectories
14716 @cindex debugging information directory, global
14717 @cindex global debugging information directory
14718 @cindex build ID, and separate debugging files
14719 @cindex @file{.build-id} directory
14721 @value{GDBN} allows you to put a program's debugging information in a
14722 file separate from the executable itself, in a way that allows
14723 @value{GDBN} to find and load the debugging information automatically.
14724 Since debugging information can be very large---sometimes larger
14725 than the executable code itself---some systems distribute debugging
14726 information for their executables in separate files, which users can
14727 install only when they need to debug a problem.
14729 @value{GDBN} supports two ways of specifying the separate debug info
14734 The executable contains a @dfn{debug link} that specifies the name of
14735 the separate debug info file. The separate debug file's name is
14736 usually @file{@var{executable}.debug}, where @var{executable} is the
14737 name of the corresponding executable file without leading directories
14738 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14739 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14740 checksum for the debug file, which @value{GDBN} uses to validate that
14741 the executable and the debug file came from the same build.
14744 The executable contains a @dfn{build ID}, a unique bit string that is
14745 also present in the corresponding debug info file. (This is supported
14746 only on some operating systems, notably those which use the ELF format
14747 for binary files and the @sc{gnu} Binutils.) For more details about
14748 this feature, see the description of the @option{--build-id}
14749 command-line option in @ref{Options, , Command Line Options, ld.info,
14750 The GNU Linker}. The debug info file's name is not specified
14751 explicitly by the build ID, but can be computed from the build ID, see
14755 Depending on the way the debug info file is specified, @value{GDBN}
14756 uses two different methods of looking for the debug file:
14760 For the ``debug link'' method, @value{GDBN} looks up the named file in
14761 the directory of the executable file, then in a subdirectory of that
14762 directory named @file{.debug}, and finally under the global debug
14763 directory, in a subdirectory whose name is identical to the leading
14764 directories of the executable's absolute file name.
14767 For the ``build ID'' method, @value{GDBN} looks in the
14768 @file{.build-id} subdirectory of the global debug directory for a file
14769 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14770 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14771 are the rest of the bit string. (Real build ID strings are 32 or more
14772 hex characters, not 10.)
14775 So, for example, suppose you ask @value{GDBN} to debug
14776 @file{/usr/bin/ls}, which has a debug link that specifies the
14777 file @file{ls.debug}, and a build ID whose value in hex is
14778 @code{abcdef1234}. If the global debug directory is
14779 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14780 debug information files, in the indicated order:
14784 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14786 @file{/usr/bin/ls.debug}
14788 @file{/usr/bin/.debug/ls.debug}
14790 @file{/usr/lib/debug/usr/bin/ls.debug}.
14793 You can set the global debugging info directory's name, and view the
14794 name @value{GDBN} is currently using.
14798 @kindex set debug-file-directory
14799 @item set debug-file-directory @var{directories}
14800 Set the directories which @value{GDBN} searches for separate debugging
14801 information files to @var{directory}. Multiple directory components can be set
14802 concatenating them by a directory separator.
14804 @kindex show debug-file-directory
14805 @item show debug-file-directory
14806 Show the directories @value{GDBN} searches for separate debugging
14811 @cindex @code{.gnu_debuglink} sections
14812 @cindex debug link sections
14813 A debug link is a special section of the executable file named
14814 @code{.gnu_debuglink}. The section must contain:
14818 A filename, with any leading directory components removed, followed by
14821 zero to three bytes of padding, as needed to reach the next four-byte
14822 boundary within the section, and
14824 a four-byte CRC checksum, stored in the same endianness used for the
14825 executable file itself. The checksum is computed on the debugging
14826 information file's full contents by the function given below, passing
14827 zero as the @var{crc} argument.
14830 Any executable file format can carry a debug link, as long as it can
14831 contain a section named @code{.gnu_debuglink} with the contents
14834 @cindex @code{.note.gnu.build-id} sections
14835 @cindex build ID sections
14836 The build ID is a special section in the executable file (and in other
14837 ELF binary files that @value{GDBN} may consider). This section is
14838 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14839 It contains unique identification for the built files---the ID remains
14840 the same across multiple builds of the same build tree. The default
14841 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14842 content for the build ID string. The same section with an identical
14843 value is present in the original built binary with symbols, in its
14844 stripped variant, and in the separate debugging information file.
14846 The debugging information file itself should be an ordinary
14847 executable, containing a full set of linker symbols, sections, and
14848 debugging information. The sections of the debugging information file
14849 should have the same names, addresses, and sizes as the original file,
14850 but they need not contain any data---much like a @code{.bss} section
14851 in an ordinary executable.
14853 The @sc{gnu} binary utilities (Binutils) package includes the
14854 @samp{objcopy} utility that can produce
14855 the separated executable / debugging information file pairs using the
14856 following commands:
14859 @kbd{objcopy --only-keep-debug foo foo.debug}
14864 These commands remove the debugging
14865 information from the executable file @file{foo} and place it in the file
14866 @file{foo.debug}. You can use the first, second or both methods to link the
14871 The debug link method needs the following additional command to also leave
14872 behind a debug link in @file{foo}:
14875 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14878 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14879 a version of the @code{strip} command such that the command @kbd{strip foo -f
14880 foo.debug} has the same functionality as the two @code{objcopy} commands and
14881 the @code{ln -s} command above, together.
14884 Build ID gets embedded into the main executable using @code{ld --build-id} or
14885 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14886 compatibility fixes for debug files separation are present in @sc{gnu} binary
14887 utilities (Binutils) package since version 2.18.
14892 @cindex CRC algorithm definition
14893 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14894 IEEE 802.3 using the polynomial:
14896 @c TexInfo requires naked braces for multi-digit exponents for Tex
14897 @c output, but this causes HTML output to barf. HTML has to be set using
14898 @c raw commands. So we end up having to specify this equation in 2
14903 <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>
14904 + <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
14910 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14911 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14915 The function is computed byte at a time, taking the least
14916 significant bit of each byte first. The initial pattern
14917 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14918 the final result is inverted to ensure trailing zeros also affect the
14921 @emph{Note:} This is the same CRC polynomial as used in handling the
14922 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14923 , @value{GDBN} Remote Serial Protocol}). However in the
14924 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14925 significant bit first, and the result is not inverted, so trailing
14926 zeros have no effect on the CRC value.
14928 To complete the description, we show below the code of the function
14929 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14930 initially supplied @code{crc} argument means that an initial call to
14931 this function passing in zero will start computing the CRC using
14934 @kindex gnu_debuglink_crc32
14937 gnu_debuglink_crc32 (unsigned long crc,
14938 unsigned char *buf, size_t len)
14940 static const unsigned long crc32_table[256] =
14942 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14943 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14944 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14945 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14946 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14947 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14948 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14949 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14950 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14951 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14952 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14953 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14954 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14955 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14956 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14957 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14958 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14959 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14960 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14961 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14962 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14963 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14964 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14965 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14966 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14967 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14968 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14969 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14970 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14971 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14972 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14973 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14974 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14975 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14976 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14977 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14978 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14979 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14980 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14981 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14982 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14983 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14984 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14985 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14986 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14987 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14988 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14989 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14990 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14991 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14992 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14995 unsigned char *end;
14997 crc = ~crc & 0xffffffff;
14998 for (end = buf + len; buf < end; ++buf)
14999 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15000 return ~crc & 0xffffffff;
15005 This computation does not apply to the ``build ID'' method.
15008 @node Symbol Errors
15009 @section Errors Reading Symbol Files
15011 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15012 such as symbol types it does not recognize, or known bugs in compiler
15013 output. By default, @value{GDBN} does not notify you of such problems, since
15014 they are relatively common and primarily of interest to people
15015 debugging compilers. If you are interested in seeing information
15016 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15017 only one message about each such type of problem, no matter how many
15018 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15019 to see how many times the problems occur, with the @code{set
15020 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15023 The messages currently printed, and their meanings, include:
15026 @item inner block not inside outer block in @var{symbol}
15028 The symbol information shows where symbol scopes begin and end
15029 (such as at the start of a function or a block of statements). This
15030 error indicates that an inner scope block is not fully contained
15031 in its outer scope blocks.
15033 @value{GDBN} circumvents the problem by treating the inner block as if it had
15034 the same scope as the outer block. In the error message, @var{symbol}
15035 may be shown as ``@code{(don't know)}'' if the outer block is not a
15038 @item block at @var{address} out of order
15040 The symbol information for symbol scope blocks should occur in
15041 order of increasing addresses. This error indicates that it does not
15044 @value{GDBN} does not circumvent this problem, and has trouble
15045 locating symbols in the source file whose symbols it is reading. (You
15046 can often determine what source file is affected by specifying
15047 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15050 @item bad block start address patched
15052 The symbol information for a symbol scope block has a start address
15053 smaller than the address of the preceding source line. This is known
15054 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15056 @value{GDBN} circumvents the problem by treating the symbol scope block as
15057 starting on the previous source line.
15059 @item bad string table offset in symbol @var{n}
15062 Symbol number @var{n} contains a pointer into the string table which is
15063 larger than the size of the string table.
15065 @value{GDBN} circumvents the problem by considering the symbol to have the
15066 name @code{foo}, which may cause other problems if many symbols end up
15069 @item unknown symbol type @code{0x@var{nn}}
15071 The symbol information contains new data types that @value{GDBN} does
15072 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15073 uncomprehended information, in hexadecimal.
15075 @value{GDBN} circumvents the error by ignoring this symbol information.
15076 This usually allows you to debug your program, though certain symbols
15077 are not accessible. If you encounter such a problem and feel like
15078 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15079 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15080 and examine @code{*bufp} to see the symbol.
15082 @item stub type has NULL name
15084 @value{GDBN} could not find the full definition for a struct or class.
15086 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15087 The symbol information for a C@t{++} member function is missing some
15088 information that recent versions of the compiler should have output for
15091 @item info mismatch between compiler and debugger
15093 @value{GDBN} could not parse a type specification output by the compiler.
15098 @section GDB Data Files
15100 @cindex prefix for data files
15101 @value{GDBN} will sometimes read an auxiliary data file. These files
15102 are kept in a directory known as the @dfn{data directory}.
15104 You can set the data directory's name, and view the name @value{GDBN}
15105 is currently using.
15108 @kindex set data-directory
15109 @item set data-directory @var{directory}
15110 Set the directory which @value{GDBN} searches for auxiliary data files
15111 to @var{directory}.
15113 @kindex show data-directory
15114 @item show data-directory
15115 Show the directory @value{GDBN} searches for auxiliary data files.
15118 @cindex default data directory
15119 @cindex @samp{--with-gdb-datadir}
15120 You can set the default data directory by using the configure-time
15121 @samp{--with-gdb-datadir} option. If the data directory is inside
15122 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15123 @samp{--exec-prefix}), then the default data directory will be updated
15124 automatically if the installed @value{GDBN} is moved to a new
15128 @chapter Specifying a Debugging Target
15130 @cindex debugging target
15131 A @dfn{target} is the execution environment occupied by your program.
15133 Often, @value{GDBN} runs in the same host environment as your program;
15134 in that case, the debugging target is specified as a side effect when
15135 you use the @code{file} or @code{core} commands. When you need more
15136 flexibility---for example, running @value{GDBN} on a physically separate
15137 host, or controlling a standalone system over a serial port or a
15138 realtime system over a TCP/IP connection---you can use the @code{target}
15139 command to specify one of the target types configured for @value{GDBN}
15140 (@pxref{Target Commands, ,Commands for Managing Targets}).
15142 @cindex target architecture
15143 It is possible to build @value{GDBN} for several different @dfn{target
15144 architectures}. When @value{GDBN} is built like that, you can choose
15145 one of the available architectures with the @kbd{set architecture}
15149 @kindex set architecture
15150 @kindex show architecture
15151 @item set architecture @var{arch}
15152 This command sets the current target architecture to @var{arch}. The
15153 value of @var{arch} can be @code{"auto"}, in addition to one of the
15154 supported architectures.
15156 @item show architecture
15157 Show the current target architecture.
15159 @item set processor
15161 @kindex set processor
15162 @kindex show processor
15163 These are alias commands for, respectively, @code{set architecture}
15164 and @code{show architecture}.
15168 * Active Targets:: Active targets
15169 * Target Commands:: Commands for managing targets
15170 * Byte Order:: Choosing target byte order
15173 @node Active Targets
15174 @section Active Targets
15176 @cindex stacking targets
15177 @cindex active targets
15178 @cindex multiple targets
15180 There are three classes of targets: processes, core files, and
15181 executable files. @value{GDBN} can work concurrently on up to three
15182 active targets, one in each class. This allows you to (for example)
15183 start a process and inspect its activity without abandoning your work on
15186 For example, if you execute @samp{gdb a.out}, then the executable file
15187 @code{a.out} is the only active target. If you designate a core file as
15188 well---presumably from a prior run that crashed and coredumped---then
15189 @value{GDBN} has two active targets and uses them in tandem, looking
15190 first in the corefile target, then in the executable file, to satisfy
15191 requests for memory addresses. (Typically, these two classes of target
15192 are complementary, since core files contain only a program's
15193 read-write memory---variables and so on---plus machine status, while
15194 executable files contain only the program text and initialized data.)
15196 When you type @code{run}, your executable file becomes an active process
15197 target as well. When a process target is active, all @value{GDBN}
15198 commands requesting memory addresses refer to that target; addresses in
15199 an active core file or executable file target are obscured while the
15200 process target is active.
15202 Use the @code{core-file} and @code{exec-file} commands to select a new
15203 core file or executable target (@pxref{Files, ,Commands to Specify
15204 Files}). To specify as a target a process that is already running, use
15205 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15208 @node Target Commands
15209 @section Commands for Managing Targets
15212 @item target @var{type} @var{parameters}
15213 Connects the @value{GDBN} host environment to a target machine or
15214 process. A target is typically a protocol for talking to debugging
15215 facilities. You use the argument @var{type} to specify the type or
15216 protocol of the target machine.
15218 Further @var{parameters} are interpreted by the target protocol, but
15219 typically include things like device names or host names to connect
15220 with, process numbers, and baud rates.
15222 The @code{target} command does not repeat if you press @key{RET} again
15223 after executing the command.
15225 @kindex help target
15227 Displays the names of all targets available. To display targets
15228 currently selected, use either @code{info target} or @code{info files}
15229 (@pxref{Files, ,Commands to Specify Files}).
15231 @item help target @var{name}
15232 Describe a particular target, including any parameters necessary to
15235 @kindex set gnutarget
15236 @item set gnutarget @var{args}
15237 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15238 knows whether it is reading an @dfn{executable},
15239 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15240 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15241 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15244 @emph{Warning:} To specify a file format with @code{set gnutarget},
15245 you must know the actual BFD name.
15249 @xref{Files, , Commands to Specify Files}.
15251 @kindex show gnutarget
15252 @item show gnutarget
15253 Use the @code{show gnutarget} command to display what file format
15254 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15255 @value{GDBN} will determine the file format for each file automatically,
15256 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15259 @cindex common targets
15260 Here are some common targets (available, or not, depending on the GDB
15265 @item target exec @var{program}
15266 @cindex executable file target
15267 An executable file. @samp{target exec @var{program}} is the same as
15268 @samp{exec-file @var{program}}.
15270 @item target core @var{filename}
15271 @cindex core dump file target
15272 A core dump file. @samp{target core @var{filename}} is the same as
15273 @samp{core-file @var{filename}}.
15275 @item target remote @var{medium}
15276 @cindex remote target
15277 A remote system connected to @value{GDBN} via a serial line or network
15278 connection. This command tells @value{GDBN} to use its own remote
15279 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15281 For example, if you have a board connected to @file{/dev/ttya} on the
15282 machine running @value{GDBN}, you could say:
15285 target remote /dev/ttya
15288 @code{target remote} supports the @code{load} command. This is only
15289 useful if you have some other way of getting the stub to the target
15290 system, and you can put it somewhere in memory where it won't get
15291 clobbered by the download.
15293 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15294 @cindex built-in simulator target
15295 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15303 works; however, you cannot assume that a specific memory map, device
15304 drivers, or even basic I/O is available, although some simulators do
15305 provide these. For info about any processor-specific simulator details,
15306 see the appropriate section in @ref{Embedded Processors, ,Embedded
15311 Some configurations may include these targets as well:
15315 @item target nrom @var{dev}
15316 @cindex NetROM ROM emulator target
15317 NetROM ROM emulator. This target only supports downloading.
15321 Different targets are available on different configurations of @value{GDBN};
15322 your configuration may have more or fewer targets.
15324 Many remote targets require you to download the executable's code once
15325 you've successfully established a connection. You may wish to control
15326 various aspects of this process.
15331 @kindex set hash@r{, for remote monitors}
15332 @cindex hash mark while downloading
15333 This command controls whether a hash mark @samp{#} is displayed while
15334 downloading a file to the remote monitor. If on, a hash mark is
15335 displayed after each S-record is successfully downloaded to the
15339 @kindex show hash@r{, for remote monitors}
15340 Show the current status of displaying the hash mark.
15342 @item set debug monitor
15343 @kindex set debug monitor
15344 @cindex display remote monitor communications
15345 Enable or disable display of communications messages between
15346 @value{GDBN} and the remote monitor.
15348 @item show debug monitor
15349 @kindex show debug monitor
15350 Show the current status of displaying communications between
15351 @value{GDBN} and the remote monitor.
15356 @kindex load @var{filename}
15357 @item load @var{filename}
15359 Depending on what remote debugging facilities are configured into
15360 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15361 is meant to make @var{filename} (an executable) available for debugging
15362 on the remote system---by downloading, or dynamic linking, for example.
15363 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15364 the @code{add-symbol-file} command.
15366 If your @value{GDBN} does not have a @code{load} command, attempting to
15367 execute it gets the error message ``@code{You can't do that when your
15368 target is @dots{}}''
15370 The file is loaded at whatever address is specified in the executable.
15371 For some object file formats, you can specify the load address when you
15372 link the program; for other formats, like a.out, the object file format
15373 specifies a fixed address.
15374 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15376 Depending on the remote side capabilities, @value{GDBN} may be able to
15377 load programs into flash memory.
15379 @code{load} does not repeat if you press @key{RET} again after using it.
15383 @section Choosing Target Byte Order
15385 @cindex choosing target byte order
15386 @cindex target byte order
15388 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15389 offer the ability to run either big-endian or little-endian byte
15390 orders. Usually the executable or symbol will include a bit to
15391 designate the endian-ness, and you will not need to worry about
15392 which to use. However, you may still find it useful to adjust
15393 @value{GDBN}'s idea of processor endian-ness manually.
15397 @item set endian big
15398 Instruct @value{GDBN} to assume the target is big-endian.
15400 @item set endian little
15401 Instruct @value{GDBN} to assume the target is little-endian.
15403 @item set endian auto
15404 Instruct @value{GDBN} to use the byte order associated with the
15408 Display @value{GDBN}'s current idea of the target byte order.
15412 Note that these commands merely adjust interpretation of symbolic
15413 data on the host, and that they have absolutely no effect on the
15417 @node Remote Debugging
15418 @chapter Debugging Remote Programs
15419 @cindex remote debugging
15421 If you are trying to debug a program running on a machine that cannot run
15422 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15423 For example, you might use remote debugging on an operating system kernel,
15424 or on a small system which does not have a general purpose operating system
15425 powerful enough to run a full-featured debugger.
15427 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15428 to make this work with particular debugging targets. In addition,
15429 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15430 but not specific to any particular target system) which you can use if you
15431 write the remote stubs---the code that runs on the remote system to
15432 communicate with @value{GDBN}.
15434 Other remote targets may be available in your
15435 configuration of @value{GDBN}; use @code{help target} to list them.
15438 * Connecting:: Connecting to a remote target
15439 * File Transfer:: Sending files to a remote system
15440 * Server:: Using the gdbserver program
15441 * Remote Configuration:: Remote configuration
15442 * Remote Stub:: Implementing a remote stub
15446 @section Connecting to a Remote Target
15448 On the @value{GDBN} host machine, you will need an unstripped copy of
15449 your program, since @value{GDBN} needs symbol and debugging information.
15450 Start up @value{GDBN} as usual, using the name of the local copy of your
15451 program as the first argument.
15453 @cindex @code{target remote}
15454 @value{GDBN} can communicate with the target over a serial line, or
15455 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15456 each case, @value{GDBN} uses the same protocol for debugging your
15457 program; only the medium carrying the debugging packets varies. The
15458 @code{target remote} command establishes a connection to the target.
15459 Its arguments indicate which medium to use:
15463 @item target remote @var{serial-device}
15464 @cindex serial line, @code{target remote}
15465 Use @var{serial-device} to communicate with the target. For example,
15466 to use a serial line connected to the device named @file{/dev/ttyb}:
15469 target remote /dev/ttyb
15472 If you're using a serial line, you may want to give @value{GDBN} the
15473 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15474 (@pxref{Remote Configuration, set remotebaud}) before the
15475 @code{target} command.
15477 @item target remote @code{@var{host}:@var{port}}
15478 @itemx target remote @code{tcp:@var{host}:@var{port}}
15479 @cindex @acronym{TCP} port, @code{target remote}
15480 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15481 The @var{host} may be either a host name or a numeric @acronym{IP}
15482 address; @var{port} must be a decimal number. The @var{host} could be
15483 the target machine itself, if it is directly connected to the net, or
15484 it might be a terminal server which in turn has a serial line to the
15487 For example, to connect to port 2828 on a terminal server named
15491 target remote manyfarms:2828
15494 If your remote target is actually running on the same machine as your
15495 debugger session (e.g.@: a simulator for your target running on the
15496 same host), you can omit the hostname. For example, to connect to
15497 port 1234 on your local machine:
15500 target remote :1234
15504 Note that the colon is still required here.
15506 @item target remote @code{udp:@var{host}:@var{port}}
15507 @cindex @acronym{UDP} port, @code{target remote}
15508 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15509 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15512 target remote udp:manyfarms:2828
15515 When using a @acronym{UDP} connection for remote debugging, you should
15516 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15517 can silently drop packets on busy or unreliable networks, which will
15518 cause havoc with your debugging session.
15520 @item target remote | @var{command}
15521 @cindex pipe, @code{target remote} to
15522 Run @var{command} in the background and communicate with it using a
15523 pipe. The @var{command} is a shell command, to be parsed and expanded
15524 by the system's command shell, @code{/bin/sh}; it should expect remote
15525 protocol packets on its standard input, and send replies on its
15526 standard output. You could use this to run a stand-alone simulator
15527 that speaks the remote debugging protocol, to make net connections
15528 using programs like @code{ssh}, or for other similar tricks.
15530 If @var{command} closes its standard output (perhaps by exiting),
15531 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15532 program has already exited, this will have no effect.)
15536 Once the connection has been established, you can use all the usual
15537 commands to examine and change data. The remote program is already
15538 running; you can use @kbd{step} and @kbd{continue}, and you do not
15539 need to use @kbd{run}.
15541 @cindex interrupting remote programs
15542 @cindex remote programs, interrupting
15543 Whenever @value{GDBN} is waiting for the remote program, if you type the
15544 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15545 program. This may or may not succeed, depending in part on the hardware
15546 and the serial drivers the remote system uses. If you type the
15547 interrupt character once again, @value{GDBN} displays this prompt:
15550 Interrupted while waiting for the program.
15551 Give up (and stop debugging it)? (y or n)
15554 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15555 (If you decide you want to try again later, you can use @samp{target
15556 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15557 goes back to waiting.
15560 @kindex detach (remote)
15562 When you have finished debugging the remote program, you can use the
15563 @code{detach} command to release it from @value{GDBN} control.
15564 Detaching from the target normally resumes its execution, but the results
15565 will depend on your particular remote stub. After the @code{detach}
15566 command, @value{GDBN} is free to connect to another target.
15570 The @code{disconnect} command behaves like @code{detach}, except that
15571 the target is generally not resumed. It will wait for @value{GDBN}
15572 (this instance or another one) to connect and continue debugging. After
15573 the @code{disconnect} command, @value{GDBN} is again free to connect to
15576 @cindex send command to remote monitor
15577 @cindex extend @value{GDBN} for remote targets
15578 @cindex add new commands for external monitor
15580 @item monitor @var{cmd}
15581 This command allows you to send arbitrary commands directly to the
15582 remote monitor. Since @value{GDBN} doesn't care about the commands it
15583 sends like this, this command is the way to extend @value{GDBN}---you
15584 can add new commands that only the external monitor will understand
15588 @node File Transfer
15589 @section Sending files to a remote system
15590 @cindex remote target, file transfer
15591 @cindex file transfer
15592 @cindex sending files to remote systems
15594 Some remote targets offer the ability to transfer files over the same
15595 connection used to communicate with @value{GDBN}. This is convenient
15596 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15597 running @code{gdbserver} over a network interface. For other targets,
15598 e.g.@: embedded devices with only a single serial port, this may be
15599 the only way to upload or download files.
15601 Not all remote targets support these commands.
15605 @item remote put @var{hostfile} @var{targetfile}
15606 Copy file @var{hostfile} from the host system (the machine running
15607 @value{GDBN}) to @var{targetfile} on the target system.
15610 @item remote get @var{targetfile} @var{hostfile}
15611 Copy file @var{targetfile} from the target system to @var{hostfile}
15612 on the host system.
15614 @kindex remote delete
15615 @item remote delete @var{targetfile}
15616 Delete @var{targetfile} from the target system.
15621 @section Using the @code{gdbserver} Program
15624 @cindex remote connection without stubs
15625 @code{gdbserver} is a control program for Unix-like systems, which
15626 allows you to connect your program with a remote @value{GDBN} via
15627 @code{target remote}---but without linking in the usual debugging stub.
15629 @code{gdbserver} is not a complete replacement for the debugging stubs,
15630 because it requires essentially the same operating-system facilities
15631 that @value{GDBN} itself does. In fact, a system that can run
15632 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15633 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15634 because it is a much smaller program than @value{GDBN} itself. It is
15635 also easier to port than all of @value{GDBN}, so you may be able to get
15636 started more quickly on a new system by using @code{gdbserver}.
15637 Finally, if you develop code for real-time systems, you may find that
15638 the tradeoffs involved in real-time operation make it more convenient to
15639 do as much development work as possible on another system, for example
15640 by cross-compiling. You can use @code{gdbserver} to make a similar
15641 choice for debugging.
15643 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15644 or a TCP connection, using the standard @value{GDBN} remote serial
15648 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15649 Do not run @code{gdbserver} connected to any public network; a
15650 @value{GDBN} connection to @code{gdbserver} provides access to the
15651 target system with the same privileges as the user running
15655 @subsection Running @code{gdbserver}
15656 @cindex arguments, to @code{gdbserver}
15658 Run @code{gdbserver} on the target system. You need a copy of the
15659 program you want to debug, including any libraries it requires.
15660 @code{gdbserver} does not need your program's symbol table, so you can
15661 strip the program if necessary to save space. @value{GDBN} on the host
15662 system does all the symbol handling.
15664 To use the server, you must tell it how to communicate with @value{GDBN};
15665 the name of your program; and the arguments for your program. The usual
15669 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15672 @var{comm} is either a device name (to use a serial line) or a TCP
15673 hostname and portnumber. For example, to debug Emacs with the argument
15674 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15678 target> gdbserver /dev/com1 emacs foo.txt
15681 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15684 To use a TCP connection instead of a serial line:
15687 target> gdbserver host:2345 emacs foo.txt
15690 The only difference from the previous example is the first argument,
15691 specifying that you are communicating with the host @value{GDBN} via
15692 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15693 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15694 (Currently, the @samp{host} part is ignored.) You can choose any number
15695 you want for the port number as long as it does not conflict with any
15696 TCP ports already in use on the target system (for example, @code{23} is
15697 reserved for @code{telnet}).@footnote{If you choose a port number that
15698 conflicts with another service, @code{gdbserver} prints an error message
15699 and exits.} You must use the same port number with the host @value{GDBN}
15700 @code{target remote} command.
15702 @subsubsection Attaching to a Running Program
15704 On some targets, @code{gdbserver} can also attach to running programs.
15705 This is accomplished via the @code{--attach} argument. The syntax is:
15708 target> gdbserver --attach @var{comm} @var{pid}
15711 @var{pid} is the process ID of a currently running process. It isn't necessary
15712 to point @code{gdbserver} at a binary for the running process.
15715 @cindex attach to a program by name
15716 You can debug processes by name instead of process ID if your target has the
15717 @code{pidof} utility:
15720 target> gdbserver --attach @var{comm} `pidof @var{program}`
15723 In case more than one copy of @var{program} is running, or @var{program}
15724 has multiple threads, most versions of @code{pidof} support the
15725 @code{-s} option to only return the first process ID.
15727 @subsubsection Multi-Process Mode for @code{gdbserver}
15728 @cindex gdbserver, multiple processes
15729 @cindex multiple processes with gdbserver
15731 When you connect to @code{gdbserver} using @code{target remote},
15732 @code{gdbserver} debugs the specified program only once. When the
15733 program exits, or you detach from it, @value{GDBN} closes the connection
15734 and @code{gdbserver} exits.
15736 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15737 enters multi-process mode. When the debugged program exits, or you
15738 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15739 though no program is running. The @code{run} and @code{attach}
15740 commands instruct @code{gdbserver} to run or attach to a new program.
15741 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15742 remote exec-file}) to select the program to run. Command line
15743 arguments are supported, except for wildcard expansion and I/O
15744 redirection (@pxref{Arguments}).
15746 To start @code{gdbserver} without supplying an initial command to run
15747 or process ID to attach, use the @option{--multi} command line option.
15748 Then you can connect using @kbd{target extended-remote} and start
15749 the program you want to debug.
15751 @code{gdbserver} does not automatically exit in multi-process mode.
15752 You can terminate it by using @code{monitor exit}
15753 (@pxref{Monitor Commands for gdbserver}).
15755 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15757 The @option{--debug} option tells @code{gdbserver} to display extra
15758 status information about the debugging process. The
15759 @option{--remote-debug} option tells @code{gdbserver} to display
15760 remote protocol debug output. These options are intended for
15761 @code{gdbserver} development and for bug reports to the developers.
15763 The @option{--wrapper} option specifies a wrapper to launch programs
15764 for debugging. The option should be followed by the name of the
15765 wrapper, then any command-line arguments to pass to the wrapper, then
15766 @kbd{--} indicating the end of the wrapper arguments.
15768 @code{gdbserver} runs the specified wrapper program with a combined
15769 command line including the wrapper arguments, then the name of the
15770 program to debug, then any arguments to the program. The wrapper
15771 runs until it executes your program, and then @value{GDBN} gains control.
15773 You can use any program that eventually calls @code{execve} with
15774 its arguments as a wrapper. Several standard Unix utilities do
15775 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15776 with @code{exec "$@@"} will also work.
15778 For example, you can use @code{env} to pass an environment variable to
15779 the debugged program, without setting the variable in @code{gdbserver}'s
15783 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15786 @subsection Connecting to @code{gdbserver}
15788 Run @value{GDBN} on the host system.
15790 First make sure you have the necessary symbol files. Load symbols for
15791 your application using the @code{file} command before you connect. Use
15792 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15793 was compiled with the correct sysroot using @code{--with-sysroot}).
15795 The symbol file and target libraries must exactly match the executable
15796 and libraries on the target, with one exception: the files on the host
15797 system should not be stripped, even if the files on the target system
15798 are. Mismatched or missing files will lead to confusing results
15799 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15800 files may also prevent @code{gdbserver} from debugging multi-threaded
15803 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15804 For TCP connections, you must start up @code{gdbserver} prior to using
15805 the @code{target remote} command. Otherwise you may get an error whose
15806 text depends on the host system, but which usually looks something like
15807 @samp{Connection refused}. Don't use the @code{load}
15808 command in @value{GDBN} when using @code{gdbserver}, since the program is
15809 already on the target.
15811 @subsection Monitor Commands for @code{gdbserver}
15812 @cindex monitor commands, for @code{gdbserver}
15813 @anchor{Monitor Commands for gdbserver}
15815 During a @value{GDBN} session using @code{gdbserver}, you can use the
15816 @code{monitor} command to send special requests to @code{gdbserver}.
15817 Here are the available commands.
15821 List the available monitor commands.
15823 @item monitor set debug 0
15824 @itemx monitor set debug 1
15825 Disable or enable general debugging messages.
15827 @item monitor set remote-debug 0
15828 @itemx monitor set remote-debug 1
15829 Disable or enable specific debugging messages associated with the remote
15830 protocol (@pxref{Remote Protocol}).
15832 @item monitor set libthread-db-search-path [PATH]
15833 @cindex gdbserver, search path for @code{libthread_db}
15834 When this command is issued, @var{path} is a colon-separated list of
15835 directories to search for @code{libthread_db} (@pxref{Threads,,set
15836 libthread-db-search-path}). If you omit @var{path},
15837 @samp{libthread-db-search-path} will be reset to an empty list.
15840 Tell gdbserver to exit immediately. This command should be followed by
15841 @code{disconnect} to close the debugging session. @code{gdbserver} will
15842 detach from any attached processes and kill any processes it created.
15843 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15844 of a multi-process mode debug session.
15848 @subsection Tracepoints support in @code{gdbserver}
15849 @cindex tracepoints support in @code{gdbserver}
15851 On some targets, @code{gdbserver} supports tracepoints and fast
15854 For fast tracepoints to work, a special library called the
15855 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
15856 This library is built and distributed as an integral part of
15859 There are several ways to load the in-process agent in your program:
15862 @item Specifying it as dependency at link time
15864 You can link your program dynamically with the in-process agent
15865 library. On most systems, this is accomplished by adding
15866 @code{-linproctrace} to the link command.
15868 @item Using the system's preloading mechanisms
15870 You can force loading the in-process agent at startup time by using
15871 your system's support for preloading shared libraries. Many Unixes
15872 support the concept of preloading user defined libraries. In most
15873 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
15874 in the environment. See also the description of @code{gdbserver}'s
15875 @option{--wrapper} command line option.
15877 @item Using @value{GDBN} to force loading the agent at run time
15879 On some systems, you can force the inferior to load a shared library,
15880 by calling a dynamic loader function in the inferior that takes care
15881 of dynamically looking up and loading a shared library. On most Unix
15882 systems, the function is @code{dlopen}. You'll use the @code{call}
15883 command for that. For example:
15886 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
15889 Note that on most Unix systems, for the @code{dlopen} function to be
15890 available, the program needs to be linked with @code{-ldl}.
15893 On systems that have a userspace dynamic loader, like most Unix
15894 systems, when you connect to @code{gdbserver} using @code{target
15895 remote}, you'll find that the program is stopped at the dynamic
15896 loader's entry point, and no shared library has been loaded in the
15897 program's address space yet, including the in-process agent. In that
15898 case, before being able to use any of the fast tracepoints features,
15899 you need to let the loader run and load the shared libraries. The
15900 most simple way to do that is to run the program to the main
15901 procedure. E.g., if debugging a C or C@t{++} program, start
15902 @code{gdbserver} like so:
15905 $ gdbserver :9999 myprogram
15908 Start GDB and connect to @code{gdbserver} like so, and run to main:
15912 (@value{GDBP}) target remote myhost:9999
15913 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
15914 (@value{GDBP}) b main
15915 (@value{GDBP}) continue
15918 The in-process tracing agent library should now be loaded into the
15919 process; you can confirm it with the @code{info sharedlibrary}
15920 command, which will list @file{libinproctrace.so} as loaded in the
15921 process. You are now ready to install fast tracepoints and start
15924 @node Remote Configuration
15925 @section Remote Configuration
15928 @kindex show remote
15929 This section documents the configuration options available when
15930 debugging remote programs. For the options related to the File I/O
15931 extensions of the remote protocol, see @ref{system,
15932 system-call-allowed}.
15935 @item set remoteaddresssize @var{bits}
15936 @cindex address size for remote targets
15937 @cindex bits in remote address
15938 Set the maximum size of address in a memory packet to the specified
15939 number of bits. @value{GDBN} will mask off the address bits above
15940 that number, when it passes addresses to the remote target. The
15941 default value is the number of bits in the target's address.
15943 @item show remoteaddresssize
15944 Show the current value of remote address size in bits.
15946 @item set remotebaud @var{n}
15947 @cindex baud rate for remote targets
15948 Set the baud rate for the remote serial I/O to @var{n} baud. The
15949 value is used to set the speed of the serial port used for debugging
15952 @item show remotebaud
15953 Show the current speed of the remote connection.
15955 @item set remotebreak
15956 @cindex interrupt remote programs
15957 @cindex BREAK signal instead of Ctrl-C
15958 @anchor{set remotebreak}
15959 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15960 when you type @kbd{Ctrl-c} to interrupt the program running
15961 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15962 character instead. The default is off, since most remote systems
15963 expect to see @samp{Ctrl-C} as the interrupt signal.
15965 @item show remotebreak
15966 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15967 interrupt the remote program.
15969 @item set remoteflow on
15970 @itemx set remoteflow off
15971 @kindex set remoteflow
15972 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15973 on the serial port used to communicate to the remote target.
15975 @item show remoteflow
15976 @kindex show remoteflow
15977 Show the current setting of hardware flow control.
15979 @item set remotelogbase @var{base}
15980 Set the base (a.k.a.@: radix) of logging serial protocol
15981 communications to @var{base}. Supported values of @var{base} are:
15982 @code{ascii}, @code{octal}, and @code{hex}. The default is
15985 @item show remotelogbase
15986 Show the current setting of the radix for logging remote serial
15989 @item set remotelogfile @var{file}
15990 @cindex record serial communications on file
15991 Record remote serial communications on the named @var{file}. The
15992 default is not to record at all.
15994 @item show remotelogfile.
15995 Show the current setting of the file name on which to record the
15996 serial communications.
15998 @item set remotetimeout @var{num}
15999 @cindex timeout for serial communications
16000 @cindex remote timeout
16001 Set the timeout limit to wait for the remote target to respond to
16002 @var{num} seconds. The default is 2 seconds.
16004 @item show remotetimeout
16005 Show the current number of seconds to wait for the remote target
16008 @cindex limit hardware breakpoints and watchpoints
16009 @cindex remote target, limit break- and watchpoints
16010 @anchor{set remote hardware-watchpoint-limit}
16011 @anchor{set remote hardware-breakpoint-limit}
16012 @item set remote hardware-watchpoint-limit @var{limit}
16013 @itemx set remote hardware-breakpoint-limit @var{limit}
16014 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16015 watchpoints. A limit of -1, the default, is treated as unlimited.
16017 @item set remote exec-file @var{filename}
16018 @itemx show remote exec-file
16019 @anchor{set remote exec-file}
16020 @cindex executable file, for remote target
16021 Select the file used for @code{run} with @code{target
16022 extended-remote}. This should be set to a filename valid on the
16023 target system. If it is not set, the target will use a default
16024 filename (e.g.@: the last program run).
16026 @item set remote interrupt-sequence
16027 @cindex interrupt remote programs
16028 @cindex select Ctrl-C, BREAK or BREAK-g
16029 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16030 @samp{BREAK-g} as the
16031 sequence to the remote target in order to interrupt the execution.
16032 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16033 is high level of serial line for some certain time.
16034 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16035 It is @code{BREAK} signal followed by character @code{g}.
16037 @item show interrupt-sequence
16038 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16039 is sent by @value{GDBN} to interrupt the remote program.
16040 @code{BREAK-g} is BREAK signal followed by @code{g} and
16041 also known as Magic SysRq g.
16043 @item set remote interrupt-on-connect
16044 @cindex send interrupt-sequence on start
16045 Specify whether interrupt-sequence is sent to remote target when
16046 @value{GDBN} connects to it. This is mostly needed when you debug
16047 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16048 which is known as Magic SysRq g in order to connect @value{GDBN}.
16050 @item show interrupt-on-connect
16051 Show whether interrupt-sequence is sent
16052 to remote target when @value{GDBN} connects to it.
16056 @item set tcp auto-retry on
16057 @cindex auto-retry, for remote TCP target
16058 Enable auto-retry for remote TCP connections. This is useful if the remote
16059 debugging agent is launched in parallel with @value{GDBN}; there is a race
16060 condition because the agent may not become ready to accept the connection
16061 before @value{GDBN} attempts to connect. When auto-retry is
16062 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16063 to establish the connection using the timeout specified by
16064 @code{set tcp connect-timeout}.
16066 @item set tcp auto-retry off
16067 Do not auto-retry failed TCP connections.
16069 @item show tcp auto-retry
16070 Show the current auto-retry setting.
16072 @item set tcp connect-timeout @var{seconds}
16073 @cindex connection timeout, for remote TCP target
16074 @cindex timeout, for remote target connection
16075 Set the timeout for establishing a TCP connection to the remote target to
16076 @var{seconds}. The timeout affects both polling to retry failed connections
16077 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16078 that are merely slow to complete, and represents an approximate cumulative
16081 @item show tcp connect-timeout
16082 Show the current connection timeout setting.
16085 @cindex remote packets, enabling and disabling
16086 The @value{GDBN} remote protocol autodetects the packets supported by
16087 your debugging stub. If you need to override the autodetection, you
16088 can use these commands to enable or disable individual packets. Each
16089 packet can be set to @samp{on} (the remote target supports this
16090 packet), @samp{off} (the remote target does not support this packet),
16091 or @samp{auto} (detect remote target support for this packet). They
16092 all default to @samp{auto}. For more information about each packet,
16093 see @ref{Remote Protocol}.
16095 During normal use, you should not have to use any of these commands.
16096 If you do, that may be a bug in your remote debugging stub, or a bug
16097 in @value{GDBN}. You may want to report the problem to the
16098 @value{GDBN} developers.
16100 For each packet @var{name}, the command to enable or disable the
16101 packet is @code{set remote @var{name}-packet}. The available settings
16104 @multitable @columnfractions 0.28 0.32 0.25
16107 @tab Related Features
16109 @item @code{fetch-register}
16111 @tab @code{info registers}
16113 @item @code{set-register}
16117 @item @code{binary-download}
16119 @tab @code{load}, @code{set}
16121 @item @code{read-aux-vector}
16122 @tab @code{qXfer:auxv:read}
16123 @tab @code{info auxv}
16125 @item @code{symbol-lookup}
16126 @tab @code{qSymbol}
16127 @tab Detecting multiple threads
16129 @item @code{attach}
16130 @tab @code{vAttach}
16133 @item @code{verbose-resume}
16135 @tab Stepping or resuming multiple threads
16141 @item @code{software-breakpoint}
16145 @item @code{hardware-breakpoint}
16149 @item @code{write-watchpoint}
16153 @item @code{read-watchpoint}
16157 @item @code{access-watchpoint}
16161 @item @code{target-features}
16162 @tab @code{qXfer:features:read}
16163 @tab @code{set architecture}
16165 @item @code{library-info}
16166 @tab @code{qXfer:libraries:read}
16167 @tab @code{info sharedlibrary}
16169 @item @code{memory-map}
16170 @tab @code{qXfer:memory-map:read}
16171 @tab @code{info mem}
16173 @item @code{read-spu-object}
16174 @tab @code{qXfer:spu:read}
16175 @tab @code{info spu}
16177 @item @code{write-spu-object}
16178 @tab @code{qXfer:spu:write}
16179 @tab @code{info spu}
16181 @item @code{read-siginfo-object}
16182 @tab @code{qXfer:siginfo:read}
16183 @tab @code{print $_siginfo}
16185 @item @code{write-siginfo-object}
16186 @tab @code{qXfer:siginfo:write}
16187 @tab @code{set $_siginfo}
16189 @item @code{threads}
16190 @tab @code{qXfer:threads:read}
16191 @tab @code{info threads}
16193 @item @code{get-thread-local-@*storage-address}
16194 @tab @code{qGetTLSAddr}
16195 @tab Displaying @code{__thread} variables
16197 @item @code{get-thread-information-block-address}
16198 @tab @code{qGetTIBAddr}
16199 @tab Display MS-Windows Thread Information Block.
16201 @item @code{search-memory}
16202 @tab @code{qSearch:memory}
16205 @item @code{supported-packets}
16206 @tab @code{qSupported}
16207 @tab Remote communications parameters
16209 @item @code{pass-signals}
16210 @tab @code{QPassSignals}
16211 @tab @code{handle @var{signal}}
16213 @item @code{hostio-close-packet}
16214 @tab @code{vFile:close}
16215 @tab @code{remote get}, @code{remote put}
16217 @item @code{hostio-open-packet}
16218 @tab @code{vFile:open}
16219 @tab @code{remote get}, @code{remote put}
16221 @item @code{hostio-pread-packet}
16222 @tab @code{vFile:pread}
16223 @tab @code{remote get}, @code{remote put}
16225 @item @code{hostio-pwrite-packet}
16226 @tab @code{vFile:pwrite}
16227 @tab @code{remote get}, @code{remote put}
16229 @item @code{hostio-unlink-packet}
16230 @tab @code{vFile:unlink}
16231 @tab @code{remote delete}
16233 @item @code{noack-packet}
16234 @tab @code{QStartNoAckMode}
16235 @tab Packet acknowledgment
16237 @item @code{osdata}
16238 @tab @code{qXfer:osdata:read}
16239 @tab @code{info os}
16241 @item @code{query-attached}
16242 @tab @code{qAttached}
16243 @tab Querying remote process attach state.
16247 @section Implementing a Remote Stub
16249 @cindex debugging stub, example
16250 @cindex remote stub, example
16251 @cindex stub example, remote debugging
16252 The stub files provided with @value{GDBN} implement the target side of the
16253 communication protocol, and the @value{GDBN} side is implemented in the
16254 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16255 these subroutines to communicate, and ignore the details. (If you're
16256 implementing your own stub file, you can still ignore the details: start
16257 with one of the existing stub files. @file{sparc-stub.c} is the best
16258 organized, and therefore the easiest to read.)
16260 @cindex remote serial debugging, overview
16261 To debug a program running on another machine (the debugging
16262 @dfn{target} machine), you must first arrange for all the usual
16263 prerequisites for the program to run by itself. For example, for a C
16268 A startup routine to set up the C runtime environment; these usually
16269 have a name like @file{crt0}. The startup routine may be supplied by
16270 your hardware supplier, or you may have to write your own.
16273 A C subroutine library to support your program's
16274 subroutine calls, notably managing input and output.
16277 A way of getting your program to the other machine---for example, a
16278 download program. These are often supplied by the hardware
16279 manufacturer, but you may have to write your own from hardware
16283 The next step is to arrange for your program to use a serial port to
16284 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16285 machine). In general terms, the scheme looks like this:
16289 @value{GDBN} already understands how to use this protocol; when everything
16290 else is set up, you can simply use the @samp{target remote} command
16291 (@pxref{Targets,,Specifying a Debugging Target}).
16293 @item On the target,
16294 you must link with your program a few special-purpose subroutines that
16295 implement the @value{GDBN} remote serial protocol. The file containing these
16296 subroutines is called a @dfn{debugging stub}.
16298 On certain remote targets, you can use an auxiliary program
16299 @code{gdbserver} instead of linking a stub into your program.
16300 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16303 The debugging stub is specific to the architecture of the remote
16304 machine; for example, use @file{sparc-stub.c} to debug programs on
16307 @cindex remote serial stub list
16308 These working remote stubs are distributed with @value{GDBN}:
16313 @cindex @file{i386-stub.c}
16316 For Intel 386 and compatible architectures.
16319 @cindex @file{m68k-stub.c}
16320 @cindex Motorola 680x0
16322 For Motorola 680x0 architectures.
16325 @cindex @file{sh-stub.c}
16328 For Renesas SH architectures.
16331 @cindex @file{sparc-stub.c}
16333 For @sc{sparc} architectures.
16335 @item sparcl-stub.c
16336 @cindex @file{sparcl-stub.c}
16339 For Fujitsu @sc{sparclite} architectures.
16343 The @file{README} file in the @value{GDBN} distribution may list other
16344 recently added stubs.
16347 * Stub Contents:: What the stub can do for you
16348 * Bootstrapping:: What you must do for the stub
16349 * Debug Session:: Putting it all together
16352 @node Stub Contents
16353 @subsection What the Stub Can Do for You
16355 @cindex remote serial stub
16356 The debugging stub for your architecture supplies these three
16360 @item set_debug_traps
16361 @findex set_debug_traps
16362 @cindex remote serial stub, initialization
16363 This routine arranges for @code{handle_exception} to run when your
16364 program stops. You must call this subroutine explicitly near the
16365 beginning of your program.
16367 @item handle_exception
16368 @findex handle_exception
16369 @cindex remote serial stub, main routine
16370 This is the central workhorse, but your program never calls it
16371 explicitly---the setup code arranges for @code{handle_exception} to
16372 run when a trap is triggered.
16374 @code{handle_exception} takes control when your program stops during
16375 execution (for example, on a breakpoint), and mediates communications
16376 with @value{GDBN} on the host machine. This is where the communications
16377 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16378 representative on the target machine. It begins by sending summary
16379 information on the state of your program, then continues to execute,
16380 retrieving and transmitting any information @value{GDBN} needs, until you
16381 execute a @value{GDBN} command that makes your program resume; at that point,
16382 @code{handle_exception} returns control to your own code on the target
16386 @cindex @code{breakpoint} subroutine, remote
16387 Use this auxiliary subroutine to make your program contain a
16388 breakpoint. Depending on the particular situation, this may be the only
16389 way for @value{GDBN} to get control. For instance, if your target
16390 machine has some sort of interrupt button, you won't need to call this;
16391 pressing the interrupt button transfers control to
16392 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16393 simply receiving characters on the serial port may also trigger a trap;
16394 again, in that situation, you don't need to call @code{breakpoint} from
16395 your own program---simply running @samp{target remote} from the host
16396 @value{GDBN} session gets control.
16398 Call @code{breakpoint} if none of these is true, or if you simply want
16399 to make certain your program stops at a predetermined point for the
16400 start of your debugging session.
16403 @node Bootstrapping
16404 @subsection What You Must Do for the Stub
16406 @cindex remote stub, support routines
16407 The debugging stubs that come with @value{GDBN} are set up for a particular
16408 chip architecture, but they have no information about the rest of your
16409 debugging target machine.
16411 First of all you need to tell the stub how to communicate with the
16415 @item int getDebugChar()
16416 @findex getDebugChar
16417 Write this subroutine to read a single character from the serial port.
16418 It may be identical to @code{getchar} for your target system; a
16419 different name is used to allow you to distinguish the two if you wish.
16421 @item void putDebugChar(int)
16422 @findex putDebugChar
16423 Write this subroutine to write a single character to the serial port.
16424 It may be identical to @code{putchar} for your target system; a
16425 different name is used to allow you to distinguish the two if you wish.
16428 @cindex control C, and remote debugging
16429 @cindex interrupting remote targets
16430 If you want @value{GDBN} to be able to stop your program while it is
16431 running, you need to use an interrupt-driven serial driver, and arrange
16432 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16433 character). That is the character which @value{GDBN} uses to tell the
16434 remote system to stop.
16436 Getting the debugging target to return the proper status to @value{GDBN}
16437 probably requires changes to the standard stub; one quick and dirty way
16438 is to just execute a breakpoint instruction (the ``dirty'' part is that
16439 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16441 Other routines you need to supply are:
16444 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16445 @findex exceptionHandler
16446 Write this function to install @var{exception_address} in the exception
16447 handling tables. You need to do this because the stub does not have any
16448 way of knowing what the exception handling tables on your target system
16449 are like (for example, the processor's table might be in @sc{rom},
16450 containing entries which point to a table in @sc{ram}).
16451 @var{exception_number} is the exception number which should be changed;
16452 its meaning is architecture-dependent (for example, different numbers
16453 might represent divide by zero, misaligned access, etc). When this
16454 exception occurs, control should be transferred directly to
16455 @var{exception_address}, and the processor state (stack, registers,
16456 and so on) should be just as it is when a processor exception occurs. So if
16457 you want to use a jump instruction to reach @var{exception_address}, it
16458 should be a simple jump, not a jump to subroutine.
16460 For the 386, @var{exception_address} should be installed as an interrupt
16461 gate so that interrupts are masked while the handler runs. The gate
16462 should be at privilege level 0 (the most privileged level). The
16463 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16464 help from @code{exceptionHandler}.
16466 @item void flush_i_cache()
16467 @findex flush_i_cache
16468 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16469 instruction cache, if any, on your target machine. If there is no
16470 instruction cache, this subroutine may be a no-op.
16472 On target machines that have instruction caches, @value{GDBN} requires this
16473 function to make certain that the state of your program is stable.
16477 You must also make sure this library routine is available:
16480 @item void *memset(void *, int, int)
16482 This is the standard library function @code{memset} that sets an area of
16483 memory to a known value. If you have one of the free versions of
16484 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16485 either obtain it from your hardware manufacturer, or write your own.
16488 If you do not use the GNU C compiler, you may need other standard
16489 library subroutines as well; this varies from one stub to another,
16490 but in general the stubs are likely to use any of the common library
16491 subroutines which @code{@value{NGCC}} generates as inline code.
16494 @node Debug Session
16495 @subsection Putting it All Together
16497 @cindex remote serial debugging summary
16498 In summary, when your program is ready to debug, you must follow these
16503 Make sure you have defined the supporting low-level routines
16504 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16506 @code{getDebugChar}, @code{putDebugChar},
16507 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16511 Insert these lines near the top of your program:
16519 For the 680x0 stub only, you need to provide a variable called
16520 @code{exceptionHook}. Normally you just use:
16523 void (*exceptionHook)() = 0;
16527 but if before calling @code{set_debug_traps}, you set it to point to a
16528 function in your program, that function is called when
16529 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16530 error). The function indicated by @code{exceptionHook} is called with
16531 one parameter: an @code{int} which is the exception number.
16534 Compile and link together: your program, the @value{GDBN} debugging stub for
16535 your target architecture, and the supporting subroutines.
16538 Make sure you have a serial connection between your target machine and
16539 the @value{GDBN} host, and identify the serial port on the host.
16542 @c The "remote" target now provides a `load' command, so we should
16543 @c document that. FIXME.
16544 Download your program to your target machine (or get it there by
16545 whatever means the manufacturer provides), and start it.
16548 Start @value{GDBN} on the host, and connect to the target
16549 (@pxref{Connecting,,Connecting to a Remote Target}).
16553 @node Configurations
16554 @chapter Configuration-Specific Information
16556 While nearly all @value{GDBN} commands are available for all native and
16557 cross versions of the debugger, there are some exceptions. This chapter
16558 describes things that are only available in certain configurations.
16560 There are three major categories of configurations: native
16561 configurations, where the host and target are the same, embedded
16562 operating system configurations, which are usually the same for several
16563 different processor architectures, and bare embedded processors, which
16564 are quite different from each other.
16569 * Embedded Processors::
16576 This section describes details specific to particular native
16581 * BSD libkvm Interface:: Debugging BSD kernel memory images
16582 * SVR4 Process Information:: SVR4 process information
16583 * DJGPP Native:: Features specific to the DJGPP port
16584 * Cygwin Native:: Features specific to the Cygwin port
16585 * Hurd Native:: Features specific to @sc{gnu} Hurd
16586 * Neutrino:: Features specific to QNX Neutrino
16587 * Darwin:: Features specific to Darwin
16593 On HP-UX systems, if you refer to a function or variable name that
16594 begins with a dollar sign, @value{GDBN} searches for a user or system
16595 name first, before it searches for a convenience variable.
16598 @node BSD libkvm Interface
16599 @subsection BSD libkvm Interface
16602 @cindex kernel memory image
16603 @cindex kernel crash dump
16605 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16606 interface that provides a uniform interface for accessing kernel virtual
16607 memory images, including live systems and crash dumps. @value{GDBN}
16608 uses this interface to allow you to debug live kernels and kernel crash
16609 dumps on many native BSD configurations. This is implemented as a
16610 special @code{kvm} debugging target. For debugging a live system, load
16611 the currently running kernel into @value{GDBN} and connect to the
16615 (@value{GDBP}) @b{target kvm}
16618 For debugging crash dumps, provide the file name of the crash dump as an
16622 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16625 Once connected to the @code{kvm} target, the following commands are
16631 Set current context from the @dfn{Process Control Block} (PCB) address.
16634 Set current context from proc address. This command isn't available on
16635 modern FreeBSD systems.
16638 @node SVR4 Process Information
16639 @subsection SVR4 Process Information
16641 @cindex examine process image
16642 @cindex process info via @file{/proc}
16644 Many versions of SVR4 and compatible systems provide a facility called
16645 @samp{/proc} that can be used to examine the image of a running
16646 process using file-system subroutines. If @value{GDBN} is configured
16647 for an operating system with this facility, the command @code{info
16648 proc} is available to report information about the process running
16649 your program, or about any process running on your system. @code{info
16650 proc} works only on SVR4 systems that include the @code{procfs} code.
16651 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16652 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16658 @itemx info proc @var{process-id}
16659 Summarize available information about any running process. If a
16660 process ID is specified by @var{process-id}, display information about
16661 that process; otherwise display information about the program being
16662 debugged. The summary includes the debugged process ID, the command
16663 line used to invoke it, its current working directory, and its
16664 executable file's absolute file name.
16666 On some systems, @var{process-id} can be of the form
16667 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16668 within a process. If the optional @var{pid} part is missing, it means
16669 a thread from the process being debugged (the leading @samp{/} still
16670 needs to be present, or else @value{GDBN} will interpret the number as
16671 a process ID rather than a thread ID).
16673 @item info proc mappings
16674 @cindex memory address space mappings
16675 Report the memory address space ranges accessible in the program, with
16676 information on whether the process has read, write, or execute access
16677 rights to each range. On @sc{gnu}/Linux systems, each memory range
16678 includes the object file which is mapped to that range, instead of the
16679 memory access rights to that range.
16681 @item info proc stat
16682 @itemx info proc status
16683 @cindex process detailed status information
16684 These subcommands are specific to @sc{gnu}/Linux systems. They show
16685 the process-related information, including the user ID and group ID;
16686 how many threads are there in the process; its virtual memory usage;
16687 the signals that are pending, blocked, and ignored; its TTY; its
16688 consumption of system and user time; its stack size; its @samp{nice}
16689 value; etc. For more information, see the @samp{proc} man page
16690 (type @kbd{man 5 proc} from your shell prompt).
16692 @item info proc all
16693 Show all the information about the process described under all of the
16694 above @code{info proc} subcommands.
16697 @comment These sub-options of 'info proc' were not included when
16698 @comment procfs.c was re-written. Keep their descriptions around
16699 @comment against the day when someone finds the time to put them back in.
16700 @kindex info proc times
16701 @item info proc times
16702 Starting time, user CPU time, and system CPU time for your program and
16705 @kindex info proc id
16707 Report on the process IDs related to your program: its own process ID,
16708 the ID of its parent, the process group ID, and the session ID.
16711 @item set procfs-trace
16712 @kindex set procfs-trace
16713 @cindex @code{procfs} API calls
16714 This command enables and disables tracing of @code{procfs} API calls.
16716 @item show procfs-trace
16717 @kindex show procfs-trace
16718 Show the current state of @code{procfs} API call tracing.
16720 @item set procfs-file @var{file}
16721 @kindex set procfs-file
16722 Tell @value{GDBN} to write @code{procfs} API trace to the named
16723 @var{file}. @value{GDBN} appends the trace info to the previous
16724 contents of the file. The default is to display the trace on the
16727 @item show procfs-file
16728 @kindex show procfs-file
16729 Show the file to which @code{procfs} API trace is written.
16731 @item proc-trace-entry
16732 @itemx proc-trace-exit
16733 @itemx proc-untrace-entry
16734 @itemx proc-untrace-exit
16735 @kindex proc-trace-entry
16736 @kindex proc-trace-exit
16737 @kindex proc-untrace-entry
16738 @kindex proc-untrace-exit
16739 These commands enable and disable tracing of entries into and exits
16740 from the @code{syscall} interface.
16743 @kindex info pidlist
16744 @cindex process list, QNX Neutrino
16745 For QNX Neutrino only, this command displays the list of all the
16746 processes and all the threads within each process.
16749 @kindex info meminfo
16750 @cindex mapinfo list, QNX Neutrino
16751 For QNX Neutrino only, this command displays the list of all mapinfos.
16755 @subsection Features for Debugging @sc{djgpp} Programs
16756 @cindex @sc{djgpp} debugging
16757 @cindex native @sc{djgpp} debugging
16758 @cindex MS-DOS-specific commands
16761 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16762 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16763 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16764 top of real-mode DOS systems and their emulations.
16766 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16767 defines a few commands specific to the @sc{djgpp} port. This
16768 subsection describes those commands.
16773 This is a prefix of @sc{djgpp}-specific commands which print
16774 information about the target system and important OS structures.
16777 @cindex MS-DOS system info
16778 @cindex free memory information (MS-DOS)
16779 @item info dos sysinfo
16780 This command displays assorted information about the underlying
16781 platform: the CPU type and features, the OS version and flavor, the
16782 DPMI version, and the available conventional and DPMI memory.
16787 @cindex segment descriptor tables
16788 @cindex descriptor tables display
16790 @itemx info dos ldt
16791 @itemx info dos idt
16792 These 3 commands display entries from, respectively, Global, Local,
16793 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16794 tables are data structures which store a descriptor for each segment
16795 that is currently in use. The segment's selector is an index into a
16796 descriptor table; the table entry for that index holds the
16797 descriptor's base address and limit, and its attributes and access
16800 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16801 segment (used for both data and the stack), and a DOS segment (which
16802 allows access to DOS/BIOS data structures and absolute addresses in
16803 conventional memory). However, the DPMI host will usually define
16804 additional segments in order to support the DPMI environment.
16806 @cindex garbled pointers
16807 These commands allow to display entries from the descriptor tables.
16808 Without an argument, all entries from the specified table are
16809 displayed. An argument, which should be an integer expression, means
16810 display a single entry whose index is given by the argument. For
16811 example, here's a convenient way to display information about the
16812 debugged program's data segment:
16815 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16816 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16820 This comes in handy when you want to see whether a pointer is outside
16821 the data segment's limit (i.e.@: @dfn{garbled}).
16823 @cindex page tables display (MS-DOS)
16825 @itemx info dos pte
16826 These two commands display entries from, respectively, the Page
16827 Directory and the Page Tables. Page Directories and Page Tables are
16828 data structures which control how virtual memory addresses are mapped
16829 into physical addresses. A Page Table includes an entry for every
16830 page of memory that is mapped into the program's address space; there
16831 may be several Page Tables, each one holding up to 4096 entries. A
16832 Page Directory has up to 4096 entries, one each for every Page Table
16833 that is currently in use.
16835 Without an argument, @kbd{info dos pde} displays the entire Page
16836 Directory, and @kbd{info dos pte} displays all the entries in all of
16837 the Page Tables. An argument, an integer expression, given to the
16838 @kbd{info dos pde} command means display only that entry from the Page
16839 Directory table. An argument given to the @kbd{info dos pte} command
16840 means display entries from a single Page Table, the one pointed to by
16841 the specified entry in the Page Directory.
16843 @cindex direct memory access (DMA) on MS-DOS
16844 These commands are useful when your program uses @dfn{DMA} (Direct
16845 Memory Access), which needs physical addresses to program the DMA
16848 These commands are supported only with some DPMI servers.
16850 @cindex physical address from linear address
16851 @item info dos address-pte @var{addr}
16852 This command displays the Page Table entry for a specified linear
16853 address. The argument @var{addr} is a linear address which should
16854 already have the appropriate segment's base address added to it,
16855 because this command accepts addresses which may belong to @emph{any}
16856 segment. For example, here's how to display the Page Table entry for
16857 the page where a variable @code{i} is stored:
16860 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16861 @exdent @code{Page Table entry for address 0x11a00d30:}
16862 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16866 This says that @code{i} is stored at offset @code{0xd30} from the page
16867 whose physical base address is @code{0x02698000}, and shows all the
16868 attributes of that page.
16870 Note that you must cast the addresses of variables to a @code{char *},
16871 since otherwise the value of @code{__djgpp_base_address}, the base
16872 address of all variables and functions in a @sc{djgpp} program, will
16873 be added using the rules of C pointer arithmetics: if @code{i} is
16874 declared an @code{int}, @value{GDBN} will add 4 times the value of
16875 @code{__djgpp_base_address} to the address of @code{i}.
16877 Here's another example, it displays the Page Table entry for the
16881 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16882 @exdent @code{Page Table entry for address 0x29110:}
16883 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16887 (The @code{+ 3} offset is because the transfer buffer's address is the
16888 3rd member of the @code{_go32_info_block} structure.) The output
16889 clearly shows that this DPMI server maps the addresses in conventional
16890 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16891 linear (@code{0x29110}) addresses are identical.
16893 This command is supported only with some DPMI servers.
16896 @cindex DOS serial data link, remote debugging
16897 In addition to native debugging, the DJGPP port supports remote
16898 debugging via a serial data link. The following commands are specific
16899 to remote serial debugging in the DJGPP port of @value{GDBN}.
16902 @kindex set com1base
16903 @kindex set com1irq
16904 @kindex set com2base
16905 @kindex set com2irq
16906 @kindex set com3base
16907 @kindex set com3irq
16908 @kindex set com4base
16909 @kindex set com4irq
16910 @item set com1base @var{addr}
16911 This command sets the base I/O port address of the @file{COM1} serial
16914 @item set com1irq @var{irq}
16915 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16916 for the @file{COM1} serial port.
16918 There are similar commands @samp{set com2base}, @samp{set com3irq},
16919 etc.@: for setting the port address and the @code{IRQ} lines for the
16922 @kindex show com1base
16923 @kindex show com1irq
16924 @kindex show com2base
16925 @kindex show com2irq
16926 @kindex show com3base
16927 @kindex show com3irq
16928 @kindex show com4base
16929 @kindex show com4irq
16930 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16931 display the current settings of the base address and the @code{IRQ}
16932 lines used by the COM ports.
16935 @kindex info serial
16936 @cindex DOS serial port status
16937 This command prints the status of the 4 DOS serial ports. For each
16938 port, it prints whether it's active or not, its I/O base address and
16939 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16940 counts of various errors encountered so far.
16944 @node Cygwin Native
16945 @subsection Features for Debugging MS Windows PE Executables
16946 @cindex MS Windows debugging
16947 @cindex native Cygwin debugging
16948 @cindex Cygwin-specific commands
16950 @value{GDBN} supports native debugging of MS Windows programs, including
16951 DLLs with and without symbolic debugging information.
16953 @cindex Ctrl-BREAK, MS-Windows
16954 @cindex interrupt debuggee on MS-Windows
16955 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16956 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16957 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16958 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16959 sequence, which can be used to interrupt the debuggee even if it
16962 There are various additional Cygwin-specific commands, described in
16963 this section. Working with DLLs that have no debugging symbols is
16964 described in @ref{Non-debug DLL Symbols}.
16969 This is a prefix of MS Windows-specific commands which print
16970 information about the target system and important OS structures.
16972 @item info w32 selector
16973 This command displays information returned by
16974 the Win32 API @code{GetThreadSelectorEntry} function.
16975 It takes an optional argument that is evaluated to
16976 a long value to give the information about this given selector.
16977 Without argument, this command displays information
16978 about the six segment registers.
16980 @item info w32 thread-information-block
16981 This command displays thread specific information stored in the
16982 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16983 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16987 This is a Cygwin-specific alias of @code{info shared}.
16989 @kindex dll-symbols
16991 This command loads symbols from a dll similarly to
16992 add-sym command but without the need to specify a base address.
16994 @kindex set cygwin-exceptions
16995 @cindex debugging the Cygwin DLL
16996 @cindex Cygwin DLL, debugging
16997 @item set cygwin-exceptions @var{mode}
16998 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16999 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17000 @value{GDBN} will delay recognition of exceptions, and may ignore some
17001 exceptions which seem to be caused by internal Cygwin DLL
17002 ``bookkeeping''. This option is meant primarily for debugging the
17003 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17004 @value{GDBN} users with false @code{SIGSEGV} signals.
17006 @kindex show cygwin-exceptions
17007 @item show cygwin-exceptions
17008 Displays whether @value{GDBN} will break on exceptions that happen
17009 inside the Cygwin DLL itself.
17011 @kindex set new-console
17012 @item set new-console @var{mode}
17013 If @var{mode} is @code{on} the debuggee will
17014 be started in a new console on next start.
17015 If @var{mode} is @code{off}, the debuggee will
17016 be started in the same console as the debugger.
17018 @kindex show new-console
17019 @item show new-console
17020 Displays whether a new console is used
17021 when the debuggee is started.
17023 @kindex set new-group
17024 @item set new-group @var{mode}
17025 This boolean value controls whether the debuggee should
17026 start a new group or stay in the same group as the debugger.
17027 This affects the way the Windows OS handles
17030 @kindex show new-group
17031 @item show new-group
17032 Displays current value of new-group boolean.
17034 @kindex set debugevents
17035 @item set debugevents
17036 This boolean value adds debug output concerning kernel events related
17037 to the debuggee seen by the debugger. This includes events that
17038 signal thread and process creation and exit, DLL loading and
17039 unloading, console interrupts, and debugging messages produced by the
17040 Windows @code{OutputDebugString} API call.
17042 @kindex set debugexec
17043 @item set debugexec
17044 This boolean value adds debug output concerning execute events
17045 (such as resume thread) seen by the debugger.
17047 @kindex set debugexceptions
17048 @item set debugexceptions
17049 This boolean value adds debug output concerning exceptions in the
17050 debuggee seen by the debugger.
17052 @kindex set debugmemory
17053 @item set debugmemory
17054 This boolean value adds debug output concerning debuggee memory reads
17055 and writes by the debugger.
17059 This boolean values specifies whether the debuggee is called
17060 via a shell or directly (default value is on).
17064 Displays if the debuggee will be started with a shell.
17069 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17072 @node Non-debug DLL Symbols
17073 @subsubsection Support for DLLs without Debugging Symbols
17074 @cindex DLLs with no debugging symbols
17075 @cindex Minimal symbols and DLLs
17077 Very often on windows, some of the DLLs that your program relies on do
17078 not include symbolic debugging information (for example,
17079 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17080 symbols in a DLL, it relies on the minimal amount of symbolic
17081 information contained in the DLL's export table. This section
17082 describes working with such symbols, known internally to @value{GDBN} as
17083 ``minimal symbols''.
17085 Note that before the debugged program has started execution, no DLLs
17086 will have been loaded. The easiest way around this problem is simply to
17087 start the program --- either by setting a breakpoint or letting the
17088 program run once to completion. It is also possible to force
17089 @value{GDBN} to load a particular DLL before starting the executable ---
17090 see the shared library information in @ref{Files}, or the
17091 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17092 explicitly loading symbols from a DLL with no debugging information will
17093 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17094 which may adversely affect symbol lookup performance.
17096 @subsubsection DLL Name Prefixes
17098 In keeping with the naming conventions used by the Microsoft debugging
17099 tools, DLL export symbols are made available with a prefix based on the
17100 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17101 also entered into the symbol table, so @code{CreateFileA} is often
17102 sufficient. In some cases there will be name clashes within a program
17103 (particularly if the executable itself includes full debugging symbols)
17104 necessitating the use of the fully qualified name when referring to the
17105 contents of the DLL. Use single-quotes around the name to avoid the
17106 exclamation mark (``!'') being interpreted as a language operator.
17108 Note that the internal name of the DLL may be all upper-case, even
17109 though the file name of the DLL is lower-case, or vice-versa. Since
17110 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17111 some confusion. If in doubt, try the @code{info functions} and
17112 @code{info variables} commands or even @code{maint print msymbols}
17113 (@pxref{Symbols}). Here's an example:
17116 (@value{GDBP}) info function CreateFileA
17117 All functions matching regular expression "CreateFileA":
17119 Non-debugging symbols:
17120 0x77e885f4 CreateFileA
17121 0x77e885f4 KERNEL32!CreateFileA
17125 (@value{GDBP}) info function !
17126 All functions matching regular expression "!":
17128 Non-debugging symbols:
17129 0x6100114c cygwin1!__assert
17130 0x61004034 cygwin1!_dll_crt0@@0
17131 0x61004240 cygwin1!dll_crt0(per_process *)
17135 @subsubsection Working with Minimal Symbols
17137 Symbols extracted from a DLL's export table do not contain very much
17138 type information. All that @value{GDBN} can do is guess whether a symbol
17139 refers to a function or variable depending on the linker section that
17140 contains the symbol. Also note that the actual contents of the memory
17141 contained in a DLL are not available unless the program is running. This
17142 means that you cannot examine the contents of a variable or disassemble
17143 a function within a DLL without a running program.
17145 Variables are generally treated as pointers and dereferenced
17146 automatically. For this reason, it is often necessary to prefix a
17147 variable name with the address-of operator (``&'') and provide explicit
17148 type information in the command. Here's an example of the type of
17152 (@value{GDBP}) print 'cygwin1!__argv'
17157 (@value{GDBP}) x 'cygwin1!__argv'
17158 0x10021610: "\230y\""
17161 And two possible solutions:
17164 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17165 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17169 (@value{GDBP}) x/2x &'cygwin1!__argv'
17170 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17171 (@value{GDBP}) x/x 0x10021608
17172 0x10021608: 0x0022fd98
17173 (@value{GDBP}) x/s 0x0022fd98
17174 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17177 Setting a break point within a DLL is possible even before the program
17178 starts execution. However, under these circumstances, @value{GDBN} can't
17179 examine the initial instructions of the function in order to skip the
17180 function's frame set-up code. You can work around this by using ``*&''
17181 to set the breakpoint at a raw memory address:
17184 (@value{GDBP}) break *&'python22!PyOS_Readline'
17185 Breakpoint 1 at 0x1e04eff0
17188 The author of these extensions is not entirely convinced that setting a
17189 break point within a shared DLL like @file{kernel32.dll} is completely
17193 @subsection Commands Specific to @sc{gnu} Hurd Systems
17194 @cindex @sc{gnu} Hurd debugging
17196 This subsection describes @value{GDBN} commands specific to the
17197 @sc{gnu} Hurd native debugging.
17202 @kindex set signals@r{, Hurd command}
17203 @kindex set sigs@r{, Hurd command}
17204 This command toggles the state of inferior signal interception by
17205 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17206 affected by this command. @code{sigs} is a shorthand alias for
17211 @kindex show signals@r{, Hurd command}
17212 @kindex show sigs@r{, Hurd command}
17213 Show the current state of intercepting inferior's signals.
17215 @item set signal-thread
17216 @itemx set sigthread
17217 @kindex set signal-thread
17218 @kindex set sigthread
17219 This command tells @value{GDBN} which thread is the @code{libc} signal
17220 thread. That thread is run when a signal is delivered to a running
17221 process. @code{set sigthread} is the shorthand alias of @code{set
17224 @item show signal-thread
17225 @itemx show sigthread
17226 @kindex show signal-thread
17227 @kindex show sigthread
17228 These two commands show which thread will run when the inferior is
17229 delivered a signal.
17232 @kindex set stopped@r{, Hurd command}
17233 This commands tells @value{GDBN} that the inferior process is stopped,
17234 as with the @code{SIGSTOP} signal. The stopped process can be
17235 continued by delivering a signal to it.
17238 @kindex show stopped@r{, Hurd command}
17239 This command shows whether @value{GDBN} thinks the debuggee is
17242 @item set exceptions
17243 @kindex set exceptions@r{, Hurd command}
17244 Use this command to turn off trapping of exceptions in the inferior.
17245 When exception trapping is off, neither breakpoints nor
17246 single-stepping will work. To restore the default, set exception
17249 @item show exceptions
17250 @kindex show exceptions@r{, Hurd command}
17251 Show the current state of trapping exceptions in the inferior.
17253 @item set task pause
17254 @kindex set task@r{, Hurd commands}
17255 @cindex task attributes (@sc{gnu} Hurd)
17256 @cindex pause current task (@sc{gnu} Hurd)
17257 This command toggles task suspension when @value{GDBN} has control.
17258 Setting it to on takes effect immediately, and the task is suspended
17259 whenever @value{GDBN} gets control. Setting it to off will take
17260 effect the next time the inferior is continued. If this option is set
17261 to off, you can use @code{set thread default pause on} or @code{set
17262 thread pause on} (see below) to pause individual threads.
17264 @item show task pause
17265 @kindex show task@r{, Hurd commands}
17266 Show the current state of task suspension.
17268 @item set task detach-suspend-count
17269 @cindex task suspend count
17270 @cindex detach from task, @sc{gnu} Hurd
17271 This command sets the suspend count the task will be left with when
17272 @value{GDBN} detaches from it.
17274 @item show task detach-suspend-count
17275 Show the suspend count the task will be left with when detaching.
17277 @item set task exception-port
17278 @itemx set task excp
17279 @cindex task exception port, @sc{gnu} Hurd
17280 This command sets the task exception port to which @value{GDBN} will
17281 forward exceptions. The argument should be the value of the @dfn{send
17282 rights} of the task. @code{set task excp} is a shorthand alias.
17284 @item set noninvasive
17285 @cindex noninvasive task options
17286 This command switches @value{GDBN} to a mode that is the least
17287 invasive as far as interfering with the inferior is concerned. This
17288 is the same as using @code{set task pause}, @code{set exceptions}, and
17289 @code{set signals} to values opposite to the defaults.
17291 @item info send-rights
17292 @itemx info receive-rights
17293 @itemx info port-rights
17294 @itemx info port-sets
17295 @itemx info dead-names
17298 @cindex send rights, @sc{gnu} Hurd
17299 @cindex receive rights, @sc{gnu} Hurd
17300 @cindex port rights, @sc{gnu} Hurd
17301 @cindex port sets, @sc{gnu} Hurd
17302 @cindex dead names, @sc{gnu} Hurd
17303 These commands display information about, respectively, send rights,
17304 receive rights, port rights, port sets, and dead names of a task.
17305 There are also shorthand aliases: @code{info ports} for @code{info
17306 port-rights} and @code{info psets} for @code{info port-sets}.
17308 @item set thread pause
17309 @kindex set thread@r{, Hurd command}
17310 @cindex thread properties, @sc{gnu} Hurd
17311 @cindex pause current thread (@sc{gnu} Hurd)
17312 This command toggles current thread suspension when @value{GDBN} has
17313 control. Setting it to on takes effect immediately, and the current
17314 thread is suspended whenever @value{GDBN} gets control. Setting it to
17315 off will take effect the next time the inferior is continued.
17316 Normally, this command has no effect, since when @value{GDBN} has
17317 control, the whole task is suspended. However, if you used @code{set
17318 task pause off} (see above), this command comes in handy to suspend
17319 only the current thread.
17321 @item show thread pause
17322 @kindex show thread@r{, Hurd command}
17323 This command shows the state of current thread suspension.
17325 @item set thread run
17326 This command sets whether the current thread is allowed to run.
17328 @item show thread run
17329 Show whether the current thread is allowed to run.
17331 @item set thread detach-suspend-count
17332 @cindex thread suspend count, @sc{gnu} Hurd
17333 @cindex detach from thread, @sc{gnu} Hurd
17334 This command sets the suspend count @value{GDBN} will leave on a
17335 thread when detaching. This number is relative to the suspend count
17336 found by @value{GDBN} when it notices the thread; use @code{set thread
17337 takeover-suspend-count} to force it to an absolute value.
17339 @item show thread detach-suspend-count
17340 Show the suspend count @value{GDBN} will leave on the thread when
17343 @item set thread exception-port
17344 @itemx set thread excp
17345 Set the thread exception port to which to forward exceptions. This
17346 overrides the port set by @code{set task exception-port} (see above).
17347 @code{set thread excp} is the shorthand alias.
17349 @item set thread takeover-suspend-count
17350 Normally, @value{GDBN}'s thread suspend counts are relative to the
17351 value @value{GDBN} finds when it notices each thread. This command
17352 changes the suspend counts to be absolute instead.
17354 @item set thread default
17355 @itemx show thread default
17356 @cindex thread default settings, @sc{gnu} Hurd
17357 Each of the above @code{set thread} commands has a @code{set thread
17358 default} counterpart (e.g., @code{set thread default pause}, @code{set
17359 thread default exception-port}, etc.). The @code{thread default}
17360 variety of commands sets the default thread properties for all
17361 threads; you can then change the properties of individual threads with
17362 the non-default commands.
17367 @subsection QNX Neutrino
17368 @cindex QNX Neutrino
17370 @value{GDBN} provides the following commands specific to the QNX
17374 @item set debug nto-debug
17375 @kindex set debug nto-debug
17376 When set to on, enables debugging messages specific to the QNX
17379 @item show debug nto-debug
17380 @kindex show debug nto-debug
17381 Show the current state of QNX Neutrino messages.
17388 @value{GDBN} provides the following commands specific to the Darwin target:
17391 @item set debug darwin @var{num}
17392 @kindex set debug darwin
17393 When set to a non zero value, enables debugging messages specific to
17394 the Darwin support. Higher values produce more verbose output.
17396 @item show debug darwin
17397 @kindex show debug darwin
17398 Show the current state of Darwin messages.
17400 @item set debug mach-o @var{num}
17401 @kindex set debug mach-o
17402 When set to a non zero value, enables debugging messages while
17403 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17404 file format used on Darwin for object and executable files.) Higher
17405 values produce more verbose output. This is a command to diagnose
17406 problems internal to @value{GDBN} and should not be needed in normal
17409 @item show debug mach-o
17410 @kindex show debug mach-o
17411 Show the current state of Mach-O file messages.
17413 @item set mach-exceptions on
17414 @itemx set mach-exceptions off
17415 @kindex set mach-exceptions
17416 On Darwin, faults are first reported as a Mach exception and are then
17417 mapped to a Posix signal. Use this command to turn on trapping of
17418 Mach exceptions in the inferior. This might be sometimes useful to
17419 better understand the cause of a fault. The default is off.
17421 @item show mach-exceptions
17422 @kindex show mach-exceptions
17423 Show the current state of exceptions trapping.
17428 @section Embedded Operating Systems
17430 This section describes configurations involving the debugging of
17431 embedded operating systems that are available for several different
17435 * VxWorks:: Using @value{GDBN} with VxWorks
17438 @value{GDBN} includes the ability to debug programs running on
17439 various real-time operating systems.
17442 @subsection Using @value{GDBN} with VxWorks
17448 @kindex target vxworks
17449 @item target vxworks @var{machinename}
17450 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17451 is the target system's machine name or IP address.
17455 On VxWorks, @code{load} links @var{filename} dynamically on the
17456 current target system as well as adding its symbols in @value{GDBN}.
17458 @value{GDBN} enables developers to spawn and debug tasks running on networked
17459 VxWorks targets from a Unix host. Already-running tasks spawned from
17460 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17461 both the Unix host and on the VxWorks target. The program
17462 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17463 installed with the name @code{vxgdb}, to distinguish it from a
17464 @value{GDBN} for debugging programs on the host itself.)
17467 @item VxWorks-timeout @var{args}
17468 @kindex vxworks-timeout
17469 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17470 This option is set by the user, and @var{args} represents the number of
17471 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17472 your VxWorks target is a slow software simulator or is on the far side
17473 of a thin network line.
17476 The following information on connecting to VxWorks was current when
17477 this manual was produced; newer releases of VxWorks may use revised
17480 @findex INCLUDE_RDB
17481 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17482 to include the remote debugging interface routines in the VxWorks
17483 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17484 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17485 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17486 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17487 information on configuring and remaking VxWorks, see the manufacturer's
17489 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17491 Once you have included @file{rdb.a} in your VxWorks system image and set
17492 your Unix execution search path to find @value{GDBN}, you are ready to
17493 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17494 @code{vxgdb}, depending on your installation).
17496 @value{GDBN} comes up showing the prompt:
17503 * VxWorks Connection:: Connecting to VxWorks
17504 * VxWorks Download:: VxWorks download
17505 * VxWorks Attach:: Running tasks
17508 @node VxWorks Connection
17509 @subsubsection Connecting to VxWorks
17511 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17512 network. To connect to a target whose host name is ``@code{tt}'', type:
17515 (vxgdb) target vxworks tt
17519 @value{GDBN} displays messages like these:
17522 Attaching remote machine across net...
17527 @value{GDBN} then attempts to read the symbol tables of any object modules
17528 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17529 these files by searching the directories listed in the command search
17530 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17531 to find an object file, it displays a message such as:
17534 prog.o: No such file or directory.
17537 When this happens, add the appropriate directory to the search path with
17538 the @value{GDBN} command @code{path}, and execute the @code{target}
17541 @node VxWorks Download
17542 @subsubsection VxWorks Download
17544 @cindex download to VxWorks
17545 If you have connected to the VxWorks target and you want to debug an
17546 object that has not yet been loaded, you can use the @value{GDBN}
17547 @code{load} command to download a file from Unix to VxWorks
17548 incrementally. The object file given as an argument to the @code{load}
17549 command is actually opened twice: first by the VxWorks target in order
17550 to download the code, then by @value{GDBN} in order to read the symbol
17551 table. This can lead to problems if the current working directories on
17552 the two systems differ. If both systems have NFS mounted the same
17553 filesystems, you can avoid these problems by using absolute paths.
17554 Otherwise, it is simplest to set the working directory on both systems
17555 to the directory in which the object file resides, and then to reference
17556 the file by its name, without any path. For instance, a program
17557 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17558 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17559 program, type this on VxWorks:
17562 -> cd "@var{vxpath}/vw/demo/rdb"
17566 Then, in @value{GDBN}, type:
17569 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17570 (vxgdb) load prog.o
17573 @value{GDBN} displays a response similar to this:
17576 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17579 You can also use the @code{load} command to reload an object module
17580 after editing and recompiling the corresponding source file. Note that
17581 this makes @value{GDBN} delete all currently-defined breakpoints,
17582 auto-displays, and convenience variables, and to clear the value
17583 history. (This is necessary in order to preserve the integrity of
17584 debugger's data structures that reference the target system's symbol
17587 @node VxWorks Attach
17588 @subsubsection Running Tasks
17590 @cindex running VxWorks tasks
17591 You can also attach to an existing task using the @code{attach} command as
17595 (vxgdb) attach @var{task}
17599 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17600 or suspended when you attach to it. Running tasks are suspended at
17601 the time of attachment.
17603 @node Embedded Processors
17604 @section Embedded Processors
17606 This section goes into details specific to particular embedded
17609 @cindex send command to simulator
17610 Whenever a specific embedded processor has a simulator, @value{GDBN}
17611 allows to send an arbitrary command to the simulator.
17614 @item sim @var{command}
17615 @kindex sim@r{, a command}
17616 Send an arbitrary @var{command} string to the simulator. Consult the
17617 documentation for the specific simulator in use for information about
17618 acceptable commands.
17624 * M32R/D:: Renesas M32R/D
17625 * M68K:: Motorola M68K
17626 * MicroBlaze:: Xilinx MicroBlaze
17627 * MIPS Embedded:: MIPS Embedded
17628 * OpenRISC 1000:: OpenRisc 1000
17629 * PA:: HP PA Embedded
17630 * PowerPC Embedded:: PowerPC Embedded
17631 * Sparclet:: Tsqware Sparclet
17632 * Sparclite:: Fujitsu Sparclite
17633 * Z8000:: Zilog Z8000
17636 * Super-H:: Renesas Super-H
17645 @item target rdi @var{dev}
17646 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17647 use this target to communicate with both boards running the Angel
17648 monitor, or with the EmbeddedICE JTAG debug device.
17651 @item target rdp @var{dev}
17656 @value{GDBN} provides the following ARM-specific commands:
17659 @item set arm disassembler
17661 This commands selects from a list of disassembly styles. The
17662 @code{"std"} style is the standard style.
17664 @item show arm disassembler
17666 Show the current disassembly style.
17668 @item set arm apcs32
17669 @cindex ARM 32-bit mode
17670 This command toggles ARM operation mode between 32-bit and 26-bit.
17672 @item show arm apcs32
17673 Display the current usage of the ARM 32-bit mode.
17675 @item set arm fpu @var{fputype}
17676 This command sets the ARM floating-point unit (FPU) type. The
17677 argument @var{fputype} can be one of these:
17681 Determine the FPU type by querying the OS ABI.
17683 Software FPU, with mixed-endian doubles on little-endian ARM
17686 GCC-compiled FPA co-processor.
17688 Software FPU with pure-endian doubles.
17694 Show the current type of the FPU.
17697 This command forces @value{GDBN} to use the specified ABI.
17700 Show the currently used ABI.
17702 @item set arm fallback-mode (arm|thumb|auto)
17703 @value{GDBN} uses the symbol table, when available, to determine
17704 whether instructions are ARM or Thumb. This command controls
17705 @value{GDBN}'s default behavior when the symbol table is not
17706 available. The default is @samp{auto}, which causes @value{GDBN} to
17707 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17710 @item show arm fallback-mode
17711 Show the current fallback instruction mode.
17713 @item set arm force-mode (arm|thumb|auto)
17714 This command overrides use of the symbol table to determine whether
17715 instructions are ARM or Thumb. The default is @samp{auto}, which
17716 causes @value{GDBN} to use the symbol table and then the setting
17717 of @samp{set arm fallback-mode}.
17719 @item show arm force-mode
17720 Show the current forced instruction mode.
17722 @item set debug arm
17723 Toggle whether to display ARM-specific debugging messages from the ARM
17724 target support subsystem.
17726 @item show debug arm
17727 Show whether ARM-specific debugging messages are enabled.
17730 The following commands are available when an ARM target is debugged
17731 using the RDI interface:
17734 @item rdilogfile @r{[}@var{file}@r{]}
17736 @cindex ADP (Angel Debugger Protocol) logging
17737 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17738 With an argument, sets the log file to the specified @var{file}. With
17739 no argument, show the current log file name. The default log file is
17742 @item rdilogenable @r{[}@var{arg}@r{]}
17743 @kindex rdilogenable
17744 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17745 enables logging, with an argument 0 or @code{"no"} disables it. With
17746 no arguments displays the current setting. When logging is enabled,
17747 ADP packets exchanged between @value{GDBN} and the RDI target device
17748 are logged to a file.
17750 @item set rdiromatzero
17751 @kindex set rdiromatzero
17752 @cindex ROM at zero address, RDI
17753 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17754 vector catching is disabled, so that zero address can be used. If off
17755 (the default), vector catching is enabled. For this command to take
17756 effect, it needs to be invoked prior to the @code{target rdi} command.
17758 @item show rdiromatzero
17759 @kindex show rdiromatzero
17760 Show the current setting of ROM at zero address.
17762 @item set rdiheartbeat
17763 @kindex set rdiheartbeat
17764 @cindex RDI heartbeat
17765 Enable or disable RDI heartbeat packets. It is not recommended to
17766 turn on this option, since it confuses ARM and EPI JTAG interface, as
17767 well as the Angel monitor.
17769 @item show rdiheartbeat
17770 @kindex show rdiheartbeat
17771 Show the setting of RDI heartbeat packets.
17775 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17776 The @value{GDBN} ARM simulator accepts the following optional arguments.
17779 @item --swi-support=@var{type}
17780 Tell the simulator which SWI interfaces to support.
17781 @var{type} may be a comma separated list of the following values.
17782 The default value is @code{all}.
17795 @subsection Renesas M32R/D and M32R/SDI
17798 @kindex target m32r
17799 @item target m32r @var{dev}
17800 Renesas M32R/D ROM monitor.
17802 @kindex target m32rsdi
17803 @item target m32rsdi @var{dev}
17804 Renesas M32R SDI server, connected via parallel port to the board.
17807 The following @value{GDBN} commands are specific to the M32R monitor:
17810 @item set download-path @var{path}
17811 @kindex set download-path
17812 @cindex find downloadable @sc{srec} files (M32R)
17813 Set the default path for finding downloadable @sc{srec} files.
17815 @item show download-path
17816 @kindex show download-path
17817 Show the default path for downloadable @sc{srec} files.
17819 @item set board-address @var{addr}
17820 @kindex set board-address
17821 @cindex M32-EVA target board address
17822 Set the IP address for the M32R-EVA target board.
17824 @item show board-address
17825 @kindex show board-address
17826 Show the current IP address of the target board.
17828 @item set server-address @var{addr}
17829 @kindex set server-address
17830 @cindex download server address (M32R)
17831 Set the IP address for the download server, which is the @value{GDBN}'s
17834 @item show server-address
17835 @kindex show server-address
17836 Display the IP address of the download server.
17838 @item upload @r{[}@var{file}@r{]}
17839 @kindex upload@r{, M32R}
17840 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17841 upload capability. If no @var{file} argument is given, the current
17842 executable file is uploaded.
17844 @item tload @r{[}@var{file}@r{]}
17845 @kindex tload@r{, M32R}
17846 Test the @code{upload} command.
17849 The following commands are available for M32R/SDI:
17854 @cindex reset SDI connection, M32R
17855 This command resets the SDI connection.
17859 This command shows the SDI connection status.
17862 @kindex debug_chaos
17863 @cindex M32R/Chaos debugging
17864 Instructs the remote that M32R/Chaos debugging is to be used.
17866 @item use_debug_dma
17867 @kindex use_debug_dma
17868 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17871 @kindex use_mon_code
17872 Instructs the remote to use the MON_CODE method of accessing memory.
17875 @kindex use_ib_break
17876 Instructs the remote to set breakpoints by IB break.
17878 @item use_dbt_break
17879 @kindex use_dbt_break
17880 Instructs the remote to set breakpoints by DBT.
17886 The Motorola m68k configuration includes ColdFire support, and a
17887 target command for the following ROM monitor.
17891 @kindex target dbug
17892 @item target dbug @var{dev}
17893 dBUG ROM monitor for Motorola ColdFire.
17898 @subsection MicroBlaze
17899 @cindex Xilinx MicroBlaze
17900 @cindex XMD, Xilinx Microprocessor Debugger
17902 The MicroBlaze is a soft-core processor supported on various Xilinx
17903 FPGAs, such as Spartan or Virtex series. Boards with these processors
17904 usually have JTAG ports which connect to a host system running the Xilinx
17905 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17906 This host system is used to download the configuration bitstream to
17907 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17908 communicates with the target board using the JTAG interface and
17909 presents a @code{gdbserver} interface to the board. By default
17910 @code{xmd} uses port @code{1234}. (While it is possible to change
17911 this default port, it requires the use of undocumented @code{xmd}
17912 commands. Contact Xilinx support if you need to do this.)
17914 Use these GDB commands to connect to the MicroBlaze target processor.
17917 @item target remote :1234
17918 Use this command to connect to the target if you are running @value{GDBN}
17919 on the same system as @code{xmd}.
17921 @item target remote @var{xmd-host}:1234
17922 Use this command to connect to the target if it is connected to @code{xmd}
17923 running on a different system named @var{xmd-host}.
17926 Use this command to download a program to the MicroBlaze target.
17928 @item set debug microblaze @var{n}
17929 Enable MicroBlaze-specific debugging messages if non-zero.
17931 @item show debug microblaze @var{n}
17932 Show MicroBlaze-specific debugging level.
17935 @node MIPS Embedded
17936 @subsection MIPS Embedded
17938 @cindex MIPS boards
17939 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17940 MIPS board attached to a serial line. This is available when
17941 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17944 Use these @value{GDBN} commands to specify the connection to your target board:
17947 @item target mips @var{port}
17948 @kindex target mips @var{port}
17949 To run a program on the board, start up @code{@value{GDBP}} with the
17950 name of your program as the argument. To connect to the board, use the
17951 command @samp{target mips @var{port}}, where @var{port} is the name of
17952 the serial port connected to the board. If the program has not already
17953 been downloaded to the board, you may use the @code{load} command to
17954 download it. You can then use all the usual @value{GDBN} commands.
17956 For example, this sequence connects to the target board through a serial
17957 port, and loads and runs a program called @var{prog} through the
17961 host$ @value{GDBP} @var{prog}
17962 @value{GDBN} is free software and @dots{}
17963 (@value{GDBP}) target mips /dev/ttyb
17964 (@value{GDBP}) load @var{prog}
17968 @item target mips @var{hostname}:@var{portnumber}
17969 On some @value{GDBN} host configurations, you can specify a TCP
17970 connection (for instance, to a serial line managed by a terminal
17971 concentrator) instead of a serial port, using the syntax
17972 @samp{@var{hostname}:@var{portnumber}}.
17974 @item target pmon @var{port}
17975 @kindex target pmon @var{port}
17978 @item target ddb @var{port}
17979 @kindex target ddb @var{port}
17980 NEC's DDB variant of PMON for Vr4300.
17982 @item target lsi @var{port}
17983 @kindex target lsi @var{port}
17984 LSI variant of PMON.
17986 @kindex target r3900
17987 @item target r3900 @var{dev}
17988 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17990 @kindex target array
17991 @item target array @var{dev}
17992 Array Tech LSI33K RAID controller board.
17998 @value{GDBN} also supports these special commands for MIPS targets:
18001 @item set mipsfpu double
18002 @itemx set mipsfpu single
18003 @itemx set mipsfpu none
18004 @itemx set mipsfpu auto
18005 @itemx show mipsfpu
18006 @kindex set mipsfpu
18007 @kindex show mipsfpu
18008 @cindex MIPS remote floating point
18009 @cindex floating point, MIPS remote
18010 If your target board does not support the MIPS floating point
18011 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18012 need this, you may wish to put the command in your @value{GDBN} init
18013 file). This tells @value{GDBN} how to find the return value of
18014 functions which return floating point values. It also allows
18015 @value{GDBN} to avoid saving the floating point registers when calling
18016 functions on the board. If you are using a floating point coprocessor
18017 with only single precision floating point support, as on the @sc{r4650}
18018 processor, use the command @samp{set mipsfpu single}. The default
18019 double precision floating point coprocessor may be selected using
18020 @samp{set mipsfpu double}.
18022 In previous versions the only choices were double precision or no
18023 floating point, so @samp{set mipsfpu on} will select double precision
18024 and @samp{set mipsfpu off} will select no floating point.
18026 As usual, you can inquire about the @code{mipsfpu} variable with
18027 @samp{show mipsfpu}.
18029 @item set timeout @var{seconds}
18030 @itemx set retransmit-timeout @var{seconds}
18031 @itemx show timeout
18032 @itemx show retransmit-timeout
18033 @cindex @code{timeout}, MIPS protocol
18034 @cindex @code{retransmit-timeout}, MIPS protocol
18035 @kindex set timeout
18036 @kindex show timeout
18037 @kindex set retransmit-timeout
18038 @kindex show retransmit-timeout
18039 You can control the timeout used while waiting for a packet, in the MIPS
18040 remote protocol, with the @code{set timeout @var{seconds}} command. The
18041 default is 5 seconds. Similarly, you can control the timeout used while
18042 waiting for an acknowledgment of a packet with the @code{set
18043 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18044 You can inspect both values with @code{show timeout} and @code{show
18045 retransmit-timeout}. (These commands are @emph{only} available when
18046 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18048 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18049 is waiting for your program to stop. In that case, @value{GDBN} waits
18050 forever because it has no way of knowing how long the program is going
18051 to run before stopping.
18053 @item set syn-garbage-limit @var{num}
18054 @kindex set syn-garbage-limit@r{, MIPS remote}
18055 @cindex synchronize with remote MIPS target
18056 Limit the maximum number of characters @value{GDBN} should ignore when
18057 it tries to synchronize with the remote target. The default is 10
18058 characters. Setting the limit to -1 means there's no limit.
18060 @item show syn-garbage-limit
18061 @kindex show syn-garbage-limit@r{, MIPS remote}
18062 Show the current limit on the number of characters to ignore when
18063 trying to synchronize with the remote system.
18065 @item set monitor-prompt @var{prompt}
18066 @kindex set monitor-prompt@r{, MIPS remote}
18067 @cindex remote monitor prompt
18068 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18069 remote monitor. The default depends on the target:
18079 @item show monitor-prompt
18080 @kindex show monitor-prompt@r{, MIPS remote}
18081 Show the current strings @value{GDBN} expects as the prompt from the
18084 @item set monitor-warnings
18085 @kindex set monitor-warnings@r{, MIPS remote}
18086 Enable or disable monitor warnings about hardware breakpoints. This
18087 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18088 display warning messages whose codes are returned by the @code{lsi}
18089 PMON monitor for breakpoint commands.
18091 @item show monitor-warnings
18092 @kindex show monitor-warnings@r{, MIPS remote}
18093 Show the current setting of printing monitor warnings.
18095 @item pmon @var{command}
18096 @kindex pmon@r{, MIPS remote}
18097 @cindex send PMON command
18098 This command allows sending an arbitrary @var{command} string to the
18099 monitor. The monitor must be in debug mode for this to work.
18102 @node OpenRISC 1000
18103 @subsection OpenRISC 1000
18104 @cindex OpenRISC 1000
18106 @cindex or1k boards
18107 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18108 about platform and commands.
18112 @kindex target jtag
18113 @item target jtag jtag://@var{host}:@var{port}
18115 Connects to remote JTAG server.
18116 JTAG remote server can be either an or1ksim or JTAG server,
18117 connected via parallel port to the board.
18119 Example: @code{target jtag jtag://localhost:9999}
18122 @item or1ksim @var{command}
18123 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18124 Simulator, proprietary commands can be executed.
18126 @kindex info or1k spr
18127 @item info or1k spr
18128 Displays spr groups.
18130 @item info or1k spr @var{group}
18131 @itemx info or1k spr @var{groupno}
18132 Displays register names in selected group.
18134 @item info or1k spr @var{group} @var{register}
18135 @itemx info or1k spr @var{register}
18136 @itemx info or1k spr @var{groupno} @var{registerno}
18137 @itemx info or1k spr @var{registerno}
18138 Shows information about specified spr register.
18141 @item spr @var{group} @var{register} @var{value}
18142 @itemx spr @var{register @var{value}}
18143 @itemx spr @var{groupno} @var{registerno @var{value}}
18144 @itemx spr @var{registerno @var{value}}
18145 Writes @var{value} to specified spr register.
18148 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18149 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18150 program execution and is thus much faster. Hardware breakpoints/watchpoint
18151 triggers can be set using:
18154 Load effective address/data
18156 Store effective address/data
18158 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18163 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18164 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18166 @code{htrace} commands:
18167 @cindex OpenRISC 1000 htrace
18170 @item hwatch @var{conditional}
18171 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18172 or Data. For example:
18174 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18176 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18180 Display information about current HW trace configuration.
18182 @item htrace trigger @var{conditional}
18183 Set starting criteria for HW trace.
18185 @item htrace qualifier @var{conditional}
18186 Set acquisition qualifier for HW trace.
18188 @item htrace stop @var{conditional}
18189 Set HW trace stopping criteria.
18191 @item htrace record [@var{data}]*
18192 Selects the data to be recorded, when qualifier is met and HW trace was
18195 @item htrace enable
18196 @itemx htrace disable
18197 Enables/disables the HW trace.
18199 @item htrace rewind [@var{filename}]
18200 Clears currently recorded trace data.
18202 If filename is specified, new trace file is made and any newly collected data
18203 will be written there.
18205 @item htrace print [@var{start} [@var{len}]]
18206 Prints trace buffer, using current record configuration.
18208 @item htrace mode continuous
18209 Set continuous trace mode.
18211 @item htrace mode suspend
18212 Set suspend trace mode.
18216 @node PowerPC Embedded
18217 @subsection PowerPC Embedded
18219 @value{GDBN} provides the following PowerPC-specific commands:
18222 @kindex set powerpc
18223 @item set powerpc soft-float
18224 @itemx show powerpc soft-float
18225 Force @value{GDBN} to use (or not use) a software floating point calling
18226 convention. By default, @value{GDBN} selects the calling convention based
18227 on the selected architecture and the provided executable file.
18229 @item set powerpc vector-abi
18230 @itemx show powerpc vector-abi
18231 Force @value{GDBN} to use the specified calling convention for vector
18232 arguments and return values. The valid options are @samp{auto};
18233 @samp{generic}, to avoid vector registers even if they are present;
18234 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18235 registers. By default, @value{GDBN} selects the calling convention
18236 based on the selected architecture and the provided executable file.
18238 @kindex target dink32
18239 @item target dink32 @var{dev}
18240 DINK32 ROM monitor.
18242 @kindex target ppcbug
18243 @item target ppcbug @var{dev}
18244 @kindex target ppcbug1
18245 @item target ppcbug1 @var{dev}
18246 PPCBUG ROM monitor for PowerPC.
18249 @item target sds @var{dev}
18250 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18253 @cindex SDS protocol
18254 The following commands specific to the SDS protocol are supported
18258 @item set sdstimeout @var{nsec}
18259 @kindex set sdstimeout
18260 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18261 default is 2 seconds.
18263 @item show sdstimeout
18264 @kindex show sdstimeout
18265 Show the current value of the SDS timeout.
18267 @item sds @var{command}
18268 @kindex sds@r{, a command}
18269 Send the specified @var{command} string to the SDS monitor.
18274 @subsection HP PA Embedded
18278 @kindex target op50n
18279 @item target op50n @var{dev}
18280 OP50N monitor, running on an OKI HPPA board.
18282 @kindex target w89k
18283 @item target w89k @var{dev}
18284 W89K monitor, running on a Winbond HPPA board.
18289 @subsection Tsqware Sparclet
18293 @value{GDBN} enables developers to debug tasks running on
18294 Sparclet targets from a Unix host.
18295 @value{GDBN} uses code that runs on
18296 both the Unix host and on the Sparclet target. The program
18297 @code{@value{GDBP}} is installed and executed on the Unix host.
18300 @item remotetimeout @var{args}
18301 @kindex remotetimeout
18302 @value{GDBN} supports the option @code{remotetimeout}.
18303 This option is set by the user, and @var{args} represents the number of
18304 seconds @value{GDBN} waits for responses.
18307 @cindex compiling, on Sparclet
18308 When compiling for debugging, include the options @samp{-g} to get debug
18309 information and @samp{-Ttext} to relocate the program to where you wish to
18310 load it on the target. You may also want to add the options @samp{-n} or
18311 @samp{-N} in order to reduce the size of the sections. Example:
18314 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18317 You can use @code{objdump} to verify that the addresses are what you intended:
18320 sparclet-aout-objdump --headers --syms prog
18323 @cindex running, on Sparclet
18325 your Unix execution search path to find @value{GDBN}, you are ready to
18326 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18327 (or @code{sparclet-aout-gdb}, depending on your installation).
18329 @value{GDBN} comes up showing the prompt:
18336 * Sparclet File:: Setting the file to debug
18337 * Sparclet Connection:: Connecting to Sparclet
18338 * Sparclet Download:: Sparclet download
18339 * Sparclet Execution:: Running and debugging
18342 @node Sparclet File
18343 @subsubsection Setting File to Debug
18345 The @value{GDBN} command @code{file} lets you choose with program to debug.
18348 (gdbslet) file prog
18352 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18353 @value{GDBN} locates
18354 the file by searching the directories listed in the command search
18356 If the file was compiled with debug information (option @samp{-g}), source
18357 files will be searched as well.
18358 @value{GDBN} locates
18359 the source files by searching the directories listed in the directory search
18360 path (@pxref{Environment, ,Your Program's Environment}).
18362 to find a file, it displays a message such as:
18365 prog: No such file or directory.
18368 When this happens, add the appropriate directories to the search paths with
18369 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18370 @code{target} command again.
18372 @node Sparclet Connection
18373 @subsubsection Connecting to Sparclet
18375 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18376 To connect to a target on serial port ``@code{ttya}'', type:
18379 (gdbslet) target sparclet /dev/ttya
18380 Remote target sparclet connected to /dev/ttya
18381 main () at ../prog.c:3
18385 @value{GDBN} displays messages like these:
18391 @node Sparclet Download
18392 @subsubsection Sparclet Download
18394 @cindex download to Sparclet
18395 Once connected to the Sparclet target,
18396 you can use the @value{GDBN}
18397 @code{load} command to download the file from the host to the target.
18398 The file name and load offset should be given as arguments to the @code{load}
18400 Since the file format is aout, the program must be loaded to the starting
18401 address. You can use @code{objdump} to find out what this value is. The load
18402 offset is an offset which is added to the VMA (virtual memory address)
18403 of each of the file's sections.
18404 For instance, if the program
18405 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18406 and bss at 0x12010170, in @value{GDBN}, type:
18409 (gdbslet) load prog 0x12010000
18410 Loading section .text, size 0xdb0 vma 0x12010000
18413 If the code is loaded at a different address then what the program was linked
18414 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18415 to tell @value{GDBN} where to map the symbol table.
18417 @node Sparclet Execution
18418 @subsubsection Running and Debugging
18420 @cindex running and debugging Sparclet programs
18421 You can now begin debugging the task using @value{GDBN}'s execution control
18422 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18423 manual for the list of commands.
18427 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18429 Starting program: prog
18430 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18431 3 char *symarg = 0;
18433 4 char *execarg = "hello!";
18438 @subsection Fujitsu Sparclite
18442 @kindex target sparclite
18443 @item target sparclite @var{dev}
18444 Fujitsu sparclite boards, used only for the purpose of loading.
18445 You must use an additional command to debug the program.
18446 For example: target remote @var{dev} using @value{GDBN} standard
18452 @subsection Zilog Z8000
18455 @cindex simulator, Z8000
18456 @cindex Zilog Z8000 simulator
18458 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18461 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18462 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18463 segmented variant). The simulator recognizes which architecture is
18464 appropriate by inspecting the object code.
18467 @item target sim @var{args}
18469 @kindex target sim@r{, with Z8000}
18470 Debug programs on a simulated CPU. If the simulator supports setup
18471 options, specify them via @var{args}.
18475 After specifying this target, you can debug programs for the simulated
18476 CPU in the same style as programs for your host computer; use the
18477 @code{file} command to load a new program image, the @code{run} command
18478 to run your program, and so on.
18480 As well as making available all the usual machine registers
18481 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18482 additional items of information as specially named registers:
18487 Counts clock-ticks in the simulator.
18490 Counts instructions run in the simulator.
18493 Execution time in 60ths of a second.
18497 You can refer to these values in @value{GDBN} expressions with the usual
18498 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18499 conditional breakpoint that suspends only after at least 5000
18500 simulated clock ticks.
18503 @subsection Atmel AVR
18506 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18507 following AVR-specific commands:
18510 @item info io_registers
18511 @kindex info io_registers@r{, AVR}
18512 @cindex I/O registers (Atmel AVR)
18513 This command displays information about the AVR I/O registers. For
18514 each register, @value{GDBN} prints its number and value.
18521 When configured for debugging CRIS, @value{GDBN} provides the
18522 following CRIS-specific commands:
18525 @item set cris-version @var{ver}
18526 @cindex CRIS version
18527 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18528 The CRIS version affects register names and sizes. This command is useful in
18529 case autodetection of the CRIS version fails.
18531 @item show cris-version
18532 Show the current CRIS version.
18534 @item set cris-dwarf2-cfi
18535 @cindex DWARF-2 CFI and CRIS
18536 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18537 Change to @samp{off} when using @code{gcc-cris} whose version is below
18540 @item show cris-dwarf2-cfi
18541 Show the current state of using DWARF-2 CFI.
18543 @item set cris-mode @var{mode}
18545 Set the current CRIS mode to @var{mode}. It should only be changed when
18546 debugging in guru mode, in which case it should be set to
18547 @samp{guru} (the default is @samp{normal}).
18549 @item show cris-mode
18550 Show the current CRIS mode.
18554 @subsection Renesas Super-H
18557 For the Renesas Super-H processor, @value{GDBN} provides these
18562 @kindex regs@r{, Super-H}
18563 Show the values of all Super-H registers.
18565 @item set sh calling-convention @var{convention}
18566 @kindex set sh calling-convention
18567 Set the calling-convention used when calling functions from @value{GDBN}.
18568 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18569 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18570 convention. If the DWARF-2 information of the called function specifies
18571 that the function follows the Renesas calling convention, the function
18572 is called using the Renesas calling convention. If the calling convention
18573 is set to @samp{renesas}, the Renesas calling convention is always used,
18574 regardless of the DWARF-2 information. This can be used to override the
18575 default of @samp{gcc} if debug information is missing, or the compiler
18576 does not emit the DWARF-2 calling convention entry for a function.
18578 @item show sh calling-convention
18579 @kindex show sh calling-convention
18580 Show the current calling convention setting.
18585 @node Architectures
18586 @section Architectures
18588 This section describes characteristics of architectures that affect
18589 all uses of @value{GDBN} with the architecture, both native and cross.
18596 * HPPA:: HP PA architecture
18597 * SPU:: Cell Broadband Engine SPU architecture
18602 @subsection x86 Architecture-specific Issues
18605 @item set struct-convention @var{mode}
18606 @kindex set struct-convention
18607 @cindex struct return convention
18608 @cindex struct/union returned in registers
18609 Set the convention used by the inferior to return @code{struct}s and
18610 @code{union}s from functions to @var{mode}. Possible values of
18611 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18612 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18613 are returned on the stack, while @code{"reg"} means that a
18614 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18615 be returned in a register.
18617 @item show struct-convention
18618 @kindex show struct-convention
18619 Show the current setting of the convention to return @code{struct}s
18628 @kindex set rstack_high_address
18629 @cindex AMD 29K register stack
18630 @cindex register stack, AMD29K
18631 @item set rstack_high_address @var{address}
18632 On AMD 29000 family processors, registers are saved in a separate
18633 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18634 extent of this stack. Normally, @value{GDBN} just assumes that the
18635 stack is ``large enough''. This may result in @value{GDBN} referencing
18636 memory locations that do not exist. If necessary, you can get around
18637 this problem by specifying the ending address of the register stack with
18638 the @code{set rstack_high_address} command. The argument should be an
18639 address, which you probably want to precede with @samp{0x} to specify in
18642 @kindex show rstack_high_address
18643 @item show rstack_high_address
18644 Display the current limit of the register stack, on AMD 29000 family
18652 See the following section.
18657 @cindex stack on Alpha
18658 @cindex stack on MIPS
18659 @cindex Alpha stack
18661 Alpha- and MIPS-based computers use an unusual stack frame, which
18662 sometimes requires @value{GDBN} to search backward in the object code to
18663 find the beginning of a function.
18665 @cindex response time, MIPS debugging
18666 To improve response time (especially for embedded applications, where
18667 @value{GDBN} may be restricted to a slow serial line for this search)
18668 you may want to limit the size of this search, using one of these
18672 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18673 @item set heuristic-fence-post @var{limit}
18674 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18675 search for the beginning of a function. A value of @var{0} (the
18676 default) means there is no limit. However, except for @var{0}, the
18677 larger the limit the more bytes @code{heuristic-fence-post} must search
18678 and therefore the longer it takes to run. You should only need to use
18679 this command when debugging a stripped executable.
18681 @item show heuristic-fence-post
18682 Display the current limit.
18686 These commands are available @emph{only} when @value{GDBN} is configured
18687 for debugging programs on Alpha or MIPS processors.
18689 Several MIPS-specific commands are available when debugging MIPS
18693 @item set mips abi @var{arg}
18694 @kindex set mips abi
18695 @cindex set ABI for MIPS
18696 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18697 values of @var{arg} are:
18701 The default ABI associated with the current binary (this is the
18712 @item show mips abi
18713 @kindex show mips abi
18714 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18717 @itemx show mipsfpu
18718 @xref{MIPS Embedded, set mipsfpu}.
18720 @item set mips mask-address @var{arg}
18721 @kindex set mips mask-address
18722 @cindex MIPS addresses, masking
18723 This command determines whether the most-significant 32 bits of 64-bit
18724 MIPS addresses are masked off. The argument @var{arg} can be
18725 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18726 setting, which lets @value{GDBN} determine the correct value.
18728 @item show mips mask-address
18729 @kindex show mips mask-address
18730 Show whether the upper 32 bits of MIPS addresses are masked off or
18733 @item set remote-mips64-transfers-32bit-regs
18734 @kindex set remote-mips64-transfers-32bit-regs
18735 This command controls compatibility with 64-bit MIPS targets that
18736 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18737 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18738 and 64 bits for other registers, set this option to @samp{on}.
18740 @item show remote-mips64-transfers-32bit-regs
18741 @kindex show remote-mips64-transfers-32bit-regs
18742 Show the current setting of compatibility with older MIPS 64 targets.
18744 @item set debug mips
18745 @kindex set debug mips
18746 This command turns on and off debugging messages for the MIPS-specific
18747 target code in @value{GDBN}.
18749 @item show debug mips
18750 @kindex show debug mips
18751 Show the current setting of MIPS debugging messages.
18757 @cindex HPPA support
18759 When @value{GDBN} is debugging the HP PA architecture, it provides the
18760 following special commands:
18763 @item set debug hppa
18764 @kindex set debug hppa
18765 This command determines whether HPPA architecture-specific debugging
18766 messages are to be displayed.
18768 @item show debug hppa
18769 Show whether HPPA debugging messages are displayed.
18771 @item maint print unwind @var{address}
18772 @kindex maint print unwind@r{, HPPA}
18773 This command displays the contents of the unwind table entry at the
18774 given @var{address}.
18780 @subsection Cell Broadband Engine SPU architecture
18781 @cindex Cell Broadband Engine
18784 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18785 it provides the following special commands:
18788 @item info spu event
18790 Display SPU event facility status. Shows current event mask
18791 and pending event status.
18793 @item info spu signal
18794 Display SPU signal notification facility status. Shows pending
18795 signal-control word and signal notification mode of both signal
18796 notification channels.
18798 @item info spu mailbox
18799 Display SPU mailbox facility status. Shows all pending entries,
18800 in order of processing, in each of the SPU Write Outbound,
18801 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18804 Display MFC DMA status. Shows all pending commands in the MFC
18805 DMA queue. For each entry, opcode, tag, class IDs, effective
18806 and local store addresses and transfer size are shown.
18808 @item info spu proxydma
18809 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18810 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18811 and local store addresses and transfer size are shown.
18815 When @value{GDBN} is debugging a combined PowerPC/SPU application
18816 on the Cell Broadband Engine, it provides in addition the following
18820 @item set spu stop-on-load @var{arg}
18822 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18823 will give control to the user when a new SPE thread enters its @code{main}
18824 function. The default is @code{off}.
18826 @item show spu stop-on-load
18828 Show whether to stop for new SPE threads.
18830 @item set spu auto-flush-cache @var{arg}
18831 Set whether to automatically flush the software-managed cache. When set to
18832 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18833 cache to be flushed whenever SPE execution stops. This provides a consistent
18834 view of PowerPC memory that is accessed via the cache. If an application
18835 does not use the software-managed cache, this option has no effect.
18837 @item show spu auto-flush-cache
18838 Show whether to automatically flush the software-managed cache.
18843 @subsection PowerPC
18844 @cindex PowerPC architecture
18846 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18847 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18848 numbers stored in the floating point registers. These values must be stored
18849 in two consecutive registers, always starting at an even register like
18850 @code{f0} or @code{f2}.
18852 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18853 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18854 @code{f2} and @code{f3} for @code{$dl1} and so on.
18856 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18857 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18860 @node Controlling GDB
18861 @chapter Controlling @value{GDBN}
18863 You can alter the way @value{GDBN} interacts with you by using the
18864 @code{set} command. For commands controlling how @value{GDBN} displays
18865 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18870 * Editing:: Command editing
18871 * Command History:: Command history
18872 * Screen Size:: Screen size
18873 * Numbers:: Numbers
18874 * ABI:: Configuring the current ABI
18875 * Messages/Warnings:: Optional warnings and messages
18876 * Debugging Output:: Optional messages about internal happenings
18877 * Other Misc Settings:: Other Miscellaneous Settings
18885 @value{GDBN} indicates its readiness to read a command by printing a string
18886 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18887 can change the prompt string with the @code{set prompt} command. For
18888 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18889 the prompt in one of the @value{GDBN} sessions so that you can always tell
18890 which one you are talking to.
18892 @emph{Note:} @code{set prompt} does not add a space for you after the
18893 prompt you set. This allows you to set a prompt which ends in a space
18894 or a prompt that does not.
18898 @item set prompt @var{newprompt}
18899 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18901 @kindex show prompt
18903 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18907 @section Command Editing
18909 @cindex command line editing
18911 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18912 @sc{gnu} library provides consistent behavior for programs which provide a
18913 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18914 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18915 substitution, and a storage and recall of command history across
18916 debugging sessions.
18918 You may control the behavior of command line editing in @value{GDBN} with the
18919 command @code{set}.
18922 @kindex set editing
18925 @itemx set editing on
18926 Enable command line editing (enabled by default).
18928 @item set editing off
18929 Disable command line editing.
18931 @kindex show editing
18933 Show whether command line editing is enabled.
18936 @xref{Command Line Editing}, for more details about the Readline
18937 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18938 encouraged to read that chapter.
18940 @node Command History
18941 @section Command History
18942 @cindex command history
18944 @value{GDBN} can keep track of the commands you type during your
18945 debugging sessions, so that you can be certain of precisely what
18946 happened. Use these commands to manage the @value{GDBN} command
18949 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18950 package, to provide the history facility. @xref{Using History
18951 Interactively}, for the detailed description of the History library.
18953 To issue a command to @value{GDBN} without affecting certain aspects of
18954 the state which is seen by users, prefix it with @samp{server }
18955 (@pxref{Server Prefix}). This
18956 means that this command will not affect the command history, nor will it
18957 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18958 pressed on a line by itself.
18960 @cindex @code{server}, command prefix
18961 The server prefix does not affect the recording of values into the value
18962 history; to print a value without recording it into the value history,
18963 use the @code{output} command instead of the @code{print} command.
18965 Here is the description of @value{GDBN} commands related to command
18969 @cindex history substitution
18970 @cindex history file
18971 @kindex set history filename
18972 @cindex @env{GDBHISTFILE}, environment variable
18973 @item set history filename @var{fname}
18974 Set the name of the @value{GDBN} command history file to @var{fname}.
18975 This is the file where @value{GDBN} reads an initial command history
18976 list, and where it writes the command history from this session when it
18977 exits. You can access this list through history expansion or through
18978 the history command editing characters listed below. This file defaults
18979 to the value of the environment variable @code{GDBHISTFILE}, or to
18980 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18983 @cindex save command history
18984 @kindex set history save
18985 @item set history save
18986 @itemx set history save on
18987 Record command history in a file, whose name may be specified with the
18988 @code{set history filename} command. By default, this option is disabled.
18990 @item set history save off
18991 Stop recording command history in a file.
18993 @cindex history size
18994 @kindex set history size
18995 @cindex @env{HISTSIZE}, environment variable
18996 @item set history size @var{size}
18997 Set the number of commands which @value{GDBN} keeps in its history list.
18998 This defaults to the value of the environment variable
18999 @code{HISTSIZE}, or to 256 if this variable is not set.
19002 History expansion assigns special meaning to the character @kbd{!}.
19003 @xref{Event Designators}, for more details.
19005 @cindex history expansion, turn on/off
19006 Since @kbd{!} is also the logical not operator in C, history expansion
19007 is off by default. If you decide to enable history expansion with the
19008 @code{set history expansion on} command, you may sometimes need to
19009 follow @kbd{!} (when it is used as logical not, in an expression) with
19010 a space or a tab to prevent it from being expanded. The readline
19011 history facilities do not attempt substitution on the strings
19012 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19014 The commands to control history expansion are:
19017 @item set history expansion on
19018 @itemx set history expansion
19019 @kindex set history expansion
19020 Enable history expansion. History expansion is off by default.
19022 @item set history expansion off
19023 Disable history expansion.
19026 @kindex show history
19028 @itemx show history filename
19029 @itemx show history save
19030 @itemx show history size
19031 @itemx show history expansion
19032 These commands display the state of the @value{GDBN} history parameters.
19033 @code{show history} by itself displays all four states.
19038 @kindex show commands
19039 @cindex show last commands
19040 @cindex display command history
19041 @item show commands
19042 Display the last ten commands in the command history.
19044 @item show commands @var{n}
19045 Print ten commands centered on command number @var{n}.
19047 @item show commands +
19048 Print ten commands just after the commands last printed.
19052 @section Screen Size
19053 @cindex size of screen
19054 @cindex pauses in output
19056 Certain commands to @value{GDBN} may produce large amounts of
19057 information output to the screen. To help you read all of it,
19058 @value{GDBN} pauses and asks you for input at the end of each page of
19059 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19060 to discard the remaining output. Also, the screen width setting
19061 determines when to wrap lines of output. Depending on what is being
19062 printed, @value{GDBN} tries to break the line at a readable place,
19063 rather than simply letting it overflow onto the following line.
19065 Normally @value{GDBN} knows the size of the screen from the terminal
19066 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19067 together with the value of the @code{TERM} environment variable and the
19068 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19069 you can override it with the @code{set height} and @code{set
19076 @kindex show height
19077 @item set height @var{lpp}
19079 @itemx set width @var{cpl}
19081 These @code{set} commands specify a screen height of @var{lpp} lines and
19082 a screen width of @var{cpl} characters. The associated @code{show}
19083 commands display the current settings.
19085 If you specify a height of zero lines, @value{GDBN} does not pause during
19086 output no matter how long the output is. This is useful if output is to a
19087 file or to an editor buffer.
19089 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19090 from wrapping its output.
19092 @item set pagination on
19093 @itemx set pagination off
19094 @kindex set pagination
19095 Turn the output pagination on or off; the default is on. Turning
19096 pagination off is the alternative to @code{set height 0}. Note that
19097 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19098 Options, -batch}) also automatically disables pagination.
19100 @item show pagination
19101 @kindex show pagination
19102 Show the current pagination mode.
19107 @cindex number representation
19108 @cindex entering numbers
19110 You can always enter numbers in octal, decimal, or hexadecimal in
19111 @value{GDBN} by the usual conventions: octal numbers begin with
19112 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19113 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19114 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19115 10; likewise, the default display for numbers---when no particular
19116 format is specified---is base 10. You can change the default base for
19117 both input and output with the commands described below.
19120 @kindex set input-radix
19121 @item set input-radix @var{base}
19122 Set the default base for numeric input. Supported choices
19123 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19124 specified either unambiguously or using the current input radix; for
19128 set input-radix 012
19129 set input-radix 10.
19130 set input-radix 0xa
19134 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19135 leaves the input radix unchanged, no matter what it was, since
19136 @samp{10}, being without any leading or trailing signs of its base, is
19137 interpreted in the current radix. Thus, if the current radix is 16,
19138 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19141 @kindex set output-radix
19142 @item set output-radix @var{base}
19143 Set the default base for numeric display. Supported choices
19144 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19145 specified either unambiguously or using the current input radix.
19147 @kindex show input-radix
19148 @item show input-radix
19149 Display the current default base for numeric input.
19151 @kindex show output-radix
19152 @item show output-radix
19153 Display the current default base for numeric display.
19155 @item set radix @r{[}@var{base}@r{]}
19159 These commands set and show the default base for both input and output
19160 of numbers. @code{set radix} sets the radix of input and output to
19161 the same base; without an argument, it resets the radix back to its
19162 default value of 10.
19167 @section Configuring the Current ABI
19169 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19170 application automatically. However, sometimes you need to override its
19171 conclusions. Use these commands to manage @value{GDBN}'s view of the
19178 One @value{GDBN} configuration can debug binaries for multiple operating
19179 system targets, either via remote debugging or native emulation.
19180 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19181 but you can override its conclusion using the @code{set osabi} command.
19182 One example where this is useful is in debugging of binaries which use
19183 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19184 not have the same identifying marks that the standard C library for your
19189 Show the OS ABI currently in use.
19192 With no argument, show the list of registered available OS ABI's.
19194 @item set osabi @var{abi}
19195 Set the current OS ABI to @var{abi}.
19198 @cindex float promotion
19200 Generally, the way that an argument of type @code{float} is passed to a
19201 function depends on whether the function is prototyped. For a prototyped
19202 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19203 according to the architecture's convention for @code{float}. For unprototyped
19204 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19205 @code{double} and then passed.
19207 Unfortunately, some forms of debug information do not reliably indicate whether
19208 a function is prototyped. If @value{GDBN} calls a function that is not marked
19209 as prototyped, it consults @kbd{set coerce-float-to-double}.
19212 @kindex set coerce-float-to-double
19213 @item set coerce-float-to-double
19214 @itemx set coerce-float-to-double on
19215 Arguments of type @code{float} will be promoted to @code{double} when passed
19216 to an unprototyped function. This is the default setting.
19218 @item set coerce-float-to-double off
19219 Arguments of type @code{float} will be passed directly to unprototyped
19222 @kindex show coerce-float-to-double
19223 @item show coerce-float-to-double
19224 Show the current setting of promoting @code{float} to @code{double}.
19228 @kindex show cp-abi
19229 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19230 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19231 used to build your application. @value{GDBN} only fully supports
19232 programs with a single C@t{++} ABI; if your program contains code using
19233 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19234 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19235 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19236 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19237 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19238 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19243 Show the C@t{++} ABI currently in use.
19246 With no argument, show the list of supported C@t{++} ABI's.
19248 @item set cp-abi @var{abi}
19249 @itemx set cp-abi auto
19250 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19253 @node Messages/Warnings
19254 @section Optional Warnings and Messages
19256 @cindex verbose operation
19257 @cindex optional warnings
19258 By default, @value{GDBN} is silent about its inner workings. If you are
19259 running on a slow machine, you may want to use the @code{set verbose}
19260 command. This makes @value{GDBN} tell you when it does a lengthy
19261 internal operation, so you will not think it has crashed.
19263 Currently, the messages controlled by @code{set verbose} are those
19264 which announce that the symbol table for a source file is being read;
19265 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19268 @kindex set verbose
19269 @item set verbose on
19270 Enables @value{GDBN} output of certain informational messages.
19272 @item set verbose off
19273 Disables @value{GDBN} output of certain informational messages.
19275 @kindex show verbose
19277 Displays whether @code{set verbose} is on or off.
19280 By default, if @value{GDBN} encounters bugs in the symbol table of an
19281 object file, it is silent; but if you are debugging a compiler, you may
19282 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19287 @kindex set complaints
19288 @item set complaints @var{limit}
19289 Permits @value{GDBN} to output @var{limit} complaints about each type of
19290 unusual symbols before becoming silent about the problem. Set
19291 @var{limit} to zero to suppress all complaints; set it to a large number
19292 to prevent complaints from being suppressed.
19294 @kindex show complaints
19295 @item show complaints
19296 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19300 @anchor{confirmation requests}
19301 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19302 lot of stupid questions to confirm certain commands. For example, if
19303 you try to run a program which is already running:
19307 The program being debugged has been started already.
19308 Start it from the beginning? (y or n)
19311 If you are willing to unflinchingly face the consequences of your own
19312 commands, you can disable this ``feature'':
19316 @kindex set confirm
19318 @cindex confirmation
19319 @cindex stupid questions
19320 @item set confirm off
19321 Disables confirmation requests. Note that running @value{GDBN} with
19322 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19323 automatically disables confirmation requests.
19325 @item set confirm on
19326 Enables confirmation requests (the default).
19328 @kindex show confirm
19330 Displays state of confirmation requests.
19334 @cindex command tracing
19335 If you need to debug user-defined commands or sourced files you may find it
19336 useful to enable @dfn{command tracing}. In this mode each command will be
19337 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19338 quantity denoting the call depth of each command.
19341 @kindex set trace-commands
19342 @cindex command scripts, debugging
19343 @item set trace-commands on
19344 Enable command tracing.
19345 @item set trace-commands off
19346 Disable command tracing.
19347 @item show trace-commands
19348 Display the current state of command tracing.
19351 @node Debugging Output
19352 @section Optional Messages about Internal Happenings
19353 @cindex optional debugging messages
19355 @value{GDBN} has commands that enable optional debugging messages from
19356 various @value{GDBN} subsystems; normally these commands are of
19357 interest to @value{GDBN} maintainers, or when reporting a bug. This
19358 section documents those commands.
19361 @kindex set exec-done-display
19362 @item set exec-done-display
19363 Turns on or off the notification of asynchronous commands'
19364 completion. When on, @value{GDBN} will print a message when an
19365 asynchronous command finishes its execution. The default is off.
19366 @kindex show exec-done-display
19367 @item show exec-done-display
19368 Displays the current setting of asynchronous command completion
19371 @cindex gdbarch debugging info
19372 @cindex architecture debugging info
19373 @item set debug arch
19374 Turns on or off display of gdbarch debugging info. The default is off
19376 @item show debug arch
19377 Displays the current state of displaying gdbarch debugging info.
19378 @item set debug aix-thread
19379 @cindex AIX threads
19380 Display debugging messages about inner workings of the AIX thread
19382 @item show debug aix-thread
19383 Show the current state of AIX thread debugging info display.
19384 @item set debug dwarf2-die
19385 @cindex DWARF2 DIEs
19386 Dump DWARF2 DIEs after they are read in.
19387 The value is the number of nesting levels to print.
19388 A value of zero turns off the display.
19389 @item show debug dwarf2-die
19390 Show the current state of DWARF2 DIE debugging.
19391 @item set debug displaced
19392 @cindex displaced stepping debugging info
19393 Turns on or off display of @value{GDBN} debugging info for the
19394 displaced stepping support. The default is off.
19395 @item show debug displaced
19396 Displays the current state of displaying @value{GDBN} debugging info
19397 related to displaced stepping.
19398 @item set debug event
19399 @cindex event debugging info
19400 Turns on or off display of @value{GDBN} event debugging info. The
19402 @item show debug event
19403 Displays the current state of displaying @value{GDBN} event debugging
19405 @item set debug expression
19406 @cindex expression debugging info
19407 Turns on or off display of debugging info about @value{GDBN}
19408 expression parsing. The default is off.
19409 @item show debug expression
19410 Displays the current state of displaying debugging info about
19411 @value{GDBN} expression parsing.
19412 @item set debug frame
19413 @cindex frame debugging info
19414 Turns on or off display of @value{GDBN} frame debugging info. The
19416 @item show debug frame
19417 Displays the current state of displaying @value{GDBN} frame debugging
19419 @item set debug gnu-nat
19420 @cindex @sc{gnu}/Hurd debug messages
19421 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19422 @item show debug gnu-nat
19423 Show the current state of @sc{gnu}/Hurd debugging messages.
19424 @item set debug infrun
19425 @cindex inferior debugging info
19426 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19427 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19428 for implementing operations such as single-stepping the inferior.
19429 @item show debug infrun
19430 Displays the current state of @value{GDBN} inferior debugging.
19431 @item set debug lin-lwp
19432 @cindex @sc{gnu}/Linux LWP debug messages
19433 @cindex Linux lightweight processes
19434 Turns on or off debugging messages from the Linux LWP debug support.
19435 @item show debug lin-lwp
19436 Show the current state of Linux LWP debugging messages.
19437 @item set debug lin-lwp-async
19438 @cindex @sc{gnu}/Linux LWP async debug messages
19439 @cindex Linux lightweight processes
19440 Turns on or off debugging messages from the Linux LWP async debug support.
19441 @item show debug lin-lwp-async
19442 Show the current state of Linux LWP async debugging messages.
19443 @item set debug observer
19444 @cindex observer debugging info
19445 Turns on or off display of @value{GDBN} observer debugging. This
19446 includes info such as the notification of observable events.
19447 @item show debug observer
19448 Displays the current state of observer debugging.
19449 @item set debug overload
19450 @cindex C@t{++} overload debugging info
19451 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19452 info. This includes info such as ranking of functions, etc. The default
19454 @item show debug overload
19455 Displays the current state of displaying @value{GDBN} C@t{++} overload
19457 @cindex expression parser, debugging info
19458 @cindex debug expression parser
19459 @item set debug parser
19460 Turns on or off the display of expression parser debugging output.
19461 Internally, this sets the @code{yydebug} variable in the expression
19462 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19463 details. The default is off.
19464 @item show debug parser
19465 Show the current state of expression parser debugging.
19466 @cindex packets, reporting on stdout
19467 @cindex serial connections, debugging
19468 @cindex debug remote protocol
19469 @cindex remote protocol debugging
19470 @cindex display remote packets
19471 @item set debug remote
19472 Turns on or off display of reports on all packets sent back and forth across
19473 the serial line to the remote machine. The info is printed on the
19474 @value{GDBN} standard output stream. The default is off.
19475 @item show debug remote
19476 Displays the state of display of remote packets.
19477 @item set debug serial
19478 Turns on or off display of @value{GDBN} serial debugging info. The
19480 @item show debug serial
19481 Displays the current state of displaying @value{GDBN} serial debugging
19483 @item set debug solib-frv
19484 @cindex FR-V shared-library debugging
19485 Turns on or off debugging messages for FR-V shared-library code.
19486 @item show debug solib-frv
19487 Display the current state of FR-V shared-library code debugging
19489 @item set debug target
19490 @cindex target debugging info
19491 Turns on or off display of @value{GDBN} target debugging info. This info
19492 includes what is going on at the target level of GDB, as it happens. The
19493 default is 0. Set it to 1 to track events, and to 2 to also track the
19494 value of large memory transfers. Changes to this flag do not take effect
19495 until the next time you connect to a target or use the @code{run} command.
19496 @item show debug target
19497 Displays the current state of displaying @value{GDBN} target debugging
19499 @item set debug timestamp
19500 @cindex timestampping debugging info
19501 Turns on or off display of timestamps with @value{GDBN} debugging info.
19502 When enabled, seconds and microseconds are displayed before each debugging
19504 @item show debug timestamp
19505 Displays the current state of displaying timestamps with @value{GDBN}
19507 @item set debugvarobj
19508 @cindex variable object debugging info
19509 Turns on or off display of @value{GDBN} variable object debugging
19510 info. The default is off.
19511 @item show debugvarobj
19512 Displays the current state of displaying @value{GDBN} variable object
19514 @item set debug xml
19515 @cindex XML parser debugging
19516 Turns on or off debugging messages for built-in XML parsers.
19517 @item show debug xml
19518 Displays the current state of XML debugging messages.
19521 @node Other Misc Settings
19522 @section Other Miscellaneous Settings
19523 @cindex miscellaneous settings
19526 @kindex set interactive-mode
19527 @item set interactive-mode
19528 If @code{on}, forces @value{GDBN} to operate interactively.
19529 If @code{off}, forces @value{GDBN} to operate non-interactively,
19530 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19531 based on whether the debugger was started in a terminal or not.
19533 In the vast majority of cases, the debugger should be able to guess
19534 correctly which mode should be used. But this setting can be useful
19535 in certain specific cases, such as running a MinGW @value{GDBN}
19536 inside a cygwin window.
19538 @kindex show interactive-mode
19539 @item show interactive-mode
19540 Displays whether the debugger is operating in interactive mode or not.
19543 @node Extending GDB
19544 @chapter Extending @value{GDBN}
19545 @cindex extending GDB
19547 @value{GDBN} provides two mechanisms for extension. The first is based
19548 on composition of @value{GDBN} commands, and the second is based on the
19549 Python scripting language.
19551 To facilitate the use of these extensions, @value{GDBN} is capable
19552 of evaluating the contents of a file. When doing so, @value{GDBN}
19553 can recognize which scripting language is being used by looking at
19554 the filename extension. Files with an unrecognized filename extension
19555 are always treated as a @value{GDBN} Command Files.
19556 @xref{Command Files,, Command files}.
19558 You can control how @value{GDBN} evaluates these files with the following
19562 @kindex set script-extension
19563 @kindex show script-extension
19564 @item set script-extension off
19565 All scripts are always evaluated as @value{GDBN} Command Files.
19567 @item set script-extension soft
19568 The debugger determines the scripting language based on filename
19569 extension. If this scripting language is supported, @value{GDBN}
19570 evaluates the script using that language. Otherwise, it evaluates
19571 the file as a @value{GDBN} Command File.
19573 @item set script-extension strict
19574 The debugger determines the scripting language based on filename
19575 extension, and evaluates the script using that language. If the
19576 language is not supported, then the evaluation fails.
19578 @item show script-extension
19579 Display the current value of the @code{script-extension} option.
19584 * Sequences:: Canned Sequences of Commands
19585 * Python:: Scripting @value{GDBN} using Python
19589 @section Canned Sequences of Commands
19591 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19592 Command Lists}), @value{GDBN} provides two ways to store sequences of
19593 commands for execution as a unit: user-defined commands and command
19597 * Define:: How to define your own commands
19598 * Hooks:: Hooks for user-defined commands
19599 * Command Files:: How to write scripts of commands to be stored in a file
19600 * Output:: Commands for controlled output
19604 @subsection User-defined Commands
19606 @cindex user-defined command
19607 @cindex arguments, to user-defined commands
19608 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19609 which you assign a new name as a command. This is done with the
19610 @code{define} command. User commands may accept up to 10 arguments
19611 separated by whitespace. Arguments are accessed within the user command
19612 via @code{$arg0@dots{}$arg9}. A trivial example:
19616 print $arg0 + $arg1 + $arg2
19621 To execute the command use:
19628 This defines the command @code{adder}, which prints the sum of
19629 its three arguments. Note the arguments are text substitutions, so they may
19630 reference variables, use complex expressions, or even perform inferior
19633 @cindex argument count in user-defined commands
19634 @cindex how many arguments (user-defined commands)
19635 In addition, @code{$argc} may be used to find out how many arguments have
19636 been passed. This expands to a number in the range 0@dots{}10.
19641 print $arg0 + $arg1
19644 print $arg0 + $arg1 + $arg2
19652 @item define @var{commandname}
19653 Define a command named @var{commandname}. If there is already a command
19654 by that name, you are asked to confirm that you want to redefine it.
19655 @var{commandname} may be a bare command name consisting of letters,
19656 numbers, dashes, and underscores. It may also start with any predefined
19657 prefix command. For example, @samp{define target my-target} creates
19658 a user-defined @samp{target my-target} command.
19660 The definition of the command is made up of other @value{GDBN} command lines,
19661 which are given following the @code{define} command. The end of these
19662 commands is marked by a line containing @code{end}.
19665 @kindex end@r{ (user-defined commands)}
19666 @item document @var{commandname}
19667 Document the user-defined command @var{commandname}, so that it can be
19668 accessed by @code{help}. The command @var{commandname} must already be
19669 defined. This command reads lines of documentation just as @code{define}
19670 reads the lines of the command definition, ending with @code{end}.
19671 After the @code{document} command is finished, @code{help} on command
19672 @var{commandname} displays the documentation you have written.
19674 You may use the @code{document} command again to change the
19675 documentation of a command. Redefining the command with @code{define}
19676 does not change the documentation.
19678 @kindex dont-repeat
19679 @cindex don't repeat command
19681 Used inside a user-defined command, this tells @value{GDBN} that this
19682 command should not be repeated when the user hits @key{RET}
19683 (@pxref{Command Syntax, repeat last command}).
19685 @kindex help user-defined
19686 @item help user-defined
19687 List all user-defined commands, with the first line of the documentation
19692 @itemx show user @var{commandname}
19693 Display the @value{GDBN} commands used to define @var{commandname} (but
19694 not its documentation). If no @var{commandname} is given, display the
19695 definitions for all user-defined commands.
19697 @cindex infinite recursion in user-defined commands
19698 @kindex show max-user-call-depth
19699 @kindex set max-user-call-depth
19700 @item show max-user-call-depth
19701 @itemx set max-user-call-depth
19702 The value of @code{max-user-call-depth} controls how many recursion
19703 levels are allowed in user-defined commands before @value{GDBN} suspects an
19704 infinite recursion and aborts the command.
19707 In addition to the above commands, user-defined commands frequently
19708 use control flow commands, described in @ref{Command Files}.
19710 When user-defined commands are executed, the
19711 commands of the definition are not printed. An error in any command
19712 stops execution of the user-defined command.
19714 If used interactively, commands that would ask for confirmation proceed
19715 without asking when used inside a user-defined command. Many @value{GDBN}
19716 commands that normally print messages to say what they are doing omit the
19717 messages when used in a user-defined command.
19720 @subsection User-defined Command Hooks
19721 @cindex command hooks
19722 @cindex hooks, for commands
19723 @cindex hooks, pre-command
19726 You may define @dfn{hooks}, which are a special kind of user-defined
19727 command. Whenever you run the command @samp{foo}, if the user-defined
19728 command @samp{hook-foo} exists, it is executed (with no arguments)
19729 before that command.
19731 @cindex hooks, post-command
19733 A hook may also be defined which is run after the command you executed.
19734 Whenever you run the command @samp{foo}, if the user-defined command
19735 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19736 that command. Post-execution hooks may exist simultaneously with
19737 pre-execution hooks, for the same command.
19739 It is valid for a hook to call the command which it hooks. If this
19740 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19742 @c It would be nice if hookpost could be passed a parameter indicating
19743 @c if the command it hooks executed properly or not. FIXME!
19745 @kindex stop@r{, a pseudo-command}
19746 In addition, a pseudo-command, @samp{stop} exists. Defining
19747 (@samp{hook-stop}) makes the associated commands execute every time
19748 execution stops in your program: before breakpoint commands are run,
19749 displays are printed, or the stack frame is printed.
19751 For example, to ignore @code{SIGALRM} signals while
19752 single-stepping, but treat them normally during normal execution,
19757 handle SIGALRM nopass
19761 handle SIGALRM pass
19764 define hook-continue
19765 handle SIGALRM pass
19769 As a further example, to hook at the beginning and end of the @code{echo}
19770 command, and to add extra text to the beginning and end of the message,
19778 define hookpost-echo
19782 (@value{GDBP}) echo Hello World
19783 <<<---Hello World--->>>
19788 You can define a hook for any single-word command in @value{GDBN}, but
19789 not for command aliases; you should define a hook for the basic command
19790 name, e.g.@: @code{backtrace} rather than @code{bt}.
19791 @c FIXME! So how does Joe User discover whether a command is an alias
19793 You can hook a multi-word command by adding @code{hook-} or
19794 @code{hookpost-} to the last word of the command, e.g.@:
19795 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19797 If an error occurs during the execution of your hook, execution of
19798 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19799 (before the command that you actually typed had a chance to run).
19801 If you try to define a hook which does not match any known command, you
19802 get a warning from the @code{define} command.
19804 @node Command Files
19805 @subsection Command Files
19807 @cindex command files
19808 @cindex scripting commands
19809 A command file for @value{GDBN} is a text file made of lines that are
19810 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19811 also be included. An empty line in a command file does nothing; it
19812 does not mean to repeat the last command, as it would from the
19815 You can request the execution of a command file with the @code{source}
19816 command. Note that the @code{source} command is also used to evaluate
19817 scripts that are not Command Files. The exact behavior can be configured
19818 using the @code{script-extension} setting.
19819 @xref{Extending GDB,, Extending GDB}.
19823 @cindex execute commands from a file
19824 @item source [-s] [-v] @var{filename}
19825 Execute the command file @var{filename}.
19828 The lines in a command file are generally executed sequentially,
19829 unless the order of execution is changed by one of the
19830 @emph{flow-control commands} described below. The commands are not
19831 printed as they are executed. An error in any command terminates
19832 execution of the command file and control is returned to the console.
19834 @value{GDBN} first searches for @var{filename} in the current directory.
19835 If the file is not found there, and @var{filename} does not specify a
19836 directory, then @value{GDBN} also looks for the file on the source search path
19837 (specified with the @samp{directory} command);
19838 except that @file{$cdir} is not searched because the compilation directory
19839 is not relevant to scripts.
19841 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19842 on the search path even if @var{filename} specifies a directory.
19843 The search is done by appending @var{filename} to each element of the
19844 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19845 and the search path contains @file{/home/user} then @value{GDBN} will
19846 look for the script @file{/home/user/mylib/myscript}.
19847 The search is also done if @var{filename} is an absolute path.
19848 For example, if @var{filename} is @file{/tmp/myscript} and
19849 the search path contains @file{/home/user} then @value{GDBN} will
19850 look for the script @file{/home/user/tmp/myscript}.
19851 For DOS-like systems, if @var{filename} contains a drive specification,
19852 it is stripped before concatenation. For example, if @var{filename} is
19853 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19854 will look for the script @file{c:/tmp/myscript}.
19856 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19857 each command as it is executed. The option must be given before
19858 @var{filename}, and is interpreted as part of the filename anywhere else.
19860 Commands that would ask for confirmation if used interactively proceed
19861 without asking when used in a command file. Many @value{GDBN} commands that
19862 normally print messages to say what they are doing omit the messages
19863 when called from command files.
19865 @value{GDBN} also accepts command input from standard input. In this
19866 mode, normal output goes to standard output and error output goes to
19867 standard error. Errors in a command file supplied on standard input do
19868 not terminate execution of the command file---execution continues with
19872 gdb < cmds > log 2>&1
19875 (The syntax above will vary depending on the shell used.) This example
19876 will execute commands from the file @file{cmds}. All output and errors
19877 would be directed to @file{log}.
19879 Since commands stored on command files tend to be more general than
19880 commands typed interactively, they frequently need to deal with
19881 complicated situations, such as different or unexpected values of
19882 variables and symbols, changes in how the program being debugged is
19883 built, etc. @value{GDBN} provides a set of flow-control commands to
19884 deal with these complexities. Using these commands, you can write
19885 complex scripts that loop over data structures, execute commands
19886 conditionally, etc.
19893 This command allows to include in your script conditionally executed
19894 commands. The @code{if} command takes a single argument, which is an
19895 expression to evaluate. It is followed by a series of commands that
19896 are executed only if the expression is true (its value is nonzero).
19897 There can then optionally be an @code{else} line, followed by a series
19898 of commands that are only executed if the expression was false. The
19899 end of the list is marked by a line containing @code{end}.
19903 This command allows to write loops. Its syntax is similar to
19904 @code{if}: the command takes a single argument, which is an expression
19905 to evaluate, and must be followed by the commands to execute, one per
19906 line, terminated by an @code{end}. These commands are called the
19907 @dfn{body} of the loop. The commands in the body of @code{while} are
19908 executed repeatedly as long as the expression evaluates to true.
19912 This command exits the @code{while} loop in whose body it is included.
19913 Execution of the script continues after that @code{while}s @code{end}
19916 @kindex loop_continue
19917 @item loop_continue
19918 This command skips the execution of the rest of the body of commands
19919 in the @code{while} loop in whose body it is included. Execution
19920 branches to the beginning of the @code{while} loop, where it evaluates
19921 the controlling expression.
19923 @kindex end@r{ (if/else/while commands)}
19925 Terminate the block of commands that are the body of @code{if},
19926 @code{else}, or @code{while} flow-control commands.
19931 @subsection Commands for Controlled Output
19933 During the execution of a command file or a user-defined command, normal
19934 @value{GDBN} output is suppressed; the only output that appears is what is
19935 explicitly printed by the commands in the definition. This section
19936 describes three commands useful for generating exactly the output you
19941 @item echo @var{text}
19942 @c I do not consider backslash-space a standard C escape sequence
19943 @c because it is not in ANSI.
19944 Print @var{text}. Nonprinting characters can be included in
19945 @var{text} using C escape sequences, such as @samp{\n} to print a
19946 newline. @strong{No newline is printed unless you specify one.}
19947 In addition to the standard C escape sequences, a backslash followed
19948 by a space stands for a space. This is useful for displaying a
19949 string with spaces at the beginning or the end, since leading and
19950 trailing spaces are otherwise trimmed from all arguments.
19951 To print @samp{@w{ }and foo =@w{ }}, use the command
19952 @samp{echo \@w{ }and foo = \@w{ }}.
19954 A backslash at the end of @var{text} can be used, as in C, to continue
19955 the command onto subsequent lines. For example,
19958 echo This is some text\n\
19959 which is continued\n\
19960 onto several lines.\n
19963 produces the same output as
19966 echo This is some text\n
19967 echo which is continued\n
19968 echo onto several lines.\n
19972 @item output @var{expression}
19973 Print the value of @var{expression} and nothing but that value: no
19974 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19975 value history either. @xref{Expressions, ,Expressions}, for more information
19978 @item output/@var{fmt} @var{expression}
19979 Print the value of @var{expression} in format @var{fmt}. You can use
19980 the same formats as for @code{print}. @xref{Output Formats,,Output
19981 Formats}, for more information.
19984 @item printf @var{template}, @var{expressions}@dots{}
19985 Print the values of one or more @var{expressions} under the control of
19986 the string @var{template}. To print several values, make
19987 @var{expressions} be a comma-separated list of individual expressions,
19988 which may be either numbers or pointers. Their values are printed as
19989 specified by @var{template}, exactly as a C program would do by
19990 executing the code below:
19993 printf (@var{template}, @var{expressions}@dots{});
19996 As in @code{C} @code{printf}, ordinary characters in @var{template}
19997 are printed verbatim, while @dfn{conversion specification} introduced
19998 by the @samp{%} character cause subsequent @var{expressions} to be
19999 evaluated, their values converted and formatted according to type and
20000 style information encoded in the conversion specifications, and then
20003 For example, you can print two values in hex like this:
20006 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20009 @code{printf} supports all the standard @code{C} conversion
20010 specifications, including the flags and modifiers between the @samp{%}
20011 character and the conversion letter, with the following exceptions:
20015 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20018 The modifier @samp{*} is not supported for specifying precision or
20022 The @samp{'} flag (for separation of digits into groups according to
20023 @code{LC_NUMERIC'}) is not supported.
20026 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20030 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20033 The conversion letters @samp{a} and @samp{A} are not supported.
20037 Note that the @samp{ll} type modifier is supported only if the
20038 underlying @code{C} implementation used to build @value{GDBN} supports
20039 the @code{long long int} type, and the @samp{L} type modifier is
20040 supported only if @code{long double} type is available.
20042 As in @code{C}, @code{printf} supports simple backslash-escape
20043 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20044 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20045 single character. Octal and hexadecimal escape sequences are not
20048 Additionally, @code{printf} supports conversion specifications for DFP
20049 (@dfn{Decimal Floating Point}) types using the following length modifiers
20050 together with a floating point specifier.
20055 @samp{H} for printing @code{Decimal32} types.
20058 @samp{D} for printing @code{Decimal64} types.
20061 @samp{DD} for printing @code{Decimal128} types.
20064 If the underlying @code{C} implementation used to build @value{GDBN} has
20065 support for the three length modifiers for DFP types, other modifiers
20066 such as width and precision will also be available for @value{GDBN} to use.
20068 In case there is no such @code{C} support, no additional modifiers will be
20069 available and the value will be printed in the standard way.
20071 Here's an example of printing DFP types using the above conversion letters:
20073 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20077 @item eval @var{template}, @var{expressions}@dots{}
20078 Convert the values of one or more @var{expressions} under the control of
20079 the string @var{template} to a command line, and call it.
20084 @section Scripting @value{GDBN} using Python
20085 @cindex python scripting
20086 @cindex scripting with python
20088 You can script @value{GDBN} using the @uref{http://www.python.org/,
20089 Python programming language}. This feature is available only if
20090 @value{GDBN} was configured using @option{--with-python}.
20092 @cindex python directory
20093 Python scripts used by @value{GDBN} should be installed in
20094 @file{@var{data-directory}/python}, where @var{data-directory} is
20095 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20096 is automatically added to the Python Search Path in order to allow
20097 the Python interpreter to locate all scripts installed at this location.
20100 * Python Commands:: Accessing Python from @value{GDBN}.
20101 * Python API:: Accessing @value{GDBN} from Python.
20102 * Auto-loading:: Automatically loading Python code.
20105 @node Python Commands
20106 @subsection Python Commands
20107 @cindex python commands
20108 @cindex commands to access python
20110 @value{GDBN} provides one command for accessing the Python interpreter,
20111 and one related setting:
20115 @item python @r{[}@var{code}@r{]}
20116 The @code{python} command can be used to evaluate Python code.
20118 If given an argument, the @code{python} command will evaluate the
20119 argument as a Python command. For example:
20122 (@value{GDBP}) python print 23
20126 If you do not provide an argument to @code{python}, it will act as a
20127 multi-line command, like @code{define}. In this case, the Python
20128 script is made up of subsequent command lines, given after the
20129 @code{python} command. This command list is terminated using a line
20130 containing @code{end}. For example:
20133 (@value{GDBP}) python
20135 End with a line saying just "end".
20141 @kindex maint set python print-stack
20142 @item maint set python print-stack
20143 By default, @value{GDBN} will print a stack trace when an error occurs
20144 in a Python script. This can be controlled using @code{maint set
20145 python print-stack}: if @code{on}, the default, then Python stack
20146 printing is enabled; if @code{off}, then Python stack printing is
20150 It is also possible to execute a Python script from the @value{GDBN}
20154 @item source @file{script-name}
20155 The script name must end with @samp{.py} and @value{GDBN} must be configured
20156 to recognize the script language based on filename extension using
20157 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20159 @item python execfile ("script-name")
20160 This method is based on the @code{execfile} Python built-in function,
20161 and thus is always available.
20165 @subsection Python API
20167 @cindex programming in python
20169 @cindex python stdout
20170 @cindex python pagination
20171 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20172 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20173 A Python program which outputs to one of these streams may have its
20174 output interrupted by the user (@pxref{Screen Size}). In this
20175 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20178 * Basic Python:: Basic Python Functions.
20179 * Exception Handling::
20180 * Values From Inferior::
20181 * Types In Python:: Python representation of types.
20182 * Pretty Printing API:: Pretty-printing values.
20183 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20184 * Disabling Pretty-Printers:: Disabling broken printers.
20185 * Inferiors In Python:: Python representation of inferiors (processes)
20186 * Threads In Python:: Accessing inferior threads from Python.
20187 * Commands In Python:: Implementing new commands in Python.
20188 * Parameters In Python:: Adding new @value{GDBN} parameters.
20189 * Functions In Python:: Writing new convenience functions.
20190 * Progspaces In Python:: Program spaces.
20191 * Objfiles In Python:: Object files.
20192 * Frames In Python:: Accessing inferior stack frames from Python.
20193 * Blocks In Python:: Accessing frame blocks from Python.
20194 * Symbols In Python:: Python representation of symbols.
20195 * Symbol Tables In Python:: Python representation of symbol tables.
20196 * Lazy Strings In Python:: Python representation of lazy strings.
20197 * Breakpoints In Python:: Manipulating breakpoints using Python.
20201 @subsubsection Basic Python
20203 @cindex python functions
20204 @cindex python module
20206 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20207 methods and classes added by @value{GDBN} are placed in this module.
20208 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20209 use in all scripts evaluated by the @code{python} command.
20211 @findex gdb.PYTHONDIR
20213 A string containing the python directory (@pxref{Python}).
20216 @findex gdb.execute
20217 @defun execute command [from_tty] [to_string]
20218 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20219 If a GDB exception happens while @var{command} runs, it is
20220 translated as described in @ref{Exception Handling,,Exception Handling}.
20222 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20223 command as having originated from the user invoking it interactively.
20224 It must be a boolean value. If omitted, it defaults to @code{False}.
20226 By default, any output produced by @var{command} is sent to
20227 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20228 @code{True}, then output will be collected by @code{gdb.execute} and
20229 returned as a string. The default is @code{False}, in which case the
20230 return value is @code{None}.
20233 @findex gdb.breakpoints
20235 Return a sequence holding all of @value{GDBN}'s breakpoints.
20236 @xref{Breakpoints In Python}, for more information.
20239 @findex gdb.parameter
20240 @defun parameter parameter
20241 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20242 string naming the parameter to look up; @var{parameter} may contain
20243 spaces if the parameter has a multi-part name. For example,
20244 @samp{print object} is a valid parameter name.
20246 If the named parameter does not exist, this function throws a
20247 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20248 a Python value of the appropriate type, and returned.
20251 @findex gdb.history
20252 @defun history number
20253 Return a value from @value{GDBN}'s value history (@pxref{Value
20254 History}). @var{number} indicates which history element to return.
20255 If @var{number} is negative, then @value{GDBN} will take its absolute value
20256 and count backward from the last element (i.e., the most recent element) to
20257 find the value to return. If @var{number} is zero, then @value{GDBN} will
20258 return the most recent element. If the element specified by @var{number}
20259 doesn't exist in the value history, a @code{RuntimeError} exception will be
20262 If no exception is raised, the return value is always an instance of
20263 @code{gdb.Value} (@pxref{Values From Inferior}).
20266 @findex gdb.parse_and_eval
20267 @defun parse_and_eval expression
20268 Parse @var{expression} as an expression in the current language,
20269 evaluate it, and return the result as a @code{gdb.Value}.
20270 @var{expression} must be a string.
20272 This function can be useful when implementing a new command
20273 (@pxref{Commands In Python}), as it provides a way to parse the
20274 command's argument as an expression. It is also useful simply to
20275 compute values, for example, it is the only way to get the value of a
20276 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20280 @defun write string
20281 Print a string to @value{GDBN}'s paginated standard output stream.
20282 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20283 call this function.
20288 Flush @value{GDBN}'s paginated standard output stream. Flushing
20289 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20293 @findex gdb.target_charset
20294 @defun target_charset
20295 Return the name of the current target character set (@pxref{Character
20296 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20297 that @samp{auto} is never returned.
20300 @findex gdb.target_wide_charset
20301 @defun target_wide_charset
20302 Return the name of the current target wide character set
20303 (@pxref{Character Sets}). This differs from
20304 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20308 @node Exception Handling
20309 @subsubsection Exception Handling
20310 @cindex python exceptions
20311 @cindex exceptions, python
20313 When executing the @code{python} command, Python exceptions
20314 uncaught within the Python code are translated to calls to
20315 @value{GDBN} error-reporting mechanism. If the command that called
20316 @code{python} does not handle the error, @value{GDBN} will
20317 terminate it and print an error message containing the Python
20318 exception name, the associated value, and the Python call stack
20319 backtrace at the point where the exception was raised. Example:
20322 (@value{GDBP}) python print foo
20323 Traceback (most recent call last):
20324 File "<string>", line 1, in <module>
20325 NameError: name 'foo' is not defined
20328 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20329 code are converted to Python @code{RuntimeError} exceptions. User
20330 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20331 prompt) is translated to a Python @code{KeyboardInterrupt}
20332 exception. If you catch these exceptions in your Python code, your
20333 exception handler will see @code{RuntimeError} or
20334 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20335 message as its value, and the Python call stack backtrace at the
20336 Python statement closest to where the @value{GDBN} error occured as the
20339 @findex gdb.GdbError
20340 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20341 it is useful to be able to throw an exception that doesn't cause a
20342 traceback to be printed. For example, the user may have invoked the
20343 command incorrectly. Use the @code{gdb.GdbError} exception
20344 to handle this case. Example:
20348 >class HelloWorld (gdb.Command):
20349 > """Greet the whole world."""
20350 > def __init__ (self):
20351 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20352 > def invoke (self, args, from_tty):
20353 > argv = gdb.string_to_argv (args)
20354 > if len (argv) != 0:
20355 > raise gdb.GdbError ("hello-world takes no arguments")
20356 > print "Hello, World!"
20359 (gdb) hello-world 42
20360 hello-world takes no arguments
20363 @node Values From Inferior
20364 @subsubsection Values From Inferior
20365 @cindex values from inferior, with Python
20366 @cindex python, working with values from inferior
20368 @cindex @code{gdb.Value}
20369 @value{GDBN} provides values it obtains from the inferior program in
20370 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20371 for its internal bookkeeping of the inferior's values, and for
20372 fetching values when necessary.
20374 Inferior values that are simple scalars can be used directly in
20375 Python expressions that are valid for the value's data type. Here's
20376 an example for an integer or floating-point value @code{some_val}:
20383 As result of this, @code{bar} will also be a @code{gdb.Value} object
20384 whose values are of the same type as those of @code{some_val}.
20386 Inferior values that are structures or instances of some class can
20387 be accessed using the Python @dfn{dictionary syntax}. For example, if
20388 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20389 can access its @code{foo} element with:
20392 bar = some_val['foo']
20395 Again, @code{bar} will also be a @code{gdb.Value} object.
20397 The following attributes are provided:
20400 @defivar Value address
20401 If this object is addressable, this read-only attribute holds a
20402 @code{gdb.Value} object representing the address. Otherwise,
20403 this attribute holds @code{None}.
20406 @cindex optimized out value in Python
20407 @defivar Value is_optimized_out
20408 This read-only boolean attribute is true if the compiler optimized out
20409 this value, thus it is not available for fetching from the inferior.
20412 @defivar Value type
20413 The type of this @code{gdb.Value}. The value of this attribute is a
20414 @code{gdb.Type} object.
20418 The following methods are provided:
20421 @defmethod Value cast type
20422 Return a new instance of @code{gdb.Value} that is the result of
20423 casting this instance to the type described by @var{type}, which must
20424 be a @code{gdb.Type} object. If the cast cannot be performed for some
20425 reason, this method throws an exception.
20428 @defmethod Value dereference
20429 For pointer data types, this method returns a new @code{gdb.Value} object
20430 whose contents is the object pointed to by the pointer. For example, if
20431 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20438 then you can use the corresponding @code{gdb.Value} to access what
20439 @code{foo} points to like this:
20442 bar = foo.dereference ()
20445 The result @code{bar} will be a @code{gdb.Value} object holding the
20446 value pointed to by @code{foo}.
20449 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20450 If this @code{gdb.Value} represents a string, then this method
20451 converts the contents to a Python string. Otherwise, this method will
20452 throw an exception.
20454 Strings are recognized in a language-specific way; whether a given
20455 @code{gdb.Value} represents a string is determined by the current
20458 For C-like languages, a value is a string if it is a pointer to or an
20459 array of characters or ints. The string is assumed to be terminated
20460 by a zero of the appropriate width. However if the optional length
20461 argument is given, the string will be converted to that given length,
20462 ignoring any embedded zeros that the string may contain.
20464 If the optional @var{encoding} argument is given, it must be a string
20465 naming the encoding of the string in the @code{gdb.Value}, such as
20466 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20467 the same encodings as the corresponding argument to Python's
20468 @code{string.decode} method, and the Python codec machinery will be used
20469 to convert the string. If @var{encoding} is not given, or if
20470 @var{encoding} is the empty string, then either the @code{target-charset}
20471 (@pxref{Character Sets}) will be used, or a language-specific encoding
20472 will be used, if the current language is able to supply one.
20474 The optional @var{errors} argument is the same as the corresponding
20475 argument to Python's @code{string.decode} method.
20477 If the optional @var{length} argument is given, the string will be
20478 fetched and converted to the given length.
20481 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20482 If this @code{gdb.Value} represents a string, then this method
20483 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20484 In Python}). Otherwise, this method will throw an exception.
20486 If the optional @var{encoding} argument is given, it must be a string
20487 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20488 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20489 @var{encoding} argument is an encoding that @value{GDBN} does
20490 recognize, @value{GDBN} will raise an error.
20492 When a lazy string is printed, the @value{GDBN} encoding machinery is
20493 used to convert the string during printing. If the optional
20494 @var{encoding} argument is not provided, or is an empty string,
20495 @value{GDBN} will automatically select the encoding most suitable for
20496 the string type. For further information on encoding in @value{GDBN}
20497 please see @ref{Character Sets}.
20499 If the optional @var{length} argument is given, the string will be
20500 fetched and encoded to the length of characters specified. If
20501 the @var{length} argument is not provided, the string will be fetched
20502 and encoded until a null of appropriate width is found.
20506 @node Types In Python
20507 @subsubsection Types In Python
20508 @cindex types in Python
20509 @cindex Python, working with types
20512 @value{GDBN} represents types from the inferior using the class
20515 The following type-related functions are available in the @code{gdb}
20518 @findex gdb.lookup_type
20519 @defun lookup_type name [block]
20520 This function looks up a type by name. @var{name} is the name of the
20521 type to look up. It must be a string.
20523 If @var{block} is given, then @var{name} is looked up in that scope.
20524 Otherwise, it is searched for globally.
20526 Ordinarily, this function will return an instance of @code{gdb.Type}.
20527 If the named type cannot be found, it will throw an exception.
20530 An instance of @code{Type} has the following attributes:
20534 The type code for this type. The type code will be one of the
20535 @code{TYPE_CODE_} constants defined below.
20538 @defivar Type sizeof
20539 The size of this type, in target @code{char} units. Usually, a
20540 target's @code{char} type will be an 8-bit byte. However, on some
20541 unusual platforms, this type may have a different size.
20545 The tag name for this type. The tag name is the name after
20546 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20547 languages have this concept. If this type has no tag name, then
20548 @code{None} is returned.
20552 The following methods are provided:
20555 @defmethod Type fields
20556 For structure and union types, this method returns the fields. Range
20557 types have two fields, the minimum and maximum values. Enum types
20558 have one field per enum constant. Function and method types have one
20559 field per parameter. The base types of C@t{++} classes are also
20560 represented as fields. If the type has no fields, or does not fit
20561 into one of these categories, an empty sequence will be returned.
20563 Each field is an object, with some pre-defined attributes:
20566 This attribute is not available for @code{static} fields (as in
20567 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20568 position of the field.
20571 The name of the field, or @code{None} for anonymous fields.
20574 This is @code{True} if the field is artificial, usually meaning that
20575 it was provided by the compiler and not the user. This attribute is
20576 always provided, and is @code{False} if the field is not artificial.
20578 @item is_base_class
20579 This is @code{True} if the field represents a base class of a C@t{++}
20580 structure. This attribute is always provided, and is @code{False}
20581 if the field is not a base class of the type that is the argument of
20582 @code{fields}, or if that type was not a C@t{++} class.
20585 If the field is packed, or is a bitfield, then this will have a
20586 non-zero value, which is the size of the field in bits. Otherwise,
20587 this will be zero; in this case the field's size is given by its type.
20590 The type of the field. This is usually an instance of @code{Type},
20591 but it can be @code{None} in some situations.
20595 @defmethod Type const
20596 Return a new @code{gdb.Type} object which represents a
20597 @code{const}-qualified variant of this type.
20600 @defmethod Type volatile
20601 Return a new @code{gdb.Type} object which represents a
20602 @code{volatile}-qualified variant of this type.
20605 @defmethod Type unqualified
20606 Return a new @code{gdb.Type} object which represents an unqualified
20607 variant of this type. That is, the result is neither @code{const} nor
20611 @defmethod Type range
20612 Return a Python @code{Tuple} object that contains two elements: the
20613 low bound of the argument type and the high bound of that type. If
20614 the type does not have a range, @value{GDBN} will raise a
20615 @code{RuntimeError} exception.
20618 @defmethod Type reference
20619 Return a new @code{gdb.Type} object which represents a reference to this
20623 @defmethod Type pointer
20624 Return a new @code{gdb.Type} object which represents a pointer to this
20628 @defmethod Type strip_typedefs
20629 Return a new @code{gdb.Type} that represents the real type,
20630 after removing all layers of typedefs.
20633 @defmethod Type target
20634 Return a new @code{gdb.Type} object which represents the target type
20637 For a pointer type, the target type is the type of the pointed-to
20638 object. For an array type (meaning C-like arrays), the target type is
20639 the type of the elements of the array. For a function or method type,
20640 the target type is the type of the return value. For a complex type,
20641 the target type is the type of the elements. For a typedef, the
20642 target type is the aliased type.
20644 If the type does not have a target, this method will throw an
20648 @defmethod Type template_argument n [block]
20649 If this @code{gdb.Type} is an instantiation of a template, this will
20650 return a new @code{gdb.Type} which represents the type of the
20651 @var{n}th template argument.
20653 If this @code{gdb.Type} is not a template type, this will throw an
20654 exception. Ordinarily, only C@t{++} code will have template types.
20656 If @var{block} is given, then @var{name} is looked up in that scope.
20657 Otherwise, it is searched for globally.
20662 Each type has a code, which indicates what category this type falls
20663 into. The available type categories are represented by constants
20664 defined in the @code{gdb} module:
20667 @findex TYPE_CODE_PTR
20668 @findex gdb.TYPE_CODE_PTR
20669 @item TYPE_CODE_PTR
20670 The type is a pointer.
20672 @findex TYPE_CODE_ARRAY
20673 @findex gdb.TYPE_CODE_ARRAY
20674 @item TYPE_CODE_ARRAY
20675 The type is an array.
20677 @findex TYPE_CODE_STRUCT
20678 @findex gdb.TYPE_CODE_STRUCT
20679 @item TYPE_CODE_STRUCT
20680 The type is a structure.
20682 @findex TYPE_CODE_UNION
20683 @findex gdb.TYPE_CODE_UNION
20684 @item TYPE_CODE_UNION
20685 The type is a union.
20687 @findex TYPE_CODE_ENUM
20688 @findex gdb.TYPE_CODE_ENUM
20689 @item TYPE_CODE_ENUM
20690 The type is an enum.
20692 @findex TYPE_CODE_FLAGS
20693 @findex gdb.TYPE_CODE_FLAGS
20694 @item TYPE_CODE_FLAGS
20695 A bit flags type, used for things such as status registers.
20697 @findex TYPE_CODE_FUNC
20698 @findex gdb.TYPE_CODE_FUNC
20699 @item TYPE_CODE_FUNC
20700 The type is a function.
20702 @findex TYPE_CODE_INT
20703 @findex gdb.TYPE_CODE_INT
20704 @item TYPE_CODE_INT
20705 The type is an integer type.
20707 @findex TYPE_CODE_FLT
20708 @findex gdb.TYPE_CODE_FLT
20709 @item TYPE_CODE_FLT
20710 A floating point type.
20712 @findex TYPE_CODE_VOID
20713 @findex gdb.TYPE_CODE_VOID
20714 @item TYPE_CODE_VOID
20715 The special type @code{void}.
20717 @findex TYPE_CODE_SET
20718 @findex gdb.TYPE_CODE_SET
20719 @item TYPE_CODE_SET
20722 @findex TYPE_CODE_RANGE
20723 @findex gdb.TYPE_CODE_RANGE
20724 @item TYPE_CODE_RANGE
20725 A range type, that is, an integer type with bounds.
20727 @findex TYPE_CODE_STRING
20728 @findex gdb.TYPE_CODE_STRING
20729 @item TYPE_CODE_STRING
20730 A string type. Note that this is only used for certain languages with
20731 language-defined string types; C strings are not represented this way.
20733 @findex TYPE_CODE_BITSTRING
20734 @findex gdb.TYPE_CODE_BITSTRING
20735 @item TYPE_CODE_BITSTRING
20738 @findex TYPE_CODE_ERROR
20739 @findex gdb.TYPE_CODE_ERROR
20740 @item TYPE_CODE_ERROR
20741 An unknown or erroneous type.
20743 @findex TYPE_CODE_METHOD
20744 @findex gdb.TYPE_CODE_METHOD
20745 @item TYPE_CODE_METHOD
20746 A method type, as found in C@t{++} or Java.
20748 @findex TYPE_CODE_METHODPTR
20749 @findex gdb.TYPE_CODE_METHODPTR
20750 @item TYPE_CODE_METHODPTR
20751 A pointer-to-member-function.
20753 @findex TYPE_CODE_MEMBERPTR
20754 @findex gdb.TYPE_CODE_MEMBERPTR
20755 @item TYPE_CODE_MEMBERPTR
20756 A pointer-to-member.
20758 @findex TYPE_CODE_REF
20759 @findex gdb.TYPE_CODE_REF
20760 @item TYPE_CODE_REF
20763 @findex TYPE_CODE_CHAR
20764 @findex gdb.TYPE_CODE_CHAR
20765 @item TYPE_CODE_CHAR
20768 @findex TYPE_CODE_BOOL
20769 @findex gdb.TYPE_CODE_BOOL
20770 @item TYPE_CODE_BOOL
20773 @findex TYPE_CODE_COMPLEX
20774 @findex gdb.TYPE_CODE_COMPLEX
20775 @item TYPE_CODE_COMPLEX
20776 A complex float type.
20778 @findex TYPE_CODE_TYPEDEF
20779 @findex gdb.TYPE_CODE_TYPEDEF
20780 @item TYPE_CODE_TYPEDEF
20781 A typedef to some other type.
20783 @findex TYPE_CODE_NAMESPACE
20784 @findex gdb.TYPE_CODE_NAMESPACE
20785 @item TYPE_CODE_NAMESPACE
20786 A C@t{++} namespace.
20788 @findex TYPE_CODE_DECFLOAT
20789 @findex gdb.TYPE_CODE_DECFLOAT
20790 @item TYPE_CODE_DECFLOAT
20791 A decimal floating point type.
20793 @findex TYPE_CODE_INTERNAL_FUNCTION
20794 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20795 @item TYPE_CODE_INTERNAL_FUNCTION
20796 A function internal to @value{GDBN}. This is the type used to represent
20797 convenience functions.
20800 @node Pretty Printing API
20801 @subsubsection Pretty Printing API
20803 An example output is provided (@pxref{Pretty Printing}).
20805 A pretty-printer is just an object that holds a value and implements a
20806 specific interface, defined here.
20808 @defop Operation {pretty printer} children (self)
20809 @value{GDBN} will call this method on a pretty-printer to compute the
20810 children of the pretty-printer's value.
20812 This method must return an object conforming to the Python iterator
20813 protocol. Each item returned by the iterator must be a tuple holding
20814 two elements. The first element is the ``name'' of the child; the
20815 second element is the child's value. The value can be any Python
20816 object which is convertible to a @value{GDBN} value.
20818 This method is optional. If it does not exist, @value{GDBN} will act
20819 as though the value has no children.
20822 @defop Operation {pretty printer} display_hint (self)
20823 The CLI may call this method and use its result to change the
20824 formatting of a value. The result will also be supplied to an MI
20825 consumer as a @samp{displayhint} attribute of the variable being
20828 This method is optional. If it does exist, this method must return a
20831 Some display hints are predefined by @value{GDBN}:
20835 Indicate that the object being printed is ``array-like''. The CLI
20836 uses this to respect parameters such as @code{set print elements} and
20837 @code{set print array}.
20840 Indicate that the object being printed is ``map-like'', and that the
20841 children of this value can be assumed to alternate between keys and
20845 Indicate that the object being printed is ``string-like''. If the
20846 printer's @code{to_string} method returns a Python string of some
20847 kind, then @value{GDBN} will call its internal language-specific
20848 string-printing function to format the string. For the CLI this means
20849 adding quotation marks, possibly escaping some characters, respecting
20850 @code{set print elements}, and the like.
20854 @defop Operation {pretty printer} to_string (self)
20855 @value{GDBN} will call this method to display the string
20856 representation of the value passed to the object's constructor.
20858 When printing from the CLI, if the @code{to_string} method exists,
20859 then @value{GDBN} will prepend its result to the values returned by
20860 @code{children}. Exactly how this formatting is done is dependent on
20861 the display hint, and may change as more hints are added. Also,
20862 depending on the print settings (@pxref{Print Settings}), the CLI may
20863 print just the result of @code{to_string} in a stack trace, omitting
20864 the result of @code{children}.
20866 If this method returns a string, it is printed verbatim.
20868 Otherwise, if this method returns an instance of @code{gdb.Value},
20869 then @value{GDBN} prints this value. This may result in a call to
20870 another pretty-printer.
20872 If instead the method returns a Python value which is convertible to a
20873 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20874 the resulting value. Again, this may result in a call to another
20875 pretty-printer. Python scalars (integers, floats, and booleans) and
20876 strings are convertible to @code{gdb.Value}; other types are not.
20878 Finally, if this method returns @code{None} then no further operations
20879 are peformed in this method and nothing is printed.
20881 If the result is not one of these types, an exception is raised.
20884 @node Selecting Pretty-Printers
20885 @subsubsection Selecting Pretty-Printers
20887 The Python list @code{gdb.pretty_printers} contains an array of
20888 functions or callable objects that have been registered via addition
20889 as a pretty-printer.
20890 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20891 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20894 A function on one of these lists is passed a single @code{gdb.Value}
20895 argument and should return a pretty-printer object conforming to the
20896 interface definition above (@pxref{Pretty Printing API}). If a function
20897 cannot create a pretty-printer for the value, it should return
20900 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20901 @code{gdb.Objfile} in the current program space and iteratively calls
20902 each enabled function (@pxref{Disabling Pretty-Printers})
20903 in the list for that @code{gdb.Objfile} until it receives
20904 a pretty-printer object.
20905 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20906 searches the pretty-printer list of the current program space,
20907 calling each enabled function until an object is returned.
20908 After these lists have been exhausted, it tries the global
20909 @code{gdb.pretty_printers} list, again calling each enabled function until an
20910 object is returned.
20912 The order in which the objfiles are searched is not specified. For a
20913 given list, functions are always invoked from the head of the list,
20914 and iterated over sequentially until the end of the list, or a printer
20915 object is returned.
20917 Here is an example showing how a @code{std::string} printer might be
20921 class StdStringPrinter:
20922 "Print a std::string"
20924 def __init__ (self, val):
20927 def to_string (self):
20928 return self.val['_M_dataplus']['_M_p']
20930 def display_hint (self):
20934 And here is an example showing how a lookup function for the printer
20935 example above might be written.
20938 def str_lookup_function (val):
20940 lookup_tag = val.type.tag
20941 regex = re.compile ("^std::basic_string<char,.*>$")
20942 if lookup_tag == None:
20944 if regex.match (lookup_tag):
20945 return StdStringPrinter (val)
20950 The example lookup function extracts the value's type, and attempts to
20951 match it to a type that it can pretty-print. If it is a type the
20952 printer can pretty-print, it will return a printer object. If not, it
20953 returns @code{None}.
20955 We recommend that you put your core pretty-printers into a Python
20956 package. If your pretty-printers are for use with a library, we
20957 further recommend embedding a version number into the package name.
20958 This practice will enable @value{GDBN} to load multiple versions of
20959 your pretty-printers at the same time, because they will have
20962 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20963 can be evaluated multiple times without changing its meaning. An
20964 ideal auto-load file will consist solely of @code{import}s of your
20965 printer modules, followed by a call to a register pretty-printers with
20966 the current objfile.
20968 Taken as a whole, this approach will scale nicely to multiple
20969 inferiors, each potentially using a different library version.
20970 Embedding a version number in the Python package name will ensure that
20971 @value{GDBN} is able to load both sets of printers simultaneously.
20972 Then, because the search for pretty-printers is done by objfile, and
20973 because your auto-loaded code took care to register your library's
20974 printers with a specific objfile, @value{GDBN} will find the correct
20975 printers for the specific version of the library used by each
20978 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
20979 this code might appear in @code{gdb.libstdcxx.v6}:
20982 def register_printers (objfile):
20983 objfile.pretty_printers.add (str_lookup_function)
20987 And then the corresponding contents of the auto-load file would be:
20990 import gdb.libstdcxx.v6
20991 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20994 @node Disabling Pretty-Printers
20995 @subsubsection Disabling Pretty-Printers
20996 @cindex disabling pretty-printers
20998 For various reasons a pretty-printer may not work.
20999 For example, the underlying data structure may have changed and
21000 the pretty-printer is out of date.
21002 The consequences of a broken pretty-printer are severe enough that
21003 @value{GDBN} provides support for enabling and disabling individual
21004 printers. For example, if @code{print frame-arguments} is on,
21005 a backtrace can become highly illegible if any argument is printed
21006 with a broken printer.
21008 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21009 attribute to the registered function or callable object. If this attribute
21010 is present and its value is @code{False}, the printer is disabled, otherwise
21011 the printer is enabled.
21013 @node Inferiors In Python
21014 @subsubsection Inferiors In Python
21015 @cindex inferiors in python
21017 @findex gdb.Inferior
21018 Programs which are being run under @value{GDBN} are called inferiors
21019 (@pxref{Inferiors and Programs}). Python scripts can access
21020 information about and manipulate inferiors controlled by @value{GDBN}
21021 via objects of the @code{gdb.Inferior} class.
21023 The following inferior-related functions are available in the @code{gdb}
21027 Return a tuple containing all inferior objects.
21030 A @code{gdb.Inferior} object has the following attributes:
21033 @defivar Inferior num
21034 ID of inferior, as assigned by GDB.
21037 @defivar Inferior pid
21038 Process ID of the inferior, as assigned by the underlying operating
21042 @defivar Inferior was_attached
21043 Boolean signaling whether the inferior was created using `attach', or
21044 started by @value{GDBN} itself.
21048 A @code{gdb.Inferior} object has the following methods:
21051 @defmethod Inferior threads
21052 This method returns a tuple holding all the threads which are valid
21053 when it is called. If there are no valid threads, the method will
21054 return an empty tuple.
21057 @findex gdb.read_memory
21058 @defmethod Inferior read_memory address length
21059 Read @var{length} bytes of memory from the inferior, starting at
21060 @var{address}. Returns a buffer object, which behaves much like an array
21061 or a string. It can be modified and given to the @code{gdb.write_memory}
21065 @findex gdb.write_memory
21066 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21067 Write the contents of @var{buffer} to the inferior, starting at
21068 @var{address}. The @var{buffer} parameter must be a Python object
21069 which supports the buffer protocol, i.e., a string, an array or the
21070 object returned from @code{gdb.read_memory}. If given, @var{length}
21071 determines the number of bytes from @var{buffer} to be written.
21074 @findex gdb.search_memory
21075 @defmethod Inferior search_memory address length pattern
21076 Search a region of the inferior memory starting at @var{address} with
21077 the given @var{length} using the search pattern supplied in
21078 @var{pattern}. The @var{pattern} parameter must be a Python object
21079 which supports the buffer protocol, i.e., a string, an array or the
21080 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21081 containing the address where the pattern was found, or @code{None} if
21082 the pattern could not be found.
21086 @node Threads In Python
21087 @subsubsection Threads In Python
21088 @cindex threads in python
21090 @findex gdb.InferiorThread
21091 Python scripts can access information about, and manipulate inferior threads
21092 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21094 The following thread-related functions are available in the @code{gdb}
21097 @findex gdb.selected_thread
21098 @defun selected_thread
21099 This function returns the thread object for the selected thread. If there
21100 is no selected thread, this will return @code{None}.
21103 A @code{gdb.InferiorThread} object has the following attributes:
21106 @defivar InferiorThread num
21107 ID of the thread, as assigned by GDB.
21110 @defivar InferiorThread ptid
21111 ID of the thread, as assigned by the operating system. This attribute is a
21112 tuple containing three integers. The first is the Process ID (PID); the second
21113 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21114 Either the LWPID or TID may be 0, which indicates that the operating system
21115 does not use that identifier.
21119 A @code{gdb.InferiorThread} object has the following methods:
21121 @defmethod InferiorThread switch
21122 This changes @value{GDBN}'s currently selected thread to the one represented
21126 @defmethod InferiorThread is_stopped
21127 Return a Boolean indicating whether the thread is stopped.
21130 @defmethod InferiorThread is_running
21131 Return a Boolean indicating whether the thread is running.
21134 @defmethod InferiorThread is_exited
21135 Return a Boolean indicating whether the thread is exited.
21139 @node Commands In Python
21140 @subsubsection Commands In Python
21142 @cindex commands in python
21143 @cindex python commands
21144 You can implement new @value{GDBN} CLI commands in Python. A CLI
21145 command is implemented using an instance of the @code{gdb.Command}
21146 class, most commonly using a subclass.
21148 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21149 The object initializer for @code{Command} registers the new command
21150 with @value{GDBN}. This initializer is normally invoked from the
21151 subclass' own @code{__init__} method.
21153 @var{name} is the name of the command. If @var{name} consists of
21154 multiple words, then the initial words are looked for as prefix
21155 commands. In this case, if one of the prefix commands does not exist,
21156 an exception is raised.
21158 There is no support for multi-line commands.
21160 @var{command_class} should be one of the @samp{COMMAND_} constants
21161 defined below. This argument tells @value{GDBN} how to categorize the
21162 new command in the help system.
21164 @var{completer_class} is an optional argument. If given, it should be
21165 one of the @samp{COMPLETE_} constants defined below. This argument
21166 tells @value{GDBN} how to perform completion for this command. If not
21167 given, @value{GDBN} will attempt to complete using the object's
21168 @code{complete} method (see below); if no such method is found, an
21169 error will occur when completion is attempted.
21171 @var{prefix} is an optional argument. If @code{True}, then the new
21172 command is a prefix command; sub-commands of this command may be
21175 The help text for the new command is taken from the Python
21176 documentation string for the command's class, if there is one. If no
21177 documentation string is provided, the default value ``This command is
21178 not documented.'' is used.
21181 @cindex don't repeat Python command
21182 @defmethod Command dont_repeat
21183 By default, a @value{GDBN} command is repeated when the user enters a
21184 blank line at the command prompt. A command can suppress this
21185 behavior by invoking the @code{dont_repeat} method. This is similar
21186 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21189 @defmethod Command invoke argument from_tty
21190 This method is called by @value{GDBN} when this command is invoked.
21192 @var{argument} is a string. It is the argument to the command, after
21193 leading and trailing whitespace has been stripped.
21195 @var{from_tty} is a boolean argument. When true, this means that the
21196 command was entered by the user at the terminal; when false it means
21197 that the command came from elsewhere.
21199 If this method throws an exception, it is turned into a @value{GDBN}
21200 @code{error} call. Otherwise, the return value is ignored.
21202 @findex gdb.string_to_argv
21203 To break @var{argument} up into an argv-like string use
21204 @code{gdb.string_to_argv}. This function behaves identically to
21205 @value{GDBN}'s internal argument lexer @code{buildargv}.
21206 It is recommended to use this for consistency.
21207 Arguments are separated by spaces and may be quoted.
21211 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21212 ['1', '2 "3', '4 "5', "6 '7"]
21217 @cindex completion of Python commands
21218 @defmethod Command complete text word
21219 This method is called by @value{GDBN} when the user attempts
21220 completion on this command. All forms of completion are handled by
21221 this method, that is, the @key{TAB} and @key{M-?} key bindings
21222 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21225 The arguments @var{text} and @var{word} are both strings. @var{text}
21226 holds the complete command line up to the cursor's location.
21227 @var{word} holds the last word of the command line; this is computed
21228 using a word-breaking heuristic.
21230 The @code{complete} method can return several values:
21233 If the return value is a sequence, the contents of the sequence are
21234 used as the completions. It is up to @code{complete} to ensure that the
21235 contents actually do complete the word. A zero-length sequence is
21236 allowed, it means that there were no completions available. Only
21237 string elements of the sequence are used; other elements in the
21238 sequence are ignored.
21241 If the return value is one of the @samp{COMPLETE_} constants defined
21242 below, then the corresponding @value{GDBN}-internal completion
21243 function is invoked, and its result is used.
21246 All other results are treated as though there were no available
21251 When a new command is registered, it must be declared as a member of
21252 some general class of commands. This is used to classify top-level
21253 commands in the on-line help system; note that prefix commands are not
21254 listed under their own category but rather that of their top-level
21255 command. The available classifications are represented by constants
21256 defined in the @code{gdb} module:
21259 @findex COMMAND_NONE
21260 @findex gdb.COMMAND_NONE
21262 The command does not belong to any particular class. A command in
21263 this category will not be displayed in any of the help categories.
21265 @findex COMMAND_RUNNING
21266 @findex gdb.COMMAND_RUNNING
21267 @item COMMAND_RUNNING
21268 The command is related to running the inferior. For example,
21269 @code{start}, @code{step}, and @code{continue} are in this category.
21270 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21271 commands in this category.
21273 @findex COMMAND_DATA
21274 @findex gdb.COMMAND_DATA
21276 The command is related to data or variables. For example,
21277 @code{call}, @code{find}, and @code{print} are in this category. Type
21278 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21281 @findex COMMAND_STACK
21282 @findex gdb.COMMAND_STACK
21283 @item COMMAND_STACK
21284 The command has to do with manipulation of the stack. For example,
21285 @code{backtrace}, @code{frame}, and @code{return} are in this
21286 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21287 list of commands in this category.
21289 @findex COMMAND_FILES
21290 @findex gdb.COMMAND_FILES
21291 @item COMMAND_FILES
21292 This class is used for file-related commands. For example,
21293 @code{file}, @code{list} and @code{section} are in this category.
21294 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21295 commands in this category.
21297 @findex COMMAND_SUPPORT
21298 @findex gdb.COMMAND_SUPPORT
21299 @item COMMAND_SUPPORT
21300 This should be used for ``support facilities'', generally meaning
21301 things that are useful to the user when interacting with @value{GDBN},
21302 but not related to the state of the inferior. For example,
21303 @code{help}, @code{make}, and @code{shell} are in this category. Type
21304 @kbd{help support} at the @value{GDBN} prompt to see a list of
21305 commands in this category.
21307 @findex COMMAND_STATUS
21308 @findex gdb.COMMAND_STATUS
21309 @item COMMAND_STATUS
21310 The command is an @samp{info}-related command, that is, related to the
21311 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21312 and @code{show} are in this category. Type @kbd{help status} at the
21313 @value{GDBN} prompt to see a list of commands in this category.
21315 @findex COMMAND_BREAKPOINTS
21316 @findex gdb.COMMAND_BREAKPOINTS
21317 @item COMMAND_BREAKPOINTS
21318 The command has to do with breakpoints. For example, @code{break},
21319 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21320 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21323 @findex COMMAND_TRACEPOINTS
21324 @findex gdb.COMMAND_TRACEPOINTS
21325 @item COMMAND_TRACEPOINTS
21326 The command has to do with tracepoints. For example, @code{trace},
21327 @code{actions}, and @code{tfind} are in this category. Type
21328 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21329 commands in this category.
21331 @findex COMMAND_OBSCURE
21332 @findex gdb.COMMAND_OBSCURE
21333 @item COMMAND_OBSCURE
21334 The command is only used in unusual circumstances, or is not of
21335 general interest to users. For example, @code{checkpoint},
21336 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21337 obscure} at the @value{GDBN} prompt to see a list of commands in this
21340 @findex COMMAND_MAINTENANCE
21341 @findex gdb.COMMAND_MAINTENANCE
21342 @item COMMAND_MAINTENANCE
21343 The command is only useful to @value{GDBN} maintainers. The
21344 @code{maintenance} and @code{flushregs} commands are in this category.
21345 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21346 commands in this category.
21349 A new command can use a predefined completion function, either by
21350 specifying it via an argument at initialization, or by returning it
21351 from the @code{complete} method. These predefined completion
21352 constants are all defined in the @code{gdb} module:
21355 @findex COMPLETE_NONE
21356 @findex gdb.COMPLETE_NONE
21357 @item COMPLETE_NONE
21358 This constant means that no completion should be done.
21360 @findex COMPLETE_FILENAME
21361 @findex gdb.COMPLETE_FILENAME
21362 @item COMPLETE_FILENAME
21363 This constant means that filename completion should be performed.
21365 @findex COMPLETE_LOCATION
21366 @findex gdb.COMPLETE_LOCATION
21367 @item COMPLETE_LOCATION
21368 This constant means that location completion should be done.
21369 @xref{Specify Location}.
21371 @findex COMPLETE_COMMAND
21372 @findex gdb.COMPLETE_COMMAND
21373 @item COMPLETE_COMMAND
21374 This constant means that completion should examine @value{GDBN}
21377 @findex COMPLETE_SYMBOL
21378 @findex gdb.COMPLETE_SYMBOL
21379 @item COMPLETE_SYMBOL
21380 This constant means that completion should be done using symbol names
21384 The following code snippet shows how a trivial CLI command can be
21385 implemented in Python:
21388 class HelloWorld (gdb.Command):
21389 """Greet the whole world."""
21391 def __init__ (self):
21392 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21394 def invoke (self, arg, from_tty):
21395 print "Hello, World!"
21400 The last line instantiates the class, and is necessary to trigger the
21401 registration of the command with @value{GDBN}. Depending on how the
21402 Python code is read into @value{GDBN}, you may need to import the
21403 @code{gdb} module explicitly.
21405 @node Parameters In Python
21406 @subsubsection Parameters In Python
21408 @cindex parameters in python
21409 @cindex python parameters
21410 @tindex gdb.Parameter
21412 You can implement new @value{GDBN} parameters using Python. A new
21413 parameter is implemented as an instance of the @code{gdb.Parameter}
21416 Parameters are exposed to the user via the @code{set} and
21417 @code{show} commands. @xref{Help}.
21419 There are many parameters that already exist and can be set in
21420 @value{GDBN}. Two examples are: @code{set follow fork} and
21421 @code{set charset}. Setting these parameters influences certain
21422 behavior in @value{GDBN}. Similarly, you can define parameters that
21423 can be used to influence behavior in custom Python scripts and commands.
21425 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21426 The object initializer for @code{Parameter} registers the new
21427 parameter with @value{GDBN}. This initializer is normally invoked
21428 from the subclass' own @code{__init__} method.
21430 @var{name} is the name of the new parameter. If @var{name} consists
21431 of multiple words, then the initial words are looked for as prefix
21432 parameters. An example of this can be illustrated with the
21433 @code{set print} set of parameters. If @var{name} is
21434 @code{print foo}, then @code{print} will be searched as the prefix
21435 parameter. In this case the parameter can subsequently be accessed in
21436 @value{GDBN} as @code{set print foo}.
21438 If @var{name} consists of multiple words, and no prefix parameter group
21439 can be found, an exception is raised.
21441 @var{command-class} should be one of the @samp{COMMAND_} constants
21442 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21443 categorize the new parameter in the help system.
21445 @var{parameter-class} should be one of the @samp{PARAM_} constants
21446 defined below. This argument tells @value{GDBN} the type of the new
21447 parameter; this information is used for input validation and
21450 If @var{parameter-class} is @code{PARAM_ENUM}, then
21451 @var{enum-sequence} must be a sequence of strings. These strings
21452 represent the possible values for the parameter.
21454 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21455 of a fourth argument will cause an exception to be thrown.
21457 The help text for the new parameter is taken from the Python
21458 documentation string for the parameter's class, if there is one. If
21459 there is no documentation string, a default value is used.
21462 @defivar Parameter set_doc
21463 If this attribute exists, and is a string, then its value is used as
21464 the help text for this parameter's @code{set} command. The value is
21465 examined when @code{Parameter.__init__} is invoked; subsequent changes
21469 @defivar Parameter show_doc
21470 If this attribute exists, and is a string, then its value is used as
21471 the help text for this parameter's @code{show} command. The value is
21472 examined when @code{Parameter.__init__} is invoked; subsequent changes
21476 @defivar Parameter value
21477 The @code{value} attribute holds the underlying value of the
21478 parameter. It can be read and assigned to just as any other
21479 attribute. @value{GDBN} does validation when assignments are made.
21483 When a new parameter is defined, its type must be specified. The
21484 available types are represented by constants defined in the @code{gdb}
21488 @findex PARAM_BOOLEAN
21489 @findex gdb.PARAM_BOOLEAN
21490 @item PARAM_BOOLEAN
21491 The value is a plain boolean. The Python boolean values, @code{True}
21492 and @code{False} are the only valid values.
21494 @findex PARAM_AUTO_BOOLEAN
21495 @findex gdb.PARAM_AUTO_BOOLEAN
21496 @item PARAM_AUTO_BOOLEAN
21497 The value has three possible states: true, false, and @samp{auto}. In
21498 Python, true and false are represented using boolean constants, and
21499 @samp{auto} is represented using @code{None}.
21501 @findex PARAM_UINTEGER
21502 @findex gdb.PARAM_UINTEGER
21503 @item PARAM_UINTEGER
21504 The value is an unsigned integer. The value of 0 should be
21505 interpreted to mean ``unlimited''.
21507 @findex PARAM_INTEGER
21508 @findex gdb.PARAM_INTEGER
21509 @item PARAM_INTEGER
21510 The value is a signed integer. The value of 0 should be interpreted
21511 to mean ``unlimited''.
21513 @findex PARAM_STRING
21514 @findex gdb.PARAM_STRING
21516 The value is a string. When the user modifies the string, any escape
21517 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21518 translated into corresponding characters and encoded into the current
21521 @findex PARAM_STRING_NOESCAPE
21522 @findex gdb.PARAM_STRING_NOESCAPE
21523 @item PARAM_STRING_NOESCAPE
21524 The value is a string. When the user modifies the string, escapes are
21525 passed through untranslated.
21527 @findex PARAM_OPTIONAL_FILENAME
21528 @findex gdb.PARAM_OPTIONAL_FILENAME
21529 @item PARAM_OPTIONAL_FILENAME
21530 The value is a either a filename (a string), or @code{None}.
21532 @findex PARAM_FILENAME
21533 @findex gdb.PARAM_FILENAME
21534 @item PARAM_FILENAME
21535 The value is a filename. This is just like
21536 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21538 @findex PARAM_ZINTEGER
21539 @findex gdb.PARAM_ZINTEGER
21540 @item PARAM_ZINTEGER
21541 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21542 is interpreted as itself.
21545 @findex gdb.PARAM_ENUM
21547 The value is a string, which must be one of a collection string
21548 constants provided when the parameter is created.
21551 @node Functions In Python
21552 @subsubsection Writing new convenience functions
21554 @cindex writing convenience functions
21555 @cindex convenience functions in python
21556 @cindex python convenience functions
21557 @tindex gdb.Function
21559 You can implement new convenience functions (@pxref{Convenience Vars})
21560 in Python. A convenience function is an instance of a subclass of the
21561 class @code{gdb.Function}.
21563 @defmethod Function __init__ name
21564 The initializer for @code{Function} registers the new function with
21565 @value{GDBN}. The argument @var{name} is the name of the function,
21566 a string. The function will be visible to the user as a convenience
21567 variable of type @code{internal function}, whose name is the same as
21568 the given @var{name}.
21570 The documentation for the new function is taken from the documentation
21571 string for the new class.
21574 @defmethod Function invoke @var{*args}
21575 When a convenience function is evaluated, its arguments are converted
21576 to instances of @code{gdb.Value}, and then the function's
21577 @code{invoke} method is called. Note that @value{GDBN} does not
21578 predetermine the arity of convenience functions. Instead, all
21579 available arguments are passed to @code{invoke}, following the
21580 standard Python calling convention. In particular, a convenience
21581 function can have default values for parameters without ill effect.
21583 The return value of this method is used as its value in the enclosing
21584 expression. If an ordinary Python value is returned, it is converted
21585 to a @code{gdb.Value} following the usual rules.
21588 The following code snippet shows how a trivial convenience function can
21589 be implemented in Python:
21592 class Greet (gdb.Function):
21593 """Return string to greet someone.
21594 Takes a name as argument."""
21596 def __init__ (self):
21597 super (Greet, self).__init__ ("greet")
21599 def invoke (self, name):
21600 return "Hello, %s!" % name.string ()
21605 The last line instantiates the class, and is necessary to trigger the
21606 registration of the function with @value{GDBN}. Depending on how the
21607 Python code is read into @value{GDBN}, you may need to import the
21608 @code{gdb} module explicitly.
21610 @node Progspaces In Python
21611 @subsubsection Program Spaces In Python
21613 @cindex progspaces in python
21614 @tindex gdb.Progspace
21616 A program space, or @dfn{progspace}, represents a symbolic view
21617 of an address space.
21618 It consists of all of the objfiles of the program.
21619 @xref{Objfiles In Python}.
21620 @xref{Inferiors and Programs, program spaces}, for more details
21621 about program spaces.
21623 The following progspace-related functions are available in the
21626 @findex gdb.current_progspace
21627 @defun current_progspace
21628 This function returns the program space of the currently selected inferior.
21629 @xref{Inferiors and Programs}.
21632 @findex gdb.progspaces
21634 Return a sequence of all the progspaces currently known to @value{GDBN}.
21637 Each progspace is represented by an instance of the @code{gdb.Progspace}
21640 @defivar Progspace filename
21641 The file name of the progspace as a string.
21644 @defivar Progspace pretty_printers
21645 The @code{pretty_printers} attribute is a list of functions. It is
21646 used to look up pretty-printers. A @code{Value} is passed to each
21647 function in order; if the function returns @code{None}, then the
21648 search continues. Otherwise, the return value should be an object
21649 which is used to format the value. @xref{Pretty Printing API}, for more
21653 @node Objfiles In Python
21654 @subsubsection Objfiles In Python
21656 @cindex objfiles in python
21657 @tindex gdb.Objfile
21659 @value{GDBN} loads symbols for an inferior from various
21660 symbol-containing files (@pxref{Files}). These include the primary
21661 executable file, any shared libraries used by the inferior, and any
21662 separate debug info files (@pxref{Separate Debug Files}).
21663 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21665 The following objfile-related functions are available in the
21668 @findex gdb.current_objfile
21669 @defun current_objfile
21670 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21671 sets the ``current objfile'' to the corresponding objfile. This
21672 function returns the current objfile. If there is no current objfile,
21673 this function returns @code{None}.
21676 @findex gdb.objfiles
21678 Return a sequence of all the objfiles current known to @value{GDBN}.
21679 @xref{Objfiles In Python}.
21682 Each objfile is represented by an instance of the @code{gdb.Objfile}
21685 @defivar Objfile filename
21686 The file name of the objfile as a string.
21689 @defivar Objfile pretty_printers
21690 The @code{pretty_printers} attribute is a list of functions. It is
21691 used to look up pretty-printers. A @code{Value} is passed to each
21692 function in order; if the function returns @code{None}, then the
21693 search continues. Otherwise, the return value should be an object
21694 which is used to format the value. @xref{Pretty Printing API}, for more
21698 @node Frames In Python
21699 @subsubsection Accessing inferior stack frames from Python.
21701 @cindex frames in python
21702 When the debugged program stops, @value{GDBN} is able to analyze its call
21703 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21704 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21705 while its corresponding frame exists in the inferior's stack. If you try
21706 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21709 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21713 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21717 The following frame-related functions are available in the @code{gdb} module:
21719 @findex gdb.selected_frame
21720 @defun selected_frame
21721 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21724 @defun frame_stop_reason_string reason
21725 Return a string explaining the reason why @value{GDBN} stopped unwinding
21726 frames, as expressed by the given @var{reason} code (an integer, see the
21727 @code{unwind_stop_reason} method further down in this section).
21730 A @code{gdb.Frame} object has the following methods:
21733 @defmethod Frame is_valid
21734 Returns true if the @code{gdb.Frame} object is valid, false if not.
21735 A frame object can become invalid if the frame it refers to doesn't
21736 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21737 an exception if it is invalid at the time the method is called.
21740 @defmethod Frame name
21741 Returns the function name of the frame, or @code{None} if it can't be
21745 @defmethod Frame type
21746 Returns the type of the frame. The value can be one of
21747 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21748 or @code{gdb.SENTINEL_FRAME}.
21751 @defmethod Frame unwind_stop_reason
21752 Return an integer representing the reason why it's not possible to find
21753 more frames toward the outermost frame. Use
21754 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21755 function to a string.
21758 @defmethod Frame pc
21759 Returns the frame's resume address.
21762 @defmethod Frame block
21763 Return the frame's code block. @xref{Blocks In Python}.
21766 @defmethod Frame function
21767 Return the symbol for the function corresponding to this frame.
21768 @xref{Symbols In Python}.
21771 @defmethod Frame older
21772 Return the frame that called this frame.
21775 @defmethod Frame newer
21776 Return the frame called by this frame.
21779 @defmethod Frame find_sal
21780 Return the frame's symtab and line object.
21781 @xref{Symbol Tables In Python}.
21784 @defmethod Frame read_var variable @r{[}block@r{]}
21785 Return the value of @var{variable} in this frame. If the optional
21786 argument @var{block} is provided, search for the variable from that
21787 block; otherwise start at the frame's current block (which is
21788 determined by the frame's current program counter). @var{variable}
21789 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21790 @code{gdb.Block} object.
21793 @defmethod Frame select
21794 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21799 @node Blocks In Python
21800 @subsubsection Accessing frame blocks from Python.
21802 @cindex blocks in python
21805 Within each frame, @value{GDBN} maintains information on each block
21806 stored in that frame. These blocks are organized hierarchically, and
21807 are represented individually in Python as a @code{gdb.Block}.
21808 Please see @ref{Frames In Python}, for a more in-depth discussion on
21809 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21810 detailed technical information on @value{GDBN}'s book-keeping of the
21813 The following block-related functions are available in the @code{gdb}
21816 @findex gdb.block_for_pc
21817 @defun block_for_pc pc
21818 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21819 block cannot be found for the @var{pc} value specified, the function
21820 will return @code{None}.
21823 A @code{gdb.Block} object has the following attributes:
21826 @defivar Block start
21827 The start address of the block. This attribute is not writable.
21831 The end address of the block. This attribute is not writable.
21834 @defivar Block function
21835 The name of the block represented as a @code{gdb.Symbol}. If the
21836 block is not named, then this attribute holds @code{None}. This
21837 attribute is not writable.
21840 @defivar Block superblock
21841 The block containing this block. If this parent block does not exist,
21842 this attribute holds @code{None}. This attribute is not writable.
21846 @node Symbols In Python
21847 @subsubsection Python representation of Symbols.
21849 @cindex symbols in python
21852 @value{GDBN} represents every variable, function and type as an
21853 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21854 Similarly, Python represents these symbols in @value{GDBN} with the
21855 @code{gdb.Symbol} object.
21857 The following symbol-related functions are available in the @code{gdb}
21860 @findex gdb.lookup_symbol
21861 @defun lookup_symbol name [block] [domain]
21862 This function searches for a symbol by name. The search scope can be
21863 restricted to the parameters defined in the optional domain and block
21866 @var{name} is the name of the symbol. It must be a string. The
21867 optional @var{block} argument restricts the search to symbols visible
21868 in that @var{block}. The @var{block} argument must be a
21869 @code{gdb.Block} object. The optional @var{domain} argument restricts
21870 the search to the domain type. The @var{domain} argument must be a
21871 domain constant defined in the @code{gdb} module and described later
21875 A @code{gdb.Symbol} object has the following attributes:
21878 @defivar Symbol symtab
21879 The symbol table in which the symbol appears. This attribute is
21880 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21881 Python}. This attribute is not writable.
21884 @defivar Symbol name
21885 The name of the symbol as a string. This attribute is not writable.
21888 @defivar Symbol linkage_name
21889 The name of the symbol, as used by the linker (i.e., may be mangled).
21890 This attribute is not writable.
21893 @defivar Symbol print_name
21894 The name of the symbol in a form suitable for output. This is either
21895 @code{name} or @code{linkage_name}, depending on whether the user
21896 asked @value{GDBN} to display demangled or mangled names.
21899 @defivar Symbol addr_class
21900 The address class of the symbol. This classifies how to find the value
21901 of a symbol. Each address class is a constant defined in the
21902 @code{gdb} module and described later in this chapter.
21905 @defivar Symbol is_argument
21906 @code{True} if the symbol is an argument of a function.
21909 @defivar Symbol is_constant
21910 @code{True} if the symbol is a constant.
21913 @defivar Symbol is_function
21914 @code{True} if the symbol is a function or a method.
21917 @defivar Symbol is_variable
21918 @code{True} if the symbol is a variable.
21922 The available domain categories in @code{gdb.Symbol} are represented
21923 as constants in the @code{gdb} module:
21926 @findex SYMBOL_UNDEF_DOMAIN
21927 @findex gdb.SYMBOL_UNDEF_DOMAIN
21928 @item SYMBOL_UNDEF_DOMAIN
21929 This is used when a domain has not been discovered or none of the
21930 following domains apply. This usually indicates an error either
21931 in the symbol information or in @value{GDBN}'s handling of symbols.
21932 @findex SYMBOL_VAR_DOMAIN
21933 @findex gdb.SYMBOL_VAR_DOMAIN
21934 @item SYMBOL_VAR_DOMAIN
21935 This domain contains variables, function names, typedef names and enum
21937 @findex SYMBOL_STRUCT_DOMAIN
21938 @findex gdb.SYMBOL_STRUCT_DOMAIN
21939 @item SYMBOL_STRUCT_DOMAIN
21940 This domain holds struct, union and enum type names.
21941 @findex SYMBOL_LABEL_DOMAIN
21942 @findex gdb.SYMBOL_LABEL_DOMAIN
21943 @item SYMBOL_LABEL_DOMAIN
21944 This domain contains names of labels (for gotos).
21945 @findex SYMBOL_VARIABLES_DOMAIN
21946 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21947 @item SYMBOL_VARIABLES_DOMAIN
21948 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21949 contains everything minus functions and types.
21950 @findex SYMBOL_FUNCTIONS_DOMAIN
21951 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21952 @item SYMBOL_FUNCTION_DOMAIN
21953 This domain contains all functions.
21954 @findex SYMBOL_TYPES_DOMAIN
21955 @findex gdb.SYMBOL_TYPES_DOMAIN
21956 @item SYMBOL_TYPES_DOMAIN
21957 This domain contains all types.
21960 The available address class categories in @code{gdb.Symbol} are represented
21961 as constants in the @code{gdb} module:
21964 @findex SYMBOL_LOC_UNDEF
21965 @findex gdb.SYMBOL_LOC_UNDEF
21966 @item SYMBOL_LOC_UNDEF
21967 If this is returned by address class, it indicates an error either in
21968 the symbol information or in @value{GDBN}'s handling of symbols.
21969 @findex SYMBOL_LOC_CONST
21970 @findex gdb.SYMBOL_LOC_CONST
21971 @item SYMBOL_LOC_CONST
21972 Value is constant int.
21973 @findex SYMBOL_LOC_STATIC
21974 @findex gdb.SYMBOL_LOC_STATIC
21975 @item SYMBOL_LOC_STATIC
21976 Value is at a fixed address.
21977 @findex SYMBOL_LOC_REGISTER
21978 @findex gdb.SYMBOL_LOC_REGISTER
21979 @item SYMBOL_LOC_REGISTER
21980 Value is in a register.
21981 @findex SYMBOL_LOC_ARG
21982 @findex gdb.SYMBOL_LOC_ARG
21983 @item SYMBOL_LOC_ARG
21984 Value is an argument. This value is at the offset stored within the
21985 symbol inside the frame's argument list.
21986 @findex SYMBOL_LOC_REF_ARG
21987 @findex gdb.SYMBOL_LOC_REF_ARG
21988 @item SYMBOL_LOC_REF_ARG
21989 Value address is stored in the frame's argument list. Just like
21990 @code{LOC_ARG} except that the value's address is stored at the
21991 offset, not the value itself.
21992 @findex SYMBOL_LOC_REGPARM_ADDR
21993 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21994 @item SYMBOL_LOC_REGPARM_ADDR
21995 Value is a specified register. Just like @code{LOC_REGISTER} except
21996 the register holds the address of the argument instead of the argument
21998 @findex SYMBOL_LOC_LOCAL
21999 @findex gdb.SYMBOL_LOC_LOCAL
22000 @item SYMBOL_LOC_LOCAL
22001 Value is a local variable.
22002 @findex SYMBOL_LOC_TYPEDEF
22003 @findex gdb.SYMBOL_LOC_TYPEDEF
22004 @item SYMBOL_LOC_TYPEDEF
22005 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22007 @findex SYMBOL_LOC_BLOCK
22008 @findex gdb.SYMBOL_LOC_BLOCK
22009 @item SYMBOL_LOC_BLOCK
22011 @findex SYMBOL_LOC_CONST_BYTES
22012 @findex gdb.SYMBOL_LOC_CONST_BYTES
22013 @item SYMBOL_LOC_CONST_BYTES
22014 Value is a byte-sequence.
22015 @findex SYMBOL_LOC_UNRESOLVED
22016 @findex gdb.SYMBOL_LOC_UNRESOLVED
22017 @item SYMBOL_LOC_UNRESOLVED
22018 Value is at a fixed address, but the address of the variable has to be
22019 determined from the minimal symbol table whenever the variable is
22021 @findex SYMBOL_LOC_OPTIMIZED_OUT
22022 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22023 @item SYMBOL_LOC_OPTIMIZED_OUT
22024 The value does not actually exist in the program.
22025 @findex SYMBOL_LOC_COMPUTED
22026 @findex gdb.SYMBOL_LOC_COMPUTED
22027 @item SYMBOL_LOC_COMPUTED
22028 The value's address is a computed location.
22031 @node Symbol Tables In Python
22032 @subsubsection Symbol table representation in Python.
22034 @cindex symbol tables in python
22036 @tindex gdb.Symtab_and_line
22038 Access to symbol table data maintained by @value{GDBN} on the inferior
22039 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22040 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22041 from the @code{find_sal} method in @code{gdb.Frame} object.
22042 @xref{Frames In Python}.
22044 For more information on @value{GDBN}'s symbol table management, see
22045 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22047 A @code{gdb.Symtab_and_line} object has the following attributes:
22050 @defivar Symtab_and_line symtab
22051 The symbol table object (@code{gdb.Symtab}) for this frame.
22052 This attribute is not writable.
22055 @defivar Symtab_and_line pc
22056 Indicates the current program counter address. This attribute is not
22060 @defivar Symtab_and_line line
22061 Indicates the current line number for this object. This
22062 attribute is not writable.
22066 A @code{gdb.Symtab} object has the following attributes:
22069 @defivar Symtab filename
22070 The symbol table's source filename. This attribute is not writable.
22073 @defivar Symtab objfile
22074 The symbol table's backing object file. @xref{Objfiles In Python}.
22075 This attribute is not writable.
22079 The following methods are provided:
22082 @defmethod Symtab fullname
22083 Return the symbol table's source absolute file name.
22087 @node Breakpoints In Python
22088 @subsubsection Manipulating breakpoints using Python
22090 @cindex breakpoints in python
22091 @tindex gdb.Breakpoint
22093 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22096 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22097 Create a new breakpoint. @var{spec} is a string naming the
22098 location of the breakpoint, or an expression that defines a
22099 watchpoint. The contents can be any location recognized by the
22100 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22101 command. The optional @var{type} denotes the breakpoint to create
22102 from the types defined later in this chapter. This argument can be
22103 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22104 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22105 argument defines the class of watchpoint to create, if @var{type} is
22106 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22107 provided, it is assumed to be a @var{WP_WRITE} class.
22110 The available watchpoint types represented by constants are defined in the
22115 @findex gdb.WP_READ
22117 Read only watchpoint.
22120 @findex gdb.WP_WRITE
22122 Write only watchpoint.
22125 @findex gdb.WP_ACCESS
22127 Read/Write watchpoint.
22130 @defmethod Breakpoint is_valid
22131 Return @code{True} if this @code{Breakpoint} object is valid,
22132 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22133 if the user deletes the breakpoint. In this case, the object still
22134 exists, but the underlying breakpoint does not. In the cases of
22135 watchpoint scope, the watchpoint remains valid even if execution of the
22136 inferior leaves the scope of that watchpoint.
22139 @defivar Breakpoint enabled
22140 This attribute is @code{True} if the breakpoint is enabled, and
22141 @code{False} otherwise. This attribute is writable.
22144 @defivar Breakpoint silent
22145 This attribute is @code{True} if the breakpoint is silent, and
22146 @code{False} otherwise. This attribute is writable.
22148 Note that a breakpoint can also be silent if it has commands and the
22149 first command is @code{silent}. This is not reported by the
22150 @code{silent} attribute.
22153 @defivar Breakpoint thread
22154 If the breakpoint is thread-specific, this attribute holds the thread
22155 id. If the breakpoint is not thread-specific, this attribute is
22156 @code{None}. This attribute is writable.
22159 @defivar Breakpoint task
22160 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22161 id. If the breakpoint is not task-specific (or the underlying
22162 language is not Ada), this attribute is @code{None}. This attribute
22166 @defivar Breakpoint ignore_count
22167 This attribute holds the ignore count for the breakpoint, an integer.
22168 This attribute is writable.
22171 @defivar Breakpoint number
22172 This attribute holds the breakpoint's number --- the identifier used by
22173 the user to manipulate the breakpoint. This attribute is not writable.
22176 @defivar Breakpoint type
22177 This attribute holds the breakpoint's type --- the identifier used to
22178 determine the actual breakpoint type or use-case. This attribute is not
22182 The available types are represented by constants defined in the @code{gdb}
22186 @findex BP_BREAKPOINT
22187 @findex gdb.BP_BREAKPOINT
22188 @item BP_BREAKPOINT
22189 Normal code breakpoint.
22191 @findex BP_WATCHPOINT
22192 @findex gdb.BP_WATCHPOINT
22193 @item BP_WATCHPOINT
22194 Watchpoint breakpoint.
22196 @findex BP_HARDWARE_WATCHPOINT
22197 @findex gdb.BP_HARDWARE_WATCHPOINT
22198 @item BP_HARDWARE_WATCHPOINT
22199 Hardware assisted watchpoint.
22201 @findex BP_READ_WATCHPOINT
22202 @findex gdb.BP_READ_WATCHPOINT
22203 @item BP_READ_WATCHPOINT
22204 Hardware assisted read watchpoint.
22206 @findex BP_ACCESS_WATCHPOINT
22207 @findex gdb.BP_ACCESS_WATCHPOINT
22208 @item BP_ACCESS_WATCHPOINT
22209 Hardware assisted access watchpoint.
22212 @defivar Breakpoint hit_count
22213 This attribute holds the hit count for the breakpoint, an integer.
22214 This attribute is writable, but currently it can only be set to zero.
22217 @defivar Breakpoint location
22218 This attribute holds the location of the breakpoint, as specified by
22219 the user. It is a string. If the breakpoint does not have a location
22220 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22221 attribute is not writable.
22224 @defivar Breakpoint expression
22225 This attribute holds a breakpoint expression, as specified by
22226 the user. It is a string. If the breakpoint does not have an
22227 expression (the breakpoint is not a watchpoint) the attribute's value
22228 is @code{None}. This attribute is not writable.
22231 @defivar Breakpoint condition
22232 This attribute holds the condition of the breakpoint, as specified by
22233 the user. It is a string. If there is no condition, this attribute's
22234 value is @code{None}. This attribute is writable.
22237 @defivar Breakpoint commands
22238 This attribute holds the commands attached to the breakpoint. If
22239 there are commands, this attribute's value is a string holding all the
22240 commands, separated by newlines. If there are no commands, this
22241 attribute is @code{None}. This attribute is not writable.
22244 @node Lazy Strings In Python
22245 @subsubsection Python representation of lazy strings.
22247 @cindex lazy strings in python
22248 @tindex gdb.LazyString
22250 A @dfn{lazy string} is a string whose contents is not retrieved or
22251 encoded until it is needed.
22253 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22254 @code{address} that points to a region of memory, an @code{encoding}
22255 that will be used to encode that region of memory, and a @code{length}
22256 to delimit the region of memory that represents the string. The
22257 difference between a @code{gdb.LazyString} and a string wrapped within
22258 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22259 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22260 retrieved and encoded during printing, while a @code{gdb.Value}
22261 wrapping a string is immediately retrieved and encoded on creation.
22263 A @code{gdb.LazyString} object has the following functions:
22265 @defmethod LazyString value
22266 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22267 will point to the string in memory, but will lose all the delayed
22268 retrieval, encoding and handling that @value{GDBN} applies to a
22269 @code{gdb.LazyString}.
22272 @defivar LazyString address
22273 This attribute holds the address of the string. This attribute is not
22277 @defivar LazyString length
22278 This attribute holds the length of the string in characters. If the
22279 length is -1, then the string will be fetched and encoded up to the
22280 first null of appropriate width. This attribute is not writable.
22283 @defivar LazyString encoding
22284 This attribute holds the encoding that will be applied to the string
22285 when the string is printed by @value{GDBN}. If the encoding is not
22286 set, or contains an empty string, then @value{GDBN} will select the
22287 most appropriate encoding when the string is printed. This attribute
22291 @defivar LazyString type
22292 This attribute holds the type that is represented by the lazy string's
22293 type. For a lazy string this will always be a pointer type. To
22294 resolve this to the lazy string's character type, use the type's
22295 @code{target} method. @xref{Types In Python}. This attribute is not
22300 @subsection Auto-loading
22301 @cindex auto-loading, Python
22303 When a new object file is read (for example, due to the @code{file}
22304 command, or because the inferior has loaded a shared library),
22305 @value{GDBN} will look for Python support scripts in several ways:
22306 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22309 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22310 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22311 * Which flavor to choose?::
22314 The auto-loading feature is useful for supplying application-specific
22315 debugging commands and scripts.
22317 Auto-loading can be enabled or disabled.
22320 @kindex maint set python auto-load
22321 @item maint set python auto-load [yes|no]
22322 Enable or disable the Python auto-loading feature.
22324 @kindex maint show python auto-load
22325 @item maint show python auto-load
22326 Show whether Python auto-loading is enabled or disabled.
22329 When reading an auto-loaded file, @value{GDBN} sets the
22330 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22331 function (@pxref{Objfiles In Python}). This can be useful for
22332 registering objfile-specific pretty-printers.
22334 @node objfile-gdb.py file
22335 @subsubsection The @file{@var{objfile}-gdb.py} file
22336 @cindex @file{@var{objfile}-gdb.py}
22338 When a new object file is read, @value{GDBN} looks for
22339 a file named @file{@var{objfile}-gdb.py},
22340 where @var{objfile} is the object file's real name, formed by ensuring
22341 that the file name is absolute, following all symlinks, and resolving
22342 @code{.} and @code{..} components. If this file exists and is
22343 readable, @value{GDBN} will evaluate it as a Python script.
22345 If this file does not exist, and if the parameter
22346 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22347 then @value{GDBN} will look for @var{real-name} in all of the
22348 directories mentioned in the value of @code{debug-file-directory}.
22350 Finally, if this file does not exist, then @value{GDBN} will look for
22351 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22352 @var{data-directory} is @value{GDBN}'s data directory (available via
22353 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22354 is the object file's real name, as described above.
22356 @value{GDBN} does not track which files it has already auto-loaded this way.
22357 @value{GDBN} will load the associated script every time the corresponding
22358 @var{objfile} is opened.
22359 So your @file{-gdb.py} file should be careful to avoid errors if it
22360 is evaluated more than once.
22362 @node .debug_gdb_scripts section
22363 @subsubsection The @code{.debug_gdb_scripts} section
22364 @cindex @code{.debug_gdb_scripts} section
22366 For systems using file formats like ELF and COFF,
22367 when @value{GDBN} loads a new object file
22368 it will look for a special section named @samp{.debug_gdb_scripts}.
22369 If this section exists, its contents is a list of names of scripts to load.
22371 @value{GDBN} will look for each specified script file first in the
22372 current directory and then along the source search path
22373 (@pxref{Source Path, ,Specifying Source Directories}),
22374 except that @file{$cdir} is not searched, since the compilation
22375 directory is not relevant to scripts.
22377 Entries can be placed in section @code{.debug_gdb_scripts} with,
22378 for example, this GCC macro:
22381 /* Note: The "MS" section flags are to remote duplicates. */
22382 #define DEFINE_GDB_SCRIPT(script_name) \
22384 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22386 .asciz \"" script_name "\"\n\
22392 Then one can reference the macro in a header or source file like this:
22395 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22398 The script name may include directories if desired.
22400 If the macro is put in a header, any application or library
22401 using this header will get a reference to the specified script.
22403 @node Which flavor to choose?
22404 @subsubsection Which flavor to choose?
22406 Given the multiple ways of auto-loading Python scripts, it might not always
22407 be clear which one to choose. This section provides some guidance.
22409 Benefits of the @file{-gdb.py} way:
22413 Can be used with file formats that don't support multiple sections.
22416 Ease of finding scripts for public libraries.
22418 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22419 in the source search path.
22420 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22421 isn't a source directory in which to find the script.
22424 Doesn't require source code additions.
22427 Benefits of the @code{.debug_gdb_scripts} way:
22431 Works with static linking.
22433 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22434 trigger their loading. When an application is statically linked the only
22435 objfile available is the executable, and it is cumbersome to attach all the
22436 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22439 Works with classes that are entirely inlined.
22441 Some classes can be entirely inlined, and thus there may not be an associated
22442 shared library to attach a @file{-gdb.py} script to.
22445 Scripts needn't be copied out of the source tree.
22447 In some circumstances, apps can be built out of large collections of internal
22448 libraries, and the build infrastructure necessary to install the
22449 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22450 cumbersome. It may be easier to specify the scripts in the
22451 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22452 top of the source tree to the source search path.
22456 @chapter Command Interpreters
22457 @cindex command interpreters
22459 @value{GDBN} supports multiple command interpreters, and some command
22460 infrastructure to allow users or user interface writers to switch
22461 between interpreters or run commands in other interpreters.
22463 @value{GDBN} currently supports two command interpreters, the console
22464 interpreter (sometimes called the command-line interpreter or @sc{cli})
22465 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22466 describes both of these interfaces in great detail.
22468 By default, @value{GDBN} will start with the console interpreter.
22469 However, the user may choose to start @value{GDBN} with another
22470 interpreter by specifying the @option{-i} or @option{--interpreter}
22471 startup options. Defined interpreters include:
22475 @cindex console interpreter
22476 The traditional console or command-line interpreter. This is the most often
22477 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22478 @value{GDBN} will use this interpreter.
22481 @cindex mi interpreter
22482 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22483 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22484 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22488 @cindex mi2 interpreter
22489 The current @sc{gdb/mi} interface.
22492 @cindex mi1 interpreter
22493 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22497 @cindex invoke another interpreter
22498 The interpreter being used by @value{GDBN} may not be dynamically
22499 switched at runtime. Although possible, this could lead to a very
22500 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22501 enters the command "interpreter-set console" in a console view,
22502 @value{GDBN} would switch to using the console interpreter, rendering
22503 the IDE inoperable!
22505 @kindex interpreter-exec
22506 Although you may only choose a single interpreter at startup, you may execute
22507 commands in any interpreter from the current interpreter using the appropriate
22508 command. If you are running the console interpreter, simply use the
22509 @code{interpreter-exec} command:
22512 interpreter-exec mi "-data-list-register-names"
22515 @sc{gdb/mi} has a similar command, although it is only available in versions of
22516 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22519 @chapter @value{GDBN} Text User Interface
22521 @cindex Text User Interface
22524 * TUI Overview:: TUI overview
22525 * TUI Keys:: TUI key bindings
22526 * TUI Single Key Mode:: TUI single key mode
22527 * TUI Commands:: TUI-specific commands
22528 * TUI Configuration:: TUI configuration variables
22531 The @value{GDBN} Text User Interface (TUI) is a terminal
22532 interface which uses the @code{curses} library to show the source
22533 file, the assembly output, the program registers and @value{GDBN}
22534 commands in separate text windows. The TUI mode is supported only
22535 on platforms where a suitable version of the @code{curses} library
22538 @pindex @value{GDBTUI}
22539 The TUI mode is enabled by default when you invoke @value{GDBN} as
22540 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22541 You can also switch in and out of TUI mode while @value{GDBN} runs by
22542 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22543 @xref{TUI Keys, ,TUI Key Bindings}.
22546 @section TUI Overview
22548 In TUI mode, @value{GDBN} can display several text windows:
22552 This window is the @value{GDBN} command window with the @value{GDBN}
22553 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22554 managed using readline.
22557 The source window shows the source file of the program. The current
22558 line and active breakpoints are displayed in this window.
22561 The assembly window shows the disassembly output of the program.
22564 This window shows the processor registers. Registers are highlighted
22565 when their values change.
22568 The source and assembly windows show the current program position
22569 by highlighting the current line and marking it with a @samp{>} marker.
22570 Breakpoints are indicated with two markers. The first marker
22571 indicates the breakpoint type:
22575 Breakpoint which was hit at least once.
22578 Breakpoint which was never hit.
22581 Hardware breakpoint which was hit at least once.
22584 Hardware breakpoint which was never hit.
22587 The second marker indicates whether the breakpoint is enabled or not:
22591 Breakpoint is enabled.
22594 Breakpoint is disabled.
22597 The source, assembly and register windows are updated when the current
22598 thread changes, when the frame changes, or when the program counter
22601 These windows are not all visible at the same time. The command
22602 window is always visible. The others can be arranged in several
22613 source and assembly,
22616 source and registers, or
22619 assembly and registers.
22622 A status line above the command window shows the following information:
22626 Indicates the current @value{GDBN} target.
22627 (@pxref{Targets, ,Specifying a Debugging Target}).
22630 Gives the current process or thread number.
22631 When no process is being debugged, this field is set to @code{No process}.
22634 Gives the current function name for the selected frame.
22635 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22636 When there is no symbol corresponding to the current program counter,
22637 the string @code{??} is displayed.
22640 Indicates the current line number for the selected frame.
22641 When the current line number is not known, the string @code{??} is displayed.
22644 Indicates the current program counter address.
22648 @section TUI Key Bindings
22649 @cindex TUI key bindings
22651 The TUI installs several key bindings in the readline keymaps
22652 (@pxref{Command Line Editing}). The following key bindings
22653 are installed for both TUI mode and the @value{GDBN} standard mode.
22662 Enter or leave the TUI mode. When leaving the TUI mode,
22663 the curses window management stops and @value{GDBN} operates using
22664 its standard mode, writing on the terminal directly. When reentering
22665 the TUI mode, control is given back to the curses windows.
22666 The screen is then refreshed.
22670 Use a TUI layout with only one window. The layout will
22671 either be @samp{source} or @samp{assembly}. When the TUI mode
22672 is not active, it will switch to the TUI mode.
22674 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22678 Use a TUI layout with at least two windows. When the current
22679 layout already has two windows, the next layout with two windows is used.
22680 When a new layout is chosen, one window will always be common to the
22681 previous layout and the new one.
22683 Think of it as the Emacs @kbd{C-x 2} binding.
22687 Change the active window. The TUI associates several key bindings
22688 (like scrolling and arrow keys) with the active window. This command
22689 gives the focus to the next TUI window.
22691 Think of it as the Emacs @kbd{C-x o} binding.
22695 Switch in and out of the TUI SingleKey mode that binds single
22696 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22699 The following key bindings only work in the TUI mode:
22704 Scroll the active window one page up.
22708 Scroll the active window one page down.
22712 Scroll the active window one line up.
22716 Scroll the active window one line down.
22720 Scroll the active window one column left.
22724 Scroll the active window one column right.
22728 Refresh the screen.
22731 Because the arrow keys scroll the active window in the TUI mode, they
22732 are not available for their normal use by readline unless the command
22733 window has the focus. When another window is active, you must use
22734 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22735 and @kbd{C-f} to control the command window.
22737 @node TUI Single Key Mode
22738 @section TUI Single Key Mode
22739 @cindex TUI single key mode
22741 The TUI also provides a @dfn{SingleKey} mode, which binds several
22742 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22743 switch into this mode, where the following key bindings are used:
22746 @kindex c @r{(SingleKey TUI key)}
22750 @kindex d @r{(SingleKey TUI key)}
22754 @kindex f @r{(SingleKey TUI key)}
22758 @kindex n @r{(SingleKey TUI key)}
22762 @kindex q @r{(SingleKey TUI key)}
22764 exit the SingleKey mode.
22766 @kindex r @r{(SingleKey TUI key)}
22770 @kindex s @r{(SingleKey TUI key)}
22774 @kindex u @r{(SingleKey TUI key)}
22778 @kindex v @r{(SingleKey TUI key)}
22782 @kindex w @r{(SingleKey TUI key)}
22787 Other keys temporarily switch to the @value{GDBN} command prompt.
22788 The key that was pressed is inserted in the editing buffer so that
22789 it is possible to type most @value{GDBN} commands without interaction
22790 with the TUI SingleKey mode. Once the command is entered the TUI
22791 SingleKey mode is restored. The only way to permanently leave
22792 this mode is by typing @kbd{q} or @kbd{C-x s}.
22796 @section TUI-specific Commands
22797 @cindex TUI commands
22799 The TUI has specific commands to control the text windows.
22800 These commands are always available, even when @value{GDBN} is not in
22801 the TUI mode. When @value{GDBN} is in the standard mode, most
22802 of these commands will automatically switch to the TUI mode.
22804 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22805 terminal, or @value{GDBN} has been started with the machine interface
22806 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22807 these commands will fail with an error, because it would not be
22808 possible or desirable to enable curses window management.
22813 List and give the size of all displayed windows.
22817 Display the next layout.
22820 Display the previous layout.
22823 Display the source window only.
22826 Display the assembly window only.
22829 Display the source and assembly window.
22832 Display the register window together with the source or assembly window.
22836 Make the next window active for scrolling.
22839 Make the previous window active for scrolling.
22842 Make the source window active for scrolling.
22845 Make the assembly window active for scrolling.
22848 Make the register window active for scrolling.
22851 Make the command window active for scrolling.
22855 Refresh the screen. This is similar to typing @kbd{C-L}.
22857 @item tui reg float
22859 Show the floating point registers in the register window.
22861 @item tui reg general
22862 Show the general registers in the register window.
22865 Show the next register group. The list of register groups as well as
22866 their order is target specific. The predefined register groups are the
22867 following: @code{general}, @code{float}, @code{system}, @code{vector},
22868 @code{all}, @code{save}, @code{restore}.
22870 @item tui reg system
22871 Show the system registers in the register window.
22875 Update the source window and the current execution point.
22877 @item winheight @var{name} +@var{count}
22878 @itemx winheight @var{name} -@var{count}
22880 Change the height of the window @var{name} by @var{count}
22881 lines. Positive counts increase the height, while negative counts
22884 @item tabset @var{nchars}
22886 Set the width of tab stops to be @var{nchars} characters.
22889 @node TUI Configuration
22890 @section TUI Configuration Variables
22891 @cindex TUI configuration variables
22893 Several configuration variables control the appearance of TUI windows.
22896 @item set tui border-kind @var{kind}
22897 @kindex set tui border-kind
22898 Select the border appearance for the source, assembly and register windows.
22899 The possible values are the following:
22902 Use a space character to draw the border.
22905 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22908 Use the Alternate Character Set to draw the border. The border is
22909 drawn using character line graphics if the terminal supports them.
22912 @item set tui border-mode @var{mode}
22913 @kindex set tui border-mode
22914 @itemx set tui active-border-mode @var{mode}
22915 @kindex set tui active-border-mode
22916 Select the display attributes for the borders of the inactive windows
22917 or the active window. The @var{mode} can be one of the following:
22920 Use normal attributes to display the border.
22926 Use reverse video mode.
22929 Use half bright mode.
22931 @item half-standout
22932 Use half bright and standout mode.
22935 Use extra bright or bold mode.
22937 @item bold-standout
22938 Use extra bright or bold and standout mode.
22943 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22946 @cindex @sc{gnu} Emacs
22947 A special interface allows you to use @sc{gnu} Emacs to view (and
22948 edit) the source files for the program you are debugging with
22951 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22952 executable file you want to debug as an argument. This command starts
22953 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22954 created Emacs buffer.
22955 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22957 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22962 All ``terminal'' input and output goes through an Emacs buffer, called
22965 This applies both to @value{GDBN} commands and their output, and to the input
22966 and output done by the program you are debugging.
22968 This is useful because it means that you can copy the text of previous
22969 commands and input them again; you can even use parts of the output
22972 All the facilities of Emacs' Shell mode are available for interacting
22973 with your program. In particular, you can send signals the usual
22974 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22978 @value{GDBN} displays source code through Emacs.
22980 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22981 source file for that frame and puts an arrow (@samp{=>}) at the
22982 left margin of the current line. Emacs uses a separate buffer for
22983 source display, and splits the screen to show both your @value{GDBN} session
22986 Explicit @value{GDBN} @code{list} or search commands still produce output as
22987 usual, but you probably have no reason to use them from Emacs.
22990 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22991 a graphical mode, enabled by default, which provides further buffers
22992 that can control the execution and describe the state of your program.
22993 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22995 If you specify an absolute file name when prompted for the @kbd{M-x
22996 gdb} argument, then Emacs sets your current working directory to where
22997 your program resides. If you only specify the file name, then Emacs
22998 sets your current working directory to to the directory associated
22999 with the previous buffer. In this case, @value{GDBN} may find your
23000 program by searching your environment's @code{PATH} variable, but on
23001 some operating systems it might not find the source. So, although the
23002 @value{GDBN} input and output session proceeds normally, the auxiliary
23003 buffer does not display the current source and line of execution.
23005 The initial working directory of @value{GDBN} is printed on the top
23006 line of the GUD buffer and this serves as a default for the commands
23007 that specify files for @value{GDBN} to operate on. @xref{Files,
23008 ,Commands to Specify Files}.
23010 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23011 need to call @value{GDBN} by a different name (for example, if you
23012 keep several configurations around, with different names) you can
23013 customize the Emacs variable @code{gud-gdb-command-name} to run the
23016 In the GUD buffer, you can use these special Emacs commands in
23017 addition to the standard Shell mode commands:
23021 Describe the features of Emacs' GUD Mode.
23024 Execute to another source line, like the @value{GDBN} @code{step} command; also
23025 update the display window to show the current file and location.
23028 Execute to next source line in this function, skipping all function
23029 calls, like the @value{GDBN} @code{next} command. Then update the display window
23030 to show the current file and location.
23033 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23034 display window accordingly.
23037 Execute until exit from the selected stack frame, like the @value{GDBN}
23038 @code{finish} command.
23041 Continue execution of your program, like the @value{GDBN} @code{continue}
23045 Go up the number of frames indicated by the numeric argument
23046 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23047 like the @value{GDBN} @code{up} command.
23050 Go down the number of frames indicated by the numeric argument, like the
23051 @value{GDBN} @code{down} command.
23054 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23055 tells @value{GDBN} to set a breakpoint on the source line point is on.
23057 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23058 separate frame which shows a backtrace when the GUD buffer is current.
23059 Move point to any frame in the stack and type @key{RET} to make it
23060 become the current frame and display the associated source in the
23061 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23062 selected frame become the current one. In graphical mode, the
23063 speedbar displays watch expressions.
23065 If you accidentally delete the source-display buffer, an easy way to get
23066 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23067 request a frame display; when you run under Emacs, this recreates
23068 the source buffer if necessary to show you the context of the current
23071 The source files displayed in Emacs are in ordinary Emacs buffers
23072 which are visiting the source files in the usual way. You can edit
23073 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23074 communicates with Emacs in terms of line numbers. If you add or
23075 delete lines from the text, the line numbers that @value{GDBN} knows cease
23076 to correspond properly with the code.
23078 A more detailed description of Emacs' interaction with @value{GDBN} is
23079 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23082 @c The following dropped because Epoch is nonstandard. Reactivate
23083 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23085 @kindex Emacs Epoch environment
23089 Version 18 of @sc{gnu} Emacs has a built-in window system
23090 called the @code{epoch}
23091 environment. Users of this environment can use a new command,
23092 @code{inspect} which performs identically to @code{print} except that
23093 each value is printed in its own window.
23098 @chapter The @sc{gdb/mi} Interface
23100 @unnumberedsec Function and Purpose
23102 @cindex @sc{gdb/mi}, its purpose
23103 @sc{gdb/mi} is a line based machine oriented text interface to
23104 @value{GDBN} and is activated by specifying using the
23105 @option{--interpreter} command line option (@pxref{Mode Options}). It
23106 is specifically intended to support the development of systems which
23107 use the debugger as just one small component of a larger system.
23109 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23110 in the form of a reference manual.
23112 Note that @sc{gdb/mi} is still under construction, so some of the
23113 features described below are incomplete and subject to change
23114 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23116 @unnumberedsec Notation and Terminology
23118 @cindex notational conventions, for @sc{gdb/mi}
23119 This chapter uses the following notation:
23123 @code{|} separates two alternatives.
23126 @code{[ @var{something} ]} indicates that @var{something} is optional:
23127 it may or may not be given.
23130 @code{( @var{group} )*} means that @var{group} inside the parentheses
23131 may repeat zero or more times.
23134 @code{( @var{group} )+} means that @var{group} inside the parentheses
23135 may repeat one or more times.
23138 @code{"@var{string}"} means a literal @var{string}.
23142 @heading Dependencies
23146 * GDB/MI General Design::
23147 * GDB/MI Command Syntax::
23148 * GDB/MI Compatibility with CLI::
23149 * GDB/MI Development and Front Ends::
23150 * GDB/MI Output Records::
23151 * GDB/MI Simple Examples::
23152 * GDB/MI Command Description Format::
23153 * GDB/MI Breakpoint Commands::
23154 * GDB/MI Program Context::
23155 * GDB/MI Thread Commands::
23156 * GDB/MI Program Execution::
23157 * GDB/MI Stack Manipulation::
23158 * GDB/MI Variable Objects::
23159 * GDB/MI Data Manipulation::
23160 * GDB/MI Tracepoint Commands::
23161 * GDB/MI Symbol Query::
23162 * GDB/MI File Commands::
23164 * GDB/MI Kod Commands::
23165 * GDB/MI Memory Overlay Commands::
23166 * GDB/MI Signal Handling Commands::
23168 * GDB/MI Target Manipulation::
23169 * GDB/MI File Transfer Commands::
23170 * GDB/MI Miscellaneous Commands::
23173 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23174 @node GDB/MI General Design
23175 @section @sc{gdb/mi} General Design
23176 @cindex GDB/MI General Design
23178 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23179 parts---commands sent to @value{GDBN}, responses to those commands
23180 and notifications. Each command results in exactly one response,
23181 indicating either successful completion of the command, or an error.
23182 For the commands that do not resume the target, the response contains the
23183 requested information. For the commands that resume the target, the
23184 response only indicates whether the target was successfully resumed.
23185 Notifications is the mechanism for reporting changes in the state of the
23186 target, or in @value{GDBN} state, that cannot conveniently be associated with
23187 a command and reported as part of that command response.
23189 The important examples of notifications are:
23193 Exec notifications. These are used to report changes in
23194 target state---when a target is resumed, or stopped. It would not
23195 be feasible to include this information in response of resuming
23196 commands, because one resume commands can result in multiple events in
23197 different threads. Also, quite some time may pass before any event
23198 happens in the target, while a frontend needs to know whether the resuming
23199 command itself was successfully executed.
23202 Console output, and status notifications. Console output
23203 notifications are used to report output of CLI commands, as well as
23204 diagnostics for other commands. Status notifications are used to
23205 report the progress of a long-running operation. Naturally, including
23206 this information in command response would mean no output is produced
23207 until the command is finished, which is undesirable.
23210 General notifications. Commands may have various side effects on
23211 the @value{GDBN} or target state beyond their official purpose. For example,
23212 a command may change the selected thread. Although such changes can
23213 be included in command response, using notification allows for more
23214 orthogonal frontend design.
23218 There's no guarantee that whenever an MI command reports an error,
23219 @value{GDBN} or the target are in any specific state, and especially,
23220 the state is not reverted to the state before the MI command was
23221 processed. Therefore, whenever an MI command results in an error,
23222 we recommend that the frontend refreshes all the information shown in
23223 the user interface.
23227 * Context management::
23228 * Asynchronous and non-stop modes::
23232 @node Context management
23233 @subsection Context management
23235 In most cases when @value{GDBN} accesses the target, this access is
23236 done in context of a specific thread and frame (@pxref{Frames}).
23237 Often, even when accessing global data, the target requires that a thread
23238 be specified. The CLI interface maintains the selected thread and frame,
23239 and supplies them to target on each command. This is convenient,
23240 because a command line user would not want to specify that information
23241 explicitly on each command, and because user interacts with
23242 @value{GDBN} via a single terminal, so no confusion is possible as
23243 to what thread and frame are the current ones.
23245 In the case of MI, the concept of selected thread and frame is less
23246 useful. First, a frontend can easily remember this information
23247 itself. Second, a graphical frontend can have more than one window,
23248 each one used for debugging a different thread, and the frontend might
23249 want to access additional threads for internal purposes. This
23250 increases the risk that by relying on implicitly selected thread, the
23251 frontend may be operating on a wrong one. Therefore, each MI command
23252 should explicitly specify which thread and frame to operate on. To
23253 make it possible, each MI command accepts the @samp{--thread} and
23254 @samp{--frame} options, the value to each is @value{GDBN} identifier
23255 for thread and frame to operate on.
23257 Usually, each top-level window in a frontend allows the user to select
23258 a thread and a frame, and remembers the user selection for further
23259 operations. However, in some cases @value{GDBN} may suggest that the
23260 current thread be changed. For example, when stopping on a breakpoint
23261 it is reasonable to switch to the thread where breakpoint is hit. For
23262 another example, if the user issues the CLI @samp{thread} command via
23263 the frontend, it is desirable to change the frontend's selected thread to the
23264 one specified by user. @value{GDBN} communicates the suggestion to
23265 change current thread using the @samp{=thread-selected} notification.
23266 No such notification is available for the selected frame at the moment.
23268 Note that historically, MI shares the selected thread with CLI, so
23269 frontends used the @code{-thread-select} to execute commands in the
23270 right context. However, getting this to work right is cumbersome. The
23271 simplest way is for frontend to emit @code{-thread-select} command
23272 before every command. This doubles the number of commands that need
23273 to be sent. The alternative approach is to suppress @code{-thread-select}
23274 if the selected thread in @value{GDBN} is supposed to be identical to the
23275 thread the frontend wants to operate on. However, getting this
23276 optimization right can be tricky. In particular, if the frontend
23277 sends several commands to @value{GDBN}, and one of the commands changes the
23278 selected thread, then the behaviour of subsequent commands will
23279 change. So, a frontend should either wait for response from such
23280 problematic commands, or explicitly add @code{-thread-select} for
23281 all subsequent commands. No frontend is known to do this exactly
23282 right, so it is suggested to just always pass the @samp{--thread} and
23283 @samp{--frame} options.
23285 @node Asynchronous and non-stop modes
23286 @subsection Asynchronous command execution and non-stop mode
23288 On some targets, @value{GDBN} is capable of processing MI commands
23289 even while the target is running. This is called @dfn{asynchronous
23290 command execution} (@pxref{Background Execution}). The frontend may
23291 specify a preferrence for asynchronous execution using the
23292 @code{-gdb-set target-async 1} command, which should be emitted before
23293 either running the executable or attaching to the target. After the
23294 frontend has started the executable or attached to the target, it can
23295 find if asynchronous execution is enabled using the
23296 @code{-list-target-features} command.
23298 Even if @value{GDBN} can accept a command while target is running,
23299 many commands that access the target do not work when the target is
23300 running. Therefore, asynchronous command execution is most useful
23301 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23302 it is possible to examine the state of one thread, while other threads
23305 When a given thread is running, MI commands that try to access the
23306 target in the context of that thread may not work, or may work only on
23307 some targets. In particular, commands that try to operate on thread's
23308 stack will not work, on any target. Commands that read memory, or
23309 modify breakpoints, may work or not work, depending on the target. Note
23310 that even commands that operate on global state, such as @code{print},
23311 @code{set}, and breakpoint commands, still access the target in the
23312 context of a specific thread, so frontend should try to find a
23313 stopped thread and perform the operation on that thread (using the
23314 @samp{--thread} option).
23316 Which commands will work in the context of a running thread is
23317 highly target dependent. However, the two commands
23318 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23319 to find the state of a thread, will always work.
23321 @node Thread groups
23322 @subsection Thread groups
23323 @value{GDBN} may be used to debug several processes at the same time.
23324 On some platfroms, @value{GDBN} may support debugging of several
23325 hardware systems, each one having several cores with several different
23326 processes running on each core. This section describes the MI
23327 mechanism to support such debugging scenarios.
23329 The key observation is that regardless of the structure of the
23330 target, MI can have a global list of threads, because most commands that
23331 accept the @samp{--thread} option do not need to know what process that
23332 thread belongs to. Therefore, it is not necessary to introduce
23333 neither additional @samp{--process} option, nor an notion of the
23334 current process in the MI interface. The only strictly new feature
23335 that is required is the ability to find how the threads are grouped
23338 To allow the user to discover such grouping, and to support arbitrary
23339 hierarchy of machines/cores/processes, MI introduces the concept of a
23340 @dfn{thread group}. Thread group is a collection of threads and other
23341 thread groups. A thread group always has a string identifier, a type,
23342 and may have additional attributes specific to the type. A new
23343 command, @code{-list-thread-groups}, returns the list of top-level
23344 thread groups, which correspond to processes that @value{GDBN} is
23345 debugging at the moment. By passing an identifier of a thread group
23346 to the @code{-list-thread-groups} command, it is possible to obtain
23347 the members of specific thread group.
23349 To allow the user to easily discover processes, and other objects, he
23350 wishes to debug, a concept of @dfn{available thread group} is
23351 introduced. Available thread group is an thread group that
23352 @value{GDBN} is not debugging, but that can be attached to, using the
23353 @code{-target-attach} command. The list of available top-level thread
23354 groups can be obtained using @samp{-list-thread-groups --available}.
23355 In general, the content of a thread group may be only retrieved only
23356 after attaching to that thread group.
23358 Thread groups are related to inferiors (@pxref{Inferiors and
23359 Programs}). Each inferior corresponds to a thread group of a special
23360 type @samp{process}, and some additional operations are permitted on
23361 such thread groups.
23363 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23364 @node GDB/MI Command Syntax
23365 @section @sc{gdb/mi} Command Syntax
23368 * GDB/MI Input Syntax::
23369 * GDB/MI Output Syntax::
23372 @node GDB/MI Input Syntax
23373 @subsection @sc{gdb/mi} Input Syntax
23375 @cindex input syntax for @sc{gdb/mi}
23376 @cindex @sc{gdb/mi}, input syntax
23378 @item @var{command} @expansion{}
23379 @code{@var{cli-command} | @var{mi-command}}
23381 @item @var{cli-command} @expansion{}
23382 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23383 @var{cli-command} is any existing @value{GDBN} CLI command.
23385 @item @var{mi-command} @expansion{}
23386 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23387 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23389 @item @var{token} @expansion{}
23390 "any sequence of digits"
23392 @item @var{option} @expansion{}
23393 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23395 @item @var{parameter} @expansion{}
23396 @code{@var{non-blank-sequence} | @var{c-string}}
23398 @item @var{operation} @expansion{}
23399 @emph{any of the operations described in this chapter}
23401 @item @var{non-blank-sequence} @expansion{}
23402 @emph{anything, provided it doesn't contain special characters such as
23403 "-", @var{nl}, """ and of course " "}
23405 @item @var{c-string} @expansion{}
23406 @code{""" @var{seven-bit-iso-c-string-content} """}
23408 @item @var{nl} @expansion{}
23417 The CLI commands are still handled by the @sc{mi} interpreter; their
23418 output is described below.
23421 The @code{@var{token}}, when present, is passed back when the command
23425 Some @sc{mi} commands accept optional arguments as part of the parameter
23426 list. Each option is identified by a leading @samp{-} (dash) and may be
23427 followed by an optional argument parameter. Options occur first in the
23428 parameter list and can be delimited from normal parameters using
23429 @samp{--} (this is useful when some parameters begin with a dash).
23436 We want easy access to the existing CLI syntax (for debugging).
23439 We want it to be easy to spot a @sc{mi} operation.
23442 @node GDB/MI Output Syntax
23443 @subsection @sc{gdb/mi} Output Syntax
23445 @cindex output syntax of @sc{gdb/mi}
23446 @cindex @sc{gdb/mi}, output syntax
23447 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23448 followed, optionally, by a single result record. This result record
23449 is for the most recent command. The sequence of output records is
23450 terminated by @samp{(gdb)}.
23452 If an input command was prefixed with a @code{@var{token}} then the
23453 corresponding output for that command will also be prefixed by that same
23457 @item @var{output} @expansion{}
23458 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23460 @item @var{result-record} @expansion{}
23461 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23463 @item @var{out-of-band-record} @expansion{}
23464 @code{@var{async-record} | @var{stream-record}}
23466 @item @var{async-record} @expansion{}
23467 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23469 @item @var{exec-async-output} @expansion{}
23470 @code{[ @var{token} ] "*" @var{async-output}}
23472 @item @var{status-async-output} @expansion{}
23473 @code{[ @var{token} ] "+" @var{async-output}}
23475 @item @var{notify-async-output} @expansion{}
23476 @code{[ @var{token} ] "=" @var{async-output}}
23478 @item @var{async-output} @expansion{}
23479 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23481 @item @var{result-class} @expansion{}
23482 @code{"done" | "running" | "connected" | "error" | "exit"}
23484 @item @var{async-class} @expansion{}
23485 @code{"stopped" | @var{others}} (where @var{others} will be added
23486 depending on the needs---this is still in development).
23488 @item @var{result} @expansion{}
23489 @code{ @var{variable} "=" @var{value}}
23491 @item @var{variable} @expansion{}
23492 @code{ @var{string} }
23494 @item @var{value} @expansion{}
23495 @code{ @var{const} | @var{tuple} | @var{list} }
23497 @item @var{const} @expansion{}
23498 @code{@var{c-string}}
23500 @item @var{tuple} @expansion{}
23501 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23503 @item @var{list} @expansion{}
23504 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23505 @var{result} ( "," @var{result} )* "]" }
23507 @item @var{stream-record} @expansion{}
23508 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23510 @item @var{console-stream-output} @expansion{}
23511 @code{"~" @var{c-string}}
23513 @item @var{target-stream-output} @expansion{}
23514 @code{"@@" @var{c-string}}
23516 @item @var{log-stream-output} @expansion{}
23517 @code{"&" @var{c-string}}
23519 @item @var{nl} @expansion{}
23522 @item @var{token} @expansion{}
23523 @emph{any sequence of digits}.
23531 All output sequences end in a single line containing a period.
23534 The @code{@var{token}} is from the corresponding request. Note that
23535 for all async output, while the token is allowed by the grammar and
23536 may be output by future versions of @value{GDBN} for select async
23537 output messages, it is generally omitted. Frontends should treat
23538 all async output as reporting general changes in the state of the
23539 target and there should be no need to associate async output to any
23543 @cindex status output in @sc{gdb/mi}
23544 @var{status-async-output} contains on-going status information about the
23545 progress of a slow operation. It can be discarded. All status output is
23546 prefixed by @samp{+}.
23549 @cindex async output in @sc{gdb/mi}
23550 @var{exec-async-output} contains asynchronous state change on the target
23551 (stopped, started, disappeared). All async output is prefixed by
23555 @cindex notify output in @sc{gdb/mi}
23556 @var{notify-async-output} contains supplementary information that the
23557 client should handle (e.g., a new breakpoint information). All notify
23558 output is prefixed by @samp{=}.
23561 @cindex console output in @sc{gdb/mi}
23562 @var{console-stream-output} is output that should be displayed as is in the
23563 console. It is the textual response to a CLI command. All the console
23564 output is prefixed by @samp{~}.
23567 @cindex target output in @sc{gdb/mi}
23568 @var{target-stream-output} is the output produced by the target program.
23569 All the target output is prefixed by @samp{@@}.
23572 @cindex log output in @sc{gdb/mi}
23573 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23574 instance messages that should be displayed as part of an error log. All
23575 the log output is prefixed by @samp{&}.
23578 @cindex list output in @sc{gdb/mi}
23579 New @sc{gdb/mi} commands should only output @var{lists} containing
23585 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23586 details about the various output records.
23588 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23589 @node GDB/MI Compatibility with CLI
23590 @section @sc{gdb/mi} Compatibility with CLI
23592 @cindex compatibility, @sc{gdb/mi} and CLI
23593 @cindex @sc{gdb/mi}, compatibility with CLI
23595 For the developers convenience CLI commands can be entered directly,
23596 but there may be some unexpected behaviour. For example, commands
23597 that query the user will behave as if the user replied yes, breakpoint
23598 command lists are not executed and some CLI commands, such as
23599 @code{if}, @code{when} and @code{define}, prompt for further input with
23600 @samp{>}, which is not valid MI output.
23602 This feature may be removed at some stage in the future and it is
23603 recommended that front ends use the @code{-interpreter-exec} command
23604 (@pxref{-interpreter-exec}).
23606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23607 @node GDB/MI Development and Front Ends
23608 @section @sc{gdb/mi} Development and Front Ends
23609 @cindex @sc{gdb/mi} development
23611 The application which takes the MI output and presents the state of the
23612 program being debugged to the user is called a @dfn{front end}.
23614 Although @sc{gdb/mi} is still incomplete, it is currently being used
23615 by a variety of front ends to @value{GDBN}. This makes it difficult
23616 to introduce new functionality without breaking existing usage. This
23617 section tries to minimize the problems by describing how the protocol
23620 Some changes in MI need not break a carefully designed front end, and
23621 for these the MI version will remain unchanged. The following is a
23622 list of changes that may occur within one level, so front ends should
23623 parse MI output in a way that can handle them:
23627 New MI commands may be added.
23630 New fields may be added to the output of any MI command.
23633 The range of values for fields with specified values, e.g.,
23634 @code{in_scope} (@pxref{-var-update}) may be extended.
23636 @c The format of field's content e.g type prefix, may change so parse it
23637 @c at your own risk. Yes, in general?
23639 @c The order of fields may change? Shouldn't really matter but it might
23640 @c resolve inconsistencies.
23643 If the changes are likely to break front ends, the MI version level
23644 will be increased by one. This will allow the front end to parse the
23645 output according to the MI version. Apart from mi0, new versions of
23646 @value{GDBN} will not support old versions of MI and it will be the
23647 responsibility of the front end to work with the new one.
23649 @c Starting with mi3, add a new command -mi-version that prints the MI
23652 The best way to avoid unexpected changes in MI that might break your front
23653 end is to make your project known to @value{GDBN} developers and
23654 follow development on @email{gdb@@sourceware.org} and
23655 @email{gdb-patches@@sourceware.org}.
23656 @cindex mailing lists
23658 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23659 @node GDB/MI Output Records
23660 @section @sc{gdb/mi} Output Records
23663 * GDB/MI Result Records::
23664 * GDB/MI Stream Records::
23665 * GDB/MI Async Records::
23666 * GDB/MI Frame Information::
23667 * GDB/MI Thread Information::
23670 @node GDB/MI Result Records
23671 @subsection @sc{gdb/mi} Result Records
23673 @cindex result records in @sc{gdb/mi}
23674 @cindex @sc{gdb/mi}, result records
23675 In addition to a number of out-of-band notifications, the response to a
23676 @sc{gdb/mi} command includes one of the following result indications:
23680 @item "^done" [ "," @var{results} ]
23681 The synchronous operation was successful, @code{@var{results}} are the return
23686 This result record is equivalent to @samp{^done}. Historically, it
23687 was output instead of @samp{^done} if the command has resumed the
23688 target. This behaviour is maintained for backward compatibility, but
23689 all frontends should treat @samp{^done} and @samp{^running}
23690 identically and rely on the @samp{*running} output record to determine
23691 which threads are resumed.
23695 @value{GDBN} has connected to a remote target.
23697 @item "^error" "," @var{c-string}
23699 The operation failed. The @code{@var{c-string}} contains the corresponding
23704 @value{GDBN} has terminated.
23708 @node GDB/MI Stream Records
23709 @subsection @sc{gdb/mi} Stream Records
23711 @cindex @sc{gdb/mi}, stream records
23712 @cindex stream records in @sc{gdb/mi}
23713 @value{GDBN} internally maintains a number of output streams: the console, the
23714 target, and the log. The output intended for each of these streams is
23715 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23717 Each stream record begins with a unique @dfn{prefix character} which
23718 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23719 Syntax}). In addition to the prefix, each stream record contains a
23720 @code{@var{string-output}}. This is either raw text (with an implicit new
23721 line) or a quoted C string (which does not contain an implicit newline).
23724 @item "~" @var{string-output}
23725 The console output stream contains text that should be displayed in the
23726 CLI console window. It contains the textual responses to CLI commands.
23728 @item "@@" @var{string-output}
23729 The target output stream contains any textual output from the running
23730 target. This is only present when GDB's event loop is truly
23731 asynchronous, which is currently only the case for remote targets.
23733 @item "&" @var{string-output}
23734 The log stream contains debugging messages being produced by @value{GDBN}'s
23738 @node GDB/MI Async Records
23739 @subsection @sc{gdb/mi} Async Records
23741 @cindex async records in @sc{gdb/mi}
23742 @cindex @sc{gdb/mi}, async records
23743 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23744 additional changes that have occurred. Those changes can either be a
23745 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23746 target activity (e.g., target stopped).
23748 The following is the list of possible async records:
23752 @item *running,thread-id="@var{thread}"
23753 The target is now running. The @var{thread} field tells which
23754 specific thread is now running, and can be @samp{all} if all threads
23755 are running. The frontend should assume that no interaction with a
23756 running thread is possible after this notification is produced.
23757 The frontend should not assume that this notification is output
23758 only once for any command. @value{GDBN} may emit this notification
23759 several times, either for different threads, because it cannot resume
23760 all threads together, or even for a single thread, if the thread must
23761 be stepped though some code before letting it run freely.
23763 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23764 The target has stopped. The @var{reason} field can have one of the
23768 @item breakpoint-hit
23769 A breakpoint was reached.
23770 @item watchpoint-trigger
23771 A watchpoint was triggered.
23772 @item read-watchpoint-trigger
23773 A read watchpoint was triggered.
23774 @item access-watchpoint-trigger
23775 An access watchpoint was triggered.
23776 @item function-finished
23777 An -exec-finish or similar CLI command was accomplished.
23778 @item location-reached
23779 An -exec-until or similar CLI command was accomplished.
23780 @item watchpoint-scope
23781 A watchpoint has gone out of scope.
23782 @item end-stepping-range
23783 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23784 similar CLI command was accomplished.
23785 @item exited-signalled
23786 The inferior exited because of a signal.
23788 The inferior exited.
23789 @item exited-normally
23790 The inferior exited normally.
23791 @item signal-received
23792 A signal was received by the inferior.
23795 The @var{id} field identifies the thread that directly caused the stop
23796 -- for example by hitting a breakpoint. Depending on whether all-stop
23797 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23798 stop all threads, or only the thread that directly triggered the stop.
23799 If all threads are stopped, the @var{stopped} field will have the
23800 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23801 field will be a list of thread identifiers. Presently, this list will
23802 always include a single thread, but frontend should be prepared to see
23803 several threads in the list. The @var{core} field reports the
23804 processor core on which the stop event has happened. This field may be absent
23805 if such information is not available.
23807 @item =thread-group-added,id="@var{id}"
23808 @itemx =thread-group-removed,id="@var{id}"
23809 A thread group was either added or removed. The @var{id} field
23810 contains the @value{GDBN} identifier of the thread group. When a thread
23811 group is added, it generally might not be associated with a running
23812 process. When a thread group is removed, its id becomes invalid and
23813 cannot be used in any way.
23815 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23816 A thread group became associated with a running program,
23817 either because the program was just started or the thread group
23818 was attached to a program. The @var{id} field contains the
23819 @value{GDBN} identifier of the thread group. The @var{pid} field
23820 contains process identifier, specific to the operating system.
23822 @itemx =thread-group-exited,id="@var{id}"
23823 A thread group is no longer associated with a running program,
23824 either because the program has exited, or because it was detached
23825 from. The @var{id} field contains the @value{GDBN} identifier of the
23828 @item =thread-created,id="@var{id}",group-id="@var{gid}"
23829 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
23830 A thread either was created, or has exited. The @var{id} field
23831 contains the @value{GDBN} identifier of the thread. The @var{gid}
23832 field identifies the thread group this thread belongs to.
23834 @item =thread-selected,id="@var{id}"
23835 Informs that the selected thread was changed as result of the last
23836 command. This notification is not emitted as result of @code{-thread-select}
23837 command but is emitted whenever an MI command that is not documented
23838 to change the selected thread actually changes it. In particular,
23839 invoking, directly or indirectly (via user-defined command), the CLI
23840 @code{thread} command, will generate this notification.
23842 We suggest that in response to this notification, front ends
23843 highlight the selected thread and cause subsequent commands to apply to
23846 @item =library-loaded,...
23847 Reports that a new library file was loaded by the program. This
23848 notification has 4 fields---@var{id}, @var{target-name},
23849 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23850 opaque identifier of the library. For remote debugging case,
23851 @var{target-name} and @var{host-name} fields give the name of the
23852 library file on the target, and on the host respectively. For native
23853 debugging, both those fields have the same value. The
23854 @var{symbols-loaded} field reports if the debug symbols for this
23855 library are loaded. The @var{thread-group} field, if present,
23856 specifies the id of the thread group in whose context the library was loaded.
23857 If the field is absent, it means the library was loaded in the context
23858 of all present thread groups.
23860 @item =library-unloaded,...
23861 Reports that a library was unloaded by the program. This notification
23862 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23863 the same meaning as for the @code{=library-loaded} notification.
23864 The @var{thread-group} field, if present, specifies the id of the
23865 thread group in whose context the library was unloaded. If the field is
23866 absent, it means the library was unloaded in the context of all present
23871 @node GDB/MI Frame Information
23872 @subsection @sc{gdb/mi} Frame Information
23874 Response from many MI commands includes an information about stack
23875 frame. This information is a tuple that may have the following
23880 The level of the stack frame. The innermost frame has the level of
23881 zero. This field is always present.
23884 The name of the function corresponding to the frame. This field may
23885 be absent if @value{GDBN} is unable to determine the function name.
23888 The code address for the frame. This field is always present.
23891 The name of the source files that correspond to the frame's code
23892 address. This field may be absent.
23895 The source line corresponding to the frames' code address. This field
23899 The name of the binary file (either executable or shared library) the
23900 corresponds to the frame's code address. This field may be absent.
23904 @node GDB/MI Thread Information
23905 @subsection @sc{gdb/mi} Thread Information
23907 Whenever @value{GDBN} has to report an information about a thread, it
23908 uses a tuple with the following fields:
23912 The numeric id assigned to the thread by @value{GDBN}. This field is
23916 Target-specific string identifying the thread. This field is always present.
23919 Additional information about the thread provided by the target.
23920 It is supposed to be human-readable and not interpreted by the
23921 frontend. This field is optional.
23924 Either @samp{stopped} or @samp{running}, depending on whether the
23925 thread is presently running. This field is always present.
23928 The value of this field is an integer number of the processor core the
23929 thread was last seen on. This field is optional.
23933 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23934 @node GDB/MI Simple Examples
23935 @section Simple Examples of @sc{gdb/mi} Interaction
23936 @cindex @sc{gdb/mi}, simple examples
23938 This subsection presents several simple examples of interaction using
23939 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23940 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23941 the output received from @sc{gdb/mi}.
23943 Note the line breaks shown in the examples are here only for
23944 readability, they don't appear in the real output.
23946 @subheading Setting a Breakpoint
23948 Setting a breakpoint generates synchronous output which contains detailed
23949 information of the breakpoint.
23952 -> -break-insert main
23953 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23954 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23955 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23959 @subheading Program Execution
23961 Program execution generates asynchronous records and MI gives the
23962 reason that execution stopped.
23968 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23969 frame=@{addr="0x08048564",func="main",
23970 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23971 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23976 <- *stopped,reason="exited-normally"
23980 @subheading Quitting @value{GDBN}
23982 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23990 Please note that @samp{^exit} is printed immediately, but it might
23991 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23992 performs necessary cleanups, including killing programs being debugged
23993 or disconnecting from debug hardware, so the frontend should wait till
23994 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23995 fails to exit in reasonable time.
23997 @subheading A Bad Command
23999 Here's what happens if you pass a non-existent command:
24003 <- ^error,msg="Undefined MI command: rubbish"
24008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24009 @node GDB/MI Command Description Format
24010 @section @sc{gdb/mi} Command Description Format
24012 The remaining sections describe blocks of commands. Each block of
24013 commands is laid out in a fashion similar to this section.
24015 @subheading Motivation
24017 The motivation for this collection of commands.
24019 @subheading Introduction
24021 A brief introduction to this collection of commands as a whole.
24023 @subheading Commands
24025 For each command in the block, the following is described:
24027 @subsubheading Synopsis
24030 -command @var{args}@dots{}
24033 @subsubheading Result
24035 @subsubheading @value{GDBN} Command
24037 The corresponding @value{GDBN} CLI command(s), if any.
24039 @subsubheading Example
24041 Example(s) formatted for readability. Some of the described commands have
24042 not been implemented yet and these are labeled N.A.@: (not available).
24045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24046 @node GDB/MI Breakpoint Commands
24047 @section @sc{gdb/mi} Breakpoint Commands
24049 @cindex breakpoint commands for @sc{gdb/mi}
24050 @cindex @sc{gdb/mi}, breakpoint commands
24051 This section documents @sc{gdb/mi} commands for manipulating
24054 @subheading The @code{-break-after} Command
24055 @findex -break-after
24057 @subsubheading Synopsis
24060 -break-after @var{number} @var{count}
24063 The breakpoint number @var{number} is not in effect until it has been
24064 hit @var{count} times. To see how this is reflected in the output of
24065 the @samp{-break-list} command, see the description of the
24066 @samp{-break-list} command below.
24068 @subsubheading @value{GDBN} Command
24070 The corresponding @value{GDBN} command is @samp{ignore}.
24072 @subsubheading Example
24077 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24078 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24079 fullname="/home/foo/hello.c",line="5",times="0"@}
24086 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24087 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24088 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24089 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24090 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24091 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24092 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24093 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24094 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24095 line="5",times="0",ignore="3"@}]@}
24100 @subheading The @code{-break-catch} Command
24101 @findex -break-catch
24104 @subheading The @code{-break-commands} Command
24105 @findex -break-commands
24107 @subsubheading Synopsis
24110 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24113 Specifies the CLI commands that should be executed when breakpoint
24114 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24115 are the commands. If no command is specified, any previously-set
24116 commands are cleared. @xref{Break Commands}. Typical use of this
24117 functionality is tracing a program, that is, printing of values of
24118 some variables whenever breakpoint is hit and then continuing.
24120 @subsubheading @value{GDBN} Command
24122 The corresponding @value{GDBN} command is @samp{commands}.
24124 @subsubheading Example
24129 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24130 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24131 fullname="/home/foo/hello.c",line="5",times="0"@}
24133 -break-commands 1 "print v" "continue"
24138 @subheading The @code{-break-condition} Command
24139 @findex -break-condition
24141 @subsubheading Synopsis
24144 -break-condition @var{number} @var{expr}
24147 Breakpoint @var{number} will stop the program only if the condition in
24148 @var{expr} is true. The condition becomes part of the
24149 @samp{-break-list} output (see the description of the @samp{-break-list}
24152 @subsubheading @value{GDBN} Command
24154 The corresponding @value{GDBN} command is @samp{condition}.
24156 @subsubheading Example
24160 -break-condition 1 1
24164 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24165 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24166 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24167 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24168 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24169 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24170 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24171 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24172 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24173 line="5",cond="1",times="0",ignore="3"@}]@}
24177 @subheading The @code{-break-delete} Command
24178 @findex -break-delete
24180 @subsubheading Synopsis
24183 -break-delete ( @var{breakpoint} )+
24186 Delete the breakpoint(s) whose number(s) are specified in the argument
24187 list. This is obviously reflected in the breakpoint list.
24189 @subsubheading @value{GDBN} Command
24191 The corresponding @value{GDBN} command is @samp{delete}.
24193 @subsubheading Example
24201 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24202 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24203 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24204 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24205 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24206 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24207 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24212 @subheading The @code{-break-disable} Command
24213 @findex -break-disable
24215 @subsubheading Synopsis
24218 -break-disable ( @var{breakpoint} )+
24221 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24222 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24224 @subsubheading @value{GDBN} Command
24226 The corresponding @value{GDBN} command is @samp{disable}.
24228 @subsubheading Example
24236 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24237 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24238 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24239 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24240 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24241 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24242 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24243 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24244 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24245 line="5",times="0"@}]@}
24249 @subheading The @code{-break-enable} Command
24250 @findex -break-enable
24252 @subsubheading Synopsis
24255 -break-enable ( @var{breakpoint} )+
24258 Enable (previously disabled) @var{breakpoint}(s).
24260 @subsubheading @value{GDBN} Command
24262 The corresponding @value{GDBN} command is @samp{enable}.
24264 @subsubheading Example
24272 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24273 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24274 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24275 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24276 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24277 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24278 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24279 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24280 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24281 line="5",times="0"@}]@}
24285 @subheading The @code{-break-info} Command
24286 @findex -break-info
24288 @subsubheading Synopsis
24291 -break-info @var{breakpoint}
24295 Get information about a single breakpoint.
24297 @subsubheading @value{GDBN} Command
24299 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24301 @subsubheading Example
24304 @subheading The @code{-break-insert} Command
24305 @findex -break-insert
24307 @subsubheading Synopsis
24310 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24311 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24312 [ -p @var{thread} ] [ @var{location} ]
24316 If specified, @var{location}, can be one of:
24323 @item filename:linenum
24324 @item filename:function
24328 The possible optional parameters of this command are:
24332 Insert a temporary breakpoint.
24334 Insert a hardware breakpoint.
24335 @item -c @var{condition}
24336 Make the breakpoint conditional on @var{condition}.
24337 @item -i @var{ignore-count}
24338 Initialize the @var{ignore-count}.
24340 If @var{location} cannot be parsed (for example if it
24341 refers to unknown files or functions), create a pending
24342 breakpoint. Without this flag, @value{GDBN} will report
24343 an error, and won't create a breakpoint, if @var{location}
24346 Create a disabled breakpoint.
24348 Create a tracepoint. @xref{Tracepoints}. When this parameter
24349 is used together with @samp{-h}, a fast tracepoint is created.
24352 @subsubheading Result
24354 The result is in the form:
24357 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24358 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24359 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24360 times="@var{times}"@}
24364 where @var{number} is the @value{GDBN} number for this breakpoint,
24365 @var{funcname} is the name of the function where the breakpoint was
24366 inserted, @var{filename} is the name of the source file which contains
24367 this function, @var{lineno} is the source line number within that file
24368 and @var{times} the number of times that the breakpoint has been hit
24369 (always 0 for -break-insert but may be greater for -break-info or -break-list
24370 which use the same output).
24372 Note: this format is open to change.
24373 @c An out-of-band breakpoint instead of part of the result?
24375 @subsubheading @value{GDBN} Command
24377 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24378 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24380 @subsubheading Example
24385 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24386 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24388 -break-insert -t foo
24389 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24390 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24393 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24394 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24395 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24396 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24397 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24398 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24399 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24400 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24401 addr="0x0001072c", func="main",file="recursive2.c",
24402 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24403 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24404 addr="0x00010774",func="foo",file="recursive2.c",
24405 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24407 -break-insert -r foo.*
24408 ~int foo(int, int);
24409 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24410 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24414 @subheading The @code{-break-list} Command
24415 @findex -break-list
24417 @subsubheading Synopsis
24423 Displays the list of inserted breakpoints, showing the following fields:
24427 number of the breakpoint
24429 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24431 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24434 is the breakpoint enabled or no: @samp{y} or @samp{n}
24436 memory location at which the breakpoint is set
24438 logical location of the breakpoint, expressed by function name, file
24441 number of times the breakpoint has been hit
24444 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24445 @code{body} field is an empty list.
24447 @subsubheading @value{GDBN} Command
24449 The corresponding @value{GDBN} command is @samp{info break}.
24451 @subsubheading Example
24456 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24457 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24458 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24459 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24460 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24461 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24462 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24463 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24464 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24465 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24466 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24467 line="13",times="0"@}]@}
24471 Here's an example of the result when there are no breakpoints:
24476 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24477 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24478 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24479 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24480 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24481 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24482 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24487 @subheading The @code{-break-passcount} Command
24488 @findex -break-passcount
24490 @subsubheading Synopsis
24493 -break-passcount @var{tracepoint-number} @var{passcount}
24496 Set the passcount for tracepoint @var{tracepoint-number} to
24497 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24498 is not a tracepoint, error is emitted. This corresponds to CLI
24499 command @samp{passcount}.
24501 @subheading The @code{-break-watch} Command
24502 @findex -break-watch
24504 @subsubheading Synopsis
24507 -break-watch [ -a | -r ]
24510 Create a watchpoint. With the @samp{-a} option it will create an
24511 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24512 read from or on a write to the memory location. With the @samp{-r}
24513 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24514 trigger only when the memory location is accessed for reading. Without
24515 either of the options, the watchpoint created is a regular watchpoint,
24516 i.e., it will trigger when the memory location is accessed for writing.
24517 @xref{Set Watchpoints, , Setting Watchpoints}.
24519 Note that @samp{-break-list} will report a single list of watchpoints and
24520 breakpoints inserted.
24522 @subsubheading @value{GDBN} Command
24524 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24527 @subsubheading Example
24529 Setting a watchpoint on a variable in the @code{main} function:
24534 ^done,wpt=@{number="2",exp="x"@}
24539 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24540 value=@{old="-268439212",new="55"@},
24541 frame=@{func="main",args=[],file="recursive2.c",
24542 fullname="/home/foo/bar/recursive2.c",line="5"@}
24546 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24547 the program execution twice: first for the variable changing value, then
24548 for the watchpoint going out of scope.
24553 ^done,wpt=@{number="5",exp="C"@}
24558 *stopped,reason="watchpoint-trigger",
24559 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24560 frame=@{func="callee4",args=[],
24561 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24562 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24567 *stopped,reason="watchpoint-scope",wpnum="5",
24568 frame=@{func="callee3",args=[@{name="strarg",
24569 value="0x11940 \"A string argument.\""@}],
24570 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24571 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24575 Listing breakpoints and watchpoints, at different points in the program
24576 execution. Note that once the watchpoint goes out of scope, it is
24582 ^done,wpt=@{number="2",exp="C"@}
24585 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24586 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24587 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24588 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24589 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24590 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24591 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24592 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24593 addr="0x00010734",func="callee4",
24594 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24595 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24596 bkpt=@{number="2",type="watchpoint",disp="keep",
24597 enabled="y",addr="",what="C",times="0"@}]@}
24602 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24603 value=@{old="-276895068",new="3"@},
24604 frame=@{func="callee4",args=[],
24605 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24606 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24609 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24610 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24611 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24612 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24613 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24614 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24615 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24616 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24617 addr="0x00010734",func="callee4",
24618 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24619 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24620 bkpt=@{number="2",type="watchpoint",disp="keep",
24621 enabled="y",addr="",what="C",times="-5"@}]@}
24625 ^done,reason="watchpoint-scope",wpnum="2",
24626 frame=@{func="callee3",args=[@{name="strarg",
24627 value="0x11940 \"A string argument.\""@}],
24628 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24629 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24632 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24633 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24634 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24635 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24636 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24637 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24638 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24639 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24640 addr="0x00010734",func="callee4",
24641 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24642 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24647 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24648 @node GDB/MI Program Context
24649 @section @sc{gdb/mi} Program Context
24651 @subheading The @code{-exec-arguments} Command
24652 @findex -exec-arguments
24655 @subsubheading Synopsis
24658 -exec-arguments @var{args}
24661 Set the inferior program arguments, to be used in the next
24664 @subsubheading @value{GDBN} Command
24666 The corresponding @value{GDBN} command is @samp{set args}.
24668 @subsubheading Example
24672 -exec-arguments -v word
24679 @subheading The @code{-exec-show-arguments} Command
24680 @findex -exec-show-arguments
24682 @subsubheading Synopsis
24685 -exec-show-arguments
24688 Print the arguments of the program.
24690 @subsubheading @value{GDBN} Command
24692 The corresponding @value{GDBN} command is @samp{show args}.
24694 @subsubheading Example
24699 @subheading The @code{-environment-cd} Command
24700 @findex -environment-cd
24702 @subsubheading Synopsis
24705 -environment-cd @var{pathdir}
24708 Set @value{GDBN}'s working directory.
24710 @subsubheading @value{GDBN} Command
24712 The corresponding @value{GDBN} command is @samp{cd}.
24714 @subsubheading Example
24718 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24724 @subheading The @code{-environment-directory} Command
24725 @findex -environment-directory
24727 @subsubheading Synopsis
24730 -environment-directory [ -r ] [ @var{pathdir} ]+
24733 Add directories @var{pathdir} to beginning of search path for source files.
24734 If the @samp{-r} option is used, the search path is reset to the default
24735 search path. If directories @var{pathdir} are supplied in addition to the
24736 @samp{-r} option, the search path is first reset and then addition
24738 Multiple directories may be specified, separated by blanks. Specifying
24739 multiple directories in a single command
24740 results in the directories added to the beginning of the
24741 search path in the same order they were presented in the command.
24742 If blanks are needed as
24743 part of a directory name, double-quotes should be used around
24744 the name. In the command output, the path will show up separated
24745 by the system directory-separator character. The directory-separator
24746 character must not be used
24747 in any directory name.
24748 If no directories are specified, the current search path is displayed.
24750 @subsubheading @value{GDBN} Command
24752 The corresponding @value{GDBN} command is @samp{dir}.
24754 @subsubheading Example
24758 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24759 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24761 -environment-directory ""
24762 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24764 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24765 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24767 -environment-directory -r
24768 ^done,source-path="$cdir:$cwd"
24773 @subheading The @code{-environment-path} Command
24774 @findex -environment-path
24776 @subsubheading Synopsis
24779 -environment-path [ -r ] [ @var{pathdir} ]+
24782 Add directories @var{pathdir} to beginning of search path for object files.
24783 If the @samp{-r} option is used, the search path is reset to the original
24784 search path that existed at gdb start-up. If directories @var{pathdir} are
24785 supplied in addition to the
24786 @samp{-r} option, the search path is first reset and then addition
24788 Multiple directories may be specified, separated by blanks. Specifying
24789 multiple directories in a single command
24790 results in the directories added to the beginning of the
24791 search path in the same order they were presented in the command.
24792 If blanks are needed as
24793 part of a directory name, double-quotes should be used around
24794 the name. In the command output, the path will show up separated
24795 by the system directory-separator character. The directory-separator
24796 character must not be used
24797 in any directory name.
24798 If no directories are specified, the current path is displayed.
24801 @subsubheading @value{GDBN} Command
24803 The corresponding @value{GDBN} command is @samp{path}.
24805 @subsubheading Example
24810 ^done,path="/usr/bin"
24812 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24813 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24815 -environment-path -r /usr/local/bin
24816 ^done,path="/usr/local/bin:/usr/bin"
24821 @subheading The @code{-environment-pwd} Command
24822 @findex -environment-pwd
24824 @subsubheading Synopsis
24830 Show the current working directory.
24832 @subsubheading @value{GDBN} Command
24834 The corresponding @value{GDBN} command is @samp{pwd}.
24836 @subsubheading Example
24841 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24846 @node GDB/MI Thread Commands
24847 @section @sc{gdb/mi} Thread Commands
24850 @subheading The @code{-thread-info} Command
24851 @findex -thread-info
24853 @subsubheading Synopsis
24856 -thread-info [ @var{thread-id} ]
24859 Reports information about either a specific thread, if
24860 the @var{thread-id} parameter is present, or about all
24861 threads. When printing information about all threads,
24862 also reports the current thread.
24864 @subsubheading @value{GDBN} Command
24866 The @samp{info thread} command prints the same information
24869 @subsubheading Example
24874 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24875 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24876 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24877 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24878 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24879 current-thread-id="1"
24883 The @samp{state} field may have the following values:
24887 The thread is stopped. Frame information is available for stopped
24891 The thread is running. There's no frame information for running
24896 @subheading The @code{-thread-list-ids} Command
24897 @findex -thread-list-ids
24899 @subsubheading Synopsis
24905 Produces a list of the currently known @value{GDBN} thread ids. At the
24906 end of the list it also prints the total number of such threads.
24908 This command is retained for historical reasons, the
24909 @code{-thread-info} command should be used instead.
24911 @subsubheading @value{GDBN} Command
24913 Part of @samp{info threads} supplies the same information.
24915 @subsubheading Example
24920 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24921 current-thread-id="1",number-of-threads="3"
24926 @subheading The @code{-thread-select} Command
24927 @findex -thread-select
24929 @subsubheading Synopsis
24932 -thread-select @var{threadnum}
24935 Make @var{threadnum} the current thread. It prints the number of the new
24936 current thread, and the topmost frame for that thread.
24938 This command is deprecated in favor of explicitly using the
24939 @samp{--thread} option to each command.
24941 @subsubheading @value{GDBN} Command
24943 The corresponding @value{GDBN} command is @samp{thread}.
24945 @subsubheading Example
24952 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24953 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24957 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24958 number-of-threads="3"
24961 ^done,new-thread-id="3",
24962 frame=@{level="0",func="vprintf",
24963 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24964 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24969 @node GDB/MI Program Execution
24970 @section @sc{gdb/mi} Program Execution
24972 These are the asynchronous commands which generate the out-of-band
24973 record @samp{*stopped}. Currently @value{GDBN} only really executes
24974 asynchronously with remote targets and this interaction is mimicked in
24977 @subheading The @code{-exec-continue} Command
24978 @findex -exec-continue
24980 @subsubheading Synopsis
24983 -exec-continue [--reverse] [--all|--thread-group N]
24986 Resumes the execution of the inferior program, which will continue
24987 to execute until it reaches a debugger stop event. If the
24988 @samp{--reverse} option is specified, execution resumes in reverse until
24989 it reaches a stop event. Stop events may include
24992 breakpoints or watchpoints
24994 signals or exceptions
24996 the end of the process (or its beginning under @samp{--reverse})
24998 the end or beginning of a replay log if one is being used.
25000 In all-stop mode (@pxref{All-Stop
25001 Mode}), may resume only one thread, or all threads, depending on the
25002 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25003 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25004 ignored in all-stop mode. If the @samp{--thread-group} options is
25005 specified, then all threads in that thread group are resumed.
25007 @subsubheading @value{GDBN} Command
25009 The corresponding @value{GDBN} corresponding is @samp{continue}.
25011 @subsubheading Example
25018 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25019 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25025 @subheading The @code{-exec-finish} Command
25026 @findex -exec-finish
25028 @subsubheading Synopsis
25031 -exec-finish [--reverse]
25034 Resumes the execution of the inferior program until the current
25035 function is exited. Displays the results returned by the function.
25036 If the @samp{--reverse} option is specified, resumes the reverse
25037 execution of the inferior program until the point where current
25038 function was called.
25040 @subsubheading @value{GDBN} Command
25042 The corresponding @value{GDBN} command is @samp{finish}.
25044 @subsubheading Example
25046 Function returning @code{void}.
25053 *stopped,reason="function-finished",frame=@{func="main",args=[],
25054 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25058 Function returning other than @code{void}. The name of the internal
25059 @value{GDBN} variable storing the result is printed, together with the
25066 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25067 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25069 gdb-result-var="$1",return-value="0"
25074 @subheading The @code{-exec-interrupt} Command
25075 @findex -exec-interrupt
25077 @subsubheading Synopsis
25080 -exec-interrupt [--all|--thread-group N]
25083 Interrupts the background execution of the target. Note how the token
25084 associated with the stop message is the one for the execution command
25085 that has been interrupted. The token for the interrupt itself only
25086 appears in the @samp{^done} output. If the user is trying to
25087 interrupt a non-running program, an error message will be printed.
25089 Note that when asynchronous execution is enabled, this command is
25090 asynchronous just like other execution commands. That is, first the
25091 @samp{^done} response will be printed, and the target stop will be
25092 reported after that using the @samp{*stopped} notification.
25094 In non-stop mode, only the context thread is interrupted by default.
25095 All threads (in all inferiors) will be interrupted if the
25096 @samp{--all} option is specified. If the @samp{--thread-group}
25097 option is specified, all threads in that group will be interrupted.
25099 @subsubheading @value{GDBN} Command
25101 The corresponding @value{GDBN} command is @samp{interrupt}.
25103 @subsubheading Example
25114 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25115 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25116 fullname="/home/foo/bar/try.c",line="13"@}
25121 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25125 @subheading The @code{-exec-jump} Command
25128 @subsubheading Synopsis
25131 -exec-jump @var{location}
25134 Resumes execution of the inferior program at the location specified by
25135 parameter. @xref{Specify Location}, for a description of the
25136 different forms of @var{location}.
25138 @subsubheading @value{GDBN} Command
25140 The corresponding @value{GDBN} command is @samp{jump}.
25142 @subsubheading Example
25145 -exec-jump foo.c:10
25146 *running,thread-id="all"
25151 @subheading The @code{-exec-next} Command
25154 @subsubheading Synopsis
25157 -exec-next [--reverse]
25160 Resumes execution of the inferior program, stopping when the beginning
25161 of the next source line is reached.
25163 If the @samp{--reverse} option is specified, resumes reverse execution
25164 of the inferior program, stopping at the beginning of the previous
25165 source line. If you issue this command on the first line of a
25166 function, it will take you back to the caller of that function, to the
25167 source line where the function was called.
25170 @subsubheading @value{GDBN} Command
25172 The corresponding @value{GDBN} command is @samp{next}.
25174 @subsubheading Example
25180 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25185 @subheading The @code{-exec-next-instruction} Command
25186 @findex -exec-next-instruction
25188 @subsubheading Synopsis
25191 -exec-next-instruction [--reverse]
25194 Executes one machine instruction. If the instruction is a function
25195 call, continues until the function returns. If the program stops at an
25196 instruction in the middle of a source line, the address will be
25199 If the @samp{--reverse} option is specified, resumes reverse execution
25200 of the inferior program, stopping at the previous instruction. If the
25201 previously executed instruction was a return from another function,
25202 it will continue to execute in reverse until the call to that function
25203 (from the current stack frame) is reached.
25205 @subsubheading @value{GDBN} Command
25207 The corresponding @value{GDBN} command is @samp{nexti}.
25209 @subsubheading Example
25213 -exec-next-instruction
25217 *stopped,reason="end-stepping-range",
25218 addr="0x000100d4",line="5",file="hello.c"
25223 @subheading The @code{-exec-return} Command
25224 @findex -exec-return
25226 @subsubheading Synopsis
25232 Makes current function return immediately. Doesn't execute the inferior.
25233 Displays the new current frame.
25235 @subsubheading @value{GDBN} Command
25237 The corresponding @value{GDBN} command is @samp{return}.
25239 @subsubheading Example
25243 200-break-insert callee4
25244 200^done,bkpt=@{number="1",addr="0x00010734",
25245 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25250 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25251 frame=@{func="callee4",args=[],
25252 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25253 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25259 111^done,frame=@{level="0",func="callee3",
25260 args=[@{name="strarg",
25261 value="0x11940 \"A string argument.\""@}],
25262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25263 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25268 @subheading The @code{-exec-run} Command
25271 @subsubheading Synopsis
25274 -exec-run [--all | --thread-group N]
25277 Starts execution of the inferior from the beginning. The inferior
25278 executes until either a breakpoint is encountered or the program
25279 exits. In the latter case the output will include an exit code, if
25280 the program has exited exceptionally.
25282 When no option is specified, the current inferior is started. If the
25283 @samp{--thread-group} option is specified, it should refer to a thread
25284 group of type @samp{process}, and that thread group will be started.
25285 If the @samp{--all} option is specified, then all inferiors will be started.
25287 @subsubheading @value{GDBN} Command
25289 The corresponding @value{GDBN} command is @samp{run}.
25291 @subsubheading Examples
25296 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25301 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25302 frame=@{func="main",args=[],file="recursive2.c",
25303 fullname="/home/foo/bar/recursive2.c",line="4"@}
25308 Program exited normally:
25316 *stopped,reason="exited-normally"
25321 Program exited exceptionally:
25329 *stopped,reason="exited",exit-code="01"
25333 Another way the program can terminate is if it receives a signal such as
25334 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25338 *stopped,reason="exited-signalled",signal-name="SIGINT",
25339 signal-meaning="Interrupt"
25343 @c @subheading -exec-signal
25346 @subheading The @code{-exec-step} Command
25349 @subsubheading Synopsis
25352 -exec-step [--reverse]
25355 Resumes execution of the inferior program, stopping when the beginning
25356 of the next source line is reached, if the next source line is not a
25357 function call. If it is, stop at the first instruction of the called
25358 function. If the @samp{--reverse} option is specified, resumes reverse
25359 execution of the inferior program, stopping at the beginning of the
25360 previously executed source line.
25362 @subsubheading @value{GDBN} Command
25364 The corresponding @value{GDBN} command is @samp{step}.
25366 @subsubheading Example
25368 Stepping into a function:
25374 *stopped,reason="end-stepping-range",
25375 frame=@{func="foo",args=[@{name="a",value="10"@},
25376 @{name="b",value="0"@}],file="recursive2.c",
25377 fullname="/home/foo/bar/recursive2.c",line="11"@}
25387 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25392 @subheading The @code{-exec-step-instruction} Command
25393 @findex -exec-step-instruction
25395 @subsubheading Synopsis
25398 -exec-step-instruction [--reverse]
25401 Resumes the inferior which executes one machine instruction. If the
25402 @samp{--reverse} option is specified, resumes reverse execution of the
25403 inferior program, stopping at the previously executed instruction.
25404 The output, once @value{GDBN} has stopped, will vary depending on
25405 whether we have stopped in the middle of a source line or not. In the
25406 former case, the address at which the program stopped will be printed
25409 @subsubheading @value{GDBN} Command
25411 The corresponding @value{GDBN} command is @samp{stepi}.
25413 @subsubheading Example
25417 -exec-step-instruction
25421 *stopped,reason="end-stepping-range",
25422 frame=@{func="foo",args=[],file="try.c",
25423 fullname="/home/foo/bar/try.c",line="10"@}
25425 -exec-step-instruction
25429 *stopped,reason="end-stepping-range",
25430 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25431 fullname="/home/foo/bar/try.c",line="10"@}
25436 @subheading The @code{-exec-until} Command
25437 @findex -exec-until
25439 @subsubheading Synopsis
25442 -exec-until [ @var{location} ]
25445 Executes the inferior until the @var{location} specified in the
25446 argument is reached. If there is no argument, the inferior executes
25447 until a source line greater than the current one is reached. The
25448 reason for stopping in this case will be @samp{location-reached}.
25450 @subsubheading @value{GDBN} Command
25452 The corresponding @value{GDBN} command is @samp{until}.
25454 @subsubheading Example
25458 -exec-until recursive2.c:6
25462 *stopped,reason="location-reached",frame=@{func="main",args=[],
25463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25468 @subheading -file-clear
25469 Is this going away????
25472 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25473 @node GDB/MI Stack Manipulation
25474 @section @sc{gdb/mi} Stack Manipulation Commands
25477 @subheading The @code{-stack-info-frame} Command
25478 @findex -stack-info-frame
25480 @subsubheading Synopsis
25486 Get info on the selected frame.
25488 @subsubheading @value{GDBN} Command
25490 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25491 (without arguments).
25493 @subsubheading Example
25498 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25499 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25500 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25504 @subheading The @code{-stack-info-depth} Command
25505 @findex -stack-info-depth
25507 @subsubheading Synopsis
25510 -stack-info-depth [ @var{max-depth} ]
25513 Return the depth of the stack. If the integer argument @var{max-depth}
25514 is specified, do not count beyond @var{max-depth} frames.
25516 @subsubheading @value{GDBN} Command
25518 There's no equivalent @value{GDBN} command.
25520 @subsubheading Example
25522 For a stack with frame levels 0 through 11:
25529 -stack-info-depth 4
25532 -stack-info-depth 12
25535 -stack-info-depth 11
25538 -stack-info-depth 13
25543 @subheading The @code{-stack-list-arguments} Command
25544 @findex -stack-list-arguments
25546 @subsubheading Synopsis
25549 -stack-list-arguments @var{print-values}
25550 [ @var{low-frame} @var{high-frame} ]
25553 Display a list of the arguments for the frames between @var{low-frame}
25554 and @var{high-frame} (inclusive). If @var{low-frame} and
25555 @var{high-frame} are not provided, list the arguments for the whole
25556 call stack. If the two arguments are equal, show the single frame
25557 at the corresponding level. It is an error if @var{low-frame} is
25558 larger than the actual number of frames. On the other hand,
25559 @var{high-frame} may be larger than the actual number of frames, in
25560 which case only existing frames will be returned.
25562 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25563 the variables; if it is 1 or @code{--all-values}, print also their
25564 values; and if it is 2 or @code{--simple-values}, print the name,
25565 type and value for simple data types, and the name and type for arrays,
25566 structures and unions.
25568 Use of this command to obtain arguments in a single frame is
25569 deprecated in favor of the @samp{-stack-list-variables} command.
25571 @subsubheading @value{GDBN} Command
25573 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25574 @samp{gdb_get_args} command which partially overlaps with the
25575 functionality of @samp{-stack-list-arguments}.
25577 @subsubheading Example
25584 frame=@{level="0",addr="0x00010734",func="callee4",
25585 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25586 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25587 frame=@{level="1",addr="0x0001076c",func="callee3",
25588 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25589 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25590 frame=@{level="2",addr="0x0001078c",func="callee2",
25591 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25592 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25593 frame=@{level="3",addr="0x000107b4",func="callee1",
25594 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25595 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25596 frame=@{level="4",addr="0x000107e0",func="main",
25597 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25598 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25600 -stack-list-arguments 0
25603 frame=@{level="0",args=[]@},
25604 frame=@{level="1",args=[name="strarg"]@},
25605 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25606 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25607 frame=@{level="4",args=[]@}]
25609 -stack-list-arguments 1
25612 frame=@{level="0",args=[]@},
25614 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25615 frame=@{level="2",args=[
25616 @{name="intarg",value="2"@},
25617 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25618 @{frame=@{level="3",args=[
25619 @{name="intarg",value="2"@},
25620 @{name="strarg",value="0x11940 \"A string argument.\""@},
25621 @{name="fltarg",value="3.5"@}]@},
25622 frame=@{level="4",args=[]@}]
25624 -stack-list-arguments 0 2 2
25625 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25627 -stack-list-arguments 1 2 2
25628 ^done,stack-args=[frame=@{level="2",
25629 args=[@{name="intarg",value="2"@},
25630 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25634 @c @subheading -stack-list-exception-handlers
25637 @subheading The @code{-stack-list-frames} Command
25638 @findex -stack-list-frames
25640 @subsubheading Synopsis
25643 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25646 List the frames currently on the stack. For each frame it displays the
25651 The frame number, 0 being the topmost frame, i.e., the innermost function.
25653 The @code{$pc} value for that frame.
25657 File name of the source file where the function lives.
25659 Line number corresponding to the @code{$pc}.
25662 If invoked without arguments, this command prints a backtrace for the
25663 whole stack. If given two integer arguments, it shows the frames whose
25664 levels are between the two arguments (inclusive). If the two arguments
25665 are equal, it shows the single frame at the corresponding level. It is
25666 an error if @var{low-frame} is larger than the actual number of
25667 frames. On the other hand, @var{high-frame} may be larger than the
25668 actual number of frames, in which case only existing frames will be returned.
25670 @subsubheading @value{GDBN} Command
25672 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25674 @subsubheading Example
25676 Full stack backtrace:
25682 [frame=@{level="0",addr="0x0001076c",func="foo",
25683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25684 frame=@{level="1",addr="0x000107a4",func="foo",
25685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25686 frame=@{level="2",addr="0x000107a4",func="foo",
25687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25688 frame=@{level="3",addr="0x000107a4",func="foo",
25689 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25690 frame=@{level="4",addr="0x000107a4",func="foo",
25691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25692 frame=@{level="5",addr="0x000107a4",func="foo",
25693 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25694 frame=@{level="6",addr="0x000107a4",func="foo",
25695 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25696 frame=@{level="7",addr="0x000107a4",func="foo",
25697 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25698 frame=@{level="8",addr="0x000107a4",func="foo",
25699 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25700 frame=@{level="9",addr="0x000107a4",func="foo",
25701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25702 frame=@{level="10",addr="0x000107a4",func="foo",
25703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25704 frame=@{level="11",addr="0x00010738",func="main",
25705 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25709 Show frames between @var{low_frame} and @var{high_frame}:
25713 -stack-list-frames 3 5
25715 [frame=@{level="3",addr="0x000107a4",func="foo",
25716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25717 frame=@{level="4",addr="0x000107a4",func="foo",
25718 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25719 frame=@{level="5",addr="0x000107a4",func="foo",
25720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25724 Show a single frame:
25728 -stack-list-frames 3 3
25730 [frame=@{level="3",addr="0x000107a4",func="foo",
25731 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25736 @subheading The @code{-stack-list-locals} Command
25737 @findex -stack-list-locals
25739 @subsubheading Synopsis
25742 -stack-list-locals @var{print-values}
25745 Display the local variable names for the selected frame. If
25746 @var{print-values} is 0 or @code{--no-values}, print only the names of
25747 the variables; if it is 1 or @code{--all-values}, print also their
25748 values; and if it is 2 or @code{--simple-values}, print the name,
25749 type and value for simple data types, and the name and type for arrays,
25750 structures and unions. In this last case, a frontend can immediately
25751 display the value of simple data types and create variable objects for
25752 other data types when the user wishes to explore their values in
25755 This command is deprecated in favor of the
25756 @samp{-stack-list-variables} command.
25758 @subsubheading @value{GDBN} Command
25760 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25762 @subsubheading Example
25766 -stack-list-locals 0
25767 ^done,locals=[name="A",name="B",name="C"]
25769 -stack-list-locals --all-values
25770 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25771 @{name="C",value="@{1, 2, 3@}"@}]
25772 -stack-list-locals --simple-values
25773 ^done,locals=[@{name="A",type="int",value="1"@},
25774 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25778 @subheading The @code{-stack-list-variables} Command
25779 @findex -stack-list-variables
25781 @subsubheading Synopsis
25784 -stack-list-variables @var{print-values}
25787 Display the names of local variables and function arguments for the selected frame. If
25788 @var{print-values} is 0 or @code{--no-values}, print only the names of
25789 the variables; if it is 1 or @code{--all-values}, print also their
25790 values; and if it is 2 or @code{--simple-values}, print the name,
25791 type and value for simple data types, and the name and type for arrays,
25792 structures and unions.
25794 @subsubheading Example
25798 -stack-list-variables --thread 1 --frame 0 --all-values
25799 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25804 @subheading The @code{-stack-select-frame} Command
25805 @findex -stack-select-frame
25807 @subsubheading Synopsis
25810 -stack-select-frame @var{framenum}
25813 Change the selected frame. Select a different frame @var{framenum} on
25816 This command in deprecated in favor of passing the @samp{--frame}
25817 option to every command.
25819 @subsubheading @value{GDBN} Command
25821 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25822 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
25824 @subsubheading Example
25828 -stack-select-frame 2
25833 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25834 @node GDB/MI Variable Objects
25835 @section @sc{gdb/mi} Variable Objects
25839 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25841 For the implementation of a variable debugger window (locals, watched
25842 expressions, etc.), we are proposing the adaptation of the existing code
25843 used by @code{Insight}.
25845 The two main reasons for that are:
25849 It has been proven in practice (it is already on its second generation).
25852 It will shorten development time (needless to say how important it is
25856 The original interface was designed to be used by Tcl code, so it was
25857 slightly changed so it could be used through @sc{gdb/mi}. This section
25858 describes the @sc{gdb/mi} operations that will be available and gives some
25859 hints about their use.
25861 @emph{Note}: In addition to the set of operations described here, we
25862 expect the @sc{gui} implementation of a variable window to require, at
25863 least, the following operations:
25866 @item @code{-gdb-show} @code{output-radix}
25867 @item @code{-stack-list-arguments}
25868 @item @code{-stack-list-locals}
25869 @item @code{-stack-select-frame}
25874 @subheading Introduction to Variable Objects
25876 @cindex variable objects in @sc{gdb/mi}
25878 Variable objects are "object-oriented" MI interface for examining and
25879 changing values of expressions. Unlike some other MI interfaces that
25880 work with expressions, variable objects are specifically designed for
25881 simple and efficient presentation in the frontend. A variable object
25882 is identified by string name. When a variable object is created, the
25883 frontend specifies the expression for that variable object. The
25884 expression can be a simple variable, or it can be an arbitrary complex
25885 expression, and can even involve CPU registers. After creating a
25886 variable object, the frontend can invoke other variable object
25887 operations---for example to obtain or change the value of a variable
25888 object, or to change display format.
25890 Variable objects have hierarchical tree structure. Any variable object
25891 that corresponds to a composite type, such as structure in C, has
25892 a number of child variable objects, for example corresponding to each
25893 element of a structure. A child variable object can itself have
25894 children, recursively. Recursion ends when we reach
25895 leaf variable objects, which always have built-in types. Child variable
25896 objects are created only by explicit request, so if a frontend
25897 is not interested in the children of a particular variable object, no
25898 child will be created.
25900 For a leaf variable object it is possible to obtain its value as a
25901 string, or set the value from a string. String value can be also
25902 obtained for a non-leaf variable object, but it's generally a string
25903 that only indicates the type of the object, and does not list its
25904 contents. Assignment to a non-leaf variable object is not allowed.
25906 A frontend does not need to read the values of all variable objects each time
25907 the program stops. Instead, MI provides an update command that lists all
25908 variable objects whose values has changed since the last update
25909 operation. This considerably reduces the amount of data that must
25910 be transferred to the frontend. As noted above, children variable
25911 objects are created on demand, and only leaf variable objects have a
25912 real value. As result, gdb will read target memory only for leaf
25913 variables that frontend has created.
25915 The automatic update is not always desirable. For example, a frontend
25916 might want to keep a value of some expression for future reference,
25917 and never update it. For another example, fetching memory is
25918 relatively slow for embedded targets, so a frontend might want
25919 to disable automatic update for the variables that are either not
25920 visible on the screen, or ``closed''. This is possible using so
25921 called ``frozen variable objects''. Such variable objects are never
25922 implicitly updated.
25924 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25925 fixed variable object, the expression is parsed when the variable
25926 object is created, including associating identifiers to specific
25927 variables. The meaning of expression never changes. For a floating
25928 variable object the values of variables whose names appear in the
25929 expressions are re-evaluated every time in the context of the current
25930 frame. Consider this example:
25935 struct work_state state;
25942 If a fixed variable object for the @code{state} variable is created in
25943 this function, and we enter the recursive call, the the variable
25944 object will report the value of @code{state} in the top-level
25945 @code{do_work} invocation. On the other hand, a floating variable
25946 object will report the value of @code{state} in the current frame.
25948 If an expression specified when creating a fixed variable object
25949 refers to a local variable, the variable object becomes bound to the
25950 thread and frame in which the variable object is created. When such
25951 variable object is updated, @value{GDBN} makes sure that the
25952 thread/frame combination the variable object is bound to still exists,
25953 and re-evaluates the variable object in context of that thread/frame.
25955 The following is the complete set of @sc{gdb/mi} operations defined to
25956 access this functionality:
25958 @multitable @columnfractions .4 .6
25959 @item @strong{Operation}
25960 @tab @strong{Description}
25962 @item @code{-enable-pretty-printing}
25963 @tab enable Python-based pretty-printing
25964 @item @code{-var-create}
25965 @tab create a variable object
25966 @item @code{-var-delete}
25967 @tab delete the variable object and/or its children
25968 @item @code{-var-set-format}
25969 @tab set the display format of this variable
25970 @item @code{-var-show-format}
25971 @tab show the display format of this variable
25972 @item @code{-var-info-num-children}
25973 @tab tells how many children this object has
25974 @item @code{-var-list-children}
25975 @tab return a list of the object's children
25976 @item @code{-var-info-type}
25977 @tab show the type of this variable object
25978 @item @code{-var-info-expression}
25979 @tab print parent-relative expression that this variable object represents
25980 @item @code{-var-info-path-expression}
25981 @tab print full expression that this variable object represents
25982 @item @code{-var-show-attributes}
25983 @tab is this variable editable? does it exist here?
25984 @item @code{-var-evaluate-expression}
25985 @tab get the value of this variable
25986 @item @code{-var-assign}
25987 @tab set the value of this variable
25988 @item @code{-var-update}
25989 @tab update the variable and its children
25990 @item @code{-var-set-frozen}
25991 @tab set frozeness attribute
25992 @item @code{-var-set-update-range}
25993 @tab set range of children to display on update
25996 In the next subsection we describe each operation in detail and suggest
25997 how it can be used.
25999 @subheading Description And Use of Operations on Variable Objects
26001 @subheading The @code{-enable-pretty-printing} Command
26002 @findex -enable-pretty-printing
26005 -enable-pretty-printing
26008 @value{GDBN} allows Python-based visualizers to affect the output of the
26009 MI variable object commands. However, because there was no way to
26010 implement this in a fully backward-compatible way, a front end must
26011 request that this functionality be enabled.
26013 Once enabled, this feature cannot be disabled.
26015 Note that if Python support has not been compiled into @value{GDBN},
26016 this command will still succeed (and do nothing).
26018 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26019 may work differently in future versions of @value{GDBN}.
26021 @subheading The @code{-var-create} Command
26022 @findex -var-create
26024 @subsubheading Synopsis
26027 -var-create @{@var{name} | "-"@}
26028 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26031 This operation creates a variable object, which allows the monitoring of
26032 a variable, the result of an expression, a memory cell or a CPU
26035 The @var{name} parameter is the string by which the object can be
26036 referenced. It must be unique. If @samp{-} is specified, the varobj
26037 system will generate a string ``varNNNNNN'' automatically. It will be
26038 unique provided that one does not specify @var{name} of that format.
26039 The command fails if a duplicate name is found.
26041 The frame under which the expression should be evaluated can be
26042 specified by @var{frame-addr}. A @samp{*} indicates that the current
26043 frame should be used. A @samp{@@} indicates that a floating variable
26044 object must be created.
26046 @var{expression} is any expression valid on the current language set (must not
26047 begin with a @samp{*}), or one of the following:
26051 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26054 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26057 @samp{$@var{regname}} --- a CPU register name
26060 @cindex dynamic varobj
26061 A varobj's contents may be provided by a Python-based pretty-printer. In this
26062 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26063 have slightly different semantics in some cases. If the
26064 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26065 will never create a dynamic varobj. This ensures backward
26066 compatibility for existing clients.
26068 @subsubheading Result
26070 This operation returns attributes of the newly-created varobj. These
26075 The name of the varobj.
26078 The number of children of the varobj. This number is not necessarily
26079 reliable for a dynamic varobj. Instead, you must examine the
26080 @samp{has_more} attribute.
26083 The varobj's scalar value. For a varobj whose type is some sort of
26084 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26085 will not be interesting.
26088 The varobj's type. This is a string representation of the type, as
26089 would be printed by the @value{GDBN} CLI.
26092 If a variable object is bound to a specific thread, then this is the
26093 thread's identifier.
26096 For a dynamic varobj, this indicates whether there appear to be any
26097 children available. For a non-dynamic varobj, this will be 0.
26100 This attribute will be present and have the value @samp{1} if the
26101 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26102 then this attribute will not be present.
26105 A dynamic varobj can supply a display hint to the front end. The
26106 value comes directly from the Python pretty-printer object's
26107 @code{display_hint} method. @xref{Pretty Printing API}.
26110 Typical output will look like this:
26113 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26114 has_more="@var{has_more}"
26118 @subheading The @code{-var-delete} Command
26119 @findex -var-delete
26121 @subsubheading Synopsis
26124 -var-delete [ -c ] @var{name}
26127 Deletes a previously created variable object and all of its children.
26128 With the @samp{-c} option, just deletes the children.
26130 Returns an error if the object @var{name} is not found.
26133 @subheading The @code{-var-set-format} Command
26134 @findex -var-set-format
26136 @subsubheading Synopsis
26139 -var-set-format @var{name} @var{format-spec}
26142 Sets the output format for the value of the object @var{name} to be
26145 @anchor{-var-set-format}
26146 The syntax for the @var{format-spec} is as follows:
26149 @var{format-spec} @expansion{}
26150 @{binary | decimal | hexadecimal | octal | natural@}
26153 The natural format is the default format choosen automatically
26154 based on the variable type (like decimal for an @code{int}, hex
26155 for pointers, etc.).
26157 For a variable with children, the format is set only on the
26158 variable itself, and the children are not affected.
26160 @subheading The @code{-var-show-format} Command
26161 @findex -var-show-format
26163 @subsubheading Synopsis
26166 -var-show-format @var{name}
26169 Returns the format used to display the value of the object @var{name}.
26172 @var{format} @expansion{}
26177 @subheading The @code{-var-info-num-children} Command
26178 @findex -var-info-num-children
26180 @subsubheading Synopsis
26183 -var-info-num-children @var{name}
26186 Returns the number of children of a variable object @var{name}:
26192 Note that this number is not completely reliable for a dynamic varobj.
26193 It will return the current number of children, but more children may
26197 @subheading The @code{-var-list-children} Command
26198 @findex -var-list-children
26200 @subsubheading Synopsis
26203 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26205 @anchor{-var-list-children}
26207 Return a list of the children of the specified variable object and
26208 create variable objects for them, if they do not already exist. With
26209 a single argument or if @var{print-values} has a value for of 0 or
26210 @code{--no-values}, print only the names of the variables; if
26211 @var{print-values} is 1 or @code{--all-values}, also print their
26212 values; and if it is 2 or @code{--simple-values} print the name and
26213 value for simple data types and just the name for arrays, structures
26216 @var{from} and @var{to}, if specified, indicate the range of children
26217 to report. If @var{from} or @var{to} is less than zero, the range is
26218 reset and all children will be reported. Otherwise, children starting
26219 at @var{from} (zero-based) and up to and excluding @var{to} will be
26222 If a child range is requested, it will only affect the current call to
26223 @code{-var-list-children}, but not future calls to @code{-var-update}.
26224 For this, you must instead use @code{-var-set-update-range}. The
26225 intent of this approach is to enable a front end to implement any
26226 update approach it likes; for example, scrolling a view may cause the
26227 front end to request more children with @code{-var-list-children}, and
26228 then the front end could call @code{-var-set-update-range} with a
26229 different range to ensure that future updates are restricted to just
26232 For each child the following results are returned:
26237 Name of the variable object created for this child.
26240 The expression to be shown to the user by the front end to designate this child.
26241 For example this may be the name of a structure member.
26243 For a dynamic varobj, this value cannot be used to form an
26244 expression. There is no way to do this at all with a dynamic varobj.
26246 For C/C@t{++} structures there are several pseudo children returned to
26247 designate access qualifiers. For these pseudo children @var{exp} is
26248 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26249 type and value are not present.
26251 A dynamic varobj will not report the access qualifying
26252 pseudo-children, regardless of the language. This information is not
26253 available at all with a dynamic varobj.
26256 Number of children this child has. For a dynamic varobj, this will be
26260 The type of the child.
26263 If values were requested, this is the value.
26266 If this variable object is associated with a thread, this is the thread id.
26267 Otherwise this result is not present.
26270 If the variable object is frozen, this variable will be present with a value of 1.
26273 The result may have its own attributes:
26277 A dynamic varobj can supply a display hint to the front end. The
26278 value comes directly from the Python pretty-printer object's
26279 @code{display_hint} method. @xref{Pretty Printing API}.
26282 This is an integer attribute which is nonzero if there are children
26283 remaining after the end of the selected range.
26286 @subsubheading Example
26290 -var-list-children n
26291 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26292 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26294 -var-list-children --all-values n
26295 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26296 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26300 @subheading The @code{-var-info-type} Command
26301 @findex -var-info-type
26303 @subsubheading Synopsis
26306 -var-info-type @var{name}
26309 Returns the type of the specified variable @var{name}. The type is
26310 returned as a string in the same format as it is output by the
26314 type=@var{typename}
26318 @subheading The @code{-var-info-expression} Command
26319 @findex -var-info-expression
26321 @subsubheading Synopsis
26324 -var-info-expression @var{name}
26327 Returns a string that is suitable for presenting this
26328 variable object in user interface. The string is generally
26329 not valid expression in the current language, and cannot be evaluated.
26331 For example, if @code{a} is an array, and variable object
26332 @code{A} was created for @code{a}, then we'll get this output:
26335 (gdb) -var-info-expression A.1
26336 ^done,lang="C",exp="1"
26340 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26342 Note that the output of the @code{-var-list-children} command also
26343 includes those expressions, so the @code{-var-info-expression} command
26346 @subheading The @code{-var-info-path-expression} Command
26347 @findex -var-info-path-expression
26349 @subsubheading Synopsis
26352 -var-info-path-expression @var{name}
26355 Returns an expression that can be evaluated in the current
26356 context and will yield the same value that a variable object has.
26357 Compare this with the @code{-var-info-expression} command, which
26358 result can be used only for UI presentation. Typical use of
26359 the @code{-var-info-path-expression} command is creating a
26360 watchpoint from a variable object.
26362 This command is currently not valid for children of a dynamic varobj,
26363 and will give an error when invoked on one.
26365 For example, suppose @code{C} is a C@t{++} class, derived from class
26366 @code{Base}, and that the @code{Base} class has a member called
26367 @code{m_size}. Assume a variable @code{c} is has the type of
26368 @code{C} and a variable object @code{C} was created for variable
26369 @code{c}. Then, we'll get this output:
26371 (gdb) -var-info-path-expression C.Base.public.m_size
26372 ^done,path_expr=((Base)c).m_size)
26375 @subheading The @code{-var-show-attributes} Command
26376 @findex -var-show-attributes
26378 @subsubheading Synopsis
26381 -var-show-attributes @var{name}
26384 List attributes of the specified variable object @var{name}:
26387 status=@var{attr} [ ( ,@var{attr} )* ]
26391 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26393 @subheading The @code{-var-evaluate-expression} Command
26394 @findex -var-evaluate-expression
26396 @subsubheading Synopsis
26399 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26402 Evaluates the expression that is represented by the specified variable
26403 object and returns its value as a string. The format of the string
26404 can be specified with the @samp{-f} option. The possible values of
26405 this option are the same as for @code{-var-set-format}
26406 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26407 the current display format will be used. The current display format
26408 can be changed using the @code{-var-set-format} command.
26414 Note that one must invoke @code{-var-list-children} for a variable
26415 before the value of a child variable can be evaluated.
26417 @subheading The @code{-var-assign} Command
26418 @findex -var-assign
26420 @subsubheading Synopsis
26423 -var-assign @var{name} @var{expression}
26426 Assigns the value of @var{expression} to the variable object specified
26427 by @var{name}. The object must be @samp{editable}. If the variable's
26428 value is altered by the assign, the variable will show up in any
26429 subsequent @code{-var-update} list.
26431 @subsubheading Example
26439 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26443 @subheading The @code{-var-update} Command
26444 @findex -var-update
26446 @subsubheading Synopsis
26449 -var-update [@var{print-values}] @{@var{name} | "*"@}
26452 Reevaluate the expressions corresponding to the variable object
26453 @var{name} and all its direct and indirect children, and return the
26454 list of variable objects whose values have changed; @var{name} must
26455 be a root variable object. Here, ``changed'' means that the result of
26456 @code{-var-evaluate-expression} before and after the
26457 @code{-var-update} is different. If @samp{*} is used as the variable
26458 object names, all existing variable objects are updated, except
26459 for frozen ones (@pxref{-var-set-frozen}). The option
26460 @var{print-values} determines whether both names and values, or just
26461 names are printed. The possible values of this option are the same
26462 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26463 recommended to use the @samp{--all-values} option, to reduce the
26464 number of MI commands needed on each program stop.
26466 With the @samp{*} parameter, if a variable object is bound to a
26467 currently running thread, it will not be updated, without any
26470 If @code{-var-set-update-range} was previously used on a varobj, then
26471 only the selected range of children will be reported.
26473 @code{-var-update} reports all the changed varobjs in a tuple named
26476 Each item in the change list is itself a tuple holding:
26480 The name of the varobj.
26483 If values were requested for this update, then this field will be
26484 present and will hold the value of the varobj.
26487 @anchor{-var-update}
26488 This field is a string which may take one of three values:
26492 The variable object's current value is valid.
26495 The variable object does not currently hold a valid value but it may
26496 hold one in the future if its associated expression comes back into
26500 The variable object no longer holds a valid value.
26501 This can occur when the executable file being debugged has changed,
26502 either through recompilation or by using the @value{GDBN} @code{file}
26503 command. The front end should normally choose to delete these variable
26507 In the future new values may be added to this list so the front should
26508 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26511 This is only present if the varobj is still valid. If the type
26512 changed, then this will be the string @samp{true}; otherwise it will
26516 If the varobj's type changed, then this field will be present and will
26519 @item new_num_children
26520 For a dynamic varobj, if the number of children changed, or if the
26521 type changed, this will be the new number of children.
26523 The @samp{numchild} field in other varobj responses is generally not
26524 valid for a dynamic varobj -- it will show the number of children that
26525 @value{GDBN} knows about, but because dynamic varobjs lazily
26526 instantiate their children, this will not reflect the number of
26527 children which may be available.
26529 The @samp{new_num_children} attribute only reports changes to the
26530 number of children known by @value{GDBN}. This is the only way to
26531 detect whether an update has removed children (which necessarily can
26532 only happen at the end of the update range).
26535 The display hint, if any.
26538 This is an integer value, which will be 1 if there are more children
26539 available outside the varobj's update range.
26542 This attribute will be present and have the value @samp{1} if the
26543 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26544 then this attribute will not be present.
26547 If new children were added to a dynamic varobj within the selected
26548 update range (as set by @code{-var-set-update-range}), then they will
26549 be listed in this attribute.
26552 @subsubheading Example
26559 -var-update --all-values var1
26560 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26561 type_changed="false"@}]
26565 @subheading The @code{-var-set-frozen} Command
26566 @findex -var-set-frozen
26567 @anchor{-var-set-frozen}
26569 @subsubheading Synopsis
26572 -var-set-frozen @var{name} @var{flag}
26575 Set the frozenness flag on the variable object @var{name}. The
26576 @var{flag} parameter should be either @samp{1} to make the variable
26577 frozen or @samp{0} to make it unfrozen. If a variable object is
26578 frozen, then neither itself, nor any of its children, are
26579 implicitly updated by @code{-var-update} of
26580 a parent variable or by @code{-var-update *}. Only
26581 @code{-var-update} of the variable itself will update its value and
26582 values of its children. After a variable object is unfrozen, it is
26583 implicitly updated by all subsequent @code{-var-update} operations.
26584 Unfreezing a variable does not update it, only subsequent
26585 @code{-var-update} does.
26587 @subsubheading Example
26591 -var-set-frozen V 1
26596 @subheading The @code{-var-set-update-range} command
26597 @findex -var-set-update-range
26598 @anchor{-var-set-update-range}
26600 @subsubheading Synopsis
26603 -var-set-update-range @var{name} @var{from} @var{to}
26606 Set the range of children to be returned by future invocations of
26607 @code{-var-update}.
26609 @var{from} and @var{to} indicate the range of children to report. If
26610 @var{from} or @var{to} is less than zero, the range is reset and all
26611 children will be reported. Otherwise, children starting at @var{from}
26612 (zero-based) and up to and excluding @var{to} will be reported.
26614 @subsubheading Example
26618 -var-set-update-range V 1 2
26622 @subheading The @code{-var-set-visualizer} command
26623 @findex -var-set-visualizer
26624 @anchor{-var-set-visualizer}
26626 @subsubheading Synopsis
26629 -var-set-visualizer @var{name} @var{visualizer}
26632 Set a visualizer for the variable object @var{name}.
26634 @var{visualizer} is the visualizer to use. The special value
26635 @samp{None} means to disable any visualizer in use.
26637 If not @samp{None}, @var{visualizer} must be a Python expression.
26638 This expression must evaluate to a callable object which accepts a
26639 single argument. @value{GDBN} will call this object with the value of
26640 the varobj @var{name} as an argument (this is done so that the same
26641 Python pretty-printing code can be used for both the CLI and MI).
26642 When called, this object must return an object which conforms to the
26643 pretty-printing interface (@pxref{Pretty Printing API}).
26645 The pre-defined function @code{gdb.default_visualizer} may be used to
26646 select a visualizer by following the built-in process
26647 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26648 a varobj is created, and so ordinarily is not needed.
26650 This feature is only available if Python support is enabled. The MI
26651 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26652 can be used to check this.
26654 @subsubheading Example
26656 Resetting the visualizer:
26660 -var-set-visualizer V None
26664 Reselecting the default (type-based) visualizer:
26668 -var-set-visualizer V gdb.default_visualizer
26672 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26673 can be used to instantiate this class for a varobj:
26677 -var-set-visualizer V "lambda val: SomeClass()"
26681 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26682 @node GDB/MI Data Manipulation
26683 @section @sc{gdb/mi} Data Manipulation
26685 @cindex data manipulation, in @sc{gdb/mi}
26686 @cindex @sc{gdb/mi}, data manipulation
26687 This section describes the @sc{gdb/mi} commands that manipulate data:
26688 examine memory and registers, evaluate expressions, etc.
26690 @c REMOVED FROM THE INTERFACE.
26691 @c @subheading -data-assign
26692 @c Change the value of a program variable. Plenty of side effects.
26693 @c @subsubheading GDB Command
26695 @c @subsubheading Example
26698 @subheading The @code{-data-disassemble} Command
26699 @findex -data-disassemble
26701 @subsubheading Synopsis
26705 [ -s @var{start-addr} -e @var{end-addr} ]
26706 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26714 @item @var{start-addr}
26715 is the beginning address (or @code{$pc})
26716 @item @var{end-addr}
26718 @item @var{filename}
26719 is the name of the file to disassemble
26720 @item @var{linenum}
26721 is the line number to disassemble around
26723 is the number of disassembly lines to be produced. If it is -1,
26724 the whole function will be disassembled, in case no @var{end-addr} is
26725 specified. If @var{end-addr} is specified as a non-zero value, and
26726 @var{lines} is lower than the number of disassembly lines between
26727 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26728 displayed; if @var{lines} is higher than the number of lines between
26729 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26732 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26736 @subsubheading Result
26738 The output for each instruction is composed of four fields:
26747 Note that whatever included in the instruction field, is not manipulated
26748 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26750 @subsubheading @value{GDBN} Command
26752 There's no direct mapping from this command to the CLI.
26754 @subsubheading Example
26756 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26760 -data-disassemble -s $pc -e "$pc + 20" -- 0
26763 @{address="0x000107c0",func-name="main",offset="4",
26764 inst="mov 2, %o0"@},
26765 @{address="0x000107c4",func-name="main",offset="8",
26766 inst="sethi %hi(0x11800), %o2"@},
26767 @{address="0x000107c8",func-name="main",offset="12",
26768 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26769 @{address="0x000107cc",func-name="main",offset="16",
26770 inst="sethi %hi(0x11800), %o2"@},
26771 @{address="0x000107d0",func-name="main",offset="20",
26772 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26776 Disassemble the whole @code{main} function. Line 32 is part of
26780 -data-disassemble -f basics.c -l 32 -- 0
26782 @{address="0x000107bc",func-name="main",offset="0",
26783 inst="save %sp, -112, %sp"@},
26784 @{address="0x000107c0",func-name="main",offset="4",
26785 inst="mov 2, %o0"@},
26786 @{address="0x000107c4",func-name="main",offset="8",
26787 inst="sethi %hi(0x11800), %o2"@},
26789 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26790 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26794 Disassemble 3 instructions from the start of @code{main}:
26798 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26800 @{address="0x000107bc",func-name="main",offset="0",
26801 inst="save %sp, -112, %sp"@},
26802 @{address="0x000107c0",func-name="main",offset="4",
26803 inst="mov 2, %o0"@},
26804 @{address="0x000107c4",func-name="main",offset="8",
26805 inst="sethi %hi(0x11800), %o2"@}]
26809 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26813 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26815 src_and_asm_line=@{line="31",
26816 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26817 testsuite/gdb.mi/basics.c",line_asm_insn=[
26818 @{address="0x000107bc",func-name="main",offset="0",
26819 inst="save %sp, -112, %sp"@}]@},
26820 src_and_asm_line=@{line="32",
26821 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26822 testsuite/gdb.mi/basics.c",line_asm_insn=[
26823 @{address="0x000107c0",func-name="main",offset="4",
26824 inst="mov 2, %o0"@},
26825 @{address="0x000107c4",func-name="main",offset="8",
26826 inst="sethi %hi(0x11800), %o2"@}]@}]
26831 @subheading The @code{-data-evaluate-expression} Command
26832 @findex -data-evaluate-expression
26834 @subsubheading Synopsis
26837 -data-evaluate-expression @var{expr}
26840 Evaluate @var{expr} as an expression. The expression could contain an
26841 inferior function call. The function call will execute synchronously.
26842 If the expression contains spaces, it must be enclosed in double quotes.
26844 @subsubheading @value{GDBN} Command
26846 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26847 @samp{call}. In @code{gdbtk} only, there's a corresponding
26848 @samp{gdb_eval} command.
26850 @subsubheading Example
26852 In the following example, the numbers that precede the commands are the
26853 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26854 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26858 211-data-evaluate-expression A
26861 311-data-evaluate-expression &A
26862 311^done,value="0xefffeb7c"
26864 411-data-evaluate-expression A+3
26867 511-data-evaluate-expression "A + 3"
26873 @subheading The @code{-data-list-changed-registers} Command
26874 @findex -data-list-changed-registers
26876 @subsubheading Synopsis
26879 -data-list-changed-registers
26882 Display a list of the registers that have changed.
26884 @subsubheading @value{GDBN} Command
26886 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26887 has the corresponding command @samp{gdb_changed_register_list}.
26889 @subsubheading Example
26891 On a PPC MBX board:
26899 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26900 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26903 -data-list-changed-registers
26904 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26905 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26906 "24","25","26","27","28","30","31","64","65","66","67","69"]
26911 @subheading The @code{-data-list-register-names} Command
26912 @findex -data-list-register-names
26914 @subsubheading Synopsis
26917 -data-list-register-names [ ( @var{regno} )+ ]
26920 Show a list of register names for the current target. If no arguments
26921 are given, it shows a list of the names of all the registers. If
26922 integer numbers are given as arguments, it will print a list of the
26923 names of the registers corresponding to the arguments. To ensure
26924 consistency between a register name and its number, the output list may
26925 include empty register names.
26927 @subsubheading @value{GDBN} Command
26929 @value{GDBN} does not have a command which corresponds to
26930 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26931 corresponding command @samp{gdb_regnames}.
26933 @subsubheading Example
26935 For the PPC MBX board:
26938 -data-list-register-names
26939 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26940 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26941 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26942 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26943 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26944 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26945 "", "pc","ps","cr","lr","ctr","xer"]
26947 -data-list-register-names 1 2 3
26948 ^done,register-names=["r1","r2","r3"]
26952 @subheading The @code{-data-list-register-values} Command
26953 @findex -data-list-register-values
26955 @subsubheading Synopsis
26958 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26961 Display the registers' contents. @var{fmt} is the format according to
26962 which the registers' contents are to be returned, followed by an optional
26963 list of numbers specifying the registers to display. A missing list of
26964 numbers indicates that the contents of all the registers must be returned.
26966 Allowed formats for @var{fmt} are:
26983 @subsubheading @value{GDBN} Command
26985 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26986 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26988 @subsubheading Example
26990 For a PPC MBX board (note: line breaks are for readability only, they
26991 don't appear in the actual output):
26995 -data-list-register-values r 64 65
26996 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26997 @{number="65",value="0x00029002"@}]
26999 -data-list-register-values x
27000 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27001 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27002 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27003 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27004 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27005 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27006 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27007 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27008 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27009 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27010 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27011 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27012 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27013 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27014 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27015 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27016 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27017 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27018 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27019 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27020 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27021 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27022 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27023 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27024 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27025 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27026 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27027 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27028 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27029 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27030 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27031 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27032 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27033 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27034 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27035 @{number="69",value="0x20002b03"@}]
27040 @subheading The @code{-data-read-memory} Command
27041 @findex -data-read-memory
27043 @subsubheading Synopsis
27046 -data-read-memory [ -o @var{byte-offset} ]
27047 @var{address} @var{word-format} @var{word-size}
27048 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27055 @item @var{address}
27056 An expression specifying the address of the first memory word to be
27057 read. Complex expressions containing embedded white space should be
27058 quoted using the C convention.
27060 @item @var{word-format}
27061 The format to be used to print the memory words. The notation is the
27062 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27065 @item @var{word-size}
27066 The size of each memory word in bytes.
27068 @item @var{nr-rows}
27069 The number of rows in the output table.
27071 @item @var{nr-cols}
27072 The number of columns in the output table.
27075 If present, indicates that each row should include an @sc{ascii} dump. The
27076 value of @var{aschar} is used as a padding character when a byte is not a
27077 member of the printable @sc{ascii} character set (printable @sc{ascii}
27078 characters are those whose code is between 32 and 126, inclusively).
27080 @item @var{byte-offset}
27081 An offset to add to the @var{address} before fetching memory.
27084 This command displays memory contents as a table of @var{nr-rows} by
27085 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27086 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27087 (returned as @samp{total-bytes}). Should less than the requested number
27088 of bytes be returned by the target, the missing words are identified
27089 using @samp{N/A}. The number of bytes read from the target is returned
27090 in @samp{nr-bytes} and the starting address used to read memory in
27093 The address of the next/previous row or page is available in
27094 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27097 @subsubheading @value{GDBN} Command
27099 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27100 @samp{gdb_get_mem} memory read command.
27102 @subsubheading Example
27104 Read six bytes of memory starting at @code{bytes+6} but then offset by
27105 @code{-6} bytes. Format as three rows of two columns. One byte per
27106 word. Display each word in hex.
27110 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27111 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27112 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27113 prev-page="0x0000138a",memory=[
27114 @{addr="0x00001390",data=["0x00","0x01"]@},
27115 @{addr="0x00001392",data=["0x02","0x03"]@},
27116 @{addr="0x00001394",data=["0x04","0x05"]@}]
27120 Read two bytes of memory starting at address @code{shorts + 64} and
27121 display as a single word formatted in decimal.
27125 5-data-read-memory shorts+64 d 2 1 1
27126 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27127 next-row="0x00001512",prev-row="0x0000150e",
27128 next-page="0x00001512",prev-page="0x0000150e",memory=[
27129 @{addr="0x00001510",data=["128"]@}]
27133 Read thirty two bytes of memory starting at @code{bytes+16} and format
27134 as eight rows of four columns. Include a string encoding with @samp{x}
27135 used as the non-printable character.
27139 4-data-read-memory bytes+16 x 1 8 4 x
27140 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27141 next-row="0x000013c0",prev-row="0x0000139c",
27142 next-page="0x000013c0",prev-page="0x00001380",memory=[
27143 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27144 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27145 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27146 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27147 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27148 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27149 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27150 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27155 @node GDB/MI Tracepoint Commands
27156 @section @sc{gdb/mi} Tracepoint Commands
27158 The commands defined in this section implement MI support for
27159 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27161 @subheading The @code{-trace-find} Command
27162 @findex -trace-find
27164 @subsubheading Synopsis
27167 -trace-find @var{mode} [@var{parameters}@dots{}]
27170 Find a trace frame using criteria defined by @var{mode} and
27171 @var{parameters}. The following table lists permissible
27172 modes and their parameters. For details of operation, see @ref{tfind}.
27177 No parameters are required. Stops examining trace frames.
27180 An integer is required as parameter. Selects tracepoint frame with
27183 @item tracepoint-number
27184 An integer is required as parameter. Finds next
27185 trace frame that corresponds to tracepoint with the specified number.
27188 An address is required as parameter. Finds
27189 next trace frame that corresponds to any tracepoint at the specified
27192 @item pc-inside-range
27193 Two addresses are required as parameters. Finds next trace
27194 frame that corresponds to a tracepoint at an address inside the
27195 specified range. Both bounds are considered to be inside the range.
27197 @item pc-outside-range
27198 Two addresses are required as parameters. Finds
27199 next trace frame that corresponds to a tracepoint at an address outside
27200 the specified range. Both bounds are considered to be inside the range.
27203 Line specification is required as parameter. @xref{Specify Location}.
27204 Finds next trace frame that corresponds to a tracepoint at
27205 the specified location.
27209 If @samp{none} was passed as @var{mode}, the response does not
27210 have fields. Otherwise, the response may have the following fields:
27214 This field has either @samp{0} or @samp{1} as the value, depending
27215 on whether a matching tracepoint was found.
27218 The index of the found traceframe. This field is present iff
27219 the @samp{found} field has value of @samp{1}.
27222 The index of the found tracepoint. This field is present iff
27223 the @samp{found} field has value of @samp{1}.
27226 The information about the frame corresponding to the found trace
27227 frame. This field is present only if a trace frame was found.
27228 @xref{GDB/MI Frame Information}, for description of this field.
27232 @subsubheading @value{GDBN} Command
27234 The corresponding @value{GDBN} command is @samp{tfind}.
27236 @subheading -trace-define-variable
27237 @findex -trace-define-variable
27239 @subsubheading Synopsis
27242 -trace-define-variable @var{name} [ @var{value} ]
27245 Create trace variable @var{name} if it does not exist. If
27246 @var{value} is specified, sets the initial value of the specified
27247 trace variable to that value. Note that the @var{name} should start
27248 with the @samp{$} character.
27250 @subsubheading @value{GDBN} Command
27252 The corresponding @value{GDBN} command is @samp{tvariable}.
27254 @subheading -trace-list-variables
27255 @findex -trace-list-variables
27257 @subsubheading Synopsis
27260 -trace-list-variables
27263 Return a table of all defined trace variables. Each element of the
27264 table has the following fields:
27268 The name of the trace variable. This field is always present.
27271 The initial value. This is a 64-bit signed integer. This
27272 field is always present.
27275 The value the trace variable has at the moment. This is a 64-bit
27276 signed integer. This field is absent iff current value is
27277 not defined, for example if the trace was never run, or is
27282 @subsubheading @value{GDBN} Command
27284 The corresponding @value{GDBN} command is @samp{tvariables}.
27286 @subsubheading Example
27290 -trace-list-variables
27291 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27292 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27293 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27294 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27295 body=[variable=@{name="$trace_timestamp",initial="0"@}
27296 variable=@{name="$foo",initial="10",current="15"@}]@}
27300 @subheading -trace-save
27301 @findex -trace-save
27303 @subsubheading Synopsis
27306 -trace-save [-r ] @var{filename}
27309 Saves the collected trace data to @var{filename}. Without the
27310 @samp{-r} option, the data is downloaded from the target and saved
27311 in a local file. With the @samp{-r} option the target is asked
27312 to perform the save.
27314 @subsubheading @value{GDBN} Command
27316 The corresponding @value{GDBN} command is @samp{tsave}.
27319 @subheading -trace-start
27320 @findex -trace-start
27322 @subsubheading Synopsis
27328 Starts a tracing experiments. The result of this command does not
27331 @subsubheading @value{GDBN} Command
27333 The corresponding @value{GDBN} command is @samp{tstart}.
27335 @subheading -trace-status
27336 @findex -trace-status
27338 @subsubheading Synopsis
27344 Obtains the status of a tracing experiment. The result may include
27345 the following fields:
27350 May have a value of either @samp{0}, when no tracing operations are
27351 supported, @samp{1}, when all tracing operations are supported, or
27352 @samp{file} when examining trace file. In the latter case, examining
27353 of trace frame is possible but new tracing experiement cannot be
27354 started. This field is always present.
27357 May have a value of either @samp{0} or @samp{1} depending on whether
27358 tracing experiement is in progress on target. This field is present
27359 if @samp{supported} field is not @samp{0}.
27362 Report the reason why the tracing was stopped last time. This field
27363 may be absent iff tracing was never stopped on target yet. The
27364 value of @samp{request} means the tracing was stopped as result of
27365 the @code{-trace-stop} command. The value of @samp{overflow} means
27366 the tracing buffer is full. The value of @samp{disconnection} means
27367 tracing was automatically stopped when @value{GDBN} has disconnected.
27368 The value of @samp{passcount} means tracing was stopped when a
27369 tracepoint was passed a maximal number of times for that tracepoint.
27370 This field is present if @samp{supported} field is not @samp{0}.
27372 @item stopping-tracepoint
27373 The number of tracepoint whose passcount as exceeded. This field is
27374 present iff the @samp{stop-reason} field has the value of
27378 @itemx frames-created
27379 The @samp{frames} field is a count of the total number of trace frames
27380 in the trace buffer, while @samp{frames-created} is the total created
27381 during the run, including ones that were discarded, such as when a
27382 circular trace buffer filled up. Both fields are optional.
27386 These fields tell the current size of the tracing buffer and the
27387 remaining space. These fields are optional.
27390 The value of the circular trace buffer flag. @code{1} means that the
27391 trace buffer is circular and old trace frames will be discarded if
27392 necessary to make room, @code{0} means that the trace buffer is linear
27396 The value of the disconnected tracing flag. @code{1} means that
27397 tracing will continue after @value{GDBN} disconnects, @code{0} means
27398 that the trace run will stop.
27402 @subsubheading @value{GDBN} Command
27404 The corresponding @value{GDBN} command is @samp{tstatus}.
27406 @subheading -trace-stop
27407 @findex -trace-stop
27409 @subsubheading Synopsis
27415 Stops a tracing experiment. The result of this command has the same
27416 fields as @code{-trace-status}, except that the @samp{supported} and
27417 @samp{running} fields are not output.
27419 @subsubheading @value{GDBN} Command
27421 The corresponding @value{GDBN} command is @samp{tstop}.
27424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27425 @node GDB/MI Symbol Query
27426 @section @sc{gdb/mi} Symbol Query Commands
27430 @subheading The @code{-symbol-info-address} Command
27431 @findex -symbol-info-address
27433 @subsubheading Synopsis
27436 -symbol-info-address @var{symbol}
27439 Describe where @var{symbol} is stored.
27441 @subsubheading @value{GDBN} Command
27443 The corresponding @value{GDBN} command is @samp{info address}.
27445 @subsubheading Example
27449 @subheading The @code{-symbol-info-file} Command
27450 @findex -symbol-info-file
27452 @subsubheading Synopsis
27458 Show the file for the symbol.
27460 @subsubheading @value{GDBN} Command
27462 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27463 @samp{gdb_find_file}.
27465 @subsubheading Example
27469 @subheading The @code{-symbol-info-function} Command
27470 @findex -symbol-info-function
27472 @subsubheading Synopsis
27475 -symbol-info-function
27478 Show which function the symbol lives in.
27480 @subsubheading @value{GDBN} Command
27482 @samp{gdb_get_function} in @code{gdbtk}.
27484 @subsubheading Example
27488 @subheading The @code{-symbol-info-line} Command
27489 @findex -symbol-info-line
27491 @subsubheading Synopsis
27497 Show the core addresses of the code for a source line.
27499 @subsubheading @value{GDBN} Command
27501 The corresponding @value{GDBN} command is @samp{info line}.
27502 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27504 @subsubheading Example
27508 @subheading The @code{-symbol-info-symbol} Command
27509 @findex -symbol-info-symbol
27511 @subsubheading Synopsis
27514 -symbol-info-symbol @var{addr}
27517 Describe what symbol is at location @var{addr}.
27519 @subsubheading @value{GDBN} Command
27521 The corresponding @value{GDBN} command is @samp{info symbol}.
27523 @subsubheading Example
27527 @subheading The @code{-symbol-list-functions} Command
27528 @findex -symbol-list-functions
27530 @subsubheading Synopsis
27533 -symbol-list-functions
27536 List the functions in the executable.
27538 @subsubheading @value{GDBN} Command
27540 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27541 @samp{gdb_search} in @code{gdbtk}.
27543 @subsubheading Example
27548 @subheading The @code{-symbol-list-lines} Command
27549 @findex -symbol-list-lines
27551 @subsubheading Synopsis
27554 -symbol-list-lines @var{filename}
27557 Print the list of lines that contain code and their associated program
27558 addresses for the given source filename. The entries are sorted in
27559 ascending PC order.
27561 @subsubheading @value{GDBN} Command
27563 There is no corresponding @value{GDBN} command.
27565 @subsubheading Example
27568 -symbol-list-lines basics.c
27569 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27575 @subheading The @code{-symbol-list-types} Command
27576 @findex -symbol-list-types
27578 @subsubheading Synopsis
27584 List all the type names.
27586 @subsubheading @value{GDBN} Command
27588 The corresponding commands are @samp{info types} in @value{GDBN},
27589 @samp{gdb_search} in @code{gdbtk}.
27591 @subsubheading Example
27595 @subheading The @code{-symbol-list-variables} Command
27596 @findex -symbol-list-variables
27598 @subsubheading Synopsis
27601 -symbol-list-variables
27604 List all the global and static variable names.
27606 @subsubheading @value{GDBN} Command
27608 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27610 @subsubheading Example
27614 @subheading The @code{-symbol-locate} Command
27615 @findex -symbol-locate
27617 @subsubheading Synopsis
27623 @subsubheading @value{GDBN} Command
27625 @samp{gdb_loc} in @code{gdbtk}.
27627 @subsubheading Example
27631 @subheading The @code{-symbol-type} Command
27632 @findex -symbol-type
27634 @subsubheading Synopsis
27637 -symbol-type @var{variable}
27640 Show type of @var{variable}.
27642 @subsubheading @value{GDBN} Command
27644 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27645 @samp{gdb_obj_variable}.
27647 @subsubheading Example
27652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27653 @node GDB/MI File Commands
27654 @section @sc{gdb/mi} File Commands
27656 This section describes the GDB/MI commands to specify executable file names
27657 and to read in and obtain symbol table information.
27659 @subheading The @code{-file-exec-and-symbols} Command
27660 @findex -file-exec-and-symbols
27662 @subsubheading Synopsis
27665 -file-exec-and-symbols @var{file}
27668 Specify the executable file to be debugged. This file is the one from
27669 which the symbol table is also read. If no file is specified, the
27670 command clears the executable and symbol information. If breakpoints
27671 are set when using this command with no arguments, @value{GDBN} will produce
27672 error messages. Otherwise, no output is produced, except a completion
27675 @subsubheading @value{GDBN} Command
27677 The corresponding @value{GDBN} command is @samp{file}.
27679 @subsubheading Example
27683 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27689 @subheading The @code{-file-exec-file} Command
27690 @findex -file-exec-file
27692 @subsubheading Synopsis
27695 -file-exec-file @var{file}
27698 Specify the executable file to be debugged. Unlike
27699 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27700 from this file. If used without argument, @value{GDBN} clears the information
27701 about the executable file. No output is produced, except a completion
27704 @subsubheading @value{GDBN} Command
27706 The corresponding @value{GDBN} command is @samp{exec-file}.
27708 @subsubheading Example
27712 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27719 @subheading The @code{-file-list-exec-sections} Command
27720 @findex -file-list-exec-sections
27722 @subsubheading Synopsis
27725 -file-list-exec-sections
27728 List the sections of the current executable file.
27730 @subsubheading @value{GDBN} Command
27732 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27733 information as this command. @code{gdbtk} has a corresponding command
27734 @samp{gdb_load_info}.
27736 @subsubheading Example
27741 @subheading The @code{-file-list-exec-source-file} Command
27742 @findex -file-list-exec-source-file
27744 @subsubheading Synopsis
27747 -file-list-exec-source-file
27750 List the line number, the current source file, and the absolute path
27751 to the current source file for the current executable. The macro
27752 information field has a value of @samp{1} or @samp{0} depending on
27753 whether or not the file includes preprocessor macro information.
27755 @subsubheading @value{GDBN} Command
27757 The @value{GDBN} equivalent is @samp{info source}
27759 @subsubheading Example
27763 123-file-list-exec-source-file
27764 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27769 @subheading The @code{-file-list-exec-source-files} Command
27770 @findex -file-list-exec-source-files
27772 @subsubheading Synopsis
27775 -file-list-exec-source-files
27778 List the source files for the current executable.
27780 It will always output the filename, but only when @value{GDBN} can find
27781 the absolute file name of a source file, will it output the fullname.
27783 @subsubheading @value{GDBN} Command
27785 The @value{GDBN} equivalent is @samp{info sources}.
27786 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27788 @subsubheading Example
27791 -file-list-exec-source-files
27793 @{file=foo.c,fullname=/home/foo.c@},
27794 @{file=/home/bar.c,fullname=/home/bar.c@},
27795 @{file=gdb_could_not_find_fullpath.c@}]
27800 @subheading The @code{-file-list-shared-libraries} Command
27801 @findex -file-list-shared-libraries
27803 @subsubheading Synopsis
27806 -file-list-shared-libraries
27809 List the shared libraries in the program.
27811 @subsubheading @value{GDBN} Command
27813 The corresponding @value{GDBN} command is @samp{info shared}.
27815 @subsubheading Example
27819 @subheading The @code{-file-list-symbol-files} Command
27820 @findex -file-list-symbol-files
27822 @subsubheading Synopsis
27825 -file-list-symbol-files
27830 @subsubheading @value{GDBN} Command
27832 The corresponding @value{GDBN} command is @samp{info file} (part of it).
27834 @subsubheading Example
27839 @subheading The @code{-file-symbol-file} Command
27840 @findex -file-symbol-file
27842 @subsubheading Synopsis
27845 -file-symbol-file @var{file}
27848 Read symbol table info from the specified @var{file} argument. When
27849 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27850 produced, except for a completion notification.
27852 @subsubheading @value{GDBN} Command
27854 The corresponding @value{GDBN} command is @samp{symbol-file}.
27856 @subsubheading Example
27860 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27867 @node GDB/MI Memory Overlay Commands
27868 @section @sc{gdb/mi} Memory Overlay Commands
27870 The memory overlay commands are not implemented.
27872 @c @subheading -overlay-auto
27874 @c @subheading -overlay-list-mapping-state
27876 @c @subheading -overlay-list-overlays
27878 @c @subheading -overlay-map
27880 @c @subheading -overlay-off
27882 @c @subheading -overlay-on
27884 @c @subheading -overlay-unmap
27886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27887 @node GDB/MI Signal Handling Commands
27888 @section @sc{gdb/mi} Signal Handling Commands
27890 Signal handling commands are not implemented.
27892 @c @subheading -signal-handle
27894 @c @subheading -signal-list-handle-actions
27896 @c @subheading -signal-list-signal-types
27900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27901 @node GDB/MI Target Manipulation
27902 @section @sc{gdb/mi} Target Manipulation Commands
27905 @subheading The @code{-target-attach} Command
27906 @findex -target-attach
27908 @subsubheading Synopsis
27911 -target-attach @var{pid} | @var{gid} | @var{file}
27914 Attach to a process @var{pid} or a file @var{file} outside of
27915 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27916 group, the id previously returned by
27917 @samp{-list-thread-groups --available} must be used.
27919 @subsubheading @value{GDBN} Command
27921 The corresponding @value{GDBN} command is @samp{attach}.
27923 @subsubheading Example
27927 =thread-created,id="1"
27928 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27934 @subheading The @code{-target-compare-sections} Command
27935 @findex -target-compare-sections
27937 @subsubheading Synopsis
27940 -target-compare-sections [ @var{section} ]
27943 Compare data of section @var{section} on target to the exec file.
27944 Without the argument, all sections are compared.
27946 @subsubheading @value{GDBN} Command
27948 The @value{GDBN} equivalent is @samp{compare-sections}.
27950 @subsubheading Example
27955 @subheading The @code{-target-detach} Command
27956 @findex -target-detach
27958 @subsubheading Synopsis
27961 -target-detach [ @var{pid} | @var{gid} ]
27964 Detach from the remote target which normally resumes its execution.
27965 If either @var{pid} or @var{gid} is specified, detaches from either
27966 the specified process, or specified thread group. There's no output.
27968 @subsubheading @value{GDBN} Command
27970 The corresponding @value{GDBN} command is @samp{detach}.
27972 @subsubheading Example
27982 @subheading The @code{-target-disconnect} Command
27983 @findex -target-disconnect
27985 @subsubheading Synopsis
27991 Disconnect from the remote target. There's no output and the target is
27992 generally not resumed.
27994 @subsubheading @value{GDBN} Command
27996 The corresponding @value{GDBN} command is @samp{disconnect}.
27998 @subsubheading Example
28008 @subheading The @code{-target-download} Command
28009 @findex -target-download
28011 @subsubheading Synopsis
28017 Loads the executable onto the remote target.
28018 It prints out an update message every half second, which includes the fields:
28022 The name of the section.
28024 The size of what has been sent so far for that section.
28026 The size of the section.
28028 The total size of what was sent so far (the current and the previous sections).
28030 The size of the overall executable to download.
28034 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28035 @sc{gdb/mi} Output Syntax}).
28037 In addition, it prints the name and size of the sections, as they are
28038 downloaded. These messages include the following fields:
28042 The name of the section.
28044 The size of the section.
28046 The size of the overall executable to download.
28050 At the end, a summary is printed.
28052 @subsubheading @value{GDBN} Command
28054 The corresponding @value{GDBN} command is @samp{load}.
28056 @subsubheading Example
28058 Note: each status message appears on a single line. Here the messages
28059 have been broken down so that they can fit onto a page.
28064 +download,@{section=".text",section-size="6668",total-size="9880"@}
28065 +download,@{section=".text",section-sent="512",section-size="6668",
28066 total-sent="512",total-size="9880"@}
28067 +download,@{section=".text",section-sent="1024",section-size="6668",
28068 total-sent="1024",total-size="9880"@}
28069 +download,@{section=".text",section-sent="1536",section-size="6668",
28070 total-sent="1536",total-size="9880"@}
28071 +download,@{section=".text",section-sent="2048",section-size="6668",
28072 total-sent="2048",total-size="9880"@}
28073 +download,@{section=".text",section-sent="2560",section-size="6668",
28074 total-sent="2560",total-size="9880"@}
28075 +download,@{section=".text",section-sent="3072",section-size="6668",
28076 total-sent="3072",total-size="9880"@}
28077 +download,@{section=".text",section-sent="3584",section-size="6668",
28078 total-sent="3584",total-size="9880"@}
28079 +download,@{section=".text",section-sent="4096",section-size="6668",
28080 total-sent="4096",total-size="9880"@}
28081 +download,@{section=".text",section-sent="4608",section-size="6668",
28082 total-sent="4608",total-size="9880"@}
28083 +download,@{section=".text",section-sent="5120",section-size="6668",
28084 total-sent="5120",total-size="9880"@}
28085 +download,@{section=".text",section-sent="5632",section-size="6668",
28086 total-sent="5632",total-size="9880"@}
28087 +download,@{section=".text",section-sent="6144",section-size="6668",
28088 total-sent="6144",total-size="9880"@}
28089 +download,@{section=".text",section-sent="6656",section-size="6668",
28090 total-sent="6656",total-size="9880"@}
28091 +download,@{section=".init",section-size="28",total-size="9880"@}
28092 +download,@{section=".fini",section-size="28",total-size="9880"@}
28093 +download,@{section=".data",section-size="3156",total-size="9880"@}
28094 +download,@{section=".data",section-sent="512",section-size="3156",
28095 total-sent="7236",total-size="9880"@}
28096 +download,@{section=".data",section-sent="1024",section-size="3156",
28097 total-sent="7748",total-size="9880"@}
28098 +download,@{section=".data",section-sent="1536",section-size="3156",
28099 total-sent="8260",total-size="9880"@}
28100 +download,@{section=".data",section-sent="2048",section-size="3156",
28101 total-sent="8772",total-size="9880"@}
28102 +download,@{section=".data",section-sent="2560",section-size="3156",
28103 total-sent="9284",total-size="9880"@}
28104 +download,@{section=".data",section-sent="3072",section-size="3156",
28105 total-sent="9796",total-size="9880"@}
28106 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28113 @subheading The @code{-target-exec-status} Command
28114 @findex -target-exec-status
28116 @subsubheading Synopsis
28119 -target-exec-status
28122 Provide information on the state of the target (whether it is running or
28123 not, for instance).
28125 @subsubheading @value{GDBN} Command
28127 There's no equivalent @value{GDBN} command.
28129 @subsubheading Example
28133 @subheading The @code{-target-list-available-targets} Command
28134 @findex -target-list-available-targets
28136 @subsubheading Synopsis
28139 -target-list-available-targets
28142 List the possible targets to connect to.
28144 @subsubheading @value{GDBN} Command
28146 The corresponding @value{GDBN} command is @samp{help target}.
28148 @subsubheading Example
28152 @subheading The @code{-target-list-current-targets} Command
28153 @findex -target-list-current-targets
28155 @subsubheading Synopsis
28158 -target-list-current-targets
28161 Describe the current target.
28163 @subsubheading @value{GDBN} Command
28165 The corresponding information is printed by @samp{info file} (among
28168 @subsubheading Example
28172 @subheading The @code{-target-list-parameters} Command
28173 @findex -target-list-parameters
28175 @subsubheading Synopsis
28178 -target-list-parameters
28184 @subsubheading @value{GDBN} Command
28188 @subsubheading Example
28192 @subheading The @code{-target-select} Command
28193 @findex -target-select
28195 @subsubheading Synopsis
28198 -target-select @var{type} @var{parameters @dots{}}
28201 Connect @value{GDBN} to the remote target. This command takes two args:
28205 The type of target, for instance @samp{remote}, etc.
28206 @item @var{parameters}
28207 Device names, host names and the like. @xref{Target Commands, ,
28208 Commands for Managing Targets}, for more details.
28211 The output is a connection notification, followed by the address at
28212 which the target program is, in the following form:
28215 ^connected,addr="@var{address}",func="@var{function name}",
28216 args=[@var{arg list}]
28219 @subsubheading @value{GDBN} Command
28221 The corresponding @value{GDBN} command is @samp{target}.
28223 @subsubheading Example
28227 -target-select remote /dev/ttya
28228 ^connected,addr="0xfe00a300",func="??",args=[]
28232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28233 @node GDB/MI File Transfer Commands
28234 @section @sc{gdb/mi} File Transfer Commands
28237 @subheading The @code{-target-file-put} Command
28238 @findex -target-file-put
28240 @subsubheading Synopsis
28243 -target-file-put @var{hostfile} @var{targetfile}
28246 Copy file @var{hostfile} from the host system (the machine running
28247 @value{GDBN}) to @var{targetfile} on the target system.
28249 @subsubheading @value{GDBN} Command
28251 The corresponding @value{GDBN} command is @samp{remote put}.
28253 @subsubheading Example
28257 -target-file-put localfile remotefile
28263 @subheading The @code{-target-file-get} Command
28264 @findex -target-file-get
28266 @subsubheading Synopsis
28269 -target-file-get @var{targetfile} @var{hostfile}
28272 Copy file @var{targetfile} from the target system to @var{hostfile}
28273 on the host system.
28275 @subsubheading @value{GDBN} Command
28277 The corresponding @value{GDBN} command is @samp{remote get}.
28279 @subsubheading Example
28283 -target-file-get remotefile localfile
28289 @subheading The @code{-target-file-delete} Command
28290 @findex -target-file-delete
28292 @subsubheading Synopsis
28295 -target-file-delete @var{targetfile}
28298 Delete @var{targetfile} from the target system.
28300 @subsubheading @value{GDBN} Command
28302 The corresponding @value{GDBN} command is @samp{remote delete}.
28304 @subsubheading Example
28308 -target-file-delete remotefile
28314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28315 @node GDB/MI Miscellaneous Commands
28316 @section Miscellaneous @sc{gdb/mi} Commands
28318 @c @subheading -gdb-complete
28320 @subheading The @code{-gdb-exit} Command
28323 @subsubheading Synopsis
28329 Exit @value{GDBN} immediately.
28331 @subsubheading @value{GDBN} Command
28333 Approximately corresponds to @samp{quit}.
28335 @subsubheading Example
28345 @subheading The @code{-exec-abort} Command
28346 @findex -exec-abort
28348 @subsubheading Synopsis
28354 Kill the inferior running program.
28356 @subsubheading @value{GDBN} Command
28358 The corresponding @value{GDBN} command is @samp{kill}.
28360 @subsubheading Example
28365 @subheading The @code{-gdb-set} Command
28368 @subsubheading Synopsis
28374 Set an internal @value{GDBN} variable.
28375 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28377 @subsubheading @value{GDBN} Command
28379 The corresponding @value{GDBN} command is @samp{set}.
28381 @subsubheading Example
28391 @subheading The @code{-gdb-show} Command
28394 @subsubheading Synopsis
28400 Show the current value of a @value{GDBN} variable.
28402 @subsubheading @value{GDBN} Command
28404 The corresponding @value{GDBN} command is @samp{show}.
28406 @subsubheading Example
28415 @c @subheading -gdb-source
28418 @subheading The @code{-gdb-version} Command
28419 @findex -gdb-version
28421 @subsubheading Synopsis
28427 Show version information for @value{GDBN}. Used mostly in testing.
28429 @subsubheading @value{GDBN} Command
28431 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28432 default shows this information when you start an interactive session.
28434 @subsubheading Example
28436 @c This example modifies the actual output from GDB to avoid overfull
28442 ~Copyright 2000 Free Software Foundation, Inc.
28443 ~GDB is free software, covered by the GNU General Public License, and
28444 ~you are welcome to change it and/or distribute copies of it under
28445 ~ certain conditions.
28446 ~Type "show copying" to see the conditions.
28447 ~There is absolutely no warranty for GDB. Type "show warranty" for
28449 ~This GDB was configured as
28450 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28455 @subheading The @code{-list-features} Command
28456 @findex -list-features
28458 Returns a list of particular features of the MI protocol that
28459 this version of gdb implements. A feature can be a command,
28460 or a new field in an output of some command, or even an
28461 important bugfix. While a frontend can sometimes detect presence
28462 of a feature at runtime, it is easier to perform detection at debugger
28465 The command returns a list of strings, with each string naming an
28466 available feature. Each returned string is just a name, it does not
28467 have any internal structure. The list of possible feature names
28473 (gdb) -list-features
28474 ^done,result=["feature1","feature2"]
28477 The current list of features is:
28480 @item frozen-varobjs
28481 Indicates presence of the @code{-var-set-frozen} command, as well
28482 as possible presense of the @code{frozen} field in the output
28483 of @code{-varobj-create}.
28484 @item pending-breakpoints
28485 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28487 Indicates presence of Python scripting support, Python-based
28488 pretty-printing commands, and possible presence of the
28489 @samp{display_hint} field in the output of @code{-var-list-children}
28491 Indicates presence of the @code{-thread-info} command.
28495 @subheading The @code{-list-target-features} Command
28496 @findex -list-target-features
28498 Returns a list of particular features that are supported by the
28499 target. Those features affect the permitted MI commands, but
28500 unlike the features reported by the @code{-list-features} command, the
28501 features depend on which target GDB is using at the moment. Whenever
28502 a target can change, due to commands such as @code{-target-select},
28503 @code{-target-attach} or @code{-exec-run}, the list of target features
28504 may change, and the frontend should obtain it again.
28508 (gdb) -list-features
28509 ^done,result=["async"]
28512 The current list of features is:
28516 Indicates that the target is capable of asynchronous command
28517 execution, which means that @value{GDBN} will accept further commands
28518 while the target is running.
28522 @subheading The @code{-list-thread-groups} Command
28523 @findex -list-thread-groups
28525 @subheading Synopsis
28528 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28531 Lists thread groups (@pxref{Thread groups}). When a single thread
28532 group is passed as the argument, lists the children of that group.
28533 When several thread group are passed, lists information about those
28534 thread groups. Without any parameters, lists information about all
28535 top-level thread groups.
28537 Normally, thread groups that are being debugged are reported.
28538 With the @samp{--available} option, @value{GDBN} reports thread groups
28539 available on the target.
28541 The output of this command may have either a @samp{threads} result or
28542 a @samp{groups} result. The @samp{thread} result has a list of tuples
28543 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28544 Information}). The @samp{groups} result has a list of tuples as value,
28545 each tuple describing a thread group. If top-level groups are
28546 requested (that is, no parameter is passed), or when several groups
28547 are passed, the output always has a @samp{groups} result. The format
28548 of the @samp{group} result is described below.
28550 To reduce the number of roundtrips it's possible to list thread groups
28551 together with their children, by passing the @samp{--recurse} option
28552 and the recursion depth. Presently, only recursion depth of 1 is
28553 permitted. If this option is present, then every reported thread group
28554 will also include its children, either as @samp{group} or
28555 @samp{threads} field.
28557 In general, any combination of option and parameters is permitted, with
28558 the following caveats:
28562 When a single thread group is passed, the output will typically
28563 be the @samp{threads} result. Because threads may not contain
28564 anything, the @samp{recurse} option will be ignored.
28567 When the @samp{--available} option is passed, limited information may
28568 be available. In particular, the list of threads of a process might
28569 be inaccessible. Further, specifying specific thread groups might
28570 not give any performance advantage over listing all thread groups.
28571 The frontend should assume that @samp{-list-thread-groups --available}
28572 is always an expensive operation and cache the results.
28576 The @samp{groups} result is a list of tuples, where each tuple may
28577 have the following fields:
28581 Identifier of the thread group. This field is always present.
28582 The identifier is an opaque string; frontends should not try to
28583 convert it to an integer, even though it might look like one.
28586 The type of the thread group. At present, only @samp{process} is a
28590 The target-specific process identifier. This field is only present
28591 for thread groups of type @samp{process} and only if the process exists.
28594 The number of children this thread group has. This field may be
28595 absent for an available thread group.
28598 This field has a list of tuples as value, each tuple describing a
28599 thread. It may be present if the @samp{--recurse} option is
28600 specified, and it's actually possible to obtain the threads.
28603 This field is a list of integers, each identifying a core that one
28604 thread of the group is running on. This field may be absent if
28605 such information is not available.
28608 The name of the executable file that corresponds to this thread group.
28609 The field is only present for thread groups of type @samp{process},
28610 and only if there is a corresponding executable file.
28614 @subheading Example
28618 -list-thread-groups
28619 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28620 -list-thread-groups 17
28621 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28622 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28623 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28624 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28625 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28626 -list-thread-groups --available
28627 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28628 -list-thread-groups --available --recurse 1
28629 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28630 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28631 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28632 -list-thread-groups --available --recurse 1 17 18
28633 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28634 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28635 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28639 @subheading The @code{-add-inferior} Command
28640 @findex -add-inferior
28642 @subheading Synopsis
28648 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28649 inferior is not associated with any executable. Such association may
28650 be established with the @samp{-file-exec-and-symbols} command
28651 (@pxref{GDB/MI File Commands}). The command response has a single
28652 field, @samp{thread-group}, whose value is the identifier of the
28653 thread group corresponding to the new inferior.
28655 @subheading Example
28660 ^done,thread-group="i3"
28663 @subheading The @code{-interpreter-exec} Command
28664 @findex -interpreter-exec
28666 @subheading Synopsis
28669 -interpreter-exec @var{interpreter} @var{command}
28671 @anchor{-interpreter-exec}
28673 Execute the specified @var{command} in the given @var{interpreter}.
28675 @subheading @value{GDBN} Command
28677 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28679 @subheading Example
28683 -interpreter-exec console "break main"
28684 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28685 &"During symbol reading, bad structure-type format.\n"
28686 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28691 @subheading The @code{-inferior-tty-set} Command
28692 @findex -inferior-tty-set
28694 @subheading Synopsis
28697 -inferior-tty-set /dev/pts/1
28700 Set terminal for future runs of the program being debugged.
28702 @subheading @value{GDBN} Command
28704 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28706 @subheading Example
28710 -inferior-tty-set /dev/pts/1
28715 @subheading The @code{-inferior-tty-show} Command
28716 @findex -inferior-tty-show
28718 @subheading Synopsis
28724 Show terminal for future runs of program being debugged.
28726 @subheading @value{GDBN} Command
28728 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28730 @subheading Example
28734 -inferior-tty-set /dev/pts/1
28738 ^done,inferior_tty_terminal="/dev/pts/1"
28742 @subheading The @code{-enable-timings} Command
28743 @findex -enable-timings
28745 @subheading Synopsis
28748 -enable-timings [yes | no]
28751 Toggle the printing of the wallclock, user and system times for an MI
28752 command as a field in its output. This command is to help frontend
28753 developers optimize the performance of their code. No argument is
28754 equivalent to @samp{yes}.
28756 @subheading @value{GDBN} Command
28760 @subheading Example
28768 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28769 addr="0x080484ed",func="main",file="myprog.c",
28770 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28771 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28779 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28780 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28781 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28782 fullname="/home/nickrob/myprog.c",line="73"@}
28787 @chapter @value{GDBN} Annotations
28789 This chapter describes annotations in @value{GDBN}. Annotations were
28790 designed to interface @value{GDBN} to graphical user interfaces or other
28791 similar programs which want to interact with @value{GDBN} at a
28792 relatively high level.
28794 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28798 This is Edition @value{EDITION}, @value{DATE}.
28802 * Annotations Overview:: What annotations are; the general syntax.
28803 * Server Prefix:: Issuing a command without affecting user state.
28804 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28805 * Errors:: Annotations for error messages.
28806 * Invalidation:: Some annotations describe things now invalid.
28807 * Annotations for Running::
28808 Whether the program is running, how it stopped, etc.
28809 * Source Annotations:: Annotations describing source code.
28812 @node Annotations Overview
28813 @section What is an Annotation?
28814 @cindex annotations
28816 Annotations start with a newline character, two @samp{control-z}
28817 characters, and the name of the annotation. If there is no additional
28818 information associated with this annotation, the name of the annotation
28819 is followed immediately by a newline. If there is additional
28820 information, the name of the annotation is followed by a space, the
28821 additional information, and a newline. The additional information
28822 cannot contain newline characters.
28824 Any output not beginning with a newline and two @samp{control-z}
28825 characters denotes literal output from @value{GDBN}. Currently there is
28826 no need for @value{GDBN} to output a newline followed by two
28827 @samp{control-z} characters, but if there was such a need, the
28828 annotations could be extended with an @samp{escape} annotation which
28829 means those three characters as output.
28831 The annotation @var{level}, which is specified using the
28832 @option{--annotate} command line option (@pxref{Mode Options}), controls
28833 how much information @value{GDBN} prints together with its prompt,
28834 values of expressions, source lines, and other types of output. Level 0
28835 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28836 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28837 for programs that control @value{GDBN}, and level 2 annotations have
28838 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28839 Interface, annotate, GDB's Obsolete Annotations}).
28842 @kindex set annotate
28843 @item set annotate @var{level}
28844 The @value{GDBN} command @code{set annotate} sets the level of
28845 annotations to the specified @var{level}.
28847 @item show annotate
28848 @kindex show annotate
28849 Show the current annotation level.
28852 This chapter describes level 3 annotations.
28854 A simple example of starting up @value{GDBN} with annotations is:
28857 $ @kbd{gdb --annotate=3}
28859 Copyright 2003 Free Software Foundation, Inc.
28860 GDB is free software, covered by the GNU General Public License,
28861 and you are welcome to change it and/or distribute copies of it
28862 under certain conditions.
28863 Type "show copying" to see the conditions.
28864 There is absolutely no warranty for GDB. Type "show warranty"
28866 This GDB was configured as "i386-pc-linux-gnu"
28877 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28878 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28879 denotes a @samp{control-z} character) are annotations; the rest is
28880 output from @value{GDBN}.
28882 @node Server Prefix
28883 @section The Server Prefix
28884 @cindex server prefix
28886 If you prefix a command with @samp{server } then it will not affect
28887 the command history, nor will it affect @value{GDBN}'s notion of which
28888 command to repeat if @key{RET} is pressed on a line by itself. This
28889 means that commands can be run behind a user's back by a front-end in
28890 a transparent manner.
28892 The @code{server } prefix does not affect the recording of values into
28893 the value history; to print a value without recording it into the
28894 value history, use the @code{output} command instead of the
28895 @code{print} command.
28897 Using this prefix also disables confirmation requests
28898 (@pxref{confirmation requests}).
28901 @section Annotation for @value{GDBN} Input
28903 @cindex annotations for prompts
28904 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28905 to know when to send output, when the output from a given command is
28908 Different kinds of input each have a different @dfn{input type}. Each
28909 input type has three annotations: a @code{pre-} annotation, which
28910 denotes the beginning of any prompt which is being output, a plain
28911 annotation, which denotes the end of the prompt, and then a @code{post-}
28912 annotation which denotes the end of any echo which may (or may not) be
28913 associated with the input. For example, the @code{prompt} input type
28914 features the following annotations:
28922 The input types are
28925 @findex pre-prompt annotation
28926 @findex prompt annotation
28927 @findex post-prompt annotation
28929 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28931 @findex pre-commands annotation
28932 @findex commands annotation
28933 @findex post-commands annotation
28935 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28936 command. The annotations are repeated for each command which is input.
28938 @findex pre-overload-choice annotation
28939 @findex overload-choice annotation
28940 @findex post-overload-choice annotation
28941 @item overload-choice
28942 When @value{GDBN} wants the user to select between various overloaded functions.
28944 @findex pre-query annotation
28945 @findex query annotation
28946 @findex post-query annotation
28948 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28950 @findex pre-prompt-for-continue annotation
28951 @findex prompt-for-continue annotation
28952 @findex post-prompt-for-continue annotation
28953 @item prompt-for-continue
28954 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28955 expect this to work well; instead use @code{set height 0} to disable
28956 prompting. This is because the counting of lines is buggy in the
28957 presence of annotations.
28962 @cindex annotations for errors, warnings and interrupts
28964 @findex quit annotation
28969 This annotation occurs right before @value{GDBN} responds to an interrupt.
28971 @findex error annotation
28976 This annotation occurs right before @value{GDBN} responds to an error.
28978 Quit and error annotations indicate that any annotations which @value{GDBN} was
28979 in the middle of may end abruptly. For example, if a
28980 @code{value-history-begin} annotation is followed by a @code{error}, one
28981 cannot expect to receive the matching @code{value-history-end}. One
28982 cannot expect not to receive it either, however; an error annotation
28983 does not necessarily mean that @value{GDBN} is immediately returning all the way
28986 @findex error-begin annotation
28987 A quit or error annotation may be preceded by
28993 Any output between that and the quit or error annotation is the error
28996 Warning messages are not yet annotated.
28997 @c If we want to change that, need to fix warning(), type_error(),
28998 @c range_error(), and possibly other places.
29001 @section Invalidation Notices
29003 @cindex annotations for invalidation messages
29004 The following annotations say that certain pieces of state may have
29008 @findex frames-invalid annotation
29009 @item ^Z^Zframes-invalid
29011 The frames (for example, output from the @code{backtrace} command) may
29014 @findex breakpoints-invalid annotation
29015 @item ^Z^Zbreakpoints-invalid
29017 The breakpoints may have changed. For example, the user just added or
29018 deleted a breakpoint.
29021 @node Annotations for Running
29022 @section Running the Program
29023 @cindex annotations for running programs
29025 @findex starting annotation
29026 @findex stopping annotation
29027 When the program starts executing due to a @value{GDBN} command such as
29028 @code{step} or @code{continue},
29034 is output. When the program stops,
29040 is output. Before the @code{stopped} annotation, a variety of
29041 annotations describe how the program stopped.
29044 @findex exited annotation
29045 @item ^Z^Zexited @var{exit-status}
29046 The program exited, and @var{exit-status} is the exit status (zero for
29047 successful exit, otherwise nonzero).
29049 @findex signalled annotation
29050 @findex signal-name annotation
29051 @findex signal-name-end annotation
29052 @findex signal-string annotation
29053 @findex signal-string-end annotation
29054 @item ^Z^Zsignalled
29055 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29056 annotation continues:
29062 ^Z^Zsignal-name-end
29066 ^Z^Zsignal-string-end
29071 where @var{name} is the name of the signal, such as @code{SIGILL} or
29072 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29073 as @code{Illegal Instruction} or @code{Segmentation fault}.
29074 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29075 user's benefit and have no particular format.
29077 @findex signal annotation
29079 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29080 just saying that the program received the signal, not that it was
29081 terminated with it.
29083 @findex breakpoint annotation
29084 @item ^Z^Zbreakpoint @var{number}
29085 The program hit breakpoint number @var{number}.
29087 @findex watchpoint annotation
29088 @item ^Z^Zwatchpoint @var{number}
29089 The program hit watchpoint number @var{number}.
29092 @node Source Annotations
29093 @section Displaying Source
29094 @cindex annotations for source display
29096 @findex source annotation
29097 The following annotation is used instead of displaying source code:
29100 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29103 where @var{filename} is an absolute file name indicating which source
29104 file, @var{line} is the line number within that file (where 1 is the
29105 first line in the file), @var{character} is the character position
29106 within the file (where 0 is the first character in the file) (for most
29107 debug formats this will necessarily point to the beginning of a line),
29108 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29109 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29110 @var{addr} is the address in the target program associated with the
29111 source which is being displayed. @var{addr} is in the form @samp{0x}
29112 followed by one or more lowercase hex digits (note that this does not
29113 depend on the language).
29115 @node JIT Interface
29116 @chapter JIT Compilation Interface
29117 @cindex just-in-time compilation
29118 @cindex JIT compilation interface
29120 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29121 interface. A JIT compiler is a program or library that generates native
29122 executable code at runtime and executes it, usually in order to achieve good
29123 performance while maintaining platform independence.
29125 Programs that use JIT compilation are normally difficult to debug because
29126 portions of their code are generated at runtime, instead of being loaded from
29127 object files, which is where @value{GDBN} normally finds the program's symbols
29128 and debug information. In order to debug programs that use JIT compilation,
29129 @value{GDBN} has an interface that allows the program to register in-memory
29130 symbol files with @value{GDBN} at runtime.
29132 If you are using @value{GDBN} to debug a program that uses this interface, then
29133 it should work transparently so long as you have not stripped the binary. If
29134 you are developing a JIT compiler, then the interface is documented in the rest
29135 of this chapter. At this time, the only known client of this interface is the
29138 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29139 JIT compiler communicates with @value{GDBN} by writing data into a global
29140 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29141 attaches, it reads a linked list of symbol files from the global variable to
29142 find existing code, and puts a breakpoint in the function so that it can find
29143 out about additional code.
29146 * Declarations:: Relevant C struct declarations
29147 * Registering Code:: Steps to register code
29148 * Unregistering Code:: Steps to unregister code
29152 @section JIT Declarations
29154 These are the relevant struct declarations that a C program should include to
29155 implement the interface:
29165 struct jit_code_entry
29167 struct jit_code_entry *next_entry;
29168 struct jit_code_entry *prev_entry;
29169 const char *symfile_addr;
29170 uint64_t symfile_size;
29173 struct jit_descriptor
29176 /* This type should be jit_actions_t, but we use uint32_t
29177 to be explicit about the bitwidth. */
29178 uint32_t action_flag;
29179 struct jit_code_entry *relevant_entry;
29180 struct jit_code_entry *first_entry;
29183 /* GDB puts a breakpoint in this function. */
29184 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29186 /* Make sure to specify the version statically, because the
29187 debugger may check the version before we can set it. */
29188 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29191 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29192 modifications to this global data properly, which can easily be done by putting
29193 a global mutex around modifications to these structures.
29195 @node Registering Code
29196 @section Registering Code
29198 To register code with @value{GDBN}, the JIT should follow this protocol:
29202 Generate an object file in memory with symbols and other desired debug
29203 information. The file must include the virtual addresses of the sections.
29206 Create a code entry for the file, which gives the start and size of the symbol
29210 Add it to the linked list in the JIT descriptor.
29213 Point the relevant_entry field of the descriptor at the entry.
29216 Set @code{action_flag} to @code{JIT_REGISTER} and call
29217 @code{__jit_debug_register_code}.
29220 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29221 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29222 new code. However, the linked list must still be maintained in order to allow
29223 @value{GDBN} to attach to a running process and still find the symbol files.
29225 @node Unregistering Code
29226 @section Unregistering Code
29228 If code is freed, then the JIT should use the following protocol:
29232 Remove the code entry corresponding to the code from the linked list.
29235 Point the @code{relevant_entry} field of the descriptor at the code entry.
29238 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29239 @code{__jit_debug_register_code}.
29242 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29243 and the JIT will leak the memory used for the associated symbol files.
29246 @chapter Reporting Bugs in @value{GDBN}
29247 @cindex bugs in @value{GDBN}
29248 @cindex reporting bugs in @value{GDBN}
29250 Your bug reports play an essential role in making @value{GDBN} reliable.
29252 Reporting a bug may help you by bringing a solution to your problem, or it
29253 may not. But in any case the principal function of a bug report is to help
29254 the entire community by making the next version of @value{GDBN} work better. Bug
29255 reports are your contribution to the maintenance of @value{GDBN}.
29257 In order for a bug report to serve its purpose, you must include the
29258 information that enables us to fix the bug.
29261 * Bug Criteria:: Have you found a bug?
29262 * Bug Reporting:: How to report bugs
29266 @section Have You Found a Bug?
29267 @cindex bug criteria
29269 If you are not sure whether you have found a bug, here are some guidelines:
29272 @cindex fatal signal
29273 @cindex debugger crash
29274 @cindex crash of debugger
29276 If the debugger gets a fatal signal, for any input whatever, that is a
29277 @value{GDBN} bug. Reliable debuggers never crash.
29279 @cindex error on valid input
29281 If @value{GDBN} produces an error message for valid input, that is a
29282 bug. (Note that if you're cross debugging, the problem may also be
29283 somewhere in the connection to the target.)
29285 @cindex invalid input
29287 If @value{GDBN} does not produce an error message for invalid input,
29288 that is a bug. However, you should note that your idea of
29289 ``invalid input'' might be our idea of ``an extension'' or ``support
29290 for traditional practice''.
29293 If you are an experienced user of debugging tools, your suggestions
29294 for improvement of @value{GDBN} are welcome in any case.
29297 @node Bug Reporting
29298 @section How to Report Bugs
29299 @cindex bug reports
29300 @cindex @value{GDBN} bugs, reporting
29302 A number of companies and individuals offer support for @sc{gnu} products.
29303 If you obtained @value{GDBN} from a support organization, we recommend you
29304 contact that organization first.
29306 You can find contact information for many support companies and
29307 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29309 @c should add a web page ref...
29312 @ifset BUGURL_DEFAULT
29313 In any event, we also recommend that you submit bug reports for
29314 @value{GDBN}. The preferred method is to submit them directly using
29315 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29316 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29319 @strong{Do not send bug reports to @samp{info-gdb}, or to
29320 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29321 not want to receive bug reports. Those that do have arranged to receive
29324 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29325 serves as a repeater. The mailing list and the newsgroup carry exactly
29326 the same messages. Often people think of posting bug reports to the
29327 newsgroup instead of mailing them. This appears to work, but it has one
29328 problem which can be crucial: a newsgroup posting often lacks a mail
29329 path back to the sender. Thus, if we need to ask for more information,
29330 we may be unable to reach you. For this reason, it is better to send
29331 bug reports to the mailing list.
29333 @ifclear BUGURL_DEFAULT
29334 In any event, we also recommend that you submit bug reports for
29335 @value{GDBN} to @value{BUGURL}.
29339 The fundamental principle of reporting bugs usefully is this:
29340 @strong{report all the facts}. If you are not sure whether to state a
29341 fact or leave it out, state it!
29343 Often people omit facts because they think they know what causes the
29344 problem and assume that some details do not matter. Thus, you might
29345 assume that the name of the variable you use in an example does not matter.
29346 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29347 stray memory reference which happens to fetch from the location where that
29348 name is stored in memory; perhaps, if the name were different, the contents
29349 of that location would fool the debugger into doing the right thing despite
29350 the bug. Play it safe and give a specific, complete example. That is the
29351 easiest thing for you to do, and the most helpful.
29353 Keep in mind that the purpose of a bug report is to enable us to fix the
29354 bug. It may be that the bug has been reported previously, but neither
29355 you nor we can know that unless your bug report is complete and
29358 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29359 bell?'' Those bug reports are useless, and we urge everyone to
29360 @emph{refuse to respond to them} except to chide the sender to report
29363 To enable us to fix the bug, you should include all these things:
29367 The version of @value{GDBN}. @value{GDBN} announces it if you start
29368 with no arguments; you can also print it at any time using @code{show
29371 Without this, we will not know whether there is any point in looking for
29372 the bug in the current version of @value{GDBN}.
29375 The type of machine you are using, and the operating system name and
29379 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29380 ``@value{GCC}--2.8.1''.
29383 What compiler (and its version) was used to compile the program you are
29384 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29385 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29386 to get this information; for other compilers, see the documentation for
29390 The command arguments you gave the compiler to compile your example and
29391 observe the bug. For example, did you use @samp{-O}? To guarantee
29392 you will not omit something important, list them all. A copy of the
29393 Makefile (or the output from make) is sufficient.
29395 If we were to try to guess the arguments, we would probably guess wrong
29396 and then we might not encounter the bug.
29399 A complete input script, and all necessary source files, that will
29403 A description of what behavior you observe that you believe is
29404 incorrect. For example, ``It gets a fatal signal.''
29406 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29407 will certainly notice it. But if the bug is incorrect output, we might
29408 not notice unless it is glaringly wrong. You might as well not give us
29409 a chance to make a mistake.
29411 Even if the problem you experience is a fatal signal, you should still
29412 say so explicitly. Suppose something strange is going on, such as, your
29413 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29414 the C library on your system. (This has happened!) Your copy might
29415 crash and ours would not. If you told us to expect a crash, then when
29416 ours fails to crash, we would know that the bug was not happening for
29417 us. If you had not told us to expect a crash, then we would not be able
29418 to draw any conclusion from our observations.
29421 @cindex recording a session script
29422 To collect all this information, you can use a session recording program
29423 such as @command{script}, which is available on many Unix systems.
29424 Just run your @value{GDBN} session inside @command{script} and then
29425 include the @file{typescript} file with your bug report.
29427 Another way to record a @value{GDBN} session is to run @value{GDBN}
29428 inside Emacs and then save the entire buffer to a file.
29431 If you wish to suggest changes to the @value{GDBN} source, send us context
29432 diffs. If you even discuss something in the @value{GDBN} source, refer to
29433 it by context, not by line number.
29435 The line numbers in our development sources will not match those in your
29436 sources. Your line numbers would convey no useful information to us.
29440 Here are some things that are not necessary:
29444 A description of the envelope of the bug.
29446 Often people who encounter a bug spend a lot of time investigating
29447 which changes to the input file will make the bug go away and which
29448 changes will not affect it.
29450 This is often time consuming and not very useful, because the way we
29451 will find the bug is by running a single example under the debugger
29452 with breakpoints, not by pure deduction from a series of examples.
29453 We recommend that you save your time for something else.
29455 Of course, if you can find a simpler example to report @emph{instead}
29456 of the original one, that is a convenience for us. Errors in the
29457 output will be easier to spot, running under the debugger will take
29458 less time, and so on.
29460 However, simplification is not vital; if you do not want to do this,
29461 report the bug anyway and send us the entire test case you used.
29464 A patch for the bug.
29466 A patch for the bug does help us if it is a good one. But do not omit
29467 the necessary information, such as the test case, on the assumption that
29468 a patch is all we need. We might see problems with your patch and decide
29469 to fix the problem another way, or we might not understand it at all.
29471 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29472 construct an example that will make the program follow a certain path
29473 through the code. If you do not send us the example, we will not be able
29474 to construct one, so we will not be able to verify that the bug is fixed.
29476 And if we cannot understand what bug you are trying to fix, or why your
29477 patch should be an improvement, we will not install it. A test case will
29478 help us to understand.
29481 A guess about what the bug is or what it depends on.
29483 Such guesses are usually wrong. Even we cannot guess right about such
29484 things without first using the debugger to find the facts.
29487 @c The readline documentation is distributed with the readline code
29488 @c and consists of the two following files:
29490 @c inc-hist.texinfo
29491 @c Use -I with makeinfo to point to the appropriate directory,
29492 @c environment var TEXINPUTS with TeX.
29493 @include rluser.texi
29494 @include inc-hist.texinfo
29497 @node Formatting Documentation
29498 @appendix Formatting Documentation
29500 @cindex @value{GDBN} reference card
29501 @cindex reference card
29502 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29503 for printing with PostScript or Ghostscript, in the @file{gdb}
29504 subdirectory of the main source directory@footnote{In
29505 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29506 release.}. If you can use PostScript or Ghostscript with your printer,
29507 you can print the reference card immediately with @file{refcard.ps}.
29509 The release also includes the source for the reference card. You
29510 can format it, using @TeX{}, by typing:
29516 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29517 mode on US ``letter'' size paper;
29518 that is, on a sheet 11 inches wide by 8.5 inches
29519 high. You will need to specify this form of printing as an option to
29520 your @sc{dvi} output program.
29522 @cindex documentation
29524 All the documentation for @value{GDBN} comes as part of the machine-readable
29525 distribution. The documentation is written in Texinfo format, which is
29526 a documentation system that uses a single source file to produce both
29527 on-line information and a printed manual. You can use one of the Info
29528 formatting commands to create the on-line version of the documentation
29529 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29531 @value{GDBN} includes an already formatted copy of the on-line Info
29532 version of this manual in the @file{gdb} subdirectory. The main Info
29533 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29534 subordinate files matching @samp{gdb.info*} in the same directory. If
29535 necessary, you can print out these files, or read them with any editor;
29536 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29537 Emacs or the standalone @code{info} program, available as part of the
29538 @sc{gnu} Texinfo distribution.
29540 If you want to format these Info files yourself, you need one of the
29541 Info formatting programs, such as @code{texinfo-format-buffer} or
29544 If you have @code{makeinfo} installed, and are in the top level
29545 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29546 version @value{GDBVN}), you can make the Info file by typing:
29553 If you want to typeset and print copies of this manual, you need @TeX{},
29554 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29555 Texinfo definitions file.
29557 @TeX{} is a typesetting program; it does not print files directly, but
29558 produces output files called @sc{dvi} files. To print a typeset
29559 document, you need a program to print @sc{dvi} files. If your system
29560 has @TeX{} installed, chances are it has such a program. The precise
29561 command to use depends on your system; @kbd{lpr -d} is common; another
29562 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29563 require a file name without any extension or a @samp{.dvi} extension.
29565 @TeX{} also requires a macro definitions file called
29566 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29567 written in Texinfo format. On its own, @TeX{} cannot either read or
29568 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29569 and is located in the @file{gdb-@var{version-number}/texinfo}
29572 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29573 typeset and print this manual. First switch to the @file{gdb}
29574 subdirectory of the main source directory (for example, to
29575 @file{gdb-@value{GDBVN}/gdb}) and type:
29581 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29583 @node Installing GDB
29584 @appendix Installing @value{GDBN}
29585 @cindex installation
29588 * Requirements:: Requirements for building @value{GDBN}
29589 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29590 * Separate Objdir:: Compiling @value{GDBN} in another directory
29591 * Config Names:: Specifying names for hosts and targets
29592 * Configure Options:: Summary of options for configure
29593 * System-wide configuration:: Having a system-wide init file
29597 @section Requirements for Building @value{GDBN}
29598 @cindex building @value{GDBN}, requirements for
29600 Building @value{GDBN} requires various tools and packages to be available.
29601 Other packages will be used only if they are found.
29603 @heading Tools/Packages Necessary for Building @value{GDBN}
29605 @item ISO C90 compiler
29606 @value{GDBN} is written in ISO C90. It should be buildable with any
29607 working C90 compiler, e.g.@: GCC.
29611 @heading Tools/Packages Optional for Building @value{GDBN}
29615 @value{GDBN} can use the Expat XML parsing library. This library may be
29616 included with your operating system distribution; if it is not, you
29617 can get the latest version from @url{http://expat.sourceforge.net}.
29618 The @file{configure} script will search for this library in several
29619 standard locations; if it is installed in an unusual path, you can
29620 use the @option{--with-libexpat-prefix} option to specify its location.
29626 Remote protocol memory maps (@pxref{Memory Map Format})
29628 Target descriptions (@pxref{Target Descriptions})
29630 Remote shared library lists (@pxref{Library List Format})
29632 MS-Windows shared libraries (@pxref{Shared Libraries})
29636 @cindex compressed debug sections
29637 @value{GDBN} will use the @samp{zlib} library, if available, to read
29638 compressed debug sections. Some linkers, such as GNU gold, are capable
29639 of producing binaries with compressed debug sections. If @value{GDBN}
29640 is compiled with @samp{zlib}, it will be able to read the debug
29641 information in such binaries.
29643 The @samp{zlib} library is likely included with your operating system
29644 distribution; if it is not, you can get the latest version from
29645 @url{http://zlib.net}.
29648 @value{GDBN}'s features related to character sets (@pxref{Character
29649 Sets}) require a functioning @code{iconv} implementation. If you are
29650 on a GNU system, then this is provided by the GNU C Library. Some
29651 other systems also provide a working @code{iconv}.
29653 On systems with @code{iconv}, you can install GNU Libiconv. If you
29654 have previously installed Libiconv, you can use the
29655 @option{--with-libiconv-prefix} option to configure.
29657 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29658 arrange to build Libiconv if a directory named @file{libiconv} appears
29659 in the top-most source directory. If Libiconv is built this way, and
29660 if the operating system does not provide a suitable @code{iconv}
29661 implementation, then the just-built library will automatically be used
29662 by @value{GDBN}. One easy way to set this up is to download GNU
29663 Libiconv, unpack it, and then rename the directory holding the
29664 Libiconv source code to @samp{libiconv}.
29667 @node Running Configure
29668 @section Invoking the @value{GDBN} @file{configure} Script
29669 @cindex configuring @value{GDBN}
29670 @value{GDBN} comes with a @file{configure} script that automates the process
29671 of preparing @value{GDBN} for installation; you can then use @code{make} to
29672 build the @code{gdb} program.
29674 @c irrelevant in info file; it's as current as the code it lives with.
29675 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29676 look at the @file{README} file in the sources; we may have improved the
29677 installation procedures since publishing this manual.}
29680 The @value{GDBN} distribution includes all the source code you need for
29681 @value{GDBN} in a single directory, whose name is usually composed by
29682 appending the version number to @samp{gdb}.
29684 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29685 @file{gdb-@value{GDBVN}} directory. That directory contains:
29688 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29689 script for configuring @value{GDBN} and all its supporting libraries
29691 @item gdb-@value{GDBVN}/gdb
29692 the source specific to @value{GDBN} itself
29694 @item gdb-@value{GDBVN}/bfd
29695 source for the Binary File Descriptor library
29697 @item gdb-@value{GDBVN}/include
29698 @sc{gnu} include files
29700 @item gdb-@value{GDBVN}/libiberty
29701 source for the @samp{-liberty} free software library
29703 @item gdb-@value{GDBVN}/opcodes
29704 source for the library of opcode tables and disassemblers
29706 @item gdb-@value{GDBVN}/readline
29707 source for the @sc{gnu} command-line interface
29709 @item gdb-@value{GDBVN}/glob
29710 source for the @sc{gnu} filename pattern-matching subroutine
29712 @item gdb-@value{GDBVN}/mmalloc
29713 source for the @sc{gnu} memory-mapped malloc package
29716 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29717 from the @file{gdb-@var{version-number}} source directory, which in
29718 this example is the @file{gdb-@value{GDBVN}} directory.
29720 First switch to the @file{gdb-@var{version-number}} source directory
29721 if you are not already in it; then run @file{configure}. Pass the
29722 identifier for the platform on which @value{GDBN} will run as an
29728 cd gdb-@value{GDBVN}
29729 ./configure @var{host}
29734 where @var{host} is an identifier such as @samp{sun4} or
29735 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29736 (You can often leave off @var{host}; @file{configure} tries to guess the
29737 correct value by examining your system.)
29739 Running @samp{configure @var{host}} and then running @code{make} builds the
29740 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29741 libraries, then @code{gdb} itself. The configured source files, and the
29742 binaries, are left in the corresponding source directories.
29745 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29746 system does not recognize this automatically when you run a different
29747 shell, you may need to run @code{sh} on it explicitly:
29750 sh configure @var{host}
29753 If you run @file{configure} from a directory that contains source
29754 directories for multiple libraries or programs, such as the
29755 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29757 creates configuration files for every directory level underneath (unless
29758 you tell it not to, with the @samp{--norecursion} option).
29760 You should run the @file{configure} script from the top directory in the
29761 source tree, the @file{gdb-@var{version-number}} directory. If you run
29762 @file{configure} from one of the subdirectories, you will configure only
29763 that subdirectory. That is usually not what you want. In particular,
29764 if you run the first @file{configure} from the @file{gdb} subdirectory
29765 of the @file{gdb-@var{version-number}} directory, you will omit the
29766 configuration of @file{bfd}, @file{readline}, and other sibling
29767 directories of the @file{gdb} subdirectory. This leads to build errors
29768 about missing include files such as @file{bfd/bfd.h}.
29770 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29771 However, you should make sure that the shell on your path (named by
29772 the @samp{SHELL} environment variable) is publicly readable. Remember
29773 that @value{GDBN} uses the shell to start your program---some systems refuse to
29774 let @value{GDBN} debug child processes whose programs are not readable.
29776 @node Separate Objdir
29777 @section Compiling @value{GDBN} in Another Directory
29779 If you want to run @value{GDBN} versions for several host or target machines,
29780 you need a different @code{gdb} compiled for each combination of
29781 host and target. @file{configure} is designed to make this easy by
29782 allowing you to generate each configuration in a separate subdirectory,
29783 rather than in the source directory. If your @code{make} program
29784 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29785 @code{make} in each of these directories builds the @code{gdb}
29786 program specified there.
29788 To build @code{gdb} in a separate directory, run @file{configure}
29789 with the @samp{--srcdir} option to specify where to find the source.
29790 (You also need to specify a path to find @file{configure}
29791 itself from your working directory. If the path to @file{configure}
29792 would be the same as the argument to @samp{--srcdir}, you can leave out
29793 the @samp{--srcdir} option; it is assumed.)
29795 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29796 separate directory for a Sun 4 like this:
29800 cd gdb-@value{GDBVN}
29803 ../gdb-@value{GDBVN}/configure sun4
29808 When @file{configure} builds a configuration using a remote source
29809 directory, it creates a tree for the binaries with the same structure
29810 (and using the same names) as the tree under the source directory. In
29811 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29812 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29813 @file{gdb-sun4/gdb}.
29815 Make sure that your path to the @file{configure} script has just one
29816 instance of @file{gdb} in it. If your path to @file{configure} looks
29817 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29818 one subdirectory of @value{GDBN}, not the whole package. This leads to
29819 build errors about missing include files such as @file{bfd/bfd.h}.
29821 One popular reason to build several @value{GDBN} configurations in separate
29822 directories is to configure @value{GDBN} for cross-compiling (where
29823 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
29824 programs that run on another machine---the @dfn{target}).
29825 You specify a cross-debugging target by
29826 giving the @samp{--target=@var{target}} option to @file{configure}.
29828 When you run @code{make} to build a program or library, you must run
29829 it in a configured directory---whatever directory you were in when you
29830 called @file{configure} (or one of its subdirectories).
29832 The @code{Makefile} that @file{configure} generates in each source
29833 directory also runs recursively. If you type @code{make} in a source
29834 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29835 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29836 will build all the required libraries, and then build GDB.
29838 When you have multiple hosts or targets configured in separate
29839 directories, you can run @code{make} on them in parallel (for example,
29840 if they are NFS-mounted on each of the hosts); they will not interfere
29844 @section Specifying Names for Hosts and Targets
29846 The specifications used for hosts and targets in the @file{configure}
29847 script are based on a three-part naming scheme, but some short predefined
29848 aliases are also supported. The full naming scheme encodes three pieces
29849 of information in the following pattern:
29852 @var{architecture}-@var{vendor}-@var{os}
29855 For example, you can use the alias @code{sun4} as a @var{host} argument,
29856 or as the value for @var{target} in a @code{--target=@var{target}}
29857 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29859 The @file{configure} script accompanying @value{GDBN} does not provide
29860 any query facility to list all supported host and target names or
29861 aliases. @file{configure} calls the Bourne shell script
29862 @code{config.sub} to map abbreviations to full names; you can read the
29863 script, if you wish, or you can use it to test your guesses on
29864 abbreviations---for example:
29867 % sh config.sub i386-linux
29869 % sh config.sub alpha-linux
29870 alpha-unknown-linux-gnu
29871 % sh config.sub hp9k700
29873 % sh config.sub sun4
29874 sparc-sun-sunos4.1.1
29875 % sh config.sub sun3
29876 m68k-sun-sunos4.1.1
29877 % sh config.sub i986v
29878 Invalid configuration `i986v': machine `i986v' not recognized
29882 @code{config.sub} is also distributed in the @value{GDBN} source
29883 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29885 @node Configure Options
29886 @section @file{configure} Options
29888 Here is a summary of the @file{configure} options and arguments that
29889 are most often useful for building @value{GDBN}. @file{configure} also has
29890 several other options not listed here. @inforef{What Configure
29891 Does,,configure.info}, for a full explanation of @file{configure}.
29894 configure @r{[}--help@r{]}
29895 @r{[}--prefix=@var{dir}@r{]}
29896 @r{[}--exec-prefix=@var{dir}@r{]}
29897 @r{[}--srcdir=@var{dirname}@r{]}
29898 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29899 @r{[}--target=@var{target}@r{]}
29904 You may introduce options with a single @samp{-} rather than
29905 @samp{--} if you prefer; but you may abbreviate option names if you use
29910 Display a quick summary of how to invoke @file{configure}.
29912 @item --prefix=@var{dir}
29913 Configure the source to install programs and files under directory
29916 @item --exec-prefix=@var{dir}
29917 Configure the source to install programs under directory
29920 @c avoid splitting the warning from the explanation:
29922 @item --srcdir=@var{dirname}
29923 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29924 @code{make} that implements the @code{VPATH} feature.}@*
29925 Use this option to make configurations in directories separate from the
29926 @value{GDBN} source directories. Among other things, you can use this to
29927 build (or maintain) several configurations simultaneously, in separate
29928 directories. @file{configure} writes configuration-specific files in
29929 the current directory, but arranges for them to use the source in the
29930 directory @var{dirname}. @file{configure} creates directories under
29931 the working directory in parallel to the source directories below
29934 @item --norecursion
29935 Configure only the directory level where @file{configure} is executed; do not
29936 propagate configuration to subdirectories.
29938 @item --target=@var{target}
29939 Configure @value{GDBN} for cross-debugging programs running on the specified
29940 @var{target}. Without this option, @value{GDBN} is configured to debug
29941 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29943 There is no convenient way to generate a list of all available targets.
29945 @item @var{host} @dots{}
29946 Configure @value{GDBN} to run on the specified @var{host}.
29948 There is no convenient way to generate a list of all available hosts.
29951 There are many other options available as well, but they are generally
29952 needed for special purposes only.
29954 @node System-wide configuration
29955 @section System-wide configuration and settings
29956 @cindex system-wide init file
29958 @value{GDBN} can be configured to have a system-wide init file;
29959 this file will be read and executed at startup (@pxref{Startup, , What
29960 @value{GDBN} does during startup}).
29962 Here is the corresponding configure option:
29965 @item --with-system-gdbinit=@var{file}
29966 Specify that the default location of the system-wide init file is
29970 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29971 it may be subject to relocation. Two possible cases:
29975 If the default location of this init file contains @file{$prefix},
29976 it will be subject to relocation. Suppose that the configure options
29977 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29978 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29979 init file is looked for as @file{$install/etc/gdbinit} instead of
29980 @file{$prefix/etc/gdbinit}.
29983 By contrast, if the default location does not contain the prefix,
29984 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29985 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29986 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29987 wherever @value{GDBN} is installed.
29990 @node Maintenance Commands
29991 @appendix Maintenance Commands
29992 @cindex maintenance commands
29993 @cindex internal commands
29995 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29996 includes a number of commands intended for @value{GDBN} developers,
29997 that are not documented elsewhere in this manual. These commands are
29998 provided here for reference. (For commands that turn on debugging
29999 messages, see @ref{Debugging Output}.)
30002 @kindex maint agent
30003 @kindex maint agent-eval
30004 @item maint agent @var{expression}
30005 @itemx maint agent-eval @var{expression}
30006 Translate the given @var{expression} into remote agent bytecodes.
30007 This command is useful for debugging the Agent Expression mechanism
30008 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30009 expression useful for data collection, such as by tracepoints, while
30010 @samp{maint agent-eval} produces an expression that evaluates directly
30011 to a result. For instance, a collection expression for @code{globa +
30012 globb} will include bytecodes to record four bytes of memory at each
30013 of the addresses of @code{globa} and @code{globb}, while discarding
30014 the result of the addition, while an evaluation expression will do the
30015 addition and return the sum.
30017 @kindex maint info breakpoints
30018 @item @anchor{maint info breakpoints}maint info breakpoints
30019 Using the same format as @samp{info breakpoints}, display both the
30020 breakpoints you've set explicitly, and those @value{GDBN} is using for
30021 internal purposes. Internal breakpoints are shown with negative
30022 breakpoint numbers. The type column identifies what kind of breakpoint
30027 Normal, explicitly set breakpoint.
30030 Normal, explicitly set watchpoint.
30033 Internal breakpoint, used to handle correctly stepping through
30034 @code{longjmp} calls.
30036 @item longjmp resume
30037 Internal breakpoint at the target of a @code{longjmp}.
30040 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30043 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30046 Shared library events.
30050 @kindex set displaced-stepping
30051 @kindex show displaced-stepping
30052 @cindex displaced stepping support
30053 @cindex out-of-line single-stepping
30054 @item set displaced-stepping
30055 @itemx show displaced-stepping
30056 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30057 if the target supports it. Displaced stepping is a way to single-step
30058 over breakpoints without removing them from the inferior, by executing
30059 an out-of-line copy of the instruction that was originally at the
30060 breakpoint location. It is also known as out-of-line single-stepping.
30063 @item set displaced-stepping on
30064 If the target architecture supports it, @value{GDBN} will use
30065 displaced stepping to step over breakpoints.
30067 @item set displaced-stepping off
30068 @value{GDBN} will not use displaced stepping to step over breakpoints,
30069 even if such is supported by the target architecture.
30071 @cindex non-stop mode, and @samp{set displaced-stepping}
30072 @item set displaced-stepping auto
30073 This is the default mode. @value{GDBN} will use displaced stepping
30074 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30075 architecture supports displaced stepping.
30078 @kindex maint check-symtabs
30079 @item maint check-symtabs
30080 Check the consistency of psymtabs and symtabs.
30082 @kindex maint cplus first_component
30083 @item maint cplus first_component @var{name}
30084 Print the first C@t{++} class/namespace component of @var{name}.
30086 @kindex maint cplus namespace
30087 @item maint cplus namespace
30088 Print the list of possible C@t{++} namespaces.
30090 @kindex maint demangle
30091 @item maint demangle @var{name}
30092 Demangle a C@t{++} or Objective-C mangled @var{name}.
30094 @kindex maint deprecate
30095 @kindex maint undeprecate
30096 @cindex deprecated commands
30097 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30098 @itemx maint undeprecate @var{command}
30099 Deprecate or undeprecate the named @var{command}. Deprecated commands
30100 cause @value{GDBN} to issue a warning when you use them. The optional
30101 argument @var{replacement} says which newer command should be used in
30102 favor of the deprecated one; if it is given, @value{GDBN} will mention
30103 the replacement as part of the warning.
30105 @kindex maint dump-me
30106 @item maint dump-me
30107 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30108 Cause a fatal signal in the debugger and force it to dump its core.
30109 This is supported only on systems which support aborting a program
30110 with the @code{SIGQUIT} signal.
30112 @kindex maint internal-error
30113 @kindex maint internal-warning
30114 @item maint internal-error @r{[}@var{message-text}@r{]}
30115 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30116 Cause @value{GDBN} to call the internal function @code{internal_error}
30117 or @code{internal_warning} and hence behave as though an internal error
30118 or internal warning has been detected. In addition to reporting the
30119 internal problem, these functions give the user the opportunity to
30120 either quit @value{GDBN} or create a core file of the current
30121 @value{GDBN} session.
30123 These commands take an optional parameter @var{message-text} that is
30124 used as the text of the error or warning message.
30126 Here's an example of using @code{internal-error}:
30129 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30130 @dots{}/maint.c:121: internal-error: testing, 1, 2
30131 A problem internal to GDB has been detected. Further
30132 debugging may prove unreliable.
30133 Quit this debugging session? (y or n) @kbd{n}
30134 Create a core file? (y or n) @kbd{n}
30138 @cindex @value{GDBN} internal error
30139 @cindex internal errors, control of @value{GDBN} behavior
30141 @kindex maint set internal-error
30142 @kindex maint show internal-error
30143 @kindex maint set internal-warning
30144 @kindex maint show internal-warning
30145 @item maint set internal-error @var{action} [ask|yes|no]
30146 @itemx maint show internal-error @var{action}
30147 @itemx maint set internal-warning @var{action} [ask|yes|no]
30148 @itemx maint show internal-warning @var{action}
30149 When @value{GDBN} reports an internal problem (error or warning) it
30150 gives the user the opportunity to both quit @value{GDBN} and create a
30151 core file of the current @value{GDBN} session. These commands let you
30152 override the default behaviour for each particular @var{action},
30153 described in the table below.
30157 You can specify that @value{GDBN} should always (yes) or never (no)
30158 quit. The default is to ask the user what to do.
30161 You can specify that @value{GDBN} should always (yes) or never (no)
30162 create a core file. The default is to ask the user what to do.
30165 @kindex maint packet
30166 @item maint packet @var{text}
30167 If @value{GDBN} is talking to an inferior via the serial protocol,
30168 then this command sends the string @var{text} to the inferior, and
30169 displays the response packet. @value{GDBN} supplies the initial
30170 @samp{$} character, the terminating @samp{#} character, and the
30173 @kindex maint print architecture
30174 @item maint print architecture @r{[}@var{file}@r{]}
30175 Print the entire architecture configuration. The optional argument
30176 @var{file} names the file where the output goes.
30178 @kindex maint print c-tdesc
30179 @item maint print c-tdesc
30180 Print the current target description (@pxref{Target Descriptions}) as
30181 a C source file. The created source file can be used in @value{GDBN}
30182 when an XML parser is not available to parse the description.
30184 @kindex maint print dummy-frames
30185 @item maint print dummy-frames
30186 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30189 (@value{GDBP}) @kbd{b add}
30191 (@value{GDBP}) @kbd{print add(2,3)}
30192 Breakpoint 2, add (a=2, b=3) at @dots{}
30194 The program being debugged stopped while in a function called from GDB.
30196 (@value{GDBP}) @kbd{maint print dummy-frames}
30197 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30198 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30199 call_lo=0x01014000 call_hi=0x01014001
30203 Takes an optional file parameter.
30205 @kindex maint print registers
30206 @kindex maint print raw-registers
30207 @kindex maint print cooked-registers
30208 @kindex maint print register-groups
30209 @item maint print registers @r{[}@var{file}@r{]}
30210 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30211 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30212 @itemx maint print register-groups @r{[}@var{file}@r{]}
30213 Print @value{GDBN}'s internal register data structures.
30215 The command @code{maint print raw-registers} includes the contents of
30216 the raw register cache; the command @code{maint print cooked-registers}
30217 includes the (cooked) value of all registers, including registers which
30218 aren't available on the target nor visible to user; and the
30219 command @code{maint print register-groups} includes the groups that each
30220 register is a member of. @xref{Registers,, Registers, gdbint,
30221 @value{GDBN} Internals}.
30223 These commands take an optional parameter, a file name to which to
30224 write the information.
30226 @kindex maint print reggroups
30227 @item maint print reggroups @r{[}@var{file}@r{]}
30228 Print @value{GDBN}'s internal register group data structures. The
30229 optional argument @var{file} tells to what file to write the
30232 The register groups info looks like this:
30235 (@value{GDBP}) @kbd{maint print reggroups}
30248 This command forces @value{GDBN} to flush its internal register cache.
30250 @kindex maint print objfiles
30251 @cindex info for known object files
30252 @item maint print objfiles
30253 Print a dump of all known object files. For each object file, this
30254 command prints its name, address in memory, and all of its psymtabs
30257 @kindex maint print section-scripts
30258 @cindex info for known .debug_gdb_scripts-loaded scripts
30259 @item maint print section-scripts [@var{regexp}]
30260 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30261 If @var{regexp} is specified, only print scripts loaded by object files
30262 matching @var{regexp}.
30263 For each script, this command prints its name as specified in the objfile,
30264 and the full path if known.
30265 @xref{.debug_gdb_scripts section}.
30267 @kindex maint print statistics
30268 @cindex bcache statistics
30269 @item maint print statistics
30270 This command prints, for each object file in the program, various data
30271 about that object file followed by the byte cache (@dfn{bcache})
30272 statistics for the object file. The objfile data includes the number
30273 of minimal, partial, full, and stabs symbols, the number of types
30274 defined by the objfile, the number of as yet unexpanded psym tables,
30275 the number of line tables and string tables, and the amount of memory
30276 used by the various tables. The bcache statistics include the counts,
30277 sizes, and counts of duplicates of all and unique objects, max,
30278 average, and median entry size, total memory used and its overhead and
30279 savings, and various measures of the hash table size and chain
30282 @kindex maint print target-stack
30283 @cindex target stack description
30284 @item maint print target-stack
30285 A @dfn{target} is an interface between the debugger and a particular
30286 kind of file or process. Targets can be stacked in @dfn{strata},
30287 so that more than one target can potentially respond to a request.
30288 In particular, memory accesses will walk down the stack of targets
30289 until they find a target that is interested in handling that particular
30292 This command prints a short description of each layer that was pushed on
30293 the @dfn{target stack}, starting from the top layer down to the bottom one.
30295 @kindex maint print type
30296 @cindex type chain of a data type
30297 @item maint print type @var{expr}
30298 Print the type chain for a type specified by @var{expr}. The argument
30299 can be either a type name or a symbol. If it is a symbol, the type of
30300 that symbol is described. The type chain produced by this command is
30301 a recursive definition of the data type as stored in @value{GDBN}'s
30302 data structures, including its flags and contained types.
30304 @kindex maint set dwarf2 always-disassemble
30305 @kindex maint show dwarf2 always-disassemble
30306 @item maint set dwarf2 always-disassemble
30307 @item maint show dwarf2 always-disassemble
30308 Control the behavior of @code{info address} when using DWARF debugging
30311 The default is @code{off}, which means that @value{GDBN} should try to
30312 describe a variable's location in an easily readable format. When
30313 @code{on}, @value{GDBN} will instead display the DWARF location
30314 expression in an assembly-like format. Note that some locations are
30315 too complex for @value{GDBN} to describe simply; in this case you will
30316 always see the disassembly form.
30318 Here is an example of the resulting disassembly:
30321 (gdb) info addr argc
30322 Symbol "argc" is a complex DWARF expression:
30326 For more information on these expressions, see
30327 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30329 @kindex maint set dwarf2 max-cache-age
30330 @kindex maint show dwarf2 max-cache-age
30331 @item maint set dwarf2 max-cache-age
30332 @itemx maint show dwarf2 max-cache-age
30333 Control the DWARF 2 compilation unit cache.
30335 @cindex DWARF 2 compilation units cache
30336 In object files with inter-compilation-unit references, such as those
30337 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30338 reader needs to frequently refer to previously read compilation units.
30339 This setting controls how long a compilation unit will remain in the
30340 cache if it is not referenced. A higher limit means that cached
30341 compilation units will be stored in memory longer, and more total
30342 memory will be used. Setting it to zero disables caching, which will
30343 slow down @value{GDBN} startup, but reduce memory consumption.
30345 @kindex maint set profile
30346 @kindex maint show profile
30347 @cindex profiling GDB
30348 @item maint set profile
30349 @itemx maint show profile
30350 Control profiling of @value{GDBN}.
30352 Profiling will be disabled until you use the @samp{maint set profile}
30353 command to enable it. When you enable profiling, the system will begin
30354 collecting timing and execution count data; when you disable profiling or
30355 exit @value{GDBN}, the results will be written to a log file. Remember that
30356 if you use profiling, @value{GDBN} will overwrite the profiling log file
30357 (often called @file{gmon.out}). If you have a record of important profiling
30358 data in a @file{gmon.out} file, be sure to move it to a safe location.
30360 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30361 compiled with the @samp{-pg} compiler option.
30363 @kindex maint set show-debug-regs
30364 @kindex maint show show-debug-regs
30365 @cindex hardware debug registers
30366 @item maint set show-debug-regs
30367 @itemx maint show show-debug-regs
30368 Control whether to show variables that mirror the hardware debug
30369 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30370 enabled, the debug registers values are shown when @value{GDBN} inserts or
30371 removes a hardware breakpoint or watchpoint, and when the inferior
30372 triggers a hardware-assisted breakpoint or watchpoint.
30374 @kindex maint set show-all-tib
30375 @kindex maint show show-all-tib
30376 @item maint set show-all-tib
30377 @itemx maint show show-all-tib
30378 Control whether to show all non zero areas within a 1k block starting
30379 at thread local base, when using the @samp{info w32 thread-information-block}
30382 @kindex maint space
30383 @cindex memory used by commands
30385 Control whether to display memory usage for each command. If set to a
30386 nonzero value, @value{GDBN} will display how much memory each command
30387 took, following the command's own output. This can also be requested
30388 by invoking @value{GDBN} with the @option{--statistics} command-line
30389 switch (@pxref{Mode Options}).
30392 @cindex time of command execution
30394 Control whether to display the execution time for each command. If
30395 set to a nonzero value, @value{GDBN} will display how much time it
30396 took to execute each command, following the command's own output.
30397 The time is not printed for the commands that run the target, since
30398 there's no mechanism currently to compute how much time was spend
30399 by @value{GDBN} and how much time was spend by the program been debugged.
30400 it's not possibly currently
30401 This can also be requested by invoking @value{GDBN} with the
30402 @option{--statistics} command-line switch (@pxref{Mode Options}).
30404 @kindex maint translate-address
30405 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30406 Find the symbol stored at the location specified by the address
30407 @var{addr} and an optional section name @var{section}. If found,
30408 @value{GDBN} prints the name of the closest symbol and an offset from
30409 the symbol's location to the specified address. This is similar to
30410 the @code{info address} command (@pxref{Symbols}), except that this
30411 command also allows to find symbols in other sections.
30413 If section was not specified, the section in which the symbol was found
30414 is also printed. For dynamically linked executables, the name of
30415 executable or shared library containing the symbol is printed as well.
30419 The following command is useful for non-interactive invocations of
30420 @value{GDBN}, such as in the test suite.
30423 @item set watchdog @var{nsec}
30424 @kindex set watchdog
30425 @cindex watchdog timer
30426 @cindex timeout for commands
30427 Set the maximum number of seconds @value{GDBN} will wait for the
30428 target operation to finish. If this time expires, @value{GDBN}
30429 reports and error and the command is aborted.
30431 @item show watchdog
30432 Show the current setting of the target wait timeout.
30435 @node Remote Protocol
30436 @appendix @value{GDBN} Remote Serial Protocol
30441 * Stop Reply Packets::
30442 * General Query Packets::
30443 * Architecture-Specific Protocol Details::
30444 * Tracepoint Packets::
30445 * Host I/O Packets::
30447 * Notification Packets::
30448 * Remote Non-Stop::
30449 * Packet Acknowledgment::
30451 * File-I/O Remote Protocol Extension::
30452 * Library List Format::
30453 * Memory Map Format::
30454 * Thread List Format::
30460 There may be occasions when you need to know something about the
30461 protocol---for example, if there is only one serial port to your target
30462 machine, you might want your program to do something special if it
30463 recognizes a packet meant for @value{GDBN}.
30465 In the examples below, @samp{->} and @samp{<-} are used to indicate
30466 transmitted and received data, respectively.
30468 @cindex protocol, @value{GDBN} remote serial
30469 @cindex serial protocol, @value{GDBN} remote
30470 @cindex remote serial protocol
30471 All @value{GDBN} commands and responses (other than acknowledgments
30472 and notifications, see @ref{Notification Packets}) are sent as a
30473 @var{packet}. A @var{packet} is introduced with the character
30474 @samp{$}, the actual @var{packet-data}, and the terminating character
30475 @samp{#} followed by a two-digit @var{checksum}:
30478 @code{$}@var{packet-data}@code{#}@var{checksum}
30482 @cindex checksum, for @value{GDBN} remote
30484 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30485 characters between the leading @samp{$} and the trailing @samp{#} (an
30486 eight bit unsigned checksum).
30488 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30489 specification also included an optional two-digit @var{sequence-id}:
30492 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30495 @cindex sequence-id, for @value{GDBN} remote
30497 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30498 has never output @var{sequence-id}s. Stubs that handle packets added
30499 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30501 When either the host or the target machine receives a packet, the first
30502 response expected is an acknowledgment: either @samp{+} (to indicate
30503 the package was received correctly) or @samp{-} (to request
30507 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30512 The @samp{+}/@samp{-} acknowledgments can be disabled
30513 once a connection is established.
30514 @xref{Packet Acknowledgment}, for details.
30516 The host (@value{GDBN}) sends @var{command}s, and the target (the
30517 debugging stub incorporated in your program) sends a @var{response}. In
30518 the case of step and continue @var{command}s, the response is only sent
30519 when the operation has completed, and the target has again stopped all
30520 threads in all attached processes. This is the default all-stop mode
30521 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30522 execution mode; see @ref{Remote Non-Stop}, for details.
30524 @var{packet-data} consists of a sequence of characters with the
30525 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30528 @cindex remote protocol, field separator
30529 Fields within the packet should be separated using @samp{,} @samp{;} or
30530 @samp{:}. Except where otherwise noted all numbers are represented in
30531 @sc{hex} with leading zeros suppressed.
30533 Implementors should note that prior to @value{GDBN} 5.0, the character
30534 @samp{:} could not appear as the third character in a packet (as it
30535 would potentially conflict with the @var{sequence-id}).
30537 @cindex remote protocol, binary data
30538 @anchor{Binary Data}
30539 Binary data in most packets is encoded either as two hexadecimal
30540 digits per byte of binary data. This allowed the traditional remote
30541 protocol to work over connections which were only seven-bit clean.
30542 Some packets designed more recently assume an eight-bit clean
30543 connection, and use a more efficient encoding to send and receive
30546 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30547 as an escape character. Any escaped byte is transmitted as the escape
30548 character followed by the original character XORed with @code{0x20}.
30549 For example, the byte @code{0x7d} would be transmitted as the two
30550 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30551 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30552 @samp{@}}) must always be escaped. Responses sent by the stub
30553 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30554 is not interpreted as the start of a run-length encoded sequence
30557 Response @var{data} can be run-length encoded to save space.
30558 Run-length encoding replaces runs of identical characters with one
30559 instance of the repeated character, followed by a @samp{*} and a
30560 repeat count. The repeat count is itself sent encoded, to avoid
30561 binary characters in @var{data}: a value of @var{n} is sent as
30562 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30563 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30564 code 32) for a repeat count of 3. (This is because run-length
30565 encoding starts to win for counts 3 or more.) Thus, for example,
30566 @samp{0* } is a run-length encoding of ``0000'': the space character
30567 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30570 The printable characters @samp{#} and @samp{$} or with a numeric value
30571 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30572 seven repeats (@samp{$}) can be expanded using a repeat count of only
30573 five (@samp{"}). For example, @samp{00000000} can be encoded as
30576 The error response returned for some packets includes a two character
30577 error number. That number is not well defined.
30579 @cindex empty response, for unsupported packets
30580 For any @var{command} not supported by the stub, an empty response
30581 (@samp{$#00}) should be returned. That way it is possible to extend the
30582 protocol. A newer @value{GDBN} can tell if a packet is supported based
30585 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30586 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30592 The following table provides a complete list of all currently defined
30593 @var{command}s and their corresponding response @var{data}.
30594 @xref{File-I/O Remote Protocol Extension}, for details about the File
30595 I/O extension of the remote protocol.
30597 Each packet's description has a template showing the packet's overall
30598 syntax, followed by an explanation of the packet's meaning. We
30599 include spaces in some of the templates for clarity; these are not
30600 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30601 separate its components. For example, a template like @samp{foo
30602 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30603 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30604 @var{baz}. @value{GDBN} does not transmit a space character between the
30605 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30608 @cindex @var{thread-id}, in remote protocol
30609 @anchor{thread-id syntax}
30610 Several packets and replies include a @var{thread-id} field to identify
30611 a thread. Normally these are positive numbers with a target-specific
30612 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30613 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30616 In addition, the remote protocol supports a multiprocess feature in
30617 which the @var{thread-id} syntax is extended to optionally include both
30618 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30619 The @var{pid} (process) and @var{tid} (thread) components each have the
30620 format described above: a positive number with target-specific
30621 interpretation formatted as a big-endian hex string, literal @samp{-1}
30622 to indicate all processes or threads (respectively), or @samp{0} to
30623 indicate an arbitrary process or thread. Specifying just a process, as
30624 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30625 error to specify all processes but a specific thread, such as
30626 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30627 for those packets and replies explicitly documented to include a process
30628 ID, rather than a @var{thread-id}.
30630 The multiprocess @var{thread-id} syntax extensions are only used if both
30631 @value{GDBN} and the stub report support for the @samp{multiprocess}
30632 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30635 Note that all packet forms beginning with an upper- or lower-case
30636 letter, other than those described here, are reserved for future use.
30638 Here are the packet descriptions.
30643 @cindex @samp{!} packet
30644 @anchor{extended mode}
30645 Enable extended mode. In extended mode, the remote server is made
30646 persistent. The @samp{R} packet is used to restart the program being
30652 The remote target both supports and has enabled extended mode.
30656 @cindex @samp{?} packet
30657 Indicate the reason the target halted. The reply is the same as for
30658 step and continue. This packet has a special interpretation when the
30659 target is in non-stop mode; see @ref{Remote Non-Stop}.
30662 @xref{Stop Reply Packets}, for the reply specifications.
30664 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30665 @cindex @samp{A} packet
30666 Initialized @code{argv[]} array passed into program. @var{arglen}
30667 specifies the number of bytes in the hex encoded byte stream
30668 @var{arg}. See @code{gdbserver} for more details.
30673 The arguments were set.
30679 @cindex @samp{b} packet
30680 (Don't use this packet; its behavior is not well-defined.)
30681 Change the serial line speed to @var{baud}.
30683 JTC: @emph{When does the transport layer state change? When it's
30684 received, or after the ACK is transmitted. In either case, there are
30685 problems if the command or the acknowledgment packet is dropped.}
30687 Stan: @emph{If people really wanted to add something like this, and get
30688 it working for the first time, they ought to modify ser-unix.c to send
30689 some kind of out-of-band message to a specially-setup stub and have the
30690 switch happen "in between" packets, so that from remote protocol's point
30691 of view, nothing actually happened.}
30693 @item B @var{addr},@var{mode}
30694 @cindex @samp{B} packet
30695 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30696 breakpoint at @var{addr}.
30698 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30699 (@pxref{insert breakpoint or watchpoint packet}).
30701 @cindex @samp{bc} packet
30704 Backward continue. Execute the target system in reverse. No parameter.
30705 @xref{Reverse Execution}, for more information.
30708 @xref{Stop Reply Packets}, for the reply specifications.
30710 @cindex @samp{bs} packet
30713 Backward single step. Execute one instruction in reverse. No parameter.
30714 @xref{Reverse Execution}, for more information.
30717 @xref{Stop Reply Packets}, for the reply specifications.
30719 @item c @r{[}@var{addr}@r{]}
30720 @cindex @samp{c} packet
30721 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30722 resume at current address.
30725 @xref{Stop Reply Packets}, for the reply specifications.
30727 @item C @var{sig}@r{[};@var{addr}@r{]}
30728 @cindex @samp{C} packet
30729 Continue with signal @var{sig} (hex signal number). If
30730 @samp{;@var{addr}} is omitted, resume at same address.
30733 @xref{Stop Reply Packets}, for the reply specifications.
30736 @cindex @samp{d} packet
30739 Don't use this packet; instead, define a general set packet
30740 (@pxref{General Query Packets}).
30744 @cindex @samp{D} packet
30745 The first form of the packet is used to detach @value{GDBN} from the
30746 remote system. It is sent to the remote target
30747 before @value{GDBN} disconnects via the @code{detach} command.
30749 The second form, including a process ID, is used when multiprocess
30750 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30751 detach only a specific process. The @var{pid} is specified as a
30752 big-endian hex string.
30762 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30763 @cindex @samp{F} packet
30764 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30765 This is part of the File-I/O protocol extension. @xref{File-I/O
30766 Remote Protocol Extension}, for the specification.
30769 @anchor{read registers packet}
30770 @cindex @samp{g} packet
30771 Read general registers.
30775 @item @var{XX@dots{}}
30776 Each byte of register data is described by two hex digits. The bytes
30777 with the register are transmitted in target byte order. The size of
30778 each register and their position within the @samp{g} packet are
30779 determined by the @value{GDBN} internal gdbarch functions
30780 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30781 specification of several standard @samp{g} packets is specified below.
30786 @item G @var{XX@dots{}}
30787 @cindex @samp{G} packet
30788 Write general registers. @xref{read registers packet}, for a
30789 description of the @var{XX@dots{}} data.
30799 @item H @var{c} @var{thread-id}
30800 @cindex @samp{H} packet
30801 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30802 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30803 should be @samp{c} for step and continue operations, @samp{g} for other
30804 operations. The thread designator @var{thread-id} has the format and
30805 interpretation described in @ref{thread-id syntax}.
30816 @c 'H': How restrictive (or permissive) is the thread model. If a
30817 @c thread is selected and stopped, are other threads allowed
30818 @c to continue to execute? As I mentioned above, I think the
30819 @c semantics of each command when a thread is selected must be
30820 @c described. For example:
30822 @c 'g': If the stub supports threads and a specific thread is
30823 @c selected, returns the register block from that thread;
30824 @c otherwise returns current registers.
30826 @c 'G' If the stub supports threads and a specific thread is
30827 @c selected, sets the registers of the register block of
30828 @c that thread; otherwise sets current registers.
30830 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
30831 @anchor{cycle step packet}
30832 @cindex @samp{i} packet
30833 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
30834 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
30835 step starting at that address.
30838 @cindex @samp{I} packet
30839 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
30843 @cindex @samp{k} packet
30846 FIXME: @emph{There is no description of how to operate when a specific
30847 thread context has been selected (i.e.@: does 'k' kill only that
30850 @item m @var{addr},@var{length}
30851 @cindex @samp{m} packet
30852 Read @var{length} bytes of memory starting at address @var{addr}.
30853 Note that @var{addr} may not be aligned to any particular boundary.
30855 The stub need not use any particular size or alignment when gathering
30856 data from memory for the response; even if @var{addr} is word-aligned
30857 and @var{length} is a multiple of the word size, the stub is free to
30858 use byte accesses, or not. For this reason, this packet may not be
30859 suitable for accessing memory-mapped I/O devices.
30860 @cindex alignment of remote memory accesses
30861 @cindex size of remote memory accesses
30862 @cindex memory, alignment and size of remote accesses
30866 @item @var{XX@dots{}}
30867 Memory contents; each byte is transmitted as a two-digit hexadecimal
30868 number. The reply may contain fewer bytes than requested if the
30869 server was able to read only part of the region of memory.
30874 @item M @var{addr},@var{length}:@var{XX@dots{}}
30875 @cindex @samp{M} packet
30876 Write @var{length} bytes of memory starting at address @var{addr}.
30877 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30878 hexadecimal number.
30885 for an error (this includes the case where only part of the data was
30890 @cindex @samp{p} packet
30891 Read the value of register @var{n}; @var{n} is in hex.
30892 @xref{read registers packet}, for a description of how the returned
30893 register value is encoded.
30897 @item @var{XX@dots{}}
30898 the register's value
30902 Indicating an unrecognized @var{query}.
30905 @item P @var{n@dots{}}=@var{r@dots{}}
30906 @anchor{write register packet}
30907 @cindex @samp{P} packet
30908 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30909 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30910 digits for each byte in the register (target byte order).
30920 @item q @var{name} @var{params}@dots{}
30921 @itemx Q @var{name} @var{params}@dots{}
30922 @cindex @samp{q} packet
30923 @cindex @samp{Q} packet
30924 General query (@samp{q}) and set (@samp{Q}). These packets are
30925 described fully in @ref{General Query Packets}.
30928 @cindex @samp{r} packet
30929 Reset the entire system.
30931 Don't use this packet; use the @samp{R} packet instead.
30934 @cindex @samp{R} packet
30935 Restart the program being debugged. @var{XX}, while needed, is ignored.
30936 This packet is only available in extended mode (@pxref{extended mode}).
30938 The @samp{R} packet has no reply.
30940 @item s @r{[}@var{addr}@r{]}
30941 @cindex @samp{s} packet
30942 Single step. @var{addr} is the address at which to resume. If
30943 @var{addr} is omitted, resume at same address.
30946 @xref{Stop Reply Packets}, for the reply specifications.
30948 @item S @var{sig}@r{[};@var{addr}@r{]}
30949 @anchor{step with signal packet}
30950 @cindex @samp{S} packet
30951 Step with signal. This is analogous to the @samp{C} packet, but
30952 requests a single-step, rather than a normal resumption of execution.
30955 @xref{Stop Reply Packets}, for the reply specifications.
30957 @item t @var{addr}:@var{PP},@var{MM}
30958 @cindex @samp{t} packet
30959 Search backwards starting at address @var{addr} for a match with pattern
30960 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30961 @var{addr} must be at least 3 digits.
30963 @item T @var{thread-id}
30964 @cindex @samp{T} packet
30965 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30970 thread is still alive
30976 Packets starting with @samp{v} are identified by a multi-letter name,
30977 up to the first @samp{;} or @samp{?} (or the end of the packet).
30979 @item vAttach;@var{pid}
30980 @cindex @samp{vAttach} packet
30981 Attach to a new process with the specified process ID @var{pid}.
30982 The process ID is a
30983 hexadecimal integer identifying the process. In all-stop mode, all
30984 threads in the attached process are stopped; in non-stop mode, it may be
30985 attached without being stopped if that is supported by the target.
30987 @c In non-stop mode, on a successful vAttach, the stub should set the
30988 @c current thread to a thread of the newly-attached process. After
30989 @c attaching, GDB queries for the attached process's thread ID with qC.
30990 @c Also note that, from a user perspective, whether or not the
30991 @c target is stopped on attach in non-stop mode depends on whether you
30992 @c use the foreground or background version of the attach command, not
30993 @c on what vAttach does; GDB does the right thing with respect to either
30994 @c stopping or restarting threads.
30996 This packet is only available in extended mode (@pxref{extended mode}).
31002 @item @r{Any stop packet}
31003 for success in all-stop mode (@pxref{Stop Reply Packets})
31005 for success in non-stop mode (@pxref{Remote Non-Stop})
31008 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31009 @cindex @samp{vCont} packet
31010 Resume the inferior, specifying different actions for each thread.
31011 If an action is specified with no @var{thread-id}, then it is applied to any
31012 threads that don't have a specific action specified; if no default action is
31013 specified then other threads should remain stopped in all-stop mode and
31014 in their current state in non-stop mode.
31015 Specifying multiple
31016 default actions is an error; specifying no actions is also an error.
31017 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31019 Currently supported actions are:
31025 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31029 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31034 The optional argument @var{addr} normally associated with the
31035 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31036 not supported in @samp{vCont}.
31038 The @samp{t} action is only relevant in non-stop mode
31039 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31040 A stop reply should be generated for any affected thread not already stopped.
31041 When a thread is stopped by means of a @samp{t} action,
31042 the corresponding stop reply should indicate that the thread has stopped with
31043 signal @samp{0}, regardless of whether the target uses some other signal
31044 as an implementation detail.
31047 @xref{Stop Reply Packets}, for the reply specifications.
31050 @cindex @samp{vCont?} packet
31051 Request a list of actions supported by the @samp{vCont} packet.
31055 @item vCont@r{[};@var{action}@dots{}@r{]}
31056 The @samp{vCont} packet is supported. Each @var{action} is a supported
31057 command in the @samp{vCont} packet.
31059 The @samp{vCont} packet is not supported.
31062 @item vFile:@var{operation}:@var{parameter}@dots{}
31063 @cindex @samp{vFile} packet
31064 Perform a file operation on the target system. For details,
31065 see @ref{Host I/O Packets}.
31067 @item vFlashErase:@var{addr},@var{length}
31068 @cindex @samp{vFlashErase} packet
31069 Direct the stub to erase @var{length} bytes of flash starting at
31070 @var{addr}. The region may enclose any number of flash blocks, but
31071 its start and end must fall on block boundaries, as indicated by the
31072 flash block size appearing in the memory map (@pxref{Memory Map
31073 Format}). @value{GDBN} groups flash memory programming operations
31074 together, and sends a @samp{vFlashDone} request after each group; the
31075 stub is allowed to delay erase operation until the @samp{vFlashDone}
31076 packet is received.
31078 The stub must support @samp{vCont} if it reports support for
31079 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31080 this case @samp{vCont} actions can be specified to apply to all threads
31081 in a process by using the @samp{p@var{pid}.-1} form of the
31092 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31093 @cindex @samp{vFlashWrite} packet
31094 Direct the stub to write data to flash address @var{addr}. The data
31095 is passed in binary form using the same encoding as for the @samp{X}
31096 packet (@pxref{Binary Data}). The memory ranges specified by
31097 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31098 not overlap, and must appear in order of increasing addresses
31099 (although @samp{vFlashErase} packets for higher addresses may already
31100 have been received; the ordering is guaranteed only between
31101 @samp{vFlashWrite} packets). If a packet writes to an address that was
31102 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31103 target-specific method, the results are unpredictable.
31111 for vFlashWrite addressing non-flash memory
31117 @cindex @samp{vFlashDone} packet
31118 Indicate to the stub that flash programming operation is finished.
31119 The stub is permitted to delay or batch the effects of a group of
31120 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31121 @samp{vFlashDone} packet is received. The contents of the affected
31122 regions of flash memory are unpredictable until the @samp{vFlashDone}
31123 request is completed.
31125 @item vKill;@var{pid}
31126 @cindex @samp{vKill} packet
31127 Kill the process with the specified process ID. @var{pid} is a
31128 hexadecimal integer identifying the process. This packet is used in
31129 preference to @samp{k} when multiprocess protocol extensions are
31130 supported; see @ref{multiprocess extensions}.
31140 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31141 @cindex @samp{vRun} packet
31142 Run the program @var{filename}, passing it each @var{argument} on its
31143 command line. The file and arguments are hex-encoded strings. If
31144 @var{filename} is an empty string, the stub may use a default program
31145 (e.g.@: the last program run). The program is created in the stopped
31148 @c FIXME: What about non-stop mode?
31150 This packet is only available in extended mode (@pxref{extended mode}).
31156 @item @r{Any stop packet}
31157 for success (@pxref{Stop Reply Packets})
31161 @anchor{vStopped packet}
31162 @cindex @samp{vStopped} packet
31164 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31165 reply and prompt for the stub to report another one.
31169 @item @r{Any stop packet}
31170 if there is another unreported stop event (@pxref{Stop Reply Packets})
31172 if there are no unreported stop events
31175 @item X @var{addr},@var{length}:@var{XX@dots{}}
31177 @cindex @samp{X} packet
31178 Write data to memory, where the data is transmitted in binary.
31179 @var{addr} is address, @var{length} is number of bytes,
31180 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31190 @item z @var{type},@var{addr},@var{kind}
31191 @itemx Z @var{type},@var{addr},@var{kind}
31192 @anchor{insert breakpoint or watchpoint packet}
31193 @cindex @samp{z} packet
31194 @cindex @samp{Z} packets
31195 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31196 watchpoint starting at address @var{address} of kind @var{kind}.
31198 Each breakpoint and watchpoint packet @var{type} is documented
31201 @emph{Implementation notes: A remote target shall return an empty string
31202 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31203 remote target shall support either both or neither of a given
31204 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31205 avoid potential problems with duplicate packets, the operations should
31206 be implemented in an idempotent way.}
31208 @item z0,@var{addr},@var{kind}
31209 @itemx Z0,@var{addr},@var{kind}
31210 @cindex @samp{z0} packet
31211 @cindex @samp{Z0} packet
31212 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31213 @var{addr} of type @var{kind}.
31215 A memory breakpoint is implemented by replacing the instruction at
31216 @var{addr} with a software breakpoint or trap instruction. The
31217 @var{kind} is target-specific and typically indicates the size of
31218 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31219 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31220 architectures have additional meanings for @var{kind};
31221 see @ref{Architecture-Specific Protocol Details}.
31223 @emph{Implementation note: It is possible for a target to copy or move
31224 code that contains memory breakpoints (e.g., when implementing
31225 overlays). The behavior of this packet, in the presence of such a
31226 target, is not defined.}
31238 @item z1,@var{addr},@var{kind}
31239 @itemx Z1,@var{addr},@var{kind}
31240 @cindex @samp{z1} packet
31241 @cindex @samp{Z1} packet
31242 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31243 address @var{addr}.
31245 A hardware breakpoint is implemented using a mechanism that is not
31246 dependant on being able to modify the target's memory. @var{kind}
31247 has the same meaning as in @samp{Z0} packets.
31249 @emph{Implementation note: A hardware breakpoint is not affected by code
31262 @item z2,@var{addr},@var{kind}
31263 @itemx Z2,@var{addr},@var{kind}
31264 @cindex @samp{z2} packet
31265 @cindex @samp{Z2} packet
31266 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31267 @var{kind} is interpreted as the number of bytes to watch.
31279 @item z3,@var{addr},@var{kind}
31280 @itemx Z3,@var{addr},@var{kind}
31281 @cindex @samp{z3} packet
31282 @cindex @samp{Z3} packet
31283 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31284 @var{kind} is interpreted as the number of bytes to watch.
31296 @item z4,@var{addr},@var{kind}
31297 @itemx Z4,@var{addr},@var{kind}
31298 @cindex @samp{z4} packet
31299 @cindex @samp{Z4} packet
31300 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31301 @var{kind} is interpreted as the number of bytes to watch.
31315 @node Stop Reply Packets
31316 @section Stop Reply Packets
31317 @cindex stop reply packets
31319 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31320 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31321 receive any of the below as a reply. Except for @samp{?}
31322 and @samp{vStopped}, that reply is only returned
31323 when the target halts. In the below the exact meaning of @dfn{signal
31324 number} is defined by the header @file{include/gdb/signals.h} in the
31325 @value{GDBN} source code.
31327 As in the description of request packets, we include spaces in the
31328 reply templates for clarity; these are not part of the reply packet's
31329 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31335 The program received signal number @var{AA} (a two-digit hexadecimal
31336 number). This is equivalent to a @samp{T} response with no
31337 @var{n}:@var{r} pairs.
31339 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31340 @cindex @samp{T} packet reply
31341 The program received signal number @var{AA} (a two-digit hexadecimal
31342 number). This is equivalent to an @samp{S} response, except that the
31343 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31344 and other information directly in the stop reply packet, reducing
31345 round-trip latency. Single-step and breakpoint traps are reported
31346 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31350 If @var{n} is a hexadecimal number, it is a register number, and the
31351 corresponding @var{r} gives that register's value. @var{r} is a
31352 series of bytes in target byte order, with each byte given by a
31353 two-digit hex number.
31356 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31357 the stopped thread, as specified in @ref{thread-id syntax}.
31360 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31361 the core on which the stop event was detected.
31364 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31365 specific event that stopped the target. The currently defined stop
31366 reasons are listed below. @var{aa} should be @samp{05}, the trap
31367 signal. At most one stop reason should be present.
31370 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31371 and go on to the next; this allows us to extend the protocol in the
31375 The currently defined stop reasons are:
31381 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31384 @cindex shared library events, remote reply
31386 The packet indicates that the loaded libraries have changed.
31387 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31388 list of loaded libraries. @var{r} is ignored.
31390 @cindex replay log events, remote reply
31392 The packet indicates that the target cannot continue replaying
31393 logged execution events, because it has reached the end (or the
31394 beginning when executing backward) of the log. The value of @var{r}
31395 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31396 for more information.
31400 @itemx W @var{AA} ; process:@var{pid}
31401 The process exited, and @var{AA} is the exit status. This is only
31402 applicable to certain targets.
31404 The second form of the response, including the process ID of the exited
31405 process, can be used only when @value{GDBN} has reported support for
31406 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31407 The @var{pid} is formatted as a big-endian hex string.
31410 @itemx X @var{AA} ; process:@var{pid}
31411 The process terminated with signal @var{AA}.
31413 The second form of the response, including the process ID of the
31414 terminated process, can be used only when @value{GDBN} has reported
31415 support for multiprocess protocol extensions; see @ref{multiprocess
31416 extensions}. The @var{pid} is formatted as a big-endian hex string.
31418 @item O @var{XX}@dots{}
31419 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31420 written as the program's console output. This can happen at any time
31421 while the program is running and the debugger should continue to wait
31422 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31424 @item F @var{call-id},@var{parameter}@dots{}
31425 @var{call-id} is the identifier which says which host system call should
31426 be called. This is just the name of the function. Translation into the
31427 correct system call is only applicable as it's defined in @value{GDBN}.
31428 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31431 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31432 this very system call.
31434 The target replies with this packet when it expects @value{GDBN} to
31435 call a host system call on behalf of the target. @value{GDBN} replies
31436 with an appropriate @samp{F} packet and keeps up waiting for the next
31437 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31438 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31439 Protocol Extension}, for more details.
31443 @node General Query Packets
31444 @section General Query Packets
31445 @cindex remote query requests
31447 Packets starting with @samp{q} are @dfn{general query packets};
31448 packets starting with @samp{Q} are @dfn{general set packets}. General
31449 query and set packets are a semi-unified form for retrieving and
31450 sending information to and from the stub.
31452 The initial letter of a query or set packet is followed by a name
31453 indicating what sort of thing the packet applies to. For example,
31454 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31455 definitions with the stub. These packet names follow some
31460 The name must not contain commas, colons or semicolons.
31462 Most @value{GDBN} query and set packets have a leading upper case
31465 The names of custom vendor packets should use a company prefix, in
31466 lower case, followed by a period. For example, packets designed at
31467 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31468 foos) or @samp{Qacme.bar} (for setting bars).
31471 The name of a query or set packet should be separated from any
31472 parameters by a @samp{:}; the parameters themselves should be
31473 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31474 full packet name, and check for a separator or the end of the packet,
31475 in case two packet names share a common prefix. New packets should not begin
31476 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31477 packets predate these conventions, and have arguments without any terminator
31478 for the packet name; we suspect they are in widespread use in places that
31479 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31480 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31483 Like the descriptions of the other packets, each description here
31484 has a template showing the packet's overall syntax, followed by an
31485 explanation of the packet's meaning. We include spaces in some of the
31486 templates for clarity; these are not part of the packet's syntax. No
31487 @value{GDBN} packet uses spaces to separate its components.
31489 Here are the currently defined query and set packets:
31493 @item QAllow:@var{op}:@var{val}@dots{}
31494 @cindex @samp{QAllow} packet
31495 Specify which operations @value{GDBN} expects to request of the
31496 target, as a semicolon-separated list of operation name and value
31497 pairs. Possible values for @var{op} include @samp{WriteReg},
31498 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31499 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31500 indicating that @value{GDBN} will not request the operation, or 1,
31501 indicating that it may. (The target can then use this to set up its
31502 own internals optimally, for instance if the debugger never expects to
31503 insert breakpoints, it may not need to install its own trap handler.)
31506 @cindex current thread, remote request
31507 @cindex @samp{qC} packet
31508 Return the current thread ID.
31512 @item QC @var{thread-id}
31513 Where @var{thread-id} is a thread ID as documented in
31514 @ref{thread-id syntax}.
31515 @item @r{(anything else)}
31516 Any other reply implies the old thread ID.
31519 @item qCRC:@var{addr},@var{length}
31520 @cindex CRC of memory block, remote request
31521 @cindex @samp{qCRC} packet
31522 Compute the CRC checksum of a block of memory using CRC-32 defined in
31523 IEEE 802.3. The CRC is computed byte at a time, taking the most
31524 significant bit of each byte first. The initial pattern code
31525 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31527 @emph{Note:} This is the same CRC used in validating separate debug
31528 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31529 Files}). However the algorithm is slightly different. When validating
31530 separate debug files, the CRC is computed taking the @emph{least}
31531 significant bit of each byte first, and the final result is inverted to
31532 detect trailing zeros.
31537 An error (such as memory fault)
31538 @item C @var{crc32}
31539 The specified memory region's checksum is @var{crc32}.
31543 @itemx qsThreadInfo
31544 @cindex list active threads, remote request
31545 @cindex @samp{qfThreadInfo} packet
31546 @cindex @samp{qsThreadInfo} packet
31547 Obtain a list of all active thread IDs from the target (OS). Since there
31548 may be too many active threads to fit into one reply packet, this query
31549 works iteratively: it may require more than one query/reply sequence to
31550 obtain the entire list of threads. The first query of the sequence will
31551 be the @samp{qfThreadInfo} query; subsequent queries in the
31552 sequence will be the @samp{qsThreadInfo} query.
31554 NOTE: This packet replaces the @samp{qL} query (see below).
31558 @item m @var{thread-id}
31560 @item m @var{thread-id},@var{thread-id}@dots{}
31561 a comma-separated list of thread IDs
31563 (lower case letter @samp{L}) denotes end of list.
31566 In response to each query, the target will reply with a list of one or
31567 more thread IDs, separated by commas.
31568 @value{GDBN} will respond to each reply with a request for more thread
31569 ids (using the @samp{qs} form of the query), until the target responds
31570 with @samp{l} (lower-case el, for @dfn{last}).
31571 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31574 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31575 @cindex get thread-local storage address, remote request
31576 @cindex @samp{qGetTLSAddr} packet
31577 Fetch the address associated with thread local storage specified
31578 by @var{thread-id}, @var{offset}, and @var{lm}.
31580 @var{thread-id} is the thread ID associated with the
31581 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31583 @var{offset} is the (big endian, hex encoded) offset associated with the
31584 thread local variable. (This offset is obtained from the debug
31585 information associated with the variable.)
31587 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31588 the load module associated with the thread local storage. For example,
31589 a @sc{gnu}/Linux system will pass the link map address of the shared
31590 object associated with the thread local storage under consideration.
31591 Other operating environments may choose to represent the load module
31592 differently, so the precise meaning of this parameter will vary.
31596 @item @var{XX}@dots{}
31597 Hex encoded (big endian) bytes representing the address of the thread
31598 local storage requested.
31601 An error occurred. @var{nn} are hex digits.
31604 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31607 @item qGetTIBAddr:@var{thread-id}
31608 @cindex get thread information block address
31609 @cindex @samp{qGetTIBAddr} packet
31610 Fetch address of the Windows OS specific Thread Information Block.
31612 @var{thread-id} is the thread ID associated with the thread.
31616 @item @var{XX}@dots{}
31617 Hex encoded (big endian) bytes representing the linear address of the
31618 thread information block.
31621 An error occured. This means that either the thread was not found, or the
31622 address could not be retrieved.
31625 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31628 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31629 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31630 digit) is one to indicate the first query and zero to indicate a
31631 subsequent query; @var{threadcount} (two hex digits) is the maximum
31632 number of threads the response packet can contain; and @var{nextthread}
31633 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31634 returned in the response as @var{argthread}.
31636 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31640 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31641 Where: @var{count} (two hex digits) is the number of threads being
31642 returned; @var{done} (one hex digit) is zero to indicate more threads
31643 and one indicates no further threads; @var{argthreadid} (eight hex
31644 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31645 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31646 digits). See @code{remote.c:parse_threadlist_response()}.
31650 @cindex section offsets, remote request
31651 @cindex @samp{qOffsets} packet
31652 Get section offsets that the target used when relocating the downloaded
31657 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31658 Relocate the @code{Text} section by @var{xxx} from its original address.
31659 Relocate the @code{Data} section by @var{yyy} from its original address.
31660 If the object file format provides segment information (e.g.@: @sc{elf}
31661 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31662 segments by the supplied offsets.
31664 @emph{Note: while a @code{Bss} offset may be included in the response,
31665 @value{GDBN} ignores this and instead applies the @code{Data} offset
31666 to the @code{Bss} section.}
31668 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31669 Relocate the first segment of the object file, which conventionally
31670 contains program code, to a starting address of @var{xxx}. If
31671 @samp{DataSeg} is specified, relocate the second segment, which
31672 conventionally contains modifiable data, to a starting address of
31673 @var{yyy}. @value{GDBN} will report an error if the object file
31674 does not contain segment information, or does not contain at least
31675 as many segments as mentioned in the reply. Extra segments are
31676 kept at fixed offsets relative to the last relocated segment.
31679 @item qP @var{mode} @var{thread-id}
31680 @cindex thread information, remote request
31681 @cindex @samp{qP} packet
31682 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31683 encoded 32 bit mode; @var{thread-id} is a thread ID
31684 (@pxref{thread-id syntax}).
31686 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31689 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31693 @cindex non-stop mode, remote request
31694 @cindex @samp{QNonStop} packet
31696 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31697 @xref{Remote Non-Stop}, for more information.
31702 The request succeeded.
31705 An error occurred. @var{nn} are hex digits.
31708 An empty reply indicates that @samp{QNonStop} is not supported by
31712 This packet is not probed by default; the remote stub must request it,
31713 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31714 Use of this packet is controlled by the @code{set non-stop} command;
31715 @pxref{Non-Stop Mode}.
31717 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31718 @cindex pass signals to inferior, remote request
31719 @cindex @samp{QPassSignals} packet
31720 @anchor{QPassSignals}
31721 Each listed @var{signal} should be passed directly to the inferior process.
31722 Signals are numbered identically to continue packets and stop replies
31723 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31724 strictly greater than the previous item. These signals do not need to stop
31725 the inferior, or be reported to @value{GDBN}. All other signals should be
31726 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31727 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31728 new list. This packet improves performance when using @samp{handle
31729 @var{signal} nostop noprint pass}.
31734 The request succeeded.
31737 An error occurred. @var{nn} are hex digits.
31740 An empty reply indicates that @samp{QPassSignals} is not supported by
31744 Use of this packet is controlled by the @code{set remote pass-signals}
31745 command (@pxref{Remote Configuration, set remote pass-signals}).
31746 This packet is not probed by default; the remote stub must request it,
31747 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31749 @item qRcmd,@var{command}
31750 @cindex execute remote command, remote request
31751 @cindex @samp{qRcmd} packet
31752 @var{command} (hex encoded) is passed to the local interpreter for
31753 execution. Invalid commands should be reported using the output
31754 string. Before the final result packet, the target may also respond
31755 with a number of intermediate @samp{O@var{output}} console output
31756 packets. @emph{Implementors should note that providing access to a
31757 stubs's interpreter may have security implications}.
31762 A command response with no output.
31764 A command response with the hex encoded output string @var{OUTPUT}.
31766 Indicate a badly formed request.
31768 An empty reply indicates that @samp{qRcmd} is not recognized.
31771 (Note that the @code{qRcmd} packet's name is separated from the
31772 command by a @samp{,}, not a @samp{:}, contrary to the naming
31773 conventions above. Please don't use this packet as a model for new
31776 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31777 @cindex searching memory, in remote debugging
31778 @cindex @samp{qSearch:memory} packet
31779 @anchor{qSearch memory}
31780 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31781 @var{address} and @var{length} are encoded in hex.
31782 @var{search-pattern} is a sequence of bytes, hex encoded.
31787 The pattern was not found.
31789 The pattern was found at @var{address}.
31791 A badly formed request or an error was encountered while searching memory.
31793 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31796 @item QStartNoAckMode
31797 @cindex @samp{QStartNoAckMode} packet
31798 @anchor{QStartNoAckMode}
31799 Request that the remote stub disable the normal @samp{+}/@samp{-}
31800 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31805 The stub has switched to no-acknowledgment mode.
31806 @value{GDBN} acknowledges this reponse,
31807 but neither the stub nor @value{GDBN} shall send or expect further
31808 @samp{+}/@samp{-} acknowledgments in the current connection.
31810 An empty reply indicates that the stub does not support no-acknowledgment mode.
31813 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31814 @cindex supported packets, remote query
31815 @cindex features of the remote protocol
31816 @cindex @samp{qSupported} packet
31817 @anchor{qSupported}
31818 Tell the remote stub about features supported by @value{GDBN}, and
31819 query the stub for features it supports. This packet allows
31820 @value{GDBN} and the remote stub to take advantage of each others'
31821 features. @samp{qSupported} also consolidates multiple feature probes
31822 at startup, to improve @value{GDBN} performance---a single larger
31823 packet performs better than multiple smaller probe packets on
31824 high-latency links. Some features may enable behavior which must not
31825 be on by default, e.g.@: because it would confuse older clients or
31826 stubs. Other features may describe packets which could be
31827 automatically probed for, but are not. These features must be
31828 reported before @value{GDBN} will use them. This ``default
31829 unsupported'' behavior is not appropriate for all packets, but it
31830 helps to keep the initial connection time under control with new
31831 versions of @value{GDBN} which support increasing numbers of packets.
31835 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
31836 The stub supports or does not support each returned @var{stubfeature},
31837 depending on the form of each @var{stubfeature} (see below for the
31840 An empty reply indicates that @samp{qSupported} is not recognized,
31841 or that no features needed to be reported to @value{GDBN}.
31844 The allowed forms for each feature (either a @var{gdbfeature} in the
31845 @samp{qSupported} packet, or a @var{stubfeature} in the response)
31849 @item @var{name}=@var{value}
31850 The remote protocol feature @var{name} is supported, and associated
31851 with the specified @var{value}. The format of @var{value} depends
31852 on the feature, but it must not include a semicolon.
31854 The remote protocol feature @var{name} is supported, and does not
31855 need an associated value.
31857 The remote protocol feature @var{name} is not supported.
31859 The remote protocol feature @var{name} may be supported, and
31860 @value{GDBN} should auto-detect support in some other way when it is
31861 needed. This form will not be used for @var{gdbfeature} notifications,
31862 but may be used for @var{stubfeature} responses.
31865 Whenever the stub receives a @samp{qSupported} request, the
31866 supplied set of @value{GDBN} features should override any previous
31867 request. This allows @value{GDBN} to put the stub in a known
31868 state, even if the stub had previously been communicating with
31869 a different version of @value{GDBN}.
31871 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
31876 This feature indicates whether @value{GDBN} supports multiprocess
31877 extensions to the remote protocol. @value{GDBN} does not use such
31878 extensions unless the stub also reports that it supports them by
31879 including @samp{multiprocess+} in its @samp{qSupported} reply.
31880 @xref{multiprocess extensions}, for details.
31883 This feature indicates that @value{GDBN} supports the XML target
31884 description. If the stub sees @samp{xmlRegisters=} with target
31885 specific strings separated by a comma, it will report register
31889 This feature indicates whether @value{GDBN} supports the
31890 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
31891 instruction reply packet}).
31894 Stubs should ignore any unknown values for
31895 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31896 packet supports receiving packets of unlimited length (earlier
31897 versions of @value{GDBN} may reject overly long responses). Additional values
31898 for @var{gdbfeature} may be defined in the future to let the stub take
31899 advantage of new features in @value{GDBN}, e.g.@: incompatible
31900 improvements in the remote protocol---the @samp{multiprocess} feature is
31901 an example of such a feature. The stub's reply should be independent
31902 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31903 describes all the features it supports, and then the stub replies with
31904 all the features it supports.
31906 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31907 responses, as long as each response uses one of the standard forms.
31909 Some features are flags. A stub which supports a flag feature
31910 should respond with a @samp{+} form response. Other features
31911 require values, and the stub should respond with an @samp{=}
31914 Each feature has a default value, which @value{GDBN} will use if
31915 @samp{qSupported} is not available or if the feature is not mentioned
31916 in the @samp{qSupported} response. The default values are fixed; a
31917 stub is free to omit any feature responses that match the defaults.
31919 Not all features can be probed, but for those which can, the probing
31920 mechanism is useful: in some cases, a stub's internal
31921 architecture may not allow the protocol layer to know some information
31922 about the underlying target in advance. This is especially common in
31923 stubs which may be configured for multiple targets.
31925 These are the currently defined stub features and their properties:
31927 @multitable @columnfractions 0.35 0.2 0.12 0.2
31928 @c NOTE: The first row should be @headitem, but we do not yet require
31929 @c a new enough version of Texinfo (4.7) to use @headitem.
31931 @tab Value Required
31935 @item @samp{PacketSize}
31940 @item @samp{qXfer:auxv:read}
31945 @item @samp{qXfer:features:read}
31950 @item @samp{qXfer:libraries:read}
31955 @item @samp{qXfer:memory-map:read}
31960 @item @samp{qXfer:spu:read}
31965 @item @samp{qXfer:spu:write}
31970 @item @samp{qXfer:siginfo:read}
31975 @item @samp{qXfer:siginfo:write}
31980 @item @samp{qXfer:threads:read}
31986 @item @samp{QNonStop}
31991 @item @samp{QPassSignals}
31996 @item @samp{QStartNoAckMode}
32001 @item @samp{multiprocess}
32006 @item @samp{ConditionalTracepoints}
32011 @item @samp{ReverseContinue}
32016 @item @samp{ReverseStep}
32021 @item @samp{TracepointSource}
32026 @item @samp{QAllow}
32033 These are the currently defined stub features, in more detail:
32036 @cindex packet size, remote protocol
32037 @item PacketSize=@var{bytes}
32038 The remote stub can accept packets up to at least @var{bytes} in
32039 length. @value{GDBN} will send packets up to this size for bulk
32040 transfers, and will never send larger packets. This is a limit on the
32041 data characters in the packet, including the frame and checksum.
32042 There is no trailing NUL byte in a remote protocol packet; if the stub
32043 stores packets in a NUL-terminated format, it should allow an extra
32044 byte in its buffer for the NUL. If this stub feature is not supported,
32045 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32047 @item qXfer:auxv:read
32048 The remote stub understands the @samp{qXfer:auxv:read} packet
32049 (@pxref{qXfer auxiliary vector read}).
32051 @item qXfer:features:read
32052 The remote stub understands the @samp{qXfer:features:read} packet
32053 (@pxref{qXfer target description read}).
32055 @item qXfer:libraries:read
32056 The remote stub understands the @samp{qXfer:libraries:read} packet
32057 (@pxref{qXfer library list read}).
32059 @item qXfer:memory-map:read
32060 The remote stub understands the @samp{qXfer:memory-map:read} packet
32061 (@pxref{qXfer memory map read}).
32063 @item qXfer:spu:read
32064 The remote stub understands the @samp{qXfer:spu:read} packet
32065 (@pxref{qXfer spu read}).
32067 @item qXfer:spu:write
32068 The remote stub understands the @samp{qXfer:spu:write} packet
32069 (@pxref{qXfer spu write}).
32071 @item qXfer:siginfo:read
32072 The remote stub understands the @samp{qXfer:siginfo:read} packet
32073 (@pxref{qXfer siginfo read}).
32075 @item qXfer:siginfo:write
32076 The remote stub understands the @samp{qXfer:siginfo:write} packet
32077 (@pxref{qXfer siginfo write}).
32079 @item qXfer:threads:read
32080 The remote stub understands the @samp{qXfer:threads:read} packet
32081 (@pxref{qXfer threads read}).
32084 The remote stub understands the @samp{QNonStop} packet
32085 (@pxref{QNonStop}).
32088 The remote stub understands the @samp{QPassSignals} packet
32089 (@pxref{QPassSignals}).
32091 @item QStartNoAckMode
32092 The remote stub understands the @samp{QStartNoAckMode} packet and
32093 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32096 @anchor{multiprocess extensions}
32097 @cindex multiprocess extensions, in remote protocol
32098 The remote stub understands the multiprocess extensions to the remote
32099 protocol syntax. The multiprocess extensions affect the syntax of
32100 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32101 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32102 replies. Note that reporting this feature indicates support for the
32103 syntactic extensions only, not that the stub necessarily supports
32104 debugging of more than one process at a time. The stub must not use
32105 multiprocess extensions in packet replies unless @value{GDBN} has also
32106 indicated it supports them in its @samp{qSupported} request.
32108 @item qXfer:osdata:read
32109 The remote stub understands the @samp{qXfer:osdata:read} packet
32110 ((@pxref{qXfer osdata read}).
32112 @item ConditionalTracepoints
32113 The remote stub accepts and implements conditional expressions defined
32114 for tracepoints (@pxref{Tracepoint Conditions}).
32116 @item ReverseContinue
32117 The remote stub accepts and implements the reverse continue packet
32121 The remote stub accepts and implements the reverse step packet
32124 @item TracepointSource
32125 The remote stub understands the @samp{QTDPsrc} packet that supplies
32126 the source form of tracepoint definitions.
32129 The remote stub understands the @samp{QAllow} packet.
32134 @cindex symbol lookup, remote request
32135 @cindex @samp{qSymbol} packet
32136 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32137 requests. Accept requests from the target for the values of symbols.
32142 The target does not need to look up any (more) symbols.
32143 @item qSymbol:@var{sym_name}
32144 The target requests the value of symbol @var{sym_name} (hex encoded).
32145 @value{GDBN} may provide the value by using the
32146 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32150 @item qSymbol:@var{sym_value}:@var{sym_name}
32151 Set the value of @var{sym_name} to @var{sym_value}.
32153 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32154 target has previously requested.
32156 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32157 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32163 The target does not need to look up any (more) symbols.
32164 @item qSymbol:@var{sym_name}
32165 The target requests the value of a new symbol @var{sym_name} (hex
32166 encoded). @value{GDBN} will continue to supply the values of symbols
32167 (if available), until the target ceases to request them.
32172 @item QTDisconnected
32179 @xref{Tracepoint Packets}.
32181 @item qThreadExtraInfo,@var{thread-id}
32182 @cindex thread attributes info, remote request
32183 @cindex @samp{qThreadExtraInfo} packet
32184 Obtain a printable string description of a thread's attributes from
32185 the target OS. @var{thread-id} is a thread ID;
32186 see @ref{thread-id syntax}. This
32187 string may contain anything that the target OS thinks is interesting
32188 for @value{GDBN} to tell the user about the thread. The string is
32189 displayed in @value{GDBN}'s @code{info threads} display. Some
32190 examples of possible thread extra info strings are @samp{Runnable}, or
32191 @samp{Blocked on Mutex}.
32195 @item @var{XX}@dots{}
32196 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32197 comprising the printable string containing the extra information about
32198 the thread's attributes.
32201 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32202 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32203 conventions above. Please don't use this packet as a model for new
32215 @xref{Tracepoint Packets}.
32217 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32218 @cindex read special object, remote request
32219 @cindex @samp{qXfer} packet
32220 @anchor{qXfer read}
32221 Read uninterpreted bytes from the target's special data area
32222 identified by the keyword @var{object}. Request @var{length} bytes
32223 starting at @var{offset} bytes into the data. The content and
32224 encoding of @var{annex} is specific to @var{object}; it can supply
32225 additional details about what data to access.
32227 Here are the specific requests of this form defined so far. All
32228 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32229 formats, listed below.
32232 @item qXfer:auxv:read::@var{offset},@var{length}
32233 @anchor{qXfer auxiliary vector read}
32234 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32235 auxiliary vector}. Note @var{annex} must be empty.
32237 This packet is not probed by default; the remote stub must request it,
32238 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32240 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32241 @anchor{qXfer target description read}
32242 Access the @dfn{target description}. @xref{Target Descriptions}. The
32243 annex specifies which XML document to access. The main description is
32244 always loaded from the @samp{target.xml} annex.
32246 This packet is not probed by default; the remote stub must request it,
32247 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32249 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32250 @anchor{qXfer library list read}
32251 Access the target's list of loaded libraries. @xref{Library List Format}.
32252 The annex part of the generic @samp{qXfer} packet must be empty
32253 (@pxref{qXfer read}).
32255 Targets which maintain a list of libraries in the program's memory do
32256 not need to implement this packet; it is designed for platforms where
32257 the operating system manages the list of loaded libraries.
32259 This packet is not probed by default; the remote stub must request it,
32260 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32262 @item qXfer:memory-map:read::@var{offset},@var{length}
32263 @anchor{qXfer memory map read}
32264 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32265 annex part of the generic @samp{qXfer} packet must be empty
32266 (@pxref{qXfer read}).
32268 This packet is not probed by default; the remote stub must request it,
32269 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32271 @item qXfer:siginfo:read::@var{offset},@var{length}
32272 @anchor{qXfer siginfo read}
32273 Read contents of the extra signal information on the target
32274 system. The annex part of the generic @samp{qXfer} packet must be
32275 empty (@pxref{qXfer read}).
32277 This packet is not probed by default; the remote stub must request it,
32278 by supplying an appropriate @samp{qSupported} response
32279 (@pxref{qSupported}).
32281 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32282 @anchor{qXfer spu read}
32283 Read contents of an @code{spufs} file on the target system. The
32284 annex specifies which file to read; it must be of the form
32285 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32286 in the target process, and @var{name} identifes the @code{spufs} file
32287 in that context to be accessed.
32289 This packet is not probed by default; the remote stub must request it,
32290 by supplying an appropriate @samp{qSupported} response
32291 (@pxref{qSupported}).
32293 @item qXfer:threads:read::@var{offset},@var{length}
32294 @anchor{qXfer threads read}
32295 Access the list of threads on target. @xref{Thread List Format}. The
32296 annex part of the generic @samp{qXfer} packet must be empty
32297 (@pxref{qXfer read}).
32299 This packet is not probed by default; the remote stub must request it,
32300 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32302 @item qXfer:osdata:read::@var{offset},@var{length}
32303 @anchor{qXfer osdata read}
32304 Access the target's @dfn{operating system information}.
32305 @xref{Operating System Information}.
32312 Data @var{data} (@pxref{Binary Data}) has been read from the
32313 target. There may be more data at a higher address (although
32314 it is permitted to return @samp{m} even for the last valid
32315 block of data, as long as at least one byte of data was read).
32316 @var{data} may have fewer bytes than the @var{length} in the
32320 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32321 There is no more data to be read. @var{data} may have fewer bytes
32322 than the @var{length} in the request.
32325 The @var{offset} in the request is at the end of the data.
32326 There is no more data to be read.
32329 The request was malformed, or @var{annex} was invalid.
32332 The offset was invalid, or there was an error encountered reading the data.
32333 @var{nn} is a hex-encoded @code{errno} value.
32336 An empty reply indicates the @var{object} string was not recognized by
32337 the stub, or that the object does not support reading.
32340 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32341 @cindex write data into object, remote request
32342 @anchor{qXfer write}
32343 Write uninterpreted bytes into the target's special data area
32344 identified by the keyword @var{object}, starting at @var{offset} bytes
32345 into the data. @var{data}@dots{} is the binary-encoded data
32346 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32347 is specific to @var{object}; it can supply additional details about what data
32350 Here are the specific requests of this form defined so far. All
32351 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32352 formats, listed below.
32355 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32356 @anchor{qXfer siginfo write}
32357 Write @var{data} to the extra signal information on the target system.
32358 The annex part of the generic @samp{qXfer} packet must be
32359 empty (@pxref{qXfer write}).
32361 This packet is not probed by default; the remote stub must request it,
32362 by supplying an appropriate @samp{qSupported} response
32363 (@pxref{qSupported}).
32365 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32366 @anchor{qXfer spu write}
32367 Write @var{data} to an @code{spufs} file on the target system. The
32368 annex specifies which file to write; it must be of the form
32369 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32370 in the target process, and @var{name} identifes the @code{spufs} file
32371 in that context to be accessed.
32373 This packet is not probed by default; the remote stub must request it,
32374 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32380 @var{nn} (hex encoded) is the number of bytes written.
32381 This may be fewer bytes than supplied in the request.
32384 The request was malformed, or @var{annex} was invalid.
32387 The offset was invalid, or there was an error encountered writing the data.
32388 @var{nn} is a hex-encoded @code{errno} value.
32391 An empty reply indicates the @var{object} string was not
32392 recognized by the stub, or that the object does not support writing.
32395 @item qXfer:@var{object}:@var{operation}:@dots{}
32396 Requests of this form may be added in the future. When a stub does
32397 not recognize the @var{object} keyword, or its support for
32398 @var{object} does not recognize the @var{operation} keyword, the stub
32399 must respond with an empty packet.
32401 @item qAttached:@var{pid}
32402 @cindex query attached, remote request
32403 @cindex @samp{qAttached} packet
32404 Return an indication of whether the remote server attached to an
32405 existing process or created a new process. When the multiprocess
32406 protocol extensions are supported (@pxref{multiprocess extensions}),
32407 @var{pid} is an integer in hexadecimal format identifying the target
32408 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32409 the query packet will be simplified as @samp{qAttached}.
32411 This query is used, for example, to know whether the remote process
32412 should be detached or killed when a @value{GDBN} session is ended with
32413 the @code{quit} command.
32418 The remote server attached to an existing process.
32420 The remote server created a new process.
32422 A badly formed request or an error was encountered.
32427 @node Architecture-Specific Protocol Details
32428 @section Architecture-Specific Protocol Details
32430 This section describes how the remote protocol is applied to specific
32431 target architectures. Also see @ref{Standard Target Features}, for
32432 details of XML target descriptions for each architecture.
32436 @subsubsection Breakpoint Kinds
32438 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32443 16-bit Thumb mode breakpoint.
32446 32-bit Thumb mode (Thumb-2) breakpoint.
32449 32-bit ARM mode breakpoint.
32455 @subsubsection Register Packet Format
32457 The following @code{g}/@code{G} packets have previously been defined.
32458 In the below, some thirty-two bit registers are transferred as
32459 sixty-four bits. Those registers should be zero/sign extended (which?)
32460 to fill the space allocated. Register bytes are transferred in target
32461 byte order. The two nibbles within a register byte are transferred
32462 most-significant - least-significant.
32468 All registers are transferred as thirty-two bit quantities in the order:
32469 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32470 registers; fsr; fir; fp.
32474 All registers are transferred as sixty-four bit quantities (including
32475 thirty-two bit registers such as @code{sr}). The ordering is the same
32480 @node Tracepoint Packets
32481 @section Tracepoint Packets
32482 @cindex tracepoint packets
32483 @cindex packets, tracepoint
32485 Here we describe the packets @value{GDBN} uses to implement
32486 tracepoints (@pxref{Tracepoints}).
32490 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32491 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32492 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32493 the tracepoint is disabled. @var{step} is the tracepoint's step
32494 count, and @var{pass} is its pass count. If an @samp{F} is present,
32495 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32496 the number of bytes that the target should copy elsewhere to make room
32497 for the tracepoint. If an @samp{X} is present, it introduces a
32498 tracepoint condition, which consists of a hexadecimal length, followed
32499 by a comma and hex-encoded bytes, in a manner similar to action
32500 encodings as described below. If the trailing @samp{-} is present,
32501 further @samp{QTDP} packets will follow to specify this tracepoint's
32507 The packet was understood and carried out.
32509 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32511 The packet was not recognized.
32514 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32515 Define actions to be taken when a tracepoint is hit. @var{n} and
32516 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32517 this tracepoint. This packet may only be sent immediately after
32518 another @samp{QTDP} packet that ended with a @samp{-}. If the
32519 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32520 specifying more actions for this tracepoint.
32522 In the series of action packets for a given tracepoint, at most one
32523 can have an @samp{S} before its first @var{action}. If such a packet
32524 is sent, it and the following packets define ``while-stepping''
32525 actions. Any prior packets define ordinary actions --- that is, those
32526 taken when the tracepoint is first hit. If no action packet has an
32527 @samp{S}, then all the packets in the series specify ordinary
32528 tracepoint actions.
32530 The @samp{@var{action}@dots{}} portion of the packet is a series of
32531 actions, concatenated without separators. Each action has one of the
32537 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32538 a hexadecimal number whose @var{i}'th bit is set if register number
32539 @var{i} should be collected. (The least significant bit is numbered
32540 zero.) Note that @var{mask} may be any number of digits long; it may
32541 not fit in a 32-bit word.
32543 @item M @var{basereg},@var{offset},@var{len}
32544 Collect @var{len} bytes of memory starting at the address in register
32545 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32546 @samp{-1}, then the range has a fixed address: @var{offset} is the
32547 address of the lowest byte to collect. The @var{basereg},
32548 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32549 values (the @samp{-1} value for @var{basereg} is a special case).
32551 @item X @var{len},@var{expr}
32552 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32553 it directs. @var{expr} is an agent expression, as described in
32554 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32555 two-digit hex number in the packet; @var{len} is the number of bytes
32556 in the expression (and thus one-half the number of hex digits in the
32561 Any number of actions may be packed together in a single @samp{QTDP}
32562 packet, as long as the packet does not exceed the maximum packet
32563 length (400 bytes, for many stubs). There may be only one @samp{R}
32564 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32565 actions. Any registers referred to by @samp{M} and @samp{X} actions
32566 must be collected by a preceding @samp{R} action. (The
32567 ``while-stepping'' actions are treated as if they were attached to a
32568 separate tracepoint, as far as these restrictions are concerned.)
32573 The packet was understood and carried out.
32575 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32577 The packet was not recognized.
32580 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32581 @cindex @samp{QTDPsrc} packet
32582 Specify a source string of tracepoint @var{n} at address @var{addr}.
32583 This is useful to get accurate reproduction of the tracepoints
32584 originally downloaded at the beginning of the trace run. @var{type}
32585 is the name of the tracepoint part, such as @samp{cond} for the
32586 tracepoint's conditional expression (see below for a list of types), while
32587 @var{bytes} is the string, encoded in hexadecimal.
32589 @var{start} is the offset of the @var{bytes} within the overall source
32590 string, while @var{slen} is the total length of the source string.
32591 This is intended for handling source strings that are longer than will
32592 fit in a single packet.
32593 @c Add detailed example when this info is moved into a dedicated
32594 @c tracepoint descriptions section.
32596 The available string types are @samp{at} for the location,
32597 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32598 @value{GDBN} sends a separate packet for each command in the action
32599 list, in the same order in which the commands are stored in the list.
32601 The target does not need to do anything with source strings except
32602 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32605 Although this packet is optional, and @value{GDBN} will only send it
32606 if the target replies with @samp{TracepointSource} @xref{General
32607 Query Packets}, it makes both disconnected tracing and trace files
32608 much easier to use. Otherwise the user must be careful that the
32609 tracepoints in effect while looking at trace frames are identical to
32610 the ones in effect during the trace run; even a small discrepancy
32611 could cause @samp{tdump} not to work, or a particular trace frame not
32614 @item QTDV:@var{n}:@var{value}
32615 @cindex define trace state variable, remote request
32616 @cindex @samp{QTDV} packet
32617 Create a new trace state variable, number @var{n}, with an initial
32618 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32619 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32620 the option of not using this packet for initial values of zero; the
32621 target should simply create the trace state variables as they are
32622 mentioned in expressions.
32624 @item QTFrame:@var{n}
32625 Select the @var{n}'th tracepoint frame from the buffer, and use the
32626 register and memory contents recorded there to answer subsequent
32627 request packets from @value{GDBN}.
32629 A successful reply from the stub indicates that the stub has found the
32630 requested frame. The response is a series of parts, concatenated
32631 without separators, describing the frame we selected. Each part has
32632 one of the following forms:
32636 The selected frame is number @var{n} in the trace frame buffer;
32637 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32638 was no frame matching the criteria in the request packet.
32641 The selected trace frame records a hit of tracepoint number @var{t};
32642 @var{t} is a hexadecimal number.
32646 @item QTFrame:pc:@var{addr}
32647 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32648 currently selected frame whose PC is @var{addr};
32649 @var{addr} is a hexadecimal number.
32651 @item QTFrame:tdp:@var{t}
32652 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32653 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32654 is a hexadecimal number.
32656 @item QTFrame:range:@var{start}:@var{end}
32657 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32658 currently selected frame whose PC is between @var{start} (inclusive)
32659 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32662 @item QTFrame:outside:@var{start}:@var{end}
32663 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32664 frame @emph{outside} the given range of addresses (exclusive).
32667 Begin the tracepoint experiment. Begin collecting data from
32668 tracepoint hits in the trace frame buffer. This packet supports the
32669 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32670 instruction reply packet}).
32673 End the tracepoint experiment. Stop collecting trace frames.
32676 Clear the table of tracepoints, and empty the trace frame buffer.
32678 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32679 Establish the given ranges of memory as ``transparent''. The stub
32680 will answer requests for these ranges from memory's current contents,
32681 if they were not collected as part of the tracepoint hit.
32683 @value{GDBN} uses this to mark read-only regions of memory, like those
32684 containing program code. Since these areas never change, they should
32685 still have the same contents they did when the tracepoint was hit, so
32686 there's no reason for the stub to refuse to provide their contents.
32688 @item QTDisconnected:@var{value}
32689 Set the choice to what to do with the tracing run when @value{GDBN}
32690 disconnects from the target. A @var{value} of 1 directs the target to
32691 continue the tracing run, while 0 tells the target to stop tracing if
32692 @value{GDBN} is no longer in the picture.
32695 Ask the stub if there is a trace experiment running right now.
32697 The reply has the form:
32701 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32702 @var{running} is a single digit @code{1} if the trace is presently
32703 running, or @code{0} if not. It is followed by semicolon-separated
32704 optional fields that an agent may use to report additional status.
32708 If the trace is not running, the agent may report any of several
32709 explanations as one of the optional fields:
32714 No trace has been run yet.
32717 The trace was stopped by a user-originated stop command.
32720 The trace stopped because the trace buffer filled up.
32722 @item tdisconnected:0
32723 The trace stopped because @value{GDBN} disconnected from the target.
32725 @item tpasscount:@var{tpnum}
32726 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32728 @item terror:@var{text}:@var{tpnum}
32729 The trace stopped because tracepoint @var{tpnum} had an error. The
32730 string @var{text} is available to describe the nature of the error
32731 (for instance, a divide by zero in the condition expression).
32732 @var{text} is hex encoded.
32735 The trace stopped for some other reason.
32739 Additional optional fields supply statistical and other information.
32740 Although not required, they are extremely useful for users monitoring
32741 the progress of a trace run. If a trace has stopped, and these
32742 numbers are reported, they must reflect the state of the just-stopped
32747 @item tframes:@var{n}
32748 The number of trace frames in the buffer.
32750 @item tcreated:@var{n}
32751 The total number of trace frames created during the run. This may
32752 be larger than the trace frame count, if the buffer is circular.
32754 @item tsize:@var{n}
32755 The total size of the trace buffer, in bytes.
32757 @item tfree:@var{n}
32758 The number of bytes still unused in the buffer.
32760 @item circular:@var{n}
32761 The value of the circular trace buffer flag. @code{1} means that the
32762 trace buffer is circular and old trace frames will be discarded if
32763 necessary to make room, @code{0} means that the trace buffer is linear
32766 @item disconn:@var{n}
32767 The value of the disconnected tracing flag. @code{1} means that
32768 tracing will continue after @value{GDBN} disconnects, @code{0} means
32769 that the trace run will stop.
32773 @item qTV:@var{var}
32774 @cindex trace state variable value, remote request
32775 @cindex @samp{qTV} packet
32776 Ask the stub for the value of the trace state variable number @var{var}.
32781 The value of the variable is @var{value}. This will be the current
32782 value of the variable if the user is examining a running target, or a
32783 saved value if the variable was collected in the trace frame that the
32784 user is looking at. Note that multiple requests may result in
32785 different reply values, such as when requesting values while the
32786 program is running.
32789 The value of the variable is unknown. This would occur, for example,
32790 if the user is examining a trace frame in which the requested variable
32796 These packets request data about tracepoints that are being used by
32797 the target. @value{GDBN} sends @code{qTfP} to get the first piece
32798 of data, and multiple @code{qTsP} to get additional pieces. Replies
32799 to these packets generally take the form of the @code{QTDP} packets
32800 that define tracepoints. (FIXME add detailed syntax)
32804 These packets request data about trace state variables that are on the
32805 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
32806 and multiple @code{qTsV} to get additional variables. Replies to
32807 these packets follow the syntax of the @code{QTDV} packets that define
32808 trace state variables.
32810 @item QTSave:@var{filename}
32811 This packet directs the target to save trace data to the file name
32812 @var{filename} in the target's filesystem. @var{filename} is encoded
32813 as a hex string; the interpretation of the file name (relative vs
32814 absolute, wild cards, etc) is up to the target.
32816 @item qTBuffer:@var{offset},@var{len}
32817 Return up to @var{len} bytes of the current contents of trace buffer,
32818 starting at @var{offset}. The trace buffer is treated as if it were
32819 a contiguous collection of traceframes, as per the trace file format.
32820 The reply consists as many hex-encoded bytes as the target can deliver
32821 in a packet; it is not an error to return fewer than were asked for.
32822 A reply consisting of just @code{l} indicates that no bytes are
32825 @item QTBuffer:circular:@var{value}
32826 This packet directs the target to use a circular trace buffer if
32827 @var{value} is 1, or a linear buffer if the value is 0.
32831 @subsection Relocate instruction reply packet
32832 When installing fast tracepoints in memory, the target may need to
32833 relocate the instruction currently at the tracepoint address to a
32834 different address in memory. For most instructions, a simple copy is
32835 enough, but, for example, call instructions that implicitly push the
32836 return address on the stack, and relative branches or other
32837 PC-relative instructions require offset adjustment, so that the effect
32838 of executing the instruction at a different address is the same as if
32839 it had executed in the original location.
32841 In response to several of the tracepoint packets, the target may also
32842 respond with a number of intermediate @samp{qRelocInsn} request
32843 packets before the final result packet, to have @value{GDBN} handle
32844 this relocation operation. If a packet supports this mechanism, its
32845 documentation will explicitly say so. See for example the above
32846 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
32847 format of the request is:
32850 @item qRelocInsn:@var{from};@var{to}
32852 This requests @value{GDBN} to copy instruction at address @var{from}
32853 to address @var{to}, possibly adjusted so that executing the
32854 instruction at @var{to} has the same effect as executing it at
32855 @var{from}. @value{GDBN} writes the adjusted instruction to target
32856 memory starting at @var{to}.
32861 @item qRelocInsn:@var{adjusted_size}
32862 Informs the stub the relocation is complete. @var{adjusted_size} is
32863 the length in bytes of resulting relocated instruction sequence.
32865 A badly formed request was detected, or an error was encountered while
32866 relocating the instruction.
32869 @node Host I/O Packets
32870 @section Host I/O Packets
32871 @cindex Host I/O, remote protocol
32872 @cindex file transfer, remote protocol
32874 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
32875 operations on the far side of a remote link. For example, Host I/O is
32876 used to upload and download files to a remote target with its own
32877 filesystem. Host I/O uses the same constant values and data structure
32878 layout as the target-initiated File-I/O protocol. However, the
32879 Host I/O packets are structured differently. The target-initiated
32880 protocol relies on target memory to store parameters and buffers.
32881 Host I/O requests are initiated by @value{GDBN}, and the
32882 target's memory is not involved. @xref{File-I/O Remote Protocol
32883 Extension}, for more details on the target-initiated protocol.
32885 The Host I/O request packets all encode a single operation along with
32886 its arguments. They have this format:
32890 @item vFile:@var{operation}: @var{parameter}@dots{}
32891 @var{operation} is the name of the particular request; the target
32892 should compare the entire packet name up to the second colon when checking
32893 for a supported operation. The format of @var{parameter} depends on
32894 the operation. Numbers are always passed in hexadecimal. Negative
32895 numbers have an explicit minus sign (i.e.@: two's complement is not
32896 used). Strings (e.g.@: filenames) are encoded as a series of
32897 hexadecimal bytes. The last argument to a system call may be a
32898 buffer of escaped binary data (@pxref{Binary Data}).
32902 The valid responses to Host I/O packets are:
32906 @item F @var{result} [, @var{errno}] [; @var{attachment}]
32907 @var{result} is the integer value returned by this operation, usually
32908 non-negative for success and -1 for errors. If an error has occured,
32909 @var{errno} will be included in the result. @var{errno} will have a
32910 value defined by the File-I/O protocol (@pxref{Errno Values}). For
32911 operations which return data, @var{attachment} supplies the data as a
32912 binary buffer. Binary buffers in response packets are escaped in the
32913 normal way (@pxref{Binary Data}). See the individual packet
32914 documentation for the interpretation of @var{result} and
32918 An empty response indicates that this operation is not recognized.
32922 These are the supported Host I/O operations:
32925 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
32926 Open a file at @var{pathname} and return a file descriptor for it, or
32927 return -1 if an error occurs. @var{pathname} is a string,
32928 @var{flags} is an integer indicating a mask of open flags
32929 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
32930 of mode bits to use if the file is created (@pxref{mode_t Values}).
32931 @xref{open}, for details of the open flags and mode values.
32933 @item vFile:close: @var{fd}
32934 Close the open file corresponding to @var{fd} and return 0, or
32935 -1 if an error occurs.
32937 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
32938 Read data from the open file corresponding to @var{fd}. Up to
32939 @var{count} bytes will be read from the file, starting at @var{offset}
32940 relative to the start of the file. The target may read fewer bytes;
32941 common reasons include packet size limits and an end-of-file
32942 condition. The number of bytes read is returned. Zero should only be
32943 returned for a successful read at the end of the file, or if
32944 @var{count} was zero.
32946 The data read should be returned as a binary attachment on success.
32947 If zero bytes were read, the response should include an empty binary
32948 attachment (i.e.@: a trailing semicolon). The return value is the
32949 number of target bytes read; the binary attachment may be longer if
32950 some characters were escaped.
32952 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32953 Write @var{data} (a binary buffer) to the open file corresponding
32954 to @var{fd}. Start the write at @var{offset} from the start of the
32955 file. Unlike many @code{write} system calls, there is no
32956 separate @var{count} argument; the length of @var{data} in the
32957 packet is used. @samp{vFile:write} returns the number of bytes written,
32958 which may be shorter than the length of @var{data}, or -1 if an
32961 @item vFile:unlink: @var{pathname}
32962 Delete the file at @var{pathname} on the target. Return 0,
32963 or -1 if an error occurs. @var{pathname} is a string.
32968 @section Interrupts
32969 @cindex interrupts (remote protocol)
32971 When a program on the remote target is running, @value{GDBN} may
32972 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32973 a @code{BREAK} followed by @code{g},
32974 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32976 The precise meaning of @code{BREAK} is defined by the transport
32977 mechanism and may, in fact, be undefined. @value{GDBN} does not
32978 currently define a @code{BREAK} mechanism for any of the network
32979 interfaces except for TCP, in which case @value{GDBN} sends the
32980 @code{telnet} BREAK sequence.
32982 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32983 transport mechanisms. It is represented by sending the single byte
32984 @code{0x03} without any of the usual packet overhead described in
32985 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32986 transmitted as part of a packet, it is considered to be packet data
32987 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32988 (@pxref{X packet}), used for binary downloads, may include an unescaped
32989 @code{0x03} as part of its packet.
32991 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32992 When Linux kernel receives this sequence from serial port,
32993 it stops execution and connects to gdb.
32995 Stubs are not required to recognize these interrupt mechanisms and the
32996 precise meaning associated with receipt of the interrupt is
32997 implementation defined. If the target supports debugging of multiple
32998 threads and/or processes, it should attempt to interrupt all
32999 currently-executing threads and processes.
33000 If the stub is successful at interrupting the
33001 running program, it should send one of the stop
33002 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33003 of successfully stopping the program in all-stop mode, and a stop reply
33004 for each stopped thread in non-stop mode.
33005 Interrupts received while the
33006 program is stopped are discarded.
33008 @node Notification Packets
33009 @section Notification Packets
33010 @cindex notification packets
33011 @cindex packets, notification
33013 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33014 packets that require no acknowledgment. Both the GDB and the stub
33015 may send notifications (although the only notifications defined at
33016 present are sent by the stub). Notifications carry information
33017 without incurring the round-trip latency of an acknowledgment, and so
33018 are useful for low-impact communications where occasional packet loss
33021 A notification packet has the form @samp{% @var{data} #
33022 @var{checksum}}, where @var{data} is the content of the notification,
33023 and @var{checksum} is a checksum of @var{data}, computed and formatted
33024 as for ordinary @value{GDBN} packets. A notification's @var{data}
33025 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33026 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33027 to acknowledge the notification's receipt or to report its corruption.
33029 Every notification's @var{data} begins with a name, which contains no
33030 colon characters, followed by a colon character.
33032 Recipients should silently ignore corrupted notifications and
33033 notifications they do not understand. Recipients should restart
33034 timeout periods on receipt of a well-formed notification, whether or
33035 not they understand it.
33037 Senders should only send the notifications described here when this
33038 protocol description specifies that they are permitted. In the
33039 future, we may extend the protocol to permit existing notifications in
33040 new contexts; this rule helps older senders avoid confusing newer
33043 (Older versions of @value{GDBN} ignore bytes received until they see
33044 the @samp{$} byte that begins an ordinary packet, so new stubs may
33045 transmit notifications without fear of confusing older clients. There
33046 are no notifications defined for @value{GDBN} to send at the moment, but we
33047 assume that most older stubs would ignore them, as well.)
33049 The following notification packets from the stub to @value{GDBN} are
33053 @item Stop: @var{reply}
33054 Report an asynchronous stop event in non-stop mode.
33055 The @var{reply} has the form of a stop reply, as
33056 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33057 for information on how these notifications are acknowledged by
33061 @node Remote Non-Stop
33062 @section Remote Protocol Support for Non-Stop Mode
33064 @value{GDBN}'s remote protocol supports non-stop debugging of
33065 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33066 supports non-stop mode, it should report that to @value{GDBN} by including
33067 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33069 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33070 establishing a new connection with the stub. Entering non-stop mode
33071 does not alter the state of any currently-running threads, but targets
33072 must stop all threads in any already-attached processes when entering
33073 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33074 probe the target state after a mode change.
33076 In non-stop mode, when an attached process encounters an event that
33077 would otherwise be reported with a stop reply, it uses the
33078 asynchronous notification mechanism (@pxref{Notification Packets}) to
33079 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33080 in all processes are stopped when a stop reply is sent, in non-stop
33081 mode only the thread reporting the stop event is stopped. That is,
33082 when reporting a @samp{S} or @samp{T} response to indicate completion
33083 of a step operation, hitting a breakpoint, or a fault, only the
33084 affected thread is stopped; any other still-running threads continue
33085 to run. When reporting a @samp{W} or @samp{X} response, all running
33086 threads belonging to other attached processes continue to run.
33088 Only one stop reply notification at a time may be pending; if
33089 additional stop events occur before @value{GDBN} has acknowledged the
33090 previous notification, they must be queued by the stub for later
33091 synchronous transmission in response to @samp{vStopped} packets from
33092 @value{GDBN}. Because the notification mechanism is unreliable,
33093 the stub is permitted to resend a stop reply notification
33094 if it believes @value{GDBN} may not have received it. @value{GDBN}
33095 ignores additional stop reply notifications received before it has
33096 finished processing a previous notification and the stub has completed
33097 sending any queued stop events.
33099 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33100 notification at any time. Specifically, they may appear when
33101 @value{GDBN} is not otherwise reading input from the stub, or when
33102 @value{GDBN} is expecting to read a normal synchronous response or a
33103 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33104 Notification packets are distinct from any other communication from
33105 the stub so there is no ambiguity.
33107 After receiving a stop reply notification, @value{GDBN} shall
33108 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33109 as a regular, synchronous request to the stub. Such acknowledgment
33110 is not required to happen immediately, as @value{GDBN} is permitted to
33111 send other, unrelated packets to the stub first, which the stub should
33114 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33115 stop events to report to @value{GDBN}, it shall respond by sending a
33116 normal stop reply response. @value{GDBN} shall then send another
33117 @samp{vStopped} packet to solicit further responses; again, it is
33118 permitted to send other, unrelated packets as well which the stub
33119 should process normally.
33121 If the stub receives a @samp{vStopped} packet and there are no
33122 additional stop events to report, the stub shall return an @samp{OK}
33123 response. At this point, if further stop events occur, the stub shall
33124 send a new stop reply notification, @value{GDBN} shall accept the
33125 notification, and the process shall be repeated.
33127 In non-stop mode, the target shall respond to the @samp{?} packet as
33128 follows. First, any incomplete stop reply notification/@samp{vStopped}
33129 sequence in progress is abandoned. The target must begin a new
33130 sequence reporting stop events for all stopped threads, whether or not
33131 it has previously reported those events to @value{GDBN}. The first
33132 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33133 subsequent stop replies are sent as responses to @samp{vStopped} packets
33134 using the mechanism described above. The target must not send
33135 asynchronous stop reply notifications until the sequence is complete.
33136 If all threads are running when the target receives the @samp{?} packet,
33137 or if the target is not attached to any process, it shall respond
33140 @node Packet Acknowledgment
33141 @section Packet Acknowledgment
33143 @cindex acknowledgment, for @value{GDBN} remote
33144 @cindex packet acknowledgment, for @value{GDBN} remote
33145 By default, when either the host or the target machine receives a packet,
33146 the first response expected is an acknowledgment: either @samp{+} (to indicate
33147 the package was received correctly) or @samp{-} (to request retransmission).
33148 This mechanism allows the @value{GDBN} remote protocol to operate over
33149 unreliable transport mechanisms, such as a serial line.
33151 In cases where the transport mechanism is itself reliable (such as a pipe or
33152 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33153 It may be desirable to disable them in that case to reduce communication
33154 overhead, or for other reasons. This can be accomplished by means of the
33155 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33157 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33158 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33159 and response format still includes the normal checksum, as described in
33160 @ref{Overview}, but the checksum may be ignored by the receiver.
33162 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33163 no-acknowledgment mode, it should report that to @value{GDBN}
33164 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33165 @pxref{qSupported}.
33166 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33167 disabled via the @code{set remote noack-packet off} command
33168 (@pxref{Remote Configuration}),
33169 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33170 Only then may the stub actually turn off packet acknowledgments.
33171 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33172 response, which can be safely ignored by the stub.
33174 Note that @code{set remote noack-packet} command only affects negotiation
33175 between @value{GDBN} and the stub when subsequent connections are made;
33176 it does not affect the protocol acknowledgment state for any current
33178 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33179 new connection is established,
33180 there is also no protocol request to re-enable the acknowledgments
33181 for the current connection, once disabled.
33186 Example sequence of a target being re-started. Notice how the restart
33187 does not get any direct output:
33192 @emph{target restarts}
33195 <- @code{T001:1234123412341234}
33199 Example sequence of a target being stepped by a single instruction:
33202 -> @code{G1445@dots{}}
33207 <- @code{T001:1234123412341234}
33211 <- @code{1455@dots{}}
33215 @node File-I/O Remote Protocol Extension
33216 @section File-I/O Remote Protocol Extension
33217 @cindex File-I/O remote protocol extension
33220 * File-I/O Overview::
33221 * Protocol Basics::
33222 * The F Request Packet::
33223 * The F Reply Packet::
33224 * The Ctrl-C Message::
33226 * List of Supported Calls::
33227 * Protocol-specific Representation of Datatypes::
33229 * File-I/O Examples::
33232 @node File-I/O Overview
33233 @subsection File-I/O Overview
33234 @cindex file-i/o overview
33236 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33237 target to use the host's file system and console I/O to perform various
33238 system calls. System calls on the target system are translated into a
33239 remote protocol packet to the host system, which then performs the needed
33240 actions and returns a response packet to the target system.
33241 This simulates file system operations even on targets that lack file systems.
33243 The protocol is defined to be independent of both the host and target systems.
33244 It uses its own internal representation of datatypes and values. Both
33245 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33246 translating the system-dependent value representations into the internal
33247 protocol representations when data is transmitted.
33249 The communication is synchronous. A system call is possible only when
33250 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33251 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33252 the target is stopped to allow deterministic access to the target's
33253 memory. Therefore File-I/O is not interruptible by target signals. On
33254 the other hand, it is possible to interrupt File-I/O by a user interrupt
33255 (@samp{Ctrl-C}) within @value{GDBN}.
33257 The target's request to perform a host system call does not finish
33258 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33259 after finishing the system call, the target returns to continuing the
33260 previous activity (continue, step). No additional continue or step
33261 request from @value{GDBN} is required.
33264 (@value{GDBP}) continue
33265 <- target requests 'system call X'
33266 target is stopped, @value{GDBN} executes system call
33267 -> @value{GDBN} returns result
33268 ... target continues, @value{GDBN} returns to wait for the target
33269 <- target hits breakpoint and sends a Txx packet
33272 The protocol only supports I/O on the console and to regular files on
33273 the host file system. Character or block special devices, pipes,
33274 named pipes, sockets or any other communication method on the host
33275 system are not supported by this protocol.
33277 File I/O is not supported in non-stop mode.
33279 @node Protocol Basics
33280 @subsection Protocol Basics
33281 @cindex protocol basics, file-i/o
33283 The File-I/O protocol uses the @code{F} packet as the request as well
33284 as reply packet. Since a File-I/O system call can only occur when
33285 @value{GDBN} is waiting for a response from the continuing or stepping target,
33286 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33287 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33288 This @code{F} packet contains all information needed to allow @value{GDBN}
33289 to call the appropriate host system call:
33293 A unique identifier for the requested system call.
33296 All parameters to the system call. Pointers are given as addresses
33297 in the target memory address space. Pointers to strings are given as
33298 pointer/length pair. Numerical values are given as they are.
33299 Numerical control flags are given in a protocol-specific representation.
33303 At this point, @value{GDBN} has to perform the following actions.
33307 If the parameters include pointer values to data needed as input to a
33308 system call, @value{GDBN} requests this data from the target with a
33309 standard @code{m} packet request. This additional communication has to be
33310 expected by the target implementation and is handled as any other @code{m}
33314 @value{GDBN} translates all value from protocol representation to host
33315 representation as needed. Datatypes are coerced into the host types.
33318 @value{GDBN} calls the system call.
33321 It then coerces datatypes back to protocol representation.
33324 If the system call is expected to return data in buffer space specified
33325 by pointer parameters to the call, the data is transmitted to the
33326 target using a @code{M} or @code{X} packet. This packet has to be expected
33327 by the target implementation and is handled as any other @code{M} or @code{X}
33332 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33333 necessary information for the target to continue. This at least contains
33340 @code{errno}, if has been changed by the system call.
33347 After having done the needed type and value coercion, the target continues
33348 the latest continue or step action.
33350 @node The F Request Packet
33351 @subsection The @code{F} Request Packet
33352 @cindex file-i/o request packet
33353 @cindex @code{F} request packet
33355 The @code{F} request packet has the following format:
33358 @item F@var{call-id},@var{parameter@dots{}}
33360 @var{call-id} is the identifier to indicate the host system call to be called.
33361 This is just the name of the function.
33363 @var{parameter@dots{}} are the parameters to the system call.
33364 Parameters are hexadecimal integer values, either the actual values in case
33365 of scalar datatypes, pointers to target buffer space in case of compound
33366 datatypes and unspecified memory areas, or pointer/length pairs in case
33367 of string parameters. These are appended to the @var{call-id} as a
33368 comma-delimited list. All values are transmitted in ASCII
33369 string representation, pointer/length pairs separated by a slash.
33375 @node The F Reply Packet
33376 @subsection The @code{F} Reply Packet
33377 @cindex file-i/o reply packet
33378 @cindex @code{F} reply packet
33380 The @code{F} reply packet has the following format:
33384 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33386 @var{retcode} is the return code of the system call as hexadecimal value.
33388 @var{errno} is the @code{errno} set by the call, in protocol-specific
33390 This parameter can be omitted if the call was successful.
33392 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33393 case, @var{errno} must be sent as well, even if the call was successful.
33394 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33401 or, if the call was interrupted before the host call has been performed:
33408 assuming 4 is the protocol-specific representation of @code{EINTR}.
33413 @node The Ctrl-C Message
33414 @subsection The @samp{Ctrl-C} Message
33415 @cindex ctrl-c message, in file-i/o protocol
33417 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33418 reply packet (@pxref{The F Reply Packet}),
33419 the target should behave as if it had
33420 gotten a break message. The meaning for the target is ``system call
33421 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33422 (as with a break message) and return to @value{GDBN} with a @code{T02}
33425 It's important for the target to know in which
33426 state the system call was interrupted. There are two possible cases:
33430 The system call hasn't been performed on the host yet.
33433 The system call on the host has been finished.
33437 These two states can be distinguished by the target by the value of the
33438 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33439 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33440 on POSIX systems. In any other case, the target may presume that the
33441 system call has been finished --- successfully or not --- and should behave
33442 as if the break message arrived right after the system call.
33444 @value{GDBN} must behave reliably. If the system call has not been called
33445 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33446 @code{errno} in the packet. If the system call on the host has been finished
33447 before the user requests a break, the full action must be finished by
33448 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33449 The @code{F} packet may only be sent when either nothing has happened
33450 or the full action has been completed.
33453 @subsection Console I/O
33454 @cindex console i/o as part of file-i/o
33456 By default and if not explicitly closed by the target system, the file
33457 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33458 on the @value{GDBN} console is handled as any other file output operation
33459 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33460 by @value{GDBN} so that after the target read request from file descriptor
33461 0 all following typing is buffered until either one of the following
33466 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33468 system call is treated as finished.
33471 The user presses @key{RET}. This is treated as end of input with a trailing
33475 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33476 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33480 If the user has typed more characters than fit in the buffer given to
33481 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33482 either another @code{read(0, @dots{})} is requested by the target, or debugging
33483 is stopped at the user's request.
33486 @node List of Supported Calls
33487 @subsection List of Supported Calls
33488 @cindex list of supported file-i/o calls
33505 @unnumberedsubsubsec open
33506 @cindex open, file-i/o system call
33511 int open(const char *pathname, int flags);
33512 int open(const char *pathname, int flags, mode_t mode);
33516 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33519 @var{flags} is the bitwise @code{OR} of the following values:
33523 If the file does not exist it will be created. The host
33524 rules apply as far as file ownership and time stamps
33528 When used with @code{O_CREAT}, if the file already exists it is
33529 an error and open() fails.
33532 If the file already exists and the open mode allows
33533 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33534 truncated to zero length.
33537 The file is opened in append mode.
33540 The file is opened for reading only.
33543 The file is opened for writing only.
33546 The file is opened for reading and writing.
33550 Other bits are silently ignored.
33554 @var{mode} is the bitwise @code{OR} of the following values:
33558 User has read permission.
33561 User has write permission.
33564 Group has read permission.
33567 Group has write permission.
33570 Others have read permission.
33573 Others have write permission.
33577 Other bits are silently ignored.
33580 @item Return value:
33581 @code{open} returns the new file descriptor or -1 if an error
33588 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33591 @var{pathname} refers to a directory.
33594 The requested access is not allowed.
33597 @var{pathname} was too long.
33600 A directory component in @var{pathname} does not exist.
33603 @var{pathname} refers to a device, pipe, named pipe or socket.
33606 @var{pathname} refers to a file on a read-only filesystem and
33607 write access was requested.
33610 @var{pathname} is an invalid pointer value.
33613 No space on device to create the file.
33616 The process already has the maximum number of files open.
33619 The limit on the total number of files open on the system
33623 The call was interrupted by the user.
33629 @unnumberedsubsubsec close
33630 @cindex close, file-i/o system call
33639 @samp{Fclose,@var{fd}}
33641 @item Return value:
33642 @code{close} returns zero on success, or -1 if an error occurred.
33648 @var{fd} isn't a valid open file descriptor.
33651 The call was interrupted by the user.
33657 @unnumberedsubsubsec read
33658 @cindex read, file-i/o system call
33663 int read(int fd, void *buf, unsigned int count);
33667 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33669 @item Return value:
33670 On success, the number of bytes read is returned.
33671 Zero indicates end of file. If count is zero, read
33672 returns zero as well. On error, -1 is returned.
33678 @var{fd} is not a valid file descriptor or is not open for
33682 @var{bufptr} is an invalid pointer value.
33685 The call was interrupted by the user.
33691 @unnumberedsubsubsec write
33692 @cindex write, file-i/o system call
33697 int write(int fd, const void *buf, unsigned int count);
33701 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33703 @item Return value:
33704 On success, the number of bytes written are returned.
33705 Zero indicates nothing was written. On error, -1
33712 @var{fd} is not a valid file descriptor or is not open for
33716 @var{bufptr} is an invalid pointer value.
33719 An attempt was made to write a file that exceeds the
33720 host-specific maximum file size allowed.
33723 No space on device to write the data.
33726 The call was interrupted by the user.
33732 @unnumberedsubsubsec lseek
33733 @cindex lseek, file-i/o system call
33738 long lseek (int fd, long offset, int flag);
33742 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33744 @var{flag} is one of:
33748 The offset is set to @var{offset} bytes.
33751 The offset is set to its current location plus @var{offset}
33755 The offset is set to the size of the file plus @var{offset}
33759 @item Return value:
33760 On success, the resulting unsigned offset in bytes from
33761 the beginning of the file is returned. Otherwise, a
33762 value of -1 is returned.
33768 @var{fd} is not a valid open file descriptor.
33771 @var{fd} is associated with the @value{GDBN} console.
33774 @var{flag} is not a proper value.
33777 The call was interrupted by the user.
33783 @unnumberedsubsubsec rename
33784 @cindex rename, file-i/o system call
33789 int rename(const char *oldpath, const char *newpath);
33793 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
33795 @item Return value:
33796 On success, zero is returned. On error, -1 is returned.
33802 @var{newpath} is an existing directory, but @var{oldpath} is not a
33806 @var{newpath} is a non-empty directory.
33809 @var{oldpath} or @var{newpath} is a directory that is in use by some
33813 An attempt was made to make a directory a subdirectory
33817 A component used as a directory in @var{oldpath} or new
33818 path is not a directory. Or @var{oldpath} is a directory
33819 and @var{newpath} exists but is not a directory.
33822 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
33825 No access to the file or the path of the file.
33829 @var{oldpath} or @var{newpath} was too long.
33832 A directory component in @var{oldpath} or @var{newpath} does not exist.
33835 The file is on a read-only filesystem.
33838 The device containing the file has no room for the new
33842 The call was interrupted by the user.
33848 @unnumberedsubsubsec unlink
33849 @cindex unlink, file-i/o system call
33854 int unlink(const char *pathname);
33858 @samp{Funlink,@var{pathnameptr}/@var{len}}
33860 @item Return value:
33861 On success, zero is returned. On error, -1 is returned.
33867 No access to the file or the path of the file.
33870 The system does not allow unlinking of directories.
33873 The file @var{pathname} cannot be unlinked because it's
33874 being used by another process.
33877 @var{pathnameptr} is an invalid pointer value.
33880 @var{pathname} was too long.
33883 A directory component in @var{pathname} does not exist.
33886 A component of the path is not a directory.
33889 The file is on a read-only filesystem.
33892 The call was interrupted by the user.
33898 @unnumberedsubsubsec stat/fstat
33899 @cindex fstat, file-i/o system call
33900 @cindex stat, file-i/o system call
33905 int stat(const char *pathname, struct stat *buf);
33906 int fstat(int fd, struct stat *buf);
33910 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
33911 @samp{Ffstat,@var{fd},@var{bufptr}}
33913 @item Return value:
33914 On success, zero is returned. On error, -1 is returned.
33920 @var{fd} is not a valid open file.
33923 A directory component in @var{pathname} does not exist or the
33924 path is an empty string.
33927 A component of the path is not a directory.
33930 @var{pathnameptr} is an invalid pointer value.
33933 No access to the file or the path of the file.
33936 @var{pathname} was too long.
33939 The call was interrupted by the user.
33945 @unnumberedsubsubsec gettimeofday
33946 @cindex gettimeofday, file-i/o system call
33951 int gettimeofday(struct timeval *tv, void *tz);
33955 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33957 @item Return value:
33958 On success, 0 is returned, -1 otherwise.
33964 @var{tz} is a non-NULL pointer.
33967 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33973 @unnumberedsubsubsec isatty
33974 @cindex isatty, file-i/o system call
33979 int isatty(int fd);
33983 @samp{Fisatty,@var{fd}}
33985 @item Return value:
33986 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33992 The call was interrupted by the user.
33997 Note that the @code{isatty} call is treated as a special case: it returns
33998 1 to the target if the file descriptor is attached
33999 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34000 would require implementing @code{ioctl} and would be more complex than
34005 @unnumberedsubsubsec system
34006 @cindex system, file-i/o system call
34011 int system(const char *command);
34015 @samp{Fsystem,@var{commandptr}/@var{len}}
34017 @item Return value:
34018 If @var{len} is zero, the return value indicates whether a shell is
34019 available. A zero return value indicates a shell is not available.
34020 For non-zero @var{len}, the value returned is -1 on error and the
34021 return status of the command otherwise. Only the exit status of the
34022 command is returned, which is extracted from the host's @code{system}
34023 return value by calling @code{WEXITSTATUS(retval)}. In case
34024 @file{/bin/sh} could not be executed, 127 is returned.
34030 The call was interrupted by the user.
34035 @value{GDBN} takes over the full task of calling the necessary host calls
34036 to perform the @code{system} call. The return value of @code{system} on
34037 the host is simplified before it's returned
34038 to the target. Any termination signal information from the child process
34039 is discarded, and the return value consists
34040 entirely of the exit status of the called command.
34042 Due to security concerns, the @code{system} call is by default refused
34043 by @value{GDBN}. The user has to allow this call explicitly with the
34044 @code{set remote system-call-allowed 1} command.
34047 @item set remote system-call-allowed
34048 @kindex set remote system-call-allowed
34049 Control whether to allow the @code{system} calls in the File I/O
34050 protocol for the remote target. The default is zero (disabled).
34052 @item show remote system-call-allowed
34053 @kindex show remote system-call-allowed
34054 Show whether the @code{system} calls are allowed in the File I/O
34058 @node Protocol-specific Representation of Datatypes
34059 @subsection Protocol-specific Representation of Datatypes
34060 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34063 * Integral Datatypes::
34065 * Memory Transfer::
34070 @node Integral Datatypes
34071 @unnumberedsubsubsec Integral Datatypes
34072 @cindex integral datatypes, in file-i/o protocol
34074 The integral datatypes used in the system calls are @code{int},
34075 @code{unsigned int}, @code{long}, @code{unsigned long},
34076 @code{mode_t}, and @code{time_t}.
34078 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34079 implemented as 32 bit values in this protocol.
34081 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34083 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34084 in @file{limits.h}) to allow range checking on host and target.
34086 @code{time_t} datatypes are defined as seconds since the Epoch.
34088 All integral datatypes transferred as part of a memory read or write of a
34089 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34092 @node Pointer Values
34093 @unnumberedsubsubsec Pointer Values
34094 @cindex pointer values, in file-i/o protocol
34096 Pointers to target data are transmitted as they are. An exception
34097 is made for pointers to buffers for which the length isn't
34098 transmitted as part of the function call, namely strings. Strings
34099 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34106 which is a pointer to data of length 18 bytes at position 0x1aaf.
34107 The length is defined as the full string length in bytes, including
34108 the trailing null byte. For example, the string @code{"hello world"}
34109 at address 0x123456 is transmitted as
34115 @node Memory Transfer
34116 @unnumberedsubsubsec Memory Transfer
34117 @cindex memory transfer, in file-i/o protocol
34119 Structured data which is transferred using a memory read or write (for
34120 example, a @code{struct stat}) is expected to be in a protocol-specific format
34121 with all scalar multibyte datatypes being big endian. Translation to
34122 this representation needs to be done both by the target before the @code{F}
34123 packet is sent, and by @value{GDBN} before
34124 it transfers memory to the target. Transferred pointers to structured
34125 data should point to the already-coerced data at any time.
34129 @unnumberedsubsubsec struct stat
34130 @cindex struct stat, in file-i/o protocol
34132 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34133 is defined as follows:
34137 unsigned int st_dev; /* device */
34138 unsigned int st_ino; /* inode */
34139 mode_t st_mode; /* protection */
34140 unsigned int st_nlink; /* number of hard links */
34141 unsigned int st_uid; /* user ID of owner */
34142 unsigned int st_gid; /* group ID of owner */
34143 unsigned int st_rdev; /* device type (if inode device) */
34144 unsigned long st_size; /* total size, in bytes */
34145 unsigned long st_blksize; /* blocksize for filesystem I/O */
34146 unsigned long st_blocks; /* number of blocks allocated */
34147 time_t st_atime; /* time of last access */
34148 time_t st_mtime; /* time of last modification */
34149 time_t st_ctime; /* time of last change */
34153 The integral datatypes conform to the definitions given in the
34154 appropriate section (see @ref{Integral Datatypes}, for details) so this
34155 structure is of size 64 bytes.
34157 The values of several fields have a restricted meaning and/or
34163 A value of 0 represents a file, 1 the console.
34166 No valid meaning for the target. Transmitted unchanged.
34169 Valid mode bits are described in @ref{Constants}. Any other
34170 bits have currently no meaning for the target.
34175 No valid meaning for the target. Transmitted unchanged.
34180 These values have a host and file system dependent
34181 accuracy. Especially on Windows hosts, the file system may not
34182 support exact timing values.
34185 The target gets a @code{struct stat} of the above representation and is
34186 responsible for coercing it to the target representation before
34189 Note that due to size differences between the host, target, and protocol
34190 representations of @code{struct stat} members, these members could eventually
34191 get truncated on the target.
34193 @node struct timeval
34194 @unnumberedsubsubsec struct timeval
34195 @cindex struct timeval, in file-i/o protocol
34197 The buffer of type @code{struct timeval} used by the File-I/O protocol
34198 is defined as follows:
34202 time_t tv_sec; /* second */
34203 long tv_usec; /* microsecond */
34207 The integral datatypes conform to the definitions given in the
34208 appropriate section (see @ref{Integral Datatypes}, for details) so this
34209 structure is of size 8 bytes.
34212 @subsection Constants
34213 @cindex constants, in file-i/o protocol
34215 The following values are used for the constants inside of the
34216 protocol. @value{GDBN} and target are responsible for translating these
34217 values before and after the call as needed.
34228 @unnumberedsubsubsec Open Flags
34229 @cindex open flags, in file-i/o protocol
34231 All values are given in hexadecimal representation.
34243 @node mode_t Values
34244 @unnumberedsubsubsec mode_t Values
34245 @cindex mode_t values, in file-i/o protocol
34247 All values are given in octal representation.
34264 @unnumberedsubsubsec Errno Values
34265 @cindex errno values, in file-i/o protocol
34267 All values are given in decimal representation.
34292 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34293 any error value not in the list of supported error numbers.
34296 @unnumberedsubsubsec Lseek Flags
34297 @cindex lseek flags, in file-i/o protocol
34306 @unnumberedsubsubsec Limits
34307 @cindex limits, in file-i/o protocol
34309 All values are given in decimal representation.
34312 INT_MIN -2147483648
34314 UINT_MAX 4294967295
34315 LONG_MIN -9223372036854775808
34316 LONG_MAX 9223372036854775807
34317 ULONG_MAX 18446744073709551615
34320 @node File-I/O Examples
34321 @subsection File-I/O Examples
34322 @cindex file-i/o examples
34324 Example sequence of a write call, file descriptor 3, buffer is at target
34325 address 0x1234, 6 bytes should be written:
34328 <- @code{Fwrite,3,1234,6}
34329 @emph{request memory read from target}
34332 @emph{return "6 bytes written"}
34336 Example sequence of a read call, file descriptor 3, buffer is at target
34337 address 0x1234, 6 bytes should be read:
34340 <- @code{Fread,3,1234,6}
34341 @emph{request memory write to target}
34342 -> @code{X1234,6:XXXXXX}
34343 @emph{return "6 bytes read"}
34347 Example sequence of a read call, call fails on the host due to invalid
34348 file descriptor (@code{EBADF}):
34351 <- @code{Fread,3,1234,6}
34355 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34359 <- @code{Fread,3,1234,6}
34364 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34368 <- @code{Fread,3,1234,6}
34369 -> @code{X1234,6:XXXXXX}
34373 @node Library List Format
34374 @section Library List Format
34375 @cindex library list format, remote protocol
34377 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34378 same process as your application to manage libraries. In this case,
34379 @value{GDBN} can use the loader's symbol table and normal memory
34380 operations to maintain a list of shared libraries. On other
34381 platforms, the operating system manages loaded libraries.
34382 @value{GDBN} can not retrieve the list of currently loaded libraries
34383 through memory operations, so it uses the @samp{qXfer:libraries:read}
34384 packet (@pxref{qXfer library list read}) instead. The remote stub
34385 queries the target's operating system and reports which libraries
34388 The @samp{qXfer:libraries:read} packet returns an XML document which
34389 lists loaded libraries and their offsets. Each library has an
34390 associated name and one or more segment or section base addresses,
34391 which report where the library was loaded in memory.
34393 For the common case of libraries that are fully linked binaries, the
34394 library should have a list of segments. If the target supports
34395 dynamic linking of a relocatable object file, its library XML element
34396 should instead include a list of allocated sections. The segment or
34397 section bases are start addresses, not relocation offsets; they do not
34398 depend on the library's link-time base addresses.
34400 @value{GDBN} must be linked with the Expat library to support XML
34401 library lists. @xref{Expat}.
34403 A simple memory map, with one loaded library relocated by a single
34404 offset, looks like this:
34408 <library name="/lib/libc.so.6">
34409 <segment address="0x10000000"/>
34414 Another simple memory map, with one loaded library with three
34415 allocated sections (.text, .data, .bss), looks like this:
34419 <library name="sharedlib.o">
34420 <section address="0x10000000"/>
34421 <section address="0x20000000"/>
34422 <section address="0x30000000"/>
34427 The format of a library list is described by this DTD:
34430 <!-- library-list: Root element with versioning -->
34431 <!ELEMENT library-list (library)*>
34432 <!ATTLIST library-list version CDATA #FIXED "1.0">
34433 <!ELEMENT library (segment*, section*)>
34434 <!ATTLIST library name CDATA #REQUIRED>
34435 <!ELEMENT segment EMPTY>
34436 <!ATTLIST segment address CDATA #REQUIRED>
34437 <!ELEMENT section EMPTY>
34438 <!ATTLIST section address CDATA #REQUIRED>
34441 In addition, segments and section descriptors cannot be mixed within a
34442 single library element, and you must supply at least one segment or
34443 section for each library.
34445 @node Memory Map Format
34446 @section Memory Map Format
34447 @cindex memory map format
34449 To be able to write into flash memory, @value{GDBN} needs to obtain a
34450 memory map from the target. This section describes the format of the
34453 The memory map is obtained using the @samp{qXfer:memory-map:read}
34454 (@pxref{qXfer memory map read}) packet and is an XML document that
34455 lists memory regions.
34457 @value{GDBN} must be linked with the Expat library to support XML
34458 memory maps. @xref{Expat}.
34460 The top-level structure of the document is shown below:
34463 <?xml version="1.0"?>
34464 <!DOCTYPE memory-map
34465 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34466 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34472 Each region can be either:
34477 A region of RAM starting at @var{addr} and extending for @var{length}
34481 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34486 A region of read-only memory:
34489 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34494 A region of flash memory, with erasure blocks @var{blocksize}
34498 <memory type="flash" start="@var{addr}" length="@var{length}">
34499 <property name="blocksize">@var{blocksize}</property>
34505 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34506 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34507 packets to write to addresses in such ranges.
34509 The formal DTD for memory map format is given below:
34512 <!-- ................................................... -->
34513 <!-- Memory Map XML DTD ................................ -->
34514 <!-- File: memory-map.dtd .............................. -->
34515 <!-- .................................... .............. -->
34516 <!-- memory-map.dtd -->
34517 <!-- memory-map: Root element with versioning -->
34518 <!ELEMENT memory-map (memory | property)>
34519 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34520 <!ELEMENT memory (property)>
34521 <!-- memory: Specifies a memory region,
34522 and its type, or device. -->
34523 <!ATTLIST memory type CDATA #REQUIRED
34524 start CDATA #REQUIRED
34525 length CDATA #REQUIRED
34526 device CDATA #IMPLIED>
34527 <!-- property: Generic attribute tag -->
34528 <!ELEMENT property (#PCDATA | property)*>
34529 <!ATTLIST property name CDATA #REQUIRED>
34532 @node Thread List Format
34533 @section Thread List Format
34534 @cindex thread list format
34536 To efficiently update the list of threads and their attributes,
34537 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34538 (@pxref{qXfer threads read}) and obtains the XML document with
34539 the following structure:
34542 <?xml version="1.0"?>
34544 <thread id="id" core="0">
34545 ... description ...
34550 Each @samp{thread} element must have the @samp{id} attribute that
34551 identifies the thread (@pxref{thread-id syntax}). The
34552 @samp{core} attribute, if present, specifies which processor core
34553 the thread was last executing on. The content of the of @samp{thread}
34554 element is interpreted as human-readable auxilliary information.
34556 @include agentexpr.texi
34558 @node Trace File Format
34559 @appendix Trace File Format
34560 @cindex trace file format
34562 The trace file comes in three parts: a header, a textual description
34563 section, and a trace frame section with binary data.
34565 The header has the form @code{\x7fTRACE0\n}. The first byte is
34566 @code{0x7f} so as to indicate that the file contains binary data,
34567 while the @code{0} is a version number that may have different values
34570 The description section consists of multiple lines of @sc{ascii} text
34571 separated by newline characters (@code{0xa}). The lines may include a
34572 variety of optional descriptive or context-setting information, such
34573 as tracepoint definitions or register set size. @value{GDBN} will
34574 ignore any line that it does not recognize. An empty line marks the end
34577 @c FIXME add some specific types of data
34579 The trace frame section consists of a number of consecutive frames.
34580 Each frame begins with a two-byte tracepoint number, followed by a
34581 four-byte size giving the amount of data in the frame. The data in
34582 the frame consists of a number of blocks, each introduced by a
34583 character indicating its type (at least register, memory, and trace
34584 state variable). The data in this section is raw binary, not a
34585 hexadecimal or other encoding; its endianness matches the target's
34588 @c FIXME bi-arch may require endianness/arch info in description section
34591 @item R @var{bytes}
34592 Register block. The number and ordering of bytes matches that of a
34593 @code{g} packet in the remote protocol. Note that these are the
34594 actual bytes, in target order and @value{GDBN} register order, not a
34595 hexadecimal encoding.
34597 @item M @var{address} @var{length} @var{bytes}...
34598 Memory block. This is a contiguous block of memory, at the 8-byte
34599 address @var{address}, with a 2-byte length @var{length}, followed by
34600 @var{length} bytes.
34602 @item V @var{number} @var{value}
34603 Trace state variable block. This records the 8-byte signed value
34604 @var{value} of trace state variable numbered @var{number}.
34608 Future enhancements of the trace file format may include additional types
34611 @node Target Descriptions
34612 @appendix Target Descriptions
34613 @cindex target descriptions
34615 @strong{Warning:} target descriptions are still under active development,
34616 and the contents and format may change between @value{GDBN} releases.
34617 The format is expected to stabilize in the future.
34619 One of the challenges of using @value{GDBN} to debug embedded systems
34620 is that there are so many minor variants of each processor
34621 architecture in use. It is common practice for vendors to start with
34622 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34623 and then make changes to adapt it to a particular market niche. Some
34624 architectures have hundreds of variants, available from dozens of
34625 vendors. This leads to a number of problems:
34629 With so many different customized processors, it is difficult for
34630 the @value{GDBN} maintainers to keep up with the changes.
34632 Since individual variants may have short lifetimes or limited
34633 audiences, it may not be worthwhile to carry information about every
34634 variant in the @value{GDBN} source tree.
34636 When @value{GDBN} does support the architecture of the embedded system
34637 at hand, the task of finding the correct architecture name to give the
34638 @command{set architecture} command can be error-prone.
34641 To address these problems, the @value{GDBN} remote protocol allows a
34642 target system to not only identify itself to @value{GDBN}, but to
34643 actually describe its own features. This lets @value{GDBN} support
34644 processor variants it has never seen before --- to the extent that the
34645 descriptions are accurate, and that @value{GDBN} understands them.
34647 @value{GDBN} must be linked with the Expat library to support XML
34648 target descriptions. @xref{Expat}.
34651 * Retrieving Descriptions:: How descriptions are fetched from a target.
34652 * Target Description Format:: The contents of a target description.
34653 * Predefined Target Types:: Standard types available for target
34655 * Standard Target Features:: Features @value{GDBN} knows about.
34658 @node Retrieving Descriptions
34659 @section Retrieving Descriptions
34661 Target descriptions can be read from the target automatically, or
34662 specified by the user manually. The default behavior is to read the
34663 description from the target. @value{GDBN} retrieves it via the remote
34664 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34665 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34666 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34667 XML document, of the form described in @ref{Target Description
34670 Alternatively, you can specify a file to read for the target description.
34671 If a file is set, the target will not be queried. The commands to
34672 specify a file are:
34675 @cindex set tdesc filename
34676 @item set tdesc filename @var{path}
34677 Read the target description from @var{path}.
34679 @cindex unset tdesc filename
34680 @item unset tdesc filename
34681 Do not read the XML target description from a file. @value{GDBN}
34682 will use the description supplied by the current target.
34684 @cindex show tdesc filename
34685 @item show tdesc filename
34686 Show the filename to read for a target description, if any.
34690 @node Target Description Format
34691 @section Target Description Format
34692 @cindex target descriptions, XML format
34694 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34695 document which complies with the Document Type Definition provided in
34696 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34697 means you can use generally available tools like @command{xmllint} to
34698 check that your feature descriptions are well-formed and valid.
34699 However, to help people unfamiliar with XML write descriptions for
34700 their targets, we also describe the grammar here.
34702 Target descriptions can identify the architecture of the remote target
34703 and (for some architectures) provide information about custom register
34704 sets. They can also identify the OS ABI of the remote target.
34705 @value{GDBN} can use this information to autoconfigure for your
34706 target, or to warn you if you connect to an unsupported target.
34708 Here is a simple target description:
34711 <target version="1.0">
34712 <architecture>i386:x86-64</architecture>
34717 This minimal description only says that the target uses
34718 the x86-64 architecture.
34720 A target description has the following overall form, with [ ] marking
34721 optional elements and @dots{} marking repeatable elements. The elements
34722 are explained further below.
34725 <?xml version="1.0"?>
34726 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34727 <target version="1.0">
34728 @r{[}@var{architecture}@r{]}
34729 @r{[}@var{osabi}@r{]}
34730 @r{[}@var{compatible}@r{]}
34731 @r{[}@var{feature}@dots{}@r{]}
34736 The description is generally insensitive to whitespace and line
34737 breaks, under the usual common-sense rules. The XML version
34738 declaration and document type declaration can generally be omitted
34739 (@value{GDBN} does not require them), but specifying them may be
34740 useful for XML validation tools. The @samp{version} attribute for
34741 @samp{<target>} may also be omitted, but we recommend
34742 including it; if future versions of @value{GDBN} use an incompatible
34743 revision of @file{gdb-target.dtd}, they will detect and report
34744 the version mismatch.
34746 @subsection Inclusion
34747 @cindex target descriptions, inclusion
34750 @cindex <xi:include>
34753 It can sometimes be valuable to split a target description up into
34754 several different annexes, either for organizational purposes, or to
34755 share files between different possible target descriptions. You can
34756 divide a description into multiple files by replacing any element of
34757 the target description with an inclusion directive of the form:
34760 <xi:include href="@var{document}"/>
34764 When @value{GDBN} encounters an element of this form, it will retrieve
34765 the named XML @var{document}, and replace the inclusion directive with
34766 the contents of that document. If the current description was read
34767 using @samp{qXfer}, then so will be the included document;
34768 @var{document} will be interpreted as the name of an annex. If the
34769 current description was read from a file, @value{GDBN} will look for
34770 @var{document} as a file in the same directory where it found the
34771 original description.
34773 @subsection Architecture
34774 @cindex <architecture>
34776 An @samp{<architecture>} element has this form:
34779 <architecture>@var{arch}</architecture>
34782 @var{arch} is one of the architectures from the set accepted by
34783 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34786 @cindex @code{<osabi>}
34788 This optional field was introduced in @value{GDBN} version 7.0.
34789 Previous versions of @value{GDBN} ignore it.
34791 An @samp{<osabi>} element has this form:
34794 <osabi>@var{abi-name}</osabi>
34797 @var{abi-name} is an OS ABI name from the same selection accepted by
34798 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
34800 @subsection Compatible Architecture
34801 @cindex @code{<compatible>}
34803 This optional field was introduced in @value{GDBN} version 7.0.
34804 Previous versions of @value{GDBN} ignore it.
34806 A @samp{<compatible>} element has this form:
34809 <compatible>@var{arch}</compatible>
34812 @var{arch} is one of the architectures from the set accepted by
34813 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34815 A @samp{<compatible>} element is used to specify that the target
34816 is able to run binaries in some other than the main target architecture
34817 given by the @samp{<architecture>} element. For example, on the
34818 Cell Broadband Engine, the main architecture is @code{powerpc:common}
34819 or @code{powerpc:common64}, but the system is able to run binaries
34820 in the @code{spu} architecture as well. The way to describe this
34821 capability with @samp{<compatible>} is as follows:
34824 <architecture>powerpc:common</architecture>
34825 <compatible>spu</compatible>
34828 @subsection Features
34831 Each @samp{<feature>} describes some logical portion of the target
34832 system. Features are currently used to describe available CPU
34833 registers and the types of their contents. A @samp{<feature>} element
34837 <feature name="@var{name}">
34838 @r{[}@var{type}@dots{}@r{]}
34844 Each feature's name should be unique within the description. The name
34845 of a feature does not matter unless @value{GDBN} has some special
34846 knowledge of the contents of that feature; if it does, the feature
34847 should have its standard name. @xref{Standard Target Features}.
34851 Any register's value is a collection of bits which @value{GDBN} must
34852 interpret. The default interpretation is a two's complement integer,
34853 but other types can be requested by name in the register description.
34854 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
34855 Target Types}), and the description can define additional composite types.
34857 Each type element must have an @samp{id} attribute, which gives
34858 a unique (within the containing @samp{<feature>}) name to the type.
34859 Types must be defined before they are used.
34862 Some targets offer vector registers, which can be treated as arrays
34863 of scalar elements. These types are written as @samp{<vector>} elements,
34864 specifying the array element type, @var{type}, and the number of elements,
34868 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
34872 If a register's value is usefully viewed in multiple ways, define it
34873 with a union type containing the useful representations. The
34874 @samp{<union>} element contains one or more @samp{<field>} elements,
34875 each of which has a @var{name} and a @var{type}:
34878 <union id="@var{id}">
34879 <field name="@var{name}" type="@var{type}"/>
34885 If a register's value is composed from several separate values, define
34886 it with a structure type. There are two forms of the @samp{<struct>}
34887 element; a @samp{<struct>} element must either contain only bitfields
34888 or contain no bitfields. If the structure contains only bitfields,
34889 its total size in bytes must be specified, each bitfield must have an
34890 explicit start and end, and bitfields are automatically assigned an
34891 integer type. The field's @var{start} should be less than or
34892 equal to its @var{end}, and zero represents the least significant bit.
34895 <struct id="@var{id}" size="@var{size}">
34896 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34901 If the structure contains no bitfields, then each field has an
34902 explicit type, and no implicit padding is added.
34905 <struct id="@var{id}">
34906 <field name="@var{name}" type="@var{type}"/>
34912 If a register's value is a series of single-bit flags, define it with
34913 a flags type. The @samp{<flags>} element has an explicit @var{size}
34914 and contains one or more @samp{<field>} elements. Each field has a
34915 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
34919 <flags id="@var{id}" size="@var{size}">
34920 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34925 @subsection Registers
34928 Each register is represented as an element with this form:
34931 <reg name="@var{name}"
34932 bitsize="@var{size}"
34933 @r{[}regnum="@var{num}"@r{]}
34934 @r{[}save-restore="@var{save-restore}"@r{]}
34935 @r{[}type="@var{type}"@r{]}
34936 @r{[}group="@var{group}"@r{]}/>
34940 The components are as follows:
34945 The register's name; it must be unique within the target description.
34948 The register's size, in bits.
34951 The register's number. If omitted, a register's number is one greater
34952 than that of the previous register (either in the current feature or in
34953 a preceeding feature); the first register in the target description
34954 defaults to zero. This register number is used to read or write
34955 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34956 packets, and registers appear in the @code{g} and @code{G} packets
34957 in order of increasing register number.
34960 Whether the register should be preserved across inferior function
34961 calls; this must be either @code{yes} or @code{no}. The default is
34962 @code{yes}, which is appropriate for most registers except for
34963 some system control registers; this is not related to the target's
34967 The type of the register. @var{type} may be a predefined type, a type
34968 defined in the current feature, or one of the special types @code{int}
34969 and @code{float}. @code{int} is an integer type of the correct size
34970 for @var{bitsize}, and @code{float} is a floating point type (in the
34971 architecture's normal floating point format) of the correct size for
34972 @var{bitsize}. The default is @code{int}.
34975 The register group to which this register belongs. @var{group} must
34976 be either @code{general}, @code{float}, or @code{vector}. If no
34977 @var{group} is specified, @value{GDBN} will not display the register
34978 in @code{info registers}.
34982 @node Predefined Target Types
34983 @section Predefined Target Types
34984 @cindex target descriptions, predefined types
34986 Type definitions in the self-description can build up composite types
34987 from basic building blocks, but can not define fundamental types. Instead,
34988 standard identifiers are provided by @value{GDBN} for the fundamental
34989 types. The currently supported types are:
34998 Signed integer types holding the specified number of bits.
35005 Unsigned integer types holding the specified number of bits.
35009 Pointers to unspecified code and data. The program counter and
35010 any dedicated return address register may be marked as code
35011 pointers; printing a code pointer converts it into a symbolic
35012 address. The stack pointer and any dedicated address registers
35013 may be marked as data pointers.
35016 Single precision IEEE floating point.
35019 Double precision IEEE floating point.
35022 The 12-byte extended precision format used by ARM FPA registers.
35025 The 10-byte extended precision format used by x87 registers.
35028 32bit @sc{eflags} register used by x86.
35031 32bit @sc{mxcsr} register used by x86.
35035 @node Standard Target Features
35036 @section Standard Target Features
35037 @cindex target descriptions, standard features
35039 A target description must contain either no registers or all the
35040 target's registers. If the description contains no registers, then
35041 @value{GDBN} will assume a default register layout, selected based on
35042 the architecture. If the description contains any registers, the
35043 default layout will not be used; the standard registers must be
35044 described in the target description, in such a way that @value{GDBN}
35045 can recognize them.
35047 This is accomplished by giving specific names to feature elements
35048 which contain standard registers. @value{GDBN} will look for features
35049 with those names and verify that they contain the expected registers;
35050 if any known feature is missing required registers, or if any required
35051 feature is missing, @value{GDBN} will reject the target
35052 description. You can add additional registers to any of the
35053 standard features --- @value{GDBN} will display them just as if
35054 they were added to an unrecognized feature.
35056 This section lists the known features and their expected contents.
35057 Sample XML documents for these features are included in the
35058 @value{GDBN} source tree, in the directory @file{gdb/features}.
35060 Names recognized by @value{GDBN} should include the name of the
35061 company or organization which selected the name, and the overall
35062 architecture to which the feature applies; so e.g.@: the feature
35063 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35065 The names of registers are not case sensitive for the purpose
35066 of recognizing standard features, but @value{GDBN} will only display
35067 registers using the capitalization used in the description.
35074 * PowerPC Features::
35079 @subsection ARM Features
35080 @cindex target descriptions, ARM features
35082 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35083 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35084 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35086 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35087 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35089 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35090 it should contain at least registers @samp{wR0} through @samp{wR15} and
35091 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35092 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35094 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35095 should contain at least registers @samp{d0} through @samp{d15}. If
35096 they are present, @samp{d16} through @samp{d31} should also be included.
35097 @value{GDBN} will synthesize the single-precision registers from
35098 halves of the double-precision registers.
35100 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35101 need to contain registers; it instructs @value{GDBN} to display the
35102 VFP double-precision registers as vectors and to synthesize the
35103 quad-precision registers from pairs of double-precision registers.
35104 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35105 be present and include 32 double-precision registers.
35107 @node i386 Features
35108 @subsection i386 Features
35109 @cindex target descriptions, i386 features
35111 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35112 targets. It should describe the following registers:
35116 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35118 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35120 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35121 @samp{fs}, @samp{gs}
35123 @samp{st0} through @samp{st7}
35125 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35126 @samp{foseg}, @samp{fooff} and @samp{fop}
35129 The register sets may be different, depending on the target.
35131 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35132 describe registers:
35136 @samp{xmm0} through @samp{xmm7} for i386
35138 @samp{xmm0} through @samp{xmm15} for amd64
35143 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35144 @samp{org.gnu.gdb.i386.sse} feature. It should
35145 describe the upper 128 bits of @sc{ymm} registers:
35149 @samp{ymm0h} through @samp{ymm7h} for i386
35151 @samp{ymm0h} through @samp{ymm15h} for amd64
35155 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35156 describe a single register, @samp{orig_eax}.
35158 @node MIPS Features
35159 @subsection MIPS Features
35160 @cindex target descriptions, MIPS features
35162 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35163 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35164 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35167 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35168 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35169 registers. They may be 32-bit or 64-bit depending on the target.
35171 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35172 it may be optional in a future version of @value{GDBN}. It should
35173 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35174 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35176 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35177 contain a single register, @samp{restart}, which is used by the
35178 Linux kernel to control restartable syscalls.
35180 @node M68K Features
35181 @subsection M68K Features
35182 @cindex target descriptions, M68K features
35185 @item @samp{org.gnu.gdb.m68k.core}
35186 @itemx @samp{org.gnu.gdb.coldfire.core}
35187 @itemx @samp{org.gnu.gdb.fido.core}
35188 One of those features must be always present.
35189 The feature that is present determines which flavor of m68k is
35190 used. The feature that is present should contain registers
35191 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35192 @samp{sp}, @samp{ps} and @samp{pc}.
35194 @item @samp{org.gnu.gdb.coldfire.fp}
35195 This feature is optional. If present, it should contain registers
35196 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35200 @node PowerPC Features
35201 @subsection PowerPC Features
35202 @cindex target descriptions, PowerPC features
35204 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35205 targets. It should contain registers @samp{r0} through @samp{r31},
35206 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35207 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35209 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35210 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35212 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35213 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35216 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35217 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35218 will combine these registers with the floating point registers
35219 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35220 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35221 through @samp{vs63}, the set of vector registers for POWER7.
35223 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35224 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35225 @samp{spefscr}. SPE targets should provide 32-bit registers in
35226 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35227 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35228 these to present registers @samp{ev0} through @samp{ev31} to the
35231 @node Operating System Information
35232 @appendix Operating System Information
35233 @cindex operating system information
35239 Users of @value{GDBN} often wish to obtain information about the state of
35240 the operating system running on the target---for example the list of
35241 processes, or the list of open files. This section describes the
35242 mechanism that makes it possible. This mechanism is similar to the
35243 target features mechanism (@pxref{Target Descriptions}), but focuses
35244 on a different aspect of target.
35246 Operating system information is retrived from the target via the
35247 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35248 read}). The object name in the request should be @samp{osdata}, and
35249 the @var{annex} identifies the data to be fetched.
35252 @appendixsection Process list
35253 @cindex operating system information, process list
35255 When requesting the process list, the @var{annex} field in the
35256 @samp{qXfer} request should be @samp{processes}. The returned data is
35257 an XML document. The formal syntax of this document is defined in
35258 @file{gdb/features/osdata.dtd}.
35260 An example document is:
35263 <?xml version="1.0"?>
35264 <!DOCTYPE target SYSTEM "osdata.dtd">
35265 <osdata type="processes">
35267 <column name="pid">1</column>
35268 <column name="user">root</column>
35269 <column name="command">/sbin/init</column>
35270 <column name="cores">1,2,3</column>
35275 Each item should include a column whose name is @samp{pid}. The value
35276 of that column should identify the process on the target. The
35277 @samp{user} and @samp{command} columns are optional, and will be
35278 displayed by @value{GDBN}. The @samp{cores} column, if present,
35279 should contain a comma-separated list of cores that this process
35280 is running on. Target may provide additional columns,
35281 which @value{GDBN} currently ignores.
35285 @node GNU Free Documentation License
35286 @appendix GNU Free Documentation License
35295 % I think something like @colophon should be in texinfo. In the
35297 \long\def\colophon{\hbox to0pt{}\vfill
35298 \centerline{The body of this manual is set in}
35299 \centerline{\fontname\tenrm,}
35300 \centerline{with headings in {\bf\fontname\tenbf}}
35301 \centerline{and examples in {\tt\fontname\tentt}.}
35302 \centerline{{\it\fontname\tenit\/},}
35303 \centerline{{\bf\fontname\tenbf}, and}
35304 \centerline{{\sl\fontname\tensl\/}}
35305 \centerline{are used for emphasis.}\vfill}
35307 % Blame: doc@cygnus.com, 1991.