1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
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 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2802 @kindex set print thread-events
2803 @cindex print messages on thread start and exit
2804 @item set print thread-events
2805 @itemx set print thread-events on
2806 @itemx set print thread-events off
2807 The @code{set print thread-events} command allows you to enable or
2808 disable printing of messages when @value{GDBN} notices that new threads have
2809 started or that threads have exited. By default, these messages will
2810 be printed if detection of these events is supported by the target.
2811 Note that these messages cannot be disabled on all targets.
2813 @kindex show print thread-events
2814 @item show print thread-events
2815 Show whether messages will be printed when @value{GDBN} detects that threads
2816 have started and exited.
2819 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2820 more information about how @value{GDBN} behaves when you stop and start
2821 programs with multiple threads.
2823 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2824 watchpoints in programs with multiple threads.
2827 @kindex set libthread-db-search-path
2828 @cindex search path for @code{libthread_db}
2829 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2830 If this variable is set, @var{path} is a colon-separated list of
2831 directories @value{GDBN} will use to search for @code{libthread_db}.
2832 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2835 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2836 @code{libthread_db} library to obtain information about threads in the
2837 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2838 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2839 with default system shared library directories, and finally the directory
2840 from which @code{libpthread} was loaded in the inferior process.
2842 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2843 @value{GDBN} attempts to initialize it with the current inferior process.
2844 If this initialization fails (which could happen because of a version
2845 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2846 will unload @code{libthread_db}, and continue with the next directory.
2847 If none of @code{libthread_db} libraries initialize successfully,
2848 @value{GDBN} will issue a warning and thread debugging will be disabled.
2850 Setting @code{libthread-db-search-path} is currently implemented
2851 only on some platforms.
2853 @kindex show libthread-db-search-path
2854 @item show libthread-db-search-path
2855 Display current libthread_db search path.
2859 @section Debugging Forks
2861 @cindex fork, debugging programs which call
2862 @cindex multiple processes
2863 @cindex processes, multiple
2864 On most systems, @value{GDBN} has no special support for debugging
2865 programs which create additional processes using the @code{fork}
2866 function. When a program forks, @value{GDBN} will continue to debug the
2867 parent process and the child process will run unimpeded. If you have
2868 set a breakpoint in any code which the child then executes, the child
2869 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2870 will cause it to terminate.
2872 However, if you want to debug the child process there is a workaround
2873 which isn't too painful. Put a call to @code{sleep} in the code which
2874 the child process executes after the fork. It may be useful to sleep
2875 only if a certain environment variable is set, or a certain file exists,
2876 so that the delay need not occur when you don't want to run @value{GDBN}
2877 on the child. While the child is sleeping, use the @code{ps} program to
2878 get its process ID. Then tell @value{GDBN} (a new invocation of
2879 @value{GDBN} if you are also debugging the parent process) to attach to
2880 the child process (@pxref{Attach}). From that point on you can debug
2881 the child process just like any other process which you attached to.
2883 On some systems, @value{GDBN} provides support for debugging programs that
2884 create additional processes using the @code{fork} or @code{vfork} functions.
2885 Currently, the only platforms with this feature are HP-UX (11.x and later
2886 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2888 By default, when a program forks, @value{GDBN} will continue to debug
2889 the parent process and the child process will run unimpeded.
2891 If you want to follow the child process instead of the parent process,
2892 use the command @w{@code{set follow-fork-mode}}.
2895 @kindex set follow-fork-mode
2896 @item set follow-fork-mode @var{mode}
2897 Set the debugger response to a program call of @code{fork} or
2898 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2899 process. The @var{mode} argument can be:
2903 The original process is debugged after a fork. The child process runs
2904 unimpeded. This is the default.
2907 The new process is debugged after a fork. The parent process runs
2912 @kindex show follow-fork-mode
2913 @item show follow-fork-mode
2914 Display the current debugger response to a @code{fork} or @code{vfork} call.
2917 @cindex debugging multiple processes
2918 On Linux, if you want to debug both the parent and child processes, use the
2919 command @w{@code{set detach-on-fork}}.
2922 @kindex set detach-on-fork
2923 @item set detach-on-fork @var{mode}
2924 Tells gdb whether to detach one of the processes after a fork, or
2925 retain debugger control over them both.
2929 The child process (or parent process, depending on the value of
2930 @code{follow-fork-mode}) will be detached and allowed to run
2931 independently. This is the default.
2934 Both processes will be held under the control of @value{GDBN}.
2935 One process (child or parent, depending on the value of
2936 @code{follow-fork-mode}) is debugged as usual, while the other
2941 @kindex show detach-on-fork
2942 @item show detach-on-fork
2943 Show whether detach-on-fork mode is on/off.
2946 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2947 will retain control of all forked processes (including nested forks).
2948 You can list the forked processes under the control of @value{GDBN} by
2949 using the @w{@code{info inferiors}} command, and switch from one fork
2950 to another by using the @code{inferior} command (@pxref{Inferiors and
2951 Programs, ,Debugging Multiple Inferiors and Programs}).
2953 To quit debugging one of the forked processes, you can either detach
2954 from it by using the @w{@code{detach inferior}} command (allowing it
2955 to run independently), or kill it using the @w{@code{kill inferior}}
2956 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2959 If you ask to debug a child process and a @code{vfork} is followed by an
2960 @code{exec}, @value{GDBN} executes the new target up to the first
2961 breakpoint in the new target. If you have a breakpoint set on
2962 @code{main} in your original program, the breakpoint will also be set on
2963 the child process's @code{main}.
2965 On some systems, when a child process is spawned by @code{vfork}, you
2966 cannot debug the child or parent until an @code{exec} call completes.
2968 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2969 call executes, the new target restarts. To restart the parent
2970 process, use the @code{file} command with the parent executable name
2971 as its argument. By default, after an @code{exec} call executes,
2972 @value{GDBN} discards the symbols of the previous executable image.
2973 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2977 @kindex set follow-exec-mode
2978 @item set follow-exec-mode @var{mode}
2980 Set debugger response to a program call of @code{exec}. An
2981 @code{exec} call replaces the program image of a process.
2983 @code{follow-exec-mode} can be:
2987 @value{GDBN} creates a new inferior and rebinds the process to this
2988 new inferior. The program the process was running before the
2989 @code{exec} call can be restarted afterwards by restarting the
2995 (@value{GDBP}) info inferiors
2997 Id Description Executable
3000 process 12020 is executing new program: prog2
3001 Program exited normally.
3002 (@value{GDBP}) info inferiors
3003 Id Description Executable
3009 @value{GDBN} keeps the process bound to the same inferior. The new
3010 executable image replaces the previous executable loaded in the
3011 inferior. Restarting the inferior after the @code{exec} call, with
3012 e.g., the @code{run} command, restarts the executable the process was
3013 running after the @code{exec} call. This is the default mode.
3018 (@value{GDBP}) info inferiors
3019 Id Description Executable
3022 process 12020 is executing new program: prog2
3023 Program exited normally.
3024 (@value{GDBP}) info inferiors
3025 Id Description Executable
3032 You can use the @code{catch} command to make @value{GDBN} stop whenever
3033 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3034 Catchpoints, ,Setting Catchpoints}.
3036 @node Checkpoint/Restart
3037 @section Setting a @emph{Bookmark} to Return to Later
3042 @cindex snapshot of a process
3043 @cindex rewind program state
3045 On certain operating systems@footnote{Currently, only
3046 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3047 program's state, called a @dfn{checkpoint}, and come back to it
3050 Returning to a checkpoint effectively undoes everything that has
3051 happened in the program since the @code{checkpoint} was saved. This
3052 includes changes in memory, registers, and even (within some limits)
3053 system state. Effectively, it is like going back in time to the
3054 moment when the checkpoint was saved.
3056 Thus, if you're stepping thru a program and you think you're
3057 getting close to the point where things go wrong, you can save
3058 a checkpoint. Then, if you accidentally go too far and miss
3059 the critical statement, instead of having to restart your program
3060 from the beginning, you can just go back to the checkpoint and
3061 start again from there.
3063 This can be especially useful if it takes a lot of time or
3064 steps to reach the point where you think the bug occurs.
3066 To use the @code{checkpoint}/@code{restart} method of debugging:
3071 Save a snapshot of the debugged program's current execution state.
3072 The @code{checkpoint} command takes no arguments, but each checkpoint
3073 is assigned a small integer id, similar to a breakpoint id.
3075 @kindex info checkpoints
3076 @item info checkpoints
3077 List the checkpoints that have been saved in the current debugging
3078 session. For each checkpoint, the following information will be
3085 @item Source line, or label
3088 @kindex restart @var{checkpoint-id}
3089 @item restart @var{checkpoint-id}
3090 Restore the program state that was saved as checkpoint number
3091 @var{checkpoint-id}. All program variables, registers, stack frames
3092 etc.@: will be returned to the values that they had when the checkpoint
3093 was saved. In essence, gdb will ``wind back the clock'' to the point
3094 in time when the checkpoint was saved.
3096 Note that breakpoints, @value{GDBN} variables, command history etc.
3097 are not affected by restoring a checkpoint. In general, a checkpoint
3098 only restores things that reside in the program being debugged, not in
3101 @kindex delete checkpoint @var{checkpoint-id}
3102 @item delete checkpoint @var{checkpoint-id}
3103 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3107 Returning to a previously saved checkpoint will restore the user state
3108 of the program being debugged, plus a significant subset of the system
3109 (OS) state, including file pointers. It won't ``un-write'' data from
3110 a file, but it will rewind the file pointer to the previous location,
3111 so that the previously written data can be overwritten. For files
3112 opened in read mode, the pointer will also be restored so that the
3113 previously read data can be read again.
3115 Of course, characters that have been sent to a printer (or other
3116 external device) cannot be ``snatched back'', and characters received
3117 from eg.@: a serial device can be removed from internal program buffers,
3118 but they cannot be ``pushed back'' into the serial pipeline, ready to
3119 be received again. Similarly, the actual contents of files that have
3120 been changed cannot be restored (at this time).
3122 However, within those constraints, you actually can ``rewind'' your
3123 program to a previously saved point in time, and begin debugging it
3124 again --- and you can change the course of events so as to debug a
3125 different execution path this time.
3127 @cindex checkpoints and process id
3128 Finally, there is one bit of internal program state that will be
3129 different when you return to a checkpoint --- the program's process
3130 id. Each checkpoint will have a unique process id (or @var{pid}),
3131 and each will be different from the program's original @var{pid}.
3132 If your program has saved a local copy of its process id, this could
3133 potentially pose a problem.
3135 @subsection A Non-obvious Benefit of Using Checkpoints
3137 On some systems such as @sc{gnu}/Linux, address space randomization
3138 is performed on new processes for security reasons. This makes it
3139 difficult or impossible to set a breakpoint, or watchpoint, on an
3140 absolute address if you have to restart the program, since the
3141 absolute location of a symbol will change from one execution to the
3144 A checkpoint, however, is an @emph{identical} copy of a process.
3145 Therefore if you create a checkpoint at (eg.@:) the start of main,
3146 and simply return to that checkpoint instead of restarting the
3147 process, you can avoid the effects of address randomization and
3148 your symbols will all stay in the same place.
3151 @chapter Stopping and Continuing
3153 The principal purposes of using a debugger are so that you can stop your
3154 program before it terminates; or so that, if your program runs into
3155 trouble, you can investigate and find out why.
3157 Inside @value{GDBN}, your program may stop for any of several reasons,
3158 such as a signal, a breakpoint, or reaching a new line after a
3159 @value{GDBN} command such as @code{step}. You may then examine and
3160 change variables, set new breakpoints or remove old ones, and then
3161 continue execution. Usually, the messages shown by @value{GDBN} provide
3162 ample explanation of the status of your program---but you can also
3163 explicitly request this information at any time.
3166 @kindex info program
3168 Display information about the status of your program: whether it is
3169 running or not, what process it is, and why it stopped.
3173 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3174 * Continuing and Stepping:: Resuming execution
3176 * Thread Stops:: Stopping and starting multi-thread programs
3180 @section Breakpoints, Watchpoints, and Catchpoints
3183 A @dfn{breakpoint} makes your program stop whenever a certain point in
3184 the program is reached. For each breakpoint, you can add conditions to
3185 control in finer detail whether your program stops. You can set
3186 breakpoints with the @code{break} command and its variants (@pxref{Set
3187 Breaks, ,Setting Breakpoints}), to specify the place where your program
3188 should stop by line number, function name or exact address in the
3191 On some systems, you can set breakpoints in shared libraries before
3192 the executable is run. There is a minor limitation on HP-UX systems:
3193 you must wait until the executable is run in order to set breakpoints
3194 in shared library routines that are not called directly by the program
3195 (for example, routines that are arguments in a @code{pthread_create}
3199 @cindex data breakpoints
3200 @cindex memory tracing
3201 @cindex breakpoint on memory address
3202 @cindex breakpoint on variable modification
3203 A @dfn{watchpoint} is a special breakpoint that stops your program
3204 when the value of an expression changes. The expression may be a value
3205 of a variable, or it could involve values of one or more variables
3206 combined by operators, such as @samp{a + b}. This is sometimes called
3207 @dfn{data breakpoints}. You must use a different command to set
3208 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3209 from that, you can manage a watchpoint like any other breakpoint: you
3210 enable, disable, and delete both breakpoints and watchpoints using the
3213 You can arrange to have values from your program displayed automatically
3214 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3218 @cindex breakpoint on events
3219 A @dfn{catchpoint} is another special breakpoint that stops your program
3220 when a certain kind of event occurs, such as the throwing of a C@t{++}
3221 exception or the loading of a library. As with watchpoints, you use a
3222 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3223 Catchpoints}), but aside from that, you can manage a catchpoint like any
3224 other breakpoint. (To stop when your program receives a signal, use the
3225 @code{handle} command; see @ref{Signals, ,Signals}.)
3227 @cindex breakpoint numbers
3228 @cindex numbers for breakpoints
3229 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3230 catchpoint when you create it; these numbers are successive integers
3231 starting with one. In many of the commands for controlling various
3232 features of breakpoints you use the breakpoint number to say which
3233 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3234 @dfn{disabled}; if disabled, it has no effect on your program until you
3237 @cindex breakpoint ranges
3238 @cindex ranges of breakpoints
3239 Some @value{GDBN} commands accept a range of breakpoints on which to
3240 operate. A breakpoint range is either a single breakpoint number, like
3241 @samp{5}, or two such numbers, in increasing order, separated by a
3242 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3243 all breakpoints in that range are operated on.
3246 * Set Breaks:: Setting breakpoints
3247 * Set Watchpoints:: Setting watchpoints
3248 * Set Catchpoints:: Setting catchpoints
3249 * Delete Breaks:: Deleting breakpoints
3250 * Disabling:: Disabling breakpoints
3251 * Conditions:: Break conditions
3252 * Break Commands:: Breakpoint command lists
3253 * Save Breakpoints:: How to save breakpoints in a file
3254 * Error in Breakpoints:: ``Cannot insert breakpoints''
3255 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3259 @subsection Setting Breakpoints
3261 @c FIXME LMB what does GDB do if no code on line of breakpt?
3262 @c consider in particular declaration with/without initialization.
3264 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3267 @kindex b @r{(@code{break})}
3268 @vindex $bpnum@r{, convenience variable}
3269 @cindex latest breakpoint
3270 Breakpoints are set with the @code{break} command (abbreviated
3271 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3272 number of the breakpoint you've set most recently; see @ref{Convenience
3273 Vars,, Convenience Variables}, for a discussion of what you can do with
3274 convenience variables.
3277 @item break @var{location}
3278 Set a breakpoint at the given @var{location}, which can specify a
3279 function name, a line number, or an address of an instruction.
3280 (@xref{Specify Location}, for a list of all the possible ways to
3281 specify a @var{location}.) The breakpoint will stop your program just
3282 before it executes any of the code in the specified @var{location}.
3284 When using source languages that permit overloading of symbols, such as
3285 C@t{++}, a function name may refer to more than one possible place to break.
3286 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3289 It is also possible to insert a breakpoint that will stop the program
3290 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3291 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3294 When called without any arguments, @code{break} sets a breakpoint at
3295 the next instruction to be executed in the selected stack frame
3296 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3297 innermost, this makes your program stop as soon as control
3298 returns to that frame. This is similar to the effect of a
3299 @code{finish} command in the frame inside the selected frame---except
3300 that @code{finish} does not leave an active breakpoint. If you use
3301 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3302 the next time it reaches the current location; this may be useful
3305 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3306 least one instruction has been executed. If it did not do this, you
3307 would be unable to proceed past a breakpoint without first disabling the
3308 breakpoint. This rule applies whether or not the breakpoint already
3309 existed when your program stopped.
3311 @item break @dots{} if @var{cond}
3312 Set a breakpoint with condition @var{cond}; evaluate the expression
3313 @var{cond} each time the breakpoint is reached, and stop only if the
3314 value is nonzero---that is, if @var{cond} evaluates as true.
3315 @samp{@dots{}} stands for one of the possible arguments described
3316 above (or no argument) specifying where to break. @xref{Conditions,
3317 ,Break Conditions}, for more information on breakpoint conditions.
3320 @item tbreak @var{args}
3321 Set a breakpoint enabled only for one stop. @var{args} are the
3322 same as for the @code{break} command, and the breakpoint is set in the same
3323 way, but the breakpoint is automatically deleted after the first time your
3324 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3327 @cindex hardware breakpoints
3328 @item hbreak @var{args}
3329 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3330 @code{break} command and the breakpoint is set in the same way, but the
3331 breakpoint requires hardware support and some target hardware may not
3332 have this support. The main purpose of this is EPROM/ROM code
3333 debugging, so you can set a breakpoint at an instruction without
3334 changing the instruction. This can be used with the new trap-generation
3335 provided by SPARClite DSU and most x86-based targets. These targets
3336 will generate traps when a program accesses some data or instruction
3337 address that is assigned to the debug registers. However the hardware
3338 breakpoint registers can take a limited number of breakpoints. For
3339 example, on the DSU, only two data breakpoints can be set at a time, and
3340 @value{GDBN} will reject this command if more than two are used. Delete
3341 or disable unused hardware breakpoints before setting new ones
3342 (@pxref{Disabling, ,Disabling Breakpoints}).
3343 @xref{Conditions, ,Break Conditions}.
3344 For remote targets, you can restrict the number of hardware
3345 breakpoints @value{GDBN} will use, see @ref{set remote
3346 hardware-breakpoint-limit}.
3349 @item thbreak @var{args}
3350 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3351 are the same as for the @code{hbreak} command and the breakpoint is set in
3352 the same way. However, like the @code{tbreak} command,
3353 the breakpoint is automatically deleted after the
3354 first time your program stops there. Also, like the @code{hbreak}
3355 command, the breakpoint requires hardware support and some target hardware
3356 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3357 See also @ref{Conditions, ,Break Conditions}.
3360 @cindex regular expression
3361 @cindex breakpoints at functions matching a regexp
3362 @cindex set breakpoints in many functions
3363 @item rbreak @var{regex}
3364 Set breakpoints on all functions matching the regular expression
3365 @var{regex}. This command sets an unconditional breakpoint on all
3366 matches, printing a list of all breakpoints it set. Once these
3367 breakpoints are set, they are treated just like the breakpoints set with
3368 the @code{break} command. You can delete them, disable them, or make
3369 them conditional the same way as any other breakpoint.
3371 The syntax of the regular expression is the standard one used with tools
3372 like @file{grep}. Note that this is different from the syntax used by
3373 shells, so for instance @code{foo*} matches all functions that include
3374 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3375 @code{.*} leading and trailing the regular expression you supply, so to
3376 match only functions that begin with @code{foo}, use @code{^foo}.
3378 @cindex non-member C@t{++} functions, set breakpoint in
3379 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3380 breakpoints on overloaded functions that are not members of any special
3383 @cindex set breakpoints on all functions
3384 The @code{rbreak} command can be used to set breakpoints in
3385 @strong{all} the functions in a program, like this:
3388 (@value{GDBP}) rbreak .
3391 @item rbreak @var{file}:@var{regex}
3392 If @code{rbreak} is called with a filename qualification, it limits
3393 the search for functions matching the given regular expression to the
3394 specified @var{file}. This can be used, for example, to set breakpoints on
3395 every function in a given file:
3398 (@value{GDBP}) rbreak file.c:.
3401 The colon separating the filename qualifier from the regex may
3402 optionally be surrounded by spaces.
3404 @kindex info breakpoints
3405 @cindex @code{$_} and @code{info breakpoints}
3406 @item info breakpoints @r{[}@var{n}@r{]}
3407 @itemx info break @r{[}@var{n}@r{]}
3408 Print a table of all breakpoints, watchpoints, and catchpoints set and
3409 not deleted. Optional argument @var{n} means print information only
3410 about the specified breakpoint (or watchpoint or catchpoint). For
3411 each breakpoint, following columns are printed:
3414 @item Breakpoint Numbers
3416 Breakpoint, watchpoint, or catchpoint.
3418 Whether the breakpoint is marked to be disabled or deleted when hit.
3419 @item Enabled or Disabled
3420 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3421 that are not enabled.
3423 Where the breakpoint is in your program, as a memory address. For a
3424 pending breakpoint whose address is not yet known, this field will
3425 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3426 library that has the symbol or line referred by breakpoint is loaded.
3427 See below for details. A breakpoint with several locations will
3428 have @samp{<MULTIPLE>} in this field---see below for details.
3430 Where the breakpoint is in the source for your program, as a file and
3431 line number. For a pending breakpoint, the original string passed to
3432 the breakpoint command will be listed as it cannot be resolved until
3433 the appropriate shared library is loaded in the future.
3437 If a breakpoint is conditional, @code{info break} shows the condition on
3438 the line following the affected breakpoint; breakpoint commands, if any,
3439 are listed after that. A pending breakpoint is allowed to have a condition
3440 specified for it. The condition is not parsed for validity until a shared
3441 library is loaded that allows the pending breakpoint to resolve to a
3445 @code{info break} with a breakpoint
3446 number @var{n} as argument lists only that breakpoint. The
3447 convenience variable @code{$_} and the default examining-address for
3448 the @code{x} command are set to the address of the last breakpoint
3449 listed (@pxref{Memory, ,Examining Memory}).
3452 @code{info break} displays a count of the number of times the breakpoint
3453 has been hit. This is especially useful in conjunction with the
3454 @code{ignore} command. You can ignore a large number of breakpoint
3455 hits, look at the breakpoint info to see how many times the breakpoint
3456 was hit, and then run again, ignoring one less than that number. This
3457 will get you quickly to the last hit of that breakpoint.
3460 @value{GDBN} allows you to set any number of breakpoints at the same place in
3461 your program. There is nothing silly or meaningless about this. When
3462 the breakpoints are conditional, this is even useful
3463 (@pxref{Conditions, ,Break Conditions}).
3465 @cindex multiple locations, breakpoints
3466 @cindex breakpoints, multiple locations
3467 It is possible that a breakpoint corresponds to several locations
3468 in your program. Examples of this situation are:
3472 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3473 instances of the function body, used in different cases.
3476 For a C@t{++} template function, a given line in the function can
3477 correspond to any number of instantiations.
3480 For an inlined function, a given source line can correspond to
3481 several places where that function is inlined.
3484 In all those cases, @value{GDBN} will insert a breakpoint at all
3485 the relevant locations@footnote{
3486 As of this writing, multiple-location breakpoints work only if there's
3487 line number information for all the locations. This means that they
3488 will generally not work in system libraries, unless you have debug
3489 info with line numbers for them.}.
3491 A breakpoint with multiple locations is displayed in the breakpoint
3492 table using several rows---one header row, followed by one row for
3493 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3494 address column. The rows for individual locations contain the actual
3495 addresses for locations, and show the functions to which those
3496 locations belong. The number column for a location is of the form
3497 @var{breakpoint-number}.@var{location-number}.
3502 Num Type Disp Enb Address What
3503 1 breakpoint keep y <MULTIPLE>
3505 breakpoint already hit 1 time
3506 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3507 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3510 Each location can be individually enabled or disabled by passing
3511 @var{breakpoint-number}.@var{location-number} as argument to the
3512 @code{enable} and @code{disable} commands. Note that you cannot
3513 delete the individual locations from the list, you can only delete the
3514 entire list of locations that belong to their parent breakpoint (with
3515 the @kbd{delete @var{num}} command, where @var{num} is the number of
3516 the parent breakpoint, 1 in the above example). Disabling or enabling
3517 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3518 that belong to that breakpoint.
3520 @cindex pending breakpoints
3521 It's quite common to have a breakpoint inside a shared library.
3522 Shared libraries can be loaded and unloaded explicitly,
3523 and possibly repeatedly, as the program is executed. To support
3524 this use case, @value{GDBN} updates breakpoint locations whenever
3525 any shared library is loaded or unloaded. Typically, you would
3526 set a breakpoint in a shared library at the beginning of your
3527 debugging session, when the library is not loaded, and when the
3528 symbols from the library are not available. When you try to set
3529 breakpoint, @value{GDBN} will ask you if you want to set
3530 a so called @dfn{pending breakpoint}---breakpoint whose address
3531 is not yet resolved.
3533 After the program is run, whenever a new shared library is loaded,
3534 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3535 shared library contains the symbol or line referred to by some
3536 pending breakpoint, that breakpoint is resolved and becomes an
3537 ordinary breakpoint. When a library is unloaded, all breakpoints
3538 that refer to its symbols or source lines become pending again.
3540 This logic works for breakpoints with multiple locations, too. For
3541 example, if you have a breakpoint in a C@t{++} template function, and
3542 a newly loaded shared library has an instantiation of that template,
3543 a new location is added to the list of locations for the breakpoint.
3545 Except for having unresolved address, pending breakpoints do not
3546 differ from regular breakpoints. You can set conditions or commands,
3547 enable and disable them and perform other breakpoint operations.
3549 @value{GDBN} provides some additional commands for controlling what
3550 happens when the @samp{break} command cannot resolve breakpoint
3551 address specification to an address:
3553 @kindex set breakpoint pending
3554 @kindex show breakpoint pending
3556 @item set breakpoint pending auto
3557 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3558 location, it queries you whether a pending breakpoint should be created.
3560 @item set breakpoint pending on
3561 This indicates that an unrecognized breakpoint location should automatically
3562 result in a pending breakpoint being created.
3564 @item set breakpoint pending off
3565 This indicates that pending breakpoints are not to be created. Any
3566 unrecognized breakpoint location results in an error. This setting does
3567 not affect any pending breakpoints previously created.
3569 @item show breakpoint pending
3570 Show the current behavior setting for creating pending breakpoints.
3573 The settings above only affect the @code{break} command and its
3574 variants. Once breakpoint is set, it will be automatically updated
3575 as shared libraries are loaded and unloaded.
3577 @cindex automatic hardware breakpoints
3578 For some targets, @value{GDBN} can automatically decide if hardware or
3579 software breakpoints should be used, depending on whether the
3580 breakpoint address is read-only or read-write. This applies to
3581 breakpoints set with the @code{break} command as well as to internal
3582 breakpoints set by commands like @code{next} and @code{finish}. For
3583 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3586 You can control this automatic behaviour with the following commands::
3588 @kindex set breakpoint auto-hw
3589 @kindex show breakpoint auto-hw
3591 @item set breakpoint auto-hw on
3592 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3593 will try to use the target memory map to decide if software or hardware
3594 breakpoint must be used.
3596 @item set breakpoint auto-hw off
3597 This indicates @value{GDBN} should not automatically select breakpoint
3598 type. If the target provides a memory map, @value{GDBN} will warn when
3599 trying to set software breakpoint at a read-only address.
3602 @value{GDBN} normally implements breakpoints by replacing the program code
3603 at the breakpoint address with a special instruction, which, when
3604 executed, given control to the debugger. By default, the program
3605 code is so modified only when the program is resumed. As soon as
3606 the program stops, @value{GDBN} restores the original instructions. This
3607 behaviour guards against leaving breakpoints inserted in the
3608 target should gdb abrubptly disconnect. However, with slow remote
3609 targets, inserting and removing breakpoint can reduce the performance.
3610 This behavior can be controlled with the following commands::
3612 @kindex set breakpoint always-inserted
3613 @kindex show breakpoint always-inserted
3615 @item set breakpoint always-inserted off
3616 All breakpoints, including newly added by the user, are inserted in
3617 the target only when the target is resumed. All breakpoints are
3618 removed from the target when it stops.
3620 @item set breakpoint always-inserted on
3621 Causes all breakpoints to be inserted in the target at all times. If
3622 the user adds a new breakpoint, or changes an existing breakpoint, the
3623 breakpoints in the target are updated immediately. A breakpoint is
3624 removed from the target only when breakpoint itself is removed.
3626 @cindex non-stop mode, and @code{breakpoint always-inserted}
3627 @item set breakpoint always-inserted auto
3628 This is the default mode. If @value{GDBN} is controlling the inferior
3629 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3630 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3631 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3632 @code{breakpoint always-inserted} mode is off.
3635 @cindex negative breakpoint numbers
3636 @cindex internal @value{GDBN} breakpoints
3637 @value{GDBN} itself sometimes sets breakpoints in your program for
3638 special purposes, such as proper handling of @code{longjmp} (in C
3639 programs). These internal breakpoints are assigned negative numbers,
3640 starting with @code{-1}; @samp{info breakpoints} does not display them.
3641 You can see these breakpoints with the @value{GDBN} maintenance command
3642 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3645 @node Set Watchpoints
3646 @subsection Setting Watchpoints
3648 @cindex setting watchpoints
3649 You can use a watchpoint to stop execution whenever the value of an
3650 expression changes, without having to predict a particular place where
3651 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3652 The expression may be as simple as the value of a single variable, or
3653 as complex as many variables combined by operators. Examples include:
3657 A reference to the value of a single variable.
3660 An address cast to an appropriate data type. For example,
3661 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3662 address (assuming an @code{int} occupies 4 bytes).
3665 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3666 expression can use any operators valid in the program's native
3667 language (@pxref{Languages}).
3670 You can set a watchpoint on an expression even if the expression can
3671 not be evaluated yet. For instance, you can set a watchpoint on
3672 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3673 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3674 the expression produces a valid value. If the expression becomes
3675 valid in some other way than changing a variable (e.g.@: if the memory
3676 pointed to by @samp{*global_ptr} becomes readable as the result of a
3677 @code{malloc} call), @value{GDBN} may not stop until the next time
3678 the expression changes.
3680 @cindex software watchpoints
3681 @cindex hardware watchpoints
3682 Depending on your system, watchpoints may be implemented in software or
3683 hardware. @value{GDBN} does software watchpointing by single-stepping your
3684 program and testing the variable's value each time, which is hundreds of
3685 times slower than normal execution. (But this may still be worth it, to
3686 catch errors where you have no clue what part of your program is the
3689 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3690 x86-based targets, @value{GDBN} includes support for hardware
3691 watchpoints, which do not slow down the running of your program.
3695 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3696 Set a watchpoint for an expression. @value{GDBN} will break when the
3697 expression @var{expr} is written into by the program and its value
3698 changes. The simplest (and the most popular) use of this command is
3699 to watch the value of a single variable:
3702 (@value{GDBP}) watch foo
3705 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3706 clause, @value{GDBN} breaks only when the thread identified by
3707 @var{threadnum} changes the value of @var{expr}. If any other threads
3708 change the value of @var{expr}, @value{GDBN} will not break. Note
3709 that watchpoints restricted to a single thread in this way only work
3710 with Hardware Watchpoints.
3713 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3714 Set a watchpoint that will break when the value of @var{expr} is read
3718 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3719 Set a watchpoint that will break when @var{expr} is either read from
3720 or written into by the program.
3722 @kindex info watchpoints @r{[}@var{n}@r{]}
3723 @item info watchpoints
3724 This command prints a list of watchpoints, using the same format as
3725 @code{info break} (@pxref{Set Breaks}).
3728 If you watch for a change in a numerically entered address you need to
3729 dereference it, as the address itself is just a constant number which will
3730 never change. @value{GDBN} refuses to create a watchpoint that watches
3731 a never-changing value:
3734 (@value{GDBP}) watch 0x600850
3735 Cannot watch constant value 0x600850.
3736 (@value{GDBP}) watch *(int *) 0x600850
3737 Watchpoint 1: *(int *) 6293584
3740 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3741 watchpoints execute very quickly, and the debugger reports a change in
3742 value at the exact instruction where the change occurs. If @value{GDBN}
3743 cannot set a hardware watchpoint, it sets a software watchpoint, which
3744 executes more slowly and reports the change in value at the next
3745 @emph{statement}, not the instruction, after the change occurs.
3747 @cindex use only software watchpoints
3748 You can force @value{GDBN} to use only software watchpoints with the
3749 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3750 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3751 the underlying system supports them. (Note that hardware-assisted
3752 watchpoints that were set @emph{before} setting
3753 @code{can-use-hw-watchpoints} to zero will still use the hardware
3754 mechanism of watching expression values.)
3757 @item set can-use-hw-watchpoints
3758 @kindex set can-use-hw-watchpoints
3759 Set whether or not to use hardware watchpoints.
3761 @item show can-use-hw-watchpoints
3762 @kindex show can-use-hw-watchpoints
3763 Show the current mode of using hardware watchpoints.
3766 For remote targets, you can restrict the number of hardware
3767 watchpoints @value{GDBN} will use, see @ref{set remote
3768 hardware-breakpoint-limit}.
3770 When you issue the @code{watch} command, @value{GDBN} reports
3773 Hardware watchpoint @var{num}: @var{expr}
3777 if it was able to set a hardware watchpoint.
3779 Currently, the @code{awatch} and @code{rwatch} commands can only set
3780 hardware watchpoints, because accesses to data that don't change the
3781 value of the watched expression cannot be detected without examining
3782 every instruction as it is being executed, and @value{GDBN} does not do
3783 that currently. If @value{GDBN} finds that it is unable to set a
3784 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3785 will print a message like this:
3788 Expression cannot be implemented with read/access watchpoint.
3791 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3792 data type of the watched expression is wider than what a hardware
3793 watchpoint on the target machine can handle. For example, some systems
3794 can only watch regions that are up to 4 bytes wide; on such systems you
3795 cannot set hardware watchpoints for an expression that yields a
3796 double-precision floating-point number (which is typically 8 bytes
3797 wide). As a work-around, it might be possible to break the large region
3798 into a series of smaller ones and watch them with separate watchpoints.
3800 If you set too many hardware watchpoints, @value{GDBN} might be unable
3801 to insert all of them when you resume the execution of your program.
3802 Since the precise number of active watchpoints is unknown until such
3803 time as the program is about to be resumed, @value{GDBN} might not be
3804 able to warn you about this when you set the watchpoints, and the
3805 warning will be printed only when the program is resumed:
3808 Hardware watchpoint @var{num}: Could not insert watchpoint
3812 If this happens, delete or disable some of the watchpoints.
3814 Watching complex expressions that reference many variables can also
3815 exhaust the resources available for hardware-assisted watchpoints.
3816 That's because @value{GDBN} needs to watch every variable in the
3817 expression with separately allocated resources.
3819 If you call a function interactively using @code{print} or @code{call},
3820 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3821 kind of breakpoint or the call completes.
3823 @value{GDBN} automatically deletes watchpoints that watch local
3824 (automatic) variables, or expressions that involve such variables, when
3825 they go out of scope, that is, when the execution leaves the block in
3826 which these variables were defined. In particular, when the program
3827 being debugged terminates, @emph{all} local variables go out of scope,
3828 and so only watchpoints that watch global variables remain set. If you
3829 rerun the program, you will need to set all such watchpoints again. One
3830 way of doing that would be to set a code breakpoint at the entry to the
3831 @code{main} function and when it breaks, set all the watchpoints.
3833 @cindex watchpoints and threads
3834 @cindex threads and watchpoints
3835 In multi-threaded programs, watchpoints will detect changes to the
3836 watched expression from every thread.
3839 @emph{Warning:} In multi-threaded programs, software watchpoints
3840 have only limited usefulness. If @value{GDBN} creates a software
3841 watchpoint, it can only watch the value of an expression @emph{in a
3842 single thread}. If you are confident that the expression can only
3843 change due to the current thread's activity (and if you are also
3844 confident that no other thread can become current), then you can use
3845 software watchpoints as usual. However, @value{GDBN} may not notice
3846 when a non-current thread's activity changes the expression. (Hardware
3847 watchpoints, in contrast, watch an expression in all threads.)
3850 @xref{set remote hardware-watchpoint-limit}.
3852 @node Set Catchpoints
3853 @subsection Setting Catchpoints
3854 @cindex catchpoints, setting
3855 @cindex exception handlers
3856 @cindex event handling
3858 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3859 kinds of program events, such as C@t{++} exceptions or the loading of a
3860 shared library. Use the @code{catch} command to set a catchpoint.
3864 @item catch @var{event}
3865 Stop when @var{event} occurs. @var{event} can be any of the following:
3868 @cindex stop on C@t{++} exceptions
3869 The throwing of a C@t{++} exception.
3872 The catching of a C@t{++} exception.
3875 @cindex Ada exception catching
3876 @cindex catch Ada exceptions
3877 An Ada exception being raised. If an exception name is specified
3878 at the end of the command (eg @code{catch exception Program_Error}),
3879 the debugger will stop only when this specific exception is raised.
3880 Otherwise, the debugger stops execution when any Ada exception is raised.
3882 When inserting an exception catchpoint on a user-defined exception whose
3883 name is identical to one of the exceptions defined by the language, the
3884 fully qualified name must be used as the exception name. Otherwise,
3885 @value{GDBN} will assume that it should stop on the pre-defined exception
3886 rather than the user-defined one. For instance, assuming an exception
3887 called @code{Constraint_Error} is defined in package @code{Pck}, then
3888 the command to use to catch such exceptions is @kbd{catch exception
3889 Pck.Constraint_Error}.
3891 @item exception unhandled
3892 An exception that was raised but is not handled by the program.
3895 A failed Ada assertion.
3898 @cindex break on fork/exec
3899 A call to @code{exec}. This is currently only available for HP-UX
3903 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3904 @cindex break on a system call.
3905 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3906 syscall is a mechanism for application programs to request a service
3907 from the operating system (OS) or one of the OS system services.
3908 @value{GDBN} can catch some or all of the syscalls issued by the
3909 debuggee, and show the related information for each syscall. If no
3910 argument is specified, calls to and returns from all system calls
3913 @var{name} can be any system call name that is valid for the
3914 underlying OS. Just what syscalls are valid depends on the OS. On
3915 GNU and Unix systems, you can find the full list of valid syscall
3916 names on @file{/usr/include/asm/unistd.h}.
3918 @c For MS-Windows, the syscall names and the corresponding numbers
3919 @c can be found, e.g., on this URL:
3920 @c http://www.metasploit.com/users/opcode/syscalls.html
3921 @c but we don't support Windows syscalls yet.
3923 Normally, @value{GDBN} knows in advance which syscalls are valid for
3924 each OS, so you can use the @value{GDBN} command-line completion
3925 facilities (@pxref{Completion,, command completion}) to list the
3928 You may also specify the system call numerically. A syscall's
3929 number is the value passed to the OS's syscall dispatcher to
3930 identify the requested service. When you specify the syscall by its
3931 name, @value{GDBN} uses its database of syscalls to convert the name
3932 into the corresponding numeric code, but using the number directly
3933 may be useful if @value{GDBN}'s database does not have the complete
3934 list of syscalls on your system (e.g., because @value{GDBN} lags
3935 behind the OS upgrades).
3937 The example below illustrates how this command works if you don't provide
3941 (@value{GDBP}) catch syscall
3942 Catchpoint 1 (syscall)
3944 Starting program: /tmp/catch-syscall
3946 Catchpoint 1 (call to syscall 'close'), \
3947 0xffffe424 in __kernel_vsyscall ()
3951 Catchpoint 1 (returned from syscall 'close'), \
3952 0xffffe424 in __kernel_vsyscall ()
3956 Here is an example of catching a system call by name:
3959 (@value{GDBP}) catch syscall chroot
3960 Catchpoint 1 (syscall 'chroot' [61])
3962 Starting program: /tmp/catch-syscall
3964 Catchpoint 1 (call to syscall 'chroot'), \
3965 0xffffe424 in __kernel_vsyscall ()
3969 Catchpoint 1 (returned from syscall 'chroot'), \
3970 0xffffe424 in __kernel_vsyscall ()
3974 An example of specifying a system call numerically. In the case
3975 below, the syscall number has a corresponding entry in the XML
3976 file, so @value{GDBN} finds its name and prints it:
3979 (@value{GDBP}) catch syscall 252
3980 Catchpoint 1 (syscall(s) 'exit_group')
3982 Starting program: /tmp/catch-syscall
3984 Catchpoint 1 (call to syscall 'exit_group'), \
3985 0xffffe424 in __kernel_vsyscall ()
3989 Program exited normally.
3993 However, there can be situations when there is no corresponding name
3994 in XML file for that syscall number. In this case, @value{GDBN} prints
3995 a warning message saying that it was not able to find the syscall name,
3996 but the catchpoint will be set anyway. See the example below:
3999 (@value{GDBP}) catch syscall 764
4000 warning: The number '764' does not represent a known syscall.
4001 Catchpoint 2 (syscall 764)
4005 If you configure @value{GDBN} using the @samp{--without-expat} option,
4006 it will not be able to display syscall names. Also, if your
4007 architecture does not have an XML file describing its system calls,
4008 you will not be able to see the syscall names. It is important to
4009 notice that these two features are used for accessing the syscall
4010 name database. In either case, you will see a warning like this:
4013 (@value{GDBP}) catch syscall
4014 warning: Could not open "syscalls/i386-linux.xml"
4015 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4016 GDB will not be able to display syscall names.
4017 Catchpoint 1 (syscall)
4021 Of course, the file name will change depending on your architecture and system.
4023 Still using the example above, you can also try to catch a syscall by its
4024 number. In this case, you would see something like:
4027 (@value{GDBP}) catch syscall 252
4028 Catchpoint 1 (syscall(s) 252)
4031 Again, in this case @value{GDBN} would not be able to display syscall's names.
4034 A call to @code{fork}. This is currently only available for HP-UX
4038 A call to @code{vfork}. This is currently only available for HP-UX
4043 @item tcatch @var{event}
4044 Set a catchpoint that is enabled only for one stop. The catchpoint is
4045 automatically deleted after the first time the event is caught.
4049 Use the @code{info break} command to list the current catchpoints.
4051 There are currently some limitations to C@t{++} exception handling
4052 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4056 If you call a function interactively, @value{GDBN} normally returns
4057 control to you when the function has finished executing. If the call
4058 raises an exception, however, the call may bypass the mechanism that
4059 returns control to you and cause your program either to abort or to
4060 simply continue running until it hits a breakpoint, catches a signal
4061 that @value{GDBN} is listening for, or exits. This is the case even if
4062 you set a catchpoint for the exception; catchpoints on exceptions are
4063 disabled within interactive calls.
4066 You cannot raise an exception interactively.
4069 You cannot install an exception handler interactively.
4072 @cindex raise exceptions
4073 Sometimes @code{catch} is not the best way to debug exception handling:
4074 if you need to know exactly where an exception is raised, it is better to
4075 stop @emph{before} the exception handler is called, since that way you
4076 can see the stack before any unwinding takes place. If you set a
4077 breakpoint in an exception handler instead, it may not be easy to find
4078 out where the exception was raised.
4080 To stop just before an exception handler is called, you need some
4081 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4082 raised by calling a library function named @code{__raise_exception}
4083 which has the following ANSI C interface:
4086 /* @var{addr} is where the exception identifier is stored.
4087 @var{id} is the exception identifier. */
4088 void __raise_exception (void **addr, void *id);
4092 To make the debugger catch all exceptions before any stack
4093 unwinding takes place, set a breakpoint on @code{__raise_exception}
4094 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4096 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4097 that depends on the value of @var{id}, you can stop your program when
4098 a specific exception is raised. You can use multiple conditional
4099 breakpoints to stop your program when any of a number of exceptions are
4104 @subsection Deleting Breakpoints
4106 @cindex clearing breakpoints, watchpoints, catchpoints
4107 @cindex deleting breakpoints, watchpoints, catchpoints
4108 It is often necessary to eliminate a breakpoint, watchpoint, or
4109 catchpoint once it has done its job and you no longer want your program
4110 to stop there. This is called @dfn{deleting} the breakpoint. A
4111 breakpoint that has been deleted no longer exists; it is forgotten.
4113 With the @code{clear} command you can delete breakpoints according to
4114 where they are in your program. With the @code{delete} command you can
4115 delete individual breakpoints, watchpoints, or catchpoints by specifying
4116 their breakpoint numbers.
4118 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4119 automatically ignores breakpoints on the first instruction to be executed
4120 when you continue execution without changing the execution address.
4125 Delete any breakpoints at the next instruction to be executed in the
4126 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4127 the innermost frame is selected, this is a good way to delete a
4128 breakpoint where your program just stopped.
4130 @item clear @var{location}
4131 Delete any breakpoints set at the specified @var{location}.
4132 @xref{Specify Location}, for the various forms of @var{location}; the
4133 most useful ones are listed below:
4136 @item clear @var{function}
4137 @itemx clear @var{filename}:@var{function}
4138 Delete any breakpoints set at entry to the named @var{function}.
4140 @item clear @var{linenum}
4141 @itemx clear @var{filename}:@var{linenum}
4142 Delete any breakpoints set at or within the code of the specified
4143 @var{linenum} of the specified @var{filename}.
4146 @cindex delete breakpoints
4148 @kindex d @r{(@code{delete})}
4149 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4150 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4151 ranges specified as arguments. If no argument is specified, delete all
4152 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4153 confirm off}). You can abbreviate this command as @code{d}.
4157 @subsection Disabling Breakpoints
4159 @cindex enable/disable a breakpoint
4160 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4161 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4162 it had been deleted, but remembers the information on the breakpoint so
4163 that you can @dfn{enable} it again later.
4165 You disable and enable breakpoints, watchpoints, and catchpoints with
4166 the @code{enable} and @code{disable} commands, optionally specifying
4167 one or more breakpoint numbers as arguments. Use @code{info break} to
4168 print a list of all breakpoints, watchpoints, and catchpoints if you
4169 do not know which numbers to use.
4171 Disabling and enabling a breakpoint that has multiple locations
4172 affects all of its locations.
4174 A breakpoint, watchpoint, or catchpoint can have any of four different
4175 states of enablement:
4179 Enabled. The breakpoint stops your program. A breakpoint set
4180 with the @code{break} command starts out in this state.
4182 Disabled. The breakpoint has no effect on your program.
4184 Enabled once. The breakpoint stops your program, but then becomes
4187 Enabled for deletion. The breakpoint stops your program, but
4188 immediately after it does so it is deleted permanently. A breakpoint
4189 set with the @code{tbreak} command starts out in this state.
4192 You can use the following commands to enable or disable breakpoints,
4193 watchpoints, and catchpoints:
4197 @kindex dis @r{(@code{disable})}
4198 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4199 Disable the specified breakpoints---or all breakpoints, if none are
4200 listed. A disabled breakpoint has no effect but is not forgotten. All
4201 options such as ignore-counts, conditions and commands are remembered in
4202 case the breakpoint is enabled again later. You may abbreviate
4203 @code{disable} as @code{dis}.
4206 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4207 Enable the specified breakpoints (or all defined breakpoints). They
4208 become effective once again in stopping your program.
4210 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4211 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4212 of these breakpoints immediately after stopping your program.
4214 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4215 Enable the specified breakpoints to work once, then die. @value{GDBN}
4216 deletes any of these breakpoints as soon as your program stops there.
4217 Breakpoints set by the @code{tbreak} command start out in this state.
4220 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4221 @c confusing: tbreak is also initially enabled.
4222 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4223 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4224 subsequently, they become disabled or enabled only when you use one of
4225 the commands above. (The command @code{until} can set and delete a
4226 breakpoint of its own, but it does not change the state of your other
4227 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4231 @subsection Break Conditions
4232 @cindex conditional breakpoints
4233 @cindex breakpoint conditions
4235 @c FIXME what is scope of break condition expr? Context where wanted?
4236 @c in particular for a watchpoint?
4237 The simplest sort of breakpoint breaks every time your program reaches a
4238 specified place. You can also specify a @dfn{condition} for a
4239 breakpoint. A condition is just a Boolean expression in your
4240 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4241 a condition evaluates the expression each time your program reaches it,
4242 and your program stops only if the condition is @emph{true}.
4244 This is the converse of using assertions for program validation; in that
4245 situation, you want to stop when the assertion is violated---that is,
4246 when the condition is false. In C, if you want to test an assertion expressed
4247 by the condition @var{assert}, you should set the condition
4248 @samp{! @var{assert}} on the appropriate breakpoint.
4250 Conditions are also accepted for watchpoints; you may not need them,
4251 since a watchpoint is inspecting the value of an expression anyhow---but
4252 it might be simpler, say, to just set a watchpoint on a variable name,
4253 and specify a condition that tests whether the new value is an interesting
4256 Break conditions can have side effects, and may even call functions in
4257 your program. This can be useful, for example, to activate functions
4258 that log program progress, or to use your own print functions to
4259 format special data structures. The effects are completely predictable
4260 unless there is another enabled breakpoint at the same address. (In
4261 that case, @value{GDBN} might see the other breakpoint first and stop your
4262 program without checking the condition of this one.) Note that
4263 breakpoint commands are usually more convenient and flexible than break
4265 purpose of performing side effects when a breakpoint is reached
4266 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4268 Break conditions can be specified when a breakpoint is set, by using
4269 @samp{if} in the arguments to the @code{break} command. @xref{Set
4270 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4271 with the @code{condition} command.
4273 You can also use the @code{if} keyword with the @code{watch} command.
4274 The @code{catch} command does not recognize the @code{if} keyword;
4275 @code{condition} is the only way to impose a further condition on a
4280 @item condition @var{bnum} @var{expression}
4281 Specify @var{expression} as the break condition for breakpoint,
4282 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4283 breakpoint @var{bnum} stops your program only if the value of
4284 @var{expression} is true (nonzero, in C). When you use
4285 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4286 syntactic correctness, and to determine whether symbols in it have
4287 referents in the context of your breakpoint. If @var{expression} uses
4288 symbols not referenced in the context of the breakpoint, @value{GDBN}
4289 prints an error message:
4292 No symbol "foo" in current context.
4297 not actually evaluate @var{expression} at the time the @code{condition}
4298 command (or a command that sets a breakpoint with a condition, like
4299 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4301 @item condition @var{bnum}
4302 Remove the condition from breakpoint number @var{bnum}. It becomes
4303 an ordinary unconditional breakpoint.
4306 @cindex ignore count (of breakpoint)
4307 A special case of a breakpoint condition is to stop only when the
4308 breakpoint has been reached a certain number of times. This is so
4309 useful that there is a special way to do it, using the @dfn{ignore
4310 count} of the breakpoint. Every breakpoint has an ignore count, which
4311 is an integer. Most of the time, the ignore count is zero, and
4312 therefore has no effect. But if your program reaches a breakpoint whose
4313 ignore count is positive, then instead of stopping, it just decrements
4314 the ignore count by one and continues. As a result, if the ignore count
4315 value is @var{n}, the breakpoint does not stop the next @var{n} times
4316 your program reaches it.
4320 @item ignore @var{bnum} @var{count}
4321 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4322 The next @var{count} times the breakpoint is reached, your program's
4323 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4326 To make the breakpoint stop the next time it is reached, specify
4329 When you use @code{continue} to resume execution of your program from a
4330 breakpoint, you can specify an ignore count directly as an argument to
4331 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4332 Stepping,,Continuing and Stepping}.
4334 If a breakpoint has a positive ignore count and a condition, the
4335 condition is not checked. Once the ignore count reaches zero,
4336 @value{GDBN} resumes checking the condition.
4338 You could achieve the effect of the ignore count with a condition such
4339 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4340 is decremented each time. @xref{Convenience Vars, ,Convenience
4344 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4347 @node Break Commands
4348 @subsection Breakpoint Command Lists
4350 @cindex breakpoint commands
4351 You can give any breakpoint (or watchpoint or catchpoint) a series of
4352 commands to execute when your program stops due to that breakpoint. For
4353 example, you might want to print the values of certain expressions, or
4354 enable other breakpoints.
4358 @kindex end@r{ (breakpoint commands)}
4359 @item commands @r{[}@var{range}@dots{}@r{]}
4360 @itemx @dots{} @var{command-list} @dots{}
4362 Specify a list of commands for the given breakpoints. The commands
4363 themselves appear on the following lines. Type a line containing just
4364 @code{end} to terminate the commands.
4366 To remove all commands from a breakpoint, type @code{commands} and
4367 follow it immediately with @code{end}; that is, give no commands.
4369 With no argument, @code{commands} refers to the last breakpoint,
4370 watchpoint, or catchpoint set (not to the breakpoint most recently
4371 encountered). If the most recent breakpoints were set with a single
4372 command, then the @code{commands} will apply to all the breakpoints
4373 set by that command. This applies to breakpoints set by
4374 @code{rbreak}, and also applies when a single @code{break} command
4375 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4379 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4380 disabled within a @var{command-list}.
4382 You can use breakpoint commands to start your program up again. Simply
4383 use the @code{continue} command, or @code{step}, or any other command
4384 that resumes execution.
4386 Any other commands in the command list, after a command that resumes
4387 execution, are ignored. This is because any time you resume execution
4388 (even with a simple @code{next} or @code{step}), you may encounter
4389 another breakpoint---which could have its own command list, leading to
4390 ambiguities about which list to execute.
4393 If the first command you specify in a command list is @code{silent}, the
4394 usual message about stopping at a breakpoint is not printed. This may
4395 be desirable for breakpoints that are to print a specific message and
4396 then continue. If none of the remaining commands print anything, you
4397 see no sign that the breakpoint was reached. @code{silent} is
4398 meaningful only at the beginning of a breakpoint command list.
4400 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4401 print precisely controlled output, and are often useful in silent
4402 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4404 For example, here is how you could use breakpoint commands to print the
4405 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4411 printf "x is %d\n",x
4416 One application for breakpoint commands is to compensate for one bug so
4417 you can test for another. Put a breakpoint just after the erroneous line
4418 of code, give it a condition to detect the case in which something
4419 erroneous has been done, and give it commands to assign correct values
4420 to any variables that need them. End with the @code{continue} command
4421 so that your program does not stop, and start with the @code{silent}
4422 command so that no output is produced. Here is an example:
4433 @node Save Breakpoints
4434 @subsection How to save breakpoints to a file
4436 To save breakpoint definitions to a file use the @w{@code{save
4437 breakpoints}} command.
4440 @kindex save breakpoints
4441 @cindex save breakpoints to a file for future sessions
4442 @item save breakpoints [@var{filename}]
4443 This command saves all current breakpoint definitions together with
4444 their commands and ignore counts, into a file @file{@var{filename}}
4445 suitable for use in a later debugging session. This includes all
4446 types of breakpoints (breakpoints, watchpoints, catchpoints,
4447 tracepoints). To read the saved breakpoint definitions, use the
4448 @code{source} command (@pxref{Command Files}). Note that watchpoints
4449 with expressions involving local variables may fail to be recreated
4450 because it may not be possible to access the context where the
4451 watchpoint is valid anymore. Because the saved breakpoint definitions
4452 are simply a sequence of @value{GDBN} commands that recreate the
4453 breakpoints, you can edit the file in your favorite editing program,
4454 and remove the breakpoint definitions you're not interested in, or
4455 that can no longer be recreated.
4458 @c @ifclear BARETARGET
4459 @node Error in Breakpoints
4460 @subsection ``Cannot insert breakpoints''
4462 If you request too many active hardware-assisted breakpoints and
4463 watchpoints, you will see this error message:
4465 @c FIXME: the precise wording of this message may change; the relevant
4466 @c source change is not committed yet (Sep 3, 1999).
4468 Stopped; cannot insert breakpoints.
4469 You may have requested too many hardware breakpoints and watchpoints.
4473 This message is printed when you attempt to resume the program, since
4474 only then @value{GDBN} knows exactly how many hardware breakpoints and
4475 watchpoints it needs to insert.
4477 When this message is printed, you need to disable or remove some of the
4478 hardware-assisted breakpoints and watchpoints, and then continue.
4480 @node Breakpoint-related Warnings
4481 @subsection ``Breakpoint address adjusted...''
4482 @cindex breakpoint address adjusted
4484 Some processor architectures place constraints on the addresses at
4485 which breakpoints may be placed. For architectures thus constrained,
4486 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4487 with the constraints dictated by the architecture.
4489 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4490 a VLIW architecture in which a number of RISC-like instructions may be
4491 bundled together for parallel execution. The FR-V architecture
4492 constrains the location of a breakpoint instruction within such a
4493 bundle to the instruction with the lowest address. @value{GDBN}
4494 honors this constraint by adjusting a breakpoint's address to the
4495 first in the bundle.
4497 It is not uncommon for optimized code to have bundles which contain
4498 instructions from different source statements, thus it may happen that
4499 a breakpoint's address will be adjusted from one source statement to
4500 another. Since this adjustment may significantly alter @value{GDBN}'s
4501 breakpoint related behavior from what the user expects, a warning is
4502 printed when the breakpoint is first set and also when the breakpoint
4505 A warning like the one below is printed when setting a breakpoint
4506 that's been subject to address adjustment:
4509 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4512 Such warnings are printed both for user settable and @value{GDBN}'s
4513 internal breakpoints. If you see one of these warnings, you should
4514 verify that a breakpoint set at the adjusted address will have the
4515 desired affect. If not, the breakpoint in question may be removed and
4516 other breakpoints may be set which will have the desired behavior.
4517 E.g., it may be sufficient to place the breakpoint at a later
4518 instruction. A conditional breakpoint may also be useful in some
4519 cases to prevent the breakpoint from triggering too often.
4521 @value{GDBN} will also issue a warning when stopping at one of these
4522 adjusted breakpoints:
4525 warning: Breakpoint 1 address previously adjusted from 0x00010414
4529 When this warning is encountered, it may be too late to take remedial
4530 action except in cases where the breakpoint is hit earlier or more
4531 frequently than expected.
4533 @node Continuing and Stepping
4534 @section Continuing and Stepping
4538 @cindex resuming execution
4539 @dfn{Continuing} means resuming program execution until your program
4540 completes normally. In contrast, @dfn{stepping} means executing just
4541 one more ``step'' of your program, where ``step'' may mean either one
4542 line of source code, or one machine instruction (depending on what
4543 particular command you use). Either when continuing or when stepping,
4544 your program may stop even sooner, due to a breakpoint or a signal. (If
4545 it stops due to a signal, you may want to use @code{handle}, or use
4546 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4550 @kindex c @r{(@code{continue})}
4551 @kindex fg @r{(resume foreground execution)}
4552 @item continue @r{[}@var{ignore-count}@r{]}
4553 @itemx c @r{[}@var{ignore-count}@r{]}
4554 @itemx fg @r{[}@var{ignore-count}@r{]}
4555 Resume program execution, at the address where your program last stopped;
4556 any breakpoints set at that address are bypassed. The optional argument
4557 @var{ignore-count} allows you to specify a further number of times to
4558 ignore a breakpoint at this location; its effect is like that of
4559 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4561 The argument @var{ignore-count} is meaningful only when your program
4562 stopped due to a breakpoint. At other times, the argument to
4563 @code{continue} is ignored.
4565 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4566 debugged program is deemed to be the foreground program) are provided
4567 purely for convenience, and have exactly the same behavior as
4571 To resume execution at a different place, you can use @code{return}
4572 (@pxref{Returning, ,Returning from a Function}) to go back to the
4573 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4574 Different Address}) to go to an arbitrary location in your program.
4576 A typical technique for using stepping is to set a breakpoint
4577 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4578 beginning of the function or the section of your program where a problem
4579 is believed to lie, run your program until it stops at that breakpoint,
4580 and then step through the suspect area, examining the variables that are
4581 interesting, until you see the problem happen.
4585 @kindex s @r{(@code{step})}
4587 Continue running your program until control reaches a different source
4588 line, then stop it and return control to @value{GDBN}. This command is
4589 abbreviated @code{s}.
4592 @c "without debugging information" is imprecise; actually "without line
4593 @c numbers in the debugging information". (gcc -g1 has debugging info but
4594 @c not line numbers). But it seems complex to try to make that
4595 @c distinction here.
4596 @emph{Warning:} If you use the @code{step} command while control is
4597 within a function that was compiled without debugging information,
4598 execution proceeds until control reaches a function that does have
4599 debugging information. Likewise, it will not step into a function which
4600 is compiled without debugging information. To step through functions
4601 without debugging information, use the @code{stepi} command, described
4605 The @code{step} command only stops at the first instruction of a source
4606 line. This prevents the multiple stops that could otherwise occur in
4607 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4608 to stop if a function that has debugging information is called within
4609 the line. In other words, @code{step} @emph{steps inside} any functions
4610 called within the line.
4612 Also, the @code{step} command only enters a function if there is line
4613 number information for the function. Otherwise it acts like the
4614 @code{next} command. This avoids problems when using @code{cc -gl}
4615 on MIPS machines. Previously, @code{step} entered subroutines if there
4616 was any debugging information about the routine.
4618 @item step @var{count}
4619 Continue running as in @code{step}, but do so @var{count} times. If a
4620 breakpoint is reached, or a signal not related to stepping occurs before
4621 @var{count} steps, stepping stops right away.
4624 @kindex n @r{(@code{next})}
4625 @item next @r{[}@var{count}@r{]}
4626 Continue to the next source line in the current (innermost) stack frame.
4627 This is similar to @code{step}, but function calls that appear within
4628 the line of code are executed without stopping. Execution stops when
4629 control reaches a different line of code at the original stack level
4630 that was executing when you gave the @code{next} command. This command
4631 is abbreviated @code{n}.
4633 An argument @var{count} is a repeat count, as for @code{step}.
4636 @c FIX ME!! Do we delete this, or is there a way it fits in with
4637 @c the following paragraph? --- Vctoria
4639 @c @code{next} within a function that lacks debugging information acts like
4640 @c @code{step}, but any function calls appearing within the code of the
4641 @c function are executed without stopping.
4643 The @code{next} command only stops at the first instruction of a
4644 source line. This prevents multiple stops that could otherwise occur in
4645 @code{switch} statements, @code{for} loops, etc.
4647 @kindex set step-mode
4649 @cindex functions without line info, and stepping
4650 @cindex stepping into functions with no line info
4651 @itemx set step-mode on
4652 The @code{set step-mode on} command causes the @code{step} command to
4653 stop at the first instruction of a function which contains no debug line
4654 information rather than stepping over it.
4656 This is useful in cases where you may be interested in inspecting the
4657 machine instructions of a function which has no symbolic info and do not
4658 want @value{GDBN} to automatically skip over this function.
4660 @item set step-mode off
4661 Causes the @code{step} command to step over any functions which contains no
4662 debug information. This is the default.
4664 @item show step-mode
4665 Show whether @value{GDBN} will stop in or step over functions without
4666 source line debug information.
4669 @kindex fin @r{(@code{finish})}
4671 Continue running until just after function in the selected stack frame
4672 returns. Print the returned value (if any). This command can be
4673 abbreviated as @code{fin}.
4675 Contrast this with the @code{return} command (@pxref{Returning,
4676 ,Returning from a Function}).
4679 @kindex u @r{(@code{until})}
4680 @cindex run until specified location
4683 Continue running until a source line past the current line, in the
4684 current stack frame, is reached. This command is used to avoid single
4685 stepping through a loop more than once. It is like the @code{next}
4686 command, except that when @code{until} encounters a jump, it
4687 automatically continues execution until the program counter is greater
4688 than the address of the jump.
4690 This means that when you reach the end of a loop after single stepping
4691 though it, @code{until} makes your program continue execution until it
4692 exits the loop. In contrast, a @code{next} command at the end of a loop
4693 simply steps back to the beginning of the loop, which forces you to step
4694 through the next iteration.
4696 @code{until} always stops your program if it attempts to exit the current
4699 @code{until} may produce somewhat counterintuitive results if the order
4700 of machine code does not match the order of the source lines. For
4701 example, in the following excerpt from a debugging session, the @code{f}
4702 (@code{frame}) command shows that execution is stopped at line
4703 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4707 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4709 (@value{GDBP}) until
4710 195 for ( ; argc > 0; NEXTARG) @{
4713 This happened because, for execution efficiency, the compiler had
4714 generated code for the loop closure test at the end, rather than the
4715 start, of the loop---even though the test in a C @code{for}-loop is
4716 written before the body of the loop. The @code{until} command appeared
4717 to step back to the beginning of the loop when it advanced to this
4718 expression; however, it has not really gone to an earlier
4719 statement---not in terms of the actual machine code.
4721 @code{until} with no argument works by means of single
4722 instruction stepping, and hence is slower than @code{until} with an
4725 @item until @var{location}
4726 @itemx u @var{location}
4727 Continue running your program until either the specified location is
4728 reached, or the current stack frame returns. @var{location} is any of
4729 the forms described in @ref{Specify Location}.
4730 This form of the command uses temporary breakpoints, and
4731 hence is quicker than @code{until} without an argument. The specified
4732 location is actually reached only if it is in the current frame. This
4733 implies that @code{until} can be used to skip over recursive function
4734 invocations. For instance in the code below, if the current location is
4735 line @code{96}, issuing @code{until 99} will execute the program up to
4736 line @code{99} in the same invocation of factorial, i.e., after the inner
4737 invocations have returned.
4740 94 int factorial (int value)
4742 96 if (value > 1) @{
4743 97 value *= factorial (value - 1);
4750 @kindex advance @var{location}
4751 @itemx advance @var{location}
4752 Continue running the program up to the given @var{location}. An argument is
4753 required, which should be of one of the forms described in
4754 @ref{Specify Location}.
4755 Execution will also stop upon exit from the current stack
4756 frame. This command is similar to @code{until}, but @code{advance} will
4757 not skip over recursive function calls, and the target location doesn't
4758 have to be in the same frame as the current one.
4762 @kindex si @r{(@code{stepi})}
4764 @itemx stepi @var{arg}
4766 Execute one machine instruction, then stop and return to the debugger.
4768 It is often useful to do @samp{display/i $pc} when stepping by machine
4769 instructions. This makes @value{GDBN} automatically display the next
4770 instruction to be executed, each time your program stops. @xref{Auto
4771 Display,, Automatic Display}.
4773 An argument is a repeat count, as in @code{step}.
4777 @kindex ni @r{(@code{nexti})}
4779 @itemx nexti @var{arg}
4781 Execute one machine instruction, but if it is a function call,
4782 proceed until the function returns.
4784 An argument is a repeat count, as in @code{next}.
4791 A signal is an asynchronous event that can happen in a program. The
4792 operating system defines the possible kinds of signals, and gives each
4793 kind a name and a number. For example, in Unix @code{SIGINT} is the
4794 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4795 @code{SIGSEGV} is the signal a program gets from referencing a place in
4796 memory far away from all the areas in use; @code{SIGALRM} occurs when
4797 the alarm clock timer goes off (which happens only if your program has
4798 requested an alarm).
4800 @cindex fatal signals
4801 Some signals, including @code{SIGALRM}, are a normal part of the
4802 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4803 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4804 program has not specified in advance some other way to handle the signal.
4805 @code{SIGINT} does not indicate an error in your program, but it is normally
4806 fatal so it can carry out the purpose of the interrupt: to kill the program.
4808 @value{GDBN} has the ability to detect any occurrence of a signal in your
4809 program. You can tell @value{GDBN} in advance what to do for each kind of
4812 @cindex handling signals
4813 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4814 @code{SIGALRM} be silently passed to your program
4815 (so as not to interfere with their role in the program's functioning)
4816 but to stop your program immediately whenever an error signal happens.
4817 You can change these settings with the @code{handle} command.
4820 @kindex info signals
4824 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4825 handle each one. You can use this to see the signal numbers of all
4826 the defined types of signals.
4828 @item info signals @var{sig}
4829 Similar, but print information only about the specified signal number.
4831 @code{info handle} is an alias for @code{info signals}.
4834 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4835 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4836 can be the number of a signal or its name (with or without the
4837 @samp{SIG} at the beginning); a list of signal numbers of the form
4838 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4839 known signals. Optional arguments @var{keywords}, described below,
4840 say what change to make.
4844 The keywords allowed by the @code{handle} command can be abbreviated.
4845 Their full names are:
4849 @value{GDBN} should not stop your program when this signal happens. It may
4850 still print a message telling you that the signal has come in.
4853 @value{GDBN} should stop your program when this signal happens. This implies
4854 the @code{print} keyword as well.
4857 @value{GDBN} should print a message when this signal happens.
4860 @value{GDBN} should not mention the occurrence of the signal at all. This
4861 implies the @code{nostop} keyword as well.
4865 @value{GDBN} should allow your program to see this signal; your program
4866 can handle the signal, or else it may terminate if the signal is fatal
4867 and not handled. @code{pass} and @code{noignore} are synonyms.
4871 @value{GDBN} should not allow your program to see this signal.
4872 @code{nopass} and @code{ignore} are synonyms.
4876 When a signal stops your program, the signal is not visible to the
4878 continue. Your program sees the signal then, if @code{pass} is in
4879 effect for the signal in question @emph{at that time}. In other words,
4880 after @value{GDBN} reports a signal, you can use the @code{handle}
4881 command with @code{pass} or @code{nopass} to control whether your
4882 program sees that signal when you continue.
4884 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4885 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4886 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4889 You can also use the @code{signal} command to prevent your program from
4890 seeing a signal, or cause it to see a signal it normally would not see,
4891 or to give it any signal at any time. For example, if your program stopped
4892 due to some sort of memory reference error, you might store correct
4893 values into the erroneous variables and continue, hoping to see more
4894 execution; but your program would probably terminate immediately as
4895 a result of the fatal signal once it saw the signal. To prevent this,
4896 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4899 @cindex extra signal information
4900 @anchor{extra signal information}
4902 On some targets, @value{GDBN} can inspect extra signal information
4903 associated with the intercepted signal, before it is actually
4904 delivered to the program being debugged. This information is exported
4905 by the convenience variable @code{$_siginfo}, and consists of data
4906 that is passed by the kernel to the signal handler at the time of the
4907 receipt of a signal. The data type of the information itself is
4908 target dependent. You can see the data type using the @code{ptype
4909 $_siginfo} command. On Unix systems, it typically corresponds to the
4910 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4913 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4914 referenced address that raised a segmentation fault.
4918 (@value{GDBP}) continue
4919 Program received signal SIGSEGV, Segmentation fault.
4920 0x0000000000400766 in main ()
4922 (@value{GDBP}) ptype $_siginfo
4929 struct @{...@} _kill;
4930 struct @{...@} _timer;
4932 struct @{...@} _sigchld;
4933 struct @{...@} _sigfault;
4934 struct @{...@} _sigpoll;
4937 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4941 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4942 $1 = (void *) 0x7ffff7ff7000
4946 Depending on target support, @code{$_siginfo} may also be writable.
4949 @section Stopping and Starting Multi-thread Programs
4951 @cindex stopped threads
4952 @cindex threads, stopped
4954 @cindex continuing threads
4955 @cindex threads, continuing
4957 @value{GDBN} supports debugging programs with multiple threads
4958 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4959 are two modes of controlling execution of your program within the
4960 debugger. In the default mode, referred to as @dfn{all-stop mode},
4961 when any thread in your program stops (for example, at a breakpoint
4962 or while being stepped), all other threads in the program are also stopped by
4963 @value{GDBN}. On some targets, @value{GDBN} also supports
4964 @dfn{non-stop mode}, in which other threads can continue to run freely while
4965 you examine the stopped thread in the debugger.
4968 * All-Stop Mode:: All threads stop when GDB takes control
4969 * Non-Stop Mode:: Other threads continue to execute
4970 * Background Execution:: Running your program asynchronously
4971 * Thread-Specific Breakpoints:: Controlling breakpoints
4972 * Interrupted System Calls:: GDB may interfere with system calls
4973 * Observer Mode:: GDB does not alter program behavior
4977 @subsection All-Stop Mode
4979 @cindex all-stop mode
4981 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4982 @emph{all} threads of execution stop, not just the current thread. This
4983 allows you to examine the overall state of the program, including
4984 switching between threads, without worrying that things may change
4987 Conversely, whenever you restart the program, @emph{all} threads start
4988 executing. @emph{This is true even when single-stepping} with commands
4989 like @code{step} or @code{next}.
4991 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4992 Since thread scheduling is up to your debugging target's operating
4993 system (not controlled by @value{GDBN}), other threads may
4994 execute more than one statement while the current thread completes a
4995 single step. Moreover, in general other threads stop in the middle of a
4996 statement, rather than at a clean statement boundary, when the program
4999 You might even find your program stopped in another thread after
5000 continuing or even single-stepping. This happens whenever some other
5001 thread runs into a breakpoint, a signal, or an exception before the
5002 first thread completes whatever you requested.
5004 @cindex automatic thread selection
5005 @cindex switching threads automatically
5006 @cindex threads, automatic switching
5007 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5008 signal, it automatically selects the thread where that breakpoint or
5009 signal happened. @value{GDBN} alerts you to the context switch with a
5010 message such as @samp{[Switching to Thread @var{n}]} to identify the
5013 On some OSes, you can modify @value{GDBN}'s default behavior by
5014 locking the OS scheduler to allow only a single thread to run.
5017 @item set scheduler-locking @var{mode}
5018 @cindex scheduler locking mode
5019 @cindex lock scheduler
5020 Set the scheduler locking mode. If it is @code{off}, then there is no
5021 locking and any thread may run at any time. If @code{on}, then only the
5022 current thread may run when the inferior is resumed. The @code{step}
5023 mode optimizes for single-stepping; it prevents other threads
5024 from preempting the current thread while you are stepping, so that
5025 the focus of debugging does not change unexpectedly.
5026 Other threads only rarely (or never) get a chance to run
5027 when you step. They are more likely to run when you @samp{next} over a
5028 function call, and they are completely free to run when you use commands
5029 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5030 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5031 the current thread away from the thread that you are debugging.
5033 @item show scheduler-locking
5034 Display the current scheduler locking mode.
5037 @cindex resume threads of multiple processes simultaneously
5038 By default, when you issue one of the execution commands such as
5039 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5040 threads of the current inferior to run. For example, if @value{GDBN}
5041 is attached to two inferiors, each with two threads, the
5042 @code{continue} command resumes only the two threads of the current
5043 inferior. This is useful, for example, when you debug a program that
5044 forks and you want to hold the parent stopped (so that, for instance,
5045 it doesn't run to exit), while you debug the child. In other
5046 situations, you may not be interested in inspecting the current state
5047 of any of the processes @value{GDBN} is attached to, and you may want
5048 to resume them all until some breakpoint is hit. In the latter case,
5049 you can instruct @value{GDBN} to allow all threads of all the
5050 inferiors to run with the @w{@code{set schedule-multiple}} command.
5053 @kindex set schedule-multiple
5054 @item set schedule-multiple
5055 Set the mode for allowing threads of multiple processes to be resumed
5056 when an execution command is issued. When @code{on}, all threads of
5057 all processes are allowed to run. When @code{off}, only the threads
5058 of the current process are resumed. The default is @code{off}. The
5059 @code{scheduler-locking} mode takes precedence when set to @code{on},
5060 or while you are stepping and set to @code{step}.
5062 @item show schedule-multiple
5063 Display the current mode for resuming the execution of threads of
5068 @subsection Non-Stop Mode
5070 @cindex non-stop mode
5072 @c This section is really only a place-holder, and needs to be expanded
5073 @c with more details.
5075 For some multi-threaded targets, @value{GDBN} supports an optional
5076 mode of operation in which you can examine stopped program threads in
5077 the debugger while other threads continue to execute freely. This
5078 minimizes intrusion when debugging live systems, such as programs
5079 where some threads have real-time constraints or must continue to
5080 respond to external events. This is referred to as @dfn{non-stop} mode.
5082 In non-stop mode, when a thread stops to report a debugging event,
5083 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5084 threads as well, in contrast to the all-stop mode behavior. Additionally,
5085 execution commands such as @code{continue} and @code{step} apply by default
5086 only to the current thread in non-stop mode, rather than all threads as
5087 in all-stop mode. This allows you to control threads explicitly in
5088 ways that are not possible in all-stop mode --- for example, stepping
5089 one thread while allowing others to run freely, stepping
5090 one thread while holding all others stopped, or stepping several threads
5091 independently and simultaneously.
5093 To enter non-stop mode, use this sequence of commands before you run
5094 or attach to your program:
5097 # Enable the async interface.
5100 # If using the CLI, pagination breaks non-stop.
5103 # Finally, turn it on!
5107 You can use these commands to manipulate the non-stop mode setting:
5110 @kindex set non-stop
5111 @item set non-stop on
5112 Enable selection of non-stop mode.
5113 @item set non-stop off
5114 Disable selection of non-stop mode.
5115 @kindex show non-stop
5117 Show the current non-stop enablement setting.
5120 Note these commands only reflect whether non-stop mode is enabled,
5121 not whether the currently-executing program is being run in non-stop mode.
5122 In particular, the @code{set non-stop} preference is only consulted when
5123 @value{GDBN} starts or connects to the target program, and it is generally
5124 not possible to switch modes once debugging has started. Furthermore,
5125 since not all targets support non-stop mode, even when you have enabled
5126 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5129 In non-stop mode, all execution commands apply only to the current thread
5130 by default. That is, @code{continue} only continues one thread.
5131 To continue all threads, issue @code{continue -a} or @code{c -a}.
5133 You can use @value{GDBN}'s background execution commands
5134 (@pxref{Background Execution}) to run some threads in the background
5135 while you continue to examine or step others from @value{GDBN}.
5136 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5137 always executed asynchronously in non-stop mode.
5139 Suspending execution is done with the @code{interrupt} command when
5140 running in the background, or @kbd{Ctrl-c} during foreground execution.
5141 In all-stop mode, this stops the whole process;
5142 but in non-stop mode the interrupt applies only to the current thread.
5143 To stop the whole program, use @code{interrupt -a}.
5145 Other execution commands do not currently support the @code{-a} option.
5147 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5148 that thread current, as it does in all-stop mode. This is because the
5149 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5150 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5151 changed to a different thread just as you entered a command to operate on the
5152 previously current thread.
5154 @node Background Execution
5155 @subsection Background Execution
5157 @cindex foreground execution
5158 @cindex background execution
5159 @cindex asynchronous execution
5160 @cindex execution, foreground, background and asynchronous
5162 @value{GDBN}'s execution commands have two variants: the normal
5163 foreground (synchronous) behavior, and a background
5164 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5165 the program to report that some thread has stopped before prompting for
5166 another command. In background execution, @value{GDBN} immediately gives
5167 a command prompt so that you can issue other commands while your program runs.
5169 You need to explicitly enable asynchronous mode before you can use
5170 background execution commands. You can use these commands to
5171 manipulate the asynchronous mode setting:
5174 @kindex set target-async
5175 @item set target-async on
5176 Enable asynchronous mode.
5177 @item set target-async off
5178 Disable asynchronous mode.
5179 @kindex show target-async
5180 @item show target-async
5181 Show the current target-async setting.
5184 If the target doesn't support async mode, @value{GDBN} issues an error
5185 message if you attempt to use the background execution commands.
5187 To specify background execution, add a @code{&} to the command. For example,
5188 the background form of the @code{continue} command is @code{continue&}, or
5189 just @code{c&}. The execution commands that accept background execution
5195 @xref{Starting, , Starting your Program}.
5199 @xref{Attach, , Debugging an Already-running Process}.
5203 @xref{Continuing and Stepping, step}.
5207 @xref{Continuing and Stepping, stepi}.
5211 @xref{Continuing and Stepping, next}.
5215 @xref{Continuing and Stepping, nexti}.
5219 @xref{Continuing and Stepping, continue}.
5223 @xref{Continuing and Stepping, finish}.
5227 @xref{Continuing and Stepping, until}.
5231 Background execution is especially useful in conjunction with non-stop
5232 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5233 However, you can also use these commands in the normal all-stop mode with
5234 the restriction that you cannot issue another execution command until the
5235 previous one finishes. Examples of commands that are valid in all-stop
5236 mode while the program is running include @code{help} and @code{info break}.
5238 You can interrupt your program while it is running in the background by
5239 using the @code{interrupt} command.
5246 Suspend execution of the running program. In all-stop mode,
5247 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5248 only the current thread. To stop the whole program in non-stop mode,
5249 use @code{interrupt -a}.
5252 @node Thread-Specific Breakpoints
5253 @subsection Thread-Specific Breakpoints
5255 When your program has multiple threads (@pxref{Threads,, Debugging
5256 Programs with Multiple Threads}), you can choose whether to set
5257 breakpoints on all threads, or on a particular thread.
5260 @cindex breakpoints and threads
5261 @cindex thread breakpoints
5262 @kindex break @dots{} thread @var{threadno}
5263 @item break @var{linespec} thread @var{threadno}
5264 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5265 @var{linespec} specifies source lines; there are several ways of
5266 writing them (@pxref{Specify Location}), but the effect is always to
5267 specify some source line.
5269 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5270 to specify that you only want @value{GDBN} to stop the program when a
5271 particular thread reaches this breakpoint. @var{threadno} is one of the
5272 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5273 column of the @samp{info threads} display.
5275 If you do not specify @samp{thread @var{threadno}} when you set a
5276 breakpoint, the breakpoint applies to @emph{all} threads of your
5279 You can use the @code{thread} qualifier on conditional breakpoints as
5280 well; in this case, place @samp{thread @var{threadno}} before or
5281 after the breakpoint condition, like this:
5284 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5289 @node Interrupted System Calls
5290 @subsection Interrupted System Calls
5292 @cindex thread breakpoints and system calls
5293 @cindex system calls and thread breakpoints
5294 @cindex premature return from system calls
5295 There is an unfortunate side effect when using @value{GDBN} to debug
5296 multi-threaded programs. If one thread stops for a
5297 breakpoint, or for some other reason, and another thread is blocked in a
5298 system call, then the system call may return prematurely. This is a
5299 consequence of the interaction between multiple threads and the signals
5300 that @value{GDBN} uses to implement breakpoints and other events that
5303 To handle this problem, your program should check the return value of
5304 each system call and react appropriately. This is good programming
5307 For example, do not write code like this:
5313 The call to @code{sleep} will return early if a different thread stops
5314 at a breakpoint or for some other reason.
5316 Instead, write this:
5321 unslept = sleep (unslept);
5324 A system call is allowed to return early, so the system is still
5325 conforming to its specification. But @value{GDBN} does cause your
5326 multi-threaded program to behave differently than it would without
5329 Also, @value{GDBN} uses internal breakpoints in the thread library to
5330 monitor certain events such as thread creation and thread destruction.
5331 When such an event happens, a system call in another thread may return
5332 prematurely, even though your program does not appear to stop.
5335 @subsection Observer Mode
5337 If you want to build on non-stop mode and observe program behavior
5338 without any chance of disruption by @value{GDBN}, you can set
5339 variables to disable all of the debugger's attempts to modify state,
5340 whether by writing memory, inserting breakpoints, etc. These operate
5341 at a low level, intercepting operations from all commands.
5343 When all of these are set to @code{off}, then @value{GDBN} is said to
5344 be @dfn{observer mode}. As a convenience, the variable
5345 @code{observer} can be set to disable these, plus enable non-stop
5348 Note that @value{GDBN} will not prevent you from making nonsensical
5349 combinations of these settings. For instance, if you have enabled
5350 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5351 then breakpoints that work by writing trap instructions into the code
5352 stream will still not be able to be placed.
5357 @item set observer on
5358 @itemx set observer off
5359 When set to @code{on}, this disables all the permission variables
5360 below (except for @code{insert-fast-tracepoints}), plus enables
5361 non-stop debugging. Setting this to @code{off} switches back to
5362 normal debugging, though remaining in non-stop mode.
5365 Show whether observer mode is on or off.
5367 @kindex may-write-registers
5368 @item set may-write-registers on
5369 @itemx set may-write-registers off
5370 This controls whether @value{GDBN} will attempt to alter the values of
5371 registers, such as with assignment expressions in @code{print}, or the
5372 @code{jump} command. It defaults to @code{on}.
5374 @item show may-write-registers
5375 Show the current permission to write registers.
5377 @kindex may-write-memory
5378 @item set may-write-memory on
5379 @itemx set may-write-memory off
5380 This controls whether @value{GDBN} will attempt to alter the contents
5381 of memory, such as with assignment expressions in @code{print}. It
5382 defaults to @code{on}.
5384 @item show may-write-memory
5385 Show the current permission to write memory.
5387 @kindex may-insert-breakpoints
5388 @item set may-insert-breakpoints on
5389 @itemx set may-insert-breakpoints off
5390 This controls whether @value{GDBN} will attempt to insert breakpoints.
5391 This affects all breakpoints, including internal breakpoints defined
5392 by @value{GDBN}. It defaults to @code{on}.
5394 @item show may-insert-breakpoints
5395 Show the current permission to insert breakpoints.
5397 @kindex may-insert-tracepoints
5398 @item set may-insert-tracepoints on
5399 @itemx set may-insert-tracepoints off
5400 This controls whether @value{GDBN} will attempt to insert (regular)
5401 tracepoints at the beginning of a tracing experiment. It affects only
5402 non-fast tracepoints, fast tracepoints being under the control of
5403 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5405 @item show may-insert-tracepoints
5406 Show the current permission to insert tracepoints.
5408 @kindex may-insert-fast-tracepoints
5409 @item set may-insert-fast-tracepoints on
5410 @itemx set may-insert-fast-tracepoints off
5411 This controls whether @value{GDBN} will attempt to insert fast
5412 tracepoints at the beginning of a tracing experiment. It affects only
5413 fast tracepoints, regular (non-fast) tracepoints being under the
5414 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5416 @item show may-insert-fast-tracepoints
5417 Show the current permission to insert fast tracepoints.
5419 @kindex may-interrupt
5420 @item set may-interrupt on
5421 @itemx set may-interrupt off
5422 This controls whether @value{GDBN} will attempt to interrupt or stop
5423 program execution. When this variable is @code{off}, the
5424 @code{interrupt} command will have no effect, nor will
5425 @kbd{Ctrl-c}. It defaults to @code{on}.
5427 @item show may-interrupt
5428 Show the current permission to interrupt or stop the program.
5432 @node Reverse Execution
5433 @chapter Running programs backward
5434 @cindex reverse execution
5435 @cindex running programs backward
5437 When you are debugging a program, it is not unusual to realize that
5438 you have gone too far, and some event of interest has already happened.
5439 If the target environment supports it, @value{GDBN} can allow you to
5440 ``rewind'' the program by running it backward.
5442 A target environment that supports reverse execution should be able
5443 to ``undo'' the changes in machine state that have taken place as the
5444 program was executing normally. Variables, registers etc.@: should
5445 revert to their previous values. Obviously this requires a great
5446 deal of sophistication on the part of the target environment; not
5447 all target environments can support reverse execution.
5449 When a program is executed in reverse, the instructions that
5450 have most recently been executed are ``un-executed'', in reverse
5451 order. The program counter runs backward, following the previous
5452 thread of execution in reverse. As each instruction is ``un-executed'',
5453 the values of memory and/or registers that were changed by that
5454 instruction are reverted to their previous states. After executing
5455 a piece of source code in reverse, all side effects of that code
5456 should be ``undone'', and all variables should be returned to their
5457 prior values@footnote{
5458 Note that some side effects are easier to undo than others. For instance,
5459 memory and registers are relatively easy, but device I/O is hard. Some
5460 targets may be able undo things like device I/O, and some may not.
5462 The contract between @value{GDBN} and the reverse executing target
5463 requires only that the target do something reasonable when
5464 @value{GDBN} tells it to execute backwards, and then report the
5465 results back to @value{GDBN}. Whatever the target reports back to
5466 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5467 assumes that the memory and registers that the target reports are in a
5468 consistant state, but @value{GDBN} accepts whatever it is given.
5471 If you are debugging in a target environment that supports
5472 reverse execution, @value{GDBN} provides the following commands.
5475 @kindex reverse-continue
5476 @kindex rc @r{(@code{reverse-continue})}
5477 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5478 @itemx rc @r{[}@var{ignore-count}@r{]}
5479 Beginning at the point where your program last stopped, start executing
5480 in reverse. Reverse execution will stop for breakpoints and synchronous
5481 exceptions (signals), just like normal execution. Behavior of
5482 asynchronous signals depends on the target environment.
5484 @kindex reverse-step
5485 @kindex rs @r{(@code{step})}
5486 @item reverse-step @r{[}@var{count}@r{]}
5487 Run the program backward until control reaches the start of a
5488 different source line; then stop it, and return control to @value{GDBN}.
5490 Like the @code{step} command, @code{reverse-step} will only stop
5491 at the beginning of a source line. It ``un-executes'' the previously
5492 executed source line. If the previous source line included calls to
5493 debuggable functions, @code{reverse-step} will step (backward) into
5494 the called function, stopping at the beginning of the @emph{last}
5495 statement in the called function (typically a return statement).
5497 Also, as with the @code{step} command, if non-debuggable functions are
5498 called, @code{reverse-step} will run thru them backward without stopping.
5500 @kindex reverse-stepi
5501 @kindex rsi @r{(@code{reverse-stepi})}
5502 @item reverse-stepi @r{[}@var{count}@r{]}
5503 Reverse-execute one machine instruction. Note that the instruction
5504 to be reverse-executed is @emph{not} the one pointed to by the program
5505 counter, but the instruction executed prior to that one. For instance,
5506 if the last instruction was a jump, @code{reverse-stepi} will take you
5507 back from the destination of the jump to the jump instruction itself.
5509 @kindex reverse-next
5510 @kindex rn @r{(@code{reverse-next})}
5511 @item reverse-next @r{[}@var{count}@r{]}
5512 Run backward to the beginning of the previous line executed in
5513 the current (innermost) stack frame. If the line contains function
5514 calls, they will be ``un-executed'' without stopping. Starting from
5515 the first line of a function, @code{reverse-next} will take you back
5516 to the caller of that function, @emph{before} the function was called,
5517 just as the normal @code{next} command would take you from the last
5518 line of a function back to its return to its caller
5519 @footnote{Unless the code is too heavily optimized.}.
5521 @kindex reverse-nexti
5522 @kindex rni @r{(@code{reverse-nexti})}
5523 @item reverse-nexti @r{[}@var{count}@r{]}
5524 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5525 in reverse, except that called functions are ``un-executed'' atomically.
5526 That is, if the previously executed instruction was a return from
5527 another function, @code{reverse-nexti} will continue to execute
5528 in reverse until the call to that function (from the current stack
5531 @kindex reverse-finish
5532 @item reverse-finish
5533 Just as the @code{finish} command takes you to the point where the
5534 current function returns, @code{reverse-finish} takes you to the point
5535 where it was called. Instead of ending up at the end of the current
5536 function invocation, you end up at the beginning.
5538 @kindex set exec-direction
5539 @item set exec-direction
5540 Set the direction of target execution.
5541 @itemx set exec-direction reverse
5542 @cindex execute forward or backward in time
5543 @value{GDBN} will perform all execution commands in reverse, until the
5544 exec-direction mode is changed to ``forward''. Affected commands include
5545 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5546 command cannot be used in reverse mode.
5547 @item set exec-direction forward
5548 @value{GDBN} will perform all execution commands in the normal fashion.
5549 This is the default.
5553 @node Process Record and Replay
5554 @chapter Recording Inferior's Execution and Replaying It
5555 @cindex process record and replay
5556 @cindex recording inferior's execution and replaying it
5558 On some platforms, @value{GDBN} provides a special @dfn{process record
5559 and replay} target that can record a log of the process execution, and
5560 replay it later with both forward and reverse execution commands.
5563 When this target is in use, if the execution log includes the record
5564 for the next instruction, @value{GDBN} will debug in @dfn{replay
5565 mode}. In the replay mode, the inferior does not really execute code
5566 instructions. Instead, all the events that normally happen during
5567 code execution are taken from the execution log. While code is not
5568 really executed in replay mode, the values of registers (including the
5569 program counter register) and the memory of the inferior are still
5570 changed as they normally would. Their contents are taken from the
5574 If the record for the next instruction is not in the execution log,
5575 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5576 inferior executes normally, and @value{GDBN} records the execution log
5579 The process record and replay target supports reverse execution
5580 (@pxref{Reverse Execution}), even if the platform on which the
5581 inferior runs does not. However, the reverse execution is limited in
5582 this case by the range of the instructions recorded in the execution
5583 log. In other words, reverse execution on platforms that don't
5584 support it directly can only be done in the replay mode.
5586 When debugging in the reverse direction, @value{GDBN} will work in
5587 replay mode as long as the execution log includes the record for the
5588 previous instruction; otherwise, it will work in record mode, if the
5589 platform supports reverse execution, or stop if not.
5591 For architecture environments that support process record and replay,
5592 @value{GDBN} provides the following commands:
5595 @kindex target record
5599 This command starts the process record and replay target. The process
5600 record and replay target can only debug a process that is already
5601 running. Therefore, you need first to start the process with the
5602 @kbd{run} or @kbd{start} commands, and then start the recording with
5603 the @kbd{target record} command.
5605 Both @code{record} and @code{rec} are aliases of @code{target record}.
5607 @cindex displaced stepping, and process record and replay
5608 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5609 will be automatically disabled when process record and replay target
5610 is started. That's because the process record and replay target
5611 doesn't support displaced stepping.
5613 @cindex non-stop mode, and process record and replay
5614 @cindex asynchronous execution, and process record and replay
5615 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5616 the asynchronous execution mode (@pxref{Background Execution}), the
5617 process record and replay target cannot be started because it doesn't
5618 support these two modes.
5623 Stop the process record and replay target. When process record and
5624 replay target stops, the entire execution log will be deleted and the
5625 inferior will either be terminated, or will remain in its final state.
5627 When you stop the process record and replay target in record mode (at
5628 the end of the execution log), the inferior will be stopped at the
5629 next instruction that would have been recorded. In other words, if
5630 you record for a while and then stop recording, the inferior process
5631 will be left in the same state as if the recording never happened.
5633 On the other hand, if the process record and replay target is stopped
5634 while in replay mode (that is, not at the end of the execution log,
5635 but at some earlier point), the inferior process will become ``live''
5636 at that earlier state, and it will then be possible to continue the
5637 usual ``live'' debugging of the process from that state.
5639 When the inferior process exits, or @value{GDBN} detaches from it,
5640 process record and replay target will automatically stop itself.
5643 @item record save @var{filename}
5644 Save the execution log to a file @file{@var{filename}}.
5645 Default filename is @file{gdb_record.@var{process_id}}, where
5646 @var{process_id} is the process ID of the inferior.
5648 @kindex record restore
5649 @item record restore @var{filename}
5650 Restore the execution log from a file @file{@var{filename}}.
5651 File must have been created with @code{record save}.
5653 @kindex set record insn-number-max
5654 @item set record insn-number-max @var{limit}
5655 Set the limit of instructions to be recorded. Default value is 200000.
5657 If @var{limit} is a positive number, then @value{GDBN} will start
5658 deleting instructions from the log once the number of the record
5659 instructions becomes greater than @var{limit}. For every new recorded
5660 instruction, @value{GDBN} will delete the earliest recorded
5661 instruction to keep the number of recorded instructions at the limit.
5662 (Since deleting recorded instructions loses information, @value{GDBN}
5663 lets you control what happens when the limit is reached, by means of
5664 the @code{stop-at-limit} option, described below.)
5666 If @var{limit} is zero, @value{GDBN} will never delete recorded
5667 instructions from the execution log. The number of recorded
5668 instructions is unlimited in this case.
5670 @kindex show record insn-number-max
5671 @item show record insn-number-max
5672 Show the limit of instructions to be recorded.
5674 @kindex set record stop-at-limit
5675 @item set record stop-at-limit
5676 Control the behavior when the number of recorded instructions reaches
5677 the limit. If ON (the default), @value{GDBN} will stop when the limit
5678 is reached for the first time and ask you whether you want to stop the
5679 inferior or continue running it and recording the execution log. If
5680 you decide to continue recording, each new recorded instruction will
5681 cause the oldest one to be deleted.
5683 If this option is OFF, @value{GDBN} will automatically delete the
5684 oldest record to make room for each new one, without asking.
5686 @kindex show record stop-at-limit
5687 @item show record stop-at-limit
5688 Show the current setting of @code{stop-at-limit}.
5692 Show various statistics about the state of process record and its
5693 in-memory execution log buffer, including:
5697 Whether in record mode or replay mode.
5699 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5701 Highest recorded instruction number.
5703 Current instruction about to be replayed (if in replay mode).
5705 Number of instructions contained in the execution log.
5707 Maximum number of instructions that may be contained in the execution log.
5710 @kindex record delete
5713 When record target runs in replay mode (``in the past''), delete the
5714 subsequent execution log and begin to record a new execution log starting
5715 from the current address. This means you will abandon the previously
5716 recorded ``future'' and begin recording a new ``future''.
5721 @chapter Examining the Stack
5723 When your program has stopped, the first thing you need to know is where it
5724 stopped and how it got there.
5727 Each time your program performs a function call, information about the call
5729 That information includes the location of the call in your program,
5730 the arguments of the call,
5731 and the local variables of the function being called.
5732 The information is saved in a block of data called a @dfn{stack frame}.
5733 The stack frames are allocated in a region of memory called the @dfn{call
5736 When your program stops, the @value{GDBN} commands for examining the
5737 stack allow you to see all of this information.
5739 @cindex selected frame
5740 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5741 @value{GDBN} commands refer implicitly to the selected frame. In
5742 particular, whenever you ask @value{GDBN} for the value of a variable in
5743 your program, the value is found in the selected frame. There are
5744 special @value{GDBN} commands to select whichever frame you are
5745 interested in. @xref{Selection, ,Selecting a Frame}.
5747 When your program stops, @value{GDBN} automatically selects the
5748 currently executing frame and describes it briefly, similar to the
5749 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5752 * Frames:: Stack frames
5753 * Backtrace:: Backtraces
5754 * Selection:: Selecting a frame
5755 * Frame Info:: Information on a frame
5760 @section Stack Frames
5762 @cindex frame, definition
5764 The call stack is divided up into contiguous pieces called @dfn{stack
5765 frames}, or @dfn{frames} for short; each frame is the data associated
5766 with one call to one function. The frame contains the arguments given
5767 to the function, the function's local variables, and the address at
5768 which the function is executing.
5770 @cindex initial frame
5771 @cindex outermost frame
5772 @cindex innermost frame
5773 When your program is started, the stack has only one frame, that of the
5774 function @code{main}. This is called the @dfn{initial} frame or the
5775 @dfn{outermost} frame. Each time a function is called, a new frame is
5776 made. Each time a function returns, the frame for that function invocation
5777 is eliminated. If a function is recursive, there can be many frames for
5778 the same function. The frame for the function in which execution is
5779 actually occurring is called the @dfn{innermost} frame. This is the most
5780 recently created of all the stack frames that still exist.
5782 @cindex frame pointer
5783 Inside your program, stack frames are identified by their addresses. A
5784 stack frame consists of many bytes, each of which has its own address; each
5785 kind of computer has a convention for choosing one byte whose
5786 address serves as the address of the frame. Usually this address is kept
5787 in a register called the @dfn{frame pointer register}
5788 (@pxref{Registers, $fp}) while execution is going on in that frame.
5790 @cindex frame number
5791 @value{GDBN} assigns numbers to all existing stack frames, starting with
5792 zero for the innermost frame, one for the frame that called it,
5793 and so on upward. These numbers do not really exist in your program;
5794 they are assigned by @value{GDBN} to give you a way of designating stack
5795 frames in @value{GDBN} commands.
5797 @c The -fomit-frame-pointer below perennially causes hbox overflow
5798 @c underflow problems.
5799 @cindex frameless execution
5800 Some compilers provide a way to compile functions so that they operate
5801 without stack frames. (For example, the @value{NGCC} option
5803 @samp{-fomit-frame-pointer}
5805 generates functions without a frame.)
5806 This is occasionally done with heavily used library functions to save
5807 the frame setup time. @value{GDBN} has limited facilities for dealing
5808 with these function invocations. If the innermost function invocation
5809 has no stack frame, @value{GDBN} nevertheless regards it as though
5810 it had a separate frame, which is numbered zero as usual, allowing
5811 correct tracing of the function call chain. However, @value{GDBN} has
5812 no provision for frameless functions elsewhere in the stack.
5815 @kindex frame@r{, command}
5816 @cindex current stack frame
5817 @item frame @var{args}
5818 The @code{frame} command allows you to move from one stack frame to another,
5819 and to print the stack frame you select. @var{args} may be either the
5820 address of the frame or the stack frame number. Without an argument,
5821 @code{frame} prints the current stack frame.
5823 @kindex select-frame
5824 @cindex selecting frame silently
5826 The @code{select-frame} command allows you to move from one stack frame
5827 to another without printing the frame. This is the silent version of
5835 @cindex call stack traces
5836 A backtrace is a summary of how your program got where it is. It shows one
5837 line per frame, for many frames, starting with the currently executing
5838 frame (frame zero), followed by its caller (frame one), and on up the
5843 @kindex bt @r{(@code{backtrace})}
5846 Print a backtrace of the entire stack: one line per frame for all
5847 frames in the stack.
5849 You can stop the backtrace at any time by typing the system interrupt
5850 character, normally @kbd{Ctrl-c}.
5852 @item backtrace @var{n}
5854 Similar, but print only the innermost @var{n} frames.
5856 @item backtrace -@var{n}
5858 Similar, but print only the outermost @var{n} frames.
5860 @item backtrace full
5862 @itemx bt full @var{n}
5863 @itemx bt full -@var{n}
5864 Print the values of the local variables also. @var{n} specifies the
5865 number of frames to print, as described above.
5870 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5871 are additional aliases for @code{backtrace}.
5873 @cindex multiple threads, backtrace
5874 In a multi-threaded program, @value{GDBN} by default shows the
5875 backtrace only for the current thread. To display the backtrace for
5876 several or all of the threads, use the command @code{thread apply}
5877 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5878 apply all backtrace}, @value{GDBN} will display the backtrace for all
5879 the threads; this is handy when you debug a core dump of a
5880 multi-threaded program.
5882 Each line in the backtrace shows the frame number and the function name.
5883 The program counter value is also shown---unless you use @code{set
5884 print address off}. The backtrace also shows the source file name and
5885 line number, as well as the arguments to the function. The program
5886 counter value is omitted if it is at the beginning of the code for that
5889 Here is an example of a backtrace. It was made with the command
5890 @samp{bt 3}, so it shows the innermost three frames.
5894 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5896 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5897 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5899 (More stack frames follow...)
5904 The display for frame zero does not begin with a program counter
5905 value, indicating that your program has stopped at the beginning of the
5906 code for line @code{993} of @code{builtin.c}.
5909 The value of parameter @code{data} in frame 1 has been replaced by
5910 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5911 only if it is a scalar (integer, pointer, enumeration, etc). See command
5912 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5913 on how to configure the way function parameter values are printed.
5915 @cindex value optimized out, in backtrace
5916 @cindex function call arguments, optimized out
5917 If your program was compiled with optimizations, some compilers will
5918 optimize away arguments passed to functions if those arguments are
5919 never used after the call. Such optimizations generate code that
5920 passes arguments through registers, but doesn't store those arguments
5921 in the stack frame. @value{GDBN} has no way of displaying such
5922 arguments in stack frames other than the innermost one. Here's what
5923 such a backtrace might look like:
5927 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5929 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5930 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5932 (More stack frames follow...)
5937 The values of arguments that were not saved in their stack frames are
5938 shown as @samp{<value optimized out>}.
5940 If you need to display the values of such optimized-out arguments,
5941 either deduce that from other variables whose values depend on the one
5942 you are interested in, or recompile without optimizations.
5944 @cindex backtrace beyond @code{main} function
5945 @cindex program entry point
5946 @cindex startup code, and backtrace
5947 Most programs have a standard user entry point---a place where system
5948 libraries and startup code transition into user code. For C this is
5949 @code{main}@footnote{
5950 Note that embedded programs (the so-called ``free-standing''
5951 environment) are not required to have a @code{main} function as the
5952 entry point. They could even have multiple entry points.}.
5953 When @value{GDBN} finds the entry function in a backtrace
5954 it will terminate the backtrace, to avoid tracing into highly
5955 system-specific (and generally uninteresting) code.
5957 If you need to examine the startup code, or limit the number of levels
5958 in a backtrace, you can change this behavior:
5961 @item set backtrace past-main
5962 @itemx set backtrace past-main on
5963 @kindex set backtrace
5964 Backtraces will continue past the user entry point.
5966 @item set backtrace past-main off
5967 Backtraces will stop when they encounter the user entry point. This is the
5970 @item show backtrace past-main
5971 @kindex show backtrace
5972 Display the current user entry point backtrace policy.
5974 @item set backtrace past-entry
5975 @itemx set backtrace past-entry on
5976 Backtraces will continue past the internal entry point of an application.
5977 This entry point is encoded by the linker when the application is built,
5978 and is likely before the user entry point @code{main} (or equivalent) is called.
5980 @item set backtrace past-entry off
5981 Backtraces will stop when they encounter the internal entry point of an
5982 application. This is the default.
5984 @item show backtrace past-entry
5985 Display the current internal entry point backtrace policy.
5987 @item set backtrace limit @var{n}
5988 @itemx set backtrace limit 0
5989 @cindex backtrace limit
5990 Limit the backtrace to @var{n} levels. A value of zero means
5993 @item show backtrace limit
5994 Display the current limit on backtrace levels.
5998 @section Selecting a Frame
6000 Most commands for examining the stack and other data in your program work on
6001 whichever stack frame is selected at the moment. Here are the commands for
6002 selecting a stack frame; all of them finish by printing a brief description
6003 of the stack frame just selected.
6006 @kindex frame@r{, selecting}
6007 @kindex f @r{(@code{frame})}
6010 Select frame number @var{n}. Recall that frame zero is the innermost
6011 (currently executing) frame, frame one is the frame that called the
6012 innermost one, and so on. The highest-numbered frame is the one for
6015 @item frame @var{addr}
6017 Select the frame at address @var{addr}. This is useful mainly if the
6018 chaining of stack frames has been damaged by a bug, making it
6019 impossible for @value{GDBN} to assign numbers properly to all frames. In
6020 addition, this can be useful when your program has multiple stacks and
6021 switches between them.
6023 On the SPARC architecture, @code{frame} needs two addresses to
6024 select an arbitrary frame: a frame pointer and a stack pointer.
6026 On the MIPS and Alpha architecture, it needs two addresses: a stack
6027 pointer and a program counter.
6029 On the 29k architecture, it needs three addresses: a register stack
6030 pointer, a program counter, and a memory stack pointer.
6034 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6035 advances toward the outermost frame, to higher frame numbers, to frames
6036 that have existed longer. @var{n} defaults to one.
6039 @kindex do @r{(@code{down})}
6041 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6042 advances toward the innermost frame, to lower frame numbers, to frames
6043 that were created more recently. @var{n} defaults to one. You may
6044 abbreviate @code{down} as @code{do}.
6047 All of these commands end by printing two lines of output describing the
6048 frame. The first line shows the frame number, the function name, the
6049 arguments, and the source file and line number of execution in that
6050 frame. The second line shows the text of that source line.
6058 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6060 10 read_input_file (argv[i]);
6064 After such a printout, the @code{list} command with no arguments
6065 prints ten lines centered on the point of execution in the frame.
6066 You can also edit the program at the point of execution with your favorite
6067 editing program by typing @code{edit}.
6068 @xref{List, ,Printing Source Lines},
6072 @kindex down-silently
6074 @item up-silently @var{n}
6075 @itemx down-silently @var{n}
6076 These two commands are variants of @code{up} and @code{down},
6077 respectively; they differ in that they do their work silently, without
6078 causing display of the new frame. They are intended primarily for use
6079 in @value{GDBN} command scripts, where the output might be unnecessary and
6084 @section Information About a Frame
6086 There are several other commands to print information about the selected
6092 When used without any argument, this command does not change which
6093 frame is selected, but prints a brief description of the currently
6094 selected stack frame. It can be abbreviated @code{f}. With an
6095 argument, this command is used to select a stack frame.
6096 @xref{Selection, ,Selecting a Frame}.
6099 @kindex info f @r{(@code{info frame})}
6102 This command prints a verbose description of the selected stack frame,
6107 the address of the frame
6109 the address of the next frame down (called by this frame)
6111 the address of the next frame up (caller of this frame)
6113 the language in which the source code corresponding to this frame is written
6115 the address of the frame's arguments
6117 the address of the frame's local variables
6119 the program counter saved in it (the address of execution in the caller frame)
6121 which registers were saved in the frame
6124 @noindent The verbose description is useful when
6125 something has gone wrong that has made the stack format fail to fit
6126 the usual conventions.
6128 @item info frame @var{addr}
6129 @itemx info f @var{addr}
6130 Print a verbose description of the frame at address @var{addr}, without
6131 selecting that frame. The selected frame remains unchanged by this
6132 command. This requires the same kind of address (more than one for some
6133 architectures) that you specify in the @code{frame} command.
6134 @xref{Selection, ,Selecting a Frame}.
6138 Print the arguments of the selected frame, each on a separate line.
6142 Print the local variables of the selected frame, each on a separate
6143 line. These are all variables (declared either static or automatic)
6144 accessible at the point of execution of the selected frame.
6147 @cindex catch exceptions, list active handlers
6148 @cindex exception handlers, how to list
6150 Print a list of all the exception handlers that are active in the
6151 current stack frame at the current point of execution. To see other
6152 exception handlers, visit the associated frame (using the @code{up},
6153 @code{down}, or @code{frame} commands); then type @code{info catch}.
6154 @xref{Set Catchpoints, , Setting Catchpoints}.
6160 @chapter Examining Source Files
6162 @value{GDBN} can print parts of your program's source, since the debugging
6163 information recorded in the program tells @value{GDBN} what source files were
6164 used to build it. When your program stops, @value{GDBN} spontaneously prints
6165 the line where it stopped. Likewise, when you select a stack frame
6166 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6167 execution in that frame has stopped. You can print other portions of
6168 source files by explicit command.
6170 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6171 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6172 @value{GDBN} under @sc{gnu} Emacs}.
6175 * List:: Printing source lines
6176 * Specify Location:: How to specify code locations
6177 * Edit:: Editing source files
6178 * Search:: Searching source files
6179 * Source Path:: Specifying source directories
6180 * Machine Code:: Source and machine code
6184 @section Printing Source Lines
6187 @kindex l @r{(@code{list})}
6188 To print lines from a source file, use the @code{list} command
6189 (abbreviated @code{l}). By default, ten lines are printed.
6190 There are several ways to specify what part of the file you want to
6191 print; see @ref{Specify Location}, for the full list.
6193 Here are the forms of the @code{list} command most commonly used:
6196 @item list @var{linenum}
6197 Print lines centered around line number @var{linenum} in the
6198 current source file.
6200 @item list @var{function}
6201 Print lines centered around the beginning of function
6205 Print more lines. If the last lines printed were printed with a
6206 @code{list} command, this prints lines following the last lines
6207 printed; however, if the last line printed was a solitary line printed
6208 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6209 Stack}), this prints lines centered around that line.
6212 Print lines just before the lines last printed.
6215 @cindex @code{list}, how many lines to display
6216 By default, @value{GDBN} prints ten source lines with any of these forms of
6217 the @code{list} command. You can change this using @code{set listsize}:
6220 @kindex set listsize
6221 @item set listsize @var{count}
6222 Make the @code{list} command display @var{count} source lines (unless
6223 the @code{list} argument explicitly specifies some other number).
6225 @kindex show listsize
6227 Display the number of lines that @code{list} prints.
6230 Repeating a @code{list} command with @key{RET} discards the argument,
6231 so it is equivalent to typing just @code{list}. This is more useful
6232 than listing the same lines again. An exception is made for an
6233 argument of @samp{-}; that argument is preserved in repetition so that
6234 each repetition moves up in the source file.
6236 In general, the @code{list} command expects you to supply zero, one or two
6237 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6238 of writing them (@pxref{Specify Location}), but the effect is always
6239 to specify some source line.
6241 Here is a complete description of the possible arguments for @code{list}:
6244 @item list @var{linespec}
6245 Print lines centered around the line specified by @var{linespec}.
6247 @item list @var{first},@var{last}
6248 Print lines from @var{first} to @var{last}. Both arguments are
6249 linespecs. When a @code{list} command has two linespecs, and the
6250 source file of the second linespec is omitted, this refers to
6251 the same source file as the first linespec.
6253 @item list ,@var{last}
6254 Print lines ending with @var{last}.
6256 @item list @var{first},
6257 Print lines starting with @var{first}.
6260 Print lines just after the lines last printed.
6263 Print lines just before the lines last printed.
6266 As described in the preceding table.
6269 @node Specify Location
6270 @section Specifying a Location
6271 @cindex specifying location
6274 Several @value{GDBN} commands accept arguments that specify a location
6275 of your program's code. Since @value{GDBN} is a source-level
6276 debugger, a location usually specifies some line in the source code;
6277 for that reason, locations are also known as @dfn{linespecs}.
6279 Here are all the different ways of specifying a code location that
6280 @value{GDBN} understands:
6284 Specifies the line number @var{linenum} of the current source file.
6287 @itemx +@var{offset}
6288 Specifies the line @var{offset} lines before or after the @dfn{current
6289 line}. For the @code{list} command, the current line is the last one
6290 printed; for the breakpoint commands, this is the line at which
6291 execution stopped in the currently selected @dfn{stack frame}
6292 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6293 used as the second of the two linespecs in a @code{list} command,
6294 this specifies the line @var{offset} lines up or down from the first
6297 @item @var{filename}:@var{linenum}
6298 Specifies the line @var{linenum} in the source file @var{filename}.
6300 @item @var{function}
6301 Specifies the line that begins the body of the function @var{function}.
6302 For example, in C, this is the line with the open brace.
6304 @item @var{filename}:@var{function}
6305 Specifies the line that begins the body of the function @var{function}
6306 in the file @var{filename}. You only need the file name with a
6307 function name to avoid ambiguity when there are identically named
6308 functions in different source files.
6310 @item *@var{address}
6311 Specifies the program address @var{address}. For line-oriented
6312 commands, such as @code{list} and @code{edit}, this specifies a source
6313 line that contains @var{address}. For @code{break} and other
6314 breakpoint oriented commands, this can be used to set breakpoints in
6315 parts of your program which do not have debugging information or
6318 Here @var{address} may be any expression valid in the current working
6319 language (@pxref{Languages, working language}) that specifies a code
6320 address. In addition, as a convenience, @value{GDBN} extends the
6321 semantics of expressions used in locations to cover the situations
6322 that frequently happen during debugging. Here are the various forms
6326 @item @var{expression}
6327 Any expression valid in the current working language.
6329 @item @var{funcaddr}
6330 An address of a function or procedure derived from its name. In C,
6331 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6332 simply the function's name @var{function} (and actually a special case
6333 of a valid expression). In Pascal and Modula-2, this is
6334 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6335 (although the Pascal form also works).
6337 This form specifies the address of the function's first instruction,
6338 before the stack frame and arguments have been set up.
6340 @item '@var{filename}'::@var{funcaddr}
6341 Like @var{funcaddr} above, but also specifies the name of the source
6342 file explicitly. This is useful if the name of the function does not
6343 specify the function unambiguously, e.g., if there are several
6344 functions with identical names in different source files.
6351 @section Editing Source Files
6352 @cindex editing source files
6355 @kindex e @r{(@code{edit})}
6356 To edit the lines in a source file, use the @code{edit} command.
6357 The editing program of your choice
6358 is invoked with the current line set to
6359 the active line in the program.
6360 Alternatively, there are several ways to specify what part of the file you
6361 want to print if you want to see other parts of the program:
6364 @item edit @var{location}
6365 Edit the source file specified by @code{location}. Editing starts at
6366 that @var{location}, e.g., at the specified source line of the
6367 specified file. @xref{Specify Location}, for all the possible forms
6368 of the @var{location} argument; here are the forms of the @code{edit}
6369 command most commonly used:
6372 @item edit @var{number}
6373 Edit the current source file with @var{number} as the active line number.
6375 @item edit @var{function}
6376 Edit the file containing @var{function} at the beginning of its definition.
6381 @subsection Choosing your Editor
6382 You can customize @value{GDBN} to use any editor you want
6384 The only restriction is that your editor (say @code{ex}), recognizes the
6385 following command-line syntax:
6387 ex +@var{number} file
6389 The optional numeric value +@var{number} specifies the number of the line in
6390 the file where to start editing.}.
6391 By default, it is @file{@value{EDITOR}}, but you can change this
6392 by setting the environment variable @code{EDITOR} before using
6393 @value{GDBN}. For example, to configure @value{GDBN} to use the
6394 @code{vi} editor, you could use these commands with the @code{sh} shell:
6400 or in the @code{csh} shell,
6402 setenv EDITOR /usr/bin/vi
6407 @section Searching Source Files
6408 @cindex searching source files
6410 There are two commands for searching through the current source file for a
6415 @kindex forward-search
6416 @item forward-search @var{regexp}
6417 @itemx search @var{regexp}
6418 The command @samp{forward-search @var{regexp}} checks each line,
6419 starting with the one following the last line listed, for a match for
6420 @var{regexp}. It lists the line that is found. You can use the
6421 synonym @samp{search @var{regexp}} or abbreviate the command name as
6424 @kindex reverse-search
6425 @item reverse-search @var{regexp}
6426 The command @samp{reverse-search @var{regexp}} checks each line, starting
6427 with the one before the last line listed and going backward, for a match
6428 for @var{regexp}. It lists the line that is found. You can abbreviate
6429 this command as @code{rev}.
6433 @section Specifying Source Directories
6436 @cindex directories for source files
6437 Executable programs sometimes do not record the directories of the source
6438 files from which they were compiled, just the names. Even when they do,
6439 the directories could be moved between the compilation and your debugging
6440 session. @value{GDBN} has a list of directories to search for source files;
6441 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6442 it tries all the directories in the list, in the order they are present
6443 in the list, until it finds a file with the desired name.
6445 For example, suppose an executable references the file
6446 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6447 @file{/mnt/cross}. The file is first looked up literally; if this
6448 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6449 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6450 message is printed. @value{GDBN} does not look up the parts of the
6451 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6452 Likewise, the subdirectories of the source path are not searched: if
6453 the source path is @file{/mnt/cross}, and the binary refers to
6454 @file{foo.c}, @value{GDBN} would not find it under
6455 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6457 Plain file names, relative file names with leading directories, file
6458 names containing dots, etc.@: are all treated as described above; for
6459 instance, if the source path is @file{/mnt/cross}, and the source file
6460 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6461 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6462 that---@file{/mnt/cross/foo.c}.
6464 Note that the executable search path is @emph{not} used to locate the
6467 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6468 any information it has cached about where source files are found and where
6469 each line is in the file.
6473 When you start @value{GDBN}, its source path includes only @samp{cdir}
6474 and @samp{cwd}, in that order.
6475 To add other directories, use the @code{directory} command.
6477 The search path is used to find both program source files and @value{GDBN}
6478 script files (read using the @samp{-command} option and @samp{source} command).
6480 In addition to the source path, @value{GDBN} provides a set of commands
6481 that manage a list of source path substitution rules. A @dfn{substitution
6482 rule} specifies how to rewrite source directories stored in the program's
6483 debug information in case the sources were moved to a different
6484 directory between compilation and debugging. A rule is made of
6485 two strings, the first specifying what needs to be rewritten in
6486 the path, and the second specifying how it should be rewritten.
6487 In @ref{set substitute-path}, we name these two parts @var{from} and
6488 @var{to} respectively. @value{GDBN} does a simple string replacement
6489 of @var{from} with @var{to} at the start of the directory part of the
6490 source file name, and uses that result instead of the original file
6491 name to look up the sources.
6493 Using the previous example, suppose the @file{foo-1.0} tree has been
6494 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6495 @value{GDBN} to replace @file{/usr/src} in all source path names with
6496 @file{/mnt/cross}. The first lookup will then be
6497 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6498 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6499 substitution rule, use the @code{set substitute-path} command
6500 (@pxref{set substitute-path}).
6502 To avoid unexpected substitution results, a rule is applied only if the
6503 @var{from} part of the directory name ends at a directory separator.
6504 For instance, a rule substituting @file{/usr/source} into
6505 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6506 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6507 is applied only at the beginning of the directory name, this rule will
6508 not be applied to @file{/root/usr/source/baz.c} either.
6510 In many cases, you can achieve the same result using the @code{directory}
6511 command. However, @code{set substitute-path} can be more efficient in
6512 the case where the sources are organized in a complex tree with multiple
6513 subdirectories. With the @code{directory} command, you need to add each
6514 subdirectory of your project. If you moved the entire tree while
6515 preserving its internal organization, then @code{set substitute-path}
6516 allows you to direct the debugger to all the sources with one single
6519 @code{set substitute-path} is also more than just a shortcut command.
6520 The source path is only used if the file at the original location no
6521 longer exists. On the other hand, @code{set substitute-path} modifies
6522 the debugger behavior to look at the rewritten location instead. So, if
6523 for any reason a source file that is not relevant to your executable is
6524 located at the original location, a substitution rule is the only
6525 method available to point @value{GDBN} at the new location.
6527 @cindex @samp{--with-relocated-sources}
6528 @cindex default source path substitution
6529 You can configure a default source path substitution rule by
6530 configuring @value{GDBN} with the
6531 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6532 should be the name of a directory under @value{GDBN}'s configured
6533 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6534 directory names in debug information under @var{dir} will be adjusted
6535 automatically if the installed @value{GDBN} is moved to a new
6536 location. This is useful if @value{GDBN}, libraries or executables
6537 with debug information and corresponding source code are being moved
6541 @item directory @var{dirname} @dots{}
6542 @item dir @var{dirname} @dots{}
6543 Add directory @var{dirname} to the front of the source path. Several
6544 directory names may be given to this command, separated by @samp{:}
6545 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6546 part of absolute file names) or
6547 whitespace. You may specify a directory that is already in the source
6548 path; this moves it forward, so @value{GDBN} searches it sooner.
6552 @vindex $cdir@r{, convenience variable}
6553 @vindex $cwd@r{, convenience variable}
6554 @cindex compilation directory
6555 @cindex current directory
6556 @cindex working directory
6557 @cindex directory, current
6558 @cindex directory, compilation
6559 You can use the string @samp{$cdir} to refer to the compilation
6560 directory (if one is recorded), and @samp{$cwd} to refer to the current
6561 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6562 tracks the current working directory as it changes during your @value{GDBN}
6563 session, while the latter is immediately expanded to the current
6564 directory at the time you add an entry to the source path.
6567 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6569 @c RET-repeat for @code{directory} is explicitly disabled, but since
6570 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6572 @item show directories
6573 @kindex show directories
6574 Print the source path: show which directories it contains.
6576 @anchor{set substitute-path}
6577 @item set substitute-path @var{from} @var{to}
6578 @kindex set substitute-path
6579 Define a source path substitution rule, and add it at the end of the
6580 current list of existing substitution rules. If a rule with the same
6581 @var{from} was already defined, then the old rule is also deleted.
6583 For example, if the file @file{/foo/bar/baz.c} was moved to
6584 @file{/mnt/cross/baz.c}, then the command
6587 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6591 will tell @value{GDBN} to replace @samp{/usr/src} with
6592 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6593 @file{baz.c} even though it was moved.
6595 In the case when more than one substitution rule have been defined,
6596 the rules are evaluated one by one in the order where they have been
6597 defined. The first one matching, if any, is selected to perform
6600 For instance, if we had entered the following commands:
6603 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6604 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6608 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6609 @file{/mnt/include/defs.h} by using the first rule. However, it would
6610 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6611 @file{/mnt/src/lib/foo.c}.
6614 @item unset substitute-path [path]
6615 @kindex unset substitute-path
6616 If a path is specified, search the current list of substitution rules
6617 for a rule that would rewrite that path. Delete that rule if found.
6618 A warning is emitted by the debugger if no rule could be found.
6620 If no path is specified, then all substitution rules are deleted.
6622 @item show substitute-path [path]
6623 @kindex show substitute-path
6624 If a path is specified, then print the source path substitution rule
6625 which would rewrite that path, if any.
6627 If no path is specified, then print all existing source path substitution
6632 If your source path is cluttered with directories that are no longer of
6633 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6634 versions of source. You can correct the situation as follows:
6638 Use @code{directory} with no argument to reset the source path to its default value.
6641 Use @code{directory} with suitable arguments to reinstall the
6642 directories you want in the source path. You can add all the
6643 directories in one command.
6647 @section Source and Machine Code
6648 @cindex source line and its code address
6650 You can use the command @code{info line} to map source lines to program
6651 addresses (and vice versa), and the command @code{disassemble} to display
6652 a range of addresses as machine instructions. You can use the command
6653 @code{set disassemble-next-line} to set whether to disassemble next
6654 source line when execution stops. When run under @sc{gnu} Emacs
6655 mode, the @code{info line} command causes the arrow to point to the
6656 line specified. Also, @code{info line} prints addresses in symbolic form as
6661 @item info line @var{linespec}
6662 Print the starting and ending addresses of the compiled code for
6663 source line @var{linespec}. You can specify source lines in any of
6664 the ways documented in @ref{Specify Location}.
6667 For example, we can use @code{info line} to discover the location of
6668 the object code for the first line of function
6669 @code{m4_changequote}:
6671 @c FIXME: I think this example should also show the addresses in
6672 @c symbolic form, as they usually would be displayed.
6674 (@value{GDBP}) info line m4_changequote
6675 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6679 @cindex code address and its source line
6680 We can also inquire (using @code{*@var{addr}} as the form for
6681 @var{linespec}) what source line covers a particular address:
6683 (@value{GDBP}) info line *0x63ff
6684 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6687 @cindex @code{$_} and @code{info line}
6688 @cindex @code{x} command, default address
6689 @kindex x@r{(examine), and} info line
6690 After @code{info line}, the default address for the @code{x} command
6691 is changed to the starting address of the line, so that @samp{x/i} is
6692 sufficient to begin examining the machine code (@pxref{Memory,
6693 ,Examining Memory}). Also, this address is saved as the value of the
6694 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6699 @cindex assembly instructions
6700 @cindex instructions, assembly
6701 @cindex machine instructions
6702 @cindex listing machine instructions
6704 @itemx disassemble /m
6705 @itemx disassemble /r
6706 This specialized command dumps a range of memory as machine
6707 instructions. It can also print mixed source+disassembly by specifying
6708 the @code{/m} modifier and print the raw instructions in hex as well as
6709 in symbolic form by specifying the @code{/r}.
6710 The default memory range is the function surrounding the
6711 program counter of the selected frame. A single argument to this
6712 command is a program counter value; @value{GDBN} dumps the function
6713 surrounding this value. When two arguments are given, they should
6714 be separated by a comma, possibly surrounded by whitespace. The
6715 arguments specify a range of addresses (first inclusive, second exclusive)
6716 to dump. In that case, the name of the function is also printed (since
6717 there could be several functions in the given range).
6719 The argument(s) can be any expression yielding a numeric value, such as
6720 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6722 If the range of memory being disassembled contains current program counter,
6723 the instruction at that location is shown with a @code{=>} marker.
6726 The following example shows the disassembly of a range of addresses of
6727 HP PA-RISC 2.0 code:
6730 (@value{GDBP}) disas 0x32c4, 0x32e4
6731 Dump of assembler code from 0x32c4 to 0x32e4:
6732 0x32c4 <main+204>: addil 0,dp
6733 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6734 0x32cc <main+212>: ldil 0x3000,r31
6735 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6736 0x32d4 <main+220>: ldo 0(r31),rp
6737 0x32d8 <main+224>: addil -0x800,dp
6738 0x32dc <main+228>: ldo 0x588(r1),r26
6739 0x32e0 <main+232>: ldil 0x3000,r31
6740 End of assembler dump.
6743 Here is an example showing mixed source+assembly for Intel x86, when the
6744 program is stopped just after function prologue:
6747 (@value{GDBP}) disas /m main
6748 Dump of assembler code for function main:
6750 0x08048330 <+0>: push %ebp
6751 0x08048331 <+1>: mov %esp,%ebp
6752 0x08048333 <+3>: sub $0x8,%esp
6753 0x08048336 <+6>: and $0xfffffff0,%esp
6754 0x08048339 <+9>: sub $0x10,%esp
6756 6 printf ("Hello.\n");
6757 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6758 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6762 0x08048348 <+24>: mov $0x0,%eax
6763 0x0804834d <+29>: leave
6764 0x0804834e <+30>: ret
6766 End of assembler dump.
6769 Some architectures have more than one commonly-used set of instruction
6770 mnemonics or other syntax.
6772 For programs that were dynamically linked and use shared libraries,
6773 instructions that call functions or branch to locations in the shared
6774 libraries might show a seemingly bogus location---it's actually a
6775 location of the relocation table. On some architectures, @value{GDBN}
6776 might be able to resolve these to actual function names.
6779 @kindex set disassembly-flavor
6780 @cindex Intel disassembly flavor
6781 @cindex AT&T disassembly flavor
6782 @item set disassembly-flavor @var{instruction-set}
6783 Select the instruction set to use when disassembling the
6784 program via the @code{disassemble} or @code{x/i} commands.
6786 Currently this command is only defined for the Intel x86 family. You
6787 can set @var{instruction-set} to either @code{intel} or @code{att}.
6788 The default is @code{att}, the AT&T flavor used by default by Unix
6789 assemblers for x86-based targets.
6791 @kindex show disassembly-flavor
6792 @item show disassembly-flavor
6793 Show the current setting of the disassembly flavor.
6797 @kindex set disassemble-next-line
6798 @kindex show disassemble-next-line
6799 @item set disassemble-next-line
6800 @itemx show disassemble-next-line
6801 Control whether or not @value{GDBN} will disassemble the next source
6802 line or instruction when execution stops. If ON, @value{GDBN} will
6803 display disassembly of the next source line when execution of the
6804 program being debugged stops. This is @emph{in addition} to
6805 displaying the source line itself, which @value{GDBN} always does if
6806 possible. If the next source line cannot be displayed for some reason
6807 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6808 info in the debug info), @value{GDBN} will display disassembly of the
6809 next @emph{instruction} instead of showing the next source line. If
6810 AUTO, @value{GDBN} will display disassembly of next instruction only
6811 if the source line cannot be displayed. This setting causes
6812 @value{GDBN} to display some feedback when you step through a function
6813 with no line info or whose source file is unavailable. The default is
6814 OFF, which means never display the disassembly of the next line or
6820 @chapter Examining Data
6822 @cindex printing data
6823 @cindex examining data
6826 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6827 @c document because it is nonstandard... Under Epoch it displays in a
6828 @c different window or something like that.
6829 The usual way to examine data in your program is with the @code{print}
6830 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6831 evaluates and prints the value of an expression of the language your
6832 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6833 Different Languages}). It may also print the expression using a
6834 Python-based pretty-printer (@pxref{Pretty Printing}).
6837 @item print @var{expr}
6838 @itemx print /@var{f} @var{expr}
6839 @var{expr} is an expression (in the source language). By default the
6840 value of @var{expr} is printed in a format appropriate to its data type;
6841 you can choose a different format by specifying @samp{/@var{f}}, where
6842 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6846 @itemx print /@var{f}
6847 @cindex reprint the last value
6848 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6849 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6850 conveniently inspect the same value in an alternative format.
6853 A more low-level way of examining data is with the @code{x} command.
6854 It examines data in memory at a specified address and prints it in a
6855 specified format. @xref{Memory, ,Examining Memory}.
6857 If you are interested in information about types, or about how the
6858 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6859 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6863 * Expressions:: Expressions
6864 * Ambiguous Expressions:: Ambiguous Expressions
6865 * Variables:: Program variables
6866 * Arrays:: Artificial arrays
6867 * Output Formats:: Output formats
6868 * Memory:: Examining memory
6869 * Auto Display:: Automatic display
6870 * Print Settings:: Print settings
6871 * Pretty Printing:: Python pretty printing
6872 * Value History:: Value history
6873 * Convenience Vars:: Convenience variables
6874 * Registers:: Registers
6875 * Floating Point Hardware:: Floating point hardware
6876 * Vector Unit:: Vector Unit
6877 * OS Information:: Auxiliary data provided by operating system
6878 * Memory Region Attributes:: Memory region attributes
6879 * Dump/Restore Files:: Copy between memory and a file
6880 * Core File Generation:: Cause a program dump its core
6881 * Character Sets:: Debugging programs that use a different
6882 character set than GDB does
6883 * Caching Remote Data:: Data caching for remote targets
6884 * Searching Memory:: Searching memory for a sequence of bytes
6888 @section Expressions
6891 @code{print} and many other @value{GDBN} commands accept an expression and
6892 compute its value. Any kind of constant, variable or operator defined
6893 by the programming language you are using is valid in an expression in
6894 @value{GDBN}. This includes conditional expressions, function calls,
6895 casts, and string constants. It also includes preprocessor macros, if
6896 you compiled your program to include this information; see
6899 @cindex arrays in expressions
6900 @value{GDBN} supports array constants in expressions input by
6901 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6902 you can use the command @code{print @{1, 2, 3@}} to create an array
6903 of three integers. If you pass an array to a function or assign it
6904 to a program variable, @value{GDBN} copies the array to memory that
6905 is @code{malloc}ed in the target program.
6907 Because C is so widespread, most of the expressions shown in examples in
6908 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6909 Languages}, for information on how to use expressions in other
6912 In this section, we discuss operators that you can use in @value{GDBN}
6913 expressions regardless of your programming language.
6915 @cindex casts, in expressions
6916 Casts are supported in all languages, not just in C, because it is so
6917 useful to cast a number into a pointer in order to examine a structure
6918 at that address in memory.
6919 @c FIXME: casts supported---Mod2 true?
6921 @value{GDBN} supports these operators, in addition to those common
6922 to programming languages:
6926 @samp{@@} is a binary operator for treating parts of memory as arrays.
6927 @xref{Arrays, ,Artificial Arrays}, for more information.
6930 @samp{::} allows you to specify a variable in terms of the file or
6931 function where it is defined. @xref{Variables, ,Program Variables}.
6933 @cindex @{@var{type}@}
6934 @cindex type casting memory
6935 @cindex memory, viewing as typed object
6936 @cindex casts, to view memory
6937 @item @{@var{type}@} @var{addr}
6938 Refers to an object of type @var{type} stored at address @var{addr} in
6939 memory. @var{addr} may be any expression whose value is an integer or
6940 pointer (but parentheses are required around binary operators, just as in
6941 a cast). This construct is allowed regardless of what kind of data is
6942 normally supposed to reside at @var{addr}.
6945 @node Ambiguous Expressions
6946 @section Ambiguous Expressions
6947 @cindex ambiguous expressions
6949 Expressions can sometimes contain some ambiguous elements. For instance,
6950 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6951 a single function name to be defined several times, for application in
6952 different contexts. This is called @dfn{overloading}. Another example
6953 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6954 templates and is typically instantiated several times, resulting in
6955 the same function name being defined in different contexts.
6957 In some cases and depending on the language, it is possible to adjust
6958 the expression to remove the ambiguity. For instance in C@t{++}, you
6959 can specify the signature of the function you want to break on, as in
6960 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6961 qualified name of your function often makes the expression unambiguous
6964 When an ambiguity that needs to be resolved is detected, the debugger
6965 has the capability to display a menu of numbered choices for each
6966 possibility, and then waits for the selection with the prompt @samp{>}.
6967 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6968 aborts the current command. If the command in which the expression was
6969 used allows more than one choice to be selected, the next option in the
6970 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6973 For example, the following session excerpt shows an attempt to set a
6974 breakpoint at the overloaded symbol @code{String::after}.
6975 We choose three particular definitions of that function name:
6977 @c FIXME! This is likely to change to show arg type lists, at least
6980 (@value{GDBP}) b String::after
6983 [2] file:String.cc; line number:867
6984 [3] file:String.cc; line number:860
6985 [4] file:String.cc; line number:875
6986 [5] file:String.cc; line number:853
6987 [6] file:String.cc; line number:846
6988 [7] file:String.cc; line number:735
6990 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6991 Breakpoint 2 at 0xb344: file String.cc, line 875.
6992 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6993 Multiple breakpoints were set.
6994 Use the "delete" command to delete unwanted
7001 @kindex set multiple-symbols
7002 @item set multiple-symbols @var{mode}
7003 @cindex multiple-symbols menu
7005 This option allows you to adjust the debugger behavior when an expression
7008 By default, @var{mode} is set to @code{all}. If the command with which
7009 the expression is used allows more than one choice, then @value{GDBN}
7010 automatically selects all possible choices. For instance, inserting
7011 a breakpoint on a function using an ambiguous name results in a breakpoint
7012 inserted on each possible match. However, if a unique choice must be made,
7013 then @value{GDBN} uses the menu to help you disambiguate the expression.
7014 For instance, printing the address of an overloaded function will result
7015 in the use of the menu.
7017 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7018 when an ambiguity is detected.
7020 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7021 an error due to the ambiguity and the command is aborted.
7023 @kindex show multiple-symbols
7024 @item show multiple-symbols
7025 Show the current value of the @code{multiple-symbols} setting.
7029 @section Program Variables
7031 The most common kind of expression to use is the name of a variable
7034 Variables in expressions are understood in the selected stack frame
7035 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7039 global (or file-static)
7046 visible according to the scope rules of the
7047 programming language from the point of execution in that frame
7050 @noindent This means that in the function
7065 you can examine and use the variable @code{a} whenever your program is
7066 executing within the function @code{foo}, but you can only use or
7067 examine the variable @code{b} while your program is executing inside
7068 the block where @code{b} is declared.
7070 @cindex variable name conflict
7071 There is an exception: you can refer to a variable or function whose
7072 scope is a single source file even if the current execution point is not
7073 in this file. But it is possible to have more than one such variable or
7074 function with the same name (in different source files). If that
7075 happens, referring to that name has unpredictable effects. If you wish,
7076 you can specify a static variable in a particular function or file,
7077 using the colon-colon (@code{::}) notation:
7079 @cindex colon-colon, context for variables/functions
7081 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7082 @cindex @code{::}, context for variables/functions
7085 @var{file}::@var{variable}
7086 @var{function}::@var{variable}
7090 Here @var{file} or @var{function} is the name of the context for the
7091 static @var{variable}. In the case of file names, you can use quotes to
7092 make sure @value{GDBN} parses the file name as a single word---for example,
7093 to print a global value of @code{x} defined in @file{f2.c}:
7096 (@value{GDBP}) p 'f2.c'::x
7099 @cindex C@t{++} scope resolution
7100 This use of @samp{::} is very rarely in conflict with the very similar
7101 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7102 scope resolution operator in @value{GDBN} expressions.
7103 @c FIXME: Um, so what happens in one of those rare cases where it's in
7106 @cindex wrong values
7107 @cindex variable values, wrong
7108 @cindex function entry/exit, wrong values of variables
7109 @cindex optimized code, wrong values of variables
7111 @emph{Warning:} Occasionally, a local variable may appear to have the
7112 wrong value at certain points in a function---just after entry to a new
7113 scope, and just before exit.
7115 You may see this problem when you are stepping by machine instructions.
7116 This is because, on most machines, it takes more than one instruction to
7117 set up a stack frame (including local variable definitions); if you are
7118 stepping by machine instructions, variables may appear to have the wrong
7119 values until the stack frame is completely built. On exit, it usually
7120 also takes more than one machine instruction to destroy a stack frame;
7121 after you begin stepping through that group of instructions, local
7122 variable definitions may be gone.
7124 This may also happen when the compiler does significant optimizations.
7125 To be sure of always seeing accurate values, turn off all optimization
7128 @cindex ``No symbol "foo" in current context''
7129 Another possible effect of compiler optimizations is to optimize
7130 unused variables out of existence, or assign variables to registers (as
7131 opposed to memory addresses). Depending on the support for such cases
7132 offered by the debug info format used by the compiler, @value{GDBN}
7133 might not be able to display values for such local variables. If that
7134 happens, @value{GDBN} will print a message like this:
7137 No symbol "foo" in current context.
7140 To solve such problems, either recompile without optimizations, or use a
7141 different debug info format, if the compiler supports several such
7142 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7143 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7144 produces debug info in a format that is superior to formats such as
7145 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7146 an effective form for debug info. @xref{Debugging Options,,Options
7147 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7148 Compiler Collection (GCC)}.
7149 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7150 that are best suited to C@t{++} programs.
7152 If you ask to print an object whose contents are unknown to
7153 @value{GDBN}, e.g., because its data type is not completely specified
7154 by the debug information, @value{GDBN} will say @samp{<incomplete
7155 type>}. @xref{Symbols, incomplete type}, for more about this.
7157 Strings are identified as arrays of @code{char} values without specified
7158 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7159 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7160 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7161 defines literal string type @code{"char"} as @code{char} without a sign.
7166 signed char var1[] = "A";
7169 You get during debugging
7174 $2 = @{65 'A', 0 '\0'@}
7178 @section Artificial Arrays
7180 @cindex artificial array
7182 @kindex @@@r{, referencing memory as an array}
7183 It is often useful to print out several successive objects of the
7184 same type in memory; a section of an array, or an array of
7185 dynamically determined size for which only a pointer exists in the
7188 You can do this by referring to a contiguous span of memory as an
7189 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7190 operand of @samp{@@} should be the first element of the desired array
7191 and be an individual object. The right operand should be the desired length
7192 of the array. The result is an array value whose elements are all of
7193 the type of the left argument. The first element is actually the left
7194 argument; the second element comes from bytes of memory immediately
7195 following those that hold the first element, and so on. Here is an
7196 example. If a program says
7199 int *array = (int *) malloc (len * sizeof (int));
7203 you can print the contents of @code{array} with
7209 The left operand of @samp{@@} must reside in memory. Array values made
7210 with @samp{@@} in this way behave just like other arrays in terms of
7211 subscripting, and are coerced to pointers when used in expressions.
7212 Artificial arrays most often appear in expressions via the value history
7213 (@pxref{Value History, ,Value History}), after printing one out.
7215 Another way to create an artificial array is to use a cast.
7216 This re-interprets a value as if it were an array.
7217 The value need not be in memory:
7219 (@value{GDBP}) p/x (short[2])0x12345678
7220 $1 = @{0x1234, 0x5678@}
7223 As a convenience, if you leave the array length out (as in
7224 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7225 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7227 (@value{GDBP}) p/x (short[])0x12345678
7228 $2 = @{0x1234, 0x5678@}
7231 Sometimes the artificial array mechanism is not quite enough; in
7232 moderately complex data structures, the elements of interest may not
7233 actually be adjacent---for example, if you are interested in the values
7234 of pointers in an array. One useful work-around in this situation is
7235 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7236 Variables}) as a counter in an expression that prints the first
7237 interesting value, and then repeat that expression via @key{RET}. For
7238 instance, suppose you have an array @code{dtab} of pointers to
7239 structures, and you are interested in the values of a field @code{fv}
7240 in each structure. Here is an example of what you might type:
7250 @node Output Formats
7251 @section Output Formats
7253 @cindex formatted output
7254 @cindex output formats
7255 By default, @value{GDBN} prints a value according to its data type. Sometimes
7256 this is not what you want. For example, you might want to print a number
7257 in hex, or a pointer in decimal. Or you might want to view data in memory
7258 at a certain address as a character string or as an instruction. To do
7259 these things, specify an @dfn{output format} when you print a value.
7261 The simplest use of output formats is to say how to print a value
7262 already computed. This is done by starting the arguments of the
7263 @code{print} command with a slash and a format letter. The format
7264 letters supported are:
7268 Regard the bits of the value as an integer, and print the integer in
7272 Print as integer in signed decimal.
7275 Print as integer in unsigned decimal.
7278 Print as integer in octal.
7281 Print as integer in binary. The letter @samp{t} stands for ``two''.
7282 @footnote{@samp{b} cannot be used because these format letters are also
7283 used with the @code{x} command, where @samp{b} stands for ``byte'';
7284 see @ref{Memory,,Examining Memory}.}
7287 @cindex unknown address, locating
7288 @cindex locate address
7289 Print as an address, both absolute in hexadecimal and as an offset from
7290 the nearest preceding symbol. You can use this format used to discover
7291 where (in what function) an unknown address is located:
7294 (@value{GDBP}) p/a 0x54320
7295 $3 = 0x54320 <_initialize_vx+396>
7299 The command @code{info symbol 0x54320} yields similar results.
7300 @xref{Symbols, info symbol}.
7303 Regard as an integer and print it as a character constant. This
7304 prints both the numerical value and its character representation. The
7305 character representation is replaced with the octal escape @samp{\nnn}
7306 for characters outside the 7-bit @sc{ascii} range.
7308 Without this format, @value{GDBN} displays @code{char},
7309 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7310 constants. Single-byte members of vectors are displayed as integer
7314 Regard the bits of the value as a floating point number and print
7315 using typical floating point syntax.
7318 @cindex printing strings
7319 @cindex printing byte arrays
7320 Regard as a string, if possible. With this format, pointers to single-byte
7321 data are displayed as null-terminated strings and arrays of single-byte data
7322 are displayed as fixed-length strings. Other values are displayed in their
7325 Without this format, @value{GDBN} displays pointers to and arrays of
7326 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7327 strings. Single-byte members of a vector are displayed as an integer
7331 @cindex raw printing
7332 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7333 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7334 Printing}). This typically results in a higher-level display of the
7335 value's contents. The @samp{r} format bypasses any Python
7336 pretty-printer which might exist.
7339 For example, to print the program counter in hex (@pxref{Registers}), type
7346 Note that no space is required before the slash; this is because command
7347 names in @value{GDBN} cannot contain a slash.
7349 To reprint the last value in the value history with a different format,
7350 you can use the @code{print} command with just a format and no
7351 expression. For example, @samp{p/x} reprints the last value in hex.
7354 @section Examining Memory
7356 You can use the command @code{x} (for ``examine'') to examine memory in
7357 any of several formats, independently of your program's data types.
7359 @cindex examining memory
7361 @kindex x @r{(examine memory)}
7362 @item x/@var{nfu} @var{addr}
7365 Use the @code{x} command to examine memory.
7368 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7369 much memory to display and how to format it; @var{addr} is an
7370 expression giving the address where you want to start displaying memory.
7371 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7372 Several commands set convenient defaults for @var{addr}.
7375 @item @var{n}, the repeat count
7376 The repeat count is a decimal integer; the default is 1. It specifies
7377 how much memory (counting by units @var{u}) to display.
7378 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7381 @item @var{f}, the display format
7382 The display format is one of the formats used by @code{print}
7383 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7384 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7385 The default is @samp{x} (hexadecimal) initially. The default changes
7386 each time you use either @code{x} or @code{print}.
7388 @item @var{u}, the unit size
7389 The unit size is any of
7395 Halfwords (two bytes).
7397 Words (four bytes). This is the initial default.
7399 Giant words (eight bytes).
7402 Each time you specify a unit size with @code{x}, that size becomes the
7403 default unit the next time you use @code{x}. For the @samp{i} format,
7404 the unit size is ignored and is normally not written. For the @samp{s} format,
7405 the unit size defaults to @samp{b}, unless it is explicitly given.
7406 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7407 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7408 Note that the results depend on the programming language of the
7409 current compilation unit. If the language is C, the @samp{s}
7410 modifier will use the UTF-16 encoding while @samp{w} will use
7411 UTF-32. The encoding is set by the programming language and cannot
7414 @item @var{addr}, starting display address
7415 @var{addr} is the address where you want @value{GDBN} to begin displaying
7416 memory. The expression need not have a pointer value (though it may);
7417 it is always interpreted as an integer address of a byte of memory.
7418 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7419 @var{addr} is usually just after the last address examined---but several
7420 other commands also set the default address: @code{info breakpoints} (to
7421 the address of the last breakpoint listed), @code{info line} (to the
7422 starting address of a line), and @code{print} (if you use it to display
7423 a value from memory).
7426 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7427 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7428 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7429 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7430 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7432 Since the letters indicating unit sizes are all distinct from the
7433 letters specifying output formats, you do not have to remember whether
7434 unit size or format comes first; either order works. The output
7435 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7436 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7438 Even though the unit size @var{u} is ignored for the formats @samp{s}
7439 and @samp{i}, you might still want to use a count @var{n}; for example,
7440 @samp{3i} specifies that you want to see three machine instructions,
7441 including any operands. For convenience, especially when used with
7442 the @code{display} command, the @samp{i} format also prints branch delay
7443 slot instructions, if any, beyond the count specified, which immediately
7444 follow the last instruction that is within the count. The command
7445 @code{disassemble} gives an alternative way of inspecting machine
7446 instructions; see @ref{Machine Code,,Source and Machine Code}.
7448 All the defaults for the arguments to @code{x} are designed to make it
7449 easy to continue scanning memory with minimal specifications each time
7450 you use @code{x}. For example, after you have inspected three machine
7451 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7452 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7453 the repeat count @var{n} is used again; the other arguments default as
7454 for successive uses of @code{x}.
7456 When examining machine instructions, the instruction at current program
7457 counter is shown with a @code{=>} marker. For example:
7460 (@value{GDBP}) x/5i $pc-6
7461 0x804837f <main+11>: mov %esp,%ebp
7462 0x8048381 <main+13>: push %ecx
7463 0x8048382 <main+14>: sub $0x4,%esp
7464 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7465 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7468 @cindex @code{$_}, @code{$__}, and value history
7469 The addresses and contents printed by the @code{x} command are not saved
7470 in the value history because there is often too much of them and they
7471 would get in the way. Instead, @value{GDBN} makes these values available for
7472 subsequent use in expressions as values of the convenience variables
7473 @code{$_} and @code{$__}. After an @code{x} command, the last address
7474 examined is available for use in expressions in the convenience variable
7475 @code{$_}. The contents of that address, as examined, are available in
7476 the convenience variable @code{$__}.
7478 If the @code{x} command has a repeat count, the address and contents saved
7479 are from the last memory unit printed; this is not the same as the last
7480 address printed if several units were printed on the last line of output.
7482 @cindex remote memory comparison
7483 @cindex verify remote memory image
7484 When you are debugging a program running on a remote target machine
7485 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7486 remote machine's memory against the executable file you downloaded to
7487 the target. The @code{compare-sections} command is provided for such
7491 @kindex compare-sections
7492 @item compare-sections @r{[}@var{section-name}@r{]}
7493 Compare the data of a loadable section @var{section-name} in the
7494 executable file of the program being debugged with the same section in
7495 the remote machine's memory, and report any mismatches. With no
7496 arguments, compares all loadable sections. This command's
7497 availability depends on the target's support for the @code{"qCRC"}
7502 @section Automatic Display
7503 @cindex automatic display
7504 @cindex display of expressions
7506 If you find that you want to print the value of an expression frequently
7507 (to see how it changes), you might want to add it to the @dfn{automatic
7508 display list} so that @value{GDBN} prints its value each time your program stops.
7509 Each expression added to the list is given a number to identify it;
7510 to remove an expression from the list, you specify that number.
7511 The automatic display looks like this:
7515 3: bar[5] = (struct hack *) 0x3804
7519 This display shows item numbers, expressions and their current values. As with
7520 displays you request manually using @code{x} or @code{print}, you can
7521 specify the output format you prefer; in fact, @code{display} decides
7522 whether to use @code{print} or @code{x} depending your format
7523 specification---it uses @code{x} if you specify either the @samp{i}
7524 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7528 @item display @var{expr}
7529 Add the expression @var{expr} to the list of expressions to display
7530 each time your program stops. @xref{Expressions, ,Expressions}.
7532 @code{display} does not repeat if you press @key{RET} again after using it.
7534 @item display/@var{fmt} @var{expr}
7535 For @var{fmt} specifying only a display format and not a size or
7536 count, add the expression @var{expr} to the auto-display list but
7537 arrange to display it each time in the specified format @var{fmt}.
7538 @xref{Output Formats,,Output Formats}.
7540 @item display/@var{fmt} @var{addr}
7541 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7542 number of units, add the expression @var{addr} as a memory address to
7543 be examined each time your program stops. Examining means in effect
7544 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7547 For example, @samp{display/i $pc} can be helpful, to see the machine
7548 instruction about to be executed each time execution stops (@samp{$pc}
7549 is a common name for the program counter; @pxref{Registers, ,Registers}).
7552 @kindex delete display
7554 @item undisplay @var{dnums}@dots{}
7555 @itemx delete display @var{dnums}@dots{}
7556 Remove item numbers @var{dnums} from the list of expressions to display.
7558 @code{undisplay} does not repeat if you press @key{RET} after using it.
7559 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7561 @kindex disable display
7562 @item disable display @var{dnums}@dots{}
7563 Disable the display of item numbers @var{dnums}. A disabled display
7564 item is not printed automatically, but is not forgotten. It may be
7565 enabled again later.
7567 @kindex enable display
7568 @item enable display @var{dnums}@dots{}
7569 Enable display of item numbers @var{dnums}. It becomes effective once
7570 again in auto display of its expression, until you specify otherwise.
7573 Display the current values of the expressions on the list, just as is
7574 done when your program stops.
7576 @kindex info display
7578 Print the list of expressions previously set up to display
7579 automatically, each one with its item number, but without showing the
7580 values. This includes disabled expressions, which are marked as such.
7581 It also includes expressions which would not be displayed right now
7582 because they refer to automatic variables not currently available.
7585 @cindex display disabled out of scope
7586 If a display expression refers to local variables, then it does not make
7587 sense outside the lexical context for which it was set up. Such an
7588 expression is disabled when execution enters a context where one of its
7589 variables is not defined. For example, if you give the command
7590 @code{display last_char} while inside a function with an argument
7591 @code{last_char}, @value{GDBN} displays this argument while your program
7592 continues to stop inside that function. When it stops elsewhere---where
7593 there is no variable @code{last_char}---the display is disabled
7594 automatically. The next time your program stops where @code{last_char}
7595 is meaningful, you can enable the display expression once again.
7597 @node Print Settings
7598 @section Print Settings
7600 @cindex format options
7601 @cindex print settings
7602 @value{GDBN} provides the following ways to control how arrays, structures,
7603 and symbols are printed.
7606 These settings are useful for debugging programs in any language:
7610 @item set print address
7611 @itemx set print address on
7612 @cindex print/don't print memory addresses
7613 @value{GDBN} prints memory addresses showing the location of stack
7614 traces, structure values, pointer values, breakpoints, and so forth,
7615 even when it also displays the contents of those addresses. The default
7616 is @code{on}. For example, this is what a stack frame display looks like with
7617 @code{set print address on}:
7622 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7624 530 if (lquote != def_lquote)
7628 @item set print address off
7629 Do not print addresses when displaying their contents. For example,
7630 this is the same stack frame displayed with @code{set print address off}:
7634 (@value{GDBP}) set print addr off
7636 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7637 530 if (lquote != def_lquote)
7641 You can use @samp{set print address off} to eliminate all machine
7642 dependent displays from the @value{GDBN} interface. For example, with
7643 @code{print address off}, you should get the same text for backtraces on
7644 all machines---whether or not they involve pointer arguments.
7647 @item show print address
7648 Show whether or not addresses are to be printed.
7651 When @value{GDBN} prints a symbolic address, it normally prints the
7652 closest earlier symbol plus an offset. If that symbol does not uniquely
7653 identify the address (for example, it is a name whose scope is a single
7654 source file), you may need to clarify. One way to do this is with
7655 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7656 you can set @value{GDBN} to print the source file and line number when
7657 it prints a symbolic address:
7660 @item set print symbol-filename on
7661 @cindex source file and line of a symbol
7662 @cindex symbol, source file and line
7663 Tell @value{GDBN} to print the source file name and line number of a
7664 symbol in the symbolic form of an address.
7666 @item set print symbol-filename off
7667 Do not print source file name and line number of a symbol. This is the
7670 @item show print symbol-filename
7671 Show whether or not @value{GDBN} will print the source file name and
7672 line number of a symbol in the symbolic form of an address.
7675 Another situation where it is helpful to show symbol filenames and line
7676 numbers is when disassembling code; @value{GDBN} shows you the line
7677 number and source file that corresponds to each instruction.
7679 Also, you may wish to see the symbolic form only if the address being
7680 printed is reasonably close to the closest earlier symbol:
7683 @item set print max-symbolic-offset @var{max-offset}
7684 @cindex maximum value for offset of closest symbol
7685 Tell @value{GDBN} to only display the symbolic form of an address if the
7686 offset between the closest earlier symbol and the address is less than
7687 @var{max-offset}. The default is 0, which tells @value{GDBN}
7688 to always print the symbolic form of an address if any symbol precedes it.
7690 @item show print max-symbolic-offset
7691 Ask how large the maximum offset is that @value{GDBN} prints in a
7695 @cindex wild pointer, interpreting
7696 @cindex pointer, finding referent
7697 If you have a pointer and you are not sure where it points, try
7698 @samp{set print symbol-filename on}. Then you can determine the name
7699 and source file location of the variable where it points, using
7700 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7701 For example, here @value{GDBN} shows that a variable @code{ptt} points
7702 at another variable @code{t}, defined in @file{hi2.c}:
7705 (@value{GDBP}) set print symbol-filename on
7706 (@value{GDBP}) p/a ptt
7707 $4 = 0xe008 <t in hi2.c>
7711 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7712 does not show the symbol name and filename of the referent, even with
7713 the appropriate @code{set print} options turned on.
7716 Other settings control how different kinds of objects are printed:
7719 @item set print array
7720 @itemx set print array on
7721 @cindex pretty print arrays
7722 Pretty print arrays. This format is more convenient to read,
7723 but uses more space. The default is off.
7725 @item set print array off
7726 Return to compressed format for arrays.
7728 @item show print array
7729 Show whether compressed or pretty format is selected for displaying
7732 @cindex print array indexes
7733 @item set print array-indexes
7734 @itemx set print array-indexes on
7735 Print the index of each element when displaying arrays. May be more
7736 convenient to locate a given element in the array or quickly find the
7737 index of a given element in that printed array. The default is off.
7739 @item set print array-indexes off
7740 Stop printing element indexes when displaying arrays.
7742 @item show print array-indexes
7743 Show whether the index of each element is printed when displaying
7746 @item set print elements @var{number-of-elements}
7747 @cindex number of array elements to print
7748 @cindex limit on number of printed array elements
7749 Set a limit on how many elements of an array @value{GDBN} will print.
7750 If @value{GDBN} is printing a large array, it stops printing after it has
7751 printed the number of elements set by the @code{set print elements} command.
7752 This limit also applies to the display of strings.
7753 When @value{GDBN} starts, this limit is set to 200.
7754 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7756 @item show print elements
7757 Display the number of elements of a large array that @value{GDBN} will print.
7758 If the number is 0, then the printing is unlimited.
7760 @item set print frame-arguments @var{value}
7761 @kindex set print frame-arguments
7762 @cindex printing frame argument values
7763 @cindex print all frame argument values
7764 @cindex print frame argument values for scalars only
7765 @cindex do not print frame argument values
7766 This command allows to control how the values of arguments are printed
7767 when the debugger prints a frame (@pxref{Frames}). The possible
7772 The values of all arguments are printed.
7775 Print the value of an argument only if it is a scalar. The value of more
7776 complex arguments such as arrays, structures, unions, etc, is replaced
7777 by @code{@dots{}}. This is the default. Here is an example where
7778 only scalar arguments are shown:
7781 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7786 None of the argument values are printed. Instead, the value of each argument
7787 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7790 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7795 By default, only scalar arguments are printed. This command can be used
7796 to configure the debugger to print the value of all arguments, regardless
7797 of their type. However, it is often advantageous to not print the value
7798 of more complex parameters. For instance, it reduces the amount of
7799 information printed in each frame, making the backtrace more readable.
7800 Also, it improves performance when displaying Ada frames, because
7801 the computation of large arguments can sometimes be CPU-intensive,
7802 especially in large applications. Setting @code{print frame-arguments}
7803 to @code{scalars} (the default) or @code{none} avoids this computation,
7804 thus speeding up the display of each Ada frame.
7806 @item show print frame-arguments
7807 Show how the value of arguments should be displayed when printing a frame.
7809 @item set print repeats
7810 @cindex repeated array elements
7811 Set the threshold for suppressing display of repeated array
7812 elements. When the number of consecutive identical elements of an
7813 array exceeds the threshold, @value{GDBN} prints the string
7814 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7815 identical repetitions, instead of displaying the identical elements
7816 themselves. Setting the threshold to zero will cause all elements to
7817 be individually printed. The default threshold is 10.
7819 @item show print repeats
7820 Display the current threshold for printing repeated identical
7823 @item set print null-stop
7824 @cindex @sc{null} elements in arrays
7825 Cause @value{GDBN} to stop printing the characters of an array when the first
7826 @sc{null} is encountered. This is useful when large arrays actually
7827 contain only short strings.
7830 @item show print null-stop
7831 Show whether @value{GDBN} stops printing an array on the first
7832 @sc{null} character.
7834 @item set print pretty on
7835 @cindex print structures in indented form
7836 @cindex indentation in structure display
7837 Cause @value{GDBN} to print structures in an indented format with one member
7838 per line, like this:
7853 @item set print pretty off
7854 Cause @value{GDBN} to print structures in a compact format, like this:
7858 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7859 meat = 0x54 "Pork"@}
7864 This is the default format.
7866 @item show print pretty
7867 Show which format @value{GDBN} is using to print structures.
7869 @item set print sevenbit-strings on
7870 @cindex eight-bit characters in strings
7871 @cindex octal escapes in strings
7872 Print using only seven-bit characters; if this option is set,
7873 @value{GDBN} displays any eight-bit characters (in strings or
7874 character values) using the notation @code{\}@var{nnn}. This setting is
7875 best if you are working in English (@sc{ascii}) and you use the
7876 high-order bit of characters as a marker or ``meta'' bit.
7878 @item set print sevenbit-strings off
7879 Print full eight-bit characters. This allows the use of more
7880 international character sets, and is the default.
7882 @item show print sevenbit-strings
7883 Show whether or not @value{GDBN} is printing only seven-bit characters.
7885 @item set print union on
7886 @cindex unions in structures, printing
7887 Tell @value{GDBN} to print unions which are contained in structures
7888 and other unions. This is the default setting.
7890 @item set print union off
7891 Tell @value{GDBN} not to print unions which are contained in
7892 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7895 @item show print union
7896 Ask @value{GDBN} whether or not it will print unions which are contained in
7897 structures and other unions.
7899 For example, given the declarations
7902 typedef enum @{Tree, Bug@} Species;
7903 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7904 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7915 struct thing foo = @{Tree, @{Acorn@}@};
7919 with @code{set print union on} in effect @samp{p foo} would print
7922 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7926 and with @code{set print union off} in effect it would print
7929 $1 = @{it = Tree, form = @{...@}@}
7933 @code{set print union} affects programs written in C-like languages
7939 These settings are of interest when debugging C@t{++} programs:
7942 @cindex demangling C@t{++} names
7943 @item set print demangle
7944 @itemx set print demangle on
7945 Print C@t{++} names in their source form rather than in the encoded
7946 (``mangled'') form passed to the assembler and linker for type-safe
7947 linkage. The default is on.
7949 @item show print demangle
7950 Show whether C@t{++} names are printed in mangled or demangled form.
7952 @item set print asm-demangle
7953 @itemx set print asm-demangle on
7954 Print C@t{++} names in their source form rather than their mangled form, even
7955 in assembler code printouts such as instruction disassemblies.
7958 @item show print asm-demangle
7959 Show whether C@t{++} names in assembly listings are printed in mangled
7962 @cindex C@t{++} symbol decoding style
7963 @cindex symbol decoding style, C@t{++}
7964 @kindex set demangle-style
7965 @item set demangle-style @var{style}
7966 Choose among several encoding schemes used by different compilers to
7967 represent C@t{++} names. The choices for @var{style} are currently:
7971 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7974 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7975 This is the default.
7978 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7981 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7984 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7985 @strong{Warning:} this setting alone is not sufficient to allow
7986 debugging @code{cfront}-generated executables. @value{GDBN} would
7987 require further enhancement to permit that.
7990 If you omit @var{style}, you will see a list of possible formats.
7992 @item show demangle-style
7993 Display the encoding style currently in use for decoding C@t{++} symbols.
7995 @item set print object
7996 @itemx set print object on
7997 @cindex derived type of an object, printing
7998 @cindex display derived types
7999 When displaying a pointer to an object, identify the @emph{actual}
8000 (derived) type of the object rather than the @emph{declared} type, using
8001 the virtual function table.
8003 @item set print object off
8004 Display only the declared type of objects, without reference to the
8005 virtual function table. This is the default setting.
8007 @item show print object
8008 Show whether actual, or declared, object types are displayed.
8010 @item set print static-members
8011 @itemx set print static-members on
8012 @cindex static members of C@t{++} objects
8013 Print static members when displaying a C@t{++} object. The default is on.
8015 @item set print static-members off
8016 Do not print static members when displaying a C@t{++} object.
8018 @item show print static-members
8019 Show whether C@t{++} static members are printed or not.
8021 @item set print pascal_static-members
8022 @itemx set print pascal_static-members on
8023 @cindex static members of Pascal objects
8024 @cindex Pascal objects, static members display
8025 Print static members when displaying a Pascal object. The default is on.
8027 @item set print pascal_static-members off
8028 Do not print static members when displaying a Pascal object.
8030 @item show print pascal_static-members
8031 Show whether Pascal static members are printed or not.
8033 @c These don't work with HP ANSI C++ yet.
8034 @item set print vtbl
8035 @itemx set print vtbl on
8036 @cindex pretty print C@t{++} virtual function tables
8037 @cindex virtual functions (C@t{++}) display
8038 @cindex VTBL display
8039 Pretty print C@t{++} virtual function tables. The default is off.
8040 (The @code{vtbl} commands do not work on programs compiled with the HP
8041 ANSI C@t{++} compiler (@code{aCC}).)
8043 @item set print vtbl off
8044 Do not pretty print C@t{++} virtual function tables.
8046 @item show print vtbl
8047 Show whether C@t{++} virtual function tables are pretty printed, or not.
8050 @node Pretty Printing
8051 @section Pretty Printing
8053 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8054 Python code. It greatly simplifies the display of complex objects. This
8055 mechanism works for both MI and the CLI.
8057 For example, here is how a C@t{++} @code{std::string} looks without a
8061 (@value{GDBP}) print s
8063 static npos = 4294967295,
8065 <std::allocator<char>> = @{
8066 <__gnu_cxx::new_allocator<char>> = @{
8067 <No data fields>@}, <No data fields>
8069 members of std::basic_string<char, std::char_traits<char>,
8070 std::allocator<char> >::_Alloc_hider:
8071 _M_p = 0x804a014 "abcd"
8076 With a pretty-printer for @code{std::string} only the contents are printed:
8079 (@value{GDBP}) print s
8083 For implementing pretty printers for new types you should read the Python API
8084 details (@pxref{Pretty Printing API}).
8087 @section Value History
8089 @cindex value history
8090 @cindex history of values printed by @value{GDBN}
8091 Values printed by the @code{print} command are saved in the @value{GDBN}
8092 @dfn{value history}. This allows you to refer to them in other expressions.
8093 Values are kept until the symbol table is re-read or discarded
8094 (for example with the @code{file} or @code{symbol-file} commands).
8095 When the symbol table changes, the value history is discarded,
8096 since the values may contain pointers back to the types defined in the
8101 @cindex history number
8102 The values printed are given @dfn{history numbers} by which you can
8103 refer to them. These are successive integers starting with one.
8104 @code{print} shows you the history number assigned to a value by
8105 printing @samp{$@var{num} = } before the value; here @var{num} is the
8108 To refer to any previous value, use @samp{$} followed by the value's
8109 history number. The way @code{print} labels its output is designed to
8110 remind you of this. Just @code{$} refers to the most recent value in
8111 the history, and @code{$$} refers to the value before that.
8112 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8113 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8114 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8116 For example, suppose you have just printed a pointer to a structure and
8117 want to see the contents of the structure. It suffices to type
8123 If you have a chain of structures where the component @code{next} points
8124 to the next one, you can print the contents of the next one with this:
8131 You can print successive links in the chain by repeating this
8132 command---which you can do by just typing @key{RET}.
8134 Note that the history records values, not expressions. If the value of
8135 @code{x} is 4 and you type these commands:
8143 then the value recorded in the value history by the @code{print} command
8144 remains 4 even though the value of @code{x} has changed.
8149 Print the last ten values in the value history, with their item numbers.
8150 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8151 values} does not change the history.
8153 @item show values @var{n}
8154 Print ten history values centered on history item number @var{n}.
8157 Print ten history values just after the values last printed. If no more
8158 values are available, @code{show values +} produces no display.
8161 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8162 same effect as @samp{show values +}.
8164 @node Convenience Vars
8165 @section Convenience Variables
8167 @cindex convenience variables
8168 @cindex user-defined variables
8169 @value{GDBN} provides @dfn{convenience variables} that you can use within
8170 @value{GDBN} to hold on to a value and refer to it later. These variables
8171 exist entirely within @value{GDBN}; they are not part of your program, and
8172 setting a convenience variable has no direct effect on further execution
8173 of your program. That is why you can use them freely.
8175 Convenience variables are prefixed with @samp{$}. Any name preceded by
8176 @samp{$} can be used for a convenience variable, unless it is one of
8177 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8178 (Value history references, in contrast, are @emph{numbers} preceded
8179 by @samp{$}. @xref{Value History, ,Value History}.)
8181 You can save a value in a convenience variable with an assignment
8182 expression, just as you would set a variable in your program.
8186 set $foo = *object_ptr
8190 would save in @code{$foo} the value contained in the object pointed to by
8193 Using a convenience variable for the first time creates it, but its
8194 value is @code{void} until you assign a new value. You can alter the
8195 value with another assignment at any time.
8197 Convenience variables have no fixed types. You can assign a convenience
8198 variable any type of value, including structures and arrays, even if
8199 that variable already has a value of a different type. The convenience
8200 variable, when used as an expression, has the type of its current value.
8203 @kindex show convenience
8204 @cindex show all user variables
8205 @item show convenience
8206 Print a list of convenience variables used so far, and their values.
8207 Abbreviated @code{show conv}.
8209 @kindex init-if-undefined
8210 @cindex convenience variables, initializing
8211 @item init-if-undefined $@var{variable} = @var{expression}
8212 Set a convenience variable if it has not already been set. This is useful
8213 for user-defined commands that keep some state. It is similar, in concept,
8214 to using local static variables with initializers in C (except that
8215 convenience variables are global). It can also be used to allow users to
8216 override default values used in a command script.
8218 If the variable is already defined then the expression is not evaluated so
8219 any side-effects do not occur.
8222 One of the ways to use a convenience variable is as a counter to be
8223 incremented or a pointer to be advanced. For example, to print
8224 a field from successive elements of an array of structures:
8228 print bar[$i++]->contents
8232 Repeat that command by typing @key{RET}.
8234 Some convenience variables are created automatically by @value{GDBN} and given
8235 values likely to be useful.
8238 @vindex $_@r{, convenience variable}
8240 The variable @code{$_} is automatically set by the @code{x} command to
8241 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8242 commands which provide a default address for @code{x} to examine also
8243 set @code{$_} to that address; these commands include @code{info line}
8244 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8245 except when set by the @code{x} command, in which case it is a pointer
8246 to the type of @code{$__}.
8248 @vindex $__@r{, convenience variable}
8250 The variable @code{$__} is automatically set by the @code{x} command
8251 to the value found in the last address examined. Its type is chosen
8252 to match the format in which the data was printed.
8255 @vindex $_exitcode@r{, convenience variable}
8256 The variable @code{$_exitcode} is automatically set to the exit code when
8257 the program being debugged terminates.
8260 @vindex $_siginfo@r{, convenience variable}
8261 The variable @code{$_siginfo} contains extra signal information
8262 (@pxref{extra signal information}). Note that @code{$_siginfo}
8263 could be empty, if the application has not yet received any signals.
8264 For example, it will be empty before you execute the @code{run} command.
8267 @vindex $_tlb@r{, convenience variable}
8268 The variable @code{$_tlb} is automatically set when debugging
8269 applications running on MS-Windows in native mode or connected to
8270 gdbserver that supports the @code{qGetTIBAddr} request.
8271 @xref{General Query Packets}.
8272 This variable contains the address of the thread information block.
8276 On HP-UX systems, if you refer to a function or variable name that
8277 begins with a dollar sign, @value{GDBN} searches for a user or system
8278 name first, before it searches for a convenience variable.
8280 @cindex convenience functions
8281 @value{GDBN} also supplies some @dfn{convenience functions}. These
8282 have a syntax similar to convenience variables. A convenience
8283 function can be used in an expression just like an ordinary function;
8284 however, a convenience function is implemented internally to
8289 @kindex help function
8290 @cindex show all convenience functions
8291 Print a list of all convenience functions.
8298 You can refer to machine register contents, in expressions, as variables
8299 with names starting with @samp{$}. The names of registers are different
8300 for each machine; use @code{info registers} to see the names used on
8304 @kindex info registers
8305 @item info registers
8306 Print the names and values of all registers except floating-point
8307 and vector registers (in the selected stack frame).
8309 @kindex info all-registers
8310 @cindex floating point registers
8311 @item info all-registers
8312 Print the names and values of all registers, including floating-point
8313 and vector registers (in the selected stack frame).
8315 @item info registers @var{regname} @dots{}
8316 Print the @dfn{relativized} value of each specified register @var{regname}.
8317 As discussed in detail below, register values are normally relative to
8318 the selected stack frame. @var{regname} may be any register name valid on
8319 the machine you are using, with or without the initial @samp{$}.
8322 @cindex stack pointer register
8323 @cindex program counter register
8324 @cindex process status register
8325 @cindex frame pointer register
8326 @cindex standard registers
8327 @value{GDBN} has four ``standard'' register names that are available (in
8328 expressions) on most machines---whenever they do not conflict with an
8329 architecture's canonical mnemonics for registers. The register names
8330 @code{$pc} and @code{$sp} are used for the program counter register and
8331 the stack pointer. @code{$fp} is used for a register that contains a
8332 pointer to the current stack frame, and @code{$ps} is used for a
8333 register that contains the processor status. For example,
8334 you could print the program counter in hex with
8341 or print the instruction to be executed next with
8348 or add four to the stack pointer@footnote{This is a way of removing
8349 one word from the stack, on machines where stacks grow downward in
8350 memory (most machines, nowadays). This assumes that the innermost
8351 stack frame is selected; setting @code{$sp} is not allowed when other
8352 stack frames are selected. To pop entire frames off the stack,
8353 regardless of machine architecture, use @code{return};
8354 see @ref{Returning, ,Returning from a Function}.} with
8360 Whenever possible, these four standard register names are available on
8361 your machine even though the machine has different canonical mnemonics,
8362 so long as there is no conflict. The @code{info registers} command
8363 shows the canonical names. For example, on the SPARC, @code{info
8364 registers} displays the processor status register as @code{$psr} but you
8365 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8366 is an alias for the @sc{eflags} register.
8368 @value{GDBN} always considers the contents of an ordinary register as an
8369 integer when the register is examined in this way. Some machines have
8370 special registers which can hold nothing but floating point; these
8371 registers are considered to have floating point values. There is no way
8372 to refer to the contents of an ordinary register as floating point value
8373 (although you can @emph{print} it as a floating point value with
8374 @samp{print/f $@var{regname}}).
8376 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8377 means that the data format in which the register contents are saved by
8378 the operating system is not the same one that your program normally
8379 sees. For example, the registers of the 68881 floating point
8380 coprocessor are always saved in ``extended'' (raw) format, but all C
8381 programs expect to work with ``double'' (virtual) format. In such
8382 cases, @value{GDBN} normally works with the virtual format only (the format
8383 that makes sense for your program), but the @code{info registers} command
8384 prints the data in both formats.
8386 @cindex SSE registers (x86)
8387 @cindex MMX registers (x86)
8388 Some machines have special registers whose contents can be interpreted
8389 in several different ways. For example, modern x86-based machines
8390 have SSE and MMX registers that can hold several values packed
8391 together in several different formats. @value{GDBN} refers to such
8392 registers in @code{struct} notation:
8395 (@value{GDBP}) print $xmm1
8397 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8398 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8399 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8400 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8401 v4_int32 = @{0, 20657912, 11, 13@},
8402 v2_int64 = @{88725056443645952, 55834574859@},
8403 uint128 = 0x0000000d0000000b013b36f800000000
8408 To set values of such registers, you need to tell @value{GDBN} which
8409 view of the register you wish to change, as if you were assigning
8410 value to a @code{struct} member:
8413 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8416 Normally, register values are relative to the selected stack frame
8417 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8418 value that the register would contain if all stack frames farther in
8419 were exited and their saved registers restored. In order to see the
8420 true contents of hardware registers, you must select the innermost
8421 frame (with @samp{frame 0}).
8423 However, @value{GDBN} must deduce where registers are saved, from the machine
8424 code generated by your compiler. If some registers are not saved, or if
8425 @value{GDBN} is unable to locate the saved registers, the selected stack
8426 frame makes no difference.
8428 @node Floating Point Hardware
8429 @section Floating Point Hardware
8430 @cindex floating point
8432 Depending on the configuration, @value{GDBN} may be able to give
8433 you more information about the status of the floating point hardware.
8438 Display hardware-dependent information about the floating
8439 point unit. The exact contents and layout vary depending on the
8440 floating point chip. Currently, @samp{info float} is supported on
8441 the ARM and x86 machines.
8445 @section Vector Unit
8448 Depending on the configuration, @value{GDBN} may be able to give you
8449 more information about the status of the vector unit.
8454 Display information about the vector unit. The exact contents and
8455 layout vary depending on the hardware.
8458 @node OS Information
8459 @section Operating System Auxiliary Information
8460 @cindex OS information
8462 @value{GDBN} provides interfaces to useful OS facilities that can help
8463 you debug your program.
8465 @cindex @code{ptrace} system call
8466 @cindex @code{struct user} contents
8467 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8468 machines), it interfaces with the inferior via the @code{ptrace}
8469 system call. The operating system creates a special sata structure,
8470 called @code{struct user}, for this interface. You can use the
8471 command @code{info udot} to display the contents of this data
8477 Display the contents of the @code{struct user} maintained by the OS
8478 kernel for the program being debugged. @value{GDBN} displays the
8479 contents of @code{struct user} as a list of hex numbers, similar to
8480 the @code{examine} command.
8483 @cindex auxiliary vector
8484 @cindex vector, auxiliary
8485 Some operating systems supply an @dfn{auxiliary vector} to programs at
8486 startup. This is akin to the arguments and environment that you
8487 specify for a program, but contains a system-dependent variety of
8488 binary values that tell system libraries important details about the
8489 hardware, operating system, and process. Each value's purpose is
8490 identified by an integer tag; the meanings are well-known but system-specific.
8491 Depending on the configuration and operating system facilities,
8492 @value{GDBN} may be able to show you this information. For remote
8493 targets, this functionality may further depend on the remote stub's
8494 support of the @samp{qXfer:auxv:read} packet, see
8495 @ref{qXfer auxiliary vector read}.
8500 Display the auxiliary vector of the inferior, which can be either a
8501 live process or a core dump file. @value{GDBN} prints each tag value
8502 numerically, and also shows names and text descriptions for recognized
8503 tags. Some values in the vector are numbers, some bit masks, and some
8504 pointers to strings or other data. @value{GDBN} displays each value in the
8505 most appropriate form for a recognized tag, and in hexadecimal for
8506 an unrecognized tag.
8509 On some targets, @value{GDBN} can access operating-system-specific information
8510 and display it to user, without interpretation. For remote targets,
8511 this functionality depends on the remote stub's support of the
8512 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8515 @kindex info os processes
8516 @item info os processes
8517 Display the list of processes on the target. For each process,
8518 @value{GDBN} prints the process identifier, the name of the user, and
8519 the command corresponding to the process.
8522 @node Memory Region Attributes
8523 @section Memory Region Attributes
8524 @cindex memory region attributes
8526 @dfn{Memory region attributes} allow you to describe special handling
8527 required by regions of your target's memory. @value{GDBN} uses
8528 attributes to determine whether to allow certain types of memory
8529 accesses; whether to use specific width accesses; and whether to cache
8530 target memory. By default the description of memory regions is
8531 fetched from the target (if the current target supports this), but the
8532 user can override the fetched regions.
8534 Defined memory regions can be individually enabled and disabled. When a
8535 memory region is disabled, @value{GDBN} uses the default attributes when
8536 accessing memory in that region. Similarly, if no memory regions have
8537 been defined, @value{GDBN} uses the default attributes when accessing
8540 When a memory region is defined, it is given a number to identify it;
8541 to enable, disable, or remove a memory region, you specify that number.
8545 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8546 Define a memory region bounded by @var{lower} and @var{upper} with
8547 attributes @var{attributes}@dots{}, and add it to the list of regions
8548 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8549 case: it is treated as the target's maximum memory address.
8550 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8553 Discard any user changes to the memory regions and use target-supplied
8554 regions, if available, or no regions if the target does not support.
8557 @item delete mem @var{nums}@dots{}
8558 Remove memory regions @var{nums}@dots{} from the list of regions
8559 monitored by @value{GDBN}.
8562 @item disable mem @var{nums}@dots{}
8563 Disable monitoring of memory regions @var{nums}@dots{}.
8564 A disabled memory region is not forgotten.
8565 It may be enabled again later.
8568 @item enable mem @var{nums}@dots{}
8569 Enable monitoring of memory regions @var{nums}@dots{}.
8573 Print a table of all defined memory regions, with the following columns
8577 @item Memory Region Number
8578 @item Enabled or Disabled.
8579 Enabled memory regions are marked with @samp{y}.
8580 Disabled memory regions are marked with @samp{n}.
8583 The address defining the inclusive lower bound of the memory region.
8586 The address defining the exclusive upper bound of the memory region.
8589 The list of attributes set for this memory region.
8594 @subsection Attributes
8596 @subsubsection Memory Access Mode
8597 The access mode attributes set whether @value{GDBN} may make read or
8598 write accesses to a memory region.
8600 While these attributes prevent @value{GDBN} from performing invalid
8601 memory accesses, they do nothing to prevent the target system, I/O DMA,
8602 etc.@: from accessing memory.
8606 Memory is read only.
8608 Memory is write only.
8610 Memory is read/write. This is the default.
8613 @subsubsection Memory Access Size
8614 The access size attribute tells @value{GDBN} to use specific sized
8615 accesses in the memory region. Often memory mapped device registers
8616 require specific sized accesses. If no access size attribute is
8617 specified, @value{GDBN} may use accesses of any size.
8621 Use 8 bit memory accesses.
8623 Use 16 bit memory accesses.
8625 Use 32 bit memory accesses.
8627 Use 64 bit memory accesses.
8630 @c @subsubsection Hardware/Software Breakpoints
8631 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8632 @c will use hardware or software breakpoints for the internal breakpoints
8633 @c used by the step, next, finish, until, etc. commands.
8637 @c Always use hardware breakpoints
8638 @c @item swbreak (default)
8641 @subsubsection Data Cache
8642 The data cache attributes set whether @value{GDBN} will cache target
8643 memory. While this generally improves performance by reducing debug
8644 protocol overhead, it can lead to incorrect results because @value{GDBN}
8645 does not know about volatile variables or memory mapped device
8650 Enable @value{GDBN} to cache target memory.
8652 Disable @value{GDBN} from caching target memory. This is the default.
8655 @subsection Memory Access Checking
8656 @value{GDBN} can be instructed to refuse accesses to memory that is
8657 not explicitly described. This can be useful if accessing such
8658 regions has undesired effects for a specific target, or to provide
8659 better error checking. The following commands control this behaviour.
8662 @kindex set mem inaccessible-by-default
8663 @item set mem inaccessible-by-default [on|off]
8664 If @code{on} is specified, make @value{GDBN} treat memory not
8665 explicitly described by the memory ranges as non-existent and refuse accesses
8666 to such memory. The checks are only performed if there's at least one
8667 memory range defined. If @code{off} is specified, make @value{GDBN}
8668 treat the memory not explicitly described by the memory ranges as RAM.
8669 The default value is @code{on}.
8670 @kindex show mem inaccessible-by-default
8671 @item show mem inaccessible-by-default
8672 Show the current handling of accesses to unknown memory.
8676 @c @subsubsection Memory Write Verification
8677 @c The memory write verification attributes set whether @value{GDBN}
8678 @c will re-reads data after each write to verify the write was successful.
8682 @c @item noverify (default)
8685 @node Dump/Restore Files
8686 @section Copy Between Memory and a File
8687 @cindex dump/restore files
8688 @cindex append data to a file
8689 @cindex dump data to a file
8690 @cindex restore data from a file
8692 You can use the commands @code{dump}, @code{append}, and
8693 @code{restore} to copy data between target memory and a file. The
8694 @code{dump} and @code{append} commands write data to a file, and the
8695 @code{restore} command reads data from a file back into the inferior's
8696 memory. Files may be in binary, Motorola S-record, Intel hex, or
8697 Tektronix Hex format; however, @value{GDBN} can only append to binary
8703 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8704 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8705 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8706 or the value of @var{expr}, to @var{filename} in the given format.
8708 The @var{format} parameter may be any one of:
8715 Motorola S-record format.
8717 Tektronix Hex format.
8720 @value{GDBN} uses the same definitions of these formats as the
8721 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8722 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8726 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8727 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8728 Append the contents of memory from @var{start_addr} to @var{end_addr},
8729 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8730 (@value{GDBN} can only append data to files in raw binary form.)
8733 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8734 Restore the contents of file @var{filename} into memory. The
8735 @code{restore} command can automatically recognize any known @sc{bfd}
8736 file format, except for raw binary. To restore a raw binary file you
8737 must specify the optional keyword @code{binary} after the filename.
8739 If @var{bias} is non-zero, its value will be added to the addresses
8740 contained in the file. Binary files always start at address zero, so
8741 they will be restored at address @var{bias}. Other bfd files have
8742 a built-in location; they will be restored at offset @var{bias}
8745 If @var{start} and/or @var{end} are non-zero, then only data between
8746 file offset @var{start} and file offset @var{end} will be restored.
8747 These offsets are relative to the addresses in the file, before
8748 the @var{bias} argument is applied.
8752 @node Core File Generation
8753 @section How to Produce a Core File from Your Program
8754 @cindex dump core from inferior
8756 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8757 image of a running process and its process status (register values
8758 etc.). Its primary use is post-mortem debugging of a program that
8759 crashed while it ran outside a debugger. A program that crashes
8760 automatically produces a core file, unless this feature is disabled by
8761 the user. @xref{Files}, for information on invoking @value{GDBN} in
8762 the post-mortem debugging mode.
8764 Occasionally, you may wish to produce a core file of the program you
8765 are debugging in order to preserve a snapshot of its state.
8766 @value{GDBN} has a special command for that.
8770 @kindex generate-core-file
8771 @item generate-core-file [@var{file}]
8772 @itemx gcore [@var{file}]
8773 Produce a core dump of the inferior process. The optional argument
8774 @var{file} specifies the file name where to put the core dump. If not
8775 specified, the file name defaults to @file{core.@var{pid}}, where
8776 @var{pid} is the inferior process ID.
8778 Note that this command is implemented only for some systems (as of
8779 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8782 @node Character Sets
8783 @section Character Sets
8784 @cindex character sets
8786 @cindex translating between character sets
8787 @cindex host character set
8788 @cindex target character set
8790 If the program you are debugging uses a different character set to
8791 represent characters and strings than the one @value{GDBN} uses itself,
8792 @value{GDBN} can automatically translate between the character sets for
8793 you. The character set @value{GDBN} uses we call the @dfn{host
8794 character set}; the one the inferior program uses we call the
8795 @dfn{target character set}.
8797 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8798 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8799 remote protocol (@pxref{Remote Debugging}) to debug a program
8800 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8801 then the host character set is Latin-1, and the target character set is
8802 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8803 target-charset EBCDIC-US}, then @value{GDBN} translates between
8804 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8805 character and string literals in expressions.
8807 @value{GDBN} has no way to automatically recognize which character set
8808 the inferior program uses; you must tell it, using the @code{set
8809 target-charset} command, described below.
8811 Here are the commands for controlling @value{GDBN}'s character set
8815 @item set target-charset @var{charset}
8816 @kindex set target-charset
8817 Set the current target character set to @var{charset}. To display the
8818 list of supported target character sets, type
8819 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8821 @item set host-charset @var{charset}
8822 @kindex set host-charset
8823 Set the current host character set to @var{charset}.
8825 By default, @value{GDBN} uses a host character set appropriate to the
8826 system it is running on; you can override that default using the
8827 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8828 automatically determine the appropriate host character set. In this
8829 case, @value{GDBN} uses @samp{UTF-8}.
8831 @value{GDBN} can only use certain character sets as its host character
8832 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8833 @value{GDBN} will list the host character sets it supports.
8835 @item set charset @var{charset}
8837 Set the current host and target character sets to @var{charset}. As
8838 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8839 @value{GDBN} will list the names of the character sets that can be used
8840 for both host and target.
8843 @kindex show charset
8844 Show the names of the current host and target character sets.
8846 @item show host-charset
8847 @kindex show host-charset
8848 Show the name of the current host character set.
8850 @item show target-charset
8851 @kindex show target-charset
8852 Show the name of the current target character set.
8854 @item set target-wide-charset @var{charset}
8855 @kindex set target-wide-charset
8856 Set the current target's wide character set to @var{charset}. This is
8857 the character set used by the target's @code{wchar_t} type. To
8858 display the list of supported wide character sets, type
8859 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8861 @item show target-wide-charset
8862 @kindex show target-wide-charset
8863 Show the name of the current target's wide character set.
8866 Here is an example of @value{GDBN}'s character set support in action.
8867 Assume that the following source code has been placed in the file
8868 @file{charset-test.c}:
8874 = @{72, 101, 108, 108, 111, 44, 32, 119,
8875 111, 114, 108, 100, 33, 10, 0@};
8876 char ibm1047_hello[]
8877 = @{200, 133, 147, 147, 150, 107, 64, 166,
8878 150, 153, 147, 132, 90, 37, 0@};
8882 printf ("Hello, world!\n");
8886 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8887 containing the string @samp{Hello, world!} followed by a newline,
8888 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8890 We compile the program, and invoke the debugger on it:
8893 $ gcc -g charset-test.c -o charset-test
8894 $ gdb -nw charset-test
8895 GNU gdb 2001-12-19-cvs
8896 Copyright 2001 Free Software Foundation, Inc.
8901 We can use the @code{show charset} command to see what character sets
8902 @value{GDBN} is currently using to interpret and display characters and
8906 (@value{GDBP}) show charset
8907 The current host and target character set is `ISO-8859-1'.
8911 For the sake of printing this manual, let's use @sc{ascii} as our
8912 initial character set:
8914 (@value{GDBP}) set charset ASCII
8915 (@value{GDBP}) show charset
8916 The current host and target character set is `ASCII'.
8920 Let's assume that @sc{ascii} is indeed the correct character set for our
8921 host system --- in other words, let's assume that if @value{GDBN} prints
8922 characters using the @sc{ascii} character set, our terminal will display
8923 them properly. Since our current target character set is also
8924 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8927 (@value{GDBP}) print ascii_hello
8928 $1 = 0x401698 "Hello, world!\n"
8929 (@value{GDBP}) print ascii_hello[0]
8934 @value{GDBN} uses the target character set for character and string
8935 literals you use in expressions:
8938 (@value{GDBP}) print '+'
8943 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8946 @value{GDBN} relies on the user to tell it which character set the
8947 target program uses. If we print @code{ibm1047_hello} while our target
8948 character set is still @sc{ascii}, we get jibberish:
8951 (@value{GDBP}) print ibm1047_hello
8952 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8953 (@value{GDBP}) print ibm1047_hello[0]
8958 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8959 @value{GDBN} tells us the character sets it supports:
8962 (@value{GDBP}) set target-charset
8963 ASCII EBCDIC-US IBM1047 ISO-8859-1
8964 (@value{GDBP}) set target-charset
8967 We can select @sc{ibm1047} as our target character set, and examine the
8968 program's strings again. Now the @sc{ascii} string is wrong, but
8969 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8970 target character set, @sc{ibm1047}, to the host character set,
8971 @sc{ascii}, and they display correctly:
8974 (@value{GDBP}) set target-charset IBM1047
8975 (@value{GDBP}) show charset
8976 The current host character set is `ASCII'.
8977 The current target character set is `IBM1047'.
8978 (@value{GDBP}) print ascii_hello
8979 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8980 (@value{GDBP}) print ascii_hello[0]
8982 (@value{GDBP}) print ibm1047_hello
8983 $8 = 0x4016a8 "Hello, world!\n"
8984 (@value{GDBP}) print ibm1047_hello[0]
8989 As above, @value{GDBN} uses the target character set for character and
8990 string literals you use in expressions:
8993 (@value{GDBP}) print '+'
8998 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9001 @node Caching Remote Data
9002 @section Caching Data of Remote Targets
9003 @cindex caching data of remote targets
9005 @value{GDBN} caches data exchanged between the debugger and a
9006 remote target (@pxref{Remote Debugging}). Such caching generally improves
9007 performance, because it reduces the overhead of the remote protocol by
9008 bundling memory reads and writes into large chunks. Unfortunately, simply
9009 caching everything would lead to incorrect results, since @value{GDBN}
9010 does not necessarily know anything about volatile values, memory-mapped I/O
9011 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9012 memory can be changed @emph{while} a gdb command is executing.
9013 Therefore, by default, @value{GDBN} only caches data
9014 known to be on the stack@footnote{In non-stop mode, it is moderately
9015 rare for a running thread to modify the stack of a stopped thread
9016 in a way that would interfere with a backtrace, and caching of
9017 stack reads provides a significant speed up of remote backtraces.}.
9018 Other regions of memory can be explicitly marked as
9019 cacheable; see @pxref{Memory Region Attributes}.
9022 @kindex set remotecache
9023 @item set remotecache on
9024 @itemx set remotecache off
9025 This option no longer does anything; it exists for compatibility
9028 @kindex show remotecache
9029 @item show remotecache
9030 Show the current state of the obsolete remotecache flag.
9032 @kindex set stack-cache
9033 @item set stack-cache on
9034 @itemx set stack-cache off
9035 Enable or disable caching of stack accesses. When @code{ON}, use
9036 caching. By default, this option is @code{ON}.
9038 @kindex show stack-cache
9039 @item show stack-cache
9040 Show the current state of data caching for memory accesses.
9043 @item info dcache @r{[}line@r{]}
9044 Print the information about the data cache performance. The
9045 information displayed includes the dcache width and depth, and for
9046 each cache line, its number, address, and how many times it was
9047 referenced. This command is useful for debugging the data cache
9050 If a line number is specified, the contents of that line will be
9054 @node Searching Memory
9055 @section Search Memory
9056 @cindex searching memory
9058 Memory can be searched for a particular sequence of bytes with the
9059 @code{find} command.
9063 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9064 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9065 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9066 etc. The search begins at address @var{start_addr} and continues for either
9067 @var{len} bytes or through to @var{end_addr} inclusive.
9070 @var{s} and @var{n} are optional parameters.
9071 They may be specified in either order, apart or together.
9074 @item @var{s}, search query size
9075 The size of each search query value.
9081 halfwords (two bytes)
9085 giant words (eight bytes)
9088 All values are interpreted in the current language.
9089 This means, for example, that if the current source language is C/C@t{++}
9090 then searching for the string ``hello'' includes the trailing '\0'.
9092 If the value size is not specified, it is taken from the
9093 value's type in the current language.
9094 This is useful when one wants to specify the search
9095 pattern as a mixture of types.
9096 Note that this means, for example, that in the case of C-like languages
9097 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9098 which is typically four bytes.
9100 @item @var{n}, maximum number of finds
9101 The maximum number of matches to print. The default is to print all finds.
9104 You can use strings as search values. Quote them with double-quotes
9106 The string value is copied into the search pattern byte by byte,
9107 regardless of the endianness of the target and the size specification.
9109 The address of each match found is printed as well as a count of the
9110 number of matches found.
9112 The address of the last value found is stored in convenience variable
9114 A count of the number of matches is stored in @samp{$numfound}.
9116 For example, if stopped at the @code{printf} in this function:
9122 static char hello[] = "hello-hello";
9123 static struct @{ char c; short s; int i; @}
9124 __attribute__ ((packed)) mixed
9125 = @{ 'c', 0x1234, 0x87654321 @};
9126 printf ("%s\n", hello);
9131 you get during debugging:
9134 (gdb) find &hello[0], +sizeof(hello), "hello"
9135 0x804956d <hello.1620+6>
9137 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9138 0x8049567 <hello.1620>
9139 0x804956d <hello.1620+6>
9141 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9142 0x8049567 <hello.1620>
9144 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9145 0x8049560 <mixed.1625>
9147 (gdb) print $numfound
9150 $2 = (void *) 0x8049560
9153 @node Optimized Code
9154 @chapter Debugging Optimized Code
9155 @cindex optimized code, debugging
9156 @cindex debugging optimized code
9158 Almost all compilers support optimization. With optimization
9159 disabled, the compiler generates assembly code that corresponds
9160 directly to your source code, in a simplistic way. As the compiler
9161 applies more powerful optimizations, the generated assembly code
9162 diverges from your original source code. With help from debugging
9163 information generated by the compiler, @value{GDBN} can map from
9164 the running program back to constructs from your original source.
9166 @value{GDBN} is more accurate with optimization disabled. If you
9167 can recompile without optimization, it is easier to follow the
9168 progress of your program during debugging. But, there are many cases
9169 where you may need to debug an optimized version.
9171 When you debug a program compiled with @samp{-g -O}, remember that the
9172 optimizer has rearranged your code; the debugger shows you what is
9173 really there. Do not be too surprised when the execution path does not
9174 exactly match your source file! An extreme example: if you define a
9175 variable, but never use it, @value{GDBN} never sees that
9176 variable---because the compiler optimizes it out of existence.
9178 Some things do not work as well with @samp{-g -O} as with just
9179 @samp{-g}, particularly on machines with instruction scheduling. If in
9180 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9181 please report it to us as a bug (including a test case!).
9182 @xref{Variables}, for more information about debugging optimized code.
9185 * Inline Functions:: How @value{GDBN} presents inlining
9188 @node Inline Functions
9189 @section Inline Functions
9190 @cindex inline functions, debugging
9192 @dfn{Inlining} is an optimization that inserts a copy of the function
9193 body directly at each call site, instead of jumping to a shared
9194 routine. @value{GDBN} displays inlined functions just like
9195 non-inlined functions. They appear in backtraces. You can view their
9196 arguments and local variables, step into them with @code{step}, skip
9197 them with @code{next}, and escape from them with @code{finish}.
9198 You can check whether a function was inlined by using the
9199 @code{info frame} command.
9201 For @value{GDBN} to support inlined functions, the compiler must
9202 record information about inlining in the debug information ---
9203 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9204 other compilers do also. @value{GDBN} only supports inlined functions
9205 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9206 do not emit two required attributes (@samp{DW_AT_call_file} and
9207 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9208 function calls with earlier versions of @value{NGCC}. It instead
9209 displays the arguments and local variables of inlined functions as
9210 local variables in the caller.
9212 The body of an inlined function is directly included at its call site;
9213 unlike a non-inlined function, there are no instructions devoted to
9214 the call. @value{GDBN} still pretends that the call site and the
9215 start of the inlined function are different instructions. Stepping to
9216 the call site shows the call site, and then stepping again shows
9217 the first line of the inlined function, even though no additional
9218 instructions are executed.
9220 This makes source-level debugging much clearer; you can see both the
9221 context of the call and then the effect of the call. Only stepping by
9222 a single instruction using @code{stepi} or @code{nexti} does not do
9223 this; single instruction steps always show the inlined body.
9225 There are some ways that @value{GDBN} does not pretend that inlined
9226 function calls are the same as normal calls:
9230 You cannot set breakpoints on inlined functions. @value{GDBN}
9231 either reports that there is no symbol with that name, or else sets the
9232 breakpoint only on non-inlined copies of the function. This limitation
9233 will be removed in a future version of @value{GDBN}; until then,
9234 set a breakpoint by line number on the first line of the inlined
9238 Setting breakpoints at the call site of an inlined function may not
9239 work, because the call site does not contain any code. @value{GDBN}
9240 may incorrectly move the breakpoint to the next line of the enclosing
9241 function, after the call. This limitation will be removed in a future
9242 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9243 or inside the inlined function instead.
9246 @value{GDBN} cannot locate the return value of inlined calls after
9247 using the @code{finish} command. This is a limitation of compiler-generated
9248 debugging information; after @code{finish}, you can step to the next line
9249 and print a variable where your program stored the return value.
9255 @chapter C Preprocessor Macros
9257 Some languages, such as C and C@t{++}, provide a way to define and invoke
9258 ``preprocessor macros'' which expand into strings of tokens.
9259 @value{GDBN} can evaluate expressions containing macro invocations, show
9260 the result of macro expansion, and show a macro's definition, including
9261 where it was defined.
9263 You may need to compile your program specially to provide @value{GDBN}
9264 with information about preprocessor macros. Most compilers do not
9265 include macros in their debugging information, even when you compile
9266 with the @option{-g} flag. @xref{Compilation}.
9268 A program may define a macro at one point, remove that definition later,
9269 and then provide a different definition after that. Thus, at different
9270 points in the program, a macro may have different definitions, or have
9271 no definition at all. If there is a current stack frame, @value{GDBN}
9272 uses the macros in scope at that frame's source code line. Otherwise,
9273 @value{GDBN} uses the macros in scope at the current listing location;
9276 Whenever @value{GDBN} evaluates an expression, it always expands any
9277 macro invocations present in the expression. @value{GDBN} also provides
9278 the following commands for working with macros explicitly.
9282 @kindex macro expand
9283 @cindex macro expansion, showing the results of preprocessor
9284 @cindex preprocessor macro expansion, showing the results of
9285 @cindex expanding preprocessor macros
9286 @item macro expand @var{expression}
9287 @itemx macro exp @var{expression}
9288 Show the results of expanding all preprocessor macro invocations in
9289 @var{expression}. Since @value{GDBN} simply expands macros, but does
9290 not parse the result, @var{expression} need not be a valid expression;
9291 it can be any string of tokens.
9294 @item macro expand-once @var{expression}
9295 @itemx macro exp1 @var{expression}
9296 @cindex expand macro once
9297 @i{(This command is not yet implemented.)} Show the results of
9298 expanding those preprocessor macro invocations that appear explicitly in
9299 @var{expression}. Macro invocations appearing in that expansion are
9300 left unchanged. This command allows you to see the effect of a
9301 particular macro more clearly, without being confused by further
9302 expansions. Since @value{GDBN} simply expands macros, but does not
9303 parse the result, @var{expression} need not be a valid expression; it
9304 can be any string of tokens.
9307 @cindex macro definition, showing
9308 @cindex definition, showing a macro's
9309 @item info macro @var{macro}
9310 Show the definition of the macro named @var{macro}, and describe the
9311 source location or compiler command-line where that definition was established.
9313 @kindex macro define
9314 @cindex user-defined macros
9315 @cindex defining macros interactively
9316 @cindex macros, user-defined
9317 @item macro define @var{macro} @var{replacement-list}
9318 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9319 Introduce a definition for a preprocessor macro named @var{macro},
9320 invocations of which are replaced by the tokens given in
9321 @var{replacement-list}. The first form of this command defines an
9322 ``object-like'' macro, which takes no arguments; the second form
9323 defines a ``function-like'' macro, which takes the arguments given in
9326 A definition introduced by this command is in scope in every
9327 expression evaluated in @value{GDBN}, until it is removed with the
9328 @code{macro undef} command, described below. The definition overrides
9329 all definitions for @var{macro} present in the program being debugged,
9330 as well as any previous user-supplied definition.
9333 @item macro undef @var{macro}
9334 Remove any user-supplied definition for the macro named @var{macro}.
9335 This command only affects definitions provided with the @code{macro
9336 define} command, described above; it cannot remove definitions present
9337 in the program being debugged.
9341 List all the macros defined using the @code{macro define} command.
9344 @cindex macros, example of debugging with
9345 Here is a transcript showing the above commands in action. First, we
9346 show our source files:
9354 #define ADD(x) (M + x)
9359 printf ("Hello, world!\n");
9361 printf ("We're so creative.\n");
9363 printf ("Goodbye, world!\n");
9370 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9371 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9372 compiler includes information about preprocessor macros in the debugging
9376 $ gcc -gdwarf-2 -g3 sample.c -o sample
9380 Now, we start @value{GDBN} on our sample program:
9384 GNU gdb 2002-05-06-cvs
9385 Copyright 2002 Free Software Foundation, Inc.
9386 GDB is free software, @dots{}
9390 We can expand macros and examine their definitions, even when the
9391 program is not running. @value{GDBN} uses the current listing position
9392 to decide which macro definitions are in scope:
9395 (@value{GDBP}) list main
9398 5 #define ADD(x) (M + x)
9403 10 printf ("Hello, world!\n");
9405 12 printf ("We're so creative.\n");
9406 (@value{GDBP}) info macro ADD
9407 Defined at /home/jimb/gdb/macros/play/sample.c:5
9408 #define ADD(x) (M + x)
9409 (@value{GDBP}) info macro Q
9410 Defined at /home/jimb/gdb/macros/play/sample.h:1
9411 included at /home/jimb/gdb/macros/play/sample.c:2
9413 (@value{GDBP}) macro expand ADD(1)
9414 expands to: (42 + 1)
9415 (@value{GDBP}) macro expand-once ADD(1)
9416 expands to: once (M + 1)
9420 In the example above, note that @code{macro expand-once} expands only
9421 the macro invocation explicit in the original text --- the invocation of
9422 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9423 which was introduced by @code{ADD}.
9425 Once the program is running, @value{GDBN} uses the macro definitions in
9426 force at the source line of the current stack frame:
9429 (@value{GDBP}) break main
9430 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9432 Starting program: /home/jimb/gdb/macros/play/sample
9434 Breakpoint 1, main () at sample.c:10
9435 10 printf ("Hello, world!\n");
9439 At line 10, the definition of the macro @code{N} at line 9 is in force:
9442 (@value{GDBP}) info macro N
9443 Defined at /home/jimb/gdb/macros/play/sample.c:9
9445 (@value{GDBP}) macro expand N Q M
9447 (@value{GDBP}) print N Q M
9452 As we step over directives that remove @code{N}'s definition, and then
9453 give it a new definition, @value{GDBN} finds the definition (or lack
9454 thereof) in force at each point:
9459 12 printf ("We're so creative.\n");
9460 (@value{GDBP}) info macro N
9461 The symbol `N' has no definition as a C/C++ preprocessor macro
9462 at /home/jimb/gdb/macros/play/sample.c:12
9465 14 printf ("Goodbye, world!\n");
9466 (@value{GDBP}) info macro N
9467 Defined at /home/jimb/gdb/macros/play/sample.c:13
9469 (@value{GDBP}) macro expand N Q M
9470 expands to: 1729 < 42
9471 (@value{GDBP}) print N Q M
9476 In addition to source files, macros can be defined on the compilation command
9477 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9478 such a way, @value{GDBN} displays the location of their definition as line zero
9479 of the source file submitted to the compiler.
9482 (@value{GDBP}) info macro __STDC__
9483 Defined at /home/jimb/gdb/macros/play/sample.c:0
9490 @chapter Tracepoints
9491 @c This chapter is based on the documentation written by Michael
9492 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9495 In some applications, it is not feasible for the debugger to interrupt
9496 the program's execution long enough for the developer to learn
9497 anything helpful about its behavior. If the program's correctness
9498 depends on its real-time behavior, delays introduced by a debugger
9499 might cause the program to change its behavior drastically, or perhaps
9500 fail, even when the code itself is correct. It is useful to be able
9501 to observe the program's behavior without interrupting it.
9503 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9504 specify locations in the program, called @dfn{tracepoints}, and
9505 arbitrary expressions to evaluate when those tracepoints are reached.
9506 Later, using the @code{tfind} command, you can examine the values
9507 those expressions had when the program hit the tracepoints. The
9508 expressions may also denote objects in memory---structures or arrays,
9509 for example---whose values @value{GDBN} should record; while visiting
9510 a particular tracepoint, you may inspect those objects as if they were
9511 in memory at that moment. However, because @value{GDBN} records these
9512 values without interacting with you, it can do so quickly and
9513 unobtrusively, hopefully not disturbing the program's behavior.
9515 The tracepoint facility is currently available only for remote
9516 targets. @xref{Targets}. In addition, your remote target must know
9517 how to collect trace data. This functionality is implemented in the
9518 remote stub; however, none of the stubs distributed with @value{GDBN}
9519 support tracepoints as of this writing. The format of the remote
9520 packets used to implement tracepoints are described in @ref{Tracepoint
9523 It is also possible to get trace data from a file, in a manner reminiscent
9524 of corefiles; you specify the filename, and use @code{tfind} to search
9525 through the file. @xref{Trace Files}, for more details.
9527 This chapter describes the tracepoint commands and features.
9531 * Analyze Collected Data::
9532 * Tracepoint Variables::
9536 @node Set Tracepoints
9537 @section Commands to Set Tracepoints
9539 Before running such a @dfn{trace experiment}, an arbitrary number of
9540 tracepoints can be set. A tracepoint is actually a special type of
9541 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9542 standard breakpoint commands. For instance, as with breakpoints,
9543 tracepoint numbers are successive integers starting from one, and many
9544 of the commands associated with tracepoints take the tracepoint number
9545 as their argument, to identify which tracepoint to work on.
9547 For each tracepoint, you can specify, in advance, some arbitrary set
9548 of data that you want the target to collect in the trace buffer when
9549 it hits that tracepoint. The collected data can include registers,
9550 local variables, or global data. Later, you can use @value{GDBN}
9551 commands to examine the values these data had at the time the
9554 Tracepoints do not support every breakpoint feature. Ignore counts on
9555 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9556 commands when they are hit. Tracepoints may not be thread-specific
9559 @cindex fast tracepoints
9560 Some targets may support @dfn{fast tracepoints}, which are inserted in
9561 a different way (such as with a jump instead of a trap), that is
9562 faster but possibly restricted in where they may be installed.
9564 @code{gdbserver} supports tracepoints on some target systems.
9565 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9567 This section describes commands to set tracepoints and associated
9568 conditions and actions.
9571 * Create and Delete Tracepoints::
9572 * Enable and Disable Tracepoints::
9573 * Tracepoint Passcounts::
9574 * Tracepoint Conditions::
9575 * Trace State Variables::
9576 * Tracepoint Actions::
9577 * Listing Tracepoints::
9578 * Starting and Stopping Trace Experiments::
9579 * Tracepoint Restrictions::
9582 @node Create and Delete Tracepoints
9583 @subsection Create and Delete Tracepoints
9586 @cindex set tracepoint
9588 @item trace @var{location}
9589 The @code{trace} command is very similar to the @code{break} command.
9590 Its argument @var{location} can be a source line, a function name, or
9591 an address in the target program. @xref{Specify Location}. The
9592 @code{trace} command defines a tracepoint, which is a point in the
9593 target program where the debugger will briefly stop, collect some
9594 data, and then allow the program to continue. Setting a tracepoint or
9595 changing its actions doesn't take effect until the next @code{tstart}
9596 command, and once a trace experiment is running, further changes will
9597 not have any effect until the next trace experiment starts.
9599 Here are some examples of using the @code{trace} command:
9602 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9604 (@value{GDBP}) @b{trace +2} // 2 lines forward
9606 (@value{GDBP}) @b{trace my_function} // first source line of function
9608 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9610 (@value{GDBP}) @b{trace *0x2117c4} // an address
9614 You can abbreviate @code{trace} as @code{tr}.
9616 @item trace @var{location} if @var{cond}
9617 Set a tracepoint with condition @var{cond}; evaluate the expression
9618 @var{cond} each time the tracepoint is reached, and collect data only
9619 if the value is nonzero---that is, if @var{cond} evaluates as true.
9620 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9621 information on tracepoint conditions.
9623 @item ftrace @var{location} [ if @var{cond} ]
9624 @cindex set fast tracepoint
9626 The @code{ftrace} command sets a fast tracepoint. For targets that
9627 support them, fast tracepoints will use a more efficient but possibly
9628 less general technique to trigger data collection, such as a jump
9629 instruction instead of a trap, or some sort of hardware support. It
9630 may not be possible to create a fast tracepoint at the desired
9631 location, in which case the command will exit with an explanatory
9634 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9638 @cindex last tracepoint number
9639 @cindex recent tracepoint number
9640 @cindex tracepoint number
9641 The convenience variable @code{$tpnum} records the tracepoint number
9642 of the most recently set tracepoint.
9644 @kindex delete tracepoint
9645 @cindex tracepoint deletion
9646 @item delete tracepoint @r{[}@var{num}@r{]}
9647 Permanently delete one or more tracepoints. With no argument, the
9648 default is to delete all tracepoints. Note that the regular
9649 @code{delete} command can remove tracepoints also.
9654 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9656 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9660 You can abbreviate this command as @code{del tr}.
9663 @node Enable and Disable Tracepoints
9664 @subsection Enable and Disable Tracepoints
9666 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9669 @kindex disable tracepoint
9670 @item disable tracepoint @r{[}@var{num}@r{]}
9671 Disable tracepoint @var{num}, or all tracepoints if no argument
9672 @var{num} is given. A disabled tracepoint will have no effect during
9673 the next trace experiment, but it is not forgotten. You can re-enable
9674 a disabled tracepoint using the @code{enable tracepoint} command.
9676 @kindex enable tracepoint
9677 @item enable tracepoint @r{[}@var{num}@r{]}
9678 Enable tracepoint @var{num}, or all tracepoints. The enabled
9679 tracepoints will become effective the next time a trace experiment is
9683 @node Tracepoint Passcounts
9684 @subsection Tracepoint Passcounts
9688 @cindex tracepoint pass count
9689 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9690 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9691 automatically stop a trace experiment. If a tracepoint's passcount is
9692 @var{n}, then the trace experiment will be automatically stopped on
9693 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9694 @var{num} is not specified, the @code{passcount} command sets the
9695 passcount of the most recently defined tracepoint. If no passcount is
9696 given, the trace experiment will run until stopped explicitly by the
9702 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9703 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9705 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9706 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9707 (@value{GDBP}) @b{trace foo}
9708 (@value{GDBP}) @b{pass 3}
9709 (@value{GDBP}) @b{trace bar}
9710 (@value{GDBP}) @b{pass 2}
9711 (@value{GDBP}) @b{trace baz}
9712 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9713 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9714 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9715 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9719 @node Tracepoint Conditions
9720 @subsection Tracepoint Conditions
9721 @cindex conditional tracepoints
9722 @cindex tracepoint conditions
9724 The simplest sort of tracepoint collects data every time your program
9725 reaches a specified place. You can also specify a @dfn{condition} for
9726 a tracepoint. A condition is just a Boolean expression in your
9727 programming language (@pxref{Expressions, ,Expressions}). A
9728 tracepoint with a condition evaluates the expression each time your
9729 program reaches it, and data collection happens only if the condition
9732 Tracepoint conditions can be specified when a tracepoint is set, by
9733 using @samp{if} in the arguments to the @code{trace} command.
9734 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9735 also be set or changed at any time with the @code{condition} command,
9736 just as with breakpoints.
9738 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9739 the conditional expression itself. Instead, @value{GDBN} encodes the
9740 expression into an agent expression (@pxref{Agent Expressions}
9741 suitable for execution on the target, independently of @value{GDBN}.
9742 Global variables become raw memory locations, locals become stack
9743 accesses, and so forth.
9745 For instance, suppose you have a function that is usually called
9746 frequently, but should not be called after an error has occurred. You
9747 could use the following tracepoint command to collect data about calls
9748 of that function that happen while the error code is propagating
9749 through the program; an unconditional tracepoint could end up
9750 collecting thousands of useless trace frames that you would have to
9754 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9757 @node Trace State Variables
9758 @subsection Trace State Variables
9759 @cindex trace state variables
9761 A @dfn{trace state variable} is a special type of variable that is
9762 created and managed by target-side code. The syntax is the same as
9763 that for GDB's convenience variables (a string prefixed with ``$''),
9764 but they are stored on the target. They must be created explicitly,
9765 using a @code{tvariable} command. They are always 64-bit signed
9768 Trace state variables are remembered by @value{GDBN}, and downloaded
9769 to the target along with tracepoint information when the trace
9770 experiment starts. There are no intrinsic limits on the number of
9771 trace state variables, beyond memory limitations of the target.
9773 @cindex convenience variables, and trace state variables
9774 Although trace state variables are managed by the target, you can use
9775 them in print commands and expressions as if they were convenience
9776 variables; @value{GDBN} will get the current value from the target
9777 while the trace experiment is running. Trace state variables share
9778 the same namespace as other ``$'' variables, which means that you
9779 cannot have trace state variables with names like @code{$23} or
9780 @code{$pc}, nor can you have a trace state variable and a convenience
9781 variable with the same name.
9785 @item tvariable $@var{name} [ = @var{expression} ]
9787 The @code{tvariable} command creates a new trace state variable named
9788 @code{$@var{name}}, and optionally gives it an initial value of
9789 @var{expression}. @var{expression} is evaluated when this command is
9790 entered; the result will be converted to an integer if possible,
9791 otherwise @value{GDBN} will report an error. A subsequent
9792 @code{tvariable} command specifying the same name does not create a
9793 variable, but instead assigns the supplied initial value to the
9794 existing variable of that name, overwriting any previous initial
9795 value. The default initial value is 0.
9797 @item info tvariables
9798 @kindex info tvariables
9799 List all the trace state variables along with their initial values.
9800 Their current values may also be displayed, if the trace experiment is
9803 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9804 @kindex delete tvariable
9805 Delete the given trace state variables, or all of them if no arguments
9810 @node Tracepoint Actions
9811 @subsection Tracepoint Action Lists
9815 @cindex tracepoint actions
9816 @item actions @r{[}@var{num}@r{]}
9817 This command will prompt for a list of actions to be taken when the
9818 tracepoint is hit. If the tracepoint number @var{num} is not
9819 specified, this command sets the actions for the one that was most
9820 recently defined (so that you can define a tracepoint and then say
9821 @code{actions} without bothering about its number). You specify the
9822 actions themselves on the following lines, one action at a time, and
9823 terminate the actions list with a line containing just @code{end}. So
9824 far, the only defined actions are @code{collect}, @code{teval}, and
9825 @code{while-stepping}.
9827 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9828 Commands, ,Breakpoint Command Lists}), except that only the defined
9829 actions are allowed; any other @value{GDBN} command is rejected.
9831 @cindex remove actions from a tracepoint
9832 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9833 and follow it immediately with @samp{end}.
9836 (@value{GDBP}) @b{collect @var{data}} // collect some data
9838 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9840 (@value{GDBP}) @b{end} // signals the end of actions.
9843 In the following example, the action list begins with @code{collect}
9844 commands indicating the things to be collected when the tracepoint is
9845 hit. Then, in order to single-step and collect additional data
9846 following the tracepoint, a @code{while-stepping} command is used,
9847 followed by the list of things to be collected after each step in a
9848 sequence of single steps. The @code{while-stepping} command is
9849 terminated by its own separate @code{end} command. Lastly, the action
9850 list is terminated by an @code{end} command.
9853 (@value{GDBP}) @b{trace foo}
9854 (@value{GDBP}) @b{actions}
9855 Enter actions for tracepoint 1, one per line:
9859 > collect $pc, arr[i]
9864 @kindex collect @r{(tracepoints)}
9865 @item collect @var{expr1}, @var{expr2}, @dots{}
9866 Collect values of the given expressions when the tracepoint is hit.
9867 This command accepts a comma-separated list of any valid expressions.
9868 In addition to global, static, or local variables, the following
9869 special arguments are supported:
9873 collect all registers
9876 collect all function arguments
9879 collect all local variables.
9882 You can give several consecutive @code{collect} commands, each one
9883 with a single argument, or one @code{collect} command with several
9884 arguments separated by commas; the effect is the same.
9886 The command @code{info scope} (@pxref{Symbols, info scope}) is
9887 particularly useful for figuring out what data to collect.
9889 @kindex teval @r{(tracepoints)}
9890 @item teval @var{expr1}, @var{expr2}, @dots{}
9891 Evaluate the given expressions when the tracepoint is hit. This
9892 command accepts a comma-separated list of expressions. The results
9893 are discarded, so this is mainly useful for assigning values to trace
9894 state variables (@pxref{Trace State Variables}) without adding those
9895 values to the trace buffer, as would be the case if the @code{collect}
9898 @kindex while-stepping @r{(tracepoints)}
9899 @item while-stepping @var{n}
9900 Perform @var{n} single-step instruction traces after the tracepoint,
9901 collecting new data after each step. The @code{while-stepping}
9902 command is followed by the list of what to collect while stepping
9903 (followed by its own @code{end} command):
9907 > collect $regs, myglobal
9913 Note that @code{$pc} is not automatically collected by
9914 @code{while-stepping}; you need to explicitly collect that register if
9915 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9918 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9919 @kindex set default-collect
9920 @cindex default collection action
9921 This variable is a list of expressions to collect at each tracepoint
9922 hit. It is effectively an additional @code{collect} action prepended
9923 to every tracepoint action list. The expressions are parsed
9924 individually for each tracepoint, so for instance a variable named
9925 @code{xyz} may be interpreted as a global for one tracepoint, and a
9926 local for another, as appropriate to the tracepoint's location.
9928 @item show default-collect
9929 @kindex show default-collect
9930 Show the list of expressions that are collected by default at each
9935 @node Listing Tracepoints
9936 @subsection Listing Tracepoints
9939 @kindex info tracepoints
9941 @cindex information about tracepoints
9942 @item info tracepoints @r{[}@var{num}@r{]}
9943 Display information about the tracepoint @var{num}. If you don't
9944 specify a tracepoint number, displays information about all the
9945 tracepoints defined so far. The format is similar to that used for
9946 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9947 command, simply restricting itself to tracepoints.
9949 A tracepoint's listing may include additional information specific to
9954 its passcount as given by the @code{passcount @var{n}} command
9958 (@value{GDBP}) @b{info trace}
9959 Num Type Disp Enb Address What
9960 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9962 collect globfoo, $regs
9971 This command can be abbreviated @code{info tp}.
9974 @node Starting and Stopping Trace Experiments
9975 @subsection Starting and Stopping Trace Experiments
9979 @cindex start a new trace experiment
9980 @cindex collected data discarded
9982 This command takes no arguments. It starts the trace experiment, and
9983 begins collecting data. This has the side effect of discarding all
9984 the data collected in the trace buffer during the previous trace
9988 @cindex stop a running trace experiment
9990 This command takes no arguments. It ends the trace experiment, and
9991 stops collecting data.
9993 @strong{Note}: a trace experiment and data collection may stop
9994 automatically if any tracepoint's passcount is reached
9995 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9998 @cindex status of trace data collection
9999 @cindex trace experiment, status of
10001 This command displays the status of the current trace data
10005 Here is an example of the commands we described so far:
10008 (@value{GDBP}) @b{trace gdb_c_test}
10009 (@value{GDBP}) @b{actions}
10010 Enter actions for tracepoint #1, one per line.
10011 > collect $regs,$locals,$args
10012 > while-stepping 11
10016 (@value{GDBP}) @b{tstart}
10017 [time passes @dots{}]
10018 (@value{GDBP}) @b{tstop}
10021 @cindex disconnected tracing
10022 You can choose to continue running the trace experiment even if
10023 @value{GDBN} disconnects from the target, voluntarily or
10024 involuntarily. For commands such as @code{detach}, the debugger will
10025 ask what you want to do with the trace. But for unexpected
10026 terminations (@value{GDBN} crash, network outage), it would be
10027 unfortunate to lose hard-won trace data, so the variable
10028 @code{disconnected-tracing} lets you decide whether the trace should
10029 continue running without @value{GDBN}.
10032 @item set disconnected-tracing on
10033 @itemx set disconnected-tracing off
10034 @kindex set disconnected-tracing
10035 Choose whether a tracing run should continue to run if @value{GDBN}
10036 has disconnected from the target. Note that @code{detach} or
10037 @code{quit} will ask you directly what to do about a running trace no
10038 matter what this variable's setting, so the variable is mainly useful
10039 for handling unexpected situations, such as loss of the network.
10041 @item show disconnected-tracing
10042 @kindex show disconnected-tracing
10043 Show the current choice for disconnected tracing.
10047 When you reconnect to the target, the trace experiment may or may not
10048 still be running; it might have filled the trace buffer in the
10049 meantime, or stopped for one of the other reasons. If it is running,
10050 it will continue after reconnection.
10052 Upon reconnection, the target will upload information about the
10053 tracepoints in effect. @value{GDBN} will then compare that
10054 information to the set of tracepoints currently defined, and attempt
10055 to match them up, allowing for the possibility that the numbers may
10056 have changed due to creation and deletion in the meantime. If one of
10057 the target's tracepoints does not match any in @value{GDBN}, the
10058 debugger will create a new tracepoint, so that you have a number with
10059 which to specify that tracepoint. This matching-up process is
10060 necessarily heuristic, and it may result in useless tracepoints being
10061 created; you may simply delete them if they are of no use.
10063 @cindex circular trace buffer
10064 If your target agent supports a @dfn{circular trace buffer}, then you
10065 can run a trace experiment indefinitely without filling the trace
10066 buffer; when space runs out, the agent deletes already-collected trace
10067 frames, oldest first, until there is enough room to continue
10068 collecting. This is especially useful if your tracepoints are being
10069 hit too often, and your trace gets terminated prematurely because the
10070 buffer is full. To ask for a circular trace buffer, simply set
10071 @samp{circular_trace_buffer} to on. You can set this at any time,
10072 including during tracing; if the agent can do it, it will change
10073 buffer handling on the fly, otherwise it will not take effect until
10077 @item set circular-trace-buffer on
10078 @itemx set circular-trace-buffer off
10079 @kindex set circular-trace-buffer
10080 Choose whether a tracing run should use a linear or circular buffer
10081 for trace data. A linear buffer will not lose any trace data, but may
10082 fill up prematurely, while a circular buffer will discard old trace
10083 data, but it will have always room for the latest tracepoint hits.
10085 @item show circular-trace-buffer
10086 @kindex show circular-trace-buffer
10087 Show the current choice for the trace buffer. Note that this may not
10088 match the agent's current buffer handling, nor is it guaranteed to
10089 match the setting that might have been in effect during a past run,
10090 for instance if you are looking at frames from a trace file.
10094 @node Tracepoint Restrictions
10095 @subsection Tracepoint Restrictions
10097 @cindex tracepoint restrictions
10098 There are a number of restrictions on the use of tracepoints. As
10099 described above, tracepoint data gathering occurs on the target
10100 without interaction from @value{GDBN}. Thus the full capabilities of
10101 the debugger are not available during data gathering, and then at data
10102 examination time, you will be limited by only having what was
10103 collected. The following items describe some common problems, but it
10104 is not exhaustive, and you may run into additional difficulties not
10110 Tracepoint expressions are intended to gather objects (lvalues). Thus
10111 the full flexibility of GDB's expression evaluator is not available.
10112 You cannot call functions, cast objects to aggregate types, access
10113 convenience variables or modify values (except by assignment to trace
10114 state variables). Some language features may implicitly call
10115 functions (for instance Objective-C fields with accessors), and therefore
10116 cannot be collected either.
10119 Collection of local variables, either individually or in bulk with
10120 @code{$locals} or @code{$args}, during @code{while-stepping} may
10121 behave erratically. The stepping action may enter a new scope (for
10122 instance by stepping into a function), or the location of the variable
10123 may change (for instance it is loaded into a register). The
10124 tracepoint data recorded uses the location information for the
10125 variables that is correct for the tracepoint location. When the
10126 tracepoint is created, it is not possible, in general, to determine
10127 where the steps of a @code{while-stepping} sequence will advance the
10128 program---particularly if a conditional branch is stepped.
10131 Collection of an incompletely-initialized or partially-destroyed object
10132 may result in something that @value{GDBN} cannot display, or displays
10133 in a misleading way.
10136 When @value{GDBN} displays a pointer to character it automatically
10137 dereferences the pointer to also display characters of the string
10138 being pointed to. However, collecting the pointer during tracing does
10139 not automatically collect the string. You need to explicitly
10140 dereference the pointer and provide size information if you want to
10141 collect not only the pointer, but the memory pointed to. For example,
10142 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10146 It is not possible to collect a complete stack backtrace at a
10147 tracepoint. Instead, you may collect the registers and a few hundred
10148 bytes from the stack pointer with something like @code{*$esp@@300}
10149 (adjust to use the name of the actual stack pointer register on your
10150 target architecture, and the amount of stack you wish to capture).
10151 Then the @code{backtrace} command will show a partial backtrace when
10152 using a trace frame. The number of stack frames that can be examined
10153 depends on the sizes of the frames in the collected stack. Note that
10154 if you ask for a block so large that it goes past the bottom of the
10155 stack, the target agent may report an error trying to read from an
10159 If you do not collect registers at a tracepoint, @value{GDBN} can
10160 infer that the value of @code{$pc} must be the same as the address of
10161 the tracepoint and use that when you are looking at a trace frame
10162 for that tracepoint. However, this cannot work if the tracepoint has
10163 multiple locations (for instance if it was set in a function that was
10164 inlined), or if it has a @code{while-stepping} loop. In those cases
10165 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10170 @node Analyze Collected Data
10171 @section Using the Collected Data
10173 After the tracepoint experiment ends, you use @value{GDBN} commands
10174 for examining the trace data. The basic idea is that each tracepoint
10175 collects a trace @dfn{snapshot} every time it is hit and another
10176 snapshot every time it single-steps. All these snapshots are
10177 consecutively numbered from zero and go into a buffer, and you can
10178 examine them later. The way you examine them is to @dfn{focus} on a
10179 specific trace snapshot. When the remote stub is focused on a trace
10180 snapshot, it will respond to all @value{GDBN} requests for memory and
10181 registers by reading from the buffer which belongs to that snapshot,
10182 rather than from @emph{real} memory or registers of the program being
10183 debugged. This means that @strong{all} @value{GDBN} commands
10184 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10185 behave as if we were currently debugging the program state as it was
10186 when the tracepoint occurred. Any requests for data that are not in
10187 the buffer will fail.
10190 * tfind:: How to select a trace snapshot
10191 * tdump:: How to display all data for a snapshot
10192 * save tracepoints:: How to save tracepoints for a future run
10196 @subsection @code{tfind @var{n}}
10199 @cindex select trace snapshot
10200 @cindex find trace snapshot
10201 The basic command for selecting a trace snapshot from the buffer is
10202 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10203 counting from zero. If no argument @var{n} is given, the next
10204 snapshot is selected.
10206 Here are the various forms of using the @code{tfind} command.
10210 Find the first snapshot in the buffer. This is a synonym for
10211 @code{tfind 0} (since 0 is the number of the first snapshot).
10214 Stop debugging trace snapshots, resume @emph{live} debugging.
10217 Same as @samp{tfind none}.
10220 No argument means find the next trace snapshot.
10223 Find the previous trace snapshot before the current one. This permits
10224 retracing earlier steps.
10226 @item tfind tracepoint @var{num}
10227 Find the next snapshot associated with tracepoint @var{num}. Search
10228 proceeds forward from the last examined trace snapshot. If no
10229 argument @var{num} is given, it means find the next snapshot collected
10230 for the same tracepoint as the current snapshot.
10232 @item tfind pc @var{addr}
10233 Find the next snapshot associated with the value @var{addr} of the
10234 program counter. Search proceeds forward from the last examined trace
10235 snapshot. If no argument @var{addr} is given, it means find the next
10236 snapshot with the same value of PC as the current snapshot.
10238 @item tfind outside @var{addr1}, @var{addr2}
10239 Find the next snapshot whose PC is outside the given range of
10240 addresses (exclusive).
10242 @item tfind range @var{addr1}, @var{addr2}
10243 Find the next snapshot whose PC is between @var{addr1} and
10244 @var{addr2} (inclusive).
10246 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10247 Find the next snapshot associated with the source line @var{n}. If
10248 the optional argument @var{file} is given, refer to line @var{n} in
10249 that source file. Search proceeds forward from the last examined
10250 trace snapshot. If no argument @var{n} is given, it means find the
10251 next line other than the one currently being examined; thus saying
10252 @code{tfind line} repeatedly can appear to have the same effect as
10253 stepping from line to line in a @emph{live} debugging session.
10256 The default arguments for the @code{tfind} commands are specifically
10257 designed to make it easy to scan through the trace buffer. For
10258 instance, @code{tfind} with no argument selects the next trace
10259 snapshot, and @code{tfind -} with no argument selects the previous
10260 trace snapshot. So, by giving one @code{tfind} command, and then
10261 simply hitting @key{RET} repeatedly you can examine all the trace
10262 snapshots in order. Or, by saying @code{tfind -} and then hitting
10263 @key{RET} repeatedly you can examine the snapshots in reverse order.
10264 The @code{tfind line} command with no argument selects the snapshot
10265 for the next source line executed. The @code{tfind pc} command with
10266 no argument selects the next snapshot with the same program counter
10267 (PC) as the current frame. The @code{tfind tracepoint} command with
10268 no argument selects the next trace snapshot collected by the same
10269 tracepoint as the current one.
10271 In addition to letting you scan through the trace buffer manually,
10272 these commands make it easy to construct @value{GDBN} scripts that
10273 scan through the trace buffer and print out whatever collected data
10274 you are interested in. Thus, if we want to examine the PC, FP, and SP
10275 registers from each trace frame in the buffer, we can say this:
10278 (@value{GDBP}) @b{tfind start}
10279 (@value{GDBP}) @b{while ($trace_frame != -1)}
10280 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10281 $trace_frame, $pc, $sp, $fp
10285 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10286 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10287 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10288 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10289 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10290 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10291 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10292 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10293 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10294 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10295 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10298 Or, if we want to examine the variable @code{X} at each source line in
10302 (@value{GDBP}) @b{tfind start}
10303 (@value{GDBP}) @b{while ($trace_frame != -1)}
10304 > printf "Frame %d, X == %d\n", $trace_frame, X
10314 @subsection @code{tdump}
10316 @cindex dump all data collected at tracepoint
10317 @cindex tracepoint data, display
10319 This command takes no arguments. It prints all the data collected at
10320 the current trace snapshot.
10323 (@value{GDBP}) @b{trace 444}
10324 (@value{GDBP}) @b{actions}
10325 Enter actions for tracepoint #2, one per line:
10326 > collect $regs, $locals, $args, gdb_long_test
10329 (@value{GDBP}) @b{tstart}
10331 (@value{GDBP}) @b{tfind line 444}
10332 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10334 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10336 (@value{GDBP}) @b{tdump}
10337 Data collected at tracepoint 2, trace frame 1:
10338 d0 0xc4aa0085 -995491707
10342 d4 0x71aea3d 119204413
10345 d7 0x380035 3670069
10346 a0 0x19e24a 1696330
10347 a1 0x3000668 50333288
10349 a3 0x322000 3284992
10350 a4 0x3000698 50333336
10351 a5 0x1ad3cc 1758156
10352 fp 0x30bf3c 0x30bf3c
10353 sp 0x30bf34 0x30bf34
10355 pc 0x20b2c8 0x20b2c8
10359 p = 0x20e5b4 "gdb-test"
10366 gdb_long_test = 17 '\021'
10371 @code{tdump} works by scanning the tracepoint's current collection
10372 actions and printing the value of each expression listed. So
10373 @code{tdump} can fail, if after a run, you change the tracepoint's
10374 actions to mention variables that were not collected during the run.
10376 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10377 uses the collected value of @code{$pc} to distinguish between trace
10378 frames that were collected at the tracepoint hit, and frames that were
10379 collected while stepping. This allows it to correctly choose whether
10380 to display the basic list of collections, or the collections from the
10381 body of the while-stepping loop. However, if @code{$pc} was not collected,
10382 then @code{tdump} will always attempt to dump using the basic collection
10383 list, and may fail if a while-stepping frame does not include all the
10384 same data that is collected at the tracepoint hit.
10385 @c This is getting pretty arcane, example would be good.
10387 @node save tracepoints
10388 @subsection @code{save tracepoints @var{filename}}
10389 @kindex save tracepoints
10390 @kindex save-tracepoints
10391 @cindex save tracepoints for future sessions
10393 This command saves all current tracepoint definitions together with
10394 their actions and passcounts, into a file @file{@var{filename}}
10395 suitable for use in a later debugging session. To read the saved
10396 tracepoint definitions, use the @code{source} command (@pxref{Command
10397 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10398 alias for @w{@code{save tracepoints}}
10400 @node Tracepoint Variables
10401 @section Convenience Variables for Tracepoints
10402 @cindex tracepoint variables
10403 @cindex convenience variables for tracepoints
10406 @vindex $trace_frame
10407 @item (int) $trace_frame
10408 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10409 snapshot is selected.
10411 @vindex $tracepoint
10412 @item (int) $tracepoint
10413 The tracepoint for the current trace snapshot.
10415 @vindex $trace_line
10416 @item (int) $trace_line
10417 The line number for the current trace snapshot.
10419 @vindex $trace_file
10420 @item (char []) $trace_file
10421 The source file for the current trace snapshot.
10423 @vindex $trace_func
10424 @item (char []) $trace_func
10425 The name of the function containing @code{$tracepoint}.
10428 Note: @code{$trace_file} is not suitable for use in @code{printf},
10429 use @code{output} instead.
10431 Here's a simple example of using these convenience variables for
10432 stepping through all the trace snapshots and printing some of their
10433 data. Note that these are not the same as trace state variables,
10434 which are managed by the target.
10437 (@value{GDBP}) @b{tfind start}
10439 (@value{GDBP}) @b{while $trace_frame != -1}
10440 > output $trace_file
10441 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10447 @section Using Trace Files
10448 @cindex trace files
10450 In some situations, the target running a trace experiment may no
10451 longer be available; perhaps it crashed, or the hardware was needed
10452 for a different activity. To handle these cases, you can arrange to
10453 dump the trace data into a file, and later use that file as a source
10454 of trace data, via the @code{target tfile} command.
10459 @item tsave [ -r ] @var{filename}
10460 Save the trace data to @var{filename}. By default, this command
10461 assumes that @var{filename} refers to the host filesystem, so if
10462 necessary @value{GDBN} will copy raw trace data up from the target and
10463 then save it. If the target supports it, you can also supply the
10464 optional argument @code{-r} (``remote'') to direct the target to save
10465 the data directly into @var{filename} in its own filesystem, which may be
10466 more efficient if the trace buffer is very large. (Note, however, that
10467 @code{target tfile} can only read from files accessible to the host.)
10469 @kindex target tfile
10471 @item target tfile @var{filename}
10472 Use the file named @var{filename} as a source of trace data. Commands
10473 that examine data work as they do with a live target, but it is not
10474 possible to run any new trace experiments. @code{tstatus} will report
10475 the state of the trace run at the moment the data was saved, as well
10476 as the current trace frame you are examining. @var{filename} must be
10477 on a filesystem accessible to the host.
10482 @chapter Debugging Programs That Use Overlays
10485 If your program is too large to fit completely in your target system's
10486 memory, you can sometimes use @dfn{overlays} to work around this
10487 problem. @value{GDBN} provides some support for debugging programs that
10491 * How Overlays Work:: A general explanation of overlays.
10492 * Overlay Commands:: Managing overlays in @value{GDBN}.
10493 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10494 mapped by asking the inferior.
10495 * Overlay Sample Program:: A sample program using overlays.
10498 @node How Overlays Work
10499 @section How Overlays Work
10500 @cindex mapped overlays
10501 @cindex unmapped overlays
10502 @cindex load address, overlay's
10503 @cindex mapped address
10504 @cindex overlay area
10506 Suppose you have a computer whose instruction address space is only 64
10507 kilobytes long, but which has much more memory which can be accessed by
10508 other means: special instructions, segment registers, or memory
10509 management hardware, for example. Suppose further that you want to
10510 adapt a program which is larger than 64 kilobytes to run on this system.
10512 One solution is to identify modules of your program which are relatively
10513 independent, and need not call each other directly; call these modules
10514 @dfn{overlays}. Separate the overlays from the main program, and place
10515 their machine code in the larger memory. Place your main program in
10516 instruction memory, but leave at least enough space there to hold the
10517 largest overlay as well.
10519 Now, to call a function located in an overlay, you must first copy that
10520 overlay's machine code from the large memory into the space set aside
10521 for it in the instruction memory, and then jump to its entry point
10524 @c NB: In the below the mapped area's size is greater or equal to the
10525 @c size of all overlays. This is intentional to remind the developer
10526 @c that overlays don't necessarily need to be the same size.
10530 Data Instruction Larger
10531 Address Space Address Space Address Space
10532 +-----------+ +-----------+ +-----------+
10534 +-----------+ +-----------+ +-----------+<-- overlay 1
10535 | program | | main | .----| overlay 1 | load address
10536 | variables | | program | | +-----------+
10537 | and heap | | | | | |
10538 +-----------+ | | | +-----------+<-- overlay 2
10539 | | +-----------+ | | | load address
10540 +-----------+ | | | .-| overlay 2 |
10542 mapped --->+-----------+ | | +-----------+
10543 address | | | | | |
10544 | overlay | <-' | | |
10545 | area | <---' +-----------+<-- overlay 3
10546 | | <---. | | load address
10547 +-----------+ `--| overlay 3 |
10554 @anchor{A code overlay}A code overlay
10558 The diagram (@pxref{A code overlay}) shows a system with separate data
10559 and instruction address spaces. To map an overlay, the program copies
10560 its code from the larger address space to the instruction address space.
10561 Since the overlays shown here all use the same mapped address, only one
10562 may be mapped at a time. For a system with a single address space for
10563 data and instructions, the diagram would be similar, except that the
10564 program variables and heap would share an address space with the main
10565 program and the overlay area.
10567 An overlay loaded into instruction memory and ready for use is called a
10568 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10569 instruction memory. An overlay not present (or only partially present)
10570 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10571 is its address in the larger memory. The mapped address is also called
10572 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10573 called the @dfn{load memory address}, or @dfn{LMA}.
10575 Unfortunately, overlays are not a completely transparent way to adapt a
10576 program to limited instruction memory. They introduce a new set of
10577 global constraints you must keep in mind as you design your program:
10582 Before calling or returning to a function in an overlay, your program
10583 must make sure that overlay is actually mapped. Otherwise, the call or
10584 return will transfer control to the right address, but in the wrong
10585 overlay, and your program will probably crash.
10588 If the process of mapping an overlay is expensive on your system, you
10589 will need to choose your overlays carefully to minimize their effect on
10590 your program's performance.
10593 The executable file you load onto your system must contain each
10594 overlay's instructions, appearing at the overlay's load address, not its
10595 mapped address. However, each overlay's instructions must be relocated
10596 and its symbols defined as if the overlay were at its mapped address.
10597 You can use GNU linker scripts to specify different load and relocation
10598 addresses for pieces of your program; see @ref{Overlay Description,,,
10599 ld.info, Using ld: the GNU linker}.
10602 The procedure for loading executable files onto your system must be able
10603 to load their contents into the larger address space as well as the
10604 instruction and data spaces.
10608 The overlay system described above is rather simple, and could be
10609 improved in many ways:
10614 If your system has suitable bank switch registers or memory management
10615 hardware, you could use those facilities to make an overlay's load area
10616 contents simply appear at their mapped address in instruction space.
10617 This would probably be faster than copying the overlay to its mapped
10618 area in the usual way.
10621 If your overlays are small enough, you could set aside more than one
10622 overlay area, and have more than one overlay mapped at a time.
10625 You can use overlays to manage data, as well as instructions. In
10626 general, data overlays are even less transparent to your design than
10627 code overlays: whereas code overlays only require care when you call or
10628 return to functions, data overlays require care every time you access
10629 the data. Also, if you change the contents of a data overlay, you
10630 must copy its contents back out to its load address before you can copy a
10631 different data overlay into the same mapped area.
10636 @node Overlay Commands
10637 @section Overlay Commands
10639 To use @value{GDBN}'s overlay support, each overlay in your program must
10640 correspond to a separate section of the executable file. The section's
10641 virtual memory address and load memory address must be the overlay's
10642 mapped and load addresses. Identifying overlays with sections allows
10643 @value{GDBN} to determine the appropriate address of a function or
10644 variable, depending on whether the overlay is mapped or not.
10646 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10647 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10652 Disable @value{GDBN}'s overlay support. When overlay support is
10653 disabled, @value{GDBN} assumes that all functions and variables are
10654 always present at their mapped addresses. By default, @value{GDBN}'s
10655 overlay support is disabled.
10657 @item overlay manual
10658 @cindex manual overlay debugging
10659 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10660 relies on you to tell it which overlays are mapped, and which are not,
10661 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10662 commands described below.
10664 @item overlay map-overlay @var{overlay}
10665 @itemx overlay map @var{overlay}
10666 @cindex map an overlay
10667 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10668 be the name of the object file section containing the overlay. When an
10669 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10670 functions and variables at their mapped addresses. @value{GDBN} assumes
10671 that any other overlays whose mapped ranges overlap that of
10672 @var{overlay} are now unmapped.
10674 @item overlay unmap-overlay @var{overlay}
10675 @itemx overlay unmap @var{overlay}
10676 @cindex unmap an overlay
10677 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10678 must be the name of the object file section containing the overlay.
10679 When an overlay is unmapped, @value{GDBN} assumes it can find the
10680 overlay's functions and variables at their load addresses.
10683 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10684 consults a data structure the overlay manager maintains in the inferior
10685 to see which overlays are mapped. For details, see @ref{Automatic
10686 Overlay Debugging}.
10688 @item overlay load-target
10689 @itemx overlay load
10690 @cindex reloading the overlay table
10691 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10692 re-reads the table @value{GDBN} automatically each time the inferior
10693 stops, so this command should only be necessary if you have changed the
10694 overlay mapping yourself using @value{GDBN}. This command is only
10695 useful when using automatic overlay debugging.
10697 @item overlay list-overlays
10698 @itemx overlay list
10699 @cindex listing mapped overlays
10700 Display a list of the overlays currently mapped, along with their mapped
10701 addresses, load addresses, and sizes.
10705 Normally, when @value{GDBN} prints a code address, it includes the name
10706 of the function the address falls in:
10709 (@value{GDBP}) print main
10710 $3 = @{int ()@} 0x11a0 <main>
10713 When overlay debugging is enabled, @value{GDBN} recognizes code in
10714 unmapped overlays, and prints the names of unmapped functions with
10715 asterisks around them. For example, if @code{foo} is a function in an
10716 unmapped overlay, @value{GDBN} prints it this way:
10719 (@value{GDBP}) overlay list
10720 No sections are mapped.
10721 (@value{GDBP}) print foo
10722 $5 = @{int (int)@} 0x100000 <*foo*>
10725 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10729 (@value{GDBP}) overlay list
10730 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10731 mapped at 0x1016 - 0x104a
10732 (@value{GDBP}) print foo
10733 $6 = @{int (int)@} 0x1016 <foo>
10736 When overlay debugging is enabled, @value{GDBN} can find the correct
10737 address for functions and variables in an overlay, whether or not the
10738 overlay is mapped. This allows most @value{GDBN} commands, like
10739 @code{break} and @code{disassemble}, to work normally, even on unmapped
10740 code. However, @value{GDBN}'s breakpoint support has some limitations:
10744 @cindex breakpoints in overlays
10745 @cindex overlays, setting breakpoints in
10746 You can set breakpoints in functions in unmapped overlays, as long as
10747 @value{GDBN} can write to the overlay at its load address.
10749 @value{GDBN} can not set hardware or simulator-based breakpoints in
10750 unmapped overlays. However, if you set a breakpoint at the end of your
10751 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10752 you are using manual overlay management), @value{GDBN} will re-set its
10753 breakpoints properly.
10757 @node Automatic Overlay Debugging
10758 @section Automatic Overlay Debugging
10759 @cindex automatic overlay debugging
10761 @value{GDBN} can automatically track which overlays are mapped and which
10762 are not, given some simple co-operation from the overlay manager in the
10763 inferior. If you enable automatic overlay debugging with the
10764 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10765 looks in the inferior's memory for certain variables describing the
10766 current state of the overlays.
10768 Here are the variables your overlay manager must define to support
10769 @value{GDBN}'s automatic overlay debugging:
10773 @item @code{_ovly_table}:
10774 This variable must be an array of the following structures:
10779 /* The overlay's mapped address. */
10782 /* The size of the overlay, in bytes. */
10783 unsigned long size;
10785 /* The overlay's load address. */
10788 /* Non-zero if the overlay is currently mapped;
10790 unsigned long mapped;
10794 @item @code{_novlys}:
10795 This variable must be a four-byte signed integer, holding the total
10796 number of elements in @code{_ovly_table}.
10800 To decide whether a particular overlay is mapped or not, @value{GDBN}
10801 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10802 @code{lma} members equal the VMA and LMA of the overlay's section in the
10803 executable file. When @value{GDBN} finds a matching entry, it consults
10804 the entry's @code{mapped} member to determine whether the overlay is
10807 In addition, your overlay manager may define a function called
10808 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10809 will silently set a breakpoint there. If the overlay manager then
10810 calls this function whenever it has changed the overlay table, this
10811 will enable @value{GDBN} to accurately keep track of which overlays
10812 are in program memory, and update any breakpoints that may be set
10813 in overlays. This will allow breakpoints to work even if the
10814 overlays are kept in ROM or other non-writable memory while they
10815 are not being executed.
10817 @node Overlay Sample Program
10818 @section Overlay Sample Program
10819 @cindex overlay example program
10821 When linking a program which uses overlays, you must place the overlays
10822 at their load addresses, while relocating them to run at their mapped
10823 addresses. To do this, you must write a linker script (@pxref{Overlay
10824 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10825 since linker scripts are specific to a particular host system, target
10826 architecture, and target memory layout, this manual cannot provide
10827 portable sample code demonstrating @value{GDBN}'s overlay support.
10829 However, the @value{GDBN} source distribution does contain an overlaid
10830 program, with linker scripts for a few systems, as part of its test
10831 suite. The program consists of the following files from
10832 @file{gdb/testsuite/gdb.base}:
10836 The main program file.
10838 A simple overlay manager, used by @file{overlays.c}.
10843 Overlay modules, loaded and used by @file{overlays.c}.
10846 Linker scripts for linking the test program on the @code{d10v-elf}
10847 and @code{m32r-elf} targets.
10850 You can build the test program using the @code{d10v-elf} GCC
10851 cross-compiler like this:
10854 $ d10v-elf-gcc -g -c overlays.c
10855 $ d10v-elf-gcc -g -c ovlymgr.c
10856 $ d10v-elf-gcc -g -c foo.c
10857 $ d10v-elf-gcc -g -c bar.c
10858 $ d10v-elf-gcc -g -c baz.c
10859 $ d10v-elf-gcc -g -c grbx.c
10860 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10861 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10864 The build process is identical for any other architecture, except that
10865 you must substitute the appropriate compiler and linker script for the
10866 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10870 @chapter Using @value{GDBN} with Different Languages
10873 Although programming languages generally have common aspects, they are
10874 rarely expressed in the same manner. For instance, in ANSI C,
10875 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10876 Modula-2, it is accomplished by @code{p^}. Values can also be
10877 represented (and displayed) differently. Hex numbers in C appear as
10878 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10880 @cindex working language
10881 Language-specific information is built into @value{GDBN} for some languages,
10882 allowing you to express operations like the above in your program's
10883 native language, and allowing @value{GDBN} to output values in a manner
10884 consistent with the syntax of your program's native language. The
10885 language you use to build expressions is called the @dfn{working
10889 * Setting:: Switching between source languages
10890 * Show:: Displaying the language
10891 * Checks:: Type and range checks
10892 * Supported Languages:: Supported languages
10893 * Unsupported Languages:: Unsupported languages
10897 @section Switching Between Source Languages
10899 There are two ways to control the working language---either have @value{GDBN}
10900 set it automatically, or select it manually yourself. You can use the
10901 @code{set language} command for either purpose. On startup, @value{GDBN}
10902 defaults to setting the language automatically. The working language is
10903 used to determine how expressions you type are interpreted, how values
10906 In addition to the working language, every source file that
10907 @value{GDBN} knows about has its own working language. For some object
10908 file formats, the compiler might indicate which language a particular
10909 source file is in. However, most of the time @value{GDBN} infers the
10910 language from the name of the file. The language of a source file
10911 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10912 show each frame appropriately for its own language. There is no way to
10913 set the language of a source file from within @value{GDBN}, but you can
10914 set the language associated with a filename extension. @xref{Show, ,
10915 Displaying the Language}.
10917 This is most commonly a problem when you use a program, such
10918 as @code{cfront} or @code{f2c}, that generates C but is written in
10919 another language. In that case, make the
10920 program use @code{#line} directives in its C output; that way
10921 @value{GDBN} will know the correct language of the source code of the original
10922 program, and will display that source code, not the generated C code.
10925 * Filenames:: Filename extensions and languages.
10926 * Manually:: Setting the working language manually
10927 * Automatically:: Having @value{GDBN} infer the source language
10931 @subsection List of Filename Extensions and Languages
10933 If a source file name ends in one of the following extensions, then
10934 @value{GDBN} infers that its language is the one indicated.
10952 C@t{++} source file
10958 Objective-C source file
10962 Fortran source file
10965 Modula-2 source file
10969 Assembler source file. This actually behaves almost like C, but
10970 @value{GDBN} does not skip over function prologues when stepping.
10973 In addition, you may set the language associated with a filename
10974 extension. @xref{Show, , Displaying the Language}.
10977 @subsection Setting the Working Language
10979 If you allow @value{GDBN} to set the language automatically,
10980 expressions are interpreted the same way in your debugging session and
10983 @kindex set language
10984 If you wish, you may set the language manually. To do this, issue the
10985 command @samp{set language @var{lang}}, where @var{lang} is the name of
10986 a language, such as
10987 @code{c} or @code{modula-2}.
10988 For a list of the supported languages, type @samp{set language}.
10990 Setting the language manually prevents @value{GDBN} from updating the working
10991 language automatically. This can lead to confusion if you try
10992 to debug a program when the working language is not the same as the
10993 source language, when an expression is acceptable to both
10994 languages---but means different things. For instance, if the current
10995 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11003 might not have the effect you intended. In C, this means to add
11004 @code{b} and @code{c} and place the result in @code{a}. The result
11005 printed would be the value of @code{a}. In Modula-2, this means to compare
11006 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11008 @node Automatically
11009 @subsection Having @value{GDBN} Infer the Source Language
11011 To have @value{GDBN} set the working language automatically, use
11012 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11013 then infers the working language. That is, when your program stops in a
11014 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11015 working language to the language recorded for the function in that
11016 frame. If the language for a frame is unknown (that is, if the function
11017 or block corresponding to the frame was defined in a source file that
11018 does not have a recognized extension), the current working language is
11019 not changed, and @value{GDBN} issues a warning.
11021 This may not seem necessary for most programs, which are written
11022 entirely in one source language. However, program modules and libraries
11023 written in one source language can be used by a main program written in
11024 a different source language. Using @samp{set language auto} in this
11025 case frees you from having to set the working language manually.
11028 @section Displaying the Language
11030 The following commands help you find out which language is the
11031 working language, and also what language source files were written in.
11034 @item show language
11035 @kindex show language
11036 Display the current working language. This is the
11037 language you can use with commands such as @code{print} to
11038 build and compute expressions that may involve variables in your program.
11041 @kindex info frame@r{, show the source language}
11042 Display the source language for this frame. This language becomes the
11043 working language if you use an identifier from this frame.
11044 @xref{Frame Info, ,Information about a Frame}, to identify the other
11045 information listed here.
11048 @kindex info source@r{, show the source language}
11049 Display the source language of this source file.
11050 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11051 information listed here.
11054 In unusual circumstances, you may have source files with extensions
11055 not in the standard list. You can then set the extension associated
11056 with a language explicitly:
11059 @item set extension-language @var{ext} @var{language}
11060 @kindex set extension-language
11061 Tell @value{GDBN} that source files with extension @var{ext} are to be
11062 assumed as written in the source language @var{language}.
11064 @item info extensions
11065 @kindex info extensions
11066 List all the filename extensions and the associated languages.
11070 @section Type and Range Checking
11073 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11074 checking are included, but they do not yet have any effect. This
11075 section documents the intended facilities.
11077 @c FIXME remove warning when type/range code added
11079 Some languages are designed to guard you against making seemingly common
11080 errors through a series of compile- and run-time checks. These include
11081 checking the type of arguments to functions and operators, and making
11082 sure mathematical overflows are caught at run time. Checks such as
11083 these help to ensure a program's correctness once it has been compiled
11084 by eliminating type mismatches, and providing active checks for range
11085 errors when your program is running.
11087 @value{GDBN} can check for conditions like the above if you wish.
11088 Although @value{GDBN} does not check the statements in your program,
11089 it can check expressions entered directly into @value{GDBN} for
11090 evaluation via the @code{print} command, for example. As with the
11091 working language, @value{GDBN} can also decide whether or not to check
11092 automatically based on your program's source language.
11093 @xref{Supported Languages, ,Supported Languages}, for the default
11094 settings of supported languages.
11097 * Type Checking:: An overview of type checking
11098 * Range Checking:: An overview of range checking
11101 @cindex type checking
11102 @cindex checks, type
11103 @node Type Checking
11104 @subsection An Overview of Type Checking
11106 Some languages, such as Modula-2, are strongly typed, meaning that the
11107 arguments to operators and functions have to be of the correct type,
11108 otherwise an error occurs. These checks prevent type mismatch
11109 errors from ever causing any run-time problems. For example,
11117 The second example fails because the @code{CARDINAL} 1 is not
11118 type-compatible with the @code{REAL} 2.3.
11120 For the expressions you use in @value{GDBN} commands, you can tell the
11121 @value{GDBN} type checker to skip checking;
11122 to treat any mismatches as errors and abandon the expression;
11123 or to only issue warnings when type mismatches occur,
11124 but evaluate the expression anyway. When you choose the last of
11125 these, @value{GDBN} evaluates expressions like the second example above, but
11126 also issues a warning.
11128 Even if you turn type checking off, there may be other reasons
11129 related to type that prevent @value{GDBN} from evaluating an expression.
11130 For instance, @value{GDBN} does not know how to add an @code{int} and
11131 a @code{struct foo}. These particular type errors have nothing to do
11132 with the language in use, and usually arise from expressions, such as
11133 the one described above, which make little sense to evaluate anyway.
11135 Each language defines to what degree it is strict about type. For
11136 instance, both Modula-2 and C require the arguments to arithmetical
11137 operators to be numbers. In C, enumerated types and pointers can be
11138 represented as numbers, so that they are valid arguments to mathematical
11139 operators. @xref{Supported Languages, ,Supported Languages}, for further
11140 details on specific languages.
11142 @value{GDBN} provides some additional commands for controlling the type checker:
11144 @kindex set check type
11145 @kindex show check type
11147 @item set check type auto
11148 Set type checking on or off based on the current working language.
11149 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11152 @item set check type on
11153 @itemx set check type off
11154 Set type checking on or off, overriding the default setting for the
11155 current working language. Issue a warning if the setting does not
11156 match the language default. If any type mismatches occur in
11157 evaluating an expression while type checking is on, @value{GDBN} prints a
11158 message and aborts evaluation of the expression.
11160 @item set check type warn
11161 Cause the type checker to issue warnings, but to always attempt to
11162 evaluate the expression. Evaluating the expression may still
11163 be impossible for other reasons. For example, @value{GDBN} cannot add
11164 numbers and structures.
11167 Show the current setting of the type checker, and whether or not @value{GDBN}
11168 is setting it automatically.
11171 @cindex range checking
11172 @cindex checks, range
11173 @node Range Checking
11174 @subsection An Overview of Range Checking
11176 In some languages (such as Modula-2), it is an error to exceed the
11177 bounds of a type; this is enforced with run-time checks. Such range
11178 checking is meant to ensure program correctness by making sure
11179 computations do not overflow, or indices on an array element access do
11180 not exceed the bounds of the array.
11182 For expressions you use in @value{GDBN} commands, you can tell
11183 @value{GDBN} to treat range errors in one of three ways: ignore them,
11184 always treat them as errors and abandon the expression, or issue
11185 warnings but evaluate the expression anyway.
11187 A range error can result from numerical overflow, from exceeding an
11188 array index bound, or when you type a constant that is not a member
11189 of any type. Some languages, however, do not treat overflows as an
11190 error. In many implementations of C, mathematical overflow causes the
11191 result to ``wrap around'' to lower values---for example, if @var{m} is
11192 the largest integer value, and @var{s} is the smallest, then
11195 @var{m} + 1 @result{} @var{s}
11198 This, too, is specific to individual languages, and in some cases
11199 specific to individual compilers or machines. @xref{Supported Languages, ,
11200 Supported Languages}, for further details on specific languages.
11202 @value{GDBN} provides some additional commands for controlling the range checker:
11204 @kindex set check range
11205 @kindex show check range
11207 @item set check range auto
11208 Set range checking on or off based on the current working language.
11209 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11212 @item set check range on
11213 @itemx set check range off
11214 Set range checking on or off, overriding the default setting for the
11215 current working language. A warning is issued if the setting does not
11216 match the language default. If a range error occurs and range checking is on,
11217 then a message is printed and evaluation of the expression is aborted.
11219 @item set check range warn
11220 Output messages when the @value{GDBN} range checker detects a range error,
11221 but attempt to evaluate the expression anyway. Evaluating the
11222 expression may still be impossible for other reasons, such as accessing
11223 memory that the process does not own (a typical example from many Unix
11227 Show the current setting of the range checker, and whether or not it is
11228 being set automatically by @value{GDBN}.
11231 @node Supported Languages
11232 @section Supported Languages
11234 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11235 assembly, Modula-2, and Ada.
11236 @c This is false ...
11237 Some @value{GDBN} features may be used in expressions regardless of the
11238 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11239 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11240 ,Expressions}) can be used with the constructs of any supported
11243 The following sections detail to what degree each source language is
11244 supported by @value{GDBN}. These sections are not meant to be language
11245 tutorials or references, but serve only as a reference guide to what the
11246 @value{GDBN} expression parser accepts, and what input and output
11247 formats should look like for different languages. There are many good
11248 books written on each of these languages; please look to these for a
11249 language reference or tutorial.
11252 * C:: C and C@t{++}
11254 * Objective-C:: Objective-C
11255 * Fortran:: Fortran
11257 * Modula-2:: Modula-2
11262 @subsection C and C@t{++}
11264 @cindex C and C@t{++}
11265 @cindex expressions in C or C@t{++}
11267 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11268 to both languages. Whenever this is the case, we discuss those languages
11272 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11273 @cindex @sc{gnu} C@t{++}
11274 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11275 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11276 effectively, you must compile your C@t{++} programs with a supported
11277 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11278 compiler (@code{aCC}).
11280 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11281 format; if it doesn't work on your system, try the stabs+ debugging
11282 format. You can select those formats explicitly with the @code{g++}
11283 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11284 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11285 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11288 * C Operators:: C and C@t{++} operators
11289 * C Constants:: C and C@t{++} constants
11290 * C Plus Plus Expressions:: C@t{++} expressions
11291 * C Defaults:: Default settings for C and C@t{++}
11292 * C Checks:: C and C@t{++} type and range checks
11293 * Debugging C:: @value{GDBN} and C
11294 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11295 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11299 @subsubsection C and C@t{++} Operators
11301 @cindex C and C@t{++} operators
11303 Operators must be defined on values of specific types. For instance,
11304 @code{+} is defined on numbers, but not on structures. Operators are
11305 often defined on groups of types.
11307 For the purposes of C and C@t{++}, the following definitions hold:
11312 @emph{Integral types} include @code{int} with any of its storage-class
11313 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11316 @emph{Floating-point types} include @code{float}, @code{double}, and
11317 @code{long double} (if supported by the target platform).
11320 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11323 @emph{Scalar types} include all of the above.
11328 The following operators are supported. They are listed here
11329 in order of increasing precedence:
11333 The comma or sequencing operator. Expressions in a comma-separated list
11334 are evaluated from left to right, with the result of the entire
11335 expression being the last expression evaluated.
11338 Assignment. The value of an assignment expression is the value
11339 assigned. Defined on scalar types.
11342 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11343 and translated to @w{@code{@var{a} = @var{a op b}}}.
11344 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11345 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11346 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11349 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11350 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11354 Logical @sc{or}. Defined on integral types.
11357 Logical @sc{and}. Defined on integral types.
11360 Bitwise @sc{or}. Defined on integral types.
11363 Bitwise exclusive-@sc{or}. Defined on integral types.
11366 Bitwise @sc{and}. Defined on integral types.
11369 Equality and inequality. Defined on scalar types. The value of these
11370 expressions is 0 for false and non-zero for true.
11372 @item <@r{, }>@r{, }<=@r{, }>=
11373 Less than, greater than, less than or equal, greater than or equal.
11374 Defined on scalar types. The value of these expressions is 0 for false
11375 and non-zero for true.
11378 left shift, and right shift. Defined on integral types.
11381 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11384 Addition and subtraction. Defined on integral types, floating-point types and
11387 @item *@r{, }/@r{, }%
11388 Multiplication, division, and modulus. Multiplication and division are
11389 defined on integral and floating-point types. Modulus is defined on
11393 Increment and decrement. When appearing before a variable, the
11394 operation is performed before the variable is used in an expression;
11395 when appearing after it, the variable's value is used before the
11396 operation takes place.
11399 Pointer dereferencing. Defined on pointer types. Same precedence as
11403 Address operator. Defined on variables. Same precedence as @code{++}.
11405 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11406 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11407 to examine the address
11408 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11412 Negative. Defined on integral and floating-point types. Same
11413 precedence as @code{++}.
11416 Logical negation. Defined on integral types. Same precedence as
11420 Bitwise complement operator. Defined on integral types. Same precedence as
11425 Structure member, and pointer-to-structure member. For convenience,
11426 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11427 pointer based on the stored type information.
11428 Defined on @code{struct} and @code{union} data.
11431 Dereferences of pointers to members.
11434 Array indexing. @code{@var{a}[@var{i}]} is defined as
11435 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11438 Function parameter list. Same precedence as @code{->}.
11441 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11442 and @code{class} types.
11445 Doubled colons also represent the @value{GDBN} scope operator
11446 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11450 If an operator is redefined in the user code, @value{GDBN} usually
11451 attempts to invoke the redefined version instead of using the operator's
11452 predefined meaning.
11455 @subsubsection C and C@t{++} Constants
11457 @cindex C and C@t{++} constants
11459 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11464 Integer constants are a sequence of digits. Octal constants are
11465 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11466 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11467 @samp{l}, specifying that the constant should be treated as a
11471 Floating point constants are a sequence of digits, followed by a decimal
11472 point, followed by a sequence of digits, and optionally followed by an
11473 exponent. An exponent is of the form:
11474 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11475 sequence of digits. The @samp{+} is optional for positive exponents.
11476 A floating-point constant may also end with a letter @samp{f} or
11477 @samp{F}, specifying that the constant should be treated as being of
11478 the @code{float} (as opposed to the default @code{double}) type; or with
11479 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11483 Enumerated constants consist of enumerated identifiers, or their
11484 integral equivalents.
11487 Character constants are a single character surrounded by single quotes
11488 (@code{'}), or a number---the ordinal value of the corresponding character
11489 (usually its @sc{ascii} value). Within quotes, the single character may
11490 be represented by a letter or by @dfn{escape sequences}, which are of
11491 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11492 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11493 @samp{@var{x}} is a predefined special character---for example,
11494 @samp{\n} for newline.
11497 String constants are a sequence of character constants surrounded by
11498 double quotes (@code{"}). Any valid character constant (as described
11499 above) may appear. Double quotes within the string must be preceded by
11500 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11504 Pointer constants are an integral value. You can also write pointers
11505 to constants using the C operator @samp{&}.
11508 Array constants are comma-separated lists surrounded by braces @samp{@{}
11509 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11510 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11511 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11514 @node C Plus Plus Expressions
11515 @subsubsection C@t{++} Expressions
11517 @cindex expressions in C@t{++}
11518 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11520 @cindex debugging C@t{++} programs
11521 @cindex C@t{++} compilers
11522 @cindex debug formats and C@t{++}
11523 @cindex @value{NGCC} and C@t{++}
11525 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11526 proper compiler and the proper debug format. Currently, @value{GDBN}
11527 works best when debugging C@t{++} code that is compiled with
11528 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11529 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11530 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11531 stabs+ as their default debug format, so you usually don't need to
11532 specify a debug format explicitly. Other compilers and/or debug formats
11533 are likely to work badly or not at all when using @value{GDBN} to debug
11539 @cindex member functions
11541 Member function calls are allowed; you can use expressions like
11544 count = aml->GetOriginal(x, y)
11547 @vindex this@r{, inside C@t{++} member functions}
11548 @cindex namespace in C@t{++}
11550 While a member function is active (in the selected stack frame), your
11551 expressions have the same namespace available as the member function;
11552 that is, @value{GDBN} allows implicit references to the class instance
11553 pointer @code{this} following the same rules as C@t{++}.
11555 @cindex call overloaded functions
11556 @cindex overloaded functions, calling
11557 @cindex type conversions in C@t{++}
11559 You can call overloaded functions; @value{GDBN} resolves the function
11560 call to the right definition, with some restrictions. @value{GDBN} does not
11561 perform overload resolution involving user-defined type conversions,
11562 calls to constructors, or instantiations of templates that do not exist
11563 in the program. It also cannot handle ellipsis argument lists or
11566 It does perform integral conversions and promotions, floating-point
11567 promotions, arithmetic conversions, pointer conversions, conversions of
11568 class objects to base classes, and standard conversions such as those of
11569 functions or arrays to pointers; it requires an exact match on the
11570 number of function arguments.
11572 Overload resolution is always performed, unless you have specified
11573 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11574 ,@value{GDBN} Features for C@t{++}}.
11576 You must specify @code{set overload-resolution off} in order to use an
11577 explicit function signature to call an overloaded function, as in
11579 p 'foo(char,int)'('x', 13)
11582 The @value{GDBN} command-completion facility can simplify this;
11583 see @ref{Completion, ,Command Completion}.
11585 @cindex reference declarations
11587 @value{GDBN} understands variables declared as C@t{++} references; you can use
11588 them in expressions just as you do in C@t{++} source---they are automatically
11591 In the parameter list shown when @value{GDBN} displays a frame, the values of
11592 reference variables are not displayed (unlike other variables); this
11593 avoids clutter, since references are often used for large structures.
11594 The @emph{address} of a reference variable is always shown, unless
11595 you have specified @samp{set print address off}.
11598 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11599 expressions can use it just as expressions in your program do. Since
11600 one scope may be defined in another, you can use @code{::} repeatedly if
11601 necessary, for example in an expression like
11602 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11603 resolving name scope by reference to source files, in both C and C@t{++}
11604 debugging (@pxref{Variables, ,Program Variables}).
11607 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11608 calling virtual functions correctly, printing out virtual bases of
11609 objects, calling functions in a base subobject, casting objects, and
11610 invoking user-defined operators.
11613 @subsubsection C and C@t{++} Defaults
11615 @cindex C and C@t{++} defaults
11617 If you allow @value{GDBN} to set type and range checking automatically, they
11618 both default to @code{off} whenever the working language changes to
11619 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11620 selects the working language.
11622 If you allow @value{GDBN} to set the language automatically, it
11623 recognizes source files whose names end with @file{.c}, @file{.C}, or
11624 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11625 these files, it sets the working language to C or C@t{++}.
11626 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11627 for further details.
11629 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11630 @c unimplemented. If (b) changes, it might make sense to let this node
11631 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11634 @subsubsection C and C@t{++} Type and Range Checks
11636 @cindex C and C@t{++} checks
11638 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11639 is not used. However, if you turn type checking on, @value{GDBN}
11640 considers two variables type equivalent if:
11644 The two variables are structured and have the same structure, union, or
11648 The two variables have the same type name, or types that have been
11649 declared equivalent through @code{typedef}.
11652 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11655 The two @code{struct}, @code{union}, or @code{enum} variables are
11656 declared in the same declaration. (Note: this may not be true for all C
11661 Range checking, if turned on, is done on mathematical operations. Array
11662 indices are not checked, since they are often used to index a pointer
11663 that is not itself an array.
11666 @subsubsection @value{GDBN} and C
11668 The @code{set print union} and @code{show print union} commands apply to
11669 the @code{union} type. When set to @samp{on}, any @code{union} that is
11670 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11671 appears as @samp{@{...@}}.
11673 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11674 with pointers and a memory allocation function. @xref{Expressions,
11677 @node Debugging C Plus Plus
11678 @subsubsection @value{GDBN} Features for C@t{++}
11680 @cindex commands for C@t{++}
11682 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11683 designed specifically for use with C@t{++}. Here is a summary:
11686 @cindex break in overloaded functions
11687 @item @r{breakpoint menus}
11688 When you want a breakpoint in a function whose name is overloaded,
11689 @value{GDBN} has the capability to display a menu of possible breakpoint
11690 locations to help you specify which function definition you want.
11691 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11693 @cindex overloading in C@t{++}
11694 @item rbreak @var{regex}
11695 Setting breakpoints using regular expressions is helpful for setting
11696 breakpoints on overloaded functions that are not members of any special
11698 @xref{Set Breaks, ,Setting Breakpoints}.
11700 @cindex C@t{++} exception handling
11703 Debug C@t{++} exception handling using these commands. @xref{Set
11704 Catchpoints, , Setting Catchpoints}.
11706 @cindex inheritance
11707 @item ptype @var{typename}
11708 Print inheritance relationships as well as other information for type
11710 @xref{Symbols, ,Examining the Symbol Table}.
11712 @cindex C@t{++} symbol display
11713 @item set print demangle
11714 @itemx show print demangle
11715 @itemx set print asm-demangle
11716 @itemx show print asm-demangle
11717 Control whether C@t{++} symbols display in their source form, both when
11718 displaying code as C@t{++} source and when displaying disassemblies.
11719 @xref{Print Settings, ,Print Settings}.
11721 @item set print object
11722 @itemx show print object
11723 Choose whether to print derived (actual) or declared types of objects.
11724 @xref{Print Settings, ,Print Settings}.
11726 @item set print vtbl
11727 @itemx show print vtbl
11728 Control the format for printing virtual function tables.
11729 @xref{Print Settings, ,Print Settings}.
11730 (The @code{vtbl} commands do not work on programs compiled with the HP
11731 ANSI C@t{++} compiler (@code{aCC}).)
11733 @kindex set overload-resolution
11734 @cindex overloaded functions, overload resolution
11735 @item set overload-resolution on
11736 Enable overload resolution for C@t{++} expression evaluation. The default
11737 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11738 and searches for a function whose signature matches the argument types,
11739 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11740 Expressions, ,C@t{++} Expressions}, for details).
11741 If it cannot find a match, it emits a message.
11743 @item set overload-resolution off
11744 Disable overload resolution for C@t{++} expression evaluation. For
11745 overloaded functions that are not class member functions, @value{GDBN}
11746 chooses the first function of the specified name that it finds in the
11747 symbol table, whether or not its arguments are of the correct type. For
11748 overloaded functions that are class member functions, @value{GDBN}
11749 searches for a function whose signature @emph{exactly} matches the
11752 @kindex show overload-resolution
11753 @item show overload-resolution
11754 Show the current setting of overload resolution.
11756 @item @r{Overloaded symbol names}
11757 You can specify a particular definition of an overloaded symbol, using
11758 the same notation that is used to declare such symbols in C@t{++}: type
11759 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11760 also use the @value{GDBN} command-line word completion facilities to list the
11761 available choices, or to finish the type list for you.
11762 @xref{Completion,, Command Completion}, for details on how to do this.
11765 @node Decimal Floating Point
11766 @subsubsection Decimal Floating Point format
11767 @cindex decimal floating point format
11769 @value{GDBN} can examine, set and perform computations with numbers in
11770 decimal floating point format, which in the C language correspond to the
11771 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11772 specified by the extension to support decimal floating-point arithmetic.
11774 There are two encodings in use, depending on the architecture: BID (Binary
11775 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11776 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11779 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11780 to manipulate decimal floating point numbers, it is not possible to convert
11781 (using a cast, for example) integers wider than 32-bit to decimal float.
11783 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11784 point computations, error checking in decimal float operations ignores
11785 underflow, overflow and divide by zero exceptions.
11787 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11788 to inspect @code{_Decimal128} values stored in floating point registers.
11789 See @ref{PowerPC,,PowerPC} for more details.
11795 @value{GDBN} can be used to debug programs written in D and compiled with
11796 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11797 specific feature --- dynamic arrays.
11800 @subsection Objective-C
11802 @cindex Objective-C
11803 This section provides information about some commands and command
11804 options that are useful for debugging Objective-C code. See also
11805 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11806 few more commands specific to Objective-C support.
11809 * Method Names in Commands::
11810 * The Print Command with Objective-C::
11813 @node Method Names in Commands
11814 @subsubsection Method Names in Commands
11816 The following commands have been extended to accept Objective-C method
11817 names as line specifications:
11819 @kindex clear@r{, and Objective-C}
11820 @kindex break@r{, and Objective-C}
11821 @kindex info line@r{, and Objective-C}
11822 @kindex jump@r{, and Objective-C}
11823 @kindex list@r{, and Objective-C}
11827 @item @code{info line}
11832 A fully qualified Objective-C method name is specified as
11835 -[@var{Class} @var{methodName}]
11838 where the minus sign is used to indicate an instance method and a
11839 plus sign (not shown) is used to indicate a class method. The class
11840 name @var{Class} and method name @var{methodName} are enclosed in
11841 brackets, similar to the way messages are specified in Objective-C
11842 source code. For example, to set a breakpoint at the @code{create}
11843 instance method of class @code{Fruit} in the program currently being
11847 break -[Fruit create]
11850 To list ten program lines around the @code{initialize} class method,
11854 list +[NSText initialize]
11857 In the current version of @value{GDBN}, the plus or minus sign is
11858 required. In future versions of @value{GDBN}, the plus or minus
11859 sign will be optional, but you can use it to narrow the search. It
11860 is also possible to specify just a method name:
11866 You must specify the complete method name, including any colons. If
11867 your program's source files contain more than one @code{create} method,
11868 you'll be presented with a numbered list of classes that implement that
11869 method. Indicate your choice by number, or type @samp{0} to exit if
11872 As another example, to clear a breakpoint established at the
11873 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11876 clear -[NSWindow makeKeyAndOrderFront:]
11879 @node The Print Command with Objective-C
11880 @subsubsection The Print Command With Objective-C
11881 @cindex Objective-C, print objects
11882 @kindex print-object
11883 @kindex po @r{(@code{print-object})}
11885 The print command has also been extended to accept methods. For example:
11888 print -[@var{object} hash]
11891 @cindex print an Objective-C object description
11892 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11894 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11895 and print the result. Also, an additional command has been added,
11896 @code{print-object} or @code{po} for short, which is meant to print
11897 the description of an object. However, this command may only work
11898 with certain Objective-C libraries that have a particular hook
11899 function, @code{_NSPrintForDebugger}, defined.
11902 @subsection Fortran
11903 @cindex Fortran-specific support in @value{GDBN}
11905 @value{GDBN} can be used to debug programs written in Fortran, but it
11906 currently supports only the features of Fortran 77 language.
11908 @cindex trailing underscore, in Fortran symbols
11909 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11910 among them) append an underscore to the names of variables and
11911 functions. When you debug programs compiled by those compilers, you
11912 will need to refer to variables and functions with a trailing
11916 * Fortran Operators:: Fortran operators and expressions
11917 * Fortran Defaults:: Default settings for Fortran
11918 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11921 @node Fortran Operators
11922 @subsubsection Fortran Operators and Expressions
11924 @cindex Fortran operators and expressions
11926 Operators must be defined on values of specific types. For instance,
11927 @code{+} is defined on numbers, but not on characters or other non-
11928 arithmetic types. Operators are often defined on groups of types.
11932 The exponentiation operator. It raises the first operand to the power
11936 The range operator. Normally used in the form of array(low:high) to
11937 represent a section of array.
11940 The access component operator. Normally used to access elements in derived
11941 types. Also suitable for unions. As unions aren't part of regular Fortran,
11942 this can only happen when accessing a register that uses a gdbarch-defined
11946 @node Fortran Defaults
11947 @subsubsection Fortran Defaults
11949 @cindex Fortran Defaults
11951 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11952 default uses case-insensitive matches for Fortran symbols. You can
11953 change that with the @samp{set case-insensitive} command, see
11954 @ref{Symbols}, for the details.
11956 @node Special Fortran Commands
11957 @subsubsection Special Fortran Commands
11959 @cindex Special Fortran commands
11961 @value{GDBN} has some commands to support Fortran-specific features,
11962 such as displaying common blocks.
11965 @cindex @code{COMMON} blocks, Fortran
11966 @kindex info common
11967 @item info common @r{[}@var{common-name}@r{]}
11968 This command prints the values contained in the Fortran @code{COMMON}
11969 block whose name is @var{common-name}. With no argument, the names of
11970 all @code{COMMON} blocks visible at the current program location are
11977 @cindex Pascal support in @value{GDBN}, limitations
11978 Debugging Pascal programs which use sets, subranges, file variables, or
11979 nested functions does not currently work. @value{GDBN} does not support
11980 entering expressions, printing values, or similar features using Pascal
11983 The Pascal-specific command @code{set print pascal_static-members}
11984 controls whether static members of Pascal objects are displayed.
11985 @xref{Print Settings, pascal_static-members}.
11988 @subsection Modula-2
11990 @cindex Modula-2, @value{GDBN} support
11992 The extensions made to @value{GDBN} to support Modula-2 only support
11993 output from the @sc{gnu} Modula-2 compiler (which is currently being
11994 developed). Other Modula-2 compilers are not currently supported, and
11995 attempting to debug executables produced by them is most likely
11996 to give an error as @value{GDBN} reads in the executable's symbol
11999 @cindex expressions in Modula-2
12001 * M2 Operators:: Built-in operators
12002 * Built-In Func/Proc:: Built-in functions and procedures
12003 * M2 Constants:: Modula-2 constants
12004 * M2 Types:: Modula-2 types
12005 * M2 Defaults:: Default settings for Modula-2
12006 * Deviations:: Deviations from standard Modula-2
12007 * M2 Checks:: Modula-2 type and range checks
12008 * M2 Scope:: The scope operators @code{::} and @code{.}
12009 * GDB/M2:: @value{GDBN} and Modula-2
12013 @subsubsection Operators
12014 @cindex Modula-2 operators
12016 Operators must be defined on values of specific types. For instance,
12017 @code{+} is defined on numbers, but not on structures. Operators are
12018 often defined on groups of types. For the purposes of Modula-2, the
12019 following definitions hold:
12024 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12028 @emph{Character types} consist of @code{CHAR} and its subranges.
12031 @emph{Floating-point types} consist of @code{REAL}.
12034 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12038 @emph{Scalar types} consist of all of the above.
12041 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12044 @emph{Boolean types} consist of @code{BOOLEAN}.
12048 The following operators are supported, and appear in order of
12049 increasing precedence:
12053 Function argument or array index separator.
12056 Assignment. The value of @var{var} @code{:=} @var{value} is
12060 Less than, greater than on integral, floating-point, or enumerated
12064 Less than or equal to, greater than or equal to
12065 on integral, floating-point and enumerated types, or set inclusion on
12066 set types. Same precedence as @code{<}.
12068 @item =@r{, }<>@r{, }#
12069 Equality and two ways of expressing inequality, valid on scalar types.
12070 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12071 available for inequality, since @code{#} conflicts with the script
12075 Set membership. Defined on set types and the types of their members.
12076 Same precedence as @code{<}.
12079 Boolean disjunction. Defined on boolean types.
12082 Boolean conjunction. Defined on boolean types.
12085 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12088 Addition and subtraction on integral and floating-point types, or union
12089 and difference on set types.
12092 Multiplication on integral and floating-point types, or set intersection
12096 Division on floating-point types, or symmetric set difference on set
12097 types. Same precedence as @code{*}.
12100 Integer division and remainder. Defined on integral types. Same
12101 precedence as @code{*}.
12104 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12107 Pointer dereferencing. Defined on pointer types.
12110 Boolean negation. Defined on boolean types. Same precedence as
12114 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12115 precedence as @code{^}.
12118 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12121 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12125 @value{GDBN} and Modula-2 scope operators.
12129 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12130 treats the use of the operator @code{IN}, or the use of operators
12131 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12132 @code{<=}, and @code{>=} on sets as an error.
12136 @node Built-In Func/Proc
12137 @subsubsection Built-in Functions and Procedures
12138 @cindex Modula-2 built-ins
12140 Modula-2 also makes available several built-in procedures and functions.
12141 In describing these, the following metavariables are used:
12146 represents an @code{ARRAY} variable.
12149 represents a @code{CHAR} constant or variable.
12152 represents a variable or constant of integral type.
12155 represents an identifier that belongs to a set. Generally used in the
12156 same function with the metavariable @var{s}. The type of @var{s} should
12157 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12160 represents a variable or constant of integral or floating-point type.
12163 represents a variable or constant of floating-point type.
12169 represents a variable.
12172 represents a variable or constant of one of many types. See the
12173 explanation of the function for details.
12176 All Modula-2 built-in procedures also return a result, described below.
12180 Returns the absolute value of @var{n}.
12183 If @var{c} is a lower case letter, it returns its upper case
12184 equivalent, otherwise it returns its argument.
12187 Returns the character whose ordinal value is @var{i}.
12190 Decrements the value in the variable @var{v} by one. Returns the new value.
12192 @item DEC(@var{v},@var{i})
12193 Decrements the value in the variable @var{v} by @var{i}. Returns the
12196 @item EXCL(@var{m},@var{s})
12197 Removes the element @var{m} from the set @var{s}. Returns the new
12200 @item FLOAT(@var{i})
12201 Returns the floating point equivalent of the integer @var{i}.
12203 @item HIGH(@var{a})
12204 Returns the index of the last member of @var{a}.
12207 Increments the value in the variable @var{v} by one. Returns the new value.
12209 @item INC(@var{v},@var{i})
12210 Increments the value in the variable @var{v} by @var{i}. Returns the
12213 @item INCL(@var{m},@var{s})
12214 Adds the element @var{m} to the set @var{s} if it is not already
12215 there. Returns the new set.
12218 Returns the maximum value of the type @var{t}.
12221 Returns the minimum value of the type @var{t}.
12224 Returns boolean TRUE if @var{i} is an odd number.
12227 Returns the ordinal value of its argument. For example, the ordinal
12228 value of a character is its @sc{ascii} value (on machines supporting the
12229 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12230 integral, character and enumerated types.
12232 @item SIZE(@var{x})
12233 Returns the size of its argument. @var{x} can be a variable or a type.
12235 @item TRUNC(@var{r})
12236 Returns the integral part of @var{r}.
12238 @item TSIZE(@var{x})
12239 Returns the size of its argument. @var{x} can be a variable or a type.
12241 @item VAL(@var{t},@var{i})
12242 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12246 @emph{Warning:} Sets and their operations are not yet supported, so
12247 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12251 @cindex Modula-2 constants
12253 @subsubsection Constants
12255 @value{GDBN} allows you to express the constants of Modula-2 in the following
12261 Integer constants are simply a sequence of digits. When used in an
12262 expression, a constant is interpreted to be type-compatible with the
12263 rest of the expression. Hexadecimal integers are specified by a
12264 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12267 Floating point constants appear as a sequence of digits, followed by a
12268 decimal point and another sequence of digits. An optional exponent can
12269 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12270 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12271 digits of the floating point constant must be valid decimal (base 10)
12275 Character constants consist of a single character enclosed by a pair of
12276 like quotes, either single (@code{'}) or double (@code{"}). They may
12277 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12278 followed by a @samp{C}.
12281 String constants consist of a sequence of characters enclosed by a
12282 pair of like quotes, either single (@code{'}) or double (@code{"}).
12283 Escape sequences in the style of C are also allowed. @xref{C
12284 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12288 Enumerated constants consist of an enumerated identifier.
12291 Boolean constants consist of the identifiers @code{TRUE} and
12295 Pointer constants consist of integral values only.
12298 Set constants are not yet supported.
12302 @subsubsection Modula-2 Types
12303 @cindex Modula-2 types
12305 Currently @value{GDBN} can print the following data types in Modula-2
12306 syntax: array types, record types, set types, pointer types, procedure
12307 types, enumerated types, subrange types and base types. You can also
12308 print the contents of variables declared using these type.
12309 This section gives a number of simple source code examples together with
12310 sample @value{GDBN} sessions.
12312 The first example contains the following section of code:
12321 and you can request @value{GDBN} to interrogate the type and value of
12322 @code{r} and @code{s}.
12325 (@value{GDBP}) print s
12327 (@value{GDBP}) ptype s
12329 (@value{GDBP}) print r
12331 (@value{GDBP}) ptype r
12336 Likewise if your source code declares @code{s} as:
12340 s: SET ['A'..'Z'] ;
12344 then you may query the type of @code{s} by:
12347 (@value{GDBP}) ptype s
12348 type = SET ['A'..'Z']
12352 Note that at present you cannot interactively manipulate set
12353 expressions using the debugger.
12355 The following example shows how you might declare an array in Modula-2
12356 and how you can interact with @value{GDBN} to print its type and contents:
12360 s: ARRAY [-10..10] OF CHAR ;
12364 (@value{GDBP}) ptype s
12365 ARRAY [-10..10] OF CHAR
12368 Note that the array handling is not yet complete and although the type
12369 is printed correctly, expression handling still assumes that all
12370 arrays have a lower bound of zero and not @code{-10} as in the example
12373 Here are some more type related Modula-2 examples:
12377 colour = (blue, red, yellow, green) ;
12378 t = [blue..yellow] ;
12386 The @value{GDBN} interaction shows how you can query the data type
12387 and value of a variable.
12390 (@value{GDBP}) print s
12392 (@value{GDBP}) ptype t
12393 type = [blue..yellow]
12397 In this example a Modula-2 array is declared and its contents
12398 displayed. Observe that the contents are written in the same way as
12399 their @code{C} counterparts.
12403 s: ARRAY [1..5] OF CARDINAL ;
12409 (@value{GDBP}) print s
12410 $1 = @{1, 0, 0, 0, 0@}
12411 (@value{GDBP}) ptype s
12412 type = ARRAY [1..5] OF CARDINAL
12415 The Modula-2 language interface to @value{GDBN} also understands
12416 pointer types as shown in this example:
12420 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12427 and you can request that @value{GDBN} describes the type of @code{s}.
12430 (@value{GDBP}) ptype s
12431 type = POINTER TO ARRAY [1..5] OF CARDINAL
12434 @value{GDBN} handles compound types as we can see in this example.
12435 Here we combine array types, record types, pointer types and subrange
12446 myarray = ARRAY myrange OF CARDINAL ;
12447 myrange = [-2..2] ;
12449 s: POINTER TO ARRAY myrange OF foo ;
12453 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12457 (@value{GDBP}) ptype s
12458 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12461 f3 : ARRAY [-2..2] OF CARDINAL;
12466 @subsubsection Modula-2 Defaults
12467 @cindex Modula-2 defaults
12469 If type and range checking are set automatically by @value{GDBN}, they
12470 both default to @code{on} whenever the working language changes to
12471 Modula-2. This happens regardless of whether you or @value{GDBN}
12472 selected the working language.
12474 If you allow @value{GDBN} to set the language automatically, then entering
12475 code compiled from a file whose name ends with @file{.mod} sets the
12476 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12477 Infer the Source Language}, for further details.
12480 @subsubsection Deviations from Standard Modula-2
12481 @cindex Modula-2, deviations from
12483 A few changes have been made to make Modula-2 programs easier to debug.
12484 This is done primarily via loosening its type strictness:
12488 Unlike in standard Modula-2, pointer constants can be formed by
12489 integers. This allows you to modify pointer variables during
12490 debugging. (In standard Modula-2, the actual address contained in a
12491 pointer variable is hidden from you; it can only be modified
12492 through direct assignment to another pointer variable or expression that
12493 returned a pointer.)
12496 C escape sequences can be used in strings and characters to represent
12497 non-printable characters. @value{GDBN} prints out strings with these
12498 escape sequences embedded. Single non-printable characters are
12499 printed using the @samp{CHR(@var{nnn})} format.
12502 The assignment operator (@code{:=}) returns the value of its right-hand
12506 All built-in procedures both modify @emph{and} return their argument.
12510 @subsubsection Modula-2 Type and Range Checks
12511 @cindex Modula-2 checks
12514 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12517 @c FIXME remove warning when type/range checks added
12519 @value{GDBN} considers two Modula-2 variables type equivalent if:
12523 They are of types that have been declared equivalent via a @code{TYPE
12524 @var{t1} = @var{t2}} statement
12527 They have been declared on the same line. (Note: This is true of the
12528 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12531 As long as type checking is enabled, any attempt to combine variables
12532 whose types are not equivalent is an error.
12534 Range checking is done on all mathematical operations, assignment, array
12535 index bounds, and all built-in functions and procedures.
12538 @subsubsection The Scope Operators @code{::} and @code{.}
12540 @cindex @code{.}, Modula-2 scope operator
12541 @cindex colon, doubled as scope operator
12543 @vindex colon-colon@r{, in Modula-2}
12544 @c Info cannot handle :: but TeX can.
12547 @vindex ::@r{, in Modula-2}
12550 There are a few subtle differences between the Modula-2 scope operator
12551 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12556 @var{module} . @var{id}
12557 @var{scope} :: @var{id}
12561 where @var{scope} is the name of a module or a procedure,
12562 @var{module} the name of a module, and @var{id} is any declared
12563 identifier within your program, except another module.
12565 Using the @code{::} operator makes @value{GDBN} search the scope
12566 specified by @var{scope} for the identifier @var{id}. If it is not
12567 found in the specified scope, then @value{GDBN} searches all scopes
12568 enclosing the one specified by @var{scope}.
12570 Using the @code{.} operator makes @value{GDBN} search the current scope for
12571 the identifier specified by @var{id} that was imported from the
12572 definition module specified by @var{module}. With this operator, it is
12573 an error if the identifier @var{id} was not imported from definition
12574 module @var{module}, or if @var{id} is not an identifier in
12578 @subsubsection @value{GDBN} and Modula-2
12580 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12581 Five subcommands of @code{set print} and @code{show print} apply
12582 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12583 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12584 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12585 analogue in Modula-2.
12587 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12588 with any language, is not useful with Modula-2. Its
12589 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12590 created in Modula-2 as they can in C or C@t{++}. However, because an
12591 address can be specified by an integral constant, the construct
12592 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12594 @cindex @code{#} in Modula-2
12595 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12596 interpreted as the beginning of a comment. Use @code{<>} instead.
12602 The extensions made to @value{GDBN} for Ada only support
12603 output from the @sc{gnu} Ada (GNAT) compiler.
12604 Other Ada compilers are not currently supported, and
12605 attempting to debug executables produced by them is most likely
12609 @cindex expressions in Ada
12611 * Ada Mode Intro:: General remarks on the Ada syntax
12612 and semantics supported by Ada mode
12614 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12615 * Additions to Ada:: Extensions of the Ada expression syntax.
12616 * Stopping Before Main Program:: Debugging the program during elaboration.
12617 * Ada Tasks:: Listing and setting breakpoints in tasks.
12618 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12619 * Ada Glitches:: Known peculiarities of Ada mode.
12622 @node Ada Mode Intro
12623 @subsubsection Introduction
12624 @cindex Ada mode, general
12626 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12627 syntax, with some extensions.
12628 The philosophy behind the design of this subset is
12632 That @value{GDBN} should provide basic literals and access to operations for
12633 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12634 leaving more sophisticated computations to subprograms written into the
12635 program (which therefore may be called from @value{GDBN}).
12638 That type safety and strict adherence to Ada language restrictions
12639 are not particularly important to the @value{GDBN} user.
12642 That brevity is important to the @value{GDBN} user.
12645 Thus, for brevity, the debugger acts as if all names declared in
12646 user-written packages are directly visible, even if they are not visible
12647 according to Ada rules, thus making it unnecessary to fully qualify most
12648 names with their packages, regardless of context. Where this causes
12649 ambiguity, @value{GDBN} asks the user's intent.
12651 The debugger will start in Ada mode if it detects an Ada main program.
12652 As for other languages, it will enter Ada mode when stopped in a program that
12653 was translated from an Ada source file.
12655 While in Ada mode, you may use `@t{--}' for comments. This is useful
12656 mostly for documenting command files. The standard @value{GDBN} comment
12657 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12658 middle (to allow based literals).
12660 The debugger supports limited overloading. Given a subprogram call in which
12661 the function symbol has multiple definitions, it will use the number of
12662 actual parameters and some information about their types to attempt to narrow
12663 the set of definitions. It also makes very limited use of context, preferring
12664 procedures to functions in the context of the @code{call} command, and
12665 functions to procedures elsewhere.
12667 @node Omissions from Ada
12668 @subsubsection Omissions from Ada
12669 @cindex Ada, omissions from
12671 Here are the notable omissions from the subset:
12675 Only a subset of the attributes are supported:
12679 @t{'First}, @t{'Last}, and @t{'Length}
12680 on array objects (not on types and subtypes).
12683 @t{'Min} and @t{'Max}.
12686 @t{'Pos} and @t{'Val}.
12692 @t{'Range} on array objects (not subtypes), but only as the right
12693 operand of the membership (@code{in}) operator.
12696 @t{'Access}, @t{'Unchecked_Access}, and
12697 @t{'Unrestricted_Access} (a GNAT extension).
12705 @code{Characters.Latin_1} are not available and
12706 concatenation is not implemented. Thus, escape characters in strings are
12707 not currently available.
12710 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12711 equality of representations. They will generally work correctly
12712 for strings and arrays whose elements have integer or enumeration types.
12713 They may not work correctly for arrays whose element
12714 types have user-defined equality, for arrays of real values
12715 (in particular, IEEE-conformant floating point, because of negative
12716 zeroes and NaNs), and for arrays whose elements contain unused bits with
12717 indeterminate values.
12720 The other component-by-component array operations (@code{and}, @code{or},
12721 @code{xor}, @code{not}, and relational tests other than equality)
12722 are not implemented.
12725 @cindex array aggregates (Ada)
12726 @cindex record aggregates (Ada)
12727 @cindex aggregates (Ada)
12728 There is limited support for array and record aggregates. They are
12729 permitted only on the right sides of assignments, as in these examples:
12732 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12733 (@value{GDBP}) set An_Array := (1, others => 0)
12734 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12735 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12736 (@value{GDBP}) set A_Record := (1, "Peter", True);
12737 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12741 discriminant's value by assigning an aggregate has an
12742 undefined effect if that discriminant is used within the record.
12743 However, you can first modify discriminants by directly assigning to
12744 them (which normally would not be allowed in Ada), and then performing an
12745 aggregate assignment. For example, given a variable @code{A_Rec}
12746 declared to have a type such as:
12749 type Rec (Len : Small_Integer := 0) is record
12751 Vals : IntArray (1 .. Len);
12755 you can assign a value with a different size of @code{Vals} with two
12759 (@value{GDBP}) set A_Rec.Len := 4
12760 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12763 As this example also illustrates, @value{GDBN} is very loose about the usual
12764 rules concerning aggregates. You may leave out some of the
12765 components of an array or record aggregate (such as the @code{Len}
12766 component in the assignment to @code{A_Rec} above); they will retain their
12767 original values upon assignment. You may freely use dynamic values as
12768 indices in component associations. You may even use overlapping or
12769 redundant component associations, although which component values are
12770 assigned in such cases is not defined.
12773 Calls to dispatching subprograms are not implemented.
12776 The overloading algorithm is much more limited (i.e., less selective)
12777 than that of real Ada. It makes only limited use of the context in
12778 which a subexpression appears to resolve its meaning, and it is much
12779 looser in its rules for allowing type matches. As a result, some
12780 function calls will be ambiguous, and the user will be asked to choose
12781 the proper resolution.
12784 The @code{new} operator is not implemented.
12787 Entry calls are not implemented.
12790 Aside from printing, arithmetic operations on the native VAX floating-point
12791 formats are not supported.
12794 It is not possible to slice a packed array.
12797 The names @code{True} and @code{False}, when not part of a qualified name,
12798 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12800 Should your program
12801 redefine these names in a package or procedure (at best a dubious practice),
12802 you will have to use fully qualified names to access their new definitions.
12805 @node Additions to Ada
12806 @subsubsection Additions to Ada
12807 @cindex Ada, deviations from
12809 As it does for other languages, @value{GDBN} makes certain generic
12810 extensions to Ada (@pxref{Expressions}):
12814 If the expression @var{E} is a variable residing in memory (typically
12815 a local variable or array element) and @var{N} is a positive integer,
12816 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12817 @var{N}-1 adjacent variables following it in memory as an array. In
12818 Ada, this operator is generally not necessary, since its prime use is
12819 in displaying parts of an array, and slicing will usually do this in
12820 Ada. However, there are occasional uses when debugging programs in
12821 which certain debugging information has been optimized away.
12824 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12825 appears in function or file @var{B}.'' When @var{B} is a file name,
12826 you must typically surround it in single quotes.
12829 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12830 @var{type} that appears at address @var{addr}.''
12833 A name starting with @samp{$} is a convenience variable
12834 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12837 In addition, @value{GDBN} provides a few other shortcuts and outright
12838 additions specific to Ada:
12842 The assignment statement is allowed as an expression, returning
12843 its right-hand operand as its value. Thus, you may enter
12846 (@value{GDBP}) set x := y + 3
12847 (@value{GDBP}) print A(tmp := y + 1)
12851 The semicolon is allowed as an ``operator,'' returning as its value
12852 the value of its right-hand operand.
12853 This allows, for example,
12854 complex conditional breaks:
12857 (@value{GDBP}) break f
12858 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12862 Rather than use catenation and symbolic character names to introduce special
12863 characters into strings, one may instead use a special bracket notation,
12864 which is also used to print strings. A sequence of characters of the form
12865 @samp{["@var{XX}"]} within a string or character literal denotes the
12866 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12867 sequence of characters @samp{["""]} also denotes a single quotation mark
12868 in strings. For example,
12870 "One line.["0a"]Next line.["0a"]"
12873 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12877 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12878 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12882 (@value{GDBP}) print 'max(x, y)
12886 When printing arrays, @value{GDBN} uses positional notation when the
12887 array has a lower bound of 1, and uses a modified named notation otherwise.
12888 For example, a one-dimensional array of three integers with a lower bound
12889 of 3 might print as
12896 That is, in contrast to valid Ada, only the first component has a @code{=>}
12900 You may abbreviate attributes in expressions with any unique,
12901 multi-character subsequence of
12902 their names (an exact match gets preference).
12903 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12904 in place of @t{a'length}.
12907 @cindex quoting Ada internal identifiers
12908 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12909 to lower case. The GNAT compiler uses upper-case characters for
12910 some of its internal identifiers, which are normally of no interest to users.
12911 For the rare occasions when you actually have to look at them,
12912 enclose them in angle brackets to avoid the lower-case mapping.
12915 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12919 Printing an object of class-wide type or dereferencing an
12920 access-to-class-wide value will display all the components of the object's
12921 specific type (as indicated by its run-time tag). Likewise, component
12922 selection on such a value will operate on the specific type of the
12927 @node Stopping Before Main Program
12928 @subsubsection Stopping at the Very Beginning
12930 @cindex breakpointing Ada elaboration code
12931 It is sometimes necessary to debug the program during elaboration, and
12932 before reaching the main procedure.
12933 As defined in the Ada Reference
12934 Manual, the elaboration code is invoked from a procedure called
12935 @code{adainit}. To run your program up to the beginning of
12936 elaboration, simply use the following two commands:
12937 @code{tbreak adainit} and @code{run}.
12940 @subsubsection Extensions for Ada Tasks
12941 @cindex Ada, tasking
12943 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12944 @value{GDBN} provides the following task-related commands:
12949 This command shows a list of current Ada tasks, as in the following example:
12956 (@value{GDBP}) info tasks
12957 ID TID P-ID Pri State Name
12958 1 8088000 0 15 Child Activation Wait main_task
12959 2 80a4000 1 15 Accept Statement b
12960 3 809a800 1 15 Child Activation Wait a
12961 * 4 80ae800 3 15 Runnable c
12966 In this listing, the asterisk before the last task indicates it to be the
12967 task currently being inspected.
12971 Represents @value{GDBN}'s internal task number.
12977 The parent's task ID (@value{GDBN}'s internal task number).
12980 The base priority of the task.
12983 Current state of the task.
12987 The task has been created but has not been activated. It cannot be
12991 The task is not blocked for any reason known to Ada. (It may be waiting
12992 for a mutex, though.) It is conceptually "executing" in normal mode.
12995 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12996 that were waiting on terminate alternatives have been awakened and have
12997 terminated themselves.
12999 @item Child Activation Wait
13000 The task is waiting for created tasks to complete activation.
13002 @item Accept Statement
13003 The task is waiting on an accept or selective wait statement.
13005 @item Waiting on entry call
13006 The task is waiting on an entry call.
13008 @item Async Select Wait
13009 The task is waiting to start the abortable part of an asynchronous
13013 The task is waiting on a select statement with only a delay
13016 @item Child Termination Wait
13017 The task is sleeping having completed a master within itself, and is
13018 waiting for the tasks dependent on that master to become terminated or
13019 waiting on a terminate Phase.
13021 @item Wait Child in Term Alt
13022 The task is sleeping waiting for tasks on terminate alternatives to
13023 finish terminating.
13025 @item Accepting RV with @var{taskno}
13026 The task is accepting a rendez-vous with the task @var{taskno}.
13030 Name of the task in the program.
13034 @kindex info task @var{taskno}
13035 @item info task @var{taskno}
13036 This command shows detailled informations on the specified task, as in
13037 the following example:
13042 (@value{GDBP}) info tasks
13043 ID TID P-ID Pri State Name
13044 1 8077880 0 15 Child Activation Wait main_task
13045 * 2 807c468 1 15 Runnable task_1
13046 (@value{GDBP}) info task 2
13047 Ada Task: 0x807c468
13050 Parent: 1 (main_task)
13056 @kindex task@r{ (Ada)}
13057 @cindex current Ada task ID
13058 This command prints the ID of the current task.
13064 (@value{GDBP}) info tasks
13065 ID TID P-ID Pri State Name
13066 1 8077870 0 15 Child Activation Wait main_task
13067 * 2 807c458 1 15 Runnable t
13068 (@value{GDBP}) task
13069 [Current task is 2]
13072 @item task @var{taskno}
13073 @cindex Ada task switching
13074 This command is like the @code{thread @var{threadno}}
13075 command (@pxref{Threads}). It switches the context of debugging
13076 from the current task to the given task.
13082 (@value{GDBP}) info tasks
13083 ID TID P-ID Pri State Name
13084 1 8077870 0 15 Child Activation Wait main_task
13085 * 2 807c458 1 15 Runnable t
13086 (@value{GDBP}) task 1
13087 [Switching to task 1]
13088 #0 0x8067726 in pthread_cond_wait ()
13090 #0 0x8067726 in pthread_cond_wait ()
13091 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13092 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13093 #3 0x806153e in system.tasking.stages.activate_tasks ()
13094 #4 0x804aacc in un () at un.adb:5
13097 @item break @var{linespec} task @var{taskno}
13098 @itemx break @var{linespec} task @var{taskno} if @dots{}
13099 @cindex breakpoints and tasks, in Ada
13100 @cindex task breakpoints, in Ada
13101 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13102 These commands are like the @code{break @dots{} thread @dots{}}
13103 command (@pxref{Thread Stops}).
13104 @var{linespec} specifies source lines, as described
13105 in @ref{Specify Location}.
13107 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13108 to specify that you only want @value{GDBN} to stop the program when a
13109 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13110 numeric task identifiers assigned by @value{GDBN}, shown in the first
13111 column of the @samp{info tasks} display.
13113 If you do not specify @samp{task @var{taskno}} when you set a
13114 breakpoint, the breakpoint applies to @emph{all} tasks of your
13117 You can use the @code{task} qualifier on conditional breakpoints as
13118 well; in this case, place @samp{task @var{taskno}} before the
13119 breakpoint condition (before the @code{if}).
13127 (@value{GDBP}) info tasks
13128 ID TID P-ID Pri State Name
13129 1 140022020 0 15 Child Activation Wait main_task
13130 2 140045060 1 15 Accept/Select Wait t2
13131 3 140044840 1 15 Runnable t1
13132 * 4 140056040 1 15 Runnable t3
13133 (@value{GDBP}) b 15 task 2
13134 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13135 (@value{GDBP}) cont
13140 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13142 (@value{GDBP}) info tasks
13143 ID TID P-ID Pri State Name
13144 1 140022020 0 15 Child Activation Wait main_task
13145 * 2 140045060 1 15 Runnable t2
13146 3 140044840 1 15 Runnable t1
13147 4 140056040 1 15 Delay Sleep t3
13151 @node Ada Tasks and Core Files
13152 @subsubsection Tasking Support when Debugging Core Files
13153 @cindex Ada tasking and core file debugging
13155 When inspecting a core file, as opposed to debugging a live program,
13156 tasking support may be limited or even unavailable, depending on
13157 the platform being used.
13158 For instance, on x86-linux, the list of tasks is available, but task
13159 switching is not supported. On Tru64, however, task switching will work
13162 On certain platforms, including Tru64, the debugger needs to perform some
13163 memory writes in order to provide Ada tasking support. When inspecting
13164 a core file, this means that the core file must be opened with read-write
13165 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13166 Under these circumstances, you should make a backup copy of the core
13167 file before inspecting it with @value{GDBN}.
13170 @subsubsection Known Peculiarities of Ada Mode
13171 @cindex Ada, problems
13173 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13174 we know of several problems with and limitations of Ada mode in
13176 some of which will be fixed with planned future releases of the debugger
13177 and the GNU Ada compiler.
13181 Currently, the debugger
13182 has insufficient information to determine whether certain pointers represent
13183 pointers to objects or the objects themselves.
13184 Thus, the user may have to tack an extra @code{.all} after an expression
13185 to get it printed properly.
13188 Static constants that the compiler chooses not to materialize as objects in
13189 storage are invisible to the debugger.
13192 Named parameter associations in function argument lists are ignored (the
13193 argument lists are treated as positional).
13196 Many useful library packages are currently invisible to the debugger.
13199 Fixed-point arithmetic, conversions, input, and output is carried out using
13200 floating-point arithmetic, and may give results that only approximate those on
13204 The GNAT compiler never generates the prefix @code{Standard} for any of
13205 the standard symbols defined by the Ada language. @value{GDBN} knows about
13206 this: it will strip the prefix from names when you use it, and will never
13207 look for a name you have so qualified among local symbols, nor match against
13208 symbols in other packages or subprograms. If you have
13209 defined entities anywhere in your program other than parameters and
13210 local variables whose simple names match names in @code{Standard},
13211 GNAT's lack of qualification here can cause confusion. When this happens,
13212 you can usually resolve the confusion
13213 by qualifying the problematic names with package
13214 @code{Standard} explicitly.
13217 Older versions of the compiler sometimes generate erroneous debugging
13218 information, resulting in the debugger incorrectly printing the value
13219 of affected entities. In some cases, the debugger is able to work
13220 around an issue automatically. In other cases, the debugger is able
13221 to work around the issue, but the work-around has to be specifically
13224 @kindex set ada trust-PAD-over-XVS
13225 @kindex show ada trust-PAD-over-XVS
13228 @item set ada trust-PAD-over-XVS on
13229 Configure GDB to strictly follow the GNAT encoding when computing the
13230 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13231 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13232 a complete description of the encoding used by the GNAT compiler).
13233 This is the default.
13235 @item set ada trust-PAD-over-XVS off
13236 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13237 sometimes prints the wrong value for certain entities, changing @code{ada
13238 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13239 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13240 @code{off}, but this incurs a slight performance penalty, so it is
13241 recommended to leave this setting to @code{on} unless necessary.
13245 @node Unsupported Languages
13246 @section Unsupported Languages
13248 @cindex unsupported languages
13249 @cindex minimal language
13250 In addition to the other fully-supported programming languages,
13251 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13252 It does not represent a real programming language, but provides a set
13253 of capabilities close to what the C or assembly languages provide.
13254 This should allow most simple operations to be performed while debugging
13255 an application that uses a language currently not supported by @value{GDBN}.
13257 If the language is set to @code{auto}, @value{GDBN} will automatically
13258 select this language if the current frame corresponds to an unsupported
13262 @chapter Examining the Symbol Table
13264 The commands described in this chapter allow you to inquire about the
13265 symbols (names of variables, functions and types) defined in your
13266 program. This information is inherent in the text of your program and
13267 does not change as your program executes. @value{GDBN} finds it in your
13268 program's symbol table, in the file indicated when you started @value{GDBN}
13269 (@pxref{File Options, ,Choosing Files}), or by one of the
13270 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13272 @cindex symbol names
13273 @cindex names of symbols
13274 @cindex quoting names
13275 Occasionally, you may need to refer to symbols that contain unusual
13276 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13277 most frequent case is in referring to static variables in other
13278 source files (@pxref{Variables,,Program Variables}). File names
13279 are recorded in object files as debugging symbols, but @value{GDBN} would
13280 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13281 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13282 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13289 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13292 @cindex case-insensitive symbol names
13293 @cindex case sensitivity in symbol names
13294 @kindex set case-sensitive
13295 @item set case-sensitive on
13296 @itemx set case-sensitive off
13297 @itemx set case-sensitive auto
13298 Normally, when @value{GDBN} looks up symbols, it matches their names
13299 with case sensitivity determined by the current source language.
13300 Occasionally, you may wish to control that. The command @code{set
13301 case-sensitive} lets you do that by specifying @code{on} for
13302 case-sensitive matches or @code{off} for case-insensitive ones. If
13303 you specify @code{auto}, case sensitivity is reset to the default
13304 suitable for the source language. The default is case-sensitive
13305 matches for all languages except for Fortran, for which the default is
13306 case-insensitive matches.
13308 @kindex show case-sensitive
13309 @item show case-sensitive
13310 This command shows the current setting of case sensitivity for symbols
13313 @kindex info address
13314 @cindex address of a symbol
13315 @item info address @var{symbol}
13316 Describe where the data for @var{symbol} is stored. For a register
13317 variable, this says which register it is kept in. For a non-register
13318 local variable, this prints the stack-frame offset at which the variable
13321 Note the contrast with @samp{print &@var{symbol}}, which does not work
13322 at all for a register variable, and for a stack local variable prints
13323 the exact address of the current instantiation of the variable.
13325 @kindex info symbol
13326 @cindex symbol from address
13327 @cindex closest symbol and offset for an address
13328 @item info symbol @var{addr}
13329 Print the name of a symbol which is stored at the address @var{addr}.
13330 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13331 nearest symbol and an offset from it:
13334 (@value{GDBP}) info symbol 0x54320
13335 _initialize_vx + 396 in section .text
13339 This is the opposite of the @code{info address} command. You can use
13340 it to find out the name of a variable or a function given its address.
13342 For dynamically linked executables, the name of executable or shared
13343 library containing the symbol is also printed:
13346 (@value{GDBP}) info symbol 0x400225
13347 _start + 5 in section .text of /tmp/a.out
13348 (@value{GDBP}) info symbol 0x2aaaac2811cf
13349 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13353 @item whatis [@var{arg}]
13354 Print the data type of @var{arg}, which can be either an expression or
13355 a data type. With no argument, print the data type of @code{$}, the
13356 last value in the value history. If @var{arg} is an expression, it is
13357 not actually evaluated, and any side-effecting operations (such as
13358 assignments or function calls) inside it do not take place. If
13359 @var{arg} is a type name, it may be the name of a type or typedef, or
13360 for C code it may have the form @samp{class @var{class-name}},
13361 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13362 @samp{enum @var{enum-tag}}.
13363 @xref{Expressions, ,Expressions}.
13366 @item ptype [@var{arg}]
13367 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13368 detailed description of the type, instead of just the name of the type.
13369 @xref{Expressions, ,Expressions}.
13371 For example, for this variable declaration:
13374 struct complex @{double real; double imag;@} v;
13378 the two commands give this output:
13382 (@value{GDBP}) whatis v
13383 type = struct complex
13384 (@value{GDBP}) ptype v
13385 type = struct complex @{
13393 As with @code{whatis}, using @code{ptype} without an argument refers to
13394 the type of @code{$}, the last value in the value history.
13396 @cindex incomplete type
13397 Sometimes, programs use opaque data types or incomplete specifications
13398 of complex data structure. If the debug information included in the
13399 program does not allow @value{GDBN} to display a full declaration of
13400 the data type, it will say @samp{<incomplete type>}. For example,
13401 given these declarations:
13405 struct foo *fooptr;
13409 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13412 (@value{GDBP}) ptype foo
13413 $1 = <incomplete type>
13417 ``Incomplete type'' is C terminology for data types that are not
13418 completely specified.
13421 @item info types @var{regexp}
13423 Print a brief description of all types whose names match the regular
13424 expression @var{regexp} (or all types in your program, if you supply
13425 no argument). Each complete typename is matched as though it were a
13426 complete line; thus, @samp{i type value} gives information on all
13427 types in your program whose names include the string @code{value}, but
13428 @samp{i type ^value$} gives information only on types whose complete
13429 name is @code{value}.
13431 This command differs from @code{ptype} in two ways: first, like
13432 @code{whatis}, it does not print a detailed description; second, it
13433 lists all source files where a type is defined.
13436 @cindex local variables
13437 @item info scope @var{location}
13438 List all the variables local to a particular scope. This command
13439 accepts a @var{location} argument---a function name, a source line, or
13440 an address preceded by a @samp{*}, and prints all the variables local
13441 to the scope defined by that location. (@xref{Specify Location}, for
13442 details about supported forms of @var{location}.) For example:
13445 (@value{GDBP}) @b{info scope command_line_handler}
13446 Scope for command_line_handler:
13447 Symbol rl is an argument at stack/frame offset 8, length 4.
13448 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13449 Symbol linelength is in static storage at address 0x150a1c, length 4.
13450 Symbol p is a local variable in register $esi, length 4.
13451 Symbol p1 is a local variable in register $ebx, length 4.
13452 Symbol nline is a local variable in register $edx, length 4.
13453 Symbol repeat is a local variable at frame offset -8, length 4.
13457 This command is especially useful for determining what data to collect
13458 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13461 @kindex info source
13463 Show information about the current source file---that is, the source file for
13464 the function containing the current point of execution:
13467 the name of the source file, and the directory containing it,
13469 the directory it was compiled in,
13471 its length, in lines,
13473 which programming language it is written in,
13475 whether the executable includes debugging information for that file, and
13476 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13478 whether the debugging information includes information about
13479 preprocessor macros.
13483 @kindex info sources
13485 Print the names of all source files in your program for which there is
13486 debugging information, organized into two lists: files whose symbols
13487 have already been read, and files whose symbols will be read when needed.
13489 @kindex info functions
13490 @item info functions
13491 Print the names and data types of all defined functions.
13493 @item info functions @var{regexp}
13494 Print the names and data types of all defined functions
13495 whose names contain a match for regular expression @var{regexp}.
13496 Thus, @samp{info fun step} finds all functions whose names
13497 include @code{step}; @samp{info fun ^step} finds those whose names
13498 start with @code{step}. If a function name contains characters
13499 that conflict with the regular expression language (e.g.@:
13500 @samp{operator*()}), they may be quoted with a backslash.
13502 @kindex info variables
13503 @item info variables
13504 Print the names and data types of all variables that are defined
13505 outside of functions (i.e.@: excluding local variables).
13507 @item info variables @var{regexp}
13508 Print the names and data types of all variables (except for local
13509 variables) whose names contain a match for regular expression
13512 @kindex info classes
13513 @cindex Objective-C, classes and selectors
13515 @itemx info classes @var{regexp}
13516 Display all Objective-C classes in your program, or
13517 (with the @var{regexp} argument) all those matching a particular regular
13520 @kindex info selectors
13521 @item info selectors
13522 @itemx info selectors @var{regexp}
13523 Display all Objective-C selectors in your program, or
13524 (with the @var{regexp} argument) all those matching a particular regular
13528 This was never implemented.
13529 @kindex info methods
13531 @itemx info methods @var{regexp}
13532 The @code{info methods} command permits the user to examine all defined
13533 methods within C@t{++} program, or (with the @var{regexp} argument) a
13534 specific set of methods found in the various C@t{++} classes. Many
13535 C@t{++} classes provide a large number of methods. Thus, the output
13536 from the @code{ptype} command can be overwhelming and hard to use. The
13537 @code{info-methods} command filters the methods, printing only those
13538 which match the regular-expression @var{regexp}.
13541 @cindex reloading symbols
13542 Some systems allow individual object files that make up your program to
13543 be replaced without stopping and restarting your program. For example,
13544 in VxWorks you can simply recompile a defective object file and keep on
13545 running. If you are running on one of these systems, you can allow
13546 @value{GDBN} to reload the symbols for automatically relinked modules:
13549 @kindex set symbol-reloading
13550 @item set symbol-reloading on
13551 Replace symbol definitions for the corresponding source file when an
13552 object file with a particular name is seen again.
13554 @item set symbol-reloading off
13555 Do not replace symbol definitions when encountering object files of the
13556 same name more than once. This is the default state; if you are not
13557 running on a system that permits automatic relinking of modules, you
13558 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13559 may discard symbols when linking large programs, that may contain
13560 several modules (from different directories or libraries) with the same
13563 @kindex show symbol-reloading
13564 @item show symbol-reloading
13565 Show the current @code{on} or @code{off} setting.
13568 @cindex opaque data types
13569 @kindex set opaque-type-resolution
13570 @item set opaque-type-resolution on
13571 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13572 declared as a pointer to a @code{struct}, @code{class}, or
13573 @code{union}---for example, @code{struct MyType *}---that is used in one
13574 source file although the full declaration of @code{struct MyType} is in
13575 another source file. The default is on.
13577 A change in the setting of this subcommand will not take effect until
13578 the next time symbols for a file are loaded.
13580 @item set opaque-type-resolution off
13581 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13582 is printed as follows:
13584 @{<no data fields>@}
13587 @kindex show opaque-type-resolution
13588 @item show opaque-type-resolution
13589 Show whether opaque types are resolved or not.
13591 @kindex maint print symbols
13592 @cindex symbol dump
13593 @kindex maint print psymbols
13594 @cindex partial symbol dump
13595 @item maint print symbols @var{filename}
13596 @itemx maint print psymbols @var{filename}
13597 @itemx maint print msymbols @var{filename}
13598 Write a dump of debugging symbol data into the file @var{filename}.
13599 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13600 symbols with debugging data are included. If you use @samp{maint print
13601 symbols}, @value{GDBN} includes all the symbols for which it has already
13602 collected full details: that is, @var{filename} reflects symbols for
13603 only those files whose symbols @value{GDBN} has read. You can use the
13604 command @code{info sources} to find out which files these are. If you
13605 use @samp{maint print psymbols} instead, the dump shows information about
13606 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13607 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13608 @samp{maint print msymbols} dumps just the minimal symbol information
13609 required for each object file from which @value{GDBN} has read some symbols.
13610 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13611 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13613 @kindex maint info symtabs
13614 @kindex maint info psymtabs
13615 @cindex listing @value{GDBN}'s internal symbol tables
13616 @cindex symbol tables, listing @value{GDBN}'s internal
13617 @cindex full symbol tables, listing @value{GDBN}'s internal
13618 @cindex partial symbol tables, listing @value{GDBN}'s internal
13619 @item maint info symtabs @r{[} @var{regexp} @r{]}
13620 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13622 List the @code{struct symtab} or @code{struct partial_symtab}
13623 structures whose names match @var{regexp}. If @var{regexp} is not
13624 given, list them all. The output includes expressions which you can
13625 copy into a @value{GDBN} debugging this one to examine a particular
13626 structure in more detail. For example:
13629 (@value{GDBP}) maint info psymtabs dwarf2read
13630 @{ objfile /home/gnu/build/gdb/gdb
13631 ((struct objfile *) 0x82e69d0)
13632 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13633 ((struct partial_symtab *) 0x8474b10)
13636 text addresses 0x814d3c8 -- 0x8158074
13637 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13638 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13639 dependencies (none)
13642 (@value{GDBP}) maint info symtabs
13646 We see that there is one partial symbol table whose filename contains
13647 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13648 and we see that @value{GDBN} has not read in any symtabs yet at all.
13649 If we set a breakpoint on a function, that will cause @value{GDBN} to
13650 read the symtab for the compilation unit containing that function:
13653 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13654 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13656 (@value{GDBP}) maint info symtabs
13657 @{ objfile /home/gnu/build/gdb/gdb
13658 ((struct objfile *) 0x82e69d0)
13659 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13660 ((struct symtab *) 0x86c1f38)
13663 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13664 linetable ((struct linetable *) 0x8370fa0)
13665 debugformat DWARF 2
13674 @chapter Altering Execution
13676 Once you think you have found an error in your program, you might want to
13677 find out for certain whether correcting the apparent error would lead to
13678 correct results in the rest of the run. You can find the answer by
13679 experiment, using the @value{GDBN} features for altering execution of the
13682 For example, you can store new values into variables or memory
13683 locations, give your program a signal, restart it at a different
13684 address, or even return prematurely from a function.
13687 * Assignment:: Assignment to variables
13688 * Jumping:: Continuing at a different address
13689 * Signaling:: Giving your program a signal
13690 * Returning:: Returning from a function
13691 * Calling:: Calling your program's functions
13692 * Patching:: Patching your program
13696 @section Assignment to Variables
13699 @cindex setting variables
13700 To alter the value of a variable, evaluate an assignment expression.
13701 @xref{Expressions, ,Expressions}. For example,
13708 stores the value 4 into the variable @code{x}, and then prints the
13709 value of the assignment expression (which is 4).
13710 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13711 information on operators in supported languages.
13713 @kindex set variable
13714 @cindex variables, setting
13715 If you are not interested in seeing the value of the assignment, use the
13716 @code{set} command instead of the @code{print} command. @code{set} is
13717 really the same as @code{print} except that the expression's value is
13718 not printed and is not put in the value history (@pxref{Value History,
13719 ,Value History}). The expression is evaluated only for its effects.
13721 If the beginning of the argument string of the @code{set} command
13722 appears identical to a @code{set} subcommand, use the @code{set
13723 variable} command instead of just @code{set}. This command is identical
13724 to @code{set} except for its lack of subcommands. For example, if your
13725 program has a variable @code{width}, you get an error if you try to set
13726 a new value with just @samp{set width=13}, because @value{GDBN} has the
13727 command @code{set width}:
13730 (@value{GDBP}) whatis width
13732 (@value{GDBP}) p width
13734 (@value{GDBP}) set width=47
13735 Invalid syntax in expression.
13739 The invalid expression, of course, is @samp{=47}. In
13740 order to actually set the program's variable @code{width}, use
13743 (@value{GDBP}) set var width=47
13746 Because the @code{set} command has many subcommands that can conflict
13747 with the names of program variables, it is a good idea to use the
13748 @code{set variable} command instead of just @code{set}. For example, if
13749 your program has a variable @code{g}, you run into problems if you try
13750 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13751 the command @code{set gnutarget}, abbreviated @code{set g}:
13755 (@value{GDBP}) whatis g
13759 (@value{GDBP}) set g=4
13763 The program being debugged has been started already.
13764 Start it from the beginning? (y or n) y
13765 Starting program: /home/smith/cc_progs/a.out
13766 "/home/smith/cc_progs/a.out": can't open to read symbols:
13767 Invalid bfd target.
13768 (@value{GDBP}) show g
13769 The current BFD target is "=4".
13774 The program variable @code{g} did not change, and you silently set the
13775 @code{gnutarget} to an invalid value. In order to set the variable
13779 (@value{GDBP}) set var g=4
13782 @value{GDBN} allows more implicit conversions in assignments than C; you can
13783 freely store an integer value into a pointer variable or vice versa,
13784 and you can convert any structure to any other structure that is the
13785 same length or shorter.
13786 @comment FIXME: how do structs align/pad in these conversions?
13787 @comment /doc@cygnus.com 18dec1990
13789 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13790 construct to generate a value of specified type at a specified address
13791 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13792 to memory location @code{0x83040} as an integer (which implies a certain size
13793 and representation in memory), and
13796 set @{int@}0x83040 = 4
13800 stores the value 4 into that memory location.
13803 @section Continuing at a Different Address
13805 Ordinarily, when you continue your program, you do so at the place where
13806 it stopped, with the @code{continue} command. You can instead continue at
13807 an address of your own choosing, with the following commands:
13811 @item jump @var{linespec}
13812 @itemx jump @var{location}
13813 Resume execution at line @var{linespec} or at address given by
13814 @var{location}. Execution stops again immediately if there is a
13815 breakpoint there. @xref{Specify Location}, for a description of the
13816 different forms of @var{linespec} and @var{location}. It is common
13817 practice to use the @code{tbreak} command in conjunction with
13818 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13820 The @code{jump} command does not change the current stack frame, or
13821 the stack pointer, or the contents of any memory location or any
13822 register other than the program counter. If line @var{linespec} is in
13823 a different function from the one currently executing, the results may
13824 be bizarre if the two functions expect different patterns of arguments or
13825 of local variables. For this reason, the @code{jump} command requests
13826 confirmation if the specified line is not in the function currently
13827 executing. However, even bizarre results are predictable if you are
13828 well acquainted with the machine-language code of your program.
13831 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13832 On many systems, you can get much the same effect as the @code{jump}
13833 command by storing a new value into the register @code{$pc}. The
13834 difference is that this does not start your program running; it only
13835 changes the address of where it @emph{will} run when you continue. For
13843 makes the next @code{continue} command or stepping command execute at
13844 address @code{0x485}, rather than at the address where your program stopped.
13845 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13847 The most common occasion to use the @code{jump} command is to back
13848 up---perhaps with more breakpoints set---over a portion of a program
13849 that has already executed, in order to examine its execution in more
13854 @section Giving your Program a Signal
13855 @cindex deliver a signal to a program
13859 @item signal @var{signal}
13860 Resume execution where your program stopped, but immediately give it the
13861 signal @var{signal}. @var{signal} can be the name or the number of a
13862 signal. For example, on many systems @code{signal 2} and @code{signal
13863 SIGINT} are both ways of sending an interrupt signal.
13865 Alternatively, if @var{signal} is zero, continue execution without
13866 giving a signal. This is useful when your program stopped on account of
13867 a signal and would ordinary see the signal when resumed with the
13868 @code{continue} command; @samp{signal 0} causes it to resume without a
13871 @code{signal} does not repeat when you press @key{RET} a second time
13872 after executing the command.
13876 Invoking the @code{signal} command is not the same as invoking the
13877 @code{kill} utility from the shell. Sending a signal with @code{kill}
13878 causes @value{GDBN} to decide what to do with the signal depending on
13879 the signal handling tables (@pxref{Signals}). The @code{signal} command
13880 passes the signal directly to your program.
13884 @section Returning from a Function
13887 @cindex returning from a function
13890 @itemx return @var{expression}
13891 You can cancel execution of a function call with the @code{return}
13892 command. If you give an
13893 @var{expression} argument, its value is used as the function's return
13897 When you use @code{return}, @value{GDBN} discards the selected stack frame
13898 (and all frames within it). You can think of this as making the
13899 discarded frame return prematurely. If you wish to specify a value to
13900 be returned, give that value as the argument to @code{return}.
13902 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13903 Frame}), and any other frames inside of it, leaving its caller as the
13904 innermost remaining frame. That frame becomes selected. The
13905 specified value is stored in the registers used for returning values
13908 The @code{return} command does not resume execution; it leaves the
13909 program stopped in the state that would exist if the function had just
13910 returned. In contrast, the @code{finish} command (@pxref{Continuing
13911 and Stepping, ,Continuing and Stepping}) resumes execution until the
13912 selected stack frame returns naturally.
13914 @value{GDBN} needs to know how the @var{expression} argument should be set for
13915 the inferior. The concrete registers assignment depends on the OS ABI and the
13916 type being returned by the selected stack frame. For example it is common for
13917 OS ABI to return floating point values in FPU registers while integer values in
13918 CPU registers. Still some ABIs return even floating point values in CPU
13919 registers. Larger integer widths (such as @code{long long int}) also have
13920 specific placement rules. @value{GDBN} already knows the OS ABI from its
13921 current target so it needs to find out also the type being returned to make the
13922 assignment into the right register(s).
13924 Normally, the selected stack frame has debug info. @value{GDBN} will always
13925 use the debug info instead of the implicit type of @var{expression} when the
13926 debug info is available. For example, if you type @kbd{return -1}, and the
13927 function in the current stack frame is declared to return a @code{long long
13928 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13929 into a @code{long long int}:
13932 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13934 (@value{GDBP}) return -1
13935 Make func return now? (y or n) y
13936 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13937 43 printf ("result=%lld\n", func ());
13941 However, if the selected stack frame does not have a debug info, e.g., if the
13942 function was compiled without debug info, @value{GDBN} has to find out the type
13943 to return from user. Specifying a different type by mistake may set the value
13944 in different inferior registers than the caller code expects. For example,
13945 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13946 of a @code{long long int} result for a debug info less function (on 32-bit
13947 architectures). Therefore the user is required to specify the return type by
13948 an appropriate cast explicitly:
13951 Breakpoint 2, 0x0040050b in func ()
13952 (@value{GDBP}) return -1
13953 Return value type not available for selected stack frame.
13954 Please use an explicit cast of the value to return.
13955 (@value{GDBP}) return (long long int) -1
13956 Make selected stack frame return now? (y or n) y
13957 #0 0x00400526 in main ()
13962 @section Calling Program Functions
13965 @cindex calling functions
13966 @cindex inferior functions, calling
13967 @item print @var{expr}
13968 Evaluate the expression @var{expr} and display the resulting value.
13969 @var{expr} may include calls to functions in the program being
13973 @item call @var{expr}
13974 Evaluate the expression @var{expr} without displaying @code{void}
13977 You can use this variant of the @code{print} command if you want to
13978 execute a function from your program that does not return anything
13979 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13980 with @code{void} returned values that @value{GDBN} will otherwise
13981 print. If the result is not void, it is printed and saved in the
13985 It is possible for the function you call via the @code{print} or
13986 @code{call} command to generate a signal (e.g., if there's a bug in
13987 the function, or if you passed it incorrect arguments). What happens
13988 in that case is controlled by the @code{set unwindonsignal} command.
13990 Similarly, with a C@t{++} program it is possible for the function you
13991 call via the @code{print} or @code{call} command to generate an
13992 exception that is not handled due to the constraints of the dummy
13993 frame. In this case, any exception that is raised in the frame, but has
13994 an out-of-frame exception handler will not be found. GDB builds a
13995 dummy-frame for the inferior function call, and the unwinder cannot
13996 seek for exception handlers outside of this dummy-frame. What happens
13997 in that case is controlled by the
13998 @code{set unwind-on-terminating-exception} command.
14001 @item set unwindonsignal
14002 @kindex set unwindonsignal
14003 @cindex unwind stack in called functions
14004 @cindex call dummy stack unwinding
14005 Set unwinding of the stack if a signal is received while in a function
14006 that @value{GDBN} called in the program being debugged. If set to on,
14007 @value{GDBN} unwinds the stack it created for the call and restores
14008 the context to what it was before the call. If set to off (the
14009 default), @value{GDBN} stops in the frame where the signal was
14012 @item show unwindonsignal
14013 @kindex show unwindonsignal
14014 Show the current setting of stack unwinding in the functions called by
14017 @item set unwind-on-terminating-exception
14018 @kindex set unwind-on-terminating-exception
14019 @cindex unwind stack in called functions with unhandled exceptions
14020 @cindex call dummy stack unwinding on unhandled exception.
14021 Set unwinding of the stack if a C@t{++} exception is raised, but left
14022 unhandled while in a function that @value{GDBN} called in the program being
14023 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14024 it created for the call and restores the context to what it was before
14025 the call. If set to off, @value{GDBN} the exception is delivered to
14026 the default C@t{++} exception handler and the inferior terminated.
14028 @item show unwind-on-terminating-exception
14029 @kindex show unwind-on-terminating-exception
14030 Show the current setting of stack unwinding in the functions called by
14035 @cindex weak alias functions
14036 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14037 for another function. In such case, @value{GDBN} might not pick up
14038 the type information, including the types of the function arguments,
14039 which causes @value{GDBN} to call the inferior function incorrectly.
14040 As a result, the called function will function erroneously and may
14041 even crash. A solution to that is to use the name of the aliased
14045 @section Patching Programs
14047 @cindex patching binaries
14048 @cindex writing into executables
14049 @cindex writing into corefiles
14051 By default, @value{GDBN} opens the file containing your program's
14052 executable code (or the corefile) read-only. This prevents accidental
14053 alterations to machine code; but it also prevents you from intentionally
14054 patching your program's binary.
14056 If you'd like to be able to patch the binary, you can specify that
14057 explicitly with the @code{set write} command. For example, you might
14058 want to turn on internal debugging flags, or even to make emergency
14064 @itemx set write off
14065 If you specify @samp{set write on}, @value{GDBN} opens executable and
14066 core files for both reading and writing; if you specify @kbd{set write
14067 off} (the default), @value{GDBN} opens them read-only.
14069 If you have already loaded a file, you must load it again (using the
14070 @code{exec-file} or @code{core-file} command) after changing @code{set
14071 write}, for your new setting to take effect.
14075 Display whether executable files and core files are opened for writing
14076 as well as reading.
14080 @chapter @value{GDBN} Files
14082 @value{GDBN} needs to know the file name of the program to be debugged,
14083 both in order to read its symbol table and in order to start your
14084 program. To debug a core dump of a previous run, you must also tell
14085 @value{GDBN} the name of the core dump file.
14088 * Files:: Commands to specify files
14089 * Separate Debug Files:: Debugging information in separate files
14090 * Symbol Errors:: Errors reading symbol files
14091 * Data Files:: GDB data files
14095 @section Commands to Specify Files
14097 @cindex symbol table
14098 @cindex core dump file
14100 You may want to specify executable and core dump file names. The usual
14101 way to do this is at start-up time, using the arguments to
14102 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14103 Out of @value{GDBN}}).
14105 Occasionally it is necessary to change to a different file during a
14106 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14107 specify a file you want to use. Or you are debugging a remote target
14108 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14109 Program}). In these situations the @value{GDBN} commands to specify
14110 new files are useful.
14113 @cindex executable file
14115 @item file @var{filename}
14116 Use @var{filename} as the program to be debugged. It is read for its
14117 symbols and for the contents of pure memory. It is also the program
14118 executed when you use the @code{run} command. If you do not specify a
14119 directory and the file is not found in the @value{GDBN} working directory,
14120 @value{GDBN} uses the environment variable @code{PATH} as a list of
14121 directories to search, just as the shell does when looking for a program
14122 to run. You can change the value of this variable, for both @value{GDBN}
14123 and your program, using the @code{path} command.
14125 @cindex unlinked object files
14126 @cindex patching object files
14127 You can load unlinked object @file{.o} files into @value{GDBN} using
14128 the @code{file} command. You will not be able to ``run'' an object
14129 file, but you can disassemble functions and inspect variables. Also,
14130 if the underlying BFD functionality supports it, you could use
14131 @kbd{gdb -write} to patch object files using this technique. Note
14132 that @value{GDBN} can neither interpret nor modify relocations in this
14133 case, so branches and some initialized variables will appear to go to
14134 the wrong place. But this feature is still handy from time to time.
14137 @code{file} with no argument makes @value{GDBN} discard any information it
14138 has on both executable file and the symbol table.
14141 @item exec-file @r{[} @var{filename} @r{]}
14142 Specify that the program to be run (but not the symbol table) is found
14143 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14144 if necessary to locate your program. Omitting @var{filename} means to
14145 discard information on the executable file.
14147 @kindex symbol-file
14148 @item symbol-file @r{[} @var{filename} @r{]}
14149 Read symbol table information from file @var{filename}. @code{PATH} is
14150 searched when necessary. Use the @code{file} command to get both symbol
14151 table and program to run from the same file.
14153 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14154 program's symbol table.
14156 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14157 some breakpoints and auto-display expressions. This is because they may
14158 contain pointers to the internal data recording symbols and data types,
14159 which are part of the old symbol table data being discarded inside
14162 @code{symbol-file} does not repeat if you press @key{RET} again after
14165 When @value{GDBN} is configured for a particular environment, it
14166 understands debugging information in whatever format is the standard
14167 generated for that environment; you may use either a @sc{gnu} compiler, or
14168 other compilers that adhere to the local conventions.
14169 Best results are usually obtained from @sc{gnu} compilers; for example,
14170 using @code{@value{NGCC}} you can generate debugging information for
14173 For most kinds of object files, with the exception of old SVR3 systems
14174 using COFF, the @code{symbol-file} command does not normally read the
14175 symbol table in full right away. Instead, it scans the symbol table
14176 quickly to find which source files and which symbols are present. The
14177 details are read later, one source file at a time, as they are needed.
14179 The purpose of this two-stage reading strategy is to make @value{GDBN}
14180 start up faster. For the most part, it is invisible except for
14181 occasional pauses while the symbol table details for a particular source
14182 file are being read. (The @code{set verbose} command can turn these
14183 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14184 Warnings and Messages}.)
14186 We have not implemented the two-stage strategy for COFF yet. When the
14187 symbol table is stored in COFF format, @code{symbol-file} reads the
14188 symbol table data in full right away. Note that ``stabs-in-COFF''
14189 still does the two-stage strategy, since the debug info is actually
14193 @cindex reading symbols immediately
14194 @cindex symbols, reading immediately
14195 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14196 @itemx file @r{[} -readnow @r{]} @var{filename}
14197 You can override the @value{GDBN} two-stage strategy for reading symbol
14198 tables by using the @samp{-readnow} option with any of the commands that
14199 load symbol table information, if you want to be sure @value{GDBN} has the
14200 entire symbol table available.
14202 @c FIXME: for now no mention of directories, since this seems to be in
14203 @c flux. 13mar1992 status is that in theory GDB would look either in
14204 @c current dir or in same dir as myprog; but issues like competing
14205 @c GDB's, or clutter in system dirs, mean that in practice right now
14206 @c only current dir is used. FFish says maybe a special GDB hierarchy
14207 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14211 @item core-file @r{[}@var{filename}@r{]}
14213 Specify the whereabouts of a core dump file to be used as the ``contents
14214 of memory''. Traditionally, core files contain only some parts of the
14215 address space of the process that generated them; @value{GDBN} can access the
14216 executable file itself for other parts.
14218 @code{core-file} with no argument specifies that no core file is
14221 Note that the core file is ignored when your program is actually running
14222 under @value{GDBN}. So, if you have been running your program and you
14223 wish to debug a core file instead, you must kill the subprocess in which
14224 the program is running. To do this, use the @code{kill} command
14225 (@pxref{Kill Process, ,Killing the Child Process}).
14227 @kindex add-symbol-file
14228 @cindex dynamic linking
14229 @item add-symbol-file @var{filename} @var{address}
14230 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14231 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14232 The @code{add-symbol-file} command reads additional symbol table
14233 information from the file @var{filename}. You would use this command
14234 when @var{filename} has been dynamically loaded (by some other means)
14235 into the program that is running. @var{address} should be the memory
14236 address at which the file has been loaded; @value{GDBN} cannot figure
14237 this out for itself. You can additionally specify an arbitrary number
14238 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14239 section name and base address for that section. You can specify any
14240 @var{address} as an expression.
14242 The symbol table of the file @var{filename} is added to the symbol table
14243 originally read with the @code{symbol-file} command. You can use the
14244 @code{add-symbol-file} command any number of times; the new symbol data
14245 thus read keeps adding to the old. To discard all old symbol data
14246 instead, use the @code{symbol-file} command without any arguments.
14248 @cindex relocatable object files, reading symbols from
14249 @cindex object files, relocatable, reading symbols from
14250 @cindex reading symbols from relocatable object files
14251 @cindex symbols, reading from relocatable object files
14252 @cindex @file{.o} files, reading symbols from
14253 Although @var{filename} is typically a shared library file, an
14254 executable file, or some other object file which has been fully
14255 relocated for loading into a process, you can also load symbolic
14256 information from relocatable @file{.o} files, as long as:
14260 the file's symbolic information refers only to linker symbols defined in
14261 that file, not to symbols defined by other object files,
14263 every section the file's symbolic information refers to has actually
14264 been loaded into the inferior, as it appears in the file, and
14266 you can determine the address at which every section was loaded, and
14267 provide these to the @code{add-symbol-file} command.
14271 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14272 relocatable files into an already running program; such systems
14273 typically make the requirements above easy to meet. However, it's
14274 important to recognize that many native systems use complex link
14275 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14276 assembly, for example) that make the requirements difficult to meet. In
14277 general, one cannot assume that using @code{add-symbol-file} to read a
14278 relocatable object file's symbolic information will have the same effect
14279 as linking the relocatable object file into the program in the normal
14282 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14284 @kindex add-symbol-file-from-memory
14285 @cindex @code{syscall DSO}
14286 @cindex load symbols from memory
14287 @item add-symbol-file-from-memory @var{address}
14288 Load symbols from the given @var{address} in a dynamically loaded
14289 object file whose image is mapped directly into the inferior's memory.
14290 For example, the Linux kernel maps a @code{syscall DSO} into each
14291 process's address space; this DSO provides kernel-specific code for
14292 some system calls. The argument can be any expression whose
14293 evaluation yields the address of the file's shared object file header.
14294 For this command to work, you must have used @code{symbol-file} or
14295 @code{exec-file} commands in advance.
14297 @kindex add-shared-symbol-files
14299 @item add-shared-symbol-files @var{library-file}
14300 @itemx assf @var{library-file}
14301 The @code{add-shared-symbol-files} command can currently be used only
14302 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14303 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14304 @value{GDBN} automatically looks for shared libraries, however if
14305 @value{GDBN} does not find yours, you can invoke
14306 @code{add-shared-symbol-files}. It takes one argument: the shared
14307 library's file name. @code{assf} is a shorthand alias for
14308 @code{add-shared-symbol-files}.
14311 @item section @var{section} @var{addr}
14312 The @code{section} command changes the base address of the named
14313 @var{section} of the exec file to @var{addr}. This can be used if the
14314 exec file does not contain section addresses, (such as in the
14315 @code{a.out} format), or when the addresses specified in the file
14316 itself are wrong. Each section must be changed separately. The
14317 @code{info files} command, described below, lists all the sections and
14321 @kindex info target
14324 @code{info files} and @code{info target} are synonymous; both print the
14325 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14326 including the names of the executable and core dump files currently in
14327 use by @value{GDBN}, and the files from which symbols were loaded. The
14328 command @code{help target} lists all possible targets rather than
14331 @kindex maint info sections
14332 @item maint info sections
14333 Another command that can give you extra information about program sections
14334 is @code{maint info sections}. In addition to the section information
14335 displayed by @code{info files}, this command displays the flags and file
14336 offset of each section in the executable and core dump files. In addition,
14337 @code{maint info sections} provides the following command options (which
14338 may be arbitrarily combined):
14342 Display sections for all loaded object files, including shared libraries.
14343 @item @var{sections}
14344 Display info only for named @var{sections}.
14345 @item @var{section-flags}
14346 Display info only for sections for which @var{section-flags} are true.
14347 The section flags that @value{GDBN} currently knows about are:
14350 Section will have space allocated in the process when loaded.
14351 Set for all sections except those containing debug information.
14353 Section will be loaded from the file into the child process memory.
14354 Set for pre-initialized code and data, clear for @code{.bss} sections.
14356 Section needs to be relocated before loading.
14358 Section cannot be modified by the child process.
14360 Section contains executable code only.
14362 Section contains data only (no executable code).
14364 Section will reside in ROM.
14366 Section contains data for constructor/destructor lists.
14368 Section is not empty.
14370 An instruction to the linker to not output the section.
14371 @item COFF_SHARED_LIBRARY
14372 A notification to the linker that the section contains
14373 COFF shared library information.
14375 Section contains common symbols.
14378 @kindex set trust-readonly-sections
14379 @cindex read-only sections
14380 @item set trust-readonly-sections on
14381 Tell @value{GDBN} that readonly sections in your object file
14382 really are read-only (i.e.@: that their contents will not change).
14383 In that case, @value{GDBN} can fetch values from these sections
14384 out of the object file, rather than from the target program.
14385 For some targets (notably embedded ones), this can be a significant
14386 enhancement to debugging performance.
14388 The default is off.
14390 @item set trust-readonly-sections off
14391 Tell @value{GDBN} not to trust readonly sections. This means that
14392 the contents of the section might change while the program is running,
14393 and must therefore be fetched from the target when needed.
14395 @item show trust-readonly-sections
14396 Show the current setting of trusting readonly sections.
14399 All file-specifying commands allow both absolute and relative file names
14400 as arguments. @value{GDBN} always converts the file name to an absolute file
14401 name and remembers it that way.
14403 @cindex shared libraries
14404 @anchor{Shared Libraries}
14405 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14406 and IBM RS/6000 AIX shared libraries.
14408 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14409 shared libraries. @xref{Expat}.
14411 @value{GDBN} automatically loads symbol definitions from shared libraries
14412 when you use the @code{run} command, or when you examine a core file.
14413 (Before you issue the @code{run} command, @value{GDBN} does not understand
14414 references to a function in a shared library, however---unless you are
14415 debugging a core file).
14417 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14418 automatically loads the symbols at the time of the @code{shl_load} call.
14420 @c FIXME: some @value{GDBN} release may permit some refs to undef
14421 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14422 @c FIXME...lib; check this from time to time when updating manual
14424 There are times, however, when you may wish to not automatically load
14425 symbol definitions from shared libraries, such as when they are
14426 particularly large or there are many of them.
14428 To control the automatic loading of shared library symbols, use the
14432 @kindex set auto-solib-add
14433 @item set auto-solib-add @var{mode}
14434 If @var{mode} is @code{on}, symbols from all shared object libraries
14435 will be loaded automatically when the inferior begins execution, you
14436 attach to an independently started inferior, or when the dynamic linker
14437 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14438 is @code{off}, symbols must be loaded manually, using the
14439 @code{sharedlibrary} command. The default value is @code{on}.
14441 @cindex memory used for symbol tables
14442 If your program uses lots of shared libraries with debug info that
14443 takes large amounts of memory, you can decrease the @value{GDBN}
14444 memory footprint by preventing it from automatically loading the
14445 symbols from shared libraries. To that end, type @kbd{set
14446 auto-solib-add off} before running the inferior, then load each
14447 library whose debug symbols you do need with @kbd{sharedlibrary
14448 @var{regexp}}, where @var{regexp} is a regular expression that matches
14449 the libraries whose symbols you want to be loaded.
14451 @kindex show auto-solib-add
14452 @item show auto-solib-add
14453 Display the current autoloading mode.
14456 @cindex load shared library
14457 To explicitly load shared library symbols, use the @code{sharedlibrary}
14461 @kindex info sharedlibrary
14463 @item info share @var{regex}
14464 @itemx info sharedlibrary @var{regex}
14465 Print the names of the shared libraries which are currently loaded
14466 that match @var{regex}. If @var{regex} is omitted then print
14467 all shared libraries that are loaded.
14469 @kindex sharedlibrary
14471 @item sharedlibrary @var{regex}
14472 @itemx share @var{regex}
14473 Load shared object library symbols for files matching a
14474 Unix regular expression.
14475 As with files loaded automatically, it only loads shared libraries
14476 required by your program for a core file or after typing @code{run}. If
14477 @var{regex} is omitted all shared libraries required by your program are
14480 @item nosharedlibrary
14481 @kindex nosharedlibrary
14482 @cindex unload symbols from shared libraries
14483 Unload all shared object library symbols. This discards all symbols
14484 that have been loaded from all shared libraries. Symbols from shared
14485 libraries that were loaded by explicit user requests are not
14489 Sometimes you may wish that @value{GDBN} stops and gives you control
14490 when any of shared library events happen. Use the @code{set
14491 stop-on-solib-events} command for this:
14494 @item set stop-on-solib-events
14495 @kindex set stop-on-solib-events
14496 This command controls whether @value{GDBN} should give you control
14497 when the dynamic linker notifies it about some shared library event.
14498 The most common event of interest is loading or unloading of a new
14501 @item show stop-on-solib-events
14502 @kindex show stop-on-solib-events
14503 Show whether @value{GDBN} stops and gives you control when shared
14504 library events happen.
14507 Shared libraries are also supported in many cross or remote debugging
14508 configurations. @value{GDBN} needs to have access to the target's libraries;
14509 this can be accomplished either by providing copies of the libraries
14510 on the host system, or by asking @value{GDBN} to automatically retrieve the
14511 libraries from the target. If copies of the target libraries are
14512 provided, they need to be the same as the target libraries, although the
14513 copies on the target can be stripped as long as the copies on the host are
14516 @cindex where to look for shared libraries
14517 For remote debugging, you need to tell @value{GDBN} where the target
14518 libraries are, so that it can load the correct copies---otherwise, it
14519 may try to load the host's libraries. @value{GDBN} has two variables
14520 to specify the search directories for target libraries.
14523 @cindex prefix for shared library file names
14524 @cindex system root, alternate
14525 @kindex set solib-absolute-prefix
14526 @kindex set sysroot
14527 @item set sysroot @var{path}
14528 Use @var{path} as the system root for the program being debugged. Any
14529 absolute shared library paths will be prefixed with @var{path}; many
14530 runtime loaders store the absolute paths to the shared library in the
14531 target program's memory. If you use @code{set sysroot} to find shared
14532 libraries, they need to be laid out in the same way that they are on
14533 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14536 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14537 retrieve the target libraries from the remote system. This is only
14538 supported when using a remote target that supports the @code{remote get}
14539 command (@pxref{File Transfer,,Sending files to a remote system}).
14540 The part of @var{path} following the initial @file{remote:}
14541 (if present) is used as system root prefix on the remote file system.
14542 @footnote{If you want to specify a local system root using a directory
14543 that happens to be named @file{remote:}, you need to use some equivalent
14544 variant of the name like @file{./remote:}.}
14546 For targets with an MS-DOS based filesystem, such as MS-Windows and
14547 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14548 absolute file name with @var{path}. But first, on Unix hosts,
14549 @value{GDBN} converts all backslash directory separators into forward
14550 slashes, because the backslash is not a directory separator on Unix:
14553 c:\foo\bar.dll @result{} c:/foo/bar.dll
14556 Then, @value{GDBN} attempts prefixing the target file name with
14557 @var{path}, and looks for the resulting file name in the host file
14561 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14564 If that does not find the shared library, @value{GDBN} tries removing
14565 the @samp{:} character from the drive spec, both for convenience, and,
14566 for the case of the host file system not supporting file names with
14570 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14573 This makes it possible to have a system root that mirrors a target
14574 with more than one drive. E.g., you may want to setup your local
14575 copies of the target system shared libraries like so (note @samp{c} vs
14579 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14580 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14581 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14585 and point the system root at @file{/path/to/sysroot}, so that
14586 @value{GDBN} can find the correct copies of both
14587 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14589 If that still does not find the shared library, @value{GDBN} tries
14590 removing the whole drive spec from the target file name:
14593 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14596 This last lookup makes it possible to not care about the drive name,
14597 if you don't want or need to.
14599 The @code{set solib-absolute-prefix} command is an alias for @code{set
14602 @cindex default system root
14603 @cindex @samp{--with-sysroot}
14604 You can set the default system root by using the configure-time
14605 @samp{--with-sysroot} option. If the system root is inside
14606 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14607 @samp{--exec-prefix}), then the default system root will be updated
14608 automatically if the installed @value{GDBN} is moved to a new
14611 @kindex show sysroot
14613 Display the current shared library prefix.
14615 @kindex set solib-search-path
14616 @item set solib-search-path @var{path}
14617 If this variable is set, @var{path} is a colon-separated list of
14618 directories to search for shared libraries. @samp{solib-search-path}
14619 is used after @samp{sysroot} fails to locate the library, or if the
14620 path to the library is relative instead of absolute. If you want to
14621 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14622 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14623 finding your host's libraries. @samp{sysroot} is preferred; setting
14624 it to a nonexistent directory may interfere with automatic loading
14625 of shared library symbols.
14627 @kindex show solib-search-path
14628 @item show solib-search-path
14629 Display the current shared library search path.
14631 @cindex DOS file-name semantics of file names.
14632 @kindex set target-file-system-kind (unix|dos-based|auto)
14633 @kindex show target-file-system-kind
14634 @item set target-file-system-kind @var{kind}
14635 Set assumed file system kind for target reported file names.
14637 Shared library file names as reported by the target system may not
14638 make sense as is on the system @value{GDBN} is running on. For
14639 example, when remote debugging a target that has MS-DOS based file
14640 system semantics, from a Unix host, the target may be reporting to
14641 @value{GDBN} a list of loaded shared libraries with file names such as
14642 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14643 drive letters, so the @samp{c:\} prefix is not normally understood as
14644 indicating an absolute file name, and neither is the backslash
14645 normally considered a directory separator character. In that case,
14646 the native file system would interpret this whole absolute file name
14647 as a relative file name with no directory components. This would make
14648 it impossible to point @value{GDBN} at a copy of the remote target's
14649 shared libraries on the host using @code{set sysroot}, and impractical
14650 with @code{set solib-search-path}. Setting
14651 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14652 to interpret such file names similarly to how the target would, and to
14653 map them to file names valid on @value{GDBN}'s native file system
14654 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14655 to one of the supported file system kinds. In that case, @value{GDBN}
14656 tries to determine the appropriate file system variant based on the
14657 current target's operating system (@pxref{ABI, ,Configuring the
14658 Current ABI}). The supported file system settings are:
14662 Instruct @value{GDBN} to assume the target file system is of Unix
14663 kind. Only file names starting the forward slash (@samp{/}) character
14664 are considered absolute, and the directory separator character is also
14668 Instruct @value{GDBN} to assume the target file system is DOS based.
14669 File names starting with either a forward slash, or a drive letter
14670 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14671 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14672 considered directory separators.
14675 Instruct @value{GDBN} to use the file system kind associated with the
14676 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14677 This is the default.
14682 @node Separate Debug Files
14683 @section Debugging Information in Separate Files
14684 @cindex separate debugging information files
14685 @cindex debugging information in separate files
14686 @cindex @file{.debug} subdirectories
14687 @cindex debugging information directory, global
14688 @cindex global debugging information directory
14689 @cindex build ID, and separate debugging files
14690 @cindex @file{.build-id} directory
14692 @value{GDBN} allows you to put a program's debugging information in a
14693 file separate from the executable itself, in a way that allows
14694 @value{GDBN} to find and load the debugging information automatically.
14695 Since debugging information can be very large---sometimes larger
14696 than the executable code itself---some systems distribute debugging
14697 information for their executables in separate files, which users can
14698 install only when they need to debug a problem.
14700 @value{GDBN} supports two ways of specifying the separate debug info
14705 The executable contains a @dfn{debug link} that specifies the name of
14706 the separate debug info file. The separate debug file's name is
14707 usually @file{@var{executable}.debug}, where @var{executable} is the
14708 name of the corresponding executable file without leading directories
14709 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14710 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14711 checksum for the debug file, which @value{GDBN} uses to validate that
14712 the executable and the debug file came from the same build.
14715 The executable contains a @dfn{build ID}, a unique bit string that is
14716 also present in the corresponding debug info file. (This is supported
14717 only on some operating systems, notably those which use the ELF format
14718 for binary files and the @sc{gnu} Binutils.) For more details about
14719 this feature, see the description of the @option{--build-id}
14720 command-line option in @ref{Options, , Command Line Options, ld.info,
14721 The GNU Linker}. The debug info file's name is not specified
14722 explicitly by the build ID, but can be computed from the build ID, see
14726 Depending on the way the debug info file is specified, @value{GDBN}
14727 uses two different methods of looking for the debug file:
14731 For the ``debug link'' method, @value{GDBN} looks up the named file in
14732 the directory of the executable file, then in a subdirectory of that
14733 directory named @file{.debug}, and finally under the global debug
14734 directory, in a subdirectory whose name is identical to the leading
14735 directories of the executable's absolute file name.
14738 For the ``build ID'' method, @value{GDBN} looks in the
14739 @file{.build-id} subdirectory of the global debug directory for a file
14740 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14741 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14742 are the rest of the bit string. (Real build ID strings are 32 or more
14743 hex characters, not 10.)
14746 So, for example, suppose you ask @value{GDBN} to debug
14747 @file{/usr/bin/ls}, which has a debug link that specifies the
14748 file @file{ls.debug}, and a build ID whose value in hex is
14749 @code{abcdef1234}. If the global debug directory is
14750 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14751 debug information files, in the indicated order:
14755 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14757 @file{/usr/bin/ls.debug}
14759 @file{/usr/bin/.debug/ls.debug}
14761 @file{/usr/lib/debug/usr/bin/ls.debug}.
14764 You can set the global debugging info directory's name, and view the
14765 name @value{GDBN} is currently using.
14769 @kindex set debug-file-directory
14770 @item set debug-file-directory @var{directories}
14771 Set the directories which @value{GDBN} searches for separate debugging
14772 information files to @var{directory}. Multiple directory components can be set
14773 concatenating them by a directory separator.
14775 @kindex show debug-file-directory
14776 @item show debug-file-directory
14777 Show the directories @value{GDBN} searches for separate debugging
14782 @cindex @code{.gnu_debuglink} sections
14783 @cindex debug link sections
14784 A debug link is a special section of the executable file named
14785 @code{.gnu_debuglink}. The section must contain:
14789 A filename, with any leading directory components removed, followed by
14792 zero to three bytes of padding, as needed to reach the next four-byte
14793 boundary within the section, and
14795 a four-byte CRC checksum, stored in the same endianness used for the
14796 executable file itself. The checksum is computed on the debugging
14797 information file's full contents by the function given below, passing
14798 zero as the @var{crc} argument.
14801 Any executable file format can carry a debug link, as long as it can
14802 contain a section named @code{.gnu_debuglink} with the contents
14805 @cindex @code{.note.gnu.build-id} sections
14806 @cindex build ID sections
14807 The build ID is a special section in the executable file (and in other
14808 ELF binary files that @value{GDBN} may consider). This section is
14809 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14810 It contains unique identification for the built files---the ID remains
14811 the same across multiple builds of the same build tree. The default
14812 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14813 content for the build ID string. The same section with an identical
14814 value is present in the original built binary with symbols, in its
14815 stripped variant, and in the separate debugging information file.
14817 The debugging information file itself should be an ordinary
14818 executable, containing a full set of linker symbols, sections, and
14819 debugging information. The sections of the debugging information file
14820 should have the same names, addresses, and sizes as the original file,
14821 but they need not contain any data---much like a @code{.bss} section
14822 in an ordinary executable.
14824 The @sc{gnu} binary utilities (Binutils) package includes the
14825 @samp{objcopy} utility that can produce
14826 the separated executable / debugging information file pairs using the
14827 following commands:
14830 @kbd{objcopy --only-keep-debug foo foo.debug}
14835 These commands remove the debugging
14836 information from the executable file @file{foo} and place it in the file
14837 @file{foo.debug}. You can use the first, second or both methods to link the
14842 The debug link method needs the following additional command to also leave
14843 behind a debug link in @file{foo}:
14846 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14849 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14850 a version of the @code{strip} command such that the command @kbd{strip foo -f
14851 foo.debug} has the same functionality as the two @code{objcopy} commands and
14852 the @code{ln -s} command above, together.
14855 Build ID gets embedded into the main executable using @code{ld --build-id} or
14856 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14857 compatibility fixes for debug files separation are present in @sc{gnu} binary
14858 utilities (Binutils) package since version 2.18.
14863 @cindex CRC algorithm definition
14864 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14865 IEEE 802.3 using the polynomial:
14867 @c TexInfo requires naked braces for multi-digit exponents for Tex
14868 @c output, but this causes HTML output to barf. HTML has to be set using
14869 @c raw commands. So we end up having to specify this equation in 2
14874 <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>
14875 + <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
14881 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14882 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14886 The function is computed byte at a time, taking the least
14887 significant bit of each byte first. The initial pattern
14888 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14889 the final result is inverted to ensure trailing zeros also affect the
14892 @emph{Note:} This is the same CRC polynomial as used in handling the
14893 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14894 , @value{GDBN} Remote Serial Protocol}). However in the
14895 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14896 significant bit first, and the result is not inverted, so trailing
14897 zeros have no effect on the CRC value.
14899 To complete the description, we show below the code of the function
14900 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14901 initially supplied @code{crc} argument means that an initial call to
14902 this function passing in zero will start computing the CRC using
14905 @kindex gnu_debuglink_crc32
14908 gnu_debuglink_crc32 (unsigned long crc,
14909 unsigned char *buf, size_t len)
14911 static const unsigned long crc32_table[256] =
14913 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14914 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14915 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14916 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14917 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14918 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14919 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14920 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14921 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14922 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14923 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14924 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14925 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14926 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14927 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14928 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14929 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14930 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14931 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14932 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14933 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14934 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14935 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14936 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14937 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14938 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14939 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14940 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14941 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14942 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14943 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14944 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14945 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14946 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14947 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14948 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14949 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14950 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14951 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14952 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14953 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14954 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14955 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14956 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14957 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14958 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14959 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14960 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14961 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14962 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14963 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14966 unsigned char *end;
14968 crc = ~crc & 0xffffffff;
14969 for (end = buf + len; buf < end; ++buf)
14970 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14971 return ~crc & 0xffffffff;
14976 This computation does not apply to the ``build ID'' method.
14979 @node Symbol Errors
14980 @section Errors Reading Symbol Files
14982 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14983 such as symbol types it does not recognize, or known bugs in compiler
14984 output. By default, @value{GDBN} does not notify you of such problems, since
14985 they are relatively common and primarily of interest to people
14986 debugging compilers. If you are interested in seeing information
14987 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14988 only one message about each such type of problem, no matter how many
14989 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14990 to see how many times the problems occur, with the @code{set
14991 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14994 The messages currently printed, and their meanings, include:
14997 @item inner block not inside outer block in @var{symbol}
14999 The symbol information shows where symbol scopes begin and end
15000 (such as at the start of a function or a block of statements). This
15001 error indicates that an inner scope block is not fully contained
15002 in its outer scope blocks.
15004 @value{GDBN} circumvents the problem by treating the inner block as if it had
15005 the same scope as the outer block. In the error message, @var{symbol}
15006 may be shown as ``@code{(don't know)}'' if the outer block is not a
15009 @item block at @var{address} out of order
15011 The symbol information for symbol scope blocks should occur in
15012 order of increasing addresses. This error indicates that it does not
15015 @value{GDBN} does not circumvent this problem, and has trouble
15016 locating symbols in the source file whose symbols it is reading. (You
15017 can often determine what source file is affected by specifying
15018 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15021 @item bad block start address patched
15023 The symbol information for a symbol scope block has a start address
15024 smaller than the address of the preceding source line. This is known
15025 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15027 @value{GDBN} circumvents the problem by treating the symbol scope block as
15028 starting on the previous source line.
15030 @item bad string table offset in symbol @var{n}
15033 Symbol number @var{n} contains a pointer into the string table which is
15034 larger than the size of the string table.
15036 @value{GDBN} circumvents the problem by considering the symbol to have the
15037 name @code{foo}, which may cause other problems if many symbols end up
15040 @item unknown symbol type @code{0x@var{nn}}
15042 The symbol information contains new data types that @value{GDBN} does
15043 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15044 uncomprehended information, in hexadecimal.
15046 @value{GDBN} circumvents the error by ignoring this symbol information.
15047 This usually allows you to debug your program, though certain symbols
15048 are not accessible. If you encounter such a problem and feel like
15049 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15050 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15051 and examine @code{*bufp} to see the symbol.
15053 @item stub type has NULL name
15055 @value{GDBN} could not find the full definition for a struct or class.
15057 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15058 The symbol information for a C@t{++} member function is missing some
15059 information that recent versions of the compiler should have output for
15062 @item info mismatch between compiler and debugger
15064 @value{GDBN} could not parse a type specification output by the compiler.
15069 @section GDB Data Files
15071 @cindex prefix for data files
15072 @value{GDBN} will sometimes read an auxiliary data file. These files
15073 are kept in a directory known as the @dfn{data directory}.
15075 You can set the data directory's name, and view the name @value{GDBN}
15076 is currently using.
15079 @kindex set data-directory
15080 @item set data-directory @var{directory}
15081 Set the directory which @value{GDBN} searches for auxiliary data files
15082 to @var{directory}.
15084 @kindex show data-directory
15085 @item show data-directory
15086 Show the directory @value{GDBN} searches for auxiliary data files.
15089 @cindex default data directory
15090 @cindex @samp{--with-gdb-datadir}
15091 You can set the default data directory by using the configure-time
15092 @samp{--with-gdb-datadir} option. If the data directory is inside
15093 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15094 @samp{--exec-prefix}), then the default data directory will be updated
15095 automatically if the installed @value{GDBN} is moved to a new
15099 @chapter Specifying a Debugging Target
15101 @cindex debugging target
15102 A @dfn{target} is the execution environment occupied by your program.
15104 Often, @value{GDBN} runs in the same host environment as your program;
15105 in that case, the debugging target is specified as a side effect when
15106 you use the @code{file} or @code{core} commands. When you need more
15107 flexibility---for example, running @value{GDBN} on a physically separate
15108 host, or controlling a standalone system over a serial port or a
15109 realtime system over a TCP/IP connection---you can use the @code{target}
15110 command to specify one of the target types configured for @value{GDBN}
15111 (@pxref{Target Commands, ,Commands for Managing Targets}).
15113 @cindex target architecture
15114 It is possible to build @value{GDBN} for several different @dfn{target
15115 architectures}. When @value{GDBN} is built like that, you can choose
15116 one of the available architectures with the @kbd{set architecture}
15120 @kindex set architecture
15121 @kindex show architecture
15122 @item set architecture @var{arch}
15123 This command sets the current target architecture to @var{arch}. The
15124 value of @var{arch} can be @code{"auto"}, in addition to one of the
15125 supported architectures.
15127 @item show architecture
15128 Show the current target architecture.
15130 @item set processor
15132 @kindex set processor
15133 @kindex show processor
15134 These are alias commands for, respectively, @code{set architecture}
15135 and @code{show architecture}.
15139 * Active Targets:: Active targets
15140 * Target Commands:: Commands for managing targets
15141 * Byte Order:: Choosing target byte order
15144 @node Active Targets
15145 @section Active Targets
15147 @cindex stacking targets
15148 @cindex active targets
15149 @cindex multiple targets
15151 There are three classes of targets: processes, core files, and
15152 executable files. @value{GDBN} can work concurrently on up to three
15153 active targets, one in each class. This allows you to (for example)
15154 start a process and inspect its activity without abandoning your work on
15157 For example, if you execute @samp{gdb a.out}, then the executable file
15158 @code{a.out} is the only active target. If you designate a core file as
15159 well---presumably from a prior run that crashed and coredumped---then
15160 @value{GDBN} has two active targets and uses them in tandem, looking
15161 first in the corefile target, then in the executable file, to satisfy
15162 requests for memory addresses. (Typically, these two classes of target
15163 are complementary, since core files contain only a program's
15164 read-write memory---variables and so on---plus machine status, while
15165 executable files contain only the program text and initialized data.)
15167 When you type @code{run}, your executable file becomes an active process
15168 target as well. When a process target is active, all @value{GDBN}
15169 commands requesting memory addresses refer to that target; addresses in
15170 an active core file or executable file target are obscured while the
15171 process target is active.
15173 Use the @code{core-file} and @code{exec-file} commands to select a new
15174 core file or executable target (@pxref{Files, ,Commands to Specify
15175 Files}). To specify as a target a process that is already running, use
15176 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15179 @node Target Commands
15180 @section Commands for Managing Targets
15183 @item target @var{type} @var{parameters}
15184 Connects the @value{GDBN} host environment to a target machine or
15185 process. A target is typically a protocol for talking to debugging
15186 facilities. You use the argument @var{type} to specify the type or
15187 protocol of the target machine.
15189 Further @var{parameters} are interpreted by the target protocol, but
15190 typically include things like device names or host names to connect
15191 with, process numbers, and baud rates.
15193 The @code{target} command does not repeat if you press @key{RET} again
15194 after executing the command.
15196 @kindex help target
15198 Displays the names of all targets available. To display targets
15199 currently selected, use either @code{info target} or @code{info files}
15200 (@pxref{Files, ,Commands to Specify Files}).
15202 @item help target @var{name}
15203 Describe a particular target, including any parameters necessary to
15206 @kindex set gnutarget
15207 @item set gnutarget @var{args}
15208 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15209 knows whether it is reading an @dfn{executable},
15210 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15211 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15212 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15215 @emph{Warning:} To specify a file format with @code{set gnutarget},
15216 you must know the actual BFD name.
15220 @xref{Files, , Commands to Specify Files}.
15222 @kindex show gnutarget
15223 @item show gnutarget
15224 Use the @code{show gnutarget} command to display what file format
15225 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15226 @value{GDBN} will determine the file format for each file automatically,
15227 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15230 @cindex common targets
15231 Here are some common targets (available, or not, depending on the GDB
15236 @item target exec @var{program}
15237 @cindex executable file target
15238 An executable file. @samp{target exec @var{program}} is the same as
15239 @samp{exec-file @var{program}}.
15241 @item target core @var{filename}
15242 @cindex core dump file target
15243 A core dump file. @samp{target core @var{filename}} is the same as
15244 @samp{core-file @var{filename}}.
15246 @item target remote @var{medium}
15247 @cindex remote target
15248 A remote system connected to @value{GDBN} via a serial line or network
15249 connection. This command tells @value{GDBN} to use its own remote
15250 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15252 For example, if you have a board connected to @file{/dev/ttya} on the
15253 machine running @value{GDBN}, you could say:
15256 target remote /dev/ttya
15259 @code{target remote} supports the @code{load} command. This is only
15260 useful if you have some other way of getting the stub to the target
15261 system, and you can put it somewhere in memory where it won't get
15262 clobbered by the download.
15264 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15265 @cindex built-in simulator target
15266 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15274 works; however, you cannot assume that a specific memory map, device
15275 drivers, or even basic I/O is available, although some simulators do
15276 provide these. For info about any processor-specific simulator details,
15277 see the appropriate section in @ref{Embedded Processors, ,Embedded
15282 Some configurations may include these targets as well:
15286 @item target nrom @var{dev}
15287 @cindex NetROM ROM emulator target
15288 NetROM ROM emulator. This target only supports downloading.
15292 Different targets are available on different configurations of @value{GDBN};
15293 your configuration may have more or fewer targets.
15295 Many remote targets require you to download the executable's code once
15296 you've successfully established a connection. You may wish to control
15297 various aspects of this process.
15302 @kindex set hash@r{, for remote monitors}
15303 @cindex hash mark while downloading
15304 This command controls whether a hash mark @samp{#} is displayed while
15305 downloading a file to the remote monitor. If on, a hash mark is
15306 displayed after each S-record is successfully downloaded to the
15310 @kindex show hash@r{, for remote monitors}
15311 Show the current status of displaying the hash mark.
15313 @item set debug monitor
15314 @kindex set debug monitor
15315 @cindex display remote monitor communications
15316 Enable or disable display of communications messages between
15317 @value{GDBN} and the remote monitor.
15319 @item show debug monitor
15320 @kindex show debug monitor
15321 Show the current status of displaying communications between
15322 @value{GDBN} and the remote monitor.
15327 @kindex load @var{filename}
15328 @item load @var{filename}
15330 Depending on what remote debugging facilities are configured into
15331 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15332 is meant to make @var{filename} (an executable) available for debugging
15333 on the remote system---by downloading, or dynamic linking, for example.
15334 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15335 the @code{add-symbol-file} command.
15337 If your @value{GDBN} does not have a @code{load} command, attempting to
15338 execute it gets the error message ``@code{You can't do that when your
15339 target is @dots{}}''
15341 The file is loaded at whatever address is specified in the executable.
15342 For some object file formats, you can specify the load address when you
15343 link the program; for other formats, like a.out, the object file format
15344 specifies a fixed address.
15345 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15347 Depending on the remote side capabilities, @value{GDBN} may be able to
15348 load programs into flash memory.
15350 @code{load} does not repeat if you press @key{RET} again after using it.
15354 @section Choosing Target Byte Order
15356 @cindex choosing target byte order
15357 @cindex target byte order
15359 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15360 offer the ability to run either big-endian or little-endian byte
15361 orders. Usually the executable or symbol will include a bit to
15362 designate the endian-ness, and you will not need to worry about
15363 which to use. However, you may still find it useful to adjust
15364 @value{GDBN}'s idea of processor endian-ness manually.
15368 @item set endian big
15369 Instruct @value{GDBN} to assume the target is big-endian.
15371 @item set endian little
15372 Instruct @value{GDBN} to assume the target is little-endian.
15374 @item set endian auto
15375 Instruct @value{GDBN} to use the byte order associated with the
15379 Display @value{GDBN}'s current idea of the target byte order.
15383 Note that these commands merely adjust interpretation of symbolic
15384 data on the host, and that they have absolutely no effect on the
15388 @node Remote Debugging
15389 @chapter Debugging Remote Programs
15390 @cindex remote debugging
15392 If you are trying to debug a program running on a machine that cannot run
15393 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15394 For example, you might use remote debugging on an operating system kernel,
15395 or on a small system which does not have a general purpose operating system
15396 powerful enough to run a full-featured debugger.
15398 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15399 to make this work with particular debugging targets. In addition,
15400 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15401 but not specific to any particular target system) which you can use if you
15402 write the remote stubs---the code that runs on the remote system to
15403 communicate with @value{GDBN}.
15405 Other remote targets may be available in your
15406 configuration of @value{GDBN}; use @code{help target} to list them.
15409 * Connecting:: Connecting to a remote target
15410 * File Transfer:: Sending files to a remote system
15411 * Server:: Using the gdbserver program
15412 * Remote Configuration:: Remote configuration
15413 * Remote Stub:: Implementing a remote stub
15417 @section Connecting to a Remote Target
15419 On the @value{GDBN} host machine, you will need an unstripped copy of
15420 your program, since @value{GDBN} needs symbol and debugging information.
15421 Start up @value{GDBN} as usual, using the name of the local copy of your
15422 program as the first argument.
15424 @cindex @code{target remote}
15425 @value{GDBN} can communicate with the target over a serial line, or
15426 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15427 each case, @value{GDBN} uses the same protocol for debugging your
15428 program; only the medium carrying the debugging packets varies. The
15429 @code{target remote} command establishes a connection to the target.
15430 Its arguments indicate which medium to use:
15434 @item target remote @var{serial-device}
15435 @cindex serial line, @code{target remote}
15436 Use @var{serial-device} to communicate with the target. For example,
15437 to use a serial line connected to the device named @file{/dev/ttyb}:
15440 target remote /dev/ttyb
15443 If you're using a serial line, you may want to give @value{GDBN} the
15444 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15445 (@pxref{Remote Configuration, set remotebaud}) before the
15446 @code{target} command.
15448 @item target remote @code{@var{host}:@var{port}}
15449 @itemx target remote @code{tcp:@var{host}:@var{port}}
15450 @cindex @acronym{TCP} port, @code{target remote}
15451 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15452 The @var{host} may be either a host name or a numeric @acronym{IP}
15453 address; @var{port} must be a decimal number. The @var{host} could be
15454 the target machine itself, if it is directly connected to the net, or
15455 it might be a terminal server which in turn has a serial line to the
15458 For example, to connect to port 2828 on a terminal server named
15462 target remote manyfarms:2828
15465 If your remote target is actually running on the same machine as your
15466 debugger session (e.g.@: a simulator for your target running on the
15467 same host), you can omit the hostname. For example, to connect to
15468 port 1234 on your local machine:
15471 target remote :1234
15475 Note that the colon is still required here.
15477 @item target remote @code{udp:@var{host}:@var{port}}
15478 @cindex @acronym{UDP} port, @code{target remote}
15479 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15480 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15483 target remote udp:manyfarms:2828
15486 When using a @acronym{UDP} connection for remote debugging, you should
15487 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15488 can silently drop packets on busy or unreliable networks, which will
15489 cause havoc with your debugging session.
15491 @item target remote | @var{command}
15492 @cindex pipe, @code{target remote} to
15493 Run @var{command} in the background and communicate with it using a
15494 pipe. The @var{command} is a shell command, to be parsed and expanded
15495 by the system's command shell, @code{/bin/sh}; it should expect remote
15496 protocol packets on its standard input, and send replies on its
15497 standard output. You could use this to run a stand-alone simulator
15498 that speaks the remote debugging protocol, to make net connections
15499 using programs like @code{ssh}, or for other similar tricks.
15501 If @var{command} closes its standard output (perhaps by exiting),
15502 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15503 program has already exited, this will have no effect.)
15507 Once the connection has been established, you can use all the usual
15508 commands to examine and change data. The remote program is already
15509 running; you can use @kbd{step} and @kbd{continue}, and you do not
15510 need to use @kbd{run}.
15512 @cindex interrupting remote programs
15513 @cindex remote programs, interrupting
15514 Whenever @value{GDBN} is waiting for the remote program, if you type the
15515 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15516 program. This may or may not succeed, depending in part on the hardware
15517 and the serial drivers the remote system uses. If you type the
15518 interrupt character once again, @value{GDBN} displays this prompt:
15521 Interrupted while waiting for the program.
15522 Give up (and stop debugging it)? (y or n)
15525 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15526 (If you decide you want to try again later, you can use @samp{target
15527 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15528 goes back to waiting.
15531 @kindex detach (remote)
15533 When you have finished debugging the remote program, you can use the
15534 @code{detach} command to release it from @value{GDBN} control.
15535 Detaching from the target normally resumes its execution, but the results
15536 will depend on your particular remote stub. After the @code{detach}
15537 command, @value{GDBN} is free to connect to another target.
15541 The @code{disconnect} command behaves like @code{detach}, except that
15542 the target is generally not resumed. It will wait for @value{GDBN}
15543 (this instance or another one) to connect and continue debugging. After
15544 the @code{disconnect} command, @value{GDBN} is again free to connect to
15547 @cindex send command to remote monitor
15548 @cindex extend @value{GDBN} for remote targets
15549 @cindex add new commands for external monitor
15551 @item monitor @var{cmd}
15552 This command allows you to send arbitrary commands directly to the
15553 remote monitor. Since @value{GDBN} doesn't care about the commands it
15554 sends like this, this command is the way to extend @value{GDBN}---you
15555 can add new commands that only the external monitor will understand
15559 @node File Transfer
15560 @section Sending files to a remote system
15561 @cindex remote target, file transfer
15562 @cindex file transfer
15563 @cindex sending files to remote systems
15565 Some remote targets offer the ability to transfer files over the same
15566 connection used to communicate with @value{GDBN}. This is convenient
15567 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15568 running @code{gdbserver} over a network interface. For other targets,
15569 e.g.@: embedded devices with only a single serial port, this may be
15570 the only way to upload or download files.
15572 Not all remote targets support these commands.
15576 @item remote put @var{hostfile} @var{targetfile}
15577 Copy file @var{hostfile} from the host system (the machine running
15578 @value{GDBN}) to @var{targetfile} on the target system.
15581 @item remote get @var{targetfile} @var{hostfile}
15582 Copy file @var{targetfile} from the target system to @var{hostfile}
15583 on the host system.
15585 @kindex remote delete
15586 @item remote delete @var{targetfile}
15587 Delete @var{targetfile} from the target system.
15592 @section Using the @code{gdbserver} Program
15595 @cindex remote connection without stubs
15596 @code{gdbserver} is a control program for Unix-like systems, which
15597 allows you to connect your program with a remote @value{GDBN} via
15598 @code{target remote}---but without linking in the usual debugging stub.
15600 @code{gdbserver} is not a complete replacement for the debugging stubs,
15601 because it requires essentially the same operating-system facilities
15602 that @value{GDBN} itself does. In fact, a system that can run
15603 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15604 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15605 because it is a much smaller program than @value{GDBN} itself. It is
15606 also easier to port than all of @value{GDBN}, so you may be able to get
15607 started more quickly on a new system by using @code{gdbserver}.
15608 Finally, if you develop code for real-time systems, you may find that
15609 the tradeoffs involved in real-time operation make it more convenient to
15610 do as much development work as possible on another system, for example
15611 by cross-compiling. You can use @code{gdbserver} to make a similar
15612 choice for debugging.
15614 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15615 or a TCP connection, using the standard @value{GDBN} remote serial
15619 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15620 Do not run @code{gdbserver} connected to any public network; a
15621 @value{GDBN} connection to @code{gdbserver} provides access to the
15622 target system with the same privileges as the user running
15626 @subsection Running @code{gdbserver}
15627 @cindex arguments, to @code{gdbserver}
15629 Run @code{gdbserver} on the target system. You need a copy of the
15630 program you want to debug, including any libraries it requires.
15631 @code{gdbserver} does not need your program's symbol table, so you can
15632 strip the program if necessary to save space. @value{GDBN} on the host
15633 system does all the symbol handling.
15635 To use the server, you must tell it how to communicate with @value{GDBN};
15636 the name of your program; and the arguments for your program. The usual
15640 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15643 @var{comm} is either a device name (to use a serial line) or a TCP
15644 hostname and portnumber. For example, to debug Emacs with the argument
15645 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15649 target> gdbserver /dev/com1 emacs foo.txt
15652 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15655 To use a TCP connection instead of a serial line:
15658 target> gdbserver host:2345 emacs foo.txt
15661 The only difference from the previous example is the first argument,
15662 specifying that you are communicating with the host @value{GDBN} via
15663 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15664 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15665 (Currently, the @samp{host} part is ignored.) You can choose any number
15666 you want for the port number as long as it does not conflict with any
15667 TCP ports already in use on the target system (for example, @code{23} is
15668 reserved for @code{telnet}).@footnote{If you choose a port number that
15669 conflicts with another service, @code{gdbserver} prints an error message
15670 and exits.} You must use the same port number with the host @value{GDBN}
15671 @code{target remote} command.
15673 @subsubsection Attaching to a Running Program
15675 On some targets, @code{gdbserver} can also attach to running programs.
15676 This is accomplished via the @code{--attach} argument. The syntax is:
15679 target> gdbserver --attach @var{comm} @var{pid}
15682 @var{pid} is the process ID of a currently running process. It isn't necessary
15683 to point @code{gdbserver} at a binary for the running process.
15686 @cindex attach to a program by name
15687 You can debug processes by name instead of process ID if your target has the
15688 @code{pidof} utility:
15691 target> gdbserver --attach @var{comm} `pidof @var{program}`
15694 In case more than one copy of @var{program} is running, or @var{program}
15695 has multiple threads, most versions of @code{pidof} support the
15696 @code{-s} option to only return the first process ID.
15698 @subsubsection Multi-Process Mode for @code{gdbserver}
15699 @cindex gdbserver, multiple processes
15700 @cindex multiple processes with gdbserver
15702 When you connect to @code{gdbserver} using @code{target remote},
15703 @code{gdbserver} debugs the specified program only once. When the
15704 program exits, or you detach from it, @value{GDBN} closes the connection
15705 and @code{gdbserver} exits.
15707 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15708 enters multi-process mode. When the debugged program exits, or you
15709 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15710 though no program is running. The @code{run} and @code{attach}
15711 commands instruct @code{gdbserver} to run or attach to a new program.
15712 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15713 remote exec-file}) to select the program to run. Command line
15714 arguments are supported, except for wildcard expansion and I/O
15715 redirection (@pxref{Arguments}).
15717 To start @code{gdbserver} without supplying an initial command to run
15718 or process ID to attach, use the @option{--multi} command line option.
15719 Then you can connect using @kbd{target extended-remote} and start
15720 the program you want to debug.
15722 @code{gdbserver} does not automatically exit in multi-process mode.
15723 You can terminate it by using @code{monitor exit}
15724 (@pxref{Monitor Commands for gdbserver}).
15726 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15728 The @option{--debug} option tells @code{gdbserver} to display extra
15729 status information about the debugging process. The
15730 @option{--remote-debug} option tells @code{gdbserver} to display
15731 remote protocol debug output. These options are intended for
15732 @code{gdbserver} development and for bug reports to the developers.
15734 The @option{--wrapper} option specifies a wrapper to launch programs
15735 for debugging. The option should be followed by the name of the
15736 wrapper, then any command-line arguments to pass to the wrapper, then
15737 @kbd{--} indicating the end of the wrapper arguments.
15739 @code{gdbserver} runs the specified wrapper program with a combined
15740 command line including the wrapper arguments, then the name of the
15741 program to debug, then any arguments to the program. The wrapper
15742 runs until it executes your program, and then @value{GDBN} gains control.
15744 You can use any program that eventually calls @code{execve} with
15745 its arguments as a wrapper. Several standard Unix utilities do
15746 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15747 with @code{exec "$@@"} will also work.
15749 For example, you can use @code{env} to pass an environment variable to
15750 the debugged program, without setting the variable in @code{gdbserver}'s
15754 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15757 @subsection Connecting to @code{gdbserver}
15759 Run @value{GDBN} on the host system.
15761 First make sure you have the necessary symbol files. Load symbols for
15762 your application using the @code{file} command before you connect. Use
15763 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15764 was compiled with the correct sysroot using @code{--with-sysroot}).
15766 The symbol file and target libraries must exactly match the executable
15767 and libraries on the target, with one exception: the files on the host
15768 system should not be stripped, even if the files on the target system
15769 are. Mismatched or missing files will lead to confusing results
15770 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15771 files may also prevent @code{gdbserver} from debugging multi-threaded
15774 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15775 For TCP connections, you must start up @code{gdbserver} prior to using
15776 the @code{target remote} command. Otherwise you may get an error whose
15777 text depends on the host system, but which usually looks something like
15778 @samp{Connection refused}. Don't use the @code{load}
15779 command in @value{GDBN} when using @code{gdbserver}, since the program is
15780 already on the target.
15782 @subsection Monitor Commands for @code{gdbserver}
15783 @cindex monitor commands, for @code{gdbserver}
15784 @anchor{Monitor Commands for gdbserver}
15786 During a @value{GDBN} session using @code{gdbserver}, you can use the
15787 @code{monitor} command to send special requests to @code{gdbserver}.
15788 Here are the available commands.
15792 List the available monitor commands.
15794 @item monitor set debug 0
15795 @itemx monitor set debug 1
15796 Disable or enable general debugging messages.
15798 @item monitor set remote-debug 0
15799 @itemx monitor set remote-debug 1
15800 Disable or enable specific debugging messages associated with the remote
15801 protocol (@pxref{Remote Protocol}).
15803 @item monitor set libthread-db-search-path [PATH]
15804 @cindex gdbserver, search path for @code{libthread_db}
15805 When this command is issued, @var{path} is a colon-separated list of
15806 directories to search for @code{libthread_db} (@pxref{Threads,,set
15807 libthread-db-search-path}). If you omit @var{path},
15808 @samp{libthread-db-search-path} will be reset to an empty list.
15811 Tell gdbserver to exit immediately. This command should be followed by
15812 @code{disconnect} to close the debugging session. @code{gdbserver} will
15813 detach from any attached processes and kill any processes it created.
15814 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15815 of a multi-process mode debug session.
15819 @subsection Tracepoints support in @code{gdbserver}
15820 @cindex tracepoints support in @code{gdbserver}
15822 On some targets, @code{gdbserver} supports tracepoints and fast
15825 For fast tracepoints to work, a special library called the
15826 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
15827 This library is built and distributed as an integral part of
15830 There are several ways to load the in-process agent in your program:
15833 @item Specifying it as dependency at link time
15835 You can link your program dynamically with the in-process agent
15836 library. On most systems, this is accomplished by adding
15837 @code{-linproctrace} to the link command.
15839 @item Using the system's preloading mechanisms
15841 You can force loading the in-process agent at startup time by using
15842 your system's support for preloading shared libraries. Many Unixes
15843 support the concept of preloading user defined libraries. In most
15844 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
15845 in the environment. See also the description of @code{gdbserver}'s
15846 @option{--wrapper} command line option.
15848 @item Using @value{GDBN} to force loading the agent at run time
15850 On some systems, you can force the inferior to load a shared library,
15851 by calling a dynamic loader function in the inferior that takes care
15852 of dynamically looking up and loading a shared library. On most Unix
15853 systems, the function is @code{dlopen}. You'll use the @code{call}
15854 command for that. For example:
15857 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
15860 Note that on most Unix systems, for the @code{dlopen} function to be
15861 available, the program needs to be linked with @code{-ldl}.
15864 On systems that have a userspace dynamic loader, like most Unix
15865 systems, when you connect to @code{gdbserver} using @code{target
15866 remote}, you'll find that the program is stopped at the dynamic
15867 loader's entry point, and no shared library has been loaded in the
15868 program's address space yet, including the in-process agent. In that
15869 case, before being able to use any of the fast tracepoints features,
15870 you need to let the loader run and load the shared libraries. The
15871 most simple way to do that is to run the program to the main
15872 procedure. E.g., if debugging a C or C@t{++} program, start
15873 @code{gdbserver} like so:
15876 $ gdbserver :9999 myprogram
15879 Start GDB and connect to @code{gdbserver} like so, and run to main:
15883 (@value{GDBP}) target remote myhost:9999
15884 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
15885 (@value{GDBP}) b main
15886 (@value{GDBP}) continue
15889 The in-process tracing agent library should now be loaded into the
15890 process; you can confirm it with the @code{info sharedlibrary}
15891 command, which will list @file{libinproctrace.so} as loaded in the
15892 process. You are now ready to install fast tracepoints and start
15895 @node Remote Configuration
15896 @section Remote Configuration
15899 @kindex show remote
15900 This section documents the configuration options available when
15901 debugging remote programs. For the options related to the File I/O
15902 extensions of the remote protocol, see @ref{system,
15903 system-call-allowed}.
15906 @item set remoteaddresssize @var{bits}
15907 @cindex address size for remote targets
15908 @cindex bits in remote address
15909 Set the maximum size of address in a memory packet to the specified
15910 number of bits. @value{GDBN} will mask off the address bits above
15911 that number, when it passes addresses to the remote target. The
15912 default value is the number of bits in the target's address.
15914 @item show remoteaddresssize
15915 Show the current value of remote address size in bits.
15917 @item set remotebaud @var{n}
15918 @cindex baud rate for remote targets
15919 Set the baud rate for the remote serial I/O to @var{n} baud. The
15920 value is used to set the speed of the serial port used for debugging
15923 @item show remotebaud
15924 Show the current speed of the remote connection.
15926 @item set remotebreak
15927 @cindex interrupt remote programs
15928 @cindex BREAK signal instead of Ctrl-C
15929 @anchor{set remotebreak}
15930 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15931 when you type @kbd{Ctrl-c} to interrupt the program running
15932 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15933 character instead. The default is off, since most remote systems
15934 expect to see @samp{Ctrl-C} as the interrupt signal.
15936 @item show remotebreak
15937 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15938 interrupt the remote program.
15940 @item set remoteflow on
15941 @itemx set remoteflow off
15942 @kindex set remoteflow
15943 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15944 on the serial port used to communicate to the remote target.
15946 @item show remoteflow
15947 @kindex show remoteflow
15948 Show the current setting of hardware flow control.
15950 @item set remotelogbase @var{base}
15951 Set the base (a.k.a.@: radix) of logging serial protocol
15952 communications to @var{base}. Supported values of @var{base} are:
15953 @code{ascii}, @code{octal}, and @code{hex}. The default is
15956 @item show remotelogbase
15957 Show the current setting of the radix for logging remote serial
15960 @item set remotelogfile @var{file}
15961 @cindex record serial communications on file
15962 Record remote serial communications on the named @var{file}. The
15963 default is not to record at all.
15965 @item show remotelogfile.
15966 Show the current setting of the file name on which to record the
15967 serial communications.
15969 @item set remotetimeout @var{num}
15970 @cindex timeout for serial communications
15971 @cindex remote timeout
15972 Set the timeout limit to wait for the remote target to respond to
15973 @var{num} seconds. The default is 2 seconds.
15975 @item show remotetimeout
15976 Show the current number of seconds to wait for the remote target
15979 @cindex limit hardware breakpoints and watchpoints
15980 @cindex remote target, limit break- and watchpoints
15981 @anchor{set remote hardware-watchpoint-limit}
15982 @anchor{set remote hardware-breakpoint-limit}
15983 @item set remote hardware-watchpoint-limit @var{limit}
15984 @itemx set remote hardware-breakpoint-limit @var{limit}
15985 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15986 watchpoints. A limit of -1, the default, is treated as unlimited.
15988 @item set remote exec-file @var{filename}
15989 @itemx show remote exec-file
15990 @anchor{set remote exec-file}
15991 @cindex executable file, for remote target
15992 Select the file used for @code{run} with @code{target
15993 extended-remote}. This should be set to a filename valid on the
15994 target system. If it is not set, the target will use a default
15995 filename (e.g.@: the last program run).
15997 @item set remote interrupt-sequence
15998 @cindex interrupt remote programs
15999 @cindex select Ctrl-C, BREAK or BREAK-g
16000 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16001 @samp{BREAK-g} as the
16002 sequence to the remote target in order to interrupt the execution.
16003 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16004 is high level of serial line for some certain time.
16005 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16006 It is @code{BREAK} signal followed by character @code{g}.
16008 @item show interrupt-sequence
16009 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16010 is sent by @value{GDBN} to interrupt the remote program.
16011 @code{BREAK-g} is BREAK signal followed by @code{g} and
16012 also known as Magic SysRq g.
16014 @item set remote interrupt-on-connect
16015 @cindex send interrupt-sequence on start
16016 Specify whether interrupt-sequence is sent to remote target when
16017 @value{GDBN} connects to it. This is mostly needed when you debug
16018 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16019 which is known as Magic SysRq g in order to connect @value{GDBN}.
16021 @item show interrupt-on-connect
16022 Show whether interrupt-sequence is sent
16023 to remote target when @value{GDBN} connects to it.
16027 @item set tcp auto-retry on
16028 @cindex auto-retry, for remote TCP target
16029 Enable auto-retry for remote TCP connections. This is useful if the remote
16030 debugging agent is launched in parallel with @value{GDBN}; there is a race
16031 condition because the agent may not become ready to accept the connection
16032 before @value{GDBN} attempts to connect. When auto-retry is
16033 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16034 to establish the connection using the timeout specified by
16035 @code{set tcp connect-timeout}.
16037 @item set tcp auto-retry off
16038 Do not auto-retry failed TCP connections.
16040 @item show tcp auto-retry
16041 Show the current auto-retry setting.
16043 @item set tcp connect-timeout @var{seconds}
16044 @cindex connection timeout, for remote TCP target
16045 @cindex timeout, for remote target connection
16046 Set the timeout for establishing a TCP connection to the remote target to
16047 @var{seconds}. The timeout affects both polling to retry failed connections
16048 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16049 that are merely slow to complete, and represents an approximate cumulative
16052 @item show tcp connect-timeout
16053 Show the current connection timeout setting.
16056 @cindex remote packets, enabling and disabling
16057 The @value{GDBN} remote protocol autodetects the packets supported by
16058 your debugging stub. If you need to override the autodetection, you
16059 can use these commands to enable or disable individual packets. Each
16060 packet can be set to @samp{on} (the remote target supports this
16061 packet), @samp{off} (the remote target does not support this packet),
16062 or @samp{auto} (detect remote target support for this packet). They
16063 all default to @samp{auto}. For more information about each packet,
16064 see @ref{Remote Protocol}.
16066 During normal use, you should not have to use any of these commands.
16067 If you do, that may be a bug in your remote debugging stub, or a bug
16068 in @value{GDBN}. You may want to report the problem to the
16069 @value{GDBN} developers.
16071 For each packet @var{name}, the command to enable or disable the
16072 packet is @code{set remote @var{name}-packet}. The available settings
16075 @multitable @columnfractions 0.28 0.32 0.25
16078 @tab Related Features
16080 @item @code{fetch-register}
16082 @tab @code{info registers}
16084 @item @code{set-register}
16088 @item @code{binary-download}
16090 @tab @code{load}, @code{set}
16092 @item @code{read-aux-vector}
16093 @tab @code{qXfer:auxv:read}
16094 @tab @code{info auxv}
16096 @item @code{symbol-lookup}
16097 @tab @code{qSymbol}
16098 @tab Detecting multiple threads
16100 @item @code{attach}
16101 @tab @code{vAttach}
16104 @item @code{verbose-resume}
16106 @tab Stepping or resuming multiple threads
16112 @item @code{software-breakpoint}
16116 @item @code{hardware-breakpoint}
16120 @item @code{write-watchpoint}
16124 @item @code{read-watchpoint}
16128 @item @code{access-watchpoint}
16132 @item @code{target-features}
16133 @tab @code{qXfer:features:read}
16134 @tab @code{set architecture}
16136 @item @code{library-info}
16137 @tab @code{qXfer:libraries:read}
16138 @tab @code{info sharedlibrary}
16140 @item @code{memory-map}
16141 @tab @code{qXfer:memory-map:read}
16142 @tab @code{info mem}
16144 @item @code{read-spu-object}
16145 @tab @code{qXfer:spu:read}
16146 @tab @code{info spu}
16148 @item @code{write-spu-object}
16149 @tab @code{qXfer:spu:write}
16150 @tab @code{info spu}
16152 @item @code{read-siginfo-object}
16153 @tab @code{qXfer:siginfo:read}
16154 @tab @code{print $_siginfo}
16156 @item @code{write-siginfo-object}
16157 @tab @code{qXfer:siginfo:write}
16158 @tab @code{set $_siginfo}
16160 @item @code{threads}
16161 @tab @code{qXfer:threads:read}
16162 @tab @code{info threads}
16164 @item @code{get-thread-local-@*storage-address}
16165 @tab @code{qGetTLSAddr}
16166 @tab Displaying @code{__thread} variables
16168 @item @code{get-thread-information-block-address}
16169 @tab @code{qGetTIBAddr}
16170 @tab Display MS-Windows Thread Information Block.
16172 @item @code{search-memory}
16173 @tab @code{qSearch:memory}
16176 @item @code{supported-packets}
16177 @tab @code{qSupported}
16178 @tab Remote communications parameters
16180 @item @code{pass-signals}
16181 @tab @code{QPassSignals}
16182 @tab @code{handle @var{signal}}
16184 @item @code{hostio-close-packet}
16185 @tab @code{vFile:close}
16186 @tab @code{remote get}, @code{remote put}
16188 @item @code{hostio-open-packet}
16189 @tab @code{vFile:open}
16190 @tab @code{remote get}, @code{remote put}
16192 @item @code{hostio-pread-packet}
16193 @tab @code{vFile:pread}
16194 @tab @code{remote get}, @code{remote put}
16196 @item @code{hostio-pwrite-packet}
16197 @tab @code{vFile:pwrite}
16198 @tab @code{remote get}, @code{remote put}
16200 @item @code{hostio-unlink-packet}
16201 @tab @code{vFile:unlink}
16202 @tab @code{remote delete}
16204 @item @code{noack-packet}
16205 @tab @code{QStartNoAckMode}
16206 @tab Packet acknowledgment
16208 @item @code{osdata}
16209 @tab @code{qXfer:osdata:read}
16210 @tab @code{info os}
16212 @item @code{query-attached}
16213 @tab @code{qAttached}
16214 @tab Querying remote process attach state.
16218 @section Implementing a Remote Stub
16220 @cindex debugging stub, example
16221 @cindex remote stub, example
16222 @cindex stub example, remote debugging
16223 The stub files provided with @value{GDBN} implement the target side of the
16224 communication protocol, and the @value{GDBN} side is implemented in the
16225 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16226 these subroutines to communicate, and ignore the details. (If you're
16227 implementing your own stub file, you can still ignore the details: start
16228 with one of the existing stub files. @file{sparc-stub.c} is the best
16229 organized, and therefore the easiest to read.)
16231 @cindex remote serial debugging, overview
16232 To debug a program running on another machine (the debugging
16233 @dfn{target} machine), you must first arrange for all the usual
16234 prerequisites for the program to run by itself. For example, for a C
16239 A startup routine to set up the C runtime environment; these usually
16240 have a name like @file{crt0}. The startup routine may be supplied by
16241 your hardware supplier, or you may have to write your own.
16244 A C subroutine library to support your program's
16245 subroutine calls, notably managing input and output.
16248 A way of getting your program to the other machine---for example, a
16249 download program. These are often supplied by the hardware
16250 manufacturer, but you may have to write your own from hardware
16254 The next step is to arrange for your program to use a serial port to
16255 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16256 machine). In general terms, the scheme looks like this:
16260 @value{GDBN} already understands how to use this protocol; when everything
16261 else is set up, you can simply use the @samp{target remote} command
16262 (@pxref{Targets,,Specifying a Debugging Target}).
16264 @item On the target,
16265 you must link with your program a few special-purpose subroutines that
16266 implement the @value{GDBN} remote serial protocol. The file containing these
16267 subroutines is called a @dfn{debugging stub}.
16269 On certain remote targets, you can use an auxiliary program
16270 @code{gdbserver} instead of linking a stub into your program.
16271 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16274 The debugging stub is specific to the architecture of the remote
16275 machine; for example, use @file{sparc-stub.c} to debug programs on
16278 @cindex remote serial stub list
16279 These working remote stubs are distributed with @value{GDBN}:
16284 @cindex @file{i386-stub.c}
16287 For Intel 386 and compatible architectures.
16290 @cindex @file{m68k-stub.c}
16291 @cindex Motorola 680x0
16293 For Motorola 680x0 architectures.
16296 @cindex @file{sh-stub.c}
16299 For Renesas SH architectures.
16302 @cindex @file{sparc-stub.c}
16304 For @sc{sparc} architectures.
16306 @item sparcl-stub.c
16307 @cindex @file{sparcl-stub.c}
16310 For Fujitsu @sc{sparclite} architectures.
16314 The @file{README} file in the @value{GDBN} distribution may list other
16315 recently added stubs.
16318 * Stub Contents:: What the stub can do for you
16319 * Bootstrapping:: What you must do for the stub
16320 * Debug Session:: Putting it all together
16323 @node Stub Contents
16324 @subsection What the Stub Can Do for You
16326 @cindex remote serial stub
16327 The debugging stub for your architecture supplies these three
16331 @item set_debug_traps
16332 @findex set_debug_traps
16333 @cindex remote serial stub, initialization
16334 This routine arranges for @code{handle_exception} to run when your
16335 program stops. You must call this subroutine explicitly near the
16336 beginning of your program.
16338 @item handle_exception
16339 @findex handle_exception
16340 @cindex remote serial stub, main routine
16341 This is the central workhorse, but your program never calls it
16342 explicitly---the setup code arranges for @code{handle_exception} to
16343 run when a trap is triggered.
16345 @code{handle_exception} takes control when your program stops during
16346 execution (for example, on a breakpoint), and mediates communications
16347 with @value{GDBN} on the host machine. This is where the communications
16348 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16349 representative on the target machine. It begins by sending summary
16350 information on the state of your program, then continues to execute,
16351 retrieving and transmitting any information @value{GDBN} needs, until you
16352 execute a @value{GDBN} command that makes your program resume; at that point,
16353 @code{handle_exception} returns control to your own code on the target
16357 @cindex @code{breakpoint} subroutine, remote
16358 Use this auxiliary subroutine to make your program contain a
16359 breakpoint. Depending on the particular situation, this may be the only
16360 way for @value{GDBN} to get control. For instance, if your target
16361 machine has some sort of interrupt button, you won't need to call this;
16362 pressing the interrupt button transfers control to
16363 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16364 simply receiving characters on the serial port may also trigger a trap;
16365 again, in that situation, you don't need to call @code{breakpoint} from
16366 your own program---simply running @samp{target remote} from the host
16367 @value{GDBN} session gets control.
16369 Call @code{breakpoint} if none of these is true, or if you simply want
16370 to make certain your program stops at a predetermined point for the
16371 start of your debugging session.
16374 @node Bootstrapping
16375 @subsection What You Must Do for the Stub
16377 @cindex remote stub, support routines
16378 The debugging stubs that come with @value{GDBN} are set up for a particular
16379 chip architecture, but they have no information about the rest of your
16380 debugging target machine.
16382 First of all you need to tell the stub how to communicate with the
16386 @item int getDebugChar()
16387 @findex getDebugChar
16388 Write this subroutine to read a single character from the serial port.
16389 It may be identical to @code{getchar} for your target system; a
16390 different name is used to allow you to distinguish the two if you wish.
16392 @item void putDebugChar(int)
16393 @findex putDebugChar
16394 Write this subroutine to write a single character to the serial port.
16395 It may be identical to @code{putchar} for your target system; a
16396 different name is used to allow you to distinguish the two if you wish.
16399 @cindex control C, and remote debugging
16400 @cindex interrupting remote targets
16401 If you want @value{GDBN} to be able to stop your program while it is
16402 running, you need to use an interrupt-driven serial driver, and arrange
16403 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16404 character). That is the character which @value{GDBN} uses to tell the
16405 remote system to stop.
16407 Getting the debugging target to return the proper status to @value{GDBN}
16408 probably requires changes to the standard stub; one quick and dirty way
16409 is to just execute a breakpoint instruction (the ``dirty'' part is that
16410 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16412 Other routines you need to supply are:
16415 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16416 @findex exceptionHandler
16417 Write this function to install @var{exception_address} in the exception
16418 handling tables. You need to do this because the stub does not have any
16419 way of knowing what the exception handling tables on your target system
16420 are like (for example, the processor's table might be in @sc{rom},
16421 containing entries which point to a table in @sc{ram}).
16422 @var{exception_number} is the exception number which should be changed;
16423 its meaning is architecture-dependent (for example, different numbers
16424 might represent divide by zero, misaligned access, etc). When this
16425 exception occurs, control should be transferred directly to
16426 @var{exception_address}, and the processor state (stack, registers,
16427 and so on) should be just as it is when a processor exception occurs. So if
16428 you want to use a jump instruction to reach @var{exception_address}, it
16429 should be a simple jump, not a jump to subroutine.
16431 For the 386, @var{exception_address} should be installed as an interrupt
16432 gate so that interrupts are masked while the handler runs. The gate
16433 should be at privilege level 0 (the most privileged level). The
16434 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16435 help from @code{exceptionHandler}.
16437 @item void flush_i_cache()
16438 @findex flush_i_cache
16439 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16440 instruction cache, if any, on your target machine. If there is no
16441 instruction cache, this subroutine may be a no-op.
16443 On target machines that have instruction caches, @value{GDBN} requires this
16444 function to make certain that the state of your program is stable.
16448 You must also make sure this library routine is available:
16451 @item void *memset(void *, int, int)
16453 This is the standard library function @code{memset} that sets an area of
16454 memory to a known value. If you have one of the free versions of
16455 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16456 either obtain it from your hardware manufacturer, or write your own.
16459 If you do not use the GNU C compiler, you may need other standard
16460 library subroutines as well; this varies from one stub to another,
16461 but in general the stubs are likely to use any of the common library
16462 subroutines which @code{@value{NGCC}} generates as inline code.
16465 @node Debug Session
16466 @subsection Putting it All Together
16468 @cindex remote serial debugging summary
16469 In summary, when your program is ready to debug, you must follow these
16474 Make sure you have defined the supporting low-level routines
16475 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16477 @code{getDebugChar}, @code{putDebugChar},
16478 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16482 Insert these lines near the top of your program:
16490 For the 680x0 stub only, you need to provide a variable called
16491 @code{exceptionHook}. Normally you just use:
16494 void (*exceptionHook)() = 0;
16498 but if before calling @code{set_debug_traps}, you set it to point to a
16499 function in your program, that function is called when
16500 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16501 error). The function indicated by @code{exceptionHook} is called with
16502 one parameter: an @code{int} which is the exception number.
16505 Compile and link together: your program, the @value{GDBN} debugging stub for
16506 your target architecture, and the supporting subroutines.
16509 Make sure you have a serial connection between your target machine and
16510 the @value{GDBN} host, and identify the serial port on the host.
16513 @c The "remote" target now provides a `load' command, so we should
16514 @c document that. FIXME.
16515 Download your program to your target machine (or get it there by
16516 whatever means the manufacturer provides), and start it.
16519 Start @value{GDBN} on the host, and connect to the target
16520 (@pxref{Connecting,,Connecting to a Remote Target}).
16524 @node Configurations
16525 @chapter Configuration-Specific Information
16527 While nearly all @value{GDBN} commands are available for all native and
16528 cross versions of the debugger, there are some exceptions. This chapter
16529 describes things that are only available in certain configurations.
16531 There are three major categories of configurations: native
16532 configurations, where the host and target are the same, embedded
16533 operating system configurations, which are usually the same for several
16534 different processor architectures, and bare embedded processors, which
16535 are quite different from each other.
16540 * Embedded Processors::
16547 This section describes details specific to particular native
16552 * BSD libkvm Interface:: Debugging BSD kernel memory images
16553 * SVR4 Process Information:: SVR4 process information
16554 * DJGPP Native:: Features specific to the DJGPP port
16555 * Cygwin Native:: Features specific to the Cygwin port
16556 * Hurd Native:: Features specific to @sc{gnu} Hurd
16557 * Neutrino:: Features specific to QNX Neutrino
16558 * Darwin:: Features specific to Darwin
16564 On HP-UX systems, if you refer to a function or variable name that
16565 begins with a dollar sign, @value{GDBN} searches for a user or system
16566 name first, before it searches for a convenience variable.
16569 @node BSD libkvm Interface
16570 @subsection BSD libkvm Interface
16573 @cindex kernel memory image
16574 @cindex kernel crash dump
16576 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16577 interface that provides a uniform interface for accessing kernel virtual
16578 memory images, including live systems and crash dumps. @value{GDBN}
16579 uses this interface to allow you to debug live kernels and kernel crash
16580 dumps on many native BSD configurations. This is implemented as a
16581 special @code{kvm} debugging target. For debugging a live system, load
16582 the currently running kernel into @value{GDBN} and connect to the
16586 (@value{GDBP}) @b{target kvm}
16589 For debugging crash dumps, provide the file name of the crash dump as an
16593 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16596 Once connected to the @code{kvm} target, the following commands are
16602 Set current context from the @dfn{Process Control Block} (PCB) address.
16605 Set current context from proc address. This command isn't available on
16606 modern FreeBSD systems.
16609 @node SVR4 Process Information
16610 @subsection SVR4 Process Information
16612 @cindex examine process image
16613 @cindex process info via @file{/proc}
16615 Many versions of SVR4 and compatible systems provide a facility called
16616 @samp{/proc} that can be used to examine the image of a running
16617 process using file-system subroutines. If @value{GDBN} is configured
16618 for an operating system with this facility, the command @code{info
16619 proc} is available to report information about the process running
16620 your program, or about any process running on your system. @code{info
16621 proc} works only on SVR4 systems that include the @code{procfs} code.
16622 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16623 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16629 @itemx info proc @var{process-id}
16630 Summarize available information about any running process. If a
16631 process ID is specified by @var{process-id}, display information about
16632 that process; otherwise display information about the program being
16633 debugged. The summary includes the debugged process ID, the command
16634 line used to invoke it, its current working directory, and its
16635 executable file's absolute file name.
16637 On some systems, @var{process-id} can be of the form
16638 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16639 within a process. If the optional @var{pid} part is missing, it means
16640 a thread from the process being debugged (the leading @samp{/} still
16641 needs to be present, or else @value{GDBN} will interpret the number as
16642 a process ID rather than a thread ID).
16644 @item info proc mappings
16645 @cindex memory address space mappings
16646 Report the memory address space ranges accessible in the program, with
16647 information on whether the process has read, write, or execute access
16648 rights to each range. On @sc{gnu}/Linux systems, each memory range
16649 includes the object file which is mapped to that range, instead of the
16650 memory access rights to that range.
16652 @item info proc stat
16653 @itemx info proc status
16654 @cindex process detailed status information
16655 These subcommands are specific to @sc{gnu}/Linux systems. They show
16656 the process-related information, including the user ID and group ID;
16657 how many threads are there in the process; its virtual memory usage;
16658 the signals that are pending, blocked, and ignored; its TTY; its
16659 consumption of system and user time; its stack size; its @samp{nice}
16660 value; etc. For more information, see the @samp{proc} man page
16661 (type @kbd{man 5 proc} from your shell prompt).
16663 @item info proc all
16664 Show all the information about the process described under all of the
16665 above @code{info proc} subcommands.
16668 @comment These sub-options of 'info proc' were not included when
16669 @comment procfs.c was re-written. Keep their descriptions around
16670 @comment against the day when someone finds the time to put them back in.
16671 @kindex info proc times
16672 @item info proc times
16673 Starting time, user CPU time, and system CPU time for your program and
16676 @kindex info proc id
16678 Report on the process IDs related to your program: its own process ID,
16679 the ID of its parent, the process group ID, and the session ID.
16682 @item set procfs-trace
16683 @kindex set procfs-trace
16684 @cindex @code{procfs} API calls
16685 This command enables and disables tracing of @code{procfs} API calls.
16687 @item show procfs-trace
16688 @kindex show procfs-trace
16689 Show the current state of @code{procfs} API call tracing.
16691 @item set procfs-file @var{file}
16692 @kindex set procfs-file
16693 Tell @value{GDBN} to write @code{procfs} API trace to the named
16694 @var{file}. @value{GDBN} appends the trace info to the previous
16695 contents of the file. The default is to display the trace on the
16698 @item show procfs-file
16699 @kindex show procfs-file
16700 Show the file to which @code{procfs} API trace is written.
16702 @item proc-trace-entry
16703 @itemx proc-trace-exit
16704 @itemx proc-untrace-entry
16705 @itemx proc-untrace-exit
16706 @kindex proc-trace-entry
16707 @kindex proc-trace-exit
16708 @kindex proc-untrace-entry
16709 @kindex proc-untrace-exit
16710 These commands enable and disable tracing of entries into and exits
16711 from the @code{syscall} interface.
16714 @kindex info pidlist
16715 @cindex process list, QNX Neutrino
16716 For QNX Neutrino only, this command displays the list of all the
16717 processes and all the threads within each process.
16720 @kindex info meminfo
16721 @cindex mapinfo list, QNX Neutrino
16722 For QNX Neutrino only, this command displays the list of all mapinfos.
16726 @subsection Features for Debugging @sc{djgpp} Programs
16727 @cindex @sc{djgpp} debugging
16728 @cindex native @sc{djgpp} debugging
16729 @cindex MS-DOS-specific commands
16732 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16733 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16734 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16735 top of real-mode DOS systems and their emulations.
16737 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16738 defines a few commands specific to the @sc{djgpp} port. This
16739 subsection describes those commands.
16744 This is a prefix of @sc{djgpp}-specific commands which print
16745 information about the target system and important OS structures.
16748 @cindex MS-DOS system info
16749 @cindex free memory information (MS-DOS)
16750 @item info dos sysinfo
16751 This command displays assorted information about the underlying
16752 platform: the CPU type and features, the OS version and flavor, the
16753 DPMI version, and the available conventional and DPMI memory.
16758 @cindex segment descriptor tables
16759 @cindex descriptor tables display
16761 @itemx info dos ldt
16762 @itemx info dos idt
16763 These 3 commands display entries from, respectively, Global, Local,
16764 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16765 tables are data structures which store a descriptor for each segment
16766 that is currently in use. The segment's selector is an index into a
16767 descriptor table; the table entry for that index holds the
16768 descriptor's base address and limit, and its attributes and access
16771 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16772 segment (used for both data and the stack), and a DOS segment (which
16773 allows access to DOS/BIOS data structures and absolute addresses in
16774 conventional memory). However, the DPMI host will usually define
16775 additional segments in order to support the DPMI environment.
16777 @cindex garbled pointers
16778 These commands allow to display entries from the descriptor tables.
16779 Without an argument, all entries from the specified table are
16780 displayed. An argument, which should be an integer expression, means
16781 display a single entry whose index is given by the argument. For
16782 example, here's a convenient way to display information about the
16783 debugged program's data segment:
16786 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16787 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16791 This comes in handy when you want to see whether a pointer is outside
16792 the data segment's limit (i.e.@: @dfn{garbled}).
16794 @cindex page tables display (MS-DOS)
16796 @itemx info dos pte
16797 These two commands display entries from, respectively, the Page
16798 Directory and the Page Tables. Page Directories and Page Tables are
16799 data structures which control how virtual memory addresses are mapped
16800 into physical addresses. A Page Table includes an entry for every
16801 page of memory that is mapped into the program's address space; there
16802 may be several Page Tables, each one holding up to 4096 entries. A
16803 Page Directory has up to 4096 entries, one each for every Page Table
16804 that is currently in use.
16806 Without an argument, @kbd{info dos pde} displays the entire Page
16807 Directory, and @kbd{info dos pte} displays all the entries in all of
16808 the Page Tables. An argument, an integer expression, given to the
16809 @kbd{info dos pde} command means display only that entry from the Page
16810 Directory table. An argument given to the @kbd{info dos pte} command
16811 means display entries from a single Page Table, the one pointed to by
16812 the specified entry in the Page Directory.
16814 @cindex direct memory access (DMA) on MS-DOS
16815 These commands are useful when your program uses @dfn{DMA} (Direct
16816 Memory Access), which needs physical addresses to program the DMA
16819 These commands are supported only with some DPMI servers.
16821 @cindex physical address from linear address
16822 @item info dos address-pte @var{addr}
16823 This command displays the Page Table entry for a specified linear
16824 address. The argument @var{addr} is a linear address which should
16825 already have the appropriate segment's base address added to it,
16826 because this command accepts addresses which may belong to @emph{any}
16827 segment. For example, here's how to display the Page Table entry for
16828 the page where a variable @code{i} is stored:
16831 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16832 @exdent @code{Page Table entry for address 0x11a00d30:}
16833 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16837 This says that @code{i} is stored at offset @code{0xd30} from the page
16838 whose physical base address is @code{0x02698000}, and shows all the
16839 attributes of that page.
16841 Note that you must cast the addresses of variables to a @code{char *},
16842 since otherwise the value of @code{__djgpp_base_address}, the base
16843 address of all variables and functions in a @sc{djgpp} program, will
16844 be added using the rules of C pointer arithmetics: if @code{i} is
16845 declared an @code{int}, @value{GDBN} will add 4 times the value of
16846 @code{__djgpp_base_address} to the address of @code{i}.
16848 Here's another example, it displays the Page Table entry for the
16852 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16853 @exdent @code{Page Table entry for address 0x29110:}
16854 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16858 (The @code{+ 3} offset is because the transfer buffer's address is the
16859 3rd member of the @code{_go32_info_block} structure.) The output
16860 clearly shows that this DPMI server maps the addresses in conventional
16861 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16862 linear (@code{0x29110}) addresses are identical.
16864 This command is supported only with some DPMI servers.
16867 @cindex DOS serial data link, remote debugging
16868 In addition to native debugging, the DJGPP port supports remote
16869 debugging via a serial data link. The following commands are specific
16870 to remote serial debugging in the DJGPP port of @value{GDBN}.
16873 @kindex set com1base
16874 @kindex set com1irq
16875 @kindex set com2base
16876 @kindex set com2irq
16877 @kindex set com3base
16878 @kindex set com3irq
16879 @kindex set com4base
16880 @kindex set com4irq
16881 @item set com1base @var{addr}
16882 This command sets the base I/O port address of the @file{COM1} serial
16885 @item set com1irq @var{irq}
16886 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16887 for the @file{COM1} serial port.
16889 There are similar commands @samp{set com2base}, @samp{set com3irq},
16890 etc.@: for setting the port address and the @code{IRQ} lines for the
16893 @kindex show com1base
16894 @kindex show com1irq
16895 @kindex show com2base
16896 @kindex show com2irq
16897 @kindex show com3base
16898 @kindex show com3irq
16899 @kindex show com4base
16900 @kindex show com4irq
16901 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16902 display the current settings of the base address and the @code{IRQ}
16903 lines used by the COM ports.
16906 @kindex info serial
16907 @cindex DOS serial port status
16908 This command prints the status of the 4 DOS serial ports. For each
16909 port, it prints whether it's active or not, its I/O base address and
16910 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16911 counts of various errors encountered so far.
16915 @node Cygwin Native
16916 @subsection Features for Debugging MS Windows PE Executables
16917 @cindex MS Windows debugging
16918 @cindex native Cygwin debugging
16919 @cindex Cygwin-specific commands
16921 @value{GDBN} supports native debugging of MS Windows programs, including
16922 DLLs with and without symbolic debugging information.
16924 @cindex Ctrl-BREAK, MS-Windows
16925 @cindex interrupt debuggee on MS-Windows
16926 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16927 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16928 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16929 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16930 sequence, which can be used to interrupt the debuggee even if it
16933 There are various additional Cygwin-specific commands, described in
16934 this section. Working with DLLs that have no debugging symbols is
16935 described in @ref{Non-debug DLL Symbols}.
16940 This is a prefix of MS Windows-specific commands which print
16941 information about the target system and important OS structures.
16943 @item info w32 selector
16944 This command displays information returned by
16945 the Win32 API @code{GetThreadSelectorEntry} function.
16946 It takes an optional argument that is evaluated to
16947 a long value to give the information about this given selector.
16948 Without argument, this command displays information
16949 about the six segment registers.
16951 @item info w32 thread-information-block
16952 This command displays thread specific information stored in the
16953 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16954 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16958 This is a Cygwin-specific alias of @code{info shared}.
16960 @kindex dll-symbols
16962 This command loads symbols from a dll similarly to
16963 add-sym command but without the need to specify a base address.
16965 @kindex set cygwin-exceptions
16966 @cindex debugging the Cygwin DLL
16967 @cindex Cygwin DLL, debugging
16968 @item set cygwin-exceptions @var{mode}
16969 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16970 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16971 @value{GDBN} will delay recognition of exceptions, and may ignore some
16972 exceptions which seem to be caused by internal Cygwin DLL
16973 ``bookkeeping''. This option is meant primarily for debugging the
16974 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16975 @value{GDBN} users with false @code{SIGSEGV} signals.
16977 @kindex show cygwin-exceptions
16978 @item show cygwin-exceptions
16979 Displays whether @value{GDBN} will break on exceptions that happen
16980 inside the Cygwin DLL itself.
16982 @kindex set new-console
16983 @item set new-console @var{mode}
16984 If @var{mode} is @code{on} the debuggee will
16985 be started in a new console on next start.
16986 If @var{mode} is @code{off}, the debuggee will
16987 be started in the same console as the debugger.
16989 @kindex show new-console
16990 @item show new-console
16991 Displays whether a new console is used
16992 when the debuggee is started.
16994 @kindex set new-group
16995 @item set new-group @var{mode}
16996 This boolean value controls whether the debuggee should
16997 start a new group or stay in the same group as the debugger.
16998 This affects the way the Windows OS handles
17001 @kindex show new-group
17002 @item show new-group
17003 Displays current value of new-group boolean.
17005 @kindex set debugevents
17006 @item set debugevents
17007 This boolean value adds debug output concerning kernel events related
17008 to the debuggee seen by the debugger. This includes events that
17009 signal thread and process creation and exit, DLL loading and
17010 unloading, console interrupts, and debugging messages produced by the
17011 Windows @code{OutputDebugString} API call.
17013 @kindex set debugexec
17014 @item set debugexec
17015 This boolean value adds debug output concerning execute events
17016 (such as resume thread) seen by the debugger.
17018 @kindex set debugexceptions
17019 @item set debugexceptions
17020 This boolean value adds debug output concerning exceptions in the
17021 debuggee seen by the debugger.
17023 @kindex set debugmemory
17024 @item set debugmemory
17025 This boolean value adds debug output concerning debuggee memory reads
17026 and writes by the debugger.
17030 This boolean values specifies whether the debuggee is called
17031 via a shell or directly (default value is on).
17035 Displays if the debuggee will be started with a shell.
17040 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17043 @node Non-debug DLL Symbols
17044 @subsubsection Support for DLLs without Debugging Symbols
17045 @cindex DLLs with no debugging symbols
17046 @cindex Minimal symbols and DLLs
17048 Very often on windows, some of the DLLs that your program relies on do
17049 not include symbolic debugging information (for example,
17050 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17051 symbols in a DLL, it relies on the minimal amount of symbolic
17052 information contained in the DLL's export table. This section
17053 describes working with such symbols, known internally to @value{GDBN} as
17054 ``minimal symbols''.
17056 Note that before the debugged program has started execution, no DLLs
17057 will have been loaded. The easiest way around this problem is simply to
17058 start the program --- either by setting a breakpoint or letting the
17059 program run once to completion. It is also possible to force
17060 @value{GDBN} to load a particular DLL before starting the executable ---
17061 see the shared library information in @ref{Files}, or the
17062 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17063 explicitly loading symbols from a DLL with no debugging information will
17064 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17065 which may adversely affect symbol lookup performance.
17067 @subsubsection DLL Name Prefixes
17069 In keeping with the naming conventions used by the Microsoft debugging
17070 tools, DLL export symbols are made available with a prefix based on the
17071 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17072 also entered into the symbol table, so @code{CreateFileA} is often
17073 sufficient. In some cases there will be name clashes within a program
17074 (particularly if the executable itself includes full debugging symbols)
17075 necessitating the use of the fully qualified name when referring to the
17076 contents of the DLL. Use single-quotes around the name to avoid the
17077 exclamation mark (``!'') being interpreted as a language operator.
17079 Note that the internal name of the DLL may be all upper-case, even
17080 though the file name of the DLL is lower-case, or vice-versa. Since
17081 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17082 some confusion. If in doubt, try the @code{info functions} and
17083 @code{info variables} commands or even @code{maint print msymbols}
17084 (@pxref{Symbols}). Here's an example:
17087 (@value{GDBP}) info function CreateFileA
17088 All functions matching regular expression "CreateFileA":
17090 Non-debugging symbols:
17091 0x77e885f4 CreateFileA
17092 0x77e885f4 KERNEL32!CreateFileA
17096 (@value{GDBP}) info function !
17097 All functions matching regular expression "!":
17099 Non-debugging symbols:
17100 0x6100114c cygwin1!__assert
17101 0x61004034 cygwin1!_dll_crt0@@0
17102 0x61004240 cygwin1!dll_crt0(per_process *)
17106 @subsubsection Working with Minimal Symbols
17108 Symbols extracted from a DLL's export table do not contain very much
17109 type information. All that @value{GDBN} can do is guess whether a symbol
17110 refers to a function or variable depending on the linker section that
17111 contains the symbol. Also note that the actual contents of the memory
17112 contained in a DLL are not available unless the program is running. This
17113 means that you cannot examine the contents of a variable or disassemble
17114 a function within a DLL without a running program.
17116 Variables are generally treated as pointers and dereferenced
17117 automatically. For this reason, it is often necessary to prefix a
17118 variable name with the address-of operator (``&'') and provide explicit
17119 type information in the command. Here's an example of the type of
17123 (@value{GDBP}) print 'cygwin1!__argv'
17128 (@value{GDBP}) x 'cygwin1!__argv'
17129 0x10021610: "\230y\""
17132 And two possible solutions:
17135 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17136 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17140 (@value{GDBP}) x/2x &'cygwin1!__argv'
17141 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17142 (@value{GDBP}) x/x 0x10021608
17143 0x10021608: 0x0022fd98
17144 (@value{GDBP}) x/s 0x0022fd98
17145 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17148 Setting a break point within a DLL is possible even before the program
17149 starts execution. However, under these circumstances, @value{GDBN} can't
17150 examine the initial instructions of the function in order to skip the
17151 function's frame set-up code. You can work around this by using ``*&''
17152 to set the breakpoint at a raw memory address:
17155 (@value{GDBP}) break *&'python22!PyOS_Readline'
17156 Breakpoint 1 at 0x1e04eff0
17159 The author of these extensions is not entirely convinced that setting a
17160 break point within a shared DLL like @file{kernel32.dll} is completely
17164 @subsection Commands Specific to @sc{gnu} Hurd Systems
17165 @cindex @sc{gnu} Hurd debugging
17167 This subsection describes @value{GDBN} commands specific to the
17168 @sc{gnu} Hurd native debugging.
17173 @kindex set signals@r{, Hurd command}
17174 @kindex set sigs@r{, Hurd command}
17175 This command toggles the state of inferior signal interception by
17176 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17177 affected by this command. @code{sigs} is a shorthand alias for
17182 @kindex show signals@r{, Hurd command}
17183 @kindex show sigs@r{, Hurd command}
17184 Show the current state of intercepting inferior's signals.
17186 @item set signal-thread
17187 @itemx set sigthread
17188 @kindex set signal-thread
17189 @kindex set sigthread
17190 This command tells @value{GDBN} which thread is the @code{libc} signal
17191 thread. That thread is run when a signal is delivered to a running
17192 process. @code{set sigthread} is the shorthand alias of @code{set
17195 @item show signal-thread
17196 @itemx show sigthread
17197 @kindex show signal-thread
17198 @kindex show sigthread
17199 These two commands show which thread will run when the inferior is
17200 delivered a signal.
17203 @kindex set stopped@r{, Hurd command}
17204 This commands tells @value{GDBN} that the inferior process is stopped,
17205 as with the @code{SIGSTOP} signal. The stopped process can be
17206 continued by delivering a signal to it.
17209 @kindex show stopped@r{, Hurd command}
17210 This command shows whether @value{GDBN} thinks the debuggee is
17213 @item set exceptions
17214 @kindex set exceptions@r{, Hurd command}
17215 Use this command to turn off trapping of exceptions in the inferior.
17216 When exception trapping is off, neither breakpoints nor
17217 single-stepping will work. To restore the default, set exception
17220 @item show exceptions
17221 @kindex show exceptions@r{, Hurd command}
17222 Show the current state of trapping exceptions in the inferior.
17224 @item set task pause
17225 @kindex set task@r{, Hurd commands}
17226 @cindex task attributes (@sc{gnu} Hurd)
17227 @cindex pause current task (@sc{gnu} Hurd)
17228 This command toggles task suspension when @value{GDBN} has control.
17229 Setting it to on takes effect immediately, and the task is suspended
17230 whenever @value{GDBN} gets control. Setting it to off will take
17231 effect the next time the inferior is continued. If this option is set
17232 to off, you can use @code{set thread default pause on} or @code{set
17233 thread pause on} (see below) to pause individual threads.
17235 @item show task pause
17236 @kindex show task@r{, Hurd commands}
17237 Show the current state of task suspension.
17239 @item set task detach-suspend-count
17240 @cindex task suspend count
17241 @cindex detach from task, @sc{gnu} Hurd
17242 This command sets the suspend count the task will be left with when
17243 @value{GDBN} detaches from it.
17245 @item show task detach-suspend-count
17246 Show the suspend count the task will be left with when detaching.
17248 @item set task exception-port
17249 @itemx set task excp
17250 @cindex task exception port, @sc{gnu} Hurd
17251 This command sets the task exception port to which @value{GDBN} will
17252 forward exceptions. The argument should be the value of the @dfn{send
17253 rights} of the task. @code{set task excp} is a shorthand alias.
17255 @item set noninvasive
17256 @cindex noninvasive task options
17257 This command switches @value{GDBN} to a mode that is the least
17258 invasive as far as interfering with the inferior is concerned. This
17259 is the same as using @code{set task pause}, @code{set exceptions}, and
17260 @code{set signals} to values opposite to the defaults.
17262 @item info send-rights
17263 @itemx info receive-rights
17264 @itemx info port-rights
17265 @itemx info port-sets
17266 @itemx info dead-names
17269 @cindex send rights, @sc{gnu} Hurd
17270 @cindex receive rights, @sc{gnu} Hurd
17271 @cindex port rights, @sc{gnu} Hurd
17272 @cindex port sets, @sc{gnu} Hurd
17273 @cindex dead names, @sc{gnu} Hurd
17274 These commands display information about, respectively, send rights,
17275 receive rights, port rights, port sets, and dead names of a task.
17276 There are also shorthand aliases: @code{info ports} for @code{info
17277 port-rights} and @code{info psets} for @code{info port-sets}.
17279 @item set thread pause
17280 @kindex set thread@r{, Hurd command}
17281 @cindex thread properties, @sc{gnu} Hurd
17282 @cindex pause current thread (@sc{gnu} Hurd)
17283 This command toggles current thread suspension when @value{GDBN} has
17284 control. Setting it to on takes effect immediately, and the current
17285 thread is suspended whenever @value{GDBN} gets control. Setting it to
17286 off will take effect the next time the inferior is continued.
17287 Normally, this command has no effect, since when @value{GDBN} has
17288 control, the whole task is suspended. However, if you used @code{set
17289 task pause off} (see above), this command comes in handy to suspend
17290 only the current thread.
17292 @item show thread pause
17293 @kindex show thread@r{, Hurd command}
17294 This command shows the state of current thread suspension.
17296 @item set thread run
17297 This command sets whether the current thread is allowed to run.
17299 @item show thread run
17300 Show whether the current thread is allowed to run.
17302 @item set thread detach-suspend-count
17303 @cindex thread suspend count, @sc{gnu} Hurd
17304 @cindex detach from thread, @sc{gnu} Hurd
17305 This command sets the suspend count @value{GDBN} will leave on a
17306 thread when detaching. This number is relative to the suspend count
17307 found by @value{GDBN} when it notices the thread; use @code{set thread
17308 takeover-suspend-count} to force it to an absolute value.
17310 @item show thread detach-suspend-count
17311 Show the suspend count @value{GDBN} will leave on the thread when
17314 @item set thread exception-port
17315 @itemx set thread excp
17316 Set the thread exception port to which to forward exceptions. This
17317 overrides the port set by @code{set task exception-port} (see above).
17318 @code{set thread excp} is the shorthand alias.
17320 @item set thread takeover-suspend-count
17321 Normally, @value{GDBN}'s thread suspend counts are relative to the
17322 value @value{GDBN} finds when it notices each thread. This command
17323 changes the suspend counts to be absolute instead.
17325 @item set thread default
17326 @itemx show thread default
17327 @cindex thread default settings, @sc{gnu} Hurd
17328 Each of the above @code{set thread} commands has a @code{set thread
17329 default} counterpart (e.g., @code{set thread default pause}, @code{set
17330 thread default exception-port}, etc.). The @code{thread default}
17331 variety of commands sets the default thread properties for all
17332 threads; you can then change the properties of individual threads with
17333 the non-default commands.
17338 @subsection QNX Neutrino
17339 @cindex QNX Neutrino
17341 @value{GDBN} provides the following commands specific to the QNX
17345 @item set debug nto-debug
17346 @kindex set debug nto-debug
17347 When set to on, enables debugging messages specific to the QNX
17350 @item show debug nto-debug
17351 @kindex show debug nto-debug
17352 Show the current state of QNX Neutrino messages.
17359 @value{GDBN} provides the following commands specific to the Darwin target:
17362 @item set debug darwin @var{num}
17363 @kindex set debug darwin
17364 When set to a non zero value, enables debugging messages specific to
17365 the Darwin support. Higher values produce more verbose output.
17367 @item show debug darwin
17368 @kindex show debug darwin
17369 Show the current state of Darwin messages.
17371 @item set debug mach-o @var{num}
17372 @kindex set debug mach-o
17373 When set to a non zero value, enables debugging messages while
17374 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17375 file format used on Darwin for object and executable files.) Higher
17376 values produce more verbose output. This is a command to diagnose
17377 problems internal to @value{GDBN} and should not be needed in normal
17380 @item show debug mach-o
17381 @kindex show debug mach-o
17382 Show the current state of Mach-O file messages.
17384 @item set mach-exceptions on
17385 @itemx set mach-exceptions off
17386 @kindex set mach-exceptions
17387 On Darwin, faults are first reported as a Mach exception and are then
17388 mapped to a Posix signal. Use this command to turn on trapping of
17389 Mach exceptions in the inferior. This might be sometimes useful to
17390 better understand the cause of a fault. The default is off.
17392 @item show mach-exceptions
17393 @kindex show mach-exceptions
17394 Show the current state of exceptions trapping.
17399 @section Embedded Operating Systems
17401 This section describes configurations involving the debugging of
17402 embedded operating systems that are available for several different
17406 * VxWorks:: Using @value{GDBN} with VxWorks
17409 @value{GDBN} includes the ability to debug programs running on
17410 various real-time operating systems.
17413 @subsection Using @value{GDBN} with VxWorks
17419 @kindex target vxworks
17420 @item target vxworks @var{machinename}
17421 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17422 is the target system's machine name or IP address.
17426 On VxWorks, @code{load} links @var{filename} dynamically on the
17427 current target system as well as adding its symbols in @value{GDBN}.
17429 @value{GDBN} enables developers to spawn and debug tasks running on networked
17430 VxWorks targets from a Unix host. Already-running tasks spawned from
17431 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17432 both the Unix host and on the VxWorks target. The program
17433 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17434 installed with the name @code{vxgdb}, to distinguish it from a
17435 @value{GDBN} for debugging programs on the host itself.)
17438 @item VxWorks-timeout @var{args}
17439 @kindex vxworks-timeout
17440 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17441 This option is set by the user, and @var{args} represents the number of
17442 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17443 your VxWorks target is a slow software simulator or is on the far side
17444 of a thin network line.
17447 The following information on connecting to VxWorks was current when
17448 this manual was produced; newer releases of VxWorks may use revised
17451 @findex INCLUDE_RDB
17452 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17453 to include the remote debugging interface routines in the VxWorks
17454 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17455 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17456 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17457 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17458 information on configuring and remaking VxWorks, see the manufacturer's
17460 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17462 Once you have included @file{rdb.a} in your VxWorks system image and set
17463 your Unix execution search path to find @value{GDBN}, you are ready to
17464 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17465 @code{vxgdb}, depending on your installation).
17467 @value{GDBN} comes up showing the prompt:
17474 * VxWorks Connection:: Connecting to VxWorks
17475 * VxWorks Download:: VxWorks download
17476 * VxWorks Attach:: Running tasks
17479 @node VxWorks Connection
17480 @subsubsection Connecting to VxWorks
17482 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17483 network. To connect to a target whose host name is ``@code{tt}'', type:
17486 (vxgdb) target vxworks tt
17490 @value{GDBN} displays messages like these:
17493 Attaching remote machine across net...
17498 @value{GDBN} then attempts to read the symbol tables of any object modules
17499 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17500 these files by searching the directories listed in the command search
17501 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17502 to find an object file, it displays a message such as:
17505 prog.o: No such file or directory.
17508 When this happens, add the appropriate directory to the search path with
17509 the @value{GDBN} command @code{path}, and execute the @code{target}
17512 @node VxWorks Download
17513 @subsubsection VxWorks Download
17515 @cindex download to VxWorks
17516 If you have connected to the VxWorks target and you want to debug an
17517 object that has not yet been loaded, you can use the @value{GDBN}
17518 @code{load} command to download a file from Unix to VxWorks
17519 incrementally. The object file given as an argument to the @code{load}
17520 command is actually opened twice: first by the VxWorks target in order
17521 to download the code, then by @value{GDBN} in order to read the symbol
17522 table. This can lead to problems if the current working directories on
17523 the two systems differ. If both systems have NFS mounted the same
17524 filesystems, you can avoid these problems by using absolute paths.
17525 Otherwise, it is simplest to set the working directory on both systems
17526 to the directory in which the object file resides, and then to reference
17527 the file by its name, without any path. For instance, a program
17528 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17529 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17530 program, type this on VxWorks:
17533 -> cd "@var{vxpath}/vw/demo/rdb"
17537 Then, in @value{GDBN}, type:
17540 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17541 (vxgdb) load prog.o
17544 @value{GDBN} displays a response similar to this:
17547 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17550 You can also use the @code{load} command to reload an object module
17551 after editing and recompiling the corresponding source file. Note that
17552 this makes @value{GDBN} delete all currently-defined breakpoints,
17553 auto-displays, and convenience variables, and to clear the value
17554 history. (This is necessary in order to preserve the integrity of
17555 debugger's data structures that reference the target system's symbol
17558 @node VxWorks Attach
17559 @subsubsection Running Tasks
17561 @cindex running VxWorks tasks
17562 You can also attach to an existing task using the @code{attach} command as
17566 (vxgdb) attach @var{task}
17570 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17571 or suspended when you attach to it. Running tasks are suspended at
17572 the time of attachment.
17574 @node Embedded Processors
17575 @section Embedded Processors
17577 This section goes into details specific to particular embedded
17580 @cindex send command to simulator
17581 Whenever a specific embedded processor has a simulator, @value{GDBN}
17582 allows to send an arbitrary command to the simulator.
17585 @item sim @var{command}
17586 @kindex sim@r{, a command}
17587 Send an arbitrary @var{command} string to the simulator. Consult the
17588 documentation for the specific simulator in use for information about
17589 acceptable commands.
17595 * M32R/D:: Renesas M32R/D
17596 * M68K:: Motorola M68K
17597 * MicroBlaze:: Xilinx MicroBlaze
17598 * MIPS Embedded:: MIPS Embedded
17599 * OpenRISC 1000:: OpenRisc 1000
17600 * PA:: HP PA Embedded
17601 * PowerPC Embedded:: PowerPC Embedded
17602 * Sparclet:: Tsqware Sparclet
17603 * Sparclite:: Fujitsu Sparclite
17604 * Z8000:: Zilog Z8000
17607 * Super-H:: Renesas Super-H
17616 @item target rdi @var{dev}
17617 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17618 use this target to communicate with both boards running the Angel
17619 monitor, or with the EmbeddedICE JTAG debug device.
17622 @item target rdp @var{dev}
17627 @value{GDBN} provides the following ARM-specific commands:
17630 @item set arm disassembler
17632 This commands selects from a list of disassembly styles. The
17633 @code{"std"} style is the standard style.
17635 @item show arm disassembler
17637 Show the current disassembly style.
17639 @item set arm apcs32
17640 @cindex ARM 32-bit mode
17641 This command toggles ARM operation mode between 32-bit and 26-bit.
17643 @item show arm apcs32
17644 Display the current usage of the ARM 32-bit mode.
17646 @item set arm fpu @var{fputype}
17647 This command sets the ARM floating-point unit (FPU) type. The
17648 argument @var{fputype} can be one of these:
17652 Determine the FPU type by querying the OS ABI.
17654 Software FPU, with mixed-endian doubles on little-endian ARM
17657 GCC-compiled FPA co-processor.
17659 Software FPU with pure-endian doubles.
17665 Show the current type of the FPU.
17668 This command forces @value{GDBN} to use the specified ABI.
17671 Show the currently used ABI.
17673 @item set arm fallback-mode (arm|thumb|auto)
17674 @value{GDBN} uses the symbol table, when available, to determine
17675 whether instructions are ARM or Thumb. This command controls
17676 @value{GDBN}'s default behavior when the symbol table is not
17677 available. The default is @samp{auto}, which causes @value{GDBN} to
17678 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17681 @item show arm fallback-mode
17682 Show the current fallback instruction mode.
17684 @item set arm force-mode (arm|thumb|auto)
17685 This command overrides use of the symbol table to determine whether
17686 instructions are ARM or Thumb. The default is @samp{auto}, which
17687 causes @value{GDBN} to use the symbol table and then the setting
17688 of @samp{set arm fallback-mode}.
17690 @item show arm force-mode
17691 Show the current forced instruction mode.
17693 @item set debug arm
17694 Toggle whether to display ARM-specific debugging messages from the ARM
17695 target support subsystem.
17697 @item show debug arm
17698 Show whether ARM-specific debugging messages are enabled.
17701 The following commands are available when an ARM target is debugged
17702 using the RDI interface:
17705 @item rdilogfile @r{[}@var{file}@r{]}
17707 @cindex ADP (Angel Debugger Protocol) logging
17708 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17709 With an argument, sets the log file to the specified @var{file}. With
17710 no argument, show the current log file name. The default log file is
17713 @item rdilogenable @r{[}@var{arg}@r{]}
17714 @kindex rdilogenable
17715 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17716 enables logging, with an argument 0 or @code{"no"} disables it. With
17717 no arguments displays the current setting. When logging is enabled,
17718 ADP packets exchanged between @value{GDBN} and the RDI target device
17719 are logged to a file.
17721 @item set rdiromatzero
17722 @kindex set rdiromatzero
17723 @cindex ROM at zero address, RDI
17724 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17725 vector catching is disabled, so that zero address can be used. If off
17726 (the default), vector catching is enabled. For this command to take
17727 effect, it needs to be invoked prior to the @code{target rdi} command.
17729 @item show rdiromatzero
17730 @kindex show rdiromatzero
17731 Show the current setting of ROM at zero address.
17733 @item set rdiheartbeat
17734 @kindex set rdiheartbeat
17735 @cindex RDI heartbeat
17736 Enable or disable RDI heartbeat packets. It is not recommended to
17737 turn on this option, since it confuses ARM and EPI JTAG interface, as
17738 well as the Angel monitor.
17740 @item show rdiheartbeat
17741 @kindex show rdiheartbeat
17742 Show the setting of RDI heartbeat packets.
17746 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17747 The @value{GDBN} ARM simulator accepts the following optional arguments.
17750 @item --swi-support=@var{type}
17751 Tell the simulator which SWI interfaces to support.
17752 @var{type} may be a comma separated list of the following values.
17753 The default value is @code{all}.
17766 @subsection Renesas M32R/D and M32R/SDI
17769 @kindex target m32r
17770 @item target m32r @var{dev}
17771 Renesas M32R/D ROM monitor.
17773 @kindex target m32rsdi
17774 @item target m32rsdi @var{dev}
17775 Renesas M32R SDI server, connected via parallel port to the board.
17778 The following @value{GDBN} commands are specific to the M32R monitor:
17781 @item set download-path @var{path}
17782 @kindex set download-path
17783 @cindex find downloadable @sc{srec} files (M32R)
17784 Set the default path for finding downloadable @sc{srec} files.
17786 @item show download-path
17787 @kindex show download-path
17788 Show the default path for downloadable @sc{srec} files.
17790 @item set board-address @var{addr}
17791 @kindex set board-address
17792 @cindex M32-EVA target board address
17793 Set the IP address for the M32R-EVA target board.
17795 @item show board-address
17796 @kindex show board-address
17797 Show the current IP address of the target board.
17799 @item set server-address @var{addr}
17800 @kindex set server-address
17801 @cindex download server address (M32R)
17802 Set the IP address for the download server, which is the @value{GDBN}'s
17805 @item show server-address
17806 @kindex show server-address
17807 Display the IP address of the download server.
17809 @item upload @r{[}@var{file}@r{]}
17810 @kindex upload@r{, M32R}
17811 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17812 upload capability. If no @var{file} argument is given, the current
17813 executable file is uploaded.
17815 @item tload @r{[}@var{file}@r{]}
17816 @kindex tload@r{, M32R}
17817 Test the @code{upload} command.
17820 The following commands are available for M32R/SDI:
17825 @cindex reset SDI connection, M32R
17826 This command resets the SDI connection.
17830 This command shows the SDI connection status.
17833 @kindex debug_chaos
17834 @cindex M32R/Chaos debugging
17835 Instructs the remote that M32R/Chaos debugging is to be used.
17837 @item use_debug_dma
17838 @kindex use_debug_dma
17839 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17842 @kindex use_mon_code
17843 Instructs the remote to use the MON_CODE method of accessing memory.
17846 @kindex use_ib_break
17847 Instructs the remote to set breakpoints by IB break.
17849 @item use_dbt_break
17850 @kindex use_dbt_break
17851 Instructs the remote to set breakpoints by DBT.
17857 The Motorola m68k configuration includes ColdFire support, and a
17858 target command for the following ROM monitor.
17862 @kindex target dbug
17863 @item target dbug @var{dev}
17864 dBUG ROM monitor for Motorola ColdFire.
17869 @subsection MicroBlaze
17870 @cindex Xilinx MicroBlaze
17871 @cindex XMD, Xilinx Microprocessor Debugger
17873 The MicroBlaze is a soft-core processor supported on various Xilinx
17874 FPGAs, such as Spartan or Virtex series. Boards with these processors
17875 usually have JTAG ports which connect to a host system running the Xilinx
17876 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17877 This host system is used to download the configuration bitstream to
17878 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17879 communicates with the target board using the JTAG interface and
17880 presents a @code{gdbserver} interface to the board. By default
17881 @code{xmd} uses port @code{1234}. (While it is possible to change
17882 this default port, it requires the use of undocumented @code{xmd}
17883 commands. Contact Xilinx support if you need to do this.)
17885 Use these GDB commands to connect to the MicroBlaze target processor.
17888 @item target remote :1234
17889 Use this command to connect to the target if you are running @value{GDBN}
17890 on the same system as @code{xmd}.
17892 @item target remote @var{xmd-host}:1234
17893 Use this command to connect to the target if it is connected to @code{xmd}
17894 running on a different system named @var{xmd-host}.
17897 Use this command to download a program to the MicroBlaze target.
17899 @item set debug microblaze @var{n}
17900 Enable MicroBlaze-specific debugging messages if non-zero.
17902 @item show debug microblaze @var{n}
17903 Show MicroBlaze-specific debugging level.
17906 @node MIPS Embedded
17907 @subsection MIPS Embedded
17909 @cindex MIPS boards
17910 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17911 MIPS board attached to a serial line. This is available when
17912 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17915 Use these @value{GDBN} commands to specify the connection to your target board:
17918 @item target mips @var{port}
17919 @kindex target mips @var{port}
17920 To run a program on the board, start up @code{@value{GDBP}} with the
17921 name of your program as the argument. To connect to the board, use the
17922 command @samp{target mips @var{port}}, where @var{port} is the name of
17923 the serial port connected to the board. If the program has not already
17924 been downloaded to the board, you may use the @code{load} command to
17925 download it. You can then use all the usual @value{GDBN} commands.
17927 For example, this sequence connects to the target board through a serial
17928 port, and loads and runs a program called @var{prog} through the
17932 host$ @value{GDBP} @var{prog}
17933 @value{GDBN} is free software and @dots{}
17934 (@value{GDBP}) target mips /dev/ttyb
17935 (@value{GDBP}) load @var{prog}
17939 @item target mips @var{hostname}:@var{portnumber}
17940 On some @value{GDBN} host configurations, you can specify a TCP
17941 connection (for instance, to a serial line managed by a terminal
17942 concentrator) instead of a serial port, using the syntax
17943 @samp{@var{hostname}:@var{portnumber}}.
17945 @item target pmon @var{port}
17946 @kindex target pmon @var{port}
17949 @item target ddb @var{port}
17950 @kindex target ddb @var{port}
17951 NEC's DDB variant of PMON for Vr4300.
17953 @item target lsi @var{port}
17954 @kindex target lsi @var{port}
17955 LSI variant of PMON.
17957 @kindex target r3900
17958 @item target r3900 @var{dev}
17959 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17961 @kindex target array
17962 @item target array @var{dev}
17963 Array Tech LSI33K RAID controller board.
17969 @value{GDBN} also supports these special commands for MIPS targets:
17972 @item set mipsfpu double
17973 @itemx set mipsfpu single
17974 @itemx set mipsfpu none
17975 @itemx set mipsfpu auto
17976 @itemx show mipsfpu
17977 @kindex set mipsfpu
17978 @kindex show mipsfpu
17979 @cindex MIPS remote floating point
17980 @cindex floating point, MIPS remote
17981 If your target board does not support the MIPS floating point
17982 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17983 need this, you may wish to put the command in your @value{GDBN} init
17984 file). This tells @value{GDBN} how to find the return value of
17985 functions which return floating point values. It also allows
17986 @value{GDBN} to avoid saving the floating point registers when calling
17987 functions on the board. If you are using a floating point coprocessor
17988 with only single precision floating point support, as on the @sc{r4650}
17989 processor, use the command @samp{set mipsfpu single}. The default
17990 double precision floating point coprocessor may be selected using
17991 @samp{set mipsfpu double}.
17993 In previous versions the only choices were double precision or no
17994 floating point, so @samp{set mipsfpu on} will select double precision
17995 and @samp{set mipsfpu off} will select no floating point.
17997 As usual, you can inquire about the @code{mipsfpu} variable with
17998 @samp{show mipsfpu}.
18000 @item set timeout @var{seconds}
18001 @itemx set retransmit-timeout @var{seconds}
18002 @itemx show timeout
18003 @itemx show retransmit-timeout
18004 @cindex @code{timeout}, MIPS protocol
18005 @cindex @code{retransmit-timeout}, MIPS protocol
18006 @kindex set timeout
18007 @kindex show timeout
18008 @kindex set retransmit-timeout
18009 @kindex show retransmit-timeout
18010 You can control the timeout used while waiting for a packet, in the MIPS
18011 remote protocol, with the @code{set timeout @var{seconds}} command. The
18012 default is 5 seconds. Similarly, you can control the timeout used while
18013 waiting for an acknowledgment of a packet with the @code{set
18014 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18015 You can inspect both values with @code{show timeout} and @code{show
18016 retransmit-timeout}. (These commands are @emph{only} available when
18017 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18019 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18020 is waiting for your program to stop. In that case, @value{GDBN} waits
18021 forever because it has no way of knowing how long the program is going
18022 to run before stopping.
18024 @item set syn-garbage-limit @var{num}
18025 @kindex set syn-garbage-limit@r{, MIPS remote}
18026 @cindex synchronize with remote MIPS target
18027 Limit the maximum number of characters @value{GDBN} should ignore when
18028 it tries to synchronize with the remote target. The default is 10
18029 characters. Setting the limit to -1 means there's no limit.
18031 @item show syn-garbage-limit
18032 @kindex show syn-garbage-limit@r{, MIPS remote}
18033 Show the current limit on the number of characters to ignore when
18034 trying to synchronize with the remote system.
18036 @item set monitor-prompt @var{prompt}
18037 @kindex set monitor-prompt@r{, MIPS remote}
18038 @cindex remote monitor prompt
18039 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18040 remote monitor. The default depends on the target:
18050 @item show monitor-prompt
18051 @kindex show monitor-prompt@r{, MIPS remote}
18052 Show the current strings @value{GDBN} expects as the prompt from the
18055 @item set monitor-warnings
18056 @kindex set monitor-warnings@r{, MIPS remote}
18057 Enable or disable monitor warnings about hardware breakpoints. This
18058 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18059 display warning messages whose codes are returned by the @code{lsi}
18060 PMON monitor for breakpoint commands.
18062 @item show monitor-warnings
18063 @kindex show monitor-warnings@r{, MIPS remote}
18064 Show the current setting of printing monitor warnings.
18066 @item pmon @var{command}
18067 @kindex pmon@r{, MIPS remote}
18068 @cindex send PMON command
18069 This command allows sending an arbitrary @var{command} string to the
18070 monitor. The monitor must be in debug mode for this to work.
18073 @node OpenRISC 1000
18074 @subsection OpenRISC 1000
18075 @cindex OpenRISC 1000
18077 @cindex or1k boards
18078 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18079 about platform and commands.
18083 @kindex target jtag
18084 @item target jtag jtag://@var{host}:@var{port}
18086 Connects to remote JTAG server.
18087 JTAG remote server can be either an or1ksim or JTAG server,
18088 connected via parallel port to the board.
18090 Example: @code{target jtag jtag://localhost:9999}
18093 @item or1ksim @var{command}
18094 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18095 Simulator, proprietary commands can be executed.
18097 @kindex info or1k spr
18098 @item info or1k spr
18099 Displays spr groups.
18101 @item info or1k spr @var{group}
18102 @itemx info or1k spr @var{groupno}
18103 Displays register names in selected group.
18105 @item info or1k spr @var{group} @var{register}
18106 @itemx info or1k spr @var{register}
18107 @itemx info or1k spr @var{groupno} @var{registerno}
18108 @itemx info or1k spr @var{registerno}
18109 Shows information about specified spr register.
18112 @item spr @var{group} @var{register} @var{value}
18113 @itemx spr @var{register @var{value}}
18114 @itemx spr @var{groupno} @var{registerno @var{value}}
18115 @itemx spr @var{registerno @var{value}}
18116 Writes @var{value} to specified spr register.
18119 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18120 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18121 program execution and is thus much faster. Hardware breakpoints/watchpoint
18122 triggers can be set using:
18125 Load effective address/data
18127 Store effective address/data
18129 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18134 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18135 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18137 @code{htrace} commands:
18138 @cindex OpenRISC 1000 htrace
18141 @item hwatch @var{conditional}
18142 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18143 or Data. For example:
18145 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18147 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18151 Display information about current HW trace configuration.
18153 @item htrace trigger @var{conditional}
18154 Set starting criteria for HW trace.
18156 @item htrace qualifier @var{conditional}
18157 Set acquisition qualifier for HW trace.
18159 @item htrace stop @var{conditional}
18160 Set HW trace stopping criteria.
18162 @item htrace record [@var{data}]*
18163 Selects the data to be recorded, when qualifier is met and HW trace was
18166 @item htrace enable
18167 @itemx htrace disable
18168 Enables/disables the HW trace.
18170 @item htrace rewind [@var{filename}]
18171 Clears currently recorded trace data.
18173 If filename is specified, new trace file is made and any newly collected data
18174 will be written there.
18176 @item htrace print [@var{start} [@var{len}]]
18177 Prints trace buffer, using current record configuration.
18179 @item htrace mode continuous
18180 Set continuous trace mode.
18182 @item htrace mode suspend
18183 Set suspend trace mode.
18187 @node PowerPC Embedded
18188 @subsection PowerPC Embedded
18190 @value{GDBN} provides the following PowerPC-specific commands:
18193 @kindex set powerpc
18194 @item set powerpc soft-float
18195 @itemx show powerpc soft-float
18196 Force @value{GDBN} to use (or not use) a software floating point calling
18197 convention. By default, @value{GDBN} selects the calling convention based
18198 on the selected architecture and the provided executable file.
18200 @item set powerpc vector-abi
18201 @itemx show powerpc vector-abi
18202 Force @value{GDBN} to use the specified calling convention for vector
18203 arguments and return values. The valid options are @samp{auto};
18204 @samp{generic}, to avoid vector registers even if they are present;
18205 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18206 registers. By default, @value{GDBN} selects the calling convention
18207 based on the selected architecture and the provided executable file.
18209 @kindex target dink32
18210 @item target dink32 @var{dev}
18211 DINK32 ROM monitor.
18213 @kindex target ppcbug
18214 @item target ppcbug @var{dev}
18215 @kindex target ppcbug1
18216 @item target ppcbug1 @var{dev}
18217 PPCBUG ROM monitor for PowerPC.
18220 @item target sds @var{dev}
18221 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18224 @cindex SDS protocol
18225 The following commands specific to the SDS protocol are supported
18229 @item set sdstimeout @var{nsec}
18230 @kindex set sdstimeout
18231 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18232 default is 2 seconds.
18234 @item show sdstimeout
18235 @kindex show sdstimeout
18236 Show the current value of the SDS timeout.
18238 @item sds @var{command}
18239 @kindex sds@r{, a command}
18240 Send the specified @var{command} string to the SDS monitor.
18245 @subsection HP PA Embedded
18249 @kindex target op50n
18250 @item target op50n @var{dev}
18251 OP50N monitor, running on an OKI HPPA board.
18253 @kindex target w89k
18254 @item target w89k @var{dev}
18255 W89K monitor, running on a Winbond HPPA board.
18260 @subsection Tsqware Sparclet
18264 @value{GDBN} enables developers to debug tasks running on
18265 Sparclet targets from a Unix host.
18266 @value{GDBN} uses code that runs on
18267 both the Unix host and on the Sparclet target. The program
18268 @code{@value{GDBP}} is installed and executed on the Unix host.
18271 @item remotetimeout @var{args}
18272 @kindex remotetimeout
18273 @value{GDBN} supports the option @code{remotetimeout}.
18274 This option is set by the user, and @var{args} represents the number of
18275 seconds @value{GDBN} waits for responses.
18278 @cindex compiling, on Sparclet
18279 When compiling for debugging, include the options @samp{-g} to get debug
18280 information and @samp{-Ttext} to relocate the program to where you wish to
18281 load it on the target. You may also want to add the options @samp{-n} or
18282 @samp{-N} in order to reduce the size of the sections. Example:
18285 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18288 You can use @code{objdump} to verify that the addresses are what you intended:
18291 sparclet-aout-objdump --headers --syms prog
18294 @cindex running, on Sparclet
18296 your Unix execution search path to find @value{GDBN}, you are ready to
18297 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18298 (or @code{sparclet-aout-gdb}, depending on your installation).
18300 @value{GDBN} comes up showing the prompt:
18307 * Sparclet File:: Setting the file to debug
18308 * Sparclet Connection:: Connecting to Sparclet
18309 * Sparclet Download:: Sparclet download
18310 * Sparclet Execution:: Running and debugging
18313 @node Sparclet File
18314 @subsubsection Setting File to Debug
18316 The @value{GDBN} command @code{file} lets you choose with program to debug.
18319 (gdbslet) file prog
18323 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18324 @value{GDBN} locates
18325 the file by searching the directories listed in the command search
18327 If the file was compiled with debug information (option @samp{-g}), source
18328 files will be searched as well.
18329 @value{GDBN} locates
18330 the source files by searching the directories listed in the directory search
18331 path (@pxref{Environment, ,Your Program's Environment}).
18333 to find a file, it displays a message such as:
18336 prog: No such file or directory.
18339 When this happens, add the appropriate directories to the search paths with
18340 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18341 @code{target} command again.
18343 @node Sparclet Connection
18344 @subsubsection Connecting to Sparclet
18346 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18347 To connect to a target on serial port ``@code{ttya}'', type:
18350 (gdbslet) target sparclet /dev/ttya
18351 Remote target sparclet connected to /dev/ttya
18352 main () at ../prog.c:3
18356 @value{GDBN} displays messages like these:
18362 @node Sparclet Download
18363 @subsubsection Sparclet Download
18365 @cindex download to Sparclet
18366 Once connected to the Sparclet target,
18367 you can use the @value{GDBN}
18368 @code{load} command to download the file from the host to the target.
18369 The file name and load offset should be given as arguments to the @code{load}
18371 Since the file format is aout, the program must be loaded to the starting
18372 address. You can use @code{objdump} to find out what this value is. The load
18373 offset is an offset which is added to the VMA (virtual memory address)
18374 of each of the file's sections.
18375 For instance, if the program
18376 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18377 and bss at 0x12010170, in @value{GDBN}, type:
18380 (gdbslet) load prog 0x12010000
18381 Loading section .text, size 0xdb0 vma 0x12010000
18384 If the code is loaded at a different address then what the program was linked
18385 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18386 to tell @value{GDBN} where to map the symbol table.
18388 @node Sparclet Execution
18389 @subsubsection Running and Debugging
18391 @cindex running and debugging Sparclet programs
18392 You can now begin debugging the task using @value{GDBN}'s execution control
18393 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18394 manual for the list of commands.
18398 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18400 Starting program: prog
18401 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18402 3 char *symarg = 0;
18404 4 char *execarg = "hello!";
18409 @subsection Fujitsu Sparclite
18413 @kindex target sparclite
18414 @item target sparclite @var{dev}
18415 Fujitsu sparclite boards, used only for the purpose of loading.
18416 You must use an additional command to debug the program.
18417 For example: target remote @var{dev} using @value{GDBN} standard
18423 @subsection Zilog Z8000
18426 @cindex simulator, Z8000
18427 @cindex Zilog Z8000 simulator
18429 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18432 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18433 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18434 segmented variant). The simulator recognizes which architecture is
18435 appropriate by inspecting the object code.
18438 @item target sim @var{args}
18440 @kindex target sim@r{, with Z8000}
18441 Debug programs on a simulated CPU. If the simulator supports setup
18442 options, specify them via @var{args}.
18446 After specifying this target, you can debug programs for the simulated
18447 CPU in the same style as programs for your host computer; use the
18448 @code{file} command to load a new program image, the @code{run} command
18449 to run your program, and so on.
18451 As well as making available all the usual machine registers
18452 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18453 additional items of information as specially named registers:
18458 Counts clock-ticks in the simulator.
18461 Counts instructions run in the simulator.
18464 Execution time in 60ths of a second.
18468 You can refer to these values in @value{GDBN} expressions with the usual
18469 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18470 conditional breakpoint that suspends only after at least 5000
18471 simulated clock ticks.
18474 @subsection Atmel AVR
18477 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18478 following AVR-specific commands:
18481 @item info io_registers
18482 @kindex info io_registers@r{, AVR}
18483 @cindex I/O registers (Atmel AVR)
18484 This command displays information about the AVR I/O registers. For
18485 each register, @value{GDBN} prints its number and value.
18492 When configured for debugging CRIS, @value{GDBN} provides the
18493 following CRIS-specific commands:
18496 @item set cris-version @var{ver}
18497 @cindex CRIS version
18498 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18499 The CRIS version affects register names and sizes. This command is useful in
18500 case autodetection of the CRIS version fails.
18502 @item show cris-version
18503 Show the current CRIS version.
18505 @item set cris-dwarf2-cfi
18506 @cindex DWARF-2 CFI and CRIS
18507 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18508 Change to @samp{off} when using @code{gcc-cris} whose version is below
18511 @item show cris-dwarf2-cfi
18512 Show the current state of using DWARF-2 CFI.
18514 @item set cris-mode @var{mode}
18516 Set the current CRIS mode to @var{mode}. It should only be changed when
18517 debugging in guru mode, in which case it should be set to
18518 @samp{guru} (the default is @samp{normal}).
18520 @item show cris-mode
18521 Show the current CRIS mode.
18525 @subsection Renesas Super-H
18528 For the Renesas Super-H processor, @value{GDBN} provides these
18533 @kindex regs@r{, Super-H}
18534 Show the values of all Super-H registers.
18536 @item set sh calling-convention @var{convention}
18537 @kindex set sh calling-convention
18538 Set the calling-convention used when calling functions from @value{GDBN}.
18539 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18540 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18541 convention. If the DWARF-2 information of the called function specifies
18542 that the function follows the Renesas calling convention, the function
18543 is called using the Renesas calling convention. If the calling convention
18544 is set to @samp{renesas}, the Renesas calling convention is always used,
18545 regardless of the DWARF-2 information. This can be used to override the
18546 default of @samp{gcc} if debug information is missing, or the compiler
18547 does not emit the DWARF-2 calling convention entry for a function.
18549 @item show sh calling-convention
18550 @kindex show sh calling-convention
18551 Show the current calling convention setting.
18556 @node Architectures
18557 @section Architectures
18559 This section describes characteristics of architectures that affect
18560 all uses of @value{GDBN} with the architecture, both native and cross.
18567 * HPPA:: HP PA architecture
18568 * SPU:: Cell Broadband Engine SPU architecture
18573 @subsection x86 Architecture-specific Issues
18576 @item set struct-convention @var{mode}
18577 @kindex set struct-convention
18578 @cindex struct return convention
18579 @cindex struct/union returned in registers
18580 Set the convention used by the inferior to return @code{struct}s and
18581 @code{union}s from functions to @var{mode}. Possible values of
18582 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18583 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18584 are returned on the stack, while @code{"reg"} means that a
18585 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18586 be returned in a register.
18588 @item show struct-convention
18589 @kindex show struct-convention
18590 Show the current setting of the convention to return @code{struct}s
18599 @kindex set rstack_high_address
18600 @cindex AMD 29K register stack
18601 @cindex register stack, AMD29K
18602 @item set rstack_high_address @var{address}
18603 On AMD 29000 family processors, registers are saved in a separate
18604 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18605 extent of this stack. Normally, @value{GDBN} just assumes that the
18606 stack is ``large enough''. This may result in @value{GDBN} referencing
18607 memory locations that do not exist. If necessary, you can get around
18608 this problem by specifying the ending address of the register stack with
18609 the @code{set rstack_high_address} command. The argument should be an
18610 address, which you probably want to precede with @samp{0x} to specify in
18613 @kindex show rstack_high_address
18614 @item show rstack_high_address
18615 Display the current limit of the register stack, on AMD 29000 family
18623 See the following section.
18628 @cindex stack on Alpha
18629 @cindex stack on MIPS
18630 @cindex Alpha stack
18632 Alpha- and MIPS-based computers use an unusual stack frame, which
18633 sometimes requires @value{GDBN} to search backward in the object code to
18634 find the beginning of a function.
18636 @cindex response time, MIPS debugging
18637 To improve response time (especially for embedded applications, where
18638 @value{GDBN} may be restricted to a slow serial line for this search)
18639 you may want to limit the size of this search, using one of these
18643 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18644 @item set heuristic-fence-post @var{limit}
18645 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18646 search for the beginning of a function. A value of @var{0} (the
18647 default) means there is no limit. However, except for @var{0}, the
18648 larger the limit the more bytes @code{heuristic-fence-post} must search
18649 and therefore the longer it takes to run. You should only need to use
18650 this command when debugging a stripped executable.
18652 @item show heuristic-fence-post
18653 Display the current limit.
18657 These commands are available @emph{only} when @value{GDBN} is configured
18658 for debugging programs on Alpha or MIPS processors.
18660 Several MIPS-specific commands are available when debugging MIPS
18664 @item set mips abi @var{arg}
18665 @kindex set mips abi
18666 @cindex set ABI for MIPS
18667 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18668 values of @var{arg} are:
18672 The default ABI associated with the current binary (this is the
18683 @item show mips abi
18684 @kindex show mips abi
18685 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18688 @itemx show mipsfpu
18689 @xref{MIPS Embedded, set mipsfpu}.
18691 @item set mips mask-address @var{arg}
18692 @kindex set mips mask-address
18693 @cindex MIPS addresses, masking
18694 This command determines whether the most-significant 32 bits of 64-bit
18695 MIPS addresses are masked off. The argument @var{arg} can be
18696 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18697 setting, which lets @value{GDBN} determine the correct value.
18699 @item show mips mask-address
18700 @kindex show mips mask-address
18701 Show whether the upper 32 bits of MIPS addresses are masked off or
18704 @item set remote-mips64-transfers-32bit-regs
18705 @kindex set remote-mips64-transfers-32bit-regs
18706 This command controls compatibility with 64-bit MIPS targets that
18707 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18708 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18709 and 64 bits for other registers, set this option to @samp{on}.
18711 @item show remote-mips64-transfers-32bit-regs
18712 @kindex show remote-mips64-transfers-32bit-regs
18713 Show the current setting of compatibility with older MIPS 64 targets.
18715 @item set debug mips
18716 @kindex set debug mips
18717 This command turns on and off debugging messages for the MIPS-specific
18718 target code in @value{GDBN}.
18720 @item show debug mips
18721 @kindex show debug mips
18722 Show the current setting of MIPS debugging messages.
18728 @cindex HPPA support
18730 When @value{GDBN} is debugging the HP PA architecture, it provides the
18731 following special commands:
18734 @item set debug hppa
18735 @kindex set debug hppa
18736 This command determines whether HPPA architecture-specific debugging
18737 messages are to be displayed.
18739 @item show debug hppa
18740 Show whether HPPA debugging messages are displayed.
18742 @item maint print unwind @var{address}
18743 @kindex maint print unwind@r{, HPPA}
18744 This command displays the contents of the unwind table entry at the
18745 given @var{address}.
18751 @subsection Cell Broadband Engine SPU architecture
18752 @cindex Cell Broadband Engine
18755 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18756 it provides the following special commands:
18759 @item info spu event
18761 Display SPU event facility status. Shows current event mask
18762 and pending event status.
18764 @item info spu signal
18765 Display SPU signal notification facility status. Shows pending
18766 signal-control word and signal notification mode of both signal
18767 notification channels.
18769 @item info spu mailbox
18770 Display SPU mailbox facility status. Shows all pending entries,
18771 in order of processing, in each of the SPU Write Outbound,
18772 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18775 Display MFC DMA status. Shows all pending commands in the MFC
18776 DMA queue. For each entry, opcode, tag, class IDs, effective
18777 and local store addresses and transfer size are shown.
18779 @item info spu proxydma
18780 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18781 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18782 and local store addresses and transfer size are shown.
18786 When @value{GDBN} is debugging a combined PowerPC/SPU application
18787 on the Cell Broadband Engine, it provides in addition the following
18791 @item set spu stop-on-load @var{arg}
18793 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18794 will give control to the user when a new SPE thread enters its @code{main}
18795 function. The default is @code{off}.
18797 @item show spu stop-on-load
18799 Show whether to stop for new SPE threads.
18801 @item set spu auto-flush-cache @var{arg}
18802 Set whether to automatically flush the software-managed cache. When set to
18803 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18804 cache to be flushed whenever SPE execution stops. This provides a consistent
18805 view of PowerPC memory that is accessed via the cache. If an application
18806 does not use the software-managed cache, this option has no effect.
18808 @item show spu auto-flush-cache
18809 Show whether to automatically flush the software-managed cache.
18814 @subsection PowerPC
18815 @cindex PowerPC architecture
18817 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18818 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18819 numbers stored in the floating point registers. These values must be stored
18820 in two consecutive registers, always starting at an even register like
18821 @code{f0} or @code{f2}.
18823 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18824 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18825 @code{f2} and @code{f3} for @code{$dl1} and so on.
18827 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18828 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18831 @node Controlling GDB
18832 @chapter Controlling @value{GDBN}
18834 You can alter the way @value{GDBN} interacts with you by using the
18835 @code{set} command. For commands controlling how @value{GDBN} displays
18836 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18841 * Editing:: Command editing
18842 * Command History:: Command history
18843 * Screen Size:: Screen size
18844 * Numbers:: Numbers
18845 * ABI:: Configuring the current ABI
18846 * Messages/Warnings:: Optional warnings and messages
18847 * Debugging Output:: Optional messages about internal happenings
18848 * Other Misc Settings:: Other Miscellaneous Settings
18856 @value{GDBN} indicates its readiness to read a command by printing a string
18857 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18858 can change the prompt string with the @code{set prompt} command. For
18859 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18860 the prompt in one of the @value{GDBN} sessions so that you can always tell
18861 which one you are talking to.
18863 @emph{Note:} @code{set prompt} does not add a space for you after the
18864 prompt you set. This allows you to set a prompt which ends in a space
18865 or a prompt that does not.
18869 @item set prompt @var{newprompt}
18870 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18872 @kindex show prompt
18874 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18878 @section Command Editing
18880 @cindex command line editing
18882 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18883 @sc{gnu} library provides consistent behavior for programs which provide a
18884 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18885 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18886 substitution, and a storage and recall of command history across
18887 debugging sessions.
18889 You may control the behavior of command line editing in @value{GDBN} with the
18890 command @code{set}.
18893 @kindex set editing
18896 @itemx set editing on
18897 Enable command line editing (enabled by default).
18899 @item set editing off
18900 Disable command line editing.
18902 @kindex show editing
18904 Show whether command line editing is enabled.
18907 @xref{Command Line Editing}, for more details about the Readline
18908 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18909 encouraged to read that chapter.
18911 @node Command History
18912 @section Command History
18913 @cindex command history
18915 @value{GDBN} can keep track of the commands you type during your
18916 debugging sessions, so that you can be certain of precisely what
18917 happened. Use these commands to manage the @value{GDBN} command
18920 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18921 package, to provide the history facility. @xref{Using History
18922 Interactively}, for the detailed description of the History library.
18924 To issue a command to @value{GDBN} without affecting certain aspects of
18925 the state which is seen by users, prefix it with @samp{server }
18926 (@pxref{Server Prefix}). This
18927 means that this command will not affect the command history, nor will it
18928 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18929 pressed on a line by itself.
18931 @cindex @code{server}, command prefix
18932 The server prefix does not affect the recording of values into the value
18933 history; to print a value without recording it into the value history,
18934 use the @code{output} command instead of the @code{print} command.
18936 Here is the description of @value{GDBN} commands related to command
18940 @cindex history substitution
18941 @cindex history file
18942 @kindex set history filename
18943 @cindex @env{GDBHISTFILE}, environment variable
18944 @item set history filename @var{fname}
18945 Set the name of the @value{GDBN} command history file to @var{fname}.
18946 This is the file where @value{GDBN} reads an initial command history
18947 list, and where it writes the command history from this session when it
18948 exits. You can access this list through history expansion or through
18949 the history command editing characters listed below. This file defaults
18950 to the value of the environment variable @code{GDBHISTFILE}, or to
18951 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18954 @cindex save command history
18955 @kindex set history save
18956 @item set history save
18957 @itemx set history save on
18958 Record command history in a file, whose name may be specified with the
18959 @code{set history filename} command. By default, this option is disabled.
18961 @item set history save off
18962 Stop recording command history in a file.
18964 @cindex history size
18965 @kindex set history size
18966 @cindex @env{HISTSIZE}, environment variable
18967 @item set history size @var{size}
18968 Set the number of commands which @value{GDBN} keeps in its history list.
18969 This defaults to the value of the environment variable
18970 @code{HISTSIZE}, or to 256 if this variable is not set.
18973 History expansion assigns special meaning to the character @kbd{!}.
18974 @xref{Event Designators}, for more details.
18976 @cindex history expansion, turn on/off
18977 Since @kbd{!} is also the logical not operator in C, history expansion
18978 is off by default. If you decide to enable history expansion with the
18979 @code{set history expansion on} command, you may sometimes need to
18980 follow @kbd{!} (when it is used as logical not, in an expression) with
18981 a space or a tab to prevent it from being expanded. The readline
18982 history facilities do not attempt substitution on the strings
18983 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18985 The commands to control history expansion are:
18988 @item set history expansion on
18989 @itemx set history expansion
18990 @kindex set history expansion
18991 Enable history expansion. History expansion is off by default.
18993 @item set history expansion off
18994 Disable history expansion.
18997 @kindex show history
18999 @itemx show history filename
19000 @itemx show history save
19001 @itemx show history size
19002 @itemx show history expansion
19003 These commands display the state of the @value{GDBN} history parameters.
19004 @code{show history} by itself displays all four states.
19009 @kindex show commands
19010 @cindex show last commands
19011 @cindex display command history
19012 @item show commands
19013 Display the last ten commands in the command history.
19015 @item show commands @var{n}
19016 Print ten commands centered on command number @var{n}.
19018 @item show commands +
19019 Print ten commands just after the commands last printed.
19023 @section Screen Size
19024 @cindex size of screen
19025 @cindex pauses in output
19027 Certain commands to @value{GDBN} may produce large amounts of
19028 information output to the screen. To help you read all of it,
19029 @value{GDBN} pauses and asks you for input at the end of each page of
19030 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19031 to discard the remaining output. Also, the screen width setting
19032 determines when to wrap lines of output. Depending on what is being
19033 printed, @value{GDBN} tries to break the line at a readable place,
19034 rather than simply letting it overflow onto the following line.
19036 Normally @value{GDBN} knows the size of the screen from the terminal
19037 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19038 together with the value of the @code{TERM} environment variable and the
19039 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19040 you can override it with the @code{set height} and @code{set
19047 @kindex show height
19048 @item set height @var{lpp}
19050 @itemx set width @var{cpl}
19052 These @code{set} commands specify a screen height of @var{lpp} lines and
19053 a screen width of @var{cpl} characters. The associated @code{show}
19054 commands display the current settings.
19056 If you specify a height of zero lines, @value{GDBN} does not pause during
19057 output no matter how long the output is. This is useful if output is to a
19058 file or to an editor buffer.
19060 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19061 from wrapping its output.
19063 @item set pagination on
19064 @itemx set pagination off
19065 @kindex set pagination
19066 Turn the output pagination on or off; the default is on. Turning
19067 pagination off is the alternative to @code{set height 0}. Note that
19068 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19069 Options, -batch}) also automatically disables pagination.
19071 @item show pagination
19072 @kindex show pagination
19073 Show the current pagination mode.
19078 @cindex number representation
19079 @cindex entering numbers
19081 You can always enter numbers in octal, decimal, or hexadecimal in
19082 @value{GDBN} by the usual conventions: octal numbers begin with
19083 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19084 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19085 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19086 10; likewise, the default display for numbers---when no particular
19087 format is specified---is base 10. You can change the default base for
19088 both input and output with the commands described below.
19091 @kindex set input-radix
19092 @item set input-radix @var{base}
19093 Set the default base for numeric input. Supported choices
19094 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19095 specified either unambiguously or using the current input radix; for
19099 set input-radix 012
19100 set input-radix 10.
19101 set input-radix 0xa
19105 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19106 leaves the input radix unchanged, no matter what it was, since
19107 @samp{10}, being without any leading or trailing signs of its base, is
19108 interpreted in the current radix. Thus, if the current radix is 16,
19109 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19112 @kindex set output-radix
19113 @item set output-radix @var{base}
19114 Set the default base for numeric display. Supported choices
19115 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19116 specified either unambiguously or using the current input radix.
19118 @kindex show input-radix
19119 @item show input-radix
19120 Display the current default base for numeric input.
19122 @kindex show output-radix
19123 @item show output-radix
19124 Display the current default base for numeric display.
19126 @item set radix @r{[}@var{base}@r{]}
19130 These commands set and show the default base for both input and output
19131 of numbers. @code{set radix} sets the radix of input and output to
19132 the same base; without an argument, it resets the radix back to its
19133 default value of 10.
19138 @section Configuring the Current ABI
19140 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19141 application automatically. However, sometimes you need to override its
19142 conclusions. Use these commands to manage @value{GDBN}'s view of the
19149 One @value{GDBN} configuration can debug binaries for multiple operating
19150 system targets, either via remote debugging or native emulation.
19151 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19152 but you can override its conclusion using the @code{set osabi} command.
19153 One example where this is useful is in debugging of binaries which use
19154 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19155 not have the same identifying marks that the standard C library for your
19160 Show the OS ABI currently in use.
19163 With no argument, show the list of registered available OS ABI's.
19165 @item set osabi @var{abi}
19166 Set the current OS ABI to @var{abi}.
19169 @cindex float promotion
19171 Generally, the way that an argument of type @code{float} is passed to a
19172 function depends on whether the function is prototyped. For a prototyped
19173 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19174 according to the architecture's convention for @code{float}. For unprototyped
19175 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19176 @code{double} and then passed.
19178 Unfortunately, some forms of debug information do not reliably indicate whether
19179 a function is prototyped. If @value{GDBN} calls a function that is not marked
19180 as prototyped, it consults @kbd{set coerce-float-to-double}.
19183 @kindex set coerce-float-to-double
19184 @item set coerce-float-to-double
19185 @itemx set coerce-float-to-double on
19186 Arguments of type @code{float} will be promoted to @code{double} when passed
19187 to an unprototyped function. This is the default setting.
19189 @item set coerce-float-to-double off
19190 Arguments of type @code{float} will be passed directly to unprototyped
19193 @kindex show coerce-float-to-double
19194 @item show coerce-float-to-double
19195 Show the current setting of promoting @code{float} to @code{double}.
19199 @kindex show cp-abi
19200 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19201 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19202 used to build your application. @value{GDBN} only fully supports
19203 programs with a single C@t{++} ABI; if your program contains code using
19204 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19205 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19206 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19207 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19208 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19209 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19214 Show the C@t{++} ABI currently in use.
19217 With no argument, show the list of supported C@t{++} ABI's.
19219 @item set cp-abi @var{abi}
19220 @itemx set cp-abi auto
19221 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19224 @node Messages/Warnings
19225 @section Optional Warnings and Messages
19227 @cindex verbose operation
19228 @cindex optional warnings
19229 By default, @value{GDBN} is silent about its inner workings. If you are
19230 running on a slow machine, you may want to use the @code{set verbose}
19231 command. This makes @value{GDBN} tell you when it does a lengthy
19232 internal operation, so you will not think it has crashed.
19234 Currently, the messages controlled by @code{set verbose} are those
19235 which announce that the symbol table for a source file is being read;
19236 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19239 @kindex set verbose
19240 @item set verbose on
19241 Enables @value{GDBN} output of certain informational messages.
19243 @item set verbose off
19244 Disables @value{GDBN} output of certain informational messages.
19246 @kindex show verbose
19248 Displays whether @code{set verbose} is on or off.
19251 By default, if @value{GDBN} encounters bugs in the symbol table of an
19252 object file, it is silent; but if you are debugging a compiler, you may
19253 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19258 @kindex set complaints
19259 @item set complaints @var{limit}
19260 Permits @value{GDBN} to output @var{limit} complaints about each type of
19261 unusual symbols before becoming silent about the problem. Set
19262 @var{limit} to zero to suppress all complaints; set it to a large number
19263 to prevent complaints from being suppressed.
19265 @kindex show complaints
19266 @item show complaints
19267 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19271 @anchor{confirmation requests}
19272 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19273 lot of stupid questions to confirm certain commands. For example, if
19274 you try to run a program which is already running:
19278 The program being debugged has been started already.
19279 Start it from the beginning? (y or n)
19282 If you are willing to unflinchingly face the consequences of your own
19283 commands, you can disable this ``feature'':
19287 @kindex set confirm
19289 @cindex confirmation
19290 @cindex stupid questions
19291 @item set confirm off
19292 Disables confirmation requests. Note that running @value{GDBN} with
19293 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19294 automatically disables confirmation requests.
19296 @item set confirm on
19297 Enables confirmation requests (the default).
19299 @kindex show confirm
19301 Displays state of confirmation requests.
19305 @cindex command tracing
19306 If you need to debug user-defined commands or sourced files you may find it
19307 useful to enable @dfn{command tracing}. In this mode each command will be
19308 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19309 quantity denoting the call depth of each command.
19312 @kindex set trace-commands
19313 @cindex command scripts, debugging
19314 @item set trace-commands on
19315 Enable command tracing.
19316 @item set trace-commands off
19317 Disable command tracing.
19318 @item show trace-commands
19319 Display the current state of command tracing.
19322 @node Debugging Output
19323 @section Optional Messages about Internal Happenings
19324 @cindex optional debugging messages
19326 @value{GDBN} has commands that enable optional debugging messages from
19327 various @value{GDBN} subsystems; normally these commands are of
19328 interest to @value{GDBN} maintainers, or when reporting a bug. This
19329 section documents those commands.
19332 @kindex set exec-done-display
19333 @item set exec-done-display
19334 Turns on or off the notification of asynchronous commands'
19335 completion. When on, @value{GDBN} will print a message when an
19336 asynchronous command finishes its execution. The default is off.
19337 @kindex show exec-done-display
19338 @item show exec-done-display
19339 Displays the current setting of asynchronous command completion
19342 @cindex gdbarch debugging info
19343 @cindex architecture debugging info
19344 @item set debug arch
19345 Turns on or off display of gdbarch debugging info. The default is off
19347 @item show debug arch
19348 Displays the current state of displaying gdbarch debugging info.
19349 @item set debug aix-thread
19350 @cindex AIX threads
19351 Display debugging messages about inner workings of the AIX thread
19353 @item show debug aix-thread
19354 Show the current state of AIX thread debugging info display.
19355 @item set debug dwarf2-die
19356 @cindex DWARF2 DIEs
19357 Dump DWARF2 DIEs after they are read in.
19358 The value is the number of nesting levels to print.
19359 A value of zero turns off the display.
19360 @item show debug dwarf2-die
19361 Show the current state of DWARF2 DIE debugging.
19362 @item set debug displaced
19363 @cindex displaced stepping debugging info
19364 Turns on or off display of @value{GDBN} debugging info for the
19365 displaced stepping support. The default is off.
19366 @item show debug displaced
19367 Displays the current state of displaying @value{GDBN} debugging info
19368 related to displaced stepping.
19369 @item set debug event
19370 @cindex event debugging info
19371 Turns on or off display of @value{GDBN} event debugging info. The
19373 @item show debug event
19374 Displays the current state of displaying @value{GDBN} event debugging
19376 @item set debug expression
19377 @cindex expression debugging info
19378 Turns on or off display of debugging info about @value{GDBN}
19379 expression parsing. The default is off.
19380 @item show debug expression
19381 Displays the current state of displaying debugging info about
19382 @value{GDBN} expression parsing.
19383 @item set debug frame
19384 @cindex frame debugging info
19385 Turns on or off display of @value{GDBN} frame debugging info. The
19387 @item show debug frame
19388 Displays the current state of displaying @value{GDBN} frame debugging
19390 @item set debug gnu-nat
19391 @cindex @sc{gnu}/Hurd debug messages
19392 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19393 @item show debug gnu-nat
19394 Show the current state of @sc{gnu}/Hurd debugging messages.
19395 @item set debug infrun
19396 @cindex inferior debugging info
19397 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19398 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19399 for implementing operations such as single-stepping the inferior.
19400 @item show debug infrun
19401 Displays the current state of @value{GDBN} inferior debugging.
19402 @item set debug lin-lwp
19403 @cindex @sc{gnu}/Linux LWP debug messages
19404 @cindex Linux lightweight processes
19405 Turns on or off debugging messages from the Linux LWP debug support.
19406 @item show debug lin-lwp
19407 Show the current state of Linux LWP debugging messages.
19408 @item set debug lin-lwp-async
19409 @cindex @sc{gnu}/Linux LWP async debug messages
19410 @cindex Linux lightweight processes
19411 Turns on or off debugging messages from the Linux LWP async debug support.
19412 @item show debug lin-lwp-async
19413 Show the current state of Linux LWP async debugging messages.
19414 @item set debug observer
19415 @cindex observer debugging info
19416 Turns on or off display of @value{GDBN} observer debugging. This
19417 includes info such as the notification of observable events.
19418 @item show debug observer
19419 Displays the current state of observer debugging.
19420 @item set debug overload
19421 @cindex C@t{++} overload debugging info
19422 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19423 info. This includes info such as ranking of functions, etc. The default
19425 @item show debug overload
19426 Displays the current state of displaying @value{GDBN} C@t{++} overload
19428 @cindex expression parser, debugging info
19429 @cindex debug expression parser
19430 @item set debug parser
19431 Turns on or off the display of expression parser debugging output.
19432 Internally, this sets the @code{yydebug} variable in the expression
19433 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19434 details. The default is off.
19435 @item show debug parser
19436 Show the current state of expression parser debugging.
19437 @cindex packets, reporting on stdout
19438 @cindex serial connections, debugging
19439 @cindex debug remote protocol
19440 @cindex remote protocol debugging
19441 @cindex display remote packets
19442 @item set debug remote
19443 Turns on or off display of reports on all packets sent back and forth across
19444 the serial line to the remote machine. The info is printed on the
19445 @value{GDBN} standard output stream. The default is off.
19446 @item show debug remote
19447 Displays the state of display of remote packets.
19448 @item set debug serial
19449 Turns on or off display of @value{GDBN} serial debugging info. The
19451 @item show debug serial
19452 Displays the current state of displaying @value{GDBN} serial debugging
19454 @item set debug solib-frv
19455 @cindex FR-V shared-library debugging
19456 Turns on or off debugging messages for FR-V shared-library code.
19457 @item show debug solib-frv
19458 Display the current state of FR-V shared-library code debugging
19460 @item set debug target
19461 @cindex target debugging info
19462 Turns on or off display of @value{GDBN} target debugging info. This info
19463 includes what is going on at the target level of GDB, as it happens. The
19464 default is 0. Set it to 1 to track events, and to 2 to also track the
19465 value of large memory transfers. Changes to this flag do not take effect
19466 until the next time you connect to a target or use the @code{run} command.
19467 @item show debug target
19468 Displays the current state of displaying @value{GDBN} target debugging
19470 @item set debug timestamp
19471 @cindex timestampping debugging info
19472 Turns on or off display of timestamps with @value{GDBN} debugging info.
19473 When enabled, seconds and microseconds are displayed before each debugging
19475 @item show debug timestamp
19476 Displays the current state of displaying timestamps with @value{GDBN}
19478 @item set debugvarobj
19479 @cindex variable object debugging info
19480 Turns on or off display of @value{GDBN} variable object debugging
19481 info. The default is off.
19482 @item show debugvarobj
19483 Displays the current state of displaying @value{GDBN} variable object
19485 @item set debug xml
19486 @cindex XML parser debugging
19487 Turns on or off debugging messages for built-in XML parsers.
19488 @item show debug xml
19489 Displays the current state of XML debugging messages.
19492 @node Other Misc Settings
19493 @section Other Miscellaneous Settings
19494 @cindex miscellaneous settings
19497 @kindex set interactive-mode
19498 @item set interactive-mode
19499 If @code{on}, forces @value{GDBN} to operate interactively.
19500 If @code{off}, forces @value{GDBN} to operate non-interactively,
19501 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19502 based on whether the debugger was started in a terminal or not.
19504 In the vast majority of cases, the debugger should be able to guess
19505 correctly which mode should be used. But this setting can be useful
19506 in certain specific cases, such as running a MinGW @value{GDBN}
19507 inside a cygwin window.
19509 @kindex show interactive-mode
19510 @item show interactive-mode
19511 Displays whether the debugger is operating in interactive mode or not.
19514 @node Extending GDB
19515 @chapter Extending @value{GDBN}
19516 @cindex extending GDB
19518 @value{GDBN} provides two mechanisms for extension. The first is based
19519 on composition of @value{GDBN} commands, and the second is based on the
19520 Python scripting language.
19522 To facilitate the use of these extensions, @value{GDBN} is capable
19523 of evaluating the contents of a file. When doing so, @value{GDBN}
19524 can recognize which scripting language is being used by looking at
19525 the filename extension. Files with an unrecognized filename extension
19526 are always treated as a @value{GDBN} Command Files.
19527 @xref{Command Files,, Command files}.
19529 You can control how @value{GDBN} evaluates these files with the following
19533 @kindex set script-extension
19534 @kindex show script-extension
19535 @item set script-extension off
19536 All scripts are always evaluated as @value{GDBN} Command Files.
19538 @item set script-extension soft
19539 The debugger determines the scripting language based on filename
19540 extension. If this scripting language is supported, @value{GDBN}
19541 evaluates the script using that language. Otherwise, it evaluates
19542 the file as a @value{GDBN} Command File.
19544 @item set script-extension strict
19545 The debugger determines the scripting language based on filename
19546 extension, and evaluates the script using that language. If the
19547 language is not supported, then the evaluation fails.
19549 @item show script-extension
19550 Display the current value of the @code{script-extension} option.
19555 * Sequences:: Canned Sequences of Commands
19556 * Python:: Scripting @value{GDBN} using Python
19560 @section Canned Sequences of Commands
19562 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19563 Command Lists}), @value{GDBN} provides two ways to store sequences of
19564 commands for execution as a unit: user-defined commands and command
19568 * Define:: How to define your own commands
19569 * Hooks:: Hooks for user-defined commands
19570 * Command Files:: How to write scripts of commands to be stored in a file
19571 * Output:: Commands for controlled output
19575 @subsection User-defined Commands
19577 @cindex user-defined command
19578 @cindex arguments, to user-defined commands
19579 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19580 which you assign a new name as a command. This is done with the
19581 @code{define} command. User commands may accept up to 10 arguments
19582 separated by whitespace. Arguments are accessed within the user command
19583 via @code{$arg0@dots{}$arg9}. A trivial example:
19587 print $arg0 + $arg1 + $arg2
19592 To execute the command use:
19599 This defines the command @code{adder}, which prints the sum of
19600 its three arguments. Note the arguments are text substitutions, so they may
19601 reference variables, use complex expressions, or even perform inferior
19604 @cindex argument count in user-defined commands
19605 @cindex how many arguments (user-defined commands)
19606 In addition, @code{$argc} may be used to find out how many arguments have
19607 been passed. This expands to a number in the range 0@dots{}10.
19612 print $arg0 + $arg1
19615 print $arg0 + $arg1 + $arg2
19623 @item define @var{commandname}
19624 Define a command named @var{commandname}. If there is already a command
19625 by that name, you are asked to confirm that you want to redefine it.
19626 @var{commandname} may be a bare command name consisting of letters,
19627 numbers, dashes, and underscores. It may also start with any predefined
19628 prefix command. For example, @samp{define target my-target} creates
19629 a user-defined @samp{target my-target} command.
19631 The definition of the command is made up of other @value{GDBN} command lines,
19632 which are given following the @code{define} command. The end of these
19633 commands is marked by a line containing @code{end}.
19636 @kindex end@r{ (user-defined commands)}
19637 @item document @var{commandname}
19638 Document the user-defined command @var{commandname}, so that it can be
19639 accessed by @code{help}. The command @var{commandname} must already be
19640 defined. This command reads lines of documentation just as @code{define}
19641 reads the lines of the command definition, ending with @code{end}.
19642 After the @code{document} command is finished, @code{help} on command
19643 @var{commandname} displays the documentation you have written.
19645 You may use the @code{document} command again to change the
19646 documentation of a command. Redefining the command with @code{define}
19647 does not change the documentation.
19649 @kindex dont-repeat
19650 @cindex don't repeat command
19652 Used inside a user-defined command, this tells @value{GDBN} that this
19653 command should not be repeated when the user hits @key{RET}
19654 (@pxref{Command Syntax, repeat last command}).
19656 @kindex help user-defined
19657 @item help user-defined
19658 List all user-defined commands, with the first line of the documentation
19663 @itemx show user @var{commandname}
19664 Display the @value{GDBN} commands used to define @var{commandname} (but
19665 not its documentation). If no @var{commandname} is given, display the
19666 definitions for all user-defined commands.
19668 @cindex infinite recursion in user-defined commands
19669 @kindex show max-user-call-depth
19670 @kindex set max-user-call-depth
19671 @item show max-user-call-depth
19672 @itemx set max-user-call-depth
19673 The value of @code{max-user-call-depth} controls how many recursion
19674 levels are allowed in user-defined commands before @value{GDBN} suspects an
19675 infinite recursion and aborts the command.
19678 In addition to the above commands, user-defined commands frequently
19679 use control flow commands, described in @ref{Command Files}.
19681 When user-defined commands are executed, the
19682 commands of the definition are not printed. An error in any command
19683 stops execution of the user-defined command.
19685 If used interactively, commands that would ask for confirmation proceed
19686 without asking when used inside a user-defined command. Many @value{GDBN}
19687 commands that normally print messages to say what they are doing omit the
19688 messages when used in a user-defined command.
19691 @subsection User-defined Command Hooks
19692 @cindex command hooks
19693 @cindex hooks, for commands
19694 @cindex hooks, pre-command
19697 You may define @dfn{hooks}, which are a special kind of user-defined
19698 command. Whenever you run the command @samp{foo}, if the user-defined
19699 command @samp{hook-foo} exists, it is executed (with no arguments)
19700 before that command.
19702 @cindex hooks, post-command
19704 A hook may also be defined which is run after the command you executed.
19705 Whenever you run the command @samp{foo}, if the user-defined command
19706 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19707 that command. Post-execution hooks may exist simultaneously with
19708 pre-execution hooks, for the same command.
19710 It is valid for a hook to call the command which it hooks. If this
19711 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19713 @c It would be nice if hookpost could be passed a parameter indicating
19714 @c if the command it hooks executed properly or not. FIXME!
19716 @kindex stop@r{, a pseudo-command}
19717 In addition, a pseudo-command, @samp{stop} exists. Defining
19718 (@samp{hook-stop}) makes the associated commands execute every time
19719 execution stops in your program: before breakpoint commands are run,
19720 displays are printed, or the stack frame is printed.
19722 For example, to ignore @code{SIGALRM} signals while
19723 single-stepping, but treat them normally during normal execution,
19728 handle SIGALRM nopass
19732 handle SIGALRM pass
19735 define hook-continue
19736 handle SIGALRM pass
19740 As a further example, to hook at the beginning and end of the @code{echo}
19741 command, and to add extra text to the beginning and end of the message,
19749 define hookpost-echo
19753 (@value{GDBP}) echo Hello World
19754 <<<---Hello World--->>>
19759 You can define a hook for any single-word command in @value{GDBN}, but
19760 not for command aliases; you should define a hook for the basic command
19761 name, e.g.@: @code{backtrace} rather than @code{bt}.
19762 @c FIXME! So how does Joe User discover whether a command is an alias
19764 You can hook a multi-word command by adding @code{hook-} or
19765 @code{hookpost-} to the last word of the command, e.g.@:
19766 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19768 If an error occurs during the execution of your hook, execution of
19769 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19770 (before the command that you actually typed had a chance to run).
19772 If you try to define a hook which does not match any known command, you
19773 get a warning from the @code{define} command.
19775 @node Command Files
19776 @subsection Command Files
19778 @cindex command files
19779 @cindex scripting commands
19780 A command file for @value{GDBN} is a text file made of lines that are
19781 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19782 also be included. An empty line in a command file does nothing; it
19783 does not mean to repeat the last command, as it would from the
19786 You can request the execution of a command file with the @code{source}
19787 command. Note that the @code{source} command is also used to evaluate
19788 scripts that are not Command Files. The exact behavior can be configured
19789 using the @code{script-extension} setting.
19790 @xref{Extending GDB,, Extending GDB}.
19794 @cindex execute commands from a file
19795 @item source [-s] [-v] @var{filename}
19796 Execute the command file @var{filename}.
19799 The lines in a command file are generally executed sequentially,
19800 unless the order of execution is changed by one of the
19801 @emph{flow-control commands} described below. The commands are not
19802 printed as they are executed. An error in any command terminates
19803 execution of the command file and control is returned to the console.
19805 @value{GDBN} first searches for @var{filename} in the current directory.
19806 If the file is not found there, and @var{filename} does not specify a
19807 directory, then @value{GDBN} also looks for the file on the source search path
19808 (specified with the @samp{directory} command);
19809 except that @file{$cdir} is not searched because the compilation directory
19810 is not relevant to scripts.
19812 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19813 on the search path even if @var{filename} specifies a directory.
19814 The search is done by appending @var{filename} to each element of the
19815 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19816 and the search path contains @file{/home/user} then @value{GDBN} will
19817 look for the script @file{/home/user/mylib/myscript}.
19818 The search is also done if @var{filename} is an absolute path.
19819 For example, if @var{filename} is @file{/tmp/myscript} and
19820 the search path contains @file{/home/user} then @value{GDBN} will
19821 look for the script @file{/home/user/tmp/myscript}.
19822 For DOS-like systems, if @var{filename} contains a drive specification,
19823 it is stripped before concatenation. For example, if @var{filename} is
19824 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19825 will look for the script @file{c:/tmp/myscript}.
19827 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19828 each command as it is executed. The option must be given before
19829 @var{filename}, and is interpreted as part of the filename anywhere else.
19831 Commands that would ask for confirmation if used interactively proceed
19832 without asking when used in a command file. Many @value{GDBN} commands that
19833 normally print messages to say what they are doing omit the messages
19834 when called from command files.
19836 @value{GDBN} also accepts command input from standard input. In this
19837 mode, normal output goes to standard output and error output goes to
19838 standard error. Errors in a command file supplied on standard input do
19839 not terminate execution of the command file---execution continues with
19843 gdb < cmds > log 2>&1
19846 (The syntax above will vary depending on the shell used.) This example
19847 will execute commands from the file @file{cmds}. All output and errors
19848 would be directed to @file{log}.
19850 Since commands stored on command files tend to be more general than
19851 commands typed interactively, they frequently need to deal with
19852 complicated situations, such as different or unexpected values of
19853 variables and symbols, changes in how the program being debugged is
19854 built, etc. @value{GDBN} provides a set of flow-control commands to
19855 deal with these complexities. Using these commands, you can write
19856 complex scripts that loop over data structures, execute commands
19857 conditionally, etc.
19864 This command allows to include in your script conditionally executed
19865 commands. The @code{if} command takes a single argument, which is an
19866 expression to evaluate. It is followed by a series of commands that
19867 are executed only if the expression is true (its value is nonzero).
19868 There can then optionally be an @code{else} line, followed by a series
19869 of commands that are only executed if the expression was false. The
19870 end of the list is marked by a line containing @code{end}.
19874 This command allows to write loops. Its syntax is similar to
19875 @code{if}: the command takes a single argument, which is an expression
19876 to evaluate, and must be followed by the commands to execute, one per
19877 line, terminated by an @code{end}. These commands are called the
19878 @dfn{body} of the loop. The commands in the body of @code{while} are
19879 executed repeatedly as long as the expression evaluates to true.
19883 This command exits the @code{while} loop in whose body it is included.
19884 Execution of the script continues after that @code{while}s @code{end}
19887 @kindex loop_continue
19888 @item loop_continue
19889 This command skips the execution of the rest of the body of commands
19890 in the @code{while} loop in whose body it is included. Execution
19891 branches to the beginning of the @code{while} loop, where it evaluates
19892 the controlling expression.
19894 @kindex end@r{ (if/else/while commands)}
19896 Terminate the block of commands that are the body of @code{if},
19897 @code{else}, or @code{while} flow-control commands.
19902 @subsection Commands for Controlled Output
19904 During the execution of a command file or a user-defined command, normal
19905 @value{GDBN} output is suppressed; the only output that appears is what is
19906 explicitly printed by the commands in the definition. This section
19907 describes three commands useful for generating exactly the output you
19912 @item echo @var{text}
19913 @c I do not consider backslash-space a standard C escape sequence
19914 @c because it is not in ANSI.
19915 Print @var{text}. Nonprinting characters can be included in
19916 @var{text} using C escape sequences, such as @samp{\n} to print a
19917 newline. @strong{No newline is printed unless you specify one.}
19918 In addition to the standard C escape sequences, a backslash followed
19919 by a space stands for a space. This is useful for displaying a
19920 string with spaces at the beginning or the end, since leading and
19921 trailing spaces are otherwise trimmed from all arguments.
19922 To print @samp{@w{ }and foo =@w{ }}, use the command
19923 @samp{echo \@w{ }and foo = \@w{ }}.
19925 A backslash at the end of @var{text} can be used, as in C, to continue
19926 the command onto subsequent lines. For example,
19929 echo This is some text\n\
19930 which is continued\n\
19931 onto several lines.\n
19934 produces the same output as
19937 echo This is some text\n
19938 echo which is continued\n
19939 echo onto several lines.\n
19943 @item output @var{expression}
19944 Print the value of @var{expression} and nothing but that value: no
19945 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19946 value history either. @xref{Expressions, ,Expressions}, for more information
19949 @item output/@var{fmt} @var{expression}
19950 Print the value of @var{expression} in format @var{fmt}. You can use
19951 the same formats as for @code{print}. @xref{Output Formats,,Output
19952 Formats}, for more information.
19955 @item printf @var{template}, @var{expressions}@dots{}
19956 Print the values of one or more @var{expressions} under the control of
19957 the string @var{template}. To print several values, make
19958 @var{expressions} be a comma-separated list of individual expressions,
19959 which may be either numbers or pointers. Their values are printed as
19960 specified by @var{template}, exactly as a C program would do by
19961 executing the code below:
19964 printf (@var{template}, @var{expressions}@dots{});
19967 As in @code{C} @code{printf}, ordinary characters in @var{template}
19968 are printed verbatim, while @dfn{conversion specification} introduced
19969 by the @samp{%} character cause subsequent @var{expressions} to be
19970 evaluated, their values converted and formatted according to type and
19971 style information encoded in the conversion specifications, and then
19974 For example, you can print two values in hex like this:
19977 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19980 @code{printf} supports all the standard @code{C} conversion
19981 specifications, including the flags and modifiers between the @samp{%}
19982 character and the conversion letter, with the following exceptions:
19986 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19989 The modifier @samp{*} is not supported for specifying precision or
19993 The @samp{'} flag (for separation of digits into groups according to
19994 @code{LC_NUMERIC'}) is not supported.
19997 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20001 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20004 The conversion letters @samp{a} and @samp{A} are not supported.
20008 Note that the @samp{ll} type modifier is supported only if the
20009 underlying @code{C} implementation used to build @value{GDBN} supports
20010 the @code{long long int} type, and the @samp{L} type modifier is
20011 supported only if @code{long double} type is available.
20013 As in @code{C}, @code{printf} supports simple backslash-escape
20014 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20015 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20016 single character. Octal and hexadecimal escape sequences are not
20019 Additionally, @code{printf} supports conversion specifications for DFP
20020 (@dfn{Decimal Floating Point}) types using the following length modifiers
20021 together with a floating point specifier.
20026 @samp{H} for printing @code{Decimal32} types.
20029 @samp{D} for printing @code{Decimal64} types.
20032 @samp{DD} for printing @code{Decimal128} types.
20035 If the underlying @code{C} implementation used to build @value{GDBN} has
20036 support for the three length modifiers for DFP types, other modifiers
20037 such as width and precision will also be available for @value{GDBN} to use.
20039 In case there is no such @code{C} support, no additional modifiers will be
20040 available and the value will be printed in the standard way.
20042 Here's an example of printing DFP types using the above conversion letters:
20044 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20050 @section Scripting @value{GDBN} using Python
20051 @cindex python scripting
20052 @cindex scripting with python
20054 You can script @value{GDBN} using the @uref{http://www.python.org/,
20055 Python programming language}. This feature is available only if
20056 @value{GDBN} was configured using @option{--with-python}.
20059 * Python Commands:: Accessing Python from @value{GDBN}.
20060 * Python API:: Accessing @value{GDBN} from Python.
20061 * Auto-loading:: Automatically loading Python code.
20064 @node Python Commands
20065 @subsection Python Commands
20066 @cindex python commands
20067 @cindex commands to access python
20069 @value{GDBN} provides one command for accessing the Python interpreter,
20070 and one related setting:
20074 @item python @r{[}@var{code}@r{]}
20075 The @code{python} command can be used to evaluate Python code.
20077 If given an argument, the @code{python} command will evaluate the
20078 argument as a Python command. For example:
20081 (@value{GDBP}) python print 23
20085 If you do not provide an argument to @code{python}, it will act as a
20086 multi-line command, like @code{define}. In this case, the Python
20087 script is made up of subsequent command lines, given after the
20088 @code{python} command. This command list is terminated using a line
20089 containing @code{end}. For example:
20092 (@value{GDBP}) python
20094 End with a line saying just "end".
20100 @kindex maint set python print-stack
20101 @item maint set python print-stack
20102 By default, @value{GDBN} will print a stack trace when an error occurs
20103 in a Python script. This can be controlled using @code{maint set
20104 python print-stack}: if @code{on}, the default, then Python stack
20105 printing is enabled; if @code{off}, then Python stack printing is
20109 It is also possible to execute a Python script from the @value{GDBN}
20113 @item source @file{script-name}
20114 The script name must end with @samp{.py} and @value{GDBN} must be configured
20115 to recognize the script language based on filename extension using
20116 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20118 @item python execfile ("script-name")
20119 This method is based on the @code{execfile} Python built-in function,
20120 and thus is always available.
20124 @subsection Python API
20126 @cindex programming in python
20128 @cindex python stdout
20129 @cindex python pagination
20130 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20131 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20132 A Python program which outputs to one of these streams may have its
20133 output interrupted by the user (@pxref{Screen Size}). In this
20134 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20137 * Basic Python:: Basic Python Functions.
20138 * Exception Handling::
20139 * Values From Inferior::
20140 * Types In Python:: Python representation of types.
20141 * Pretty Printing API:: Pretty-printing values.
20142 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20143 * Disabling Pretty-Printers:: Disabling broken printers.
20144 * Commands In Python:: Implementing new commands in Python.
20145 * Parameters In Python:: Adding new @value{GDBN} parameters.
20146 * Functions In Python:: Writing new convenience functions.
20147 * Progspaces In Python:: Program spaces.
20148 * Objfiles In Python:: Object files.
20149 * Frames In Python:: Accessing inferior stack frames from Python.
20150 * Blocks In Python:: Accessing frame blocks from Python.
20151 * Symbols In Python:: Python representation of symbols.
20152 * Symbol Tables In Python:: Python representation of symbol tables.
20153 * Lazy Strings In Python:: Python representation of lazy strings.
20154 * Breakpoints In Python:: Manipulating breakpoints using Python.
20158 @subsubsection Basic Python
20160 @cindex python functions
20161 @cindex python module
20163 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20164 methods and classes added by @value{GDBN} are placed in this module.
20165 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20166 use in all scripts evaluated by the @code{python} command.
20168 @findex gdb.execute
20169 @defun execute command [from_tty]
20170 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20171 If a GDB exception happens while @var{command} runs, it is
20172 translated as described in @ref{Exception Handling,,Exception Handling}.
20173 If no exceptions occur, this function returns @code{None}.
20175 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20176 command as having originated from the user invoking it interactively.
20177 It must be a boolean value. If omitted, it defaults to @code{False}.
20180 @findex gdb.breakpoints
20182 Return a sequence holding all of @value{GDBN}'s breakpoints.
20183 @xref{Breakpoints In Python}, for more information.
20186 @findex gdb.parameter
20187 @defun parameter parameter
20188 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20189 string naming the parameter to look up; @var{parameter} may contain
20190 spaces if the parameter has a multi-part name. For example,
20191 @samp{print object} is a valid parameter name.
20193 If the named parameter does not exist, this function throws a
20194 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20195 a Python value of the appropriate type, and returned.
20198 @findex gdb.history
20199 @defun history number
20200 Return a value from @value{GDBN}'s value history (@pxref{Value
20201 History}). @var{number} indicates which history element to return.
20202 If @var{number} is negative, then @value{GDBN} will take its absolute value
20203 and count backward from the last element (i.e., the most recent element) to
20204 find the value to return. If @var{number} is zero, then @value{GDBN} will
20205 return the most recent element. If the element specified by @var{number}
20206 doesn't exist in the value history, a @code{RuntimeError} exception will be
20209 If no exception is raised, the return value is always an instance of
20210 @code{gdb.Value} (@pxref{Values From Inferior}).
20213 @findex gdb.parse_and_eval
20214 @defun parse_and_eval expression
20215 Parse @var{expression} as an expression in the current language,
20216 evaluate it, and return the result as a @code{gdb.Value}.
20217 @var{expression} must be a string.
20219 This function can be useful when implementing a new command
20220 (@pxref{Commands In Python}), as it provides a way to parse the
20221 command's argument as an expression. It is also useful simply to
20222 compute values, for example, it is the only way to get the value of a
20223 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20227 @defun write string
20228 Print a string to @value{GDBN}'s paginated standard output stream.
20229 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20230 call this function.
20235 Flush @value{GDBN}'s paginated standard output stream. Flushing
20236 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20240 @findex gdb.target_charset
20241 @defun target_charset
20242 Return the name of the current target character set (@pxref{Character
20243 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20244 that @samp{auto} is never returned.
20247 @findex gdb.target_wide_charset
20248 @defun target_wide_charset
20249 Return the name of the current target wide character set
20250 (@pxref{Character Sets}). This differs from
20251 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20255 @node Exception Handling
20256 @subsubsection Exception Handling
20257 @cindex python exceptions
20258 @cindex exceptions, python
20260 When executing the @code{python} command, Python exceptions
20261 uncaught within the Python code are translated to calls to
20262 @value{GDBN} error-reporting mechanism. If the command that called
20263 @code{python} does not handle the error, @value{GDBN} will
20264 terminate it and print an error message containing the Python
20265 exception name, the associated value, and the Python call stack
20266 backtrace at the point where the exception was raised. Example:
20269 (@value{GDBP}) python print foo
20270 Traceback (most recent call last):
20271 File "<string>", line 1, in <module>
20272 NameError: name 'foo' is not defined
20275 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20276 code are converted to Python @code{RuntimeError} exceptions. User
20277 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20278 prompt) is translated to a Python @code{KeyboardInterrupt}
20279 exception. If you catch these exceptions in your Python code, your
20280 exception handler will see @code{RuntimeError} or
20281 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20282 message as its value, and the Python call stack backtrace at the
20283 Python statement closest to where the @value{GDBN} error occured as the
20286 @findex gdb.GdbError
20287 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20288 it is useful to be able to throw an exception that doesn't cause a
20289 traceback to be printed. For example, the user may have invoked the
20290 command incorrectly. Use the @code{gdb.GdbError} exception
20291 to handle this case. Example:
20295 >class HelloWorld (gdb.Command):
20296 > """Greet the whole world."""
20297 > def __init__ (self):
20298 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20299 > def invoke (self, args, from_tty):
20300 > argv = gdb.string_to_argv (args)
20301 > if len (argv) != 0:
20302 > raise gdb.GdbError ("hello-world takes no arguments")
20303 > print "Hello, World!"
20306 (gdb) hello-world 42
20307 hello-world takes no arguments
20310 @node Values From Inferior
20311 @subsubsection Values From Inferior
20312 @cindex values from inferior, with Python
20313 @cindex python, working with values from inferior
20315 @cindex @code{gdb.Value}
20316 @value{GDBN} provides values it obtains from the inferior program in
20317 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20318 for its internal bookkeeping of the inferior's values, and for
20319 fetching values when necessary.
20321 Inferior values that are simple scalars can be used directly in
20322 Python expressions that are valid for the value's data type. Here's
20323 an example for an integer or floating-point value @code{some_val}:
20330 As result of this, @code{bar} will also be a @code{gdb.Value} object
20331 whose values are of the same type as those of @code{some_val}.
20333 Inferior values that are structures or instances of some class can
20334 be accessed using the Python @dfn{dictionary syntax}. For example, if
20335 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20336 can access its @code{foo} element with:
20339 bar = some_val['foo']
20342 Again, @code{bar} will also be a @code{gdb.Value} object.
20344 The following attributes are provided:
20347 @defivar Value address
20348 If this object is addressable, this read-only attribute holds a
20349 @code{gdb.Value} object representing the address. Otherwise,
20350 this attribute holds @code{None}.
20353 @cindex optimized out value in Python
20354 @defivar Value is_optimized_out
20355 This read-only boolean attribute is true if the compiler optimized out
20356 this value, thus it is not available for fetching from the inferior.
20359 @defivar Value type
20360 The type of this @code{gdb.Value}. The value of this attribute is a
20361 @code{gdb.Type} object.
20365 The following methods are provided:
20368 @defmethod Value cast type
20369 Return a new instance of @code{gdb.Value} that is the result of
20370 casting this instance to the type described by @var{type}, which must
20371 be a @code{gdb.Type} object. If the cast cannot be performed for some
20372 reason, this method throws an exception.
20375 @defmethod Value dereference
20376 For pointer data types, this method returns a new @code{gdb.Value} object
20377 whose contents is the object pointed to by the pointer. For example, if
20378 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20385 then you can use the corresponding @code{gdb.Value} to access what
20386 @code{foo} points to like this:
20389 bar = foo.dereference ()
20392 The result @code{bar} will be a @code{gdb.Value} object holding the
20393 value pointed to by @code{foo}.
20396 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20397 If this @code{gdb.Value} represents a string, then this method
20398 converts the contents to a Python string. Otherwise, this method will
20399 throw an exception.
20401 Strings are recognized in a language-specific way; whether a given
20402 @code{gdb.Value} represents a string is determined by the current
20405 For C-like languages, a value is a string if it is a pointer to or an
20406 array of characters or ints. The string is assumed to be terminated
20407 by a zero of the appropriate width. However if the optional length
20408 argument is given, the string will be converted to that given length,
20409 ignoring any embedded zeros that the string may contain.
20411 If the optional @var{encoding} argument is given, it must be a string
20412 naming the encoding of the string in the @code{gdb.Value}, such as
20413 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20414 the same encodings as the corresponding argument to Python's
20415 @code{string.decode} method, and the Python codec machinery will be used
20416 to convert the string. If @var{encoding} is not given, or if
20417 @var{encoding} is the empty string, then either the @code{target-charset}
20418 (@pxref{Character Sets}) will be used, or a language-specific encoding
20419 will be used, if the current language is able to supply one.
20421 The optional @var{errors} argument is the same as the corresponding
20422 argument to Python's @code{string.decode} method.
20424 If the optional @var{length} argument is given, the string will be
20425 fetched and converted to the given length.
20428 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20429 If this @code{gdb.Value} represents a string, then this method
20430 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20431 In Python}). Otherwise, this method will throw an exception.
20433 If the optional @var{encoding} argument is given, it must be a string
20434 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20435 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20436 @var{encoding} argument is an encoding that @value{GDBN} does
20437 recognize, @value{GDBN} will raise an error.
20439 When a lazy string is printed, the @value{GDBN} encoding machinery is
20440 used to convert the string during printing. If the optional
20441 @var{encoding} argument is not provided, or is an empty string,
20442 @value{GDBN} will automatically select the encoding most suitable for
20443 the string type. For further information on encoding in @value{GDBN}
20444 please see @ref{Character Sets}.
20446 If the optional @var{length} argument is given, the string will be
20447 fetched and encoded to the length of characters specified. If
20448 the @var{length} argument is not provided, the string will be fetched
20449 and encoded until a null of appropriate width is found.
20453 @node Types In Python
20454 @subsubsection Types In Python
20455 @cindex types in Python
20456 @cindex Python, working with types
20459 @value{GDBN} represents types from the inferior using the class
20462 The following type-related functions are available in the @code{gdb}
20465 @findex gdb.lookup_type
20466 @defun lookup_type name [block]
20467 This function looks up a type by name. @var{name} is the name of the
20468 type to look up. It must be a string.
20470 If @var{block} is given, then @var{name} is looked up in that scope.
20471 Otherwise, it is searched for globally.
20473 Ordinarily, this function will return an instance of @code{gdb.Type}.
20474 If the named type cannot be found, it will throw an exception.
20477 An instance of @code{Type} has the following attributes:
20481 The type code for this type. The type code will be one of the
20482 @code{TYPE_CODE_} constants defined below.
20485 @defivar Type sizeof
20486 The size of this type, in target @code{char} units. Usually, a
20487 target's @code{char} type will be an 8-bit byte. However, on some
20488 unusual platforms, this type may have a different size.
20492 The tag name for this type. The tag name is the name after
20493 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20494 languages have this concept. If this type has no tag name, then
20495 @code{None} is returned.
20499 The following methods are provided:
20502 @defmethod Type fields
20503 For structure and union types, this method returns the fields. Range
20504 types have two fields, the minimum and maximum values. Enum types
20505 have one field per enum constant. Function and method types have one
20506 field per parameter. The base types of C@t{++} classes are also
20507 represented as fields. If the type has no fields, or does not fit
20508 into one of these categories, an empty sequence will be returned.
20510 Each field is an object, with some pre-defined attributes:
20513 This attribute is not available for @code{static} fields (as in
20514 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20515 position of the field.
20518 The name of the field, or @code{None} for anonymous fields.
20521 This is @code{True} if the field is artificial, usually meaning that
20522 it was provided by the compiler and not the user. This attribute is
20523 always provided, and is @code{False} if the field is not artificial.
20525 @item is_base_class
20526 This is @code{True} if the field represents a base class of a C@t{++}
20527 structure. This attribute is always provided, and is @code{False}
20528 if the field is not a base class of the type that is the argument of
20529 @code{fields}, or if that type was not a C@t{++} class.
20532 If the field is packed, or is a bitfield, then this will have a
20533 non-zero value, which is the size of the field in bits. Otherwise,
20534 this will be zero; in this case the field's size is given by its type.
20537 The type of the field. This is usually an instance of @code{Type},
20538 but it can be @code{None} in some situations.
20542 @defmethod Type const
20543 Return a new @code{gdb.Type} object which represents a
20544 @code{const}-qualified variant of this type.
20547 @defmethod Type volatile
20548 Return a new @code{gdb.Type} object which represents a
20549 @code{volatile}-qualified variant of this type.
20552 @defmethod Type unqualified
20553 Return a new @code{gdb.Type} object which represents an unqualified
20554 variant of this type. That is, the result is neither @code{const} nor
20558 @defmethod Type range
20559 Return a Python @code{Tuple} object that contains two elements: the
20560 low bound of the argument type and the high bound of that type. If
20561 the type does not have a range, @value{GDBN} will raise a
20562 @code{RuntimeError} exception.
20565 @defmethod Type reference
20566 Return a new @code{gdb.Type} object which represents a reference to this
20570 @defmethod Type pointer
20571 Return a new @code{gdb.Type} object which represents a pointer to this
20575 @defmethod Type strip_typedefs
20576 Return a new @code{gdb.Type} that represents the real type,
20577 after removing all layers of typedefs.
20580 @defmethod Type target
20581 Return a new @code{gdb.Type} object which represents the target type
20584 For a pointer type, the target type is the type of the pointed-to
20585 object. For an array type (meaning C-like arrays), the target type is
20586 the type of the elements of the array. For a function or method type,
20587 the target type is the type of the return value. For a complex type,
20588 the target type is the type of the elements. For a typedef, the
20589 target type is the aliased type.
20591 If the type does not have a target, this method will throw an
20595 @defmethod Type template_argument n [block]
20596 If this @code{gdb.Type} is an instantiation of a template, this will
20597 return a new @code{gdb.Type} which represents the type of the
20598 @var{n}th template argument.
20600 If this @code{gdb.Type} is not a template type, this will throw an
20601 exception. Ordinarily, only C@t{++} code will have template types.
20603 If @var{block} is given, then @var{name} is looked up in that scope.
20604 Otherwise, it is searched for globally.
20609 Each type has a code, which indicates what category this type falls
20610 into. The available type categories are represented by constants
20611 defined in the @code{gdb} module:
20614 @findex TYPE_CODE_PTR
20615 @findex gdb.TYPE_CODE_PTR
20616 @item TYPE_CODE_PTR
20617 The type is a pointer.
20619 @findex TYPE_CODE_ARRAY
20620 @findex gdb.TYPE_CODE_ARRAY
20621 @item TYPE_CODE_ARRAY
20622 The type is an array.
20624 @findex TYPE_CODE_STRUCT
20625 @findex gdb.TYPE_CODE_STRUCT
20626 @item TYPE_CODE_STRUCT
20627 The type is a structure.
20629 @findex TYPE_CODE_UNION
20630 @findex gdb.TYPE_CODE_UNION
20631 @item TYPE_CODE_UNION
20632 The type is a union.
20634 @findex TYPE_CODE_ENUM
20635 @findex gdb.TYPE_CODE_ENUM
20636 @item TYPE_CODE_ENUM
20637 The type is an enum.
20639 @findex TYPE_CODE_FLAGS
20640 @findex gdb.TYPE_CODE_FLAGS
20641 @item TYPE_CODE_FLAGS
20642 A bit flags type, used for things such as status registers.
20644 @findex TYPE_CODE_FUNC
20645 @findex gdb.TYPE_CODE_FUNC
20646 @item TYPE_CODE_FUNC
20647 The type is a function.
20649 @findex TYPE_CODE_INT
20650 @findex gdb.TYPE_CODE_INT
20651 @item TYPE_CODE_INT
20652 The type is an integer type.
20654 @findex TYPE_CODE_FLT
20655 @findex gdb.TYPE_CODE_FLT
20656 @item TYPE_CODE_FLT
20657 A floating point type.
20659 @findex TYPE_CODE_VOID
20660 @findex gdb.TYPE_CODE_VOID
20661 @item TYPE_CODE_VOID
20662 The special type @code{void}.
20664 @findex TYPE_CODE_SET
20665 @findex gdb.TYPE_CODE_SET
20666 @item TYPE_CODE_SET
20669 @findex TYPE_CODE_RANGE
20670 @findex gdb.TYPE_CODE_RANGE
20671 @item TYPE_CODE_RANGE
20672 A range type, that is, an integer type with bounds.
20674 @findex TYPE_CODE_STRING
20675 @findex gdb.TYPE_CODE_STRING
20676 @item TYPE_CODE_STRING
20677 A string type. Note that this is only used for certain languages with
20678 language-defined string types; C strings are not represented this way.
20680 @findex TYPE_CODE_BITSTRING
20681 @findex gdb.TYPE_CODE_BITSTRING
20682 @item TYPE_CODE_BITSTRING
20685 @findex TYPE_CODE_ERROR
20686 @findex gdb.TYPE_CODE_ERROR
20687 @item TYPE_CODE_ERROR
20688 An unknown or erroneous type.
20690 @findex TYPE_CODE_METHOD
20691 @findex gdb.TYPE_CODE_METHOD
20692 @item TYPE_CODE_METHOD
20693 A method type, as found in C@t{++} or Java.
20695 @findex TYPE_CODE_METHODPTR
20696 @findex gdb.TYPE_CODE_METHODPTR
20697 @item TYPE_CODE_METHODPTR
20698 A pointer-to-member-function.
20700 @findex TYPE_CODE_MEMBERPTR
20701 @findex gdb.TYPE_CODE_MEMBERPTR
20702 @item TYPE_CODE_MEMBERPTR
20703 A pointer-to-member.
20705 @findex TYPE_CODE_REF
20706 @findex gdb.TYPE_CODE_REF
20707 @item TYPE_CODE_REF
20710 @findex TYPE_CODE_CHAR
20711 @findex gdb.TYPE_CODE_CHAR
20712 @item TYPE_CODE_CHAR
20715 @findex TYPE_CODE_BOOL
20716 @findex gdb.TYPE_CODE_BOOL
20717 @item TYPE_CODE_BOOL
20720 @findex TYPE_CODE_COMPLEX
20721 @findex gdb.TYPE_CODE_COMPLEX
20722 @item TYPE_CODE_COMPLEX
20723 A complex float type.
20725 @findex TYPE_CODE_TYPEDEF
20726 @findex gdb.TYPE_CODE_TYPEDEF
20727 @item TYPE_CODE_TYPEDEF
20728 A typedef to some other type.
20730 @findex TYPE_CODE_NAMESPACE
20731 @findex gdb.TYPE_CODE_NAMESPACE
20732 @item TYPE_CODE_NAMESPACE
20733 A C@t{++} namespace.
20735 @findex TYPE_CODE_DECFLOAT
20736 @findex gdb.TYPE_CODE_DECFLOAT
20737 @item TYPE_CODE_DECFLOAT
20738 A decimal floating point type.
20740 @findex TYPE_CODE_INTERNAL_FUNCTION
20741 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20742 @item TYPE_CODE_INTERNAL_FUNCTION
20743 A function internal to @value{GDBN}. This is the type used to represent
20744 convenience functions.
20747 @node Pretty Printing API
20748 @subsubsection Pretty Printing API
20750 An example output is provided (@pxref{Pretty Printing}).
20752 A pretty-printer is just an object that holds a value and implements a
20753 specific interface, defined here.
20755 @defop Operation {pretty printer} children (self)
20756 @value{GDBN} will call this method on a pretty-printer to compute the
20757 children of the pretty-printer's value.
20759 This method must return an object conforming to the Python iterator
20760 protocol. Each item returned by the iterator must be a tuple holding
20761 two elements. The first element is the ``name'' of the child; the
20762 second element is the child's value. The value can be any Python
20763 object which is convertible to a @value{GDBN} value.
20765 This method is optional. If it does not exist, @value{GDBN} will act
20766 as though the value has no children.
20769 @defop Operation {pretty printer} display_hint (self)
20770 The CLI may call this method and use its result to change the
20771 formatting of a value. The result will also be supplied to an MI
20772 consumer as a @samp{displayhint} attribute of the variable being
20775 This method is optional. If it does exist, this method must return a
20778 Some display hints are predefined by @value{GDBN}:
20782 Indicate that the object being printed is ``array-like''. The CLI
20783 uses this to respect parameters such as @code{set print elements} and
20784 @code{set print array}.
20787 Indicate that the object being printed is ``map-like'', and that the
20788 children of this value can be assumed to alternate between keys and
20792 Indicate that the object being printed is ``string-like''. If the
20793 printer's @code{to_string} method returns a Python string of some
20794 kind, then @value{GDBN} will call its internal language-specific
20795 string-printing function to format the string. For the CLI this means
20796 adding quotation marks, possibly escaping some characters, respecting
20797 @code{set print elements}, and the like.
20801 @defop Operation {pretty printer} to_string (self)
20802 @value{GDBN} will call this method to display the string
20803 representation of the value passed to the object's constructor.
20805 When printing from the CLI, if the @code{to_string} method exists,
20806 then @value{GDBN} will prepend its result to the values returned by
20807 @code{children}. Exactly how this formatting is done is dependent on
20808 the display hint, and may change as more hints are added. Also,
20809 depending on the print settings (@pxref{Print Settings}), the CLI may
20810 print just the result of @code{to_string} in a stack trace, omitting
20811 the result of @code{children}.
20813 If this method returns a string, it is printed verbatim.
20815 Otherwise, if this method returns an instance of @code{gdb.Value},
20816 then @value{GDBN} prints this value. This may result in a call to
20817 another pretty-printer.
20819 If instead the method returns a Python value which is convertible to a
20820 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20821 the resulting value. Again, this may result in a call to another
20822 pretty-printer. Python scalars (integers, floats, and booleans) and
20823 strings are convertible to @code{gdb.Value}; other types are not.
20825 Finally, if this method returns @code{None} then no further operations
20826 are peformed in this method and nothing is printed.
20828 If the result is not one of these types, an exception is raised.
20831 @node Selecting Pretty-Printers
20832 @subsubsection Selecting Pretty-Printers
20834 The Python list @code{gdb.pretty_printers} contains an array of
20835 functions or callable objects that have been registered via addition
20836 as a pretty-printer.
20837 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20838 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20841 A function on one of these lists is passed a single @code{gdb.Value}
20842 argument and should return a pretty-printer object conforming to the
20843 interface definition above (@pxref{Pretty Printing API}). If a function
20844 cannot create a pretty-printer for the value, it should return
20847 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20848 @code{gdb.Objfile} in the current program space and iteratively calls
20849 each enabled function (@pxref{Disabling Pretty-Printers})
20850 in the list for that @code{gdb.Objfile} until it receives
20851 a pretty-printer object.
20852 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20853 searches the pretty-printer list of the current program space,
20854 calling each enabled function until an object is returned.
20855 After these lists have been exhausted, it tries the global
20856 @code{gdb.pretty_printers} list, again calling each enabled function until an
20857 object is returned.
20859 The order in which the objfiles are searched is not specified. For a
20860 given list, functions are always invoked from the head of the list,
20861 and iterated over sequentially until the end of the list, or a printer
20862 object is returned.
20864 Here is an example showing how a @code{std::string} printer might be
20868 class StdStringPrinter:
20869 "Print a std::string"
20871 def __init__ (self, val):
20874 def to_string (self):
20875 return self.val['_M_dataplus']['_M_p']
20877 def display_hint (self):
20881 And here is an example showing how a lookup function for the printer
20882 example above might be written.
20885 def str_lookup_function (val):
20887 lookup_tag = val.type.tag
20888 regex = re.compile ("^std::basic_string<char,.*>$")
20889 if lookup_tag == None:
20891 if regex.match (lookup_tag):
20892 return StdStringPrinter (val)
20897 The example lookup function extracts the value's type, and attempts to
20898 match it to a type that it can pretty-print. If it is a type the
20899 printer can pretty-print, it will return a printer object. If not, it
20900 returns @code{None}.
20902 We recommend that you put your core pretty-printers into a Python
20903 package. If your pretty-printers are for use with a library, we
20904 further recommend embedding a version number into the package name.
20905 This practice will enable @value{GDBN} to load multiple versions of
20906 your pretty-printers at the same time, because they will have
20909 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20910 can be evaluated multiple times without changing its meaning. An
20911 ideal auto-load file will consist solely of @code{import}s of your
20912 printer modules, followed by a call to a register pretty-printers with
20913 the current objfile.
20915 Taken as a whole, this approach will scale nicely to multiple
20916 inferiors, each potentially using a different library version.
20917 Embedding a version number in the Python package name will ensure that
20918 @value{GDBN} is able to load both sets of printers simultaneously.
20919 Then, because the search for pretty-printers is done by objfile, and
20920 because your auto-loaded code took care to register your library's
20921 printers with a specific objfile, @value{GDBN} will find the correct
20922 printers for the specific version of the library used by each
20925 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
20926 this code might appear in @code{gdb.libstdcxx.v6}:
20929 def register_printers (objfile):
20930 objfile.pretty_printers.add (str_lookup_function)
20934 And then the corresponding contents of the auto-load file would be:
20937 import gdb.libstdcxx.v6
20938 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20941 @node Disabling Pretty-Printers
20942 @subsubsection Disabling Pretty-Printers
20943 @cindex disabling pretty-printers
20945 For various reasons a pretty-printer may not work.
20946 For example, the underlying data structure may have changed and
20947 the pretty-printer is out of date.
20949 The consequences of a broken pretty-printer are severe enough that
20950 @value{GDBN} provides support for enabling and disabling individual
20951 printers. For example, if @code{print frame-arguments} is on,
20952 a backtrace can become highly illegible if any argument is printed
20953 with a broken printer.
20955 Pretty-printers are enabled and disabled by attaching an @code{enabled}
20956 attribute to the registered function or callable object. If this attribute
20957 is present and its value is @code{False}, the printer is disabled, otherwise
20958 the printer is enabled.
20960 @node Commands In Python
20961 @subsubsection Commands In Python
20963 @cindex commands in python
20964 @cindex python commands
20965 You can implement new @value{GDBN} CLI commands in Python. A CLI
20966 command is implemented using an instance of the @code{gdb.Command}
20967 class, most commonly using a subclass.
20969 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20970 The object initializer for @code{Command} registers the new command
20971 with @value{GDBN}. This initializer is normally invoked from the
20972 subclass' own @code{__init__} method.
20974 @var{name} is the name of the command. If @var{name} consists of
20975 multiple words, then the initial words are looked for as prefix
20976 commands. In this case, if one of the prefix commands does not exist,
20977 an exception is raised.
20979 There is no support for multi-line commands.
20981 @var{command_class} should be one of the @samp{COMMAND_} constants
20982 defined below. This argument tells @value{GDBN} how to categorize the
20983 new command in the help system.
20985 @var{completer_class} is an optional argument. If given, it should be
20986 one of the @samp{COMPLETE_} constants defined below. This argument
20987 tells @value{GDBN} how to perform completion for this command. If not
20988 given, @value{GDBN} will attempt to complete using the object's
20989 @code{complete} method (see below); if no such method is found, an
20990 error will occur when completion is attempted.
20992 @var{prefix} is an optional argument. If @code{True}, then the new
20993 command is a prefix command; sub-commands of this command may be
20996 The help text for the new command is taken from the Python
20997 documentation string for the command's class, if there is one. If no
20998 documentation string is provided, the default value ``This command is
20999 not documented.'' is used.
21002 @cindex don't repeat Python command
21003 @defmethod Command dont_repeat
21004 By default, a @value{GDBN} command is repeated when the user enters a
21005 blank line at the command prompt. A command can suppress this
21006 behavior by invoking the @code{dont_repeat} method. This is similar
21007 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21010 @defmethod Command invoke argument from_tty
21011 This method is called by @value{GDBN} when this command is invoked.
21013 @var{argument} is a string. It is the argument to the command, after
21014 leading and trailing whitespace has been stripped.
21016 @var{from_tty} is a boolean argument. When true, this means that the
21017 command was entered by the user at the terminal; when false it means
21018 that the command came from elsewhere.
21020 If this method throws an exception, it is turned into a @value{GDBN}
21021 @code{error} call. Otherwise, the return value is ignored.
21023 @findex gdb.string_to_argv
21024 To break @var{argument} up into an argv-like string use
21025 @code{gdb.string_to_argv}. This function behaves identically to
21026 @value{GDBN}'s internal argument lexer @code{buildargv}.
21027 It is recommended to use this for consistency.
21028 Arguments are separated by spaces and may be quoted.
21032 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21033 ['1', '2 "3', '4 "5', "6 '7"]
21038 @cindex completion of Python commands
21039 @defmethod Command complete text word
21040 This method is called by @value{GDBN} when the user attempts
21041 completion on this command. All forms of completion are handled by
21042 this method, that is, the @key{TAB} and @key{M-?} key bindings
21043 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21046 The arguments @var{text} and @var{word} are both strings. @var{text}
21047 holds the complete command line up to the cursor's location.
21048 @var{word} holds the last word of the command line; this is computed
21049 using a word-breaking heuristic.
21051 The @code{complete} method can return several values:
21054 If the return value is a sequence, the contents of the sequence are
21055 used as the completions. It is up to @code{complete} to ensure that the
21056 contents actually do complete the word. A zero-length sequence is
21057 allowed, it means that there were no completions available. Only
21058 string elements of the sequence are used; other elements in the
21059 sequence are ignored.
21062 If the return value is one of the @samp{COMPLETE_} constants defined
21063 below, then the corresponding @value{GDBN}-internal completion
21064 function is invoked, and its result is used.
21067 All other results are treated as though there were no available
21072 When a new command is registered, it must be declared as a member of
21073 some general class of commands. This is used to classify top-level
21074 commands in the on-line help system; note that prefix commands are not
21075 listed under their own category but rather that of their top-level
21076 command. The available classifications are represented by constants
21077 defined in the @code{gdb} module:
21080 @findex COMMAND_NONE
21081 @findex gdb.COMMAND_NONE
21083 The command does not belong to any particular class. A command in
21084 this category will not be displayed in any of the help categories.
21086 @findex COMMAND_RUNNING
21087 @findex gdb.COMMAND_RUNNING
21088 @item COMMAND_RUNNING
21089 The command is related to running the inferior. For example,
21090 @code{start}, @code{step}, and @code{continue} are in this category.
21091 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21092 commands in this category.
21094 @findex COMMAND_DATA
21095 @findex gdb.COMMAND_DATA
21097 The command is related to data or variables. For example,
21098 @code{call}, @code{find}, and @code{print} are in this category. Type
21099 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21102 @findex COMMAND_STACK
21103 @findex gdb.COMMAND_STACK
21104 @item COMMAND_STACK
21105 The command has to do with manipulation of the stack. For example,
21106 @code{backtrace}, @code{frame}, and @code{return} are in this
21107 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21108 list of commands in this category.
21110 @findex COMMAND_FILES
21111 @findex gdb.COMMAND_FILES
21112 @item COMMAND_FILES
21113 This class is used for file-related commands. For example,
21114 @code{file}, @code{list} and @code{section} are in this category.
21115 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21116 commands in this category.
21118 @findex COMMAND_SUPPORT
21119 @findex gdb.COMMAND_SUPPORT
21120 @item COMMAND_SUPPORT
21121 This should be used for ``support facilities'', generally meaning
21122 things that are useful to the user when interacting with @value{GDBN},
21123 but not related to the state of the inferior. For example,
21124 @code{help}, @code{make}, and @code{shell} are in this category. Type
21125 @kbd{help support} at the @value{GDBN} prompt to see a list of
21126 commands in this category.
21128 @findex COMMAND_STATUS
21129 @findex gdb.COMMAND_STATUS
21130 @item COMMAND_STATUS
21131 The command is an @samp{info}-related command, that is, related to the
21132 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21133 and @code{show} are in this category. Type @kbd{help status} at the
21134 @value{GDBN} prompt to see a list of commands in this category.
21136 @findex COMMAND_BREAKPOINTS
21137 @findex gdb.COMMAND_BREAKPOINTS
21138 @item COMMAND_BREAKPOINTS
21139 The command has to do with breakpoints. For example, @code{break},
21140 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21141 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21144 @findex COMMAND_TRACEPOINTS
21145 @findex gdb.COMMAND_TRACEPOINTS
21146 @item COMMAND_TRACEPOINTS
21147 The command has to do with tracepoints. For example, @code{trace},
21148 @code{actions}, and @code{tfind} are in this category. Type
21149 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21150 commands in this category.
21152 @findex COMMAND_OBSCURE
21153 @findex gdb.COMMAND_OBSCURE
21154 @item COMMAND_OBSCURE
21155 The command is only used in unusual circumstances, or is not of
21156 general interest to users. For example, @code{checkpoint},
21157 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21158 obscure} at the @value{GDBN} prompt to see a list of commands in this
21161 @findex COMMAND_MAINTENANCE
21162 @findex gdb.COMMAND_MAINTENANCE
21163 @item COMMAND_MAINTENANCE
21164 The command is only useful to @value{GDBN} maintainers. The
21165 @code{maintenance} and @code{flushregs} commands are in this category.
21166 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21167 commands in this category.
21170 A new command can use a predefined completion function, either by
21171 specifying it via an argument at initialization, or by returning it
21172 from the @code{complete} method. These predefined completion
21173 constants are all defined in the @code{gdb} module:
21176 @findex COMPLETE_NONE
21177 @findex gdb.COMPLETE_NONE
21178 @item COMPLETE_NONE
21179 This constant means that no completion should be done.
21181 @findex COMPLETE_FILENAME
21182 @findex gdb.COMPLETE_FILENAME
21183 @item COMPLETE_FILENAME
21184 This constant means that filename completion should be performed.
21186 @findex COMPLETE_LOCATION
21187 @findex gdb.COMPLETE_LOCATION
21188 @item COMPLETE_LOCATION
21189 This constant means that location completion should be done.
21190 @xref{Specify Location}.
21192 @findex COMPLETE_COMMAND
21193 @findex gdb.COMPLETE_COMMAND
21194 @item COMPLETE_COMMAND
21195 This constant means that completion should examine @value{GDBN}
21198 @findex COMPLETE_SYMBOL
21199 @findex gdb.COMPLETE_SYMBOL
21200 @item COMPLETE_SYMBOL
21201 This constant means that completion should be done using symbol names
21205 The following code snippet shows how a trivial CLI command can be
21206 implemented in Python:
21209 class HelloWorld (gdb.Command):
21210 """Greet the whole world."""
21212 def __init__ (self):
21213 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21215 def invoke (self, arg, from_tty):
21216 print "Hello, World!"
21221 The last line instantiates the class, and is necessary to trigger the
21222 registration of the command with @value{GDBN}. Depending on how the
21223 Python code is read into @value{GDBN}, you may need to import the
21224 @code{gdb} module explicitly.
21226 @node Parameters In Python
21227 @subsubsection Parameters In Python
21229 @cindex parameters in python
21230 @cindex python parameters
21231 @tindex gdb.Parameter
21233 You can implement new @value{GDBN} parameters using Python. A new
21234 parameter is implemented as an instance of the @code{gdb.Parameter}
21237 Parameters are exposed to the user via the @code{set} and
21238 @code{show} commands. @xref{Help}.
21240 There are many parameters that already exist and can be set in
21241 @value{GDBN}. Two examples are: @code{set follow fork} and
21242 @code{set charset}. Setting these parameters influences certain
21243 behavior in @value{GDBN}. Similarly, you can define parameters that
21244 can be used to influence behavior in custom Python scripts and commands.
21246 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21247 The object initializer for @code{Parameter} registers the new
21248 parameter with @value{GDBN}. This initializer is normally invoked
21249 from the subclass' own @code{__init__} method.
21251 @var{name} is the name of the new parameter. If @var{name} consists
21252 of multiple words, then the initial words are looked for as prefix
21253 parameters. An example of this can be illustrated with the
21254 @code{set print} set of parameters. If @var{name} is
21255 @code{print foo}, then @code{print} will be searched as the prefix
21256 parameter. In this case the parameter can subsequently be accessed in
21257 @value{GDBN} as @code{set print foo}.
21259 If @var{name} consists of multiple words, and no prefix parameter group
21260 can be found, an exception is raised.
21262 @var{command-class} should be one of the @samp{COMMAND_} constants
21263 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21264 categorize the new parameter in the help system.
21266 @var{parameter-class} should be one of the @samp{PARAM_} constants
21267 defined below. This argument tells @value{GDBN} the type of the new
21268 parameter; this information is used for input validation and
21271 If @var{parameter-class} is @code{PARAM_ENUM}, then
21272 @var{enum-sequence} must be a sequence of strings. These strings
21273 represent the possible values for the parameter.
21275 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21276 of a fourth argument will cause an exception to be thrown.
21278 The help text for the new parameter is taken from the Python
21279 documentation string for the parameter's class, if there is one. If
21280 there is no documentation string, a default value is used.
21283 @defivar Parameter set_doc
21284 If this attribute exists, and is a string, then its value is used as
21285 the help text for this parameter's @code{set} command. The value is
21286 examined when @code{Parameter.__init__} is invoked; subsequent changes
21290 @defivar Parameter show_doc
21291 If this attribute exists, and is a string, then its value is used as
21292 the help text for this parameter's @code{show} command. The value is
21293 examined when @code{Parameter.__init__} is invoked; subsequent changes
21297 @defivar Parameter value
21298 The @code{value} attribute holds the underlying value of the
21299 parameter. It can be read and assigned to just as any other
21300 attribute. @value{GDBN} does validation when assignments are made.
21304 When a new parameter is defined, its type must be specified. The
21305 available types are represented by constants defined in the @code{gdb}
21309 @findex PARAM_BOOLEAN
21310 @findex gdb.PARAM_BOOLEAN
21311 @item PARAM_BOOLEAN
21312 The value is a plain boolean. The Python boolean values, @code{True}
21313 and @code{False} are the only valid values.
21315 @findex PARAM_AUTO_BOOLEAN
21316 @findex gdb.PARAM_AUTO_BOOLEAN
21317 @item PARAM_AUTO_BOOLEAN
21318 The value has three possible states: true, false, and @samp{auto}. In
21319 Python, true and false are represented using boolean constants, and
21320 @samp{auto} is represented using @code{None}.
21322 @findex PARAM_UINTEGER
21323 @findex gdb.PARAM_UINTEGER
21324 @item PARAM_UINTEGER
21325 The value is an unsigned integer. The value of 0 should be
21326 interpreted to mean ``unlimited''.
21328 @findex PARAM_INTEGER
21329 @findex gdb.PARAM_INTEGER
21330 @item PARAM_INTEGER
21331 The value is a signed integer. The value of 0 should be interpreted
21332 to mean ``unlimited''.
21334 @findex PARAM_STRING
21335 @findex gdb.PARAM_STRING
21337 The value is a string. When the user modifies the string, any escape
21338 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21339 translated into corresponding characters and encoded into the current
21342 @findex PARAM_STRING_NOESCAPE
21343 @findex gdb.PARAM_STRING_NOESCAPE
21344 @item PARAM_STRING_NOESCAPE
21345 The value is a string. When the user modifies the string, escapes are
21346 passed through untranslated.
21348 @findex PARAM_OPTIONAL_FILENAME
21349 @findex gdb.PARAM_OPTIONAL_FILENAME
21350 @item PARAM_OPTIONAL_FILENAME
21351 The value is a either a filename (a string), or @code{None}.
21353 @findex PARAM_FILENAME
21354 @findex gdb.PARAM_FILENAME
21355 @item PARAM_FILENAME
21356 The value is a filename. This is just like
21357 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21359 @findex PARAM_ZINTEGER
21360 @findex gdb.PARAM_ZINTEGER
21361 @item PARAM_ZINTEGER
21362 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21363 is interpreted as itself.
21366 @findex gdb.PARAM_ENUM
21368 The value is a string, which must be one of a collection string
21369 constants provided when the parameter is created.
21372 @node Functions In Python
21373 @subsubsection Writing new convenience functions
21375 @cindex writing convenience functions
21376 @cindex convenience functions in python
21377 @cindex python convenience functions
21378 @tindex gdb.Function
21380 You can implement new convenience functions (@pxref{Convenience Vars})
21381 in Python. A convenience function is an instance of a subclass of the
21382 class @code{gdb.Function}.
21384 @defmethod Function __init__ name
21385 The initializer for @code{Function} registers the new function with
21386 @value{GDBN}. The argument @var{name} is the name of the function,
21387 a string. The function will be visible to the user as a convenience
21388 variable of type @code{internal function}, whose name is the same as
21389 the given @var{name}.
21391 The documentation for the new function is taken from the documentation
21392 string for the new class.
21395 @defmethod Function invoke @var{*args}
21396 When a convenience function is evaluated, its arguments are converted
21397 to instances of @code{gdb.Value}, and then the function's
21398 @code{invoke} method is called. Note that @value{GDBN} does not
21399 predetermine the arity of convenience functions. Instead, all
21400 available arguments are passed to @code{invoke}, following the
21401 standard Python calling convention. In particular, a convenience
21402 function can have default values for parameters without ill effect.
21404 The return value of this method is used as its value in the enclosing
21405 expression. If an ordinary Python value is returned, it is converted
21406 to a @code{gdb.Value} following the usual rules.
21409 The following code snippet shows how a trivial convenience function can
21410 be implemented in Python:
21413 class Greet (gdb.Function):
21414 """Return string to greet someone.
21415 Takes a name as argument."""
21417 def __init__ (self):
21418 super (Greet, self).__init__ ("greet")
21420 def invoke (self, name):
21421 return "Hello, %s!" % name.string ()
21426 The last line instantiates the class, and is necessary to trigger the
21427 registration of the function with @value{GDBN}. Depending on how the
21428 Python code is read into @value{GDBN}, you may need to import the
21429 @code{gdb} module explicitly.
21431 @node Progspaces In Python
21432 @subsubsection Program Spaces In Python
21434 @cindex progspaces in python
21435 @tindex gdb.Progspace
21437 A program space, or @dfn{progspace}, represents a symbolic view
21438 of an address space.
21439 It consists of all of the objfiles of the program.
21440 @xref{Objfiles In Python}.
21441 @xref{Inferiors and Programs, program spaces}, for more details
21442 about program spaces.
21444 The following progspace-related functions are available in the
21447 @findex gdb.current_progspace
21448 @defun current_progspace
21449 This function returns the program space of the currently selected inferior.
21450 @xref{Inferiors and Programs}.
21453 @findex gdb.progspaces
21455 Return a sequence of all the progspaces currently known to @value{GDBN}.
21458 Each progspace is represented by an instance of the @code{gdb.Progspace}
21461 @defivar Progspace filename
21462 The file name of the progspace as a string.
21465 @defivar Progspace pretty_printers
21466 The @code{pretty_printers} attribute is a list of functions. It is
21467 used to look up pretty-printers. A @code{Value} is passed to each
21468 function in order; if the function returns @code{None}, then the
21469 search continues. Otherwise, the return value should be an object
21470 which is used to format the value. @xref{Pretty Printing API}, for more
21474 @node Objfiles In Python
21475 @subsubsection Objfiles In Python
21477 @cindex objfiles in python
21478 @tindex gdb.Objfile
21480 @value{GDBN} loads symbols for an inferior from various
21481 symbol-containing files (@pxref{Files}). These include the primary
21482 executable file, any shared libraries used by the inferior, and any
21483 separate debug info files (@pxref{Separate Debug Files}).
21484 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21486 The following objfile-related functions are available in the
21489 @findex gdb.current_objfile
21490 @defun current_objfile
21491 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21492 sets the ``current objfile'' to the corresponding objfile. This
21493 function returns the current objfile. If there is no current objfile,
21494 this function returns @code{None}.
21497 @findex gdb.objfiles
21499 Return a sequence of all the objfiles current known to @value{GDBN}.
21500 @xref{Objfiles In Python}.
21503 Each objfile is represented by an instance of the @code{gdb.Objfile}
21506 @defivar Objfile filename
21507 The file name of the objfile as a string.
21510 @defivar Objfile pretty_printers
21511 The @code{pretty_printers} attribute is a list of functions. It is
21512 used to look up pretty-printers. A @code{Value} is passed to each
21513 function in order; if the function returns @code{None}, then the
21514 search continues. Otherwise, the return value should be an object
21515 which is used to format the value. @xref{Pretty Printing API}, for more
21519 @node Frames In Python
21520 @subsubsection Accessing inferior stack frames from Python.
21522 @cindex frames in python
21523 When the debugged program stops, @value{GDBN} is able to analyze its call
21524 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21525 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21526 while its corresponding frame exists in the inferior's stack. If you try
21527 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21530 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21534 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21538 The following frame-related functions are available in the @code{gdb} module:
21540 @findex gdb.selected_frame
21541 @defun selected_frame
21542 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21545 @defun frame_stop_reason_string reason
21546 Return a string explaining the reason why @value{GDBN} stopped unwinding
21547 frames, as expressed by the given @var{reason} code (an integer, see the
21548 @code{unwind_stop_reason} method further down in this section).
21551 A @code{gdb.Frame} object has the following methods:
21554 @defmethod Frame is_valid
21555 Returns true if the @code{gdb.Frame} object is valid, false if not.
21556 A frame object can become invalid if the frame it refers to doesn't
21557 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21558 an exception if it is invalid at the time the method is called.
21561 @defmethod Frame name
21562 Returns the function name of the frame, or @code{None} if it can't be
21566 @defmethod Frame type
21567 Returns the type of the frame. The value can be one of
21568 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21569 or @code{gdb.SENTINEL_FRAME}.
21572 @defmethod Frame unwind_stop_reason
21573 Return an integer representing the reason why it's not possible to find
21574 more frames toward the outermost frame. Use
21575 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21576 function to a string.
21579 @defmethod Frame pc
21580 Returns the frame's resume address.
21583 @defmethod Frame block
21584 Return the frame's code block. @xref{Blocks In Python}.
21587 @defmethod Frame function
21588 Return the symbol for the function corresponding to this frame.
21589 @xref{Symbols In Python}.
21592 @defmethod Frame older
21593 Return the frame that called this frame.
21596 @defmethod Frame newer
21597 Return the frame called by this frame.
21600 @defmethod Frame find_sal
21601 Return the frame's symtab and line object.
21602 @xref{Symbol Tables In Python}.
21605 @defmethod Frame read_var variable @r{[}block@r{]}
21606 Return the value of @var{variable} in this frame. If the optional
21607 argument @var{block} is provided, search for the variable from that
21608 block; otherwise start at the frame's current block (which is
21609 determined by the frame's current program counter). @var{variable}
21610 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21611 @code{gdb.Block} object.
21614 @defmethod Frame select
21615 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21620 @node Blocks In Python
21621 @subsubsection Accessing frame blocks from Python.
21623 @cindex blocks in python
21626 Within each frame, @value{GDBN} maintains information on each block
21627 stored in that frame. These blocks are organized hierarchically, and
21628 are represented individually in Python as a @code{gdb.Block}.
21629 Please see @ref{Frames In Python}, for a more in-depth discussion on
21630 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21631 detailed technical information on @value{GDBN}'s book-keeping of the
21634 The following block-related functions are available in the @code{gdb}
21637 @findex gdb.block_for_pc
21638 @defun block_for_pc pc
21639 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21640 block cannot be found for the @var{pc} value specified, the function
21641 will return @code{None}.
21644 A @code{gdb.Block} object has the following attributes:
21647 @defivar Block start
21648 The start address of the block. This attribute is not writable.
21652 The end address of the block. This attribute is not writable.
21655 @defivar Block function
21656 The name of the block represented as a @code{gdb.Symbol}. If the
21657 block is not named, then this attribute holds @code{None}. This
21658 attribute is not writable.
21661 @defivar Block superblock
21662 The block containing this block. If this parent block does not exist,
21663 this attribute holds @code{None}. This attribute is not writable.
21667 @node Symbols In Python
21668 @subsubsection Python representation of Symbols.
21670 @cindex symbols in python
21673 @value{GDBN} represents every variable, function and type as an
21674 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21675 Similarly, Python represents these symbols in @value{GDBN} with the
21676 @code{gdb.Symbol} object.
21678 The following symbol-related functions are available in the @code{gdb}
21681 @findex gdb.lookup_symbol
21682 @defun lookup_symbol name [block] [domain]
21683 This function searches for a symbol by name. The search scope can be
21684 restricted to the parameters defined in the optional domain and block
21687 @var{name} is the name of the symbol. It must be a string. The
21688 optional @var{block} argument restricts the search to symbols visible
21689 in that @var{block}. The @var{block} argument must be a
21690 @code{gdb.Block} object. The optional @var{domain} argument restricts
21691 the search to the domain type. The @var{domain} argument must be a
21692 domain constant defined in the @code{gdb} module and described later
21696 A @code{gdb.Symbol} object has the following attributes:
21699 @defivar Symbol symtab
21700 The symbol table in which the symbol appears. This attribute is
21701 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21702 Python}. This attribute is not writable.
21705 @defivar Symbol name
21706 The name of the symbol as a string. This attribute is not writable.
21709 @defivar Symbol linkage_name
21710 The name of the symbol, as used by the linker (i.e., may be mangled).
21711 This attribute is not writable.
21714 @defivar Symbol print_name
21715 The name of the symbol in a form suitable for output. This is either
21716 @code{name} or @code{linkage_name}, depending on whether the user
21717 asked @value{GDBN} to display demangled or mangled names.
21720 @defivar Symbol addr_class
21721 The address class of the symbol. This classifies how to find the value
21722 of a symbol. Each address class is a constant defined in the
21723 @code{gdb} module and described later in this chapter.
21726 @defivar Symbol is_argument
21727 @code{True} if the symbol is an argument of a function.
21730 @defivar Symbol is_constant
21731 @code{True} if the symbol is a constant.
21734 @defivar Symbol is_function
21735 @code{True} if the symbol is a function or a method.
21738 @defivar Symbol is_variable
21739 @code{True} if the symbol is a variable.
21743 The available domain categories in @code{gdb.Symbol} are represented
21744 as constants in the @code{gdb} module:
21747 @findex SYMBOL_UNDEF_DOMAIN
21748 @findex gdb.SYMBOL_UNDEF_DOMAIN
21749 @item SYMBOL_UNDEF_DOMAIN
21750 This is used when a domain has not been discovered or none of the
21751 following domains apply. This usually indicates an error either
21752 in the symbol information or in @value{GDBN}'s handling of symbols.
21753 @findex SYMBOL_VAR_DOMAIN
21754 @findex gdb.SYMBOL_VAR_DOMAIN
21755 @item SYMBOL_VAR_DOMAIN
21756 This domain contains variables, function names, typedef names and enum
21758 @findex SYMBOL_STRUCT_DOMAIN
21759 @findex gdb.SYMBOL_STRUCT_DOMAIN
21760 @item SYMBOL_STRUCT_DOMAIN
21761 This domain holds struct, union and enum type names.
21762 @findex SYMBOL_LABEL_DOMAIN
21763 @findex gdb.SYMBOL_LABEL_DOMAIN
21764 @item SYMBOL_LABEL_DOMAIN
21765 This domain contains names of labels (for gotos).
21766 @findex SYMBOL_VARIABLES_DOMAIN
21767 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21768 @item SYMBOL_VARIABLES_DOMAIN
21769 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21770 contains everything minus functions and types.
21771 @findex SYMBOL_FUNCTIONS_DOMAIN
21772 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21773 @item SYMBOL_FUNCTION_DOMAIN
21774 This domain contains all functions.
21775 @findex SYMBOL_TYPES_DOMAIN
21776 @findex gdb.SYMBOL_TYPES_DOMAIN
21777 @item SYMBOL_TYPES_DOMAIN
21778 This domain contains all types.
21781 The available address class categories in @code{gdb.Symbol} are represented
21782 as constants in the @code{gdb} module:
21785 @findex SYMBOL_LOC_UNDEF
21786 @findex gdb.SYMBOL_LOC_UNDEF
21787 @item SYMBOL_LOC_UNDEF
21788 If this is returned by address class, it indicates an error either in
21789 the symbol information or in @value{GDBN}'s handling of symbols.
21790 @findex SYMBOL_LOC_CONST
21791 @findex gdb.SYMBOL_LOC_CONST
21792 @item SYMBOL_LOC_CONST
21793 Value is constant int.
21794 @findex SYMBOL_LOC_STATIC
21795 @findex gdb.SYMBOL_LOC_STATIC
21796 @item SYMBOL_LOC_STATIC
21797 Value is at a fixed address.
21798 @findex SYMBOL_LOC_REGISTER
21799 @findex gdb.SYMBOL_LOC_REGISTER
21800 @item SYMBOL_LOC_REGISTER
21801 Value is in a register.
21802 @findex SYMBOL_LOC_ARG
21803 @findex gdb.SYMBOL_LOC_ARG
21804 @item SYMBOL_LOC_ARG
21805 Value is an argument. This value is at the offset stored within the
21806 symbol inside the frame's argument list.
21807 @findex SYMBOL_LOC_REF_ARG
21808 @findex gdb.SYMBOL_LOC_REF_ARG
21809 @item SYMBOL_LOC_REF_ARG
21810 Value address is stored in the frame's argument list. Just like
21811 @code{LOC_ARG} except that the value's address is stored at the
21812 offset, not the value itself.
21813 @findex SYMBOL_LOC_REGPARM_ADDR
21814 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21815 @item SYMBOL_LOC_REGPARM_ADDR
21816 Value is a specified register. Just like @code{LOC_REGISTER} except
21817 the register holds the address of the argument instead of the argument
21819 @findex SYMBOL_LOC_LOCAL
21820 @findex gdb.SYMBOL_LOC_LOCAL
21821 @item SYMBOL_LOC_LOCAL
21822 Value is a local variable.
21823 @findex SYMBOL_LOC_TYPEDEF
21824 @findex gdb.SYMBOL_LOC_TYPEDEF
21825 @item SYMBOL_LOC_TYPEDEF
21826 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21828 @findex SYMBOL_LOC_BLOCK
21829 @findex gdb.SYMBOL_LOC_BLOCK
21830 @item SYMBOL_LOC_BLOCK
21832 @findex SYMBOL_LOC_CONST_BYTES
21833 @findex gdb.SYMBOL_LOC_CONST_BYTES
21834 @item SYMBOL_LOC_CONST_BYTES
21835 Value is a byte-sequence.
21836 @findex SYMBOL_LOC_UNRESOLVED
21837 @findex gdb.SYMBOL_LOC_UNRESOLVED
21838 @item SYMBOL_LOC_UNRESOLVED
21839 Value is at a fixed address, but the address of the variable has to be
21840 determined from the minimal symbol table whenever the variable is
21842 @findex SYMBOL_LOC_OPTIMIZED_OUT
21843 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21844 @item SYMBOL_LOC_OPTIMIZED_OUT
21845 The value does not actually exist in the program.
21846 @findex SYMBOL_LOC_COMPUTED
21847 @findex gdb.SYMBOL_LOC_COMPUTED
21848 @item SYMBOL_LOC_COMPUTED
21849 The value's address is a computed location.
21852 @node Symbol Tables In Python
21853 @subsubsection Symbol table representation in Python.
21855 @cindex symbol tables in python
21857 @tindex gdb.Symtab_and_line
21859 Access to symbol table data maintained by @value{GDBN} on the inferior
21860 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21861 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21862 from the @code{find_sal} method in @code{gdb.Frame} object.
21863 @xref{Frames In Python}.
21865 For more information on @value{GDBN}'s symbol table management, see
21866 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21868 A @code{gdb.Symtab_and_line} object has the following attributes:
21871 @defivar Symtab_and_line symtab
21872 The symbol table object (@code{gdb.Symtab}) for this frame.
21873 This attribute is not writable.
21876 @defivar Symtab_and_line pc
21877 Indicates the current program counter address. This attribute is not
21881 @defivar Symtab_and_line line
21882 Indicates the current line number for this object. This
21883 attribute is not writable.
21887 A @code{gdb.Symtab} object has the following attributes:
21890 @defivar Symtab filename
21891 The symbol table's source filename. This attribute is not writable.
21894 @defivar Symtab objfile
21895 The symbol table's backing object file. @xref{Objfiles In Python}.
21896 This attribute is not writable.
21900 The following methods are provided:
21903 @defmethod Symtab fullname
21904 Return the symbol table's source absolute file name.
21908 @node Breakpoints In Python
21909 @subsubsection Manipulating breakpoints using Python
21911 @cindex breakpoints in python
21912 @tindex gdb.Breakpoint
21914 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
21917 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
21918 Create a new breakpoint. @var{spec} is a string naming the
21919 location of the breakpoint, or an expression that defines a
21920 watchpoint. The contents can be any location recognized by the
21921 @code{break} command, or in the case of a watchpoint, by the @code{watch}
21922 command. The optional @var{type} denotes the breakpoint to create
21923 from the types defined later in this chapter. This argument can be
21924 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
21925 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
21926 argument defines the class of watchpoint to create, if @var{type} is
21927 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
21928 provided, it is assumed to be a @var{WP_WRITE} class.
21931 The available watchpoint types represented by constants are defined in the
21936 @findex gdb.WP_READ
21938 Read only watchpoint.
21941 @findex gdb.WP_WRITE
21943 Write only watchpoint.
21946 @findex gdb.WP_ACCESS
21948 Read/Write watchpoint.
21951 @defmethod Breakpoint is_valid
21952 Return @code{True} if this @code{Breakpoint} object is valid,
21953 @code{False} otherwise. A @code{Breakpoint} object can become invalid
21954 if the user deletes the breakpoint. In this case, the object still
21955 exists, but the underlying breakpoint does not. In the cases of
21956 watchpoint scope, the watchpoint remains valid even if execution of the
21957 inferior leaves the scope of that watchpoint.
21960 @defivar Breakpoint enabled
21961 This attribute is @code{True} if the breakpoint is enabled, and
21962 @code{False} otherwise. This attribute is writable.
21965 @defivar Breakpoint silent
21966 This attribute is @code{True} if the breakpoint is silent, and
21967 @code{False} otherwise. This attribute is writable.
21969 Note that a breakpoint can also be silent if it has commands and the
21970 first command is @code{silent}. This is not reported by the
21971 @code{silent} attribute.
21974 @defivar Breakpoint thread
21975 If the breakpoint is thread-specific, this attribute holds the thread
21976 id. If the breakpoint is not thread-specific, this attribute is
21977 @code{None}. This attribute is writable.
21980 @defivar Breakpoint task
21981 If the breakpoint is Ada task-specific, this attribute holds the Ada task
21982 id. If the breakpoint is not task-specific (or the underlying
21983 language is not Ada), this attribute is @code{None}. This attribute
21987 @defivar Breakpoint ignore_count
21988 This attribute holds the ignore count for the breakpoint, an integer.
21989 This attribute is writable.
21992 @defivar Breakpoint number
21993 This attribute holds the breakpoint's number --- the identifier used by
21994 the user to manipulate the breakpoint. This attribute is not writable.
21997 @defivar Breakpoint type
21998 This attribute holds the breakpoint's type --- the identifier used to
21999 determine the actual breakpoint type or use-case. This attribute is not
22003 The available types are represented by constants defined in the @code{gdb}
22007 @findex BP_BREAKPOINT
22008 @findex gdb.BP_BREAKPOINT
22009 @item BP_BREAKPOINT
22010 Normal code breakpoint.
22012 @findex BP_WATCHPOINT
22013 @findex gdb.BP_WATCHPOINT
22014 @item BP_WATCHPOINT
22015 Watchpoint breakpoint.
22017 @findex BP_HARDWARE_WATCHPOINT
22018 @findex gdb.BP_HARDWARE_WATCHPOINT
22019 @item BP_HARDWARE_WATCHPOINT
22020 Hardware assisted watchpoint.
22022 @findex BP_READ_WATCHPOINT
22023 @findex gdb.BP_READ_WATCHPOINT
22024 @item BP_READ_WATCHPOINT
22025 Hardware assisted read watchpoint.
22027 @findex BP_ACCESS_WATCHPOINT
22028 @findex gdb.BP_ACCESS_WATCHPOINT
22029 @item BP_ACCESS_WATCHPOINT
22030 Hardware assisted access watchpoint.
22033 @defivar Breakpoint hit_count
22034 This attribute holds the hit count for the breakpoint, an integer.
22035 This attribute is writable, but currently it can only be set to zero.
22038 @defivar Breakpoint location
22039 This attribute holds the location of the breakpoint, as specified by
22040 the user. It is a string. If the breakpoint does not have a location
22041 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22042 attribute is not writable.
22045 @defivar Breakpoint expression
22046 This attribute holds a breakpoint expression, as specified by
22047 the user. It is a string. If the breakpoint does not have an
22048 expression (the breakpoint is not a watchpoint) the attribute's value
22049 is @code{None}. This attribute is not writable.
22052 @defivar Breakpoint condition
22053 This attribute holds the condition of the breakpoint, as specified by
22054 the user. It is a string. If there is no condition, this attribute's
22055 value is @code{None}. This attribute is writable.
22058 @defivar Breakpoint commands
22059 This attribute holds the commands attached to the breakpoint. If
22060 there are commands, this attribute's value is a string holding all the
22061 commands, separated by newlines. If there are no commands, this
22062 attribute is @code{None}. This attribute is not writable.
22065 @node Lazy Strings In Python
22066 @subsubsection Python representation of lazy strings.
22068 @cindex lazy strings in python
22069 @tindex gdb.LazyString
22071 A @dfn{lazy string} is a string whose contents is not retrieved or
22072 encoded until it is needed.
22074 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22075 @code{address} that points to a region of memory, an @code{encoding}
22076 that will be used to encode that region of memory, and a @code{length}
22077 to delimit the region of memory that represents the string. The
22078 difference between a @code{gdb.LazyString} and a string wrapped within
22079 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22080 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22081 retrieved and encoded during printing, while a @code{gdb.Value}
22082 wrapping a string is immediately retrieved and encoded on creation.
22084 A @code{gdb.LazyString} object has the following functions:
22086 @defmethod LazyString value
22087 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22088 will point to the string in memory, but will lose all the delayed
22089 retrieval, encoding and handling that @value{GDBN} applies to a
22090 @code{gdb.LazyString}.
22093 @defivar LazyString address
22094 This attribute holds the address of the string. This attribute is not
22098 @defivar LazyString length
22099 This attribute holds the length of the string in characters. If the
22100 length is -1, then the string will be fetched and encoded up to the
22101 first null of appropriate width. This attribute is not writable.
22104 @defivar LazyString encoding
22105 This attribute holds the encoding that will be applied to the string
22106 when the string is printed by @value{GDBN}. If the encoding is not
22107 set, or contains an empty string, then @value{GDBN} will select the
22108 most appropriate encoding when the string is printed. This attribute
22112 @defivar LazyString type
22113 This attribute holds the type that is represented by the lazy string's
22114 type. For a lazy string this will always be a pointer type. To
22115 resolve this to the lazy string's character type, use the type's
22116 @code{target} method. @xref{Types In Python}. This attribute is not
22121 @subsection Auto-loading
22122 @cindex auto-loading, Python
22124 When a new object file is read (for example, due to the @code{file}
22125 command, or because the inferior has loaded a shared library),
22126 @value{GDBN} will look for Python support scripts in several ways:
22127 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22130 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22131 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22132 * Which flavor to choose?::
22135 The auto-loading feature is useful for supplying application-specific
22136 debugging commands and scripts.
22138 Auto-loading can be enabled or disabled.
22141 @kindex maint set python auto-load
22142 @item maint set python auto-load [yes|no]
22143 Enable or disable the Python auto-loading feature.
22145 @kindex maint show python auto-load
22146 @item maint show python auto-load
22147 Show whether Python auto-loading is enabled or disabled.
22150 When reading an auto-loaded file, @value{GDBN} sets the
22151 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22152 function (@pxref{Objfiles In Python}). This can be useful for
22153 registering objfile-specific pretty-printers.
22155 @node objfile-gdb.py file
22156 @subsubsection The @file{@var{objfile}-gdb.py} file
22157 @cindex @file{@var{objfile}-gdb.py}
22159 When a new object file is read, @value{GDBN} looks for
22160 a file named @file{@var{objfile}-gdb.py},
22161 where @var{objfile} is the object file's real name, formed by ensuring
22162 that the file name is absolute, following all symlinks, and resolving
22163 @code{.} and @code{..} components. If this file exists and is
22164 readable, @value{GDBN} will evaluate it as a Python script.
22166 If this file does not exist, and if the parameter
22167 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22168 then @value{GDBN} will look for @var{real-name} in all of the
22169 directories mentioned in the value of @code{debug-file-directory}.
22171 Finally, if this file does not exist, then @value{GDBN} will look for
22172 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22173 @var{data-directory} is @value{GDBN}'s data directory (available via
22174 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22175 is the object file's real name, as described above.
22177 @value{GDBN} does not track which files it has already auto-loaded this way.
22178 @value{GDBN} will load the associated script every time the corresponding
22179 @var{objfile} is opened.
22180 So your @file{-gdb.py} file should be careful to avoid errors if it
22181 is evaluated more than once.
22183 @node .debug_gdb_scripts section
22184 @subsubsection The @code{.debug_gdb_scripts} section
22185 @cindex @code{.debug_gdb_scripts} section
22187 For systems using file formats like ELF and COFF,
22188 when @value{GDBN} loads a new object file
22189 it will look for a special section named @samp{.debug_gdb_scripts}.
22190 If this section exists, its contents is a list of names of scripts to load.
22192 @value{GDBN} will look for each specified script file first in the
22193 current directory and then along the source search path
22194 (@pxref{Source Path, ,Specifying Source Directories}),
22195 except that @file{$cdir} is not searched, since the compilation
22196 directory is not relevant to scripts.
22198 Entries can be placed in section @code{.debug_gdb_scripts} with,
22199 for example, this GCC macro:
22202 /* Note: The "MS" section flags are to remote duplicates. */
22203 #define DEFINE_GDB_SCRIPT(script_name) \
22205 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22207 .asciz \"" script_name "\"\n\
22213 Then one can reference the macro in a header or source file like this:
22216 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22219 The script name may include directories if desired.
22221 If the macro is put in a header, any application or library
22222 using this header will get a reference to the specified script.
22224 @node Which flavor to choose?
22225 @subsubsection Which flavor to choose?
22227 Given the multiple ways of auto-loading Python scripts, it might not always
22228 be clear which one to choose. This section provides some guidance.
22230 Benefits of the @file{-gdb.py} way:
22234 Can be used with file formats that don't support multiple sections.
22237 Ease of finding scripts for public libraries.
22239 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22240 in the source search path.
22241 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22242 isn't a source directory in which to find the script.
22245 Doesn't require source code additions.
22248 Benefits of the @code{.debug_gdb_scripts} way:
22252 Works with static linking.
22254 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22255 trigger their loading. When an application is statically linked the only
22256 objfile available is the executable, and it is cumbersome to attach all the
22257 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22260 Works with classes that are entirely inlined.
22262 Some classes can be entirely inlined, and thus there may not be an associated
22263 shared library to attach a @file{-gdb.py} script to.
22266 Scripts needn't be copied out of the source tree.
22268 In some circumstances, apps can be built out of large collections of internal
22269 libraries, and the build infrastructure necessary to install the
22270 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22271 cumbersome. It may be easier to specify the scripts in the
22272 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22273 top of the source tree to the source search path.
22277 @chapter Command Interpreters
22278 @cindex command interpreters
22280 @value{GDBN} supports multiple command interpreters, and some command
22281 infrastructure to allow users or user interface writers to switch
22282 between interpreters or run commands in other interpreters.
22284 @value{GDBN} currently supports two command interpreters, the console
22285 interpreter (sometimes called the command-line interpreter or @sc{cli})
22286 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22287 describes both of these interfaces in great detail.
22289 By default, @value{GDBN} will start with the console interpreter.
22290 However, the user may choose to start @value{GDBN} with another
22291 interpreter by specifying the @option{-i} or @option{--interpreter}
22292 startup options. Defined interpreters include:
22296 @cindex console interpreter
22297 The traditional console or command-line interpreter. This is the most often
22298 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22299 @value{GDBN} will use this interpreter.
22302 @cindex mi interpreter
22303 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22304 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22305 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22309 @cindex mi2 interpreter
22310 The current @sc{gdb/mi} interface.
22313 @cindex mi1 interpreter
22314 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22318 @cindex invoke another interpreter
22319 The interpreter being used by @value{GDBN} may not be dynamically
22320 switched at runtime. Although possible, this could lead to a very
22321 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22322 enters the command "interpreter-set console" in a console view,
22323 @value{GDBN} would switch to using the console interpreter, rendering
22324 the IDE inoperable!
22326 @kindex interpreter-exec
22327 Although you may only choose a single interpreter at startup, you may execute
22328 commands in any interpreter from the current interpreter using the appropriate
22329 command. If you are running the console interpreter, simply use the
22330 @code{interpreter-exec} command:
22333 interpreter-exec mi "-data-list-register-names"
22336 @sc{gdb/mi} has a similar command, although it is only available in versions of
22337 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22340 @chapter @value{GDBN} Text User Interface
22342 @cindex Text User Interface
22345 * TUI Overview:: TUI overview
22346 * TUI Keys:: TUI key bindings
22347 * TUI Single Key Mode:: TUI single key mode
22348 * TUI Commands:: TUI-specific commands
22349 * TUI Configuration:: TUI configuration variables
22352 The @value{GDBN} Text User Interface (TUI) is a terminal
22353 interface which uses the @code{curses} library to show the source
22354 file, the assembly output, the program registers and @value{GDBN}
22355 commands in separate text windows. The TUI mode is supported only
22356 on platforms where a suitable version of the @code{curses} library
22359 @pindex @value{GDBTUI}
22360 The TUI mode is enabled by default when you invoke @value{GDBN} as
22361 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22362 You can also switch in and out of TUI mode while @value{GDBN} runs by
22363 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22364 @xref{TUI Keys, ,TUI Key Bindings}.
22367 @section TUI Overview
22369 In TUI mode, @value{GDBN} can display several text windows:
22373 This window is the @value{GDBN} command window with the @value{GDBN}
22374 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22375 managed using readline.
22378 The source window shows the source file of the program. The current
22379 line and active breakpoints are displayed in this window.
22382 The assembly window shows the disassembly output of the program.
22385 This window shows the processor registers. Registers are highlighted
22386 when their values change.
22389 The source and assembly windows show the current program position
22390 by highlighting the current line and marking it with a @samp{>} marker.
22391 Breakpoints are indicated with two markers. The first marker
22392 indicates the breakpoint type:
22396 Breakpoint which was hit at least once.
22399 Breakpoint which was never hit.
22402 Hardware breakpoint which was hit at least once.
22405 Hardware breakpoint which was never hit.
22408 The second marker indicates whether the breakpoint is enabled or not:
22412 Breakpoint is enabled.
22415 Breakpoint is disabled.
22418 The source, assembly and register windows are updated when the current
22419 thread changes, when the frame changes, or when the program counter
22422 These windows are not all visible at the same time. The command
22423 window is always visible. The others can be arranged in several
22434 source and assembly,
22437 source and registers, or
22440 assembly and registers.
22443 A status line above the command window shows the following information:
22447 Indicates the current @value{GDBN} target.
22448 (@pxref{Targets, ,Specifying a Debugging Target}).
22451 Gives the current process or thread number.
22452 When no process is being debugged, this field is set to @code{No process}.
22455 Gives the current function name for the selected frame.
22456 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22457 When there is no symbol corresponding to the current program counter,
22458 the string @code{??} is displayed.
22461 Indicates the current line number for the selected frame.
22462 When the current line number is not known, the string @code{??} is displayed.
22465 Indicates the current program counter address.
22469 @section TUI Key Bindings
22470 @cindex TUI key bindings
22472 The TUI installs several key bindings in the readline keymaps
22473 (@pxref{Command Line Editing}). The following key bindings
22474 are installed for both TUI mode and the @value{GDBN} standard mode.
22483 Enter or leave the TUI mode. When leaving the TUI mode,
22484 the curses window management stops and @value{GDBN} operates using
22485 its standard mode, writing on the terminal directly. When reentering
22486 the TUI mode, control is given back to the curses windows.
22487 The screen is then refreshed.
22491 Use a TUI layout with only one window. The layout will
22492 either be @samp{source} or @samp{assembly}. When the TUI mode
22493 is not active, it will switch to the TUI mode.
22495 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22499 Use a TUI layout with at least two windows. When the current
22500 layout already has two windows, the next layout with two windows is used.
22501 When a new layout is chosen, one window will always be common to the
22502 previous layout and the new one.
22504 Think of it as the Emacs @kbd{C-x 2} binding.
22508 Change the active window. The TUI associates several key bindings
22509 (like scrolling and arrow keys) with the active window. This command
22510 gives the focus to the next TUI window.
22512 Think of it as the Emacs @kbd{C-x o} binding.
22516 Switch in and out of the TUI SingleKey mode that binds single
22517 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22520 The following key bindings only work in the TUI mode:
22525 Scroll the active window one page up.
22529 Scroll the active window one page down.
22533 Scroll the active window one line up.
22537 Scroll the active window one line down.
22541 Scroll the active window one column left.
22545 Scroll the active window one column right.
22549 Refresh the screen.
22552 Because the arrow keys scroll the active window in the TUI mode, they
22553 are not available for their normal use by readline unless the command
22554 window has the focus. When another window is active, you must use
22555 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22556 and @kbd{C-f} to control the command window.
22558 @node TUI Single Key Mode
22559 @section TUI Single Key Mode
22560 @cindex TUI single key mode
22562 The TUI also provides a @dfn{SingleKey} mode, which binds several
22563 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22564 switch into this mode, where the following key bindings are used:
22567 @kindex c @r{(SingleKey TUI key)}
22571 @kindex d @r{(SingleKey TUI key)}
22575 @kindex f @r{(SingleKey TUI key)}
22579 @kindex n @r{(SingleKey TUI key)}
22583 @kindex q @r{(SingleKey TUI key)}
22585 exit the SingleKey mode.
22587 @kindex r @r{(SingleKey TUI key)}
22591 @kindex s @r{(SingleKey TUI key)}
22595 @kindex u @r{(SingleKey TUI key)}
22599 @kindex v @r{(SingleKey TUI key)}
22603 @kindex w @r{(SingleKey TUI key)}
22608 Other keys temporarily switch to the @value{GDBN} command prompt.
22609 The key that was pressed is inserted in the editing buffer so that
22610 it is possible to type most @value{GDBN} commands without interaction
22611 with the TUI SingleKey mode. Once the command is entered the TUI
22612 SingleKey mode is restored. The only way to permanently leave
22613 this mode is by typing @kbd{q} or @kbd{C-x s}.
22617 @section TUI-specific Commands
22618 @cindex TUI commands
22620 The TUI has specific commands to control the text windows.
22621 These commands are always available, even when @value{GDBN} is not in
22622 the TUI mode. When @value{GDBN} is in the standard mode, most
22623 of these commands will automatically switch to the TUI mode.
22625 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22626 terminal, or @value{GDBN} has been started with the machine interface
22627 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22628 these commands will fail with an error, because it would not be
22629 possible or desirable to enable curses window management.
22634 List and give the size of all displayed windows.
22638 Display the next layout.
22641 Display the previous layout.
22644 Display the source window only.
22647 Display the assembly window only.
22650 Display the source and assembly window.
22653 Display the register window together with the source or assembly window.
22657 Make the next window active for scrolling.
22660 Make the previous window active for scrolling.
22663 Make the source window active for scrolling.
22666 Make the assembly window active for scrolling.
22669 Make the register window active for scrolling.
22672 Make the command window active for scrolling.
22676 Refresh the screen. This is similar to typing @kbd{C-L}.
22678 @item tui reg float
22680 Show the floating point registers in the register window.
22682 @item tui reg general
22683 Show the general registers in the register window.
22686 Show the next register group. The list of register groups as well as
22687 their order is target specific. The predefined register groups are the
22688 following: @code{general}, @code{float}, @code{system}, @code{vector},
22689 @code{all}, @code{save}, @code{restore}.
22691 @item tui reg system
22692 Show the system registers in the register window.
22696 Update the source window and the current execution point.
22698 @item winheight @var{name} +@var{count}
22699 @itemx winheight @var{name} -@var{count}
22701 Change the height of the window @var{name} by @var{count}
22702 lines. Positive counts increase the height, while negative counts
22705 @item tabset @var{nchars}
22707 Set the width of tab stops to be @var{nchars} characters.
22710 @node TUI Configuration
22711 @section TUI Configuration Variables
22712 @cindex TUI configuration variables
22714 Several configuration variables control the appearance of TUI windows.
22717 @item set tui border-kind @var{kind}
22718 @kindex set tui border-kind
22719 Select the border appearance for the source, assembly and register windows.
22720 The possible values are the following:
22723 Use a space character to draw the border.
22726 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22729 Use the Alternate Character Set to draw the border. The border is
22730 drawn using character line graphics if the terminal supports them.
22733 @item set tui border-mode @var{mode}
22734 @kindex set tui border-mode
22735 @itemx set tui active-border-mode @var{mode}
22736 @kindex set tui active-border-mode
22737 Select the display attributes for the borders of the inactive windows
22738 or the active window. The @var{mode} can be one of the following:
22741 Use normal attributes to display the border.
22747 Use reverse video mode.
22750 Use half bright mode.
22752 @item half-standout
22753 Use half bright and standout mode.
22756 Use extra bright or bold mode.
22758 @item bold-standout
22759 Use extra bright or bold and standout mode.
22764 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22767 @cindex @sc{gnu} Emacs
22768 A special interface allows you to use @sc{gnu} Emacs to view (and
22769 edit) the source files for the program you are debugging with
22772 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22773 executable file you want to debug as an argument. This command starts
22774 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22775 created Emacs buffer.
22776 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22778 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22783 All ``terminal'' input and output goes through an Emacs buffer, called
22786 This applies both to @value{GDBN} commands and their output, and to the input
22787 and output done by the program you are debugging.
22789 This is useful because it means that you can copy the text of previous
22790 commands and input them again; you can even use parts of the output
22793 All the facilities of Emacs' Shell mode are available for interacting
22794 with your program. In particular, you can send signals the usual
22795 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22799 @value{GDBN} displays source code through Emacs.
22801 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22802 source file for that frame and puts an arrow (@samp{=>}) at the
22803 left margin of the current line. Emacs uses a separate buffer for
22804 source display, and splits the screen to show both your @value{GDBN} session
22807 Explicit @value{GDBN} @code{list} or search commands still produce output as
22808 usual, but you probably have no reason to use them from Emacs.
22811 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22812 a graphical mode, enabled by default, which provides further buffers
22813 that can control the execution and describe the state of your program.
22814 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22816 If you specify an absolute file name when prompted for the @kbd{M-x
22817 gdb} argument, then Emacs sets your current working directory to where
22818 your program resides. If you only specify the file name, then Emacs
22819 sets your current working directory to to the directory associated
22820 with the previous buffer. In this case, @value{GDBN} may find your
22821 program by searching your environment's @code{PATH} variable, but on
22822 some operating systems it might not find the source. So, although the
22823 @value{GDBN} input and output session proceeds normally, the auxiliary
22824 buffer does not display the current source and line of execution.
22826 The initial working directory of @value{GDBN} is printed on the top
22827 line of the GUD buffer and this serves as a default for the commands
22828 that specify files for @value{GDBN} to operate on. @xref{Files,
22829 ,Commands to Specify Files}.
22831 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
22832 need to call @value{GDBN} by a different name (for example, if you
22833 keep several configurations around, with different names) you can
22834 customize the Emacs variable @code{gud-gdb-command-name} to run the
22837 In the GUD buffer, you can use these special Emacs commands in
22838 addition to the standard Shell mode commands:
22842 Describe the features of Emacs' GUD Mode.
22845 Execute to another source line, like the @value{GDBN} @code{step} command; also
22846 update the display window to show the current file and location.
22849 Execute to next source line in this function, skipping all function
22850 calls, like the @value{GDBN} @code{next} command. Then update the display window
22851 to show the current file and location.
22854 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
22855 display window accordingly.
22858 Execute until exit from the selected stack frame, like the @value{GDBN}
22859 @code{finish} command.
22862 Continue execution of your program, like the @value{GDBN} @code{continue}
22866 Go up the number of frames indicated by the numeric argument
22867 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
22868 like the @value{GDBN} @code{up} command.
22871 Go down the number of frames indicated by the numeric argument, like the
22872 @value{GDBN} @code{down} command.
22875 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
22876 tells @value{GDBN} to set a breakpoint on the source line point is on.
22878 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
22879 separate frame which shows a backtrace when the GUD buffer is current.
22880 Move point to any frame in the stack and type @key{RET} to make it
22881 become the current frame and display the associated source in the
22882 source buffer. Alternatively, click @kbd{Mouse-2} to make the
22883 selected frame become the current one. In graphical mode, the
22884 speedbar displays watch expressions.
22886 If you accidentally delete the source-display buffer, an easy way to get
22887 it back is to type the command @code{f} in the @value{GDBN} buffer, to
22888 request a frame display; when you run under Emacs, this recreates
22889 the source buffer if necessary to show you the context of the current
22892 The source files displayed in Emacs are in ordinary Emacs buffers
22893 which are visiting the source files in the usual way. You can edit
22894 the files with these buffers if you wish; but keep in mind that @value{GDBN}
22895 communicates with Emacs in terms of line numbers. If you add or
22896 delete lines from the text, the line numbers that @value{GDBN} knows cease
22897 to correspond properly with the code.
22899 A more detailed description of Emacs' interaction with @value{GDBN} is
22900 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
22903 @c The following dropped because Epoch is nonstandard. Reactivate
22904 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
22906 @kindex Emacs Epoch environment
22910 Version 18 of @sc{gnu} Emacs has a built-in window system
22911 called the @code{epoch}
22912 environment. Users of this environment can use a new command,
22913 @code{inspect} which performs identically to @code{print} except that
22914 each value is printed in its own window.
22919 @chapter The @sc{gdb/mi} Interface
22921 @unnumberedsec Function and Purpose
22923 @cindex @sc{gdb/mi}, its purpose
22924 @sc{gdb/mi} is a line based machine oriented text interface to
22925 @value{GDBN} and is activated by specifying using the
22926 @option{--interpreter} command line option (@pxref{Mode Options}). It
22927 is specifically intended to support the development of systems which
22928 use the debugger as just one small component of a larger system.
22930 This chapter is a specification of the @sc{gdb/mi} interface. It is written
22931 in the form of a reference manual.
22933 Note that @sc{gdb/mi} is still under construction, so some of the
22934 features described below are incomplete and subject to change
22935 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
22937 @unnumberedsec Notation and Terminology
22939 @cindex notational conventions, for @sc{gdb/mi}
22940 This chapter uses the following notation:
22944 @code{|} separates two alternatives.
22947 @code{[ @var{something} ]} indicates that @var{something} is optional:
22948 it may or may not be given.
22951 @code{( @var{group} )*} means that @var{group} inside the parentheses
22952 may repeat zero or more times.
22955 @code{( @var{group} )+} means that @var{group} inside the parentheses
22956 may repeat one or more times.
22959 @code{"@var{string}"} means a literal @var{string}.
22963 @heading Dependencies
22967 * GDB/MI General Design::
22968 * GDB/MI Command Syntax::
22969 * GDB/MI Compatibility with CLI::
22970 * GDB/MI Development and Front Ends::
22971 * GDB/MI Output Records::
22972 * GDB/MI Simple Examples::
22973 * GDB/MI Command Description Format::
22974 * GDB/MI Breakpoint Commands::
22975 * GDB/MI Program Context::
22976 * GDB/MI Thread Commands::
22977 * GDB/MI Program Execution::
22978 * GDB/MI Stack Manipulation::
22979 * GDB/MI Variable Objects::
22980 * GDB/MI Data Manipulation::
22981 * GDB/MI Tracepoint Commands::
22982 * GDB/MI Symbol Query::
22983 * GDB/MI File Commands::
22985 * GDB/MI Kod Commands::
22986 * GDB/MI Memory Overlay Commands::
22987 * GDB/MI Signal Handling Commands::
22989 * GDB/MI Target Manipulation::
22990 * GDB/MI File Transfer Commands::
22991 * GDB/MI Miscellaneous Commands::
22994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22995 @node GDB/MI General Design
22996 @section @sc{gdb/mi} General Design
22997 @cindex GDB/MI General Design
22999 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23000 parts---commands sent to @value{GDBN}, responses to those commands
23001 and notifications. Each command results in exactly one response,
23002 indicating either successful completion of the command, or an error.
23003 For the commands that do not resume the target, the response contains the
23004 requested information. For the commands that resume the target, the
23005 response only indicates whether the target was successfully resumed.
23006 Notifications is the mechanism for reporting changes in the state of the
23007 target, or in @value{GDBN} state, that cannot conveniently be associated with
23008 a command and reported as part of that command response.
23010 The important examples of notifications are:
23014 Exec notifications. These are used to report changes in
23015 target state---when a target is resumed, or stopped. It would not
23016 be feasible to include this information in response of resuming
23017 commands, because one resume commands can result in multiple events in
23018 different threads. Also, quite some time may pass before any event
23019 happens in the target, while a frontend needs to know whether the resuming
23020 command itself was successfully executed.
23023 Console output, and status notifications. Console output
23024 notifications are used to report output of CLI commands, as well as
23025 diagnostics for other commands. Status notifications are used to
23026 report the progress of a long-running operation. Naturally, including
23027 this information in command response would mean no output is produced
23028 until the command is finished, which is undesirable.
23031 General notifications. Commands may have various side effects on
23032 the @value{GDBN} or target state beyond their official purpose. For example,
23033 a command may change the selected thread. Although such changes can
23034 be included in command response, using notification allows for more
23035 orthogonal frontend design.
23039 There's no guarantee that whenever an MI command reports an error,
23040 @value{GDBN} or the target are in any specific state, and especially,
23041 the state is not reverted to the state before the MI command was
23042 processed. Therefore, whenever an MI command results in an error,
23043 we recommend that the frontend refreshes all the information shown in
23044 the user interface.
23048 * Context management::
23049 * Asynchronous and non-stop modes::
23053 @node Context management
23054 @subsection Context management
23056 In most cases when @value{GDBN} accesses the target, this access is
23057 done in context of a specific thread and frame (@pxref{Frames}).
23058 Often, even when accessing global data, the target requires that a thread
23059 be specified. The CLI interface maintains the selected thread and frame,
23060 and supplies them to target on each command. This is convenient,
23061 because a command line user would not want to specify that information
23062 explicitly on each command, and because user interacts with
23063 @value{GDBN} via a single terminal, so no confusion is possible as
23064 to what thread and frame are the current ones.
23066 In the case of MI, the concept of selected thread and frame is less
23067 useful. First, a frontend can easily remember this information
23068 itself. Second, a graphical frontend can have more than one window,
23069 each one used for debugging a different thread, and the frontend might
23070 want to access additional threads for internal purposes. This
23071 increases the risk that by relying on implicitly selected thread, the
23072 frontend may be operating on a wrong one. Therefore, each MI command
23073 should explicitly specify which thread and frame to operate on. To
23074 make it possible, each MI command accepts the @samp{--thread} and
23075 @samp{--frame} options, the value to each is @value{GDBN} identifier
23076 for thread and frame to operate on.
23078 Usually, each top-level window in a frontend allows the user to select
23079 a thread and a frame, and remembers the user selection for further
23080 operations. However, in some cases @value{GDBN} may suggest that the
23081 current thread be changed. For example, when stopping on a breakpoint
23082 it is reasonable to switch to the thread where breakpoint is hit. For
23083 another example, if the user issues the CLI @samp{thread} command via
23084 the frontend, it is desirable to change the frontend's selected thread to the
23085 one specified by user. @value{GDBN} communicates the suggestion to
23086 change current thread using the @samp{=thread-selected} notification.
23087 No such notification is available for the selected frame at the moment.
23089 Note that historically, MI shares the selected thread with CLI, so
23090 frontends used the @code{-thread-select} to execute commands in the
23091 right context. However, getting this to work right is cumbersome. The
23092 simplest way is for frontend to emit @code{-thread-select} command
23093 before every command. This doubles the number of commands that need
23094 to be sent. The alternative approach is to suppress @code{-thread-select}
23095 if the selected thread in @value{GDBN} is supposed to be identical to the
23096 thread the frontend wants to operate on. However, getting this
23097 optimization right can be tricky. In particular, if the frontend
23098 sends several commands to @value{GDBN}, and one of the commands changes the
23099 selected thread, then the behaviour of subsequent commands will
23100 change. So, a frontend should either wait for response from such
23101 problematic commands, or explicitly add @code{-thread-select} for
23102 all subsequent commands. No frontend is known to do this exactly
23103 right, so it is suggested to just always pass the @samp{--thread} and
23104 @samp{--frame} options.
23106 @node Asynchronous and non-stop modes
23107 @subsection Asynchronous command execution and non-stop mode
23109 On some targets, @value{GDBN} is capable of processing MI commands
23110 even while the target is running. This is called @dfn{asynchronous
23111 command execution} (@pxref{Background Execution}). The frontend may
23112 specify a preferrence for asynchronous execution using the
23113 @code{-gdb-set target-async 1} command, which should be emitted before
23114 either running the executable or attaching to the target. After the
23115 frontend has started the executable or attached to the target, it can
23116 find if asynchronous execution is enabled using the
23117 @code{-list-target-features} command.
23119 Even if @value{GDBN} can accept a command while target is running,
23120 many commands that access the target do not work when the target is
23121 running. Therefore, asynchronous command execution is most useful
23122 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23123 it is possible to examine the state of one thread, while other threads
23126 When a given thread is running, MI commands that try to access the
23127 target in the context of that thread may not work, or may work only on
23128 some targets. In particular, commands that try to operate on thread's
23129 stack will not work, on any target. Commands that read memory, or
23130 modify breakpoints, may work or not work, depending on the target. Note
23131 that even commands that operate on global state, such as @code{print},
23132 @code{set}, and breakpoint commands, still access the target in the
23133 context of a specific thread, so frontend should try to find a
23134 stopped thread and perform the operation on that thread (using the
23135 @samp{--thread} option).
23137 Which commands will work in the context of a running thread is
23138 highly target dependent. However, the two commands
23139 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23140 to find the state of a thread, will always work.
23142 @node Thread groups
23143 @subsection Thread groups
23144 @value{GDBN} may be used to debug several processes at the same time.
23145 On some platfroms, @value{GDBN} may support debugging of several
23146 hardware systems, each one having several cores with several different
23147 processes running on each core. This section describes the MI
23148 mechanism to support such debugging scenarios.
23150 The key observation is that regardless of the structure of the
23151 target, MI can have a global list of threads, because most commands that
23152 accept the @samp{--thread} option do not need to know what process that
23153 thread belongs to. Therefore, it is not necessary to introduce
23154 neither additional @samp{--process} option, nor an notion of the
23155 current process in the MI interface. The only strictly new feature
23156 that is required is the ability to find how the threads are grouped
23159 To allow the user to discover such grouping, and to support arbitrary
23160 hierarchy of machines/cores/processes, MI introduces the concept of a
23161 @dfn{thread group}. Thread group is a collection of threads and other
23162 thread groups. A thread group always has a string identifier, a type,
23163 and may have additional attributes specific to the type. A new
23164 command, @code{-list-thread-groups}, returns the list of top-level
23165 thread groups, which correspond to processes that @value{GDBN} is
23166 debugging at the moment. By passing an identifier of a thread group
23167 to the @code{-list-thread-groups} command, it is possible to obtain
23168 the members of specific thread group.
23170 To allow the user to easily discover processes, and other objects, he
23171 wishes to debug, a concept of @dfn{available thread group} is
23172 introduced. Available thread group is an thread group that
23173 @value{GDBN} is not debugging, but that can be attached to, using the
23174 @code{-target-attach} command. The list of available top-level thread
23175 groups can be obtained using @samp{-list-thread-groups --available}.
23176 In general, the content of a thread group may be only retrieved only
23177 after attaching to that thread group.
23179 Thread groups are related to inferiors (@pxref{Inferiors and
23180 Programs}). Each inferior corresponds to a thread group of a special
23181 type @samp{process}, and some additional operations are permitted on
23182 such thread groups.
23184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23185 @node GDB/MI Command Syntax
23186 @section @sc{gdb/mi} Command Syntax
23189 * GDB/MI Input Syntax::
23190 * GDB/MI Output Syntax::
23193 @node GDB/MI Input Syntax
23194 @subsection @sc{gdb/mi} Input Syntax
23196 @cindex input syntax for @sc{gdb/mi}
23197 @cindex @sc{gdb/mi}, input syntax
23199 @item @var{command} @expansion{}
23200 @code{@var{cli-command} | @var{mi-command}}
23202 @item @var{cli-command} @expansion{}
23203 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23204 @var{cli-command} is any existing @value{GDBN} CLI command.
23206 @item @var{mi-command} @expansion{}
23207 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23208 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23210 @item @var{token} @expansion{}
23211 "any sequence of digits"
23213 @item @var{option} @expansion{}
23214 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23216 @item @var{parameter} @expansion{}
23217 @code{@var{non-blank-sequence} | @var{c-string}}
23219 @item @var{operation} @expansion{}
23220 @emph{any of the operations described in this chapter}
23222 @item @var{non-blank-sequence} @expansion{}
23223 @emph{anything, provided it doesn't contain special characters such as
23224 "-", @var{nl}, """ and of course " "}
23226 @item @var{c-string} @expansion{}
23227 @code{""" @var{seven-bit-iso-c-string-content} """}
23229 @item @var{nl} @expansion{}
23238 The CLI commands are still handled by the @sc{mi} interpreter; their
23239 output is described below.
23242 The @code{@var{token}}, when present, is passed back when the command
23246 Some @sc{mi} commands accept optional arguments as part of the parameter
23247 list. Each option is identified by a leading @samp{-} (dash) and may be
23248 followed by an optional argument parameter. Options occur first in the
23249 parameter list and can be delimited from normal parameters using
23250 @samp{--} (this is useful when some parameters begin with a dash).
23257 We want easy access to the existing CLI syntax (for debugging).
23260 We want it to be easy to spot a @sc{mi} operation.
23263 @node GDB/MI Output Syntax
23264 @subsection @sc{gdb/mi} Output Syntax
23266 @cindex output syntax of @sc{gdb/mi}
23267 @cindex @sc{gdb/mi}, output syntax
23268 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23269 followed, optionally, by a single result record. This result record
23270 is for the most recent command. The sequence of output records is
23271 terminated by @samp{(gdb)}.
23273 If an input command was prefixed with a @code{@var{token}} then the
23274 corresponding output for that command will also be prefixed by that same
23278 @item @var{output} @expansion{}
23279 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23281 @item @var{result-record} @expansion{}
23282 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23284 @item @var{out-of-band-record} @expansion{}
23285 @code{@var{async-record} | @var{stream-record}}
23287 @item @var{async-record} @expansion{}
23288 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23290 @item @var{exec-async-output} @expansion{}
23291 @code{[ @var{token} ] "*" @var{async-output}}
23293 @item @var{status-async-output} @expansion{}
23294 @code{[ @var{token} ] "+" @var{async-output}}
23296 @item @var{notify-async-output} @expansion{}
23297 @code{[ @var{token} ] "=" @var{async-output}}
23299 @item @var{async-output} @expansion{}
23300 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23302 @item @var{result-class} @expansion{}
23303 @code{"done" | "running" | "connected" | "error" | "exit"}
23305 @item @var{async-class} @expansion{}
23306 @code{"stopped" | @var{others}} (where @var{others} will be added
23307 depending on the needs---this is still in development).
23309 @item @var{result} @expansion{}
23310 @code{ @var{variable} "=" @var{value}}
23312 @item @var{variable} @expansion{}
23313 @code{ @var{string} }
23315 @item @var{value} @expansion{}
23316 @code{ @var{const} | @var{tuple} | @var{list} }
23318 @item @var{const} @expansion{}
23319 @code{@var{c-string}}
23321 @item @var{tuple} @expansion{}
23322 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23324 @item @var{list} @expansion{}
23325 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23326 @var{result} ( "," @var{result} )* "]" }
23328 @item @var{stream-record} @expansion{}
23329 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23331 @item @var{console-stream-output} @expansion{}
23332 @code{"~" @var{c-string}}
23334 @item @var{target-stream-output} @expansion{}
23335 @code{"@@" @var{c-string}}
23337 @item @var{log-stream-output} @expansion{}
23338 @code{"&" @var{c-string}}
23340 @item @var{nl} @expansion{}
23343 @item @var{token} @expansion{}
23344 @emph{any sequence of digits}.
23352 All output sequences end in a single line containing a period.
23355 The @code{@var{token}} is from the corresponding request. Note that
23356 for all async output, while the token is allowed by the grammar and
23357 may be output by future versions of @value{GDBN} for select async
23358 output messages, it is generally omitted. Frontends should treat
23359 all async output as reporting general changes in the state of the
23360 target and there should be no need to associate async output to any
23364 @cindex status output in @sc{gdb/mi}
23365 @var{status-async-output} contains on-going status information about the
23366 progress of a slow operation. It can be discarded. All status output is
23367 prefixed by @samp{+}.
23370 @cindex async output in @sc{gdb/mi}
23371 @var{exec-async-output} contains asynchronous state change on the target
23372 (stopped, started, disappeared). All async output is prefixed by
23376 @cindex notify output in @sc{gdb/mi}
23377 @var{notify-async-output} contains supplementary information that the
23378 client should handle (e.g., a new breakpoint information). All notify
23379 output is prefixed by @samp{=}.
23382 @cindex console output in @sc{gdb/mi}
23383 @var{console-stream-output} is output that should be displayed as is in the
23384 console. It is the textual response to a CLI command. All the console
23385 output is prefixed by @samp{~}.
23388 @cindex target output in @sc{gdb/mi}
23389 @var{target-stream-output} is the output produced by the target program.
23390 All the target output is prefixed by @samp{@@}.
23393 @cindex log output in @sc{gdb/mi}
23394 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23395 instance messages that should be displayed as part of an error log. All
23396 the log output is prefixed by @samp{&}.
23399 @cindex list output in @sc{gdb/mi}
23400 New @sc{gdb/mi} commands should only output @var{lists} containing
23406 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23407 details about the various output records.
23409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23410 @node GDB/MI Compatibility with CLI
23411 @section @sc{gdb/mi} Compatibility with CLI
23413 @cindex compatibility, @sc{gdb/mi} and CLI
23414 @cindex @sc{gdb/mi}, compatibility with CLI
23416 For the developers convenience CLI commands can be entered directly,
23417 but there may be some unexpected behaviour. For example, commands
23418 that query the user will behave as if the user replied yes, breakpoint
23419 command lists are not executed and some CLI commands, such as
23420 @code{if}, @code{when} and @code{define}, prompt for further input with
23421 @samp{>}, which is not valid MI output.
23423 This feature may be removed at some stage in the future and it is
23424 recommended that front ends use the @code{-interpreter-exec} command
23425 (@pxref{-interpreter-exec}).
23427 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23428 @node GDB/MI Development and Front Ends
23429 @section @sc{gdb/mi} Development and Front Ends
23430 @cindex @sc{gdb/mi} development
23432 The application which takes the MI output and presents the state of the
23433 program being debugged to the user is called a @dfn{front end}.
23435 Although @sc{gdb/mi} is still incomplete, it is currently being used
23436 by a variety of front ends to @value{GDBN}. This makes it difficult
23437 to introduce new functionality without breaking existing usage. This
23438 section tries to minimize the problems by describing how the protocol
23441 Some changes in MI need not break a carefully designed front end, and
23442 for these the MI version will remain unchanged. The following is a
23443 list of changes that may occur within one level, so front ends should
23444 parse MI output in a way that can handle them:
23448 New MI commands may be added.
23451 New fields may be added to the output of any MI command.
23454 The range of values for fields with specified values, e.g.,
23455 @code{in_scope} (@pxref{-var-update}) may be extended.
23457 @c The format of field's content e.g type prefix, may change so parse it
23458 @c at your own risk. Yes, in general?
23460 @c The order of fields may change? Shouldn't really matter but it might
23461 @c resolve inconsistencies.
23464 If the changes are likely to break front ends, the MI version level
23465 will be increased by one. This will allow the front end to parse the
23466 output according to the MI version. Apart from mi0, new versions of
23467 @value{GDBN} will not support old versions of MI and it will be the
23468 responsibility of the front end to work with the new one.
23470 @c Starting with mi3, add a new command -mi-version that prints the MI
23473 The best way to avoid unexpected changes in MI that might break your front
23474 end is to make your project known to @value{GDBN} developers and
23475 follow development on @email{gdb@@sourceware.org} and
23476 @email{gdb-patches@@sourceware.org}.
23477 @cindex mailing lists
23479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23480 @node GDB/MI Output Records
23481 @section @sc{gdb/mi} Output Records
23484 * GDB/MI Result Records::
23485 * GDB/MI Stream Records::
23486 * GDB/MI Async Records::
23487 * GDB/MI Frame Information::
23488 * GDB/MI Thread Information::
23491 @node GDB/MI Result Records
23492 @subsection @sc{gdb/mi} Result Records
23494 @cindex result records in @sc{gdb/mi}
23495 @cindex @sc{gdb/mi}, result records
23496 In addition to a number of out-of-band notifications, the response to a
23497 @sc{gdb/mi} command includes one of the following result indications:
23501 @item "^done" [ "," @var{results} ]
23502 The synchronous operation was successful, @code{@var{results}} are the return
23507 This result record is equivalent to @samp{^done}. Historically, it
23508 was output instead of @samp{^done} if the command has resumed the
23509 target. This behaviour is maintained for backward compatibility, but
23510 all frontends should treat @samp{^done} and @samp{^running}
23511 identically and rely on the @samp{*running} output record to determine
23512 which threads are resumed.
23516 @value{GDBN} has connected to a remote target.
23518 @item "^error" "," @var{c-string}
23520 The operation failed. The @code{@var{c-string}} contains the corresponding
23525 @value{GDBN} has terminated.
23529 @node GDB/MI Stream Records
23530 @subsection @sc{gdb/mi} Stream Records
23532 @cindex @sc{gdb/mi}, stream records
23533 @cindex stream records in @sc{gdb/mi}
23534 @value{GDBN} internally maintains a number of output streams: the console, the
23535 target, and the log. The output intended for each of these streams is
23536 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23538 Each stream record begins with a unique @dfn{prefix character} which
23539 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23540 Syntax}). In addition to the prefix, each stream record contains a
23541 @code{@var{string-output}}. This is either raw text (with an implicit new
23542 line) or a quoted C string (which does not contain an implicit newline).
23545 @item "~" @var{string-output}
23546 The console output stream contains text that should be displayed in the
23547 CLI console window. It contains the textual responses to CLI commands.
23549 @item "@@" @var{string-output}
23550 The target output stream contains any textual output from the running
23551 target. This is only present when GDB's event loop is truly
23552 asynchronous, which is currently only the case for remote targets.
23554 @item "&" @var{string-output}
23555 The log stream contains debugging messages being produced by @value{GDBN}'s
23559 @node GDB/MI Async Records
23560 @subsection @sc{gdb/mi} Async Records
23562 @cindex async records in @sc{gdb/mi}
23563 @cindex @sc{gdb/mi}, async records
23564 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23565 additional changes that have occurred. Those changes can either be a
23566 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23567 target activity (e.g., target stopped).
23569 The following is the list of possible async records:
23573 @item *running,thread-id="@var{thread}"
23574 The target is now running. The @var{thread} field tells which
23575 specific thread is now running, and can be @samp{all} if all threads
23576 are running. The frontend should assume that no interaction with a
23577 running thread is possible after this notification is produced.
23578 The frontend should not assume that this notification is output
23579 only once for any command. @value{GDBN} may emit this notification
23580 several times, either for different threads, because it cannot resume
23581 all threads together, or even for a single thread, if the thread must
23582 be stepped though some code before letting it run freely.
23584 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23585 The target has stopped. The @var{reason} field can have one of the
23589 @item breakpoint-hit
23590 A breakpoint was reached.
23591 @item watchpoint-trigger
23592 A watchpoint was triggered.
23593 @item read-watchpoint-trigger
23594 A read watchpoint was triggered.
23595 @item access-watchpoint-trigger
23596 An access watchpoint was triggered.
23597 @item function-finished
23598 An -exec-finish or similar CLI command was accomplished.
23599 @item location-reached
23600 An -exec-until or similar CLI command was accomplished.
23601 @item watchpoint-scope
23602 A watchpoint has gone out of scope.
23603 @item end-stepping-range
23604 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23605 similar CLI command was accomplished.
23606 @item exited-signalled
23607 The inferior exited because of a signal.
23609 The inferior exited.
23610 @item exited-normally
23611 The inferior exited normally.
23612 @item signal-received
23613 A signal was received by the inferior.
23616 The @var{id} field identifies the thread that directly caused the stop
23617 -- for example by hitting a breakpoint. Depending on whether all-stop
23618 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23619 stop all threads, or only the thread that directly triggered the stop.
23620 If all threads are stopped, the @var{stopped} field will have the
23621 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23622 field will be a list of thread identifiers. Presently, this list will
23623 always include a single thread, but frontend should be prepared to see
23624 several threads in the list. The @var{core} field reports the
23625 processor core on which the stop event has happened. This field may be absent
23626 if such information is not available.
23628 @item =thread-group-added,id="@var{id}"
23629 @itemx =thread-group-removed,id="@var{id}"
23630 A thread group was either added or removed. The @var{id} field
23631 contains the @value{GDBN} identifier of the thread group. When a thread
23632 group is added, it generally might not be associated with a running
23633 process. When a thread group is removed, its id becomes invalid and
23634 cannot be used in any way.
23636 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23637 A thread group became associated with a running program,
23638 either because the program was just started or the thread group
23639 was attached to a program. The @var{id} field contains the
23640 @value{GDBN} identifier of the thread group. The @var{pid} field
23641 contains process identifier, specific to the operating system.
23643 @itemx =thread-group-exited,id="@var{id}"
23644 A thread group is no longer associated with a running program,
23645 either because the program has exited, or because it was detached
23646 from. The @var{id} field contains the @value{GDBN} identifier of the
23649 @item =thread-created,id="@var{id}",group-id="@var{gid}"
23650 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
23651 A thread either was created, or has exited. The @var{id} field
23652 contains the @value{GDBN} identifier of the thread. The @var{gid}
23653 field identifies the thread group this thread belongs to.
23655 @item =thread-selected,id="@var{id}"
23656 Informs that the selected thread was changed as result of the last
23657 command. This notification is not emitted as result of @code{-thread-select}
23658 command but is emitted whenever an MI command that is not documented
23659 to change the selected thread actually changes it. In particular,
23660 invoking, directly or indirectly (via user-defined command), the CLI
23661 @code{thread} command, will generate this notification.
23663 We suggest that in response to this notification, front ends
23664 highlight the selected thread and cause subsequent commands to apply to
23667 @item =library-loaded,...
23668 Reports that a new library file was loaded by the program. This
23669 notification has 4 fields---@var{id}, @var{target-name},
23670 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23671 opaque identifier of the library. For remote debugging case,
23672 @var{target-name} and @var{host-name} fields give the name of the
23673 library file on the target, and on the host respectively. For native
23674 debugging, both those fields have the same value. The
23675 @var{symbols-loaded} field reports if the debug symbols for this
23676 library are loaded. The @var{thread-group} field, if present,
23677 specifies the id of the thread group in whose context the library was loaded.
23678 If the field is absent, it means the library was loaded in the context
23679 of all present thread groups.
23681 @item =library-unloaded,...
23682 Reports that a library was unloaded by the program. This notification
23683 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23684 the same meaning as for the @code{=library-loaded} notification.
23685 The @var{thread-group} field, if present, specifies the id of the
23686 thread group in whose context the library was unloaded. If the field is
23687 absent, it means the library was unloaded in the context of all present
23692 @node GDB/MI Frame Information
23693 @subsection @sc{gdb/mi} Frame Information
23695 Response from many MI commands includes an information about stack
23696 frame. This information is a tuple that may have the following
23701 The level of the stack frame. The innermost frame has the level of
23702 zero. This field is always present.
23705 The name of the function corresponding to the frame. This field may
23706 be absent if @value{GDBN} is unable to determine the function name.
23709 The code address for the frame. This field is always present.
23712 The name of the source files that correspond to the frame's code
23713 address. This field may be absent.
23716 The source line corresponding to the frames' code address. This field
23720 The name of the binary file (either executable or shared library) the
23721 corresponds to the frame's code address. This field may be absent.
23725 @node GDB/MI Thread Information
23726 @subsection @sc{gdb/mi} Thread Information
23728 Whenever @value{GDBN} has to report an information about a thread, it
23729 uses a tuple with the following fields:
23733 The numeric id assigned to the thread by @value{GDBN}. This field is
23737 Target-specific string identifying the thread. This field is always present.
23740 Additional information about the thread provided by the target.
23741 It is supposed to be human-readable and not interpreted by the
23742 frontend. This field is optional.
23745 Either @samp{stopped} or @samp{running}, depending on whether the
23746 thread is presently running. This field is always present.
23749 The value of this field is an integer number of the processor core the
23750 thread was last seen on. This field is optional.
23754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23755 @node GDB/MI Simple Examples
23756 @section Simple Examples of @sc{gdb/mi} Interaction
23757 @cindex @sc{gdb/mi}, simple examples
23759 This subsection presents several simple examples of interaction using
23760 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23761 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23762 the output received from @sc{gdb/mi}.
23764 Note the line breaks shown in the examples are here only for
23765 readability, they don't appear in the real output.
23767 @subheading Setting a Breakpoint
23769 Setting a breakpoint generates synchronous output which contains detailed
23770 information of the breakpoint.
23773 -> -break-insert main
23774 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23775 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23776 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23780 @subheading Program Execution
23782 Program execution generates asynchronous records and MI gives the
23783 reason that execution stopped.
23789 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23790 frame=@{addr="0x08048564",func="main",
23791 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23792 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23797 <- *stopped,reason="exited-normally"
23801 @subheading Quitting @value{GDBN}
23803 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23811 Please note that @samp{^exit} is printed immediately, but it might
23812 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23813 performs necessary cleanups, including killing programs being debugged
23814 or disconnecting from debug hardware, so the frontend should wait till
23815 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23816 fails to exit in reasonable time.
23818 @subheading A Bad Command
23820 Here's what happens if you pass a non-existent command:
23824 <- ^error,msg="Undefined MI command: rubbish"
23829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23830 @node GDB/MI Command Description Format
23831 @section @sc{gdb/mi} Command Description Format
23833 The remaining sections describe blocks of commands. Each block of
23834 commands is laid out in a fashion similar to this section.
23836 @subheading Motivation
23838 The motivation for this collection of commands.
23840 @subheading Introduction
23842 A brief introduction to this collection of commands as a whole.
23844 @subheading Commands
23846 For each command in the block, the following is described:
23848 @subsubheading Synopsis
23851 -command @var{args}@dots{}
23854 @subsubheading Result
23856 @subsubheading @value{GDBN} Command
23858 The corresponding @value{GDBN} CLI command(s), if any.
23860 @subsubheading Example
23862 Example(s) formatted for readability. Some of the described commands have
23863 not been implemented yet and these are labeled N.A.@: (not available).
23866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23867 @node GDB/MI Breakpoint Commands
23868 @section @sc{gdb/mi} Breakpoint Commands
23870 @cindex breakpoint commands for @sc{gdb/mi}
23871 @cindex @sc{gdb/mi}, breakpoint commands
23872 This section documents @sc{gdb/mi} commands for manipulating
23875 @subheading The @code{-break-after} Command
23876 @findex -break-after
23878 @subsubheading Synopsis
23881 -break-after @var{number} @var{count}
23884 The breakpoint number @var{number} is not in effect until it has been
23885 hit @var{count} times. To see how this is reflected in the output of
23886 the @samp{-break-list} command, see the description of the
23887 @samp{-break-list} command below.
23889 @subsubheading @value{GDBN} Command
23891 The corresponding @value{GDBN} command is @samp{ignore}.
23893 @subsubheading Example
23898 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23899 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23900 fullname="/home/foo/hello.c",line="5",times="0"@}
23907 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23914 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23915 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23916 line="5",times="0",ignore="3"@}]@}
23921 @subheading The @code{-break-catch} Command
23922 @findex -break-catch
23925 @subheading The @code{-break-commands} Command
23926 @findex -break-commands
23928 @subsubheading Synopsis
23931 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
23934 Specifies the CLI commands that should be executed when breakpoint
23935 @var{number} is hit. The parameters @var{command1} to @var{commandN}
23936 are the commands. If no command is specified, any previously-set
23937 commands are cleared. @xref{Break Commands}. Typical use of this
23938 functionality is tracing a program, that is, printing of values of
23939 some variables whenever breakpoint is hit and then continuing.
23941 @subsubheading @value{GDBN} Command
23943 The corresponding @value{GDBN} command is @samp{commands}.
23945 @subsubheading Example
23950 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23951 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23952 fullname="/home/foo/hello.c",line="5",times="0"@}
23954 -break-commands 1 "print v" "continue"
23959 @subheading The @code{-break-condition} Command
23960 @findex -break-condition
23962 @subsubheading Synopsis
23965 -break-condition @var{number} @var{expr}
23968 Breakpoint @var{number} will stop the program only if the condition in
23969 @var{expr} is true. The condition becomes part of the
23970 @samp{-break-list} output (see the description of the @samp{-break-list}
23973 @subsubheading @value{GDBN} Command
23975 The corresponding @value{GDBN} command is @samp{condition}.
23977 @subsubheading Example
23981 -break-condition 1 1
23985 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23986 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23987 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23988 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23989 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23990 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23991 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23992 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23993 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23994 line="5",cond="1",times="0",ignore="3"@}]@}
23998 @subheading The @code{-break-delete} Command
23999 @findex -break-delete
24001 @subsubheading Synopsis
24004 -break-delete ( @var{breakpoint} )+
24007 Delete the breakpoint(s) whose number(s) are specified in the argument
24008 list. This is obviously reflected in the breakpoint list.
24010 @subsubheading @value{GDBN} Command
24012 The corresponding @value{GDBN} command is @samp{delete}.
24014 @subsubheading Example
24022 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24033 @subheading The @code{-break-disable} Command
24034 @findex -break-disable
24036 @subsubheading Synopsis
24039 -break-disable ( @var{breakpoint} )+
24042 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24043 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24045 @subsubheading @value{GDBN} Command
24047 The corresponding @value{GDBN} command is @samp{disable}.
24049 @subsubheading Example
24057 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24064 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24065 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24066 line="5",times="0"@}]@}
24070 @subheading The @code{-break-enable} Command
24071 @findex -break-enable
24073 @subsubheading Synopsis
24076 -break-enable ( @var{breakpoint} )+
24079 Enable (previously disabled) @var{breakpoint}(s).
24081 @subsubheading @value{GDBN} Command
24083 The corresponding @value{GDBN} command is @samp{enable}.
24085 @subsubheading Example
24093 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24094 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24095 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24096 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24097 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24098 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24099 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24100 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24101 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24102 line="5",times="0"@}]@}
24106 @subheading The @code{-break-info} Command
24107 @findex -break-info
24109 @subsubheading Synopsis
24112 -break-info @var{breakpoint}
24116 Get information about a single breakpoint.
24118 @subsubheading @value{GDBN} Command
24120 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24122 @subsubheading Example
24125 @subheading The @code{-break-insert} Command
24126 @findex -break-insert
24128 @subsubheading Synopsis
24131 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24132 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24133 [ -p @var{thread} ] [ @var{location} ]
24137 If specified, @var{location}, can be one of:
24144 @item filename:linenum
24145 @item filename:function
24149 The possible optional parameters of this command are:
24153 Insert a temporary breakpoint.
24155 Insert a hardware breakpoint.
24156 @item -c @var{condition}
24157 Make the breakpoint conditional on @var{condition}.
24158 @item -i @var{ignore-count}
24159 Initialize the @var{ignore-count}.
24161 If @var{location} cannot be parsed (for example if it
24162 refers to unknown files or functions), create a pending
24163 breakpoint. Without this flag, @value{GDBN} will report
24164 an error, and won't create a breakpoint, if @var{location}
24167 Create a disabled breakpoint.
24169 Create a tracepoint. @xref{Tracepoints}. When this parameter
24170 is used together with @samp{-h}, a fast tracepoint is created.
24173 @subsubheading Result
24175 The result is in the form:
24178 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24179 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24180 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24181 times="@var{times}"@}
24185 where @var{number} is the @value{GDBN} number for this breakpoint,
24186 @var{funcname} is the name of the function where the breakpoint was
24187 inserted, @var{filename} is the name of the source file which contains
24188 this function, @var{lineno} is the source line number within that file
24189 and @var{times} the number of times that the breakpoint has been hit
24190 (always 0 for -break-insert but may be greater for -break-info or -break-list
24191 which use the same output).
24193 Note: this format is open to change.
24194 @c An out-of-band breakpoint instead of part of the result?
24196 @subsubheading @value{GDBN} Command
24198 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24199 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24201 @subsubheading Example
24206 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24207 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24209 -break-insert -t foo
24210 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24211 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24214 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24215 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24216 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24217 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24218 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24219 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24220 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24221 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24222 addr="0x0001072c", func="main",file="recursive2.c",
24223 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24224 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24225 addr="0x00010774",func="foo",file="recursive2.c",
24226 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24228 -break-insert -r foo.*
24229 ~int foo(int, int);
24230 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24231 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24235 @subheading The @code{-break-list} Command
24236 @findex -break-list
24238 @subsubheading Synopsis
24244 Displays the list of inserted breakpoints, showing the following fields:
24248 number of the breakpoint
24250 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24252 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24255 is the breakpoint enabled or no: @samp{y} or @samp{n}
24257 memory location at which the breakpoint is set
24259 logical location of the breakpoint, expressed by function name, file
24262 number of times the breakpoint has been hit
24265 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24266 @code{body} field is an empty list.
24268 @subsubheading @value{GDBN} Command
24270 The corresponding @value{GDBN} command is @samp{info break}.
24272 @subsubheading Example
24277 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24278 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24279 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24280 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24281 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24282 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24283 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24284 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24285 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24286 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24287 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24288 line="13",times="0"@}]@}
24292 Here's an example of the result when there are no breakpoints:
24297 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24298 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24299 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24300 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24301 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24302 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24303 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24308 @subheading The @code{-break-passcount} Command
24309 @findex -break-passcount
24311 @subsubheading Synopsis
24314 -break-passcount @var{tracepoint-number} @var{passcount}
24317 Set the passcount for tracepoint @var{tracepoint-number} to
24318 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24319 is not a tracepoint, error is emitted. This corresponds to CLI
24320 command @samp{passcount}.
24322 @subheading The @code{-break-watch} Command
24323 @findex -break-watch
24325 @subsubheading Synopsis
24328 -break-watch [ -a | -r ]
24331 Create a watchpoint. With the @samp{-a} option it will create an
24332 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24333 read from or on a write to the memory location. With the @samp{-r}
24334 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24335 trigger only when the memory location is accessed for reading. Without
24336 either of the options, the watchpoint created is a regular watchpoint,
24337 i.e., it will trigger when the memory location is accessed for writing.
24338 @xref{Set Watchpoints, , Setting Watchpoints}.
24340 Note that @samp{-break-list} will report a single list of watchpoints and
24341 breakpoints inserted.
24343 @subsubheading @value{GDBN} Command
24345 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24348 @subsubheading Example
24350 Setting a watchpoint on a variable in the @code{main} function:
24355 ^done,wpt=@{number="2",exp="x"@}
24360 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24361 value=@{old="-268439212",new="55"@},
24362 frame=@{func="main",args=[],file="recursive2.c",
24363 fullname="/home/foo/bar/recursive2.c",line="5"@}
24367 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24368 the program execution twice: first for the variable changing value, then
24369 for the watchpoint going out of scope.
24374 ^done,wpt=@{number="5",exp="C"@}
24379 *stopped,reason="watchpoint-trigger",
24380 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24381 frame=@{func="callee4",args=[],
24382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24388 *stopped,reason="watchpoint-scope",wpnum="5",
24389 frame=@{func="callee3",args=[@{name="strarg",
24390 value="0x11940 \"A string argument.\""@}],
24391 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24392 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24396 Listing breakpoints and watchpoints, at different points in the program
24397 execution. Note that once the watchpoint goes out of scope, it is
24403 ^done,wpt=@{number="2",exp="C"@}
24406 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24407 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24408 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24409 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24410 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24411 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24412 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24413 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24414 addr="0x00010734",func="callee4",
24415 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24416 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24417 bkpt=@{number="2",type="watchpoint",disp="keep",
24418 enabled="y",addr="",what="C",times="0"@}]@}
24423 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24424 value=@{old="-276895068",new="3"@},
24425 frame=@{func="callee4",args=[],
24426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24430 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24431 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24432 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24433 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24434 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24435 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24436 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24437 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24438 addr="0x00010734",func="callee4",
24439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24440 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24441 bkpt=@{number="2",type="watchpoint",disp="keep",
24442 enabled="y",addr="",what="C",times="-5"@}]@}
24446 ^done,reason="watchpoint-scope",wpnum="2",
24447 frame=@{func="callee3",args=[@{name="strarg",
24448 value="0x11940 \"A string argument.\""@}],
24449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24450 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24453 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24454 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24455 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24456 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24457 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24458 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24459 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24460 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24461 addr="0x00010734",func="callee4",
24462 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24463 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24469 @node GDB/MI Program Context
24470 @section @sc{gdb/mi} Program Context
24472 @subheading The @code{-exec-arguments} Command
24473 @findex -exec-arguments
24476 @subsubheading Synopsis
24479 -exec-arguments @var{args}
24482 Set the inferior program arguments, to be used in the next
24485 @subsubheading @value{GDBN} Command
24487 The corresponding @value{GDBN} command is @samp{set args}.
24489 @subsubheading Example
24493 -exec-arguments -v word
24500 @subheading The @code{-exec-show-arguments} Command
24501 @findex -exec-show-arguments
24503 @subsubheading Synopsis
24506 -exec-show-arguments
24509 Print the arguments of the program.
24511 @subsubheading @value{GDBN} Command
24513 The corresponding @value{GDBN} command is @samp{show args}.
24515 @subsubheading Example
24520 @subheading The @code{-environment-cd} Command
24521 @findex -environment-cd
24523 @subsubheading Synopsis
24526 -environment-cd @var{pathdir}
24529 Set @value{GDBN}'s working directory.
24531 @subsubheading @value{GDBN} Command
24533 The corresponding @value{GDBN} command is @samp{cd}.
24535 @subsubheading Example
24539 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24545 @subheading The @code{-environment-directory} Command
24546 @findex -environment-directory
24548 @subsubheading Synopsis
24551 -environment-directory [ -r ] [ @var{pathdir} ]+
24554 Add directories @var{pathdir} to beginning of search path for source files.
24555 If the @samp{-r} option is used, the search path is reset to the default
24556 search path. If directories @var{pathdir} are supplied in addition to the
24557 @samp{-r} option, the search path is first reset and then addition
24559 Multiple directories may be specified, separated by blanks. Specifying
24560 multiple directories in a single command
24561 results in the directories added to the beginning of the
24562 search path in the same order they were presented in the command.
24563 If blanks are needed as
24564 part of a directory name, double-quotes should be used around
24565 the name. In the command output, the path will show up separated
24566 by the system directory-separator character. The directory-separator
24567 character must not be used
24568 in any directory name.
24569 If no directories are specified, the current search path is displayed.
24571 @subsubheading @value{GDBN} Command
24573 The corresponding @value{GDBN} command is @samp{dir}.
24575 @subsubheading Example
24579 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24580 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24582 -environment-directory ""
24583 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24585 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24586 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24588 -environment-directory -r
24589 ^done,source-path="$cdir:$cwd"
24594 @subheading The @code{-environment-path} Command
24595 @findex -environment-path
24597 @subsubheading Synopsis
24600 -environment-path [ -r ] [ @var{pathdir} ]+
24603 Add directories @var{pathdir} to beginning of search path for object files.
24604 If the @samp{-r} option is used, the search path is reset to the original
24605 search path that existed at gdb start-up. If directories @var{pathdir} are
24606 supplied in addition to the
24607 @samp{-r} option, the search path is first reset and then addition
24609 Multiple directories may be specified, separated by blanks. Specifying
24610 multiple directories in a single command
24611 results in the directories added to the beginning of the
24612 search path in the same order they were presented in the command.
24613 If blanks are needed as
24614 part of a directory name, double-quotes should be used around
24615 the name. In the command output, the path will show up separated
24616 by the system directory-separator character. The directory-separator
24617 character must not be used
24618 in any directory name.
24619 If no directories are specified, the current path is displayed.
24622 @subsubheading @value{GDBN} Command
24624 The corresponding @value{GDBN} command is @samp{path}.
24626 @subsubheading Example
24631 ^done,path="/usr/bin"
24633 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24634 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24636 -environment-path -r /usr/local/bin
24637 ^done,path="/usr/local/bin:/usr/bin"
24642 @subheading The @code{-environment-pwd} Command
24643 @findex -environment-pwd
24645 @subsubheading Synopsis
24651 Show the current working directory.
24653 @subsubheading @value{GDBN} Command
24655 The corresponding @value{GDBN} command is @samp{pwd}.
24657 @subsubheading Example
24662 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24666 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24667 @node GDB/MI Thread Commands
24668 @section @sc{gdb/mi} Thread Commands
24671 @subheading The @code{-thread-info} Command
24672 @findex -thread-info
24674 @subsubheading Synopsis
24677 -thread-info [ @var{thread-id} ]
24680 Reports information about either a specific thread, if
24681 the @var{thread-id} parameter is present, or about all
24682 threads. When printing information about all threads,
24683 also reports the current thread.
24685 @subsubheading @value{GDBN} Command
24687 The @samp{info thread} command prints the same information
24690 @subsubheading Example
24695 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24696 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24697 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24698 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24699 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24700 current-thread-id="1"
24704 The @samp{state} field may have the following values:
24708 The thread is stopped. Frame information is available for stopped
24712 The thread is running. There's no frame information for running
24717 @subheading The @code{-thread-list-ids} Command
24718 @findex -thread-list-ids
24720 @subsubheading Synopsis
24726 Produces a list of the currently known @value{GDBN} thread ids. At the
24727 end of the list it also prints the total number of such threads.
24729 This command is retained for historical reasons, the
24730 @code{-thread-info} command should be used instead.
24732 @subsubheading @value{GDBN} Command
24734 Part of @samp{info threads} supplies the same information.
24736 @subsubheading Example
24741 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24742 current-thread-id="1",number-of-threads="3"
24747 @subheading The @code{-thread-select} Command
24748 @findex -thread-select
24750 @subsubheading Synopsis
24753 -thread-select @var{threadnum}
24756 Make @var{threadnum} the current thread. It prints the number of the new
24757 current thread, and the topmost frame for that thread.
24759 This command is deprecated in favor of explicitly using the
24760 @samp{--thread} option to each command.
24762 @subsubheading @value{GDBN} Command
24764 The corresponding @value{GDBN} command is @samp{thread}.
24766 @subsubheading Example
24773 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24774 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24778 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24779 number-of-threads="3"
24782 ^done,new-thread-id="3",
24783 frame=@{level="0",func="vprintf",
24784 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24785 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24789 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24790 @node GDB/MI Program Execution
24791 @section @sc{gdb/mi} Program Execution
24793 These are the asynchronous commands which generate the out-of-band
24794 record @samp{*stopped}. Currently @value{GDBN} only really executes
24795 asynchronously with remote targets and this interaction is mimicked in
24798 @subheading The @code{-exec-continue} Command
24799 @findex -exec-continue
24801 @subsubheading Synopsis
24804 -exec-continue [--reverse] [--all|--thread-group N]
24807 Resumes the execution of the inferior program, which will continue
24808 to execute until it reaches a debugger stop event. If the
24809 @samp{--reverse} option is specified, execution resumes in reverse until
24810 it reaches a stop event. Stop events may include
24813 breakpoints or watchpoints
24815 signals or exceptions
24817 the end of the process (or its beginning under @samp{--reverse})
24819 the end or beginning of a replay log if one is being used.
24821 In all-stop mode (@pxref{All-Stop
24822 Mode}), may resume only one thread, or all threads, depending on the
24823 value of the @samp{scheduler-locking} variable. If @samp{--all} is
24824 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
24825 ignored in all-stop mode. If the @samp{--thread-group} options is
24826 specified, then all threads in that thread group are resumed.
24828 @subsubheading @value{GDBN} Command
24830 The corresponding @value{GDBN} corresponding is @samp{continue}.
24832 @subsubheading Example
24839 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
24840 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
24846 @subheading The @code{-exec-finish} Command
24847 @findex -exec-finish
24849 @subsubheading Synopsis
24852 -exec-finish [--reverse]
24855 Resumes the execution of the inferior program until the current
24856 function is exited. Displays the results returned by the function.
24857 If the @samp{--reverse} option is specified, resumes the reverse
24858 execution of the inferior program until the point where current
24859 function was called.
24861 @subsubheading @value{GDBN} Command
24863 The corresponding @value{GDBN} command is @samp{finish}.
24865 @subsubheading Example
24867 Function returning @code{void}.
24874 *stopped,reason="function-finished",frame=@{func="main",args=[],
24875 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
24879 Function returning other than @code{void}. The name of the internal
24880 @value{GDBN} variable storing the result is printed, together with the
24887 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
24888 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
24889 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24890 gdb-result-var="$1",return-value="0"
24895 @subheading The @code{-exec-interrupt} Command
24896 @findex -exec-interrupt
24898 @subsubheading Synopsis
24901 -exec-interrupt [--all|--thread-group N]
24904 Interrupts the background execution of the target. Note how the token
24905 associated with the stop message is the one for the execution command
24906 that has been interrupted. The token for the interrupt itself only
24907 appears in the @samp{^done} output. If the user is trying to
24908 interrupt a non-running program, an error message will be printed.
24910 Note that when asynchronous execution is enabled, this command is
24911 asynchronous just like other execution commands. That is, first the
24912 @samp{^done} response will be printed, and the target stop will be
24913 reported after that using the @samp{*stopped} notification.
24915 In non-stop mode, only the context thread is interrupted by default.
24916 All threads (in all inferiors) will be interrupted if the
24917 @samp{--all} option is specified. If the @samp{--thread-group}
24918 option is specified, all threads in that group will be interrupted.
24920 @subsubheading @value{GDBN} Command
24922 The corresponding @value{GDBN} command is @samp{interrupt}.
24924 @subsubheading Example
24935 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
24936 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
24937 fullname="/home/foo/bar/try.c",line="13"@}
24942 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24946 @subheading The @code{-exec-jump} Command
24949 @subsubheading Synopsis
24952 -exec-jump @var{location}
24955 Resumes execution of the inferior program at the location specified by
24956 parameter. @xref{Specify Location}, for a description of the
24957 different forms of @var{location}.
24959 @subsubheading @value{GDBN} Command
24961 The corresponding @value{GDBN} command is @samp{jump}.
24963 @subsubheading Example
24966 -exec-jump foo.c:10
24967 *running,thread-id="all"
24972 @subheading The @code{-exec-next} Command
24975 @subsubheading Synopsis
24978 -exec-next [--reverse]
24981 Resumes execution of the inferior program, stopping when the beginning
24982 of the next source line is reached.
24984 If the @samp{--reverse} option is specified, resumes reverse execution
24985 of the inferior program, stopping at the beginning of the previous
24986 source line. If you issue this command on the first line of a
24987 function, it will take you back to the caller of that function, to the
24988 source line where the function was called.
24991 @subsubheading @value{GDBN} Command
24993 The corresponding @value{GDBN} command is @samp{next}.
24995 @subsubheading Example
25001 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25006 @subheading The @code{-exec-next-instruction} Command
25007 @findex -exec-next-instruction
25009 @subsubheading Synopsis
25012 -exec-next-instruction [--reverse]
25015 Executes one machine instruction. If the instruction is a function
25016 call, continues until the function returns. If the program stops at an
25017 instruction in the middle of a source line, the address will be
25020 If the @samp{--reverse} option is specified, resumes reverse execution
25021 of the inferior program, stopping at the previous instruction. If the
25022 previously executed instruction was a return from another function,
25023 it will continue to execute in reverse until the call to that function
25024 (from the current stack frame) is reached.
25026 @subsubheading @value{GDBN} Command
25028 The corresponding @value{GDBN} command is @samp{nexti}.
25030 @subsubheading Example
25034 -exec-next-instruction
25038 *stopped,reason="end-stepping-range",
25039 addr="0x000100d4",line="5",file="hello.c"
25044 @subheading The @code{-exec-return} Command
25045 @findex -exec-return
25047 @subsubheading Synopsis
25053 Makes current function return immediately. Doesn't execute the inferior.
25054 Displays the new current frame.
25056 @subsubheading @value{GDBN} Command
25058 The corresponding @value{GDBN} command is @samp{return}.
25060 @subsubheading Example
25064 200-break-insert callee4
25065 200^done,bkpt=@{number="1",addr="0x00010734",
25066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25071 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25072 frame=@{func="callee4",args=[],
25073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25074 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25080 111^done,frame=@{level="0",func="callee3",
25081 args=[@{name="strarg",
25082 value="0x11940 \"A string argument.\""@}],
25083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25084 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25089 @subheading The @code{-exec-run} Command
25092 @subsubheading Synopsis
25095 -exec-run [--all | --thread-group N]
25098 Starts execution of the inferior from the beginning. The inferior
25099 executes until either a breakpoint is encountered or the program
25100 exits. In the latter case the output will include an exit code, if
25101 the program has exited exceptionally.
25103 When no option is specified, the current inferior is started. If the
25104 @samp{--thread-group} option is specified, it should refer to a thread
25105 group of type @samp{process}, and that thread group will be started.
25106 If the @samp{--all} option is specified, then all inferiors will be started.
25108 @subsubheading @value{GDBN} Command
25110 The corresponding @value{GDBN} command is @samp{run}.
25112 @subsubheading Examples
25117 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25122 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25123 frame=@{func="main",args=[],file="recursive2.c",
25124 fullname="/home/foo/bar/recursive2.c",line="4"@}
25129 Program exited normally:
25137 *stopped,reason="exited-normally"
25142 Program exited exceptionally:
25150 *stopped,reason="exited",exit-code="01"
25154 Another way the program can terminate is if it receives a signal such as
25155 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25159 *stopped,reason="exited-signalled",signal-name="SIGINT",
25160 signal-meaning="Interrupt"
25164 @c @subheading -exec-signal
25167 @subheading The @code{-exec-step} Command
25170 @subsubheading Synopsis
25173 -exec-step [--reverse]
25176 Resumes execution of the inferior program, stopping when the beginning
25177 of the next source line is reached, if the next source line is not a
25178 function call. If it is, stop at the first instruction of the called
25179 function. If the @samp{--reverse} option is specified, resumes reverse
25180 execution of the inferior program, stopping at the beginning of the
25181 previously executed source line.
25183 @subsubheading @value{GDBN} Command
25185 The corresponding @value{GDBN} command is @samp{step}.
25187 @subsubheading Example
25189 Stepping into a function:
25195 *stopped,reason="end-stepping-range",
25196 frame=@{func="foo",args=[@{name="a",value="10"@},
25197 @{name="b",value="0"@}],file="recursive2.c",
25198 fullname="/home/foo/bar/recursive2.c",line="11"@}
25208 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25213 @subheading The @code{-exec-step-instruction} Command
25214 @findex -exec-step-instruction
25216 @subsubheading Synopsis
25219 -exec-step-instruction [--reverse]
25222 Resumes the inferior which executes one machine instruction. If the
25223 @samp{--reverse} option is specified, resumes reverse execution of the
25224 inferior program, stopping at the previously executed instruction.
25225 The output, once @value{GDBN} has stopped, will vary depending on
25226 whether we have stopped in the middle of a source line or not. In the
25227 former case, the address at which the program stopped will be printed
25230 @subsubheading @value{GDBN} Command
25232 The corresponding @value{GDBN} command is @samp{stepi}.
25234 @subsubheading Example
25238 -exec-step-instruction
25242 *stopped,reason="end-stepping-range",
25243 frame=@{func="foo",args=[],file="try.c",
25244 fullname="/home/foo/bar/try.c",line="10"@}
25246 -exec-step-instruction
25250 *stopped,reason="end-stepping-range",
25251 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25252 fullname="/home/foo/bar/try.c",line="10"@}
25257 @subheading The @code{-exec-until} Command
25258 @findex -exec-until
25260 @subsubheading Synopsis
25263 -exec-until [ @var{location} ]
25266 Executes the inferior until the @var{location} specified in the
25267 argument is reached. If there is no argument, the inferior executes
25268 until a source line greater than the current one is reached. The
25269 reason for stopping in this case will be @samp{location-reached}.
25271 @subsubheading @value{GDBN} Command
25273 The corresponding @value{GDBN} command is @samp{until}.
25275 @subsubheading Example
25279 -exec-until recursive2.c:6
25283 *stopped,reason="location-reached",frame=@{func="main",args=[],
25284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25289 @subheading -file-clear
25290 Is this going away????
25293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25294 @node GDB/MI Stack Manipulation
25295 @section @sc{gdb/mi} Stack Manipulation Commands
25298 @subheading The @code{-stack-info-frame} Command
25299 @findex -stack-info-frame
25301 @subsubheading Synopsis
25307 Get info on the selected frame.
25309 @subsubheading @value{GDBN} Command
25311 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25312 (without arguments).
25314 @subsubheading Example
25319 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25320 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25321 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25325 @subheading The @code{-stack-info-depth} Command
25326 @findex -stack-info-depth
25328 @subsubheading Synopsis
25331 -stack-info-depth [ @var{max-depth} ]
25334 Return the depth of the stack. If the integer argument @var{max-depth}
25335 is specified, do not count beyond @var{max-depth} frames.
25337 @subsubheading @value{GDBN} Command
25339 There's no equivalent @value{GDBN} command.
25341 @subsubheading Example
25343 For a stack with frame levels 0 through 11:
25350 -stack-info-depth 4
25353 -stack-info-depth 12
25356 -stack-info-depth 11
25359 -stack-info-depth 13
25364 @subheading The @code{-stack-list-arguments} Command
25365 @findex -stack-list-arguments
25367 @subsubheading Synopsis
25370 -stack-list-arguments @var{print-values}
25371 [ @var{low-frame} @var{high-frame} ]
25374 Display a list of the arguments for the frames between @var{low-frame}
25375 and @var{high-frame} (inclusive). If @var{low-frame} and
25376 @var{high-frame} are not provided, list the arguments for the whole
25377 call stack. If the two arguments are equal, show the single frame
25378 at the corresponding level. It is an error if @var{low-frame} is
25379 larger than the actual number of frames. On the other hand,
25380 @var{high-frame} may be larger than the actual number of frames, in
25381 which case only existing frames will be returned.
25383 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25384 the variables; if it is 1 or @code{--all-values}, print also their
25385 values; and if it is 2 or @code{--simple-values}, print the name,
25386 type and value for simple data types, and the name and type for arrays,
25387 structures and unions.
25389 Use of this command to obtain arguments in a single frame is
25390 deprecated in favor of the @samp{-stack-list-variables} command.
25392 @subsubheading @value{GDBN} Command
25394 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25395 @samp{gdb_get_args} command which partially overlaps with the
25396 functionality of @samp{-stack-list-arguments}.
25398 @subsubheading Example
25405 frame=@{level="0",addr="0x00010734",func="callee4",
25406 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25407 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25408 frame=@{level="1",addr="0x0001076c",func="callee3",
25409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25411 frame=@{level="2",addr="0x0001078c",func="callee2",
25412 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25413 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25414 frame=@{level="3",addr="0x000107b4",func="callee1",
25415 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25416 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25417 frame=@{level="4",addr="0x000107e0",func="main",
25418 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25419 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25421 -stack-list-arguments 0
25424 frame=@{level="0",args=[]@},
25425 frame=@{level="1",args=[name="strarg"]@},
25426 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25427 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25428 frame=@{level="4",args=[]@}]
25430 -stack-list-arguments 1
25433 frame=@{level="0",args=[]@},
25435 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25436 frame=@{level="2",args=[
25437 @{name="intarg",value="2"@},
25438 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25439 @{frame=@{level="3",args=[
25440 @{name="intarg",value="2"@},
25441 @{name="strarg",value="0x11940 \"A string argument.\""@},
25442 @{name="fltarg",value="3.5"@}]@},
25443 frame=@{level="4",args=[]@}]
25445 -stack-list-arguments 0 2 2
25446 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25448 -stack-list-arguments 1 2 2
25449 ^done,stack-args=[frame=@{level="2",
25450 args=[@{name="intarg",value="2"@},
25451 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25455 @c @subheading -stack-list-exception-handlers
25458 @subheading The @code{-stack-list-frames} Command
25459 @findex -stack-list-frames
25461 @subsubheading Synopsis
25464 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25467 List the frames currently on the stack. For each frame it displays the
25472 The frame number, 0 being the topmost frame, i.e., the innermost function.
25474 The @code{$pc} value for that frame.
25478 File name of the source file where the function lives.
25480 Line number corresponding to the @code{$pc}.
25483 If invoked without arguments, this command prints a backtrace for the
25484 whole stack. If given two integer arguments, it shows the frames whose
25485 levels are between the two arguments (inclusive). If the two arguments
25486 are equal, it shows the single frame at the corresponding level. It is
25487 an error if @var{low-frame} is larger than the actual number of
25488 frames. On the other hand, @var{high-frame} may be larger than the
25489 actual number of frames, in which case only existing frames will be returned.
25491 @subsubheading @value{GDBN} Command
25493 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25495 @subsubheading Example
25497 Full stack backtrace:
25503 [frame=@{level="0",addr="0x0001076c",func="foo",
25504 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25505 frame=@{level="1",addr="0x000107a4",func="foo",
25506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25507 frame=@{level="2",addr="0x000107a4",func="foo",
25508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25509 frame=@{level="3",addr="0x000107a4",func="foo",
25510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25511 frame=@{level="4",addr="0x000107a4",func="foo",
25512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25513 frame=@{level="5",addr="0x000107a4",func="foo",
25514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25515 frame=@{level="6",addr="0x000107a4",func="foo",
25516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25517 frame=@{level="7",addr="0x000107a4",func="foo",
25518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25519 frame=@{level="8",addr="0x000107a4",func="foo",
25520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25521 frame=@{level="9",addr="0x000107a4",func="foo",
25522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25523 frame=@{level="10",addr="0x000107a4",func="foo",
25524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25525 frame=@{level="11",addr="0x00010738",func="main",
25526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25530 Show frames between @var{low_frame} and @var{high_frame}:
25534 -stack-list-frames 3 5
25536 [frame=@{level="3",addr="0x000107a4",func="foo",
25537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25538 frame=@{level="4",addr="0x000107a4",func="foo",
25539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25540 frame=@{level="5",addr="0x000107a4",func="foo",
25541 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25545 Show a single frame:
25549 -stack-list-frames 3 3
25551 [frame=@{level="3",addr="0x000107a4",func="foo",
25552 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25557 @subheading The @code{-stack-list-locals} Command
25558 @findex -stack-list-locals
25560 @subsubheading Synopsis
25563 -stack-list-locals @var{print-values}
25566 Display the local variable names for the selected frame. If
25567 @var{print-values} is 0 or @code{--no-values}, print only the names of
25568 the variables; if it is 1 or @code{--all-values}, print also their
25569 values; and if it is 2 or @code{--simple-values}, print the name,
25570 type and value for simple data types, and the name and type for arrays,
25571 structures and unions. In this last case, a frontend can immediately
25572 display the value of simple data types and create variable objects for
25573 other data types when the user wishes to explore their values in
25576 This command is deprecated in favor of the
25577 @samp{-stack-list-variables} command.
25579 @subsubheading @value{GDBN} Command
25581 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25583 @subsubheading Example
25587 -stack-list-locals 0
25588 ^done,locals=[name="A",name="B",name="C"]
25590 -stack-list-locals --all-values
25591 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25592 @{name="C",value="@{1, 2, 3@}"@}]
25593 -stack-list-locals --simple-values
25594 ^done,locals=[@{name="A",type="int",value="1"@},
25595 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25599 @subheading The @code{-stack-list-variables} Command
25600 @findex -stack-list-variables
25602 @subsubheading Synopsis
25605 -stack-list-variables @var{print-values}
25608 Display the names of local variables and function arguments for the selected frame. If
25609 @var{print-values} is 0 or @code{--no-values}, print only the names of
25610 the variables; if it is 1 or @code{--all-values}, print also their
25611 values; and if it is 2 or @code{--simple-values}, print the name,
25612 type and value for simple data types, and the name and type for arrays,
25613 structures and unions.
25615 @subsubheading Example
25619 -stack-list-variables --thread 1 --frame 0 --all-values
25620 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25625 @subheading The @code{-stack-select-frame} Command
25626 @findex -stack-select-frame
25628 @subsubheading Synopsis
25631 -stack-select-frame @var{framenum}
25634 Change the selected frame. Select a different frame @var{framenum} on
25637 This command in deprecated in favor of passing the @samp{--frame}
25638 option to every command.
25640 @subsubheading @value{GDBN} Command
25642 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25643 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
25645 @subsubheading Example
25649 -stack-select-frame 2
25654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25655 @node GDB/MI Variable Objects
25656 @section @sc{gdb/mi} Variable Objects
25660 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25662 For the implementation of a variable debugger window (locals, watched
25663 expressions, etc.), we are proposing the adaptation of the existing code
25664 used by @code{Insight}.
25666 The two main reasons for that are:
25670 It has been proven in practice (it is already on its second generation).
25673 It will shorten development time (needless to say how important it is
25677 The original interface was designed to be used by Tcl code, so it was
25678 slightly changed so it could be used through @sc{gdb/mi}. This section
25679 describes the @sc{gdb/mi} operations that will be available and gives some
25680 hints about their use.
25682 @emph{Note}: In addition to the set of operations described here, we
25683 expect the @sc{gui} implementation of a variable window to require, at
25684 least, the following operations:
25687 @item @code{-gdb-show} @code{output-radix}
25688 @item @code{-stack-list-arguments}
25689 @item @code{-stack-list-locals}
25690 @item @code{-stack-select-frame}
25695 @subheading Introduction to Variable Objects
25697 @cindex variable objects in @sc{gdb/mi}
25699 Variable objects are "object-oriented" MI interface for examining and
25700 changing values of expressions. Unlike some other MI interfaces that
25701 work with expressions, variable objects are specifically designed for
25702 simple and efficient presentation in the frontend. A variable object
25703 is identified by string name. When a variable object is created, the
25704 frontend specifies the expression for that variable object. The
25705 expression can be a simple variable, or it can be an arbitrary complex
25706 expression, and can even involve CPU registers. After creating a
25707 variable object, the frontend can invoke other variable object
25708 operations---for example to obtain or change the value of a variable
25709 object, or to change display format.
25711 Variable objects have hierarchical tree structure. Any variable object
25712 that corresponds to a composite type, such as structure in C, has
25713 a number of child variable objects, for example corresponding to each
25714 element of a structure. A child variable object can itself have
25715 children, recursively. Recursion ends when we reach
25716 leaf variable objects, which always have built-in types. Child variable
25717 objects are created only by explicit request, so if a frontend
25718 is not interested in the children of a particular variable object, no
25719 child will be created.
25721 For a leaf variable object it is possible to obtain its value as a
25722 string, or set the value from a string. String value can be also
25723 obtained for a non-leaf variable object, but it's generally a string
25724 that only indicates the type of the object, and does not list its
25725 contents. Assignment to a non-leaf variable object is not allowed.
25727 A frontend does not need to read the values of all variable objects each time
25728 the program stops. Instead, MI provides an update command that lists all
25729 variable objects whose values has changed since the last update
25730 operation. This considerably reduces the amount of data that must
25731 be transferred to the frontend. As noted above, children variable
25732 objects are created on demand, and only leaf variable objects have a
25733 real value. As result, gdb will read target memory only for leaf
25734 variables that frontend has created.
25736 The automatic update is not always desirable. For example, a frontend
25737 might want to keep a value of some expression for future reference,
25738 and never update it. For another example, fetching memory is
25739 relatively slow for embedded targets, so a frontend might want
25740 to disable automatic update for the variables that are either not
25741 visible on the screen, or ``closed''. This is possible using so
25742 called ``frozen variable objects''. Such variable objects are never
25743 implicitly updated.
25745 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25746 fixed variable object, the expression is parsed when the variable
25747 object is created, including associating identifiers to specific
25748 variables. The meaning of expression never changes. For a floating
25749 variable object the values of variables whose names appear in the
25750 expressions are re-evaluated every time in the context of the current
25751 frame. Consider this example:
25756 struct work_state state;
25763 If a fixed variable object for the @code{state} variable is created in
25764 this function, and we enter the recursive call, the the variable
25765 object will report the value of @code{state} in the top-level
25766 @code{do_work} invocation. On the other hand, a floating variable
25767 object will report the value of @code{state} in the current frame.
25769 If an expression specified when creating a fixed variable object
25770 refers to a local variable, the variable object becomes bound to the
25771 thread and frame in which the variable object is created. When such
25772 variable object is updated, @value{GDBN} makes sure that the
25773 thread/frame combination the variable object is bound to still exists,
25774 and re-evaluates the variable object in context of that thread/frame.
25776 The following is the complete set of @sc{gdb/mi} operations defined to
25777 access this functionality:
25779 @multitable @columnfractions .4 .6
25780 @item @strong{Operation}
25781 @tab @strong{Description}
25783 @item @code{-enable-pretty-printing}
25784 @tab enable Python-based pretty-printing
25785 @item @code{-var-create}
25786 @tab create a variable object
25787 @item @code{-var-delete}
25788 @tab delete the variable object and/or its children
25789 @item @code{-var-set-format}
25790 @tab set the display format of this variable
25791 @item @code{-var-show-format}
25792 @tab show the display format of this variable
25793 @item @code{-var-info-num-children}
25794 @tab tells how many children this object has
25795 @item @code{-var-list-children}
25796 @tab return a list of the object's children
25797 @item @code{-var-info-type}
25798 @tab show the type of this variable object
25799 @item @code{-var-info-expression}
25800 @tab print parent-relative expression that this variable object represents
25801 @item @code{-var-info-path-expression}
25802 @tab print full expression that this variable object represents
25803 @item @code{-var-show-attributes}
25804 @tab is this variable editable? does it exist here?
25805 @item @code{-var-evaluate-expression}
25806 @tab get the value of this variable
25807 @item @code{-var-assign}
25808 @tab set the value of this variable
25809 @item @code{-var-update}
25810 @tab update the variable and its children
25811 @item @code{-var-set-frozen}
25812 @tab set frozeness attribute
25813 @item @code{-var-set-update-range}
25814 @tab set range of children to display on update
25817 In the next subsection we describe each operation in detail and suggest
25818 how it can be used.
25820 @subheading Description And Use of Operations on Variable Objects
25822 @subheading The @code{-enable-pretty-printing} Command
25823 @findex -enable-pretty-printing
25826 -enable-pretty-printing
25829 @value{GDBN} allows Python-based visualizers to affect the output of the
25830 MI variable object commands. However, because there was no way to
25831 implement this in a fully backward-compatible way, a front end must
25832 request that this functionality be enabled.
25834 Once enabled, this feature cannot be disabled.
25836 Note that if Python support has not been compiled into @value{GDBN},
25837 this command will still succeed (and do nothing).
25839 This feature is currently (as of @value{GDBN} 7.0) experimental, and
25840 may work differently in future versions of @value{GDBN}.
25842 @subheading The @code{-var-create} Command
25843 @findex -var-create
25845 @subsubheading Synopsis
25848 -var-create @{@var{name} | "-"@}
25849 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
25852 This operation creates a variable object, which allows the monitoring of
25853 a variable, the result of an expression, a memory cell or a CPU
25856 The @var{name} parameter is the string by which the object can be
25857 referenced. It must be unique. If @samp{-} is specified, the varobj
25858 system will generate a string ``varNNNNNN'' automatically. It will be
25859 unique provided that one does not specify @var{name} of that format.
25860 The command fails if a duplicate name is found.
25862 The frame under which the expression should be evaluated can be
25863 specified by @var{frame-addr}. A @samp{*} indicates that the current
25864 frame should be used. A @samp{@@} indicates that a floating variable
25865 object must be created.
25867 @var{expression} is any expression valid on the current language set (must not
25868 begin with a @samp{*}), or one of the following:
25872 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
25875 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
25878 @samp{$@var{regname}} --- a CPU register name
25881 @cindex dynamic varobj
25882 A varobj's contents may be provided by a Python-based pretty-printer. In this
25883 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
25884 have slightly different semantics in some cases. If the
25885 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
25886 will never create a dynamic varobj. This ensures backward
25887 compatibility for existing clients.
25889 @subsubheading Result
25891 This operation returns attributes of the newly-created varobj. These
25896 The name of the varobj.
25899 The number of children of the varobj. This number is not necessarily
25900 reliable for a dynamic varobj. Instead, you must examine the
25901 @samp{has_more} attribute.
25904 The varobj's scalar value. For a varobj whose type is some sort of
25905 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
25906 will not be interesting.
25909 The varobj's type. This is a string representation of the type, as
25910 would be printed by the @value{GDBN} CLI.
25913 If a variable object is bound to a specific thread, then this is the
25914 thread's identifier.
25917 For a dynamic varobj, this indicates whether there appear to be any
25918 children available. For a non-dynamic varobj, this will be 0.
25921 This attribute will be present and have the value @samp{1} if the
25922 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25923 then this attribute will not be present.
25926 A dynamic varobj can supply a display hint to the front end. The
25927 value comes directly from the Python pretty-printer object's
25928 @code{display_hint} method. @xref{Pretty Printing API}.
25931 Typical output will look like this:
25934 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
25935 has_more="@var{has_more}"
25939 @subheading The @code{-var-delete} Command
25940 @findex -var-delete
25942 @subsubheading Synopsis
25945 -var-delete [ -c ] @var{name}
25948 Deletes a previously created variable object and all of its children.
25949 With the @samp{-c} option, just deletes the children.
25951 Returns an error if the object @var{name} is not found.
25954 @subheading The @code{-var-set-format} Command
25955 @findex -var-set-format
25957 @subsubheading Synopsis
25960 -var-set-format @var{name} @var{format-spec}
25963 Sets the output format for the value of the object @var{name} to be
25966 @anchor{-var-set-format}
25967 The syntax for the @var{format-spec} is as follows:
25970 @var{format-spec} @expansion{}
25971 @{binary | decimal | hexadecimal | octal | natural@}
25974 The natural format is the default format choosen automatically
25975 based on the variable type (like decimal for an @code{int}, hex
25976 for pointers, etc.).
25978 For a variable with children, the format is set only on the
25979 variable itself, and the children are not affected.
25981 @subheading The @code{-var-show-format} Command
25982 @findex -var-show-format
25984 @subsubheading Synopsis
25987 -var-show-format @var{name}
25990 Returns the format used to display the value of the object @var{name}.
25993 @var{format} @expansion{}
25998 @subheading The @code{-var-info-num-children} Command
25999 @findex -var-info-num-children
26001 @subsubheading Synopsis
26004 -var-info-num-children @var{name}
26007 Returns the number of children of a variable object @var{name}:
26013 Note that this number is not completely reliable for a dynamic varobj.
26014 It will return the current number of children, but more children may
26018 @subheading The @code{-var-list-children} Command
26019 @findex -var-list-children
26021 @subsubheading Synopsis
26024 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26026 @anchor{-var-list-children}
26028 Return a list of the children of the specified variable object and
26029 create variable objects for them, if they do not already exist. With
26030 a single argument or if @var{print-values} has a value for of 0 or
26031 @code{--no-values}, print only the names of the variables; if
26032 @var{print-values} is 1 or @code{--all-values}, also print their
26033 values; and if it is 2 or @code{--simple-values} print the name and
26034 value for simple data types and just the name for arrays, structures
26037 @var{from} and @var{to}, if specified, indicate the range of children
26038 to report. If @var{from} or @var{to} is less than zero, the range is
26039 reset and all children will be reported. Otherwise, children starting
26040 at @var{from} (zero-based) and up to and excluding @var{to} will be
26043 If a child range is requested, it will only affect the current call to
26044 @code{-var-list-children}, but not future calls to @code{-var-update}.
26045 For this, you must instead use @code{-var-set-update-range}. The
26046 intent of this approach is to enable a front end to implement any
26047 update approach it likes; for example, scrolling a view may cause the
26048 front end to request more children with @code{-var-list-children}, and
26049 then the front end could call @code{-var-set-update-range} with a
26050 different range to ensure that future updates are restricted to just
26053 For each child the following results are returned:
26058 Name of the variable object created for this child.
26061 The expression to be shown to the user by the front end to designate this child.
26062 For example this may be the name of a structure member.
26064 For a dynamic varobj, this value cannot be used to form an
26065 expression. There is no way to do this at all with a dynamic varobj.
26067 For C/C@t{++} structures there are several pseudo children returned to
26068 designate access qualifiers. For these pseudo children @var{exp} is
26069 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26070 type and value are not present.
26072 A dynamic varobj will not report the access qualifying
26073 pseudo-children, regardless of the language. This information is not
26074 available at all with a dynamic varobj.
26077 Number of children this child has. For a dynamic varobj, this will be
26081 The type of the child.
26084 If values were requested, this is the value.
26087 If this variable object is associated with a thread, this is the thread id.
26088 Otherwise this result is not present.
26091 If the variable object is frozen, this variable will be present with a value of 1.
26094 The result may have its own attributes:
26098 A dynamic varobj can supply a display hint to the front end. The
26099 value comes directly from the Python pretty-printer object's
26100 @code{display_hint} method. @xref{Pretty Printing API}.
26103 This is an integer attribute which is nonzero if there are children
26104 remaining after the end of the selected range.
26107 @subsubheading Example
26111 -var-list-children n
26112 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26113 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26115 -var-list-children --all-values n
26116 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26117 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26121 @subheading The @code{-var-info-type} Command
26122 @findex -var-info-type
26124 @subsubheading Synopsis
26127 -var-info-type @var{name}
26130 Returns the type of the specified variable @var{name}. The type is
26131 returned as a string in the same format as it is output by the
26135 type=@var{typename}
26139 @subheading The @code{-var-info-expression} Command
26140 @findex -var-info-expression
26142 @subsubheading Synopsis
26145 -var-info-expression @var{name}
26148 Returns a string that is suitable for presenting this
26149 variable object in user interface. The string is generally
26150 not valid expression in the current language, and cannot be evaluated.
26152 For example, if @code{a} is an array, and variable object
26153 @code{A} was created for @code{a}, then we'll get this output:
26156 (gdb) -var-info-expression A.1
26157 ^done,lang="C",exp="1"
26161 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26163 Note that the output of the @code{-var-list-children} command also
26164 includes those expressions, so the @code{-var-info-expression} command
26167 @subheading The @code{-var-info-path-expression} Command
26168 @findex -var-info-path-expression
26170 @subsubheading Synopsis
26173 -var-info-path-expression @var{name}
26176 Returns an expression that can be evaluated in the current
26177 context and will yield the same value that a variable object has.
26178 Compare this with the @code{-var-info-expression} command, which
26179 result can be used only for UI presentation. Typical use of
26180 the @code{-var-info-path-expression} command is creating a
26181 watchpoint from a variable object.
26183 This command is currently not valid for children of a dynamic varobj,
26184 and will give an error when invoked on one.
26186 For example, suppose @code{C} is a C@t{++} class, derived from class
26187 @code{Base}, and that the @code{Base} class has a member called
26188 @code{m_size}. Assume a variable @code{c} is has the type of
26189 @code{C} and a variable object @code{C} was created for variable
26190 @code{c}. Then, we'll get this output:
26192 (gdb) -var-info-path-expression C.Base.public.m_size
26193 ^done,path_expr=((Base)c).m_size)
26196 @subheading The @code{-var-show-attributes} Command
26197 @findex -var-show-attributes
26199 @subsubheading Synopsis
26202 -var-show-attributes @var{name}
26205 List attributes of the specified variable object @var{name}:
26208 status=@var{attr} [ ( ,@var{attr} )* ]
26212 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26214 @subheading The @code{-var-evaluate-expression} Command
26215 @findex -var-evaluate-expression
26217 @subsubheading Synopsis
26220 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26223 Evaluates the expression that is represented by the specified variable
26224 object and returns its value as a string. The format of the string
26225 can be specified with the @samp{-f} option. The possible values of
26226 this option are the same as for @code{-var-set-format}
26227 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26228 the current display format will be used. The current display format
26229 can be changed using the @code{-var-set-format} command.
26235 Note that one must invoke @code{-var-list-children} for a variable
26236 before the value of a child variable can be evaluated.
26238 @subheading The @code{-var-assign} Command
26239 @findex -var-assign
26241 @subsubheading Synopsis
26244 -var-assign @var{name} @var{expression}
26247 Assigns the value of @var{expression} to the variable object specified
26248 by @var{name}. The object must be @samp{editable}. If the variable's
26249 value is altered by the assign, the variable will show up in any
26250 subsequent @code{-var-update} list.
26252 @subsubheading Example
26260 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26264 @subheading The @code{-var-update} Command
26265 @findex -var-update
26267 @subsubheading Synopsis
26270 -var-update [@var{print-values}] @{@var{name} | "*"@}
26273 Reevaluate the expressions corresponding to the variable object
26274 @var{name} and all its direct and indirect children, and return the
26275 list of variable objects whose values have changed; @var{name} must
26276 be a root variable object. Here, ``changed'' means that the result of
26277 @code{-var-evaluate-expression} before and after the
26278 @code{-var-update} is different. If @samp{*} is used as the variable
26279 object names, all existing variable objects are updated, except
26280 for frozen ones (@pxref{-var-set-frozen}). The option
26281 @var{print-values} determines whether both names and values, or just
26282 names are printed. The possible values of this option are the same
26283 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26284 recommended to use the @samp{--all-values} option, to reduce the
26285 number of MI commands needed on each program stop.
26287 With the @samp{*} parameter, if a variable object is bound to a
26288 currently running thread, it will not be updated, without any
26291 If @code{-var-set-update-range} was previously used on a varobj, then
26292 only the selected range of children will be reported.
26294 @code{-var-update} reports all the changed varobjs in a tuple named
26297 Each item in the change list is itself a tuple holding:
26301 The name of the varobj.
26304 If values were requested for this update, then this field will be
26305 present and will hold the value of the varobj.
26308 @anchor{-var-update}
26309 This field is a string which may take one of three values:
26313 The variable object's current value is valid.
26316 The variable object does not currently hold a valid value but it may
26317 hold one in the future if its associated expression comes back into
26321 The variable object no longer holds a valid value.
26322 This can occur when the executable file being debugged has changed,
26323 either through recompilation or by using the @value{GDBN} @code{file}
26324 command. The front end should normally choose to delete these variable
26328 In the future new values may be added to this list so the front should
26329 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26332 This is only present if the varobj is still valid. If the type
26333 changed, then this will be the string @samp{true}; otherwise it will
26337 If the varobj's type changed, then this field will be present and will
26340 @item new_num_children
26341 For a dynamic varobj, if the number of children changed, or if the
26342 type changed, this will be the new number of children.
26344 The @samp{numchild} field in other varobj responses is generally not
26345 valid for a dynamic varobj -- it will show the number of children that
26346 @value{GDBN} knows about, but because dynamic varobjs lazily
26347 instantiate their children, this will not reflect the number of
26348 children which may be available.
26350 The @samp{new_num_children} attribute only reports changes to the
26351 number of children known by @value{GDBN}. This is the only way to
26352 detect whether an update has removed children (which necessarily can
26353 only happen at the end of the update range).
26356 The display hint, if any.
26359 This is an integer value, which will be 1 if there are more children
26360 available outside the varobj's update range.
26363 This attribute will be present and have the value @samp{1} if the
26364 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26365 then this attribute will not be present.
26368 If new children were added to a dynamic varobj within the selected
26369 update range (as set by @code{-var-set-update-range}), then they will
26370 be listed in this attribute.
26373 @subsubheading Example
26380 -var-update --all-values var1
26381 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26382 type_changed="false"@}]
26386 @subheading The @code{-var-set-frozen} Command
26387 @findex -var-set-frozen
26388 @anchor{-var-set-frozen}
26390 @subsubheading Synopsis
26393 -var-set-frozen @var{name} @var{flag}
26396 Set the frozenness flag on the variable object @var{name}. The
26397 @var{flag} parameter should be either @samp{1} to make the variable
26398 frozen or @samp{0} to make it unfrozen. If a variable object is
26399 frozen, then neither itself, nor any of its children, are
26400 implicitly updated by @code{-var-update} of
26401 a parent variable or by @code{-var-update *}. Only
26402 @code{-var-update} of the variable itself will update its value and
26403 values of its children. After a variable object is unfrozen, it is
26404 implicitly updated by all subsequent @code{-var-update} operations.
26405 Unfreezing a variable does not update it, only subsequent
26406 @code{-var-update} does.
26408 @subsubheading Example
26412 -var-set-frozen V 1
26417 @subheading The @code{-var-set-update-range} command
26418 @findex -var-set-update-range
26419 @anchor{-var-set-update-range}
26421 @subsubheading Synopsis
26424 -var-set-update-range @var{name} @var{from} @var{to}
26427 Set the range of children to be returned by future invocations of
26428 @code{-var-update}.
26430 @var{from} and @var{to} indicate the range of children to report. If
26431 @var{from} or @var{to} is less than zero, the range is reset and all
26432 children will be reported. Otherwise, children starting at @var{from}
26433 (zero-based) and up to and excluding @var{to} will be reported.
26435 @subsubheading Example
26439 -var-set-update-range V 1 2
26443 @subheading The @code{-var-set-visualizer} command
26444 @findex -var-set-visualizer
26445 @anchor{-var-set-visualizer}
26447 @subsubheading Synopsis
26450 -var-set-visualizer @var{name} @var{visualizer}
26453 Set a visualizer for the variable object @var{name}.
26455 @var{visualizer} is the visualizer to use. The special value
26456 @samp{None} means to disable any visualizer in use.
26458 If not @samp{None}, @var{visualizer} must be a Python expression.
26459 This expression must evaluate to a callable object which accepts a
26460 single argument. @value{GDBN} will call this object with the value of
26461 the varobj @var{name} as an argument (this is done so that the same
26462 Python pretty-printing code can be used for both the CLI and MI).
26463 When called, this object must return an object which conforms to the
26464 pretty-printing interface (@pxref{Pretty Printing API}).
26466 The pre-defined function @code{gdb.default_visualizer} may be used to
26467 select a visualizer by following the built-in process
26468 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26469 a varobj is created, and so ordinarily is not needed.
26471 This feature is only available if Python support is enabled. The MI
26472 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26473 can be used to check this.
26475 @subsubheading Example
26477 Resetting the visualizer:
26481 -var-set-visualizer V None
26485 Reselecting the default (type-based) visualizer:
26489 -var-set-visualizer V gdb.default_visualizer
26493 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26494 can be used to instantiate this class for a varobj:
26498 -var-set-visualizer V "lambda val: SomeClass()"
26502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26503 @node GDB/MI Data Manipulation
26504 @section @sc{gdb/mi} Data Manipulation
26506 @cindex data manipulation, in @sc{gdb/mi}
26507 @cindex @sc{gdb/mi}, data manipulation
26508 This section describes the @sc{gdb/mi} commands that manipulate data:
26509 examine memory and registers, evaluate expressions, etc.
26511 @c REMOVED FROM THE INTERFACE.
26512 @c @subheading -data-assign
26513 @c Change the value of a program variable. Plenty of side effects.
26514 @c @subsubheading GDB Command
26516 @c @subsubheading Example
26519 @subheading The @code{-data-disassemble} Command
26520 @findex -data-disassemble
26522 @subsubheading Synopsis
26526 [ -s @var{start-addr} -e @var{end-addr} ]
26527 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26535 @item @var{start-addr}
26536 is the beginning address (or @code{$pc})
26537 @item @var{end-addr}
26539 @item @var{filename}
26540 is the name of the file to disassemble
26541 @item @var{linenum}
26542 is the line number to disassemble around
26544 is the number of disassembly lines to be produced. If it is -1,
26545 the whole function will be disassembled, in case no @var{end-addr} is
26546 specified. If @var{end-addr} is specified as a non-zero value, and
26547 @var{lines} is lower than the number of disassembly lines between
26548 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26549 displayed; if @var{lines} is higher than the number of lines between
26550 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26553 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26557 @subsubheading Result
26559 The output for each instruction is composed of four fields:
26568 Note that whatever included in the instruction field, is not manipulated
26569 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26571 @subsubheading @value{GDBN} Command
26573 There's no direct mapping from this command to the CLI.
26575 @subsubheading Example
26577 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26581 -data-disassemble -s $pc -e "$pc + 20" -- 0
26584 @{address="0x000107c0",func-name="main",offset="4",
26585 inst="mov 2, %o0"@},
26586 @{address="0x000107c4",func-name="main",offset="8",
26587 inst="sethi %hi(0x11800), %o2"@},
26588 @{address="0x000107c8",func-name="main",offset="12",
26589 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26590 @{address="0x000107cc",func-name="main",offset="16",
26591 inst="sethi %hi(0x11800), %o2"@},
26592 @{address="0x000107d0",func-name="main",offset="20",
26593 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26597 Disassemble the whole @code{main} function. Line 32 is part of
26601 -data-disassemble -f basics.c -l 32 -- 0
26603 @{address="0x000107bc",func-name="main",offset="0",
26604 inst="save %sp, -112, %sp"@},
26605 @{address="0x000107c0",func-name="main",offset="4",
26606 inst="mov 2, %o0"@},
26607 @{address="0x000107c4",func-name="main",offset="8",
26608 inst="sethi %hi(0x11800), %o2"@},
26610 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26611 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26615 Disassemble 3 instructions from the start of @code{main}:
26619 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26621 @{address="0x000107bc",func-name="main",offset="0",
26622 inst="save %sp, -112, %sp"@},
26623 @{address="0x000107c0",func-name="main",offset="4",
26624 inst="mov 2, %o0"@},
26625 @{address="0x000107c4",func-name="main",offset="8",
26626 inst="sethi %hi(0x11800), %o2"@}]
26630 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26634 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26636 src_and_asm_line=@{line="31",
26637 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26638 testsuite/gdb.mi/basics.c",line_asm_insn=[
26639 @{address="0x000107bc",func-name="main",offset="0",
26640 inst="save %sp, -112, %sp"@}]@},
26641 src_and_asm_line=@{line="32",
26642 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26643 testsuite/gdb.mi/basics.c",line_asm_insn=[
26644 @{address="0x000107c0",func-name="main",offset="4",
26645 inst="mov 2, %o0"@},
26646 @{address="0x000107c4",func-name="main",offset="8",
26647 inst="sethi %hi(0x11800), %o2"@}]@}]
26652 @subheading The @code{-data-evaluate-expression} Command
26653 @findex -data-evaluate-expression
26655 @subsubheading Synopsis
26658 -data-evaluate-expression @var{expr}
26661 Evaluate @var{expr} as an expression. The expression could contain an
26662 inferior function call. The function call will execute synchronously.
26663 If the expression contains spaces, it must be enclosed in double quotes.
26665 @subsubheading @value{GDBN} Command
26667 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26668 @samp{call}. In @code{gdbtk} only, there's a corresponding
26669 @samp{gdb_eval} command.
26671 @subsubheading Example
26673 In the following example, the numbers that precede the commands are the
26674 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26675 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26679 211-data-evaluate-expression A
26682 311-data-evaluate-expression &A
26683 311^done,value="0xefffeb7c"
26685 411-data-evaluate-expression A+3
26688 511-data-evaluate-expression "A + 3"
26694 @subheading The @code{-data-list-changed-registers} Command
26695 @findex -data-list-changed-registers
26697 @subsubheading Synopsis
26700 -data-list-changed-registers
26703 Display a list of the registers that have changed.
26705 @subsubheading @value{GDBN} Command
26707 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26708 has the corresponding command @samp{gdb_changed_register_list}.
26710 @subsubheading Example
26712 On a PPC MBX board:
26720 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26721 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26724 -data-list-changed-registers
26725 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26726 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26727 "24","25","26","27","28","30","31","64","65","66","67","69"]
26732 @subheading The @code{-data-list-register-names} Command
26733 @findex -data-list-register-names
26735 @subsubheading Synopsis
26738 -data-list-register-names [ ( @var{regno} )+ ]
26741 Show a list of register names for the current target. If no arguments
26742 are given, it shows a list of the names of all the registers. If
26743 integer numbers are given as arguments, it will print a list of the
26744 names of the registers corresponding to the arguments. To ensure
26745 consistency between a register name and its number, the output list may
26746 include empty register names.
26748 @subsubheading @value{GDBN} Command
26750 @value{GDBN} does not have a command which corresponds to
26751 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26752 corresponding command @samp{gdb_regnames}.
26754 @subsubheading Example
26756 For the PPC MBX board:
26759 -data-list-register-names
26760 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26761 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26762 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26763 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26764 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26765 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26766 "", "pc","ps","cr","lr","ctr","xer"]
26768 -data-list-register-names 1 2 3
26769 ^done,register-names=["r1","r2","r3"]
26773 @subheading The @code{-data-list-register-values} Command
26774 @findex -data-list-register-values
26776 @subsubheading Synopsis
26779 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26782 Display the registers' contents. @var{fmt} is the format according to
26783 which the registers' contents are to be returned, followed by an optional
26784 list of numbers specifying the registers to display. A missing list of
26785 numbers indicates that the contents of all the registers must be returned.
26787 Allowed formats for @var{fmt} are:
26804 @subsubheading @value{GDBN} Command
26806 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26807 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26809 @subsubheading Example
26811 For a PPC MBX board (note: line breaks are for readability only, they
26812 don't appear in the actual output):
26816 -data-list-register-values r 64 65
26817 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26818 @{number="65",value="0x00029002"@}]
26820 -data-list-register-values x
26821 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
26822 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
26823 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
26824 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
26825 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
26826 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
26827 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
26828 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
26829 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
26830 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
26831 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
26832 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
26833 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
26834 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
26835 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
26836 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
26837 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
26838 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
26839 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
26840 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
26841 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
26842 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
26843 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
26844 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
26845 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
26846 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
26847 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
26848 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
26849 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
26850 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
26851 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
26852 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
26853 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
26854 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
26855 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
26856 @{number="69",value="0x20002b03"@}]
26861 @subheading The @code{-data-read-memory} Command
26862 @findex -data-read-memory
26864 @subsubheading Synopsis
26867 -data-read-memory [ -o @var{byte-offset} ]
26868 @var{address} @var{word-format} @var{word-size}
26869 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
26876 @item @var{address}
26877 An expression specifying the address of the first memory word to be
26878 read. Complex expressions containing embedded white space should be
26879 quoted using the C convention.
26881 @item @var{word-format}
26882 The format to be used to print the memory words. The notation is the
26883 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
26886 @item @var{word-size}
26887 The size of each memory word in bytes.
26889 @item @var{nr-rows}
26890 The number of rows in the output table.
26892 @item @var{nr-cols}
26893 The number of columns in the output table.
26896 If present, indicates that each row should include an @sc{ascii} dump. The
26897 value of @var{aschar} is used as a padding character when a byte is not a
26898 member of the printable @sc{ascii} character set (printable @sc{ascii}
26899 characters are those whose code is between 32 and 126, inclusively).
26901 @item @var{byte-offset}
26902 An offset to add to the @var{address} before fetching memory.
26905 This command displays memory contents as a table of @var{nr-rows} by
26906 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
26907 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
26908 (returned as @samp{total-bytes}). Should less than the requested number
26909 of bytes be returned by the target, the missing words are identified
26910 using @samp{N/A}. The number of bytes read from the target is returned
26911 in @samp{nr-bytes} and the starting address used to read memory in
26914 The address of the next/previous row or page is available in
26915 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
26918 @subsubheading @value{GDBN} Command
26920 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
26921 @samp{gdb_get_mem} memory read command.
26923 @subsubheading Example
26925 Read six bytes of memory starting at @code{bytes+6} but then offset by
26926 @code{-6} bytes. Format as three rows of two columns. One byte per
26927 word. Display each word in hex.
26931 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
26932 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
26933 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
26934 prev-page="0x0000138a",memory=[
26935 @{addr="0x00001390",data=["0x00","0x01"]@},
26936 @{addr="0x00001392",data=["0x02","0x03"]@},
26937 @{addr="0x00001394",data=["0x04","0x05"]@}]
26941 Read two bytes of memory starting at address @code{shorts + 64} and
26942 display as a single word formatted in decimal.
26946 5-data-read-memory shorts+64 d 2 1 1
26947 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26948 next-row="0x00001512",prev-row="0x0000150e",
26949 next-page="0x00001512",prev-page="0x0000150e",memory=[
26950 @{addr="0x00001510",data=["128"]@}]
26954 Read thirty two bytes of memory starting at @code{bytes+16} and format
26955 as eight rows of four columns. Include a string encoding with @samp{x}
26956 used as the non-printable character.
26960 4-data-read-memory bytes+16 x 1 8 4 x
26961 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26962 next-row="0x000013c0",prev-row="0x0000139c",
26963 next-page="0x000013c0",prev-page="0x00001380",memory=[
26964 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26965 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26966 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26967 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26968 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26969 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26970 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26971 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26976 @node GDB/MI Tracepoint Commands
26977 @section @sc{gdb/mi} Tracepoint Commands
26979 The commands defined in this section implement MI support for
26980 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26982 @subheading The @code{-trace-find} Command
26983 @findex -trace-find
26985 @subsubheading Synopsis
26988 -trace-find @var{mode} [@var{parameters}@dots{}]
26991 Find a trace frame using criteria defined by @var{mode} and
26992 @var{parameters}. The following table lists permissible
26993 modes and their parameters. For details of operation, see @ref{tfind}.
26998 No parameters are required. Stops examining trace frames.
27001 An integer is required as parameter. Selects tracepoint frame with
27004 @item tracepoint-number
27005 An integer is required as parameter. Finds next
27006 trace frame that corresponds to tracepoint with the specified number.
27009 An address is required as parameter. Finds
27010 next trace frame that corresponds to any tracepoint at the specified
27013 @item pc-inside-range
27014 Two addresses are required as parameters. Finds next trace
27015 frame that corresponds to a tracepoint at an address inside the
27016 specified range. Both bounds are considered to be inside the range.
27018 @item pc-outside-range
27019 Two addresses are required as parameters. Finds
27020 next trace frame that corresponds to a tracepoint at an address outside
27021 the specified range. Both bounds are considered to be inside the range.
27024 Line specification is required as parameter. @xref{Specify Location}.
27025 Finds next trace frame that corresponds to a tracepoint at
27026 the specified location.
27030 If @samp{none} was passed as @var{mode}, the response does not
27031 have fields. Otherwise, the response may have the following fields:
27035 This field has either @samp{0} or @samp{1} as the value, depending
27036 on whether a matching tracepoint was found.
27039 The index of the found traceframe. This field is present iff
27040 the @samp{found} field has value of @samp{1}.
27043 The index of the found tracepoint. This field is present iff
27044 the @samp{found} field has value of @samp{1}.
27047 The information about the frame corresponding to the found trace
27048 frame. This field is present only if a trace frame was found.
27049 @xref{GDB/MI Frame Information}, for description of this field.
27053 @subsubheading @value{GDBN} Command
27055 The corresponding @value{GDBN} command is @samp{tfind}.
27057 @subheading -trace-define-variable
27058 @findex -trace-define-variable
27060 @subsubheading Synopsis
27063 -trace-define-variable @var{name} [ @var{value} ]
27066 Create trace variable @var{name} if it does not exist. If
27067 @var{value} is specified, sets the initial value of the specified
27068 trace variable to that value. Note that the @var{name} should start
27069 with the @samp{$} character.
27071 @subsubheading @value{GDBN} Command
27073 The corresponding @value{GDBN} command is @samp{tvariable}.
27075 @subheading -trace-list-variables
27076 @findex -trace-list-variables
27078 @subsubheading Synopsis
27081 -trace-list-variables
27084 Return a table of all defined trace variables. Each element of the
27085 table has the following fields:
27089 The name of the trace variable. This field is always present.
27092 The initial value. This is a 64-bit signed integer. This
27093 field is always present.
27096 The value the trace variable has at the moment. This is a 64-bit
27097 signed integer. This field is absent iff current value is
27098 not defined, for example if the trace was never run, or is
27103 @subsubheading @value{GDBN} Command
27105 The corresponding @value{GDBN} command is @samp{tvariables}.
27107 @subsubheading Example
27111 -trace-list-variables
27112 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27113 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27114 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27115 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27116 body=[variable=@{name="$trace_timestamp",initial="0"@}
27117 variable=@{name="$foo",initial="10",current="15"@}]@}
27121 @subheading -trace-save
27122 @findex -trace-save
27124 @subsubheading Synopsis
27127 -trace-save [-r ] @var{filename}
27130 Saves the collected trace data to @var{filename}. Without the
27131 @samp{-r} option, the data is downloaded from the target and saved
27132 in a local file. With the @samp{-r} option the target is asked
27133 to perform the save.
27135 @subsubheading @value{GDBN} Command
27137 The corresponding @value{GDBN} command is @samp{tsave}.
27140 @subheading -trace-start
27141 @findex -trace-start
27143 @subsubheading Synopsis
27149 Starts a tracing experiments. The result of this command does not
27152 @subsubheading @value{GDBN} Command
27154 The corresponding @value{GDBN} command is @samp{tstart}.
27156 @subheading -trace-status
27157 @findex -trace-status
27159 @subsubheading Synopsis
27165 Obtains the status of a tracing experiment. The result may include
27166 the following fields:
27171 May have a value of either @samp{0}, when no tracing operations are
27172 supported, @samp{1}, when all tracing operations are supported, or
27173 @samp{file} when examining trace file. In the latter case, examining
27174 of trace frame is possible but new tracing experiement cannot be
27175 started. This field is always present.
27178 May have a value of either @samp{0} or @samp{1} depending on whether
27179 tracing experiement is in progress on target. This field is present
27180 if @samp{supported} field is not @samp{0}.
27183 Report the reason why the tracing was stopped last time. This field
27184 may be absent iff tracing was never stopped on target yet. The
27185 value of @samp{request} means the tracing was stopped as result of
27186 the @code{-trace-stop} command. The value of @samp{overflow} means
27187 the tracing buffer is full. The value of @samp{disconnection} means
27188 tracing was automatically stopped when @value{GDBN} has disconnected.
27189 The value of @samp{passcount} means tracing was stopped when a
27190 tracepoint was passed a maximal number of times for that tracepoint.
27191 This field is present if @samp{supported} field is not @samp{0}.
27193 @item stopping-tracepoint
27194 The number of tracepoint whose passcount as exceeded. This field is
27195 present iff the @samp{stop-reason} field has the value of
27199 @itemx frames-created
27200 The @samp{frames} field is a count of the total number of trace frames
27201 in the trace buffer, while @samp{frames-created} is the total created
27202 during the run, including ones that were discarded, such as when a
27203 circular trace buffer filled up. Both fields are optional.
27207 These fields tell the current size of the tracing buffer and the
27208 remaining space. These fields are optional.
27211 The value of the circular trace buffer flag. @code{1} means that the
27212 trace buffer is circular and old trace frames will be discarded if
27213 necessary to make room, @code{0} means that the trace buffer is linear
27217 The value of the disconnected tracing flag. @code{1} means that
27218 tracing will continue after @value{GDBN} disconnects, @code{0} means
27219 that the trace run will stop.
27223 @subsubheading @value{GDBN} Command
27225 The corresponding @value{GDBN} command is @samp{tstatus}.
27227 @subheading -trace-stop
27228 @findex -trace-stop
27230 @subsubheading Synopsis
27236 Stops a tracing experiment. The result of this command has the same
27237 fields as @code{-trace-status}, except that the @samp{supported} and
27238 @samp{running} fields are not output.
27240 @subsubheading @value{GDBN} Command
27242 The corresponding @value{GDBN} command is @samp{tstop}.
27245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27246 @node GDB/MI Symbol Query
27247 @section @sc{gdb/mi} Symbol Query Commands
27251 @subheading The @code{-symbol-info-address} Command
27252 @findex -symbol-info-address
27254 @subsubheading Synopsis
27257 -symbol-info-address @var{symbol}
27260 Describe where @var{symbol} is stored.
27262 @subsubheading @value{GDBN} Command
27264 The corresponding @value{GDBN} command is @samp{info address}.
27266 @subsubheading Example
27270 @subheading The @code{-symbol-info-file} Command
27271 @findex -symbol-info-file
27273 @subsubheading Synopsis
27279 Show the file for the symbol.
27281 @subsubheading @value{GDBN} Command
27283 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27284 @samp{gdb_find_file}.
27286 @subsubheading Example
27290 @subheading The @code{-symbol-info-function} Command
27291 @findex -symbol-info-function
27293 @subsubheading Synopsis
27296 -symbol-info-function
27299 Show which function the symbol lives in.
27301 @subsubheading @value{GDBN} Command
27303 @samp{gdb_get_function} in @code{gdbtk}.
27305 @subsubheading Example
27309 @subheading The @code{-symbol-info-line} Command
27310 @findex -symbol-info-line
27312 @subsubheading Synopsis
27318 Show the core addresses of the code for a source line.
27320 @subsubheading @value{GDBN} Command
27322 The corresponding @value{GDBN} command is @samp{info line}.
27323 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27325 @subsubheading Example
27329 @subheading The @code{-symbol-info-symbol} Command
27330 @findex -symbol-info-symbol
27332 @subsubheading Synopsis
27335 -symbol-info-symbol @var{addr}
27338 Describe what symbol is at location @var{addr}.
27340 @subsubheading @value{GDBN} Command
27342 The corresponding @value{GDBN} command is @samp{info symbol}.
27344 @subsubheading Example
27348 @subheading The @code{-symbol-list-functions} Command
27349 @findex -symbol-list-functions
27351 @subsubheading Synopsis
27354 -symbol-list-functions
27357 List the functions in the executable.
27359 @subsubheading @value{GDBN} Command
27361 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27362 @samp{gdb_search} in @code{gdbtk}.
27364 @subsubheading Example
27369 @subheading The @code{-symbol-list-lines} Command
27370 @findex -symbol-list-lines
27372 @subsubheading Synopsis
27375 -symbol-list-lines @var{filename}
27378 Print the list of lines that contain code and their associated program
27379 addresses for the given source filename. The entries are sorted in
27380 ascending PC order.
27382 @subsubheading @value{GDBN} Command
27384 There is no corresponding @value{GDBN} command.
27386 @subsubheading Example
27389 -symbol-list-lines basics.c
27390 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27396 @subheading The @code{-symbol-list-types} Command
27397 @findex -symbol-list-types
27399 @subsubheading Synopsis
27405 List all the type names.
27407 @subsubheading @value{GDBN} Command
27409 The corresponding commands are @samp{info types} in @value{GDBN},
27410 @samp{gdb_search} in @code{gdbtk}.
27412 @subsubheading Example
27416 @subheading The @code{-symbol-list-variables} Command
27417 @findex -symbol-list-variables
27419 @subsubheading Synopsis
27422 -symbol-list-variables
27425 List all the global and static variable names.
27427 @subsubheading @value{GDBN} Command
27429 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27431 @subsubheading Example
27435 @subheading The @code{-symbol-locate} Command
27436 @findex -symbol-locate
27438 @subsubheading Synopsis
27444 @subsubheading @value{GDBN} Command
27446 @samp{gdb_loc} in @code{gdbtk}.
27448 @subsubheading Example
27452 @subheading The @code{-symbol-type} Command
27453 @findex -symbol-type
27455 @subsubheading Synopsis
27458 -symbol-type @var{variable}
27461 Show type of @var{variable}.
27463 @subsubheading @value{GDBN} Command
27465 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27466 @samp{gdb_obj_variable}.
27468 @subsubheading Example
27473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27474 @node GDB/MI File Commands
27475 @section @sc{gdb/mi} File Commands
27477 This section describes the GDB/MI commands to specify executable file names
27478 and to read in and obtain symbol table information.
27480 @subheading The @code{-file-exec-and-symbols} Command
27481 @findex -file-exec-and-symbols
27483 @subsubheading Synopsis
27486 -file-exec-and-symbols @var{file}
27489 Specify the executable file to be debugged. This file is the one from
27490 which the symbol table is also read. If no file is specified, the
27491 command clears the executable and symbol information. If breakpoints
27492 are set when using this command with no arguments, @value{GDBN} will produce
27493 error messages. Otherwise, no output is produced, except a completion
27496 @subsubheading @value{GDBN} Command
27498 The corresponding @value{GDBN} command is @samp{file}.
27500 @subsubheading Example
27504 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27510 @subheading The @code{-file-exec-file} Command
27511 @findex -file-exec-file
27513 @subsubheading Synopsis
27516 -file-exec-file @var{file}
27519 Specify the executable file to be debugged. Unlike
27520 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27521 from this file. If used without argument, @value{GDBN} clears the information
27522 about the executable file. No output is produced, except a completion
27525 @subsubheading @value{GDBN} Command
27527 The corresponding @value{GDBN} command is @samp{exec-file}.
27529 @subsubheading Example
27533 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27540 @subheading The @code{-file-list-exec-sections} Command
27541 @findex -file-list-exec-sections
27543 @subsubheading Synopsis
27546 -file-list-exec-sections
27549 List the sections of the current executable file.
27551 @subsubheading @value{GDBN} Command
27553 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27554 information as this command. @code{gdbtk} has a corresponding command
27555 @samp{gdb_load_info}.
27557 @subsubheading Example
27562 @subheading The @code{-file-list-exec-source-file} Command
27563 @findex -file-list-exec-source-file
27565 @subsubheading Synopsis
27568 -file-list-exec-source-file
27571 List the line number, the current source file, and the absolute path
27572 to the current source file for the current executable. The macro
27573 information field has a value of @samp{1} or @samp{0} depending on
27574 whether or not the file includes preprocessor macro information.
27576 @subsubheading @value{GDBN} Command
27578 The @value{GDBN} equivalent is @samp{info source}
27580 @subsubheading Example
27584 123-file-list-exec-source-file
27585 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27590 @subheading The @code{-file-list-exec-source-files} Command
27591 @findex -file-list-exec-source-files
27593 @subsubheading Synopsis
27596 -file-list-exec-source-files
27599 List the source files for the current executable.
27601 It will always output the filename, but only when @value{GDBN} can find
27602 the absolute file name of a source file, will it output the fullname.
27604 @subsubheading @value{GDBN} Command
27606 The @value{GDBN} equivalent is @samp{info sources}.
27607 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27609 @subsubheading Example
27612 -file-list-exec-source-files
27614 @{file=foo.c,fullname=/home/foo.c@},
27615 @{file=/home/bar.c,fullname=/home/bar.c@},
27616 @{file=gdb_could_not_find_fullpath.c@}]
27621 @subheading The @code{-file-list-shared-libraries} Command
27622 @findex -file-list-shared-libraries
27624 @subsubheading Synopsis
27627 -file-list-shared-libraries
27630 List the shared libraries in the program.
27632 @subsubheading @value{GDBN} Command
27634 The corresponding @value{GDBN} command is @samp{info shared}.
27636 @subsubheading Example
27640 @subheading The @code{-file-list-symbol-files} Command
27641 @findex -file-list-symbol-files
27643 @subsubheading Synopsis
27646 -file-list-symbol-files
27651 @subsubheading @value{GDBN} Command
27653 The corresponding @value{GDBN} command is @samp{info file} (part of it).
27655 @subsubheading Example
27660 @subheading The @code{-file-symbol-file} Command
27661 @findex -file-symbol-file
27663 @subsubheading Synopsis
27666 -file-symbol-file @var{file}
27669 Read symbol table info from the specified @var{file} argument. When
27670 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27671 produced, except for a completion notification.
27673 @subsubheading @value{GDBN} Command
27675 The corresponding @value{GDBN} command is @samp{symbol-file}.
27677 @subsubheading Example
27681 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27688 @node GDB/MI Memory Overlay Commands
27689 @section @sc{gdb/mi} Memory Overlay Commands
27691 The memory overlay commands are not implemented.
27693 @c @subheading -overlay-auto
27695 @c @subheading -overlay-list-mapping-state
27697 @c @subheading -overlay-list-overlays
27699 @c @subheading -overlay-map
27701 @c @subheading -overlay-off
27703 @c @subheading -overlay-on
27705 @c @subheading -overlay-unmap
27707 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27708 @node GDB/MI Signal Handling Commands
27709 @section @sc{gdb/mi} Signal Handling Commands
27711 Signal handling commands are not implemented.
27713 @c @subheading -signal-handle
27715 @c @subheading -signal-list-handle-actions
27717 @c @subheading -signal-list-signal-types
27721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27722 @node GDB/MI Target Manipulation
27723 @section @sc{gdb/mi} Target Manipulation Commands
27726 @subheading The @code{-target-attach} Command
27727 @findex -target-attach
27729 @subsubheading Synopsis
27732 -target-attach @var{pid} | @var{gid} | @var{file}
27735 Attach to a process @var{pid} or a file @var{file} outside of
27736 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27737 group, the id previously returned by
27738 @samp{-list-thread-groups --available} must be used.
27740 @subsubheading @value{GDBN} Command
27742 The corresponding @value{GDBN} command is @samp{attach}.
27744 @subsubheading Example
27748 =thread-created,id="1"
27749 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27755 @subheading The @code{-target-compare-sections} Command
27756 @findex -target-compare-sections
27758 @subsubheading Synopsis
27761 -target-compare-sections [ @var{section} ]
27764 Compare data of section @var{section} on target to the exec file.
27765 Without the argument, all sections are compared.
27767 @subsubheading @value{GDBN} Command
27769 The @value{GDBN} equivalent is @samp{compare-sections}.
27771 @subsubheading Example
27776 @subheading The @code{-target-detach} Command
27777 @findex -target-detach
27779 @subsubheading Synopsis
27782 -target-detach [ @var{pid} | @var{gid} ]
27785 Detach from the remote target which normally resumes its execution.
27786 If either @var{pid} or @var{gid} is specified, detaches from either
27787 the specified process, or specified thread group. There's no output.
27789 @subsubheading @value{GDBN} Command
27791 The corresponding @value{GDBN} command is @samp{detach}.
27793 @subsubheading Example
27803 @subheading The @code{-target-disconnect} Command
27804 @findex -target-disconnect
27806 @subsubheading Synopsis
27812 Disconnect from the remote target. There's no output and the target is
27813 generally not resumed.
27815 @subsubheading @value{GDBN} Command
27817 The corresponding @value{GDBN} command is @samp{disconnect}.
27819 @subsubheading Example
27829 @subheading The @code{-target-download} Command
27830 @findex -target-download
27832 @subsubheading Synopsis
27838 Loads the executable onto the remote target.
27839 It prints out an update message every half second, which includes the fields:
27843 The name of the section.
27845 The size of what has been sent so far for that section.
27847 The size of the section.
27849 The total size of what was sent so far (the current and the previous sections).
27851 The size of the overall executable to download.
27855 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
27856 @sc{gdb/mi} Output Syntax}).
27858 In addition, it prints the name and size of the sections, as they are
27859 downloaded. These messages include the following fields:
27863 The name of the section.
27865 The size of the section.
27867 The size of the overall executable to download.
27871 At the end, a summary is printed.
27873 @subsubheading @value{GDBN} Command
27875 The corresponding @value{GDBN} command is @samp{load}.
27877 @subsubheading Example
27879 Note: each status message appears on a single line. Here the messages
27880 have been broken down so that they can fit onto a page.
27885 +download,@{section=".text",section-size="6668",total-size="9880"@}
27886 +download,@{section=".text",section-sent="512",section-size="6668",
27887 total-sent="512",total-size="9880"@}
27888 +download,@{section=".text",section-sent="1024",section-size="6668",
27889 total-sent="1024",total-size="9880"@}
27890 +download,@{section=".text",section-sent="1536",section-size="6668",
27891 total-sent="1536",total-size="9880"@}
27892 +download,@{section=".text",section-sent="2048",section-size="6668",
27893 total-sent="2048",total-size="9880"@}
27894 +download,@{section=".text",section-sent="2560",section-size="6668",
27895 total-sent="2560",total-size="9880"@}
27896 +download,@{section=".text",section-sent="3072",section-size="6668",
27897 total-sent="3072",total-size="9880"@}
27898 +download,@{section=".text",section-sent="3584",section-size="6668",
27899 total-sent="3584",total-size="9880"@}
27900 +download,@{section=".text",section-sent="4096",section-size="6668",
27901 total-sent="4096",total-size="9880"@}
27902 +download,@{section=".text",section-sent="4608",section-size="6668",
27903 total-sent="4608",total-size="9880"@}
27904 +download,@{section=".text",section-sent="5120",section-size="6668",
27905 total-sent="5120",total-size="9880"@}
27906 +download,@{section=".text",section-sent="5632",section-size="6668",
27907 total-sent="5632",total-size="9880"@}
27908 +download,@{section=".text",section-sent="6144",section-size="6668",
27909 total-sent="6144",total-size="9880"@}
27910 +download,@{section=".text",section-sent="6656",section-size="6668",
27911 total-sent="6656",total-size="9880"@}
27912 +download,@{section=".init",section-size="28",total-size="9880"@}
27913 +download,@{section=".fini",section-size="28",total-size="9880"@}
27914 +download,@{section=".data",section-size="3156",total-size="9880"@}
27915 +download,@{section=".data",section-sent="512",section-size="3156",
27916 total-sent="7236",total-size="9880"@}
27917 +download,@{section=".data",section-sent="1024",section-size="3156",
27918 total-sent="7748",total-size="9880"@}
27919 +download,@{section=".data",section-sent="1536",section-size="3156",
27920 total-sent="8260",total-size="9880"@}
27921 +download,@{section=".data",section-sent="2048",section-size="3156",
27922 total-sent="8772",total-size="9880"@}
27923 +download,@{section=".data",section-sent="2560",section-size="3156",
27924 total-sent="9284",total-size="9880"@}
27925 +download,@{section=".data",section-sent="3072",section-size="3156",
27926 total-sent="9796",total-size="9880"@}
27927 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
27934 @subheading The @code{-target-exec-status} Command
27935 @findex -target-exec-status
27937 @subsubheading Synopsis
27940 -target-exec-status
27943 Provide information on the state of the target (whether it is running or
27944 not, for instance).
27946 @subsubheading @value{GDBN} Command
27948 There's no equivalent @value{GDBN} command.
27950 @subsubheading Example
27954 @subheading The @code{-target-list-available-targets} Command
27955 @findex -target-list-available-targets
27957 @subsubheading Synopsis
27960 -target-list-available-targets
27963 List the possible targets to connect to.
27965 @subsubheading @value{GDBN} Command
27967 The corresponding @value{GDBN} command is @samp{help target}.
27969 @subsubheading Example
27973 @subheading The @code{-target-list-current-targets} Command
27974 @findex -target-list-current-targets
27976 @subsubheading Synopsis
27979 -target-list-current-targets
27982 Describe the current target.
27984 @subsubheading @value{GDBN} Command
27986 The corresponding information is printed by @samp{info file} (among
27989 @subsubheading Example
27993 @subheading The @code{-target-list-parameters} Command
27994 @findex -target-list-parameters
27996 @subsubheading Synopsis
27999 -target-list-parameters
28005 @subsubheading @value{GDBN} Command
28009 @subsubheading Example
28013 @subheading The @code{-target-select} Command
28014 @findex -target-select
28016 @subsubheading Synopsis
28019 -target-select @var{type} @var{parameters @dots{}}
28022 Connect @value{GDBN} to the remote target. This command takes two args:
28026 The type of target, for instance @samp{remote}, etc.
28027 @item @var{parameters}
28028 Device names, host names and the like. @xref{Target Commands, ,
28029 Commands for Managing Targets}, for more details.
28032 The output is a connection notification, followed by the address at
28033 which the target program is, in the following form:
28036 ^connected,addr="@var{address}",func="@var{function name}",
28037 args=[@var{arg list}]
28040 @subsubheading @value{GDBN} Command
28042 The corresponding @value{GDBN} command is @samp{target}.
28044 @subsubheading Example
28048 -target-select remote /dev/ttya
28049 ^connected,addr="0xfe00a300",func="??",args=[]
28053 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28054 @node GDB/MI File Transfer Commands
28055 @section @sc{gdb/mi} File Transfer Commands
28058 @subheading The @code{-target-file-put} Command
28059 @findex -target-file-put
28061 @subsubheading Synopsis
28064 -target-file-put @var{hostfile} @var{targetfile}
28067 Copy file @var{hostfile} from the host system (the machine running
28068 @value{GDBN}) to @var{targetfile} on the target system.
28070 @subsubheading @value{GDBN} Command
28072 The corresponding @value{GDBN} command is @samp{remote put}.
28074 @subsubheading Example
28078 -target-file-put localfile remotefile
28084 @subheading The @code{-target-file-get} Command
28085 @findex -target-file-get
28087 @subsubheading Synopsis
28090 -target-file-get @var{targetfile} @var{hostfile}
28093 Copy file @var{targetfile} from the target system to @var{hostfile}
28094 on the host system.
28096 @subsubheading @value{GDBN} Command
28098 The corresponding @value{GDBN} command is @samp{remote get}.
28100 @subsubheading Example
28104 -target-file-get remotefile localfile
28110 @subheading The @code{-target-file-delete} Command
28111 @findex -target-file-delete
28113 @subsubheading Synopsis
28116 -target-file-delete @var{targetfile}
28119 Delete @var{targetfile} from the target system.
28121 @subsubheading @value{GDBN} Command
28123 The corresponding @value{GDBN} command is @samp{remote delete}.
28125 @subsubheading Example
28129 -target-file-delete remotefile
28135 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28136 @node GDB/MI Miscellaneous Commands
28137 @section Miscellaneous @sc{gdb/mi} Commands
28139 @c @subheading -gdb-complete
28141 @subheading The @code{-gdb-exit} Command
28144 @subsubheading Synopsis
28150 Exit @value{GDBN} immediately.
28152 @subsubheading @value{GDBN} Command
28154 Approximately corresponds to @samp{quit}.
28156 @subsubheading Example
28166 @subheading The @code{-exec-abort} Command
28167 @findex -exec-abort
28169 @subsubheading Synopsis
28175 Kill the inferior running program.
28177 @subsubheading @value{GDBN} Command
28179 The corresponding @value{GDBN} command is @samp{kill}.
28181 @subsubheading Example
28186 @subheading The @code{-gdb-set} Command
28189 @subsubheading Synopsis
28195 Set an internal @value{GDBN} variable.
28196 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28198 @subsubheading @value{GDBN} Command
28200 The corresponding @value{GDBN} command is @samp{set}.
28202 @subsubheading Example
28212 @subheading The @code{-gdb-show} Command
28215 @subsubheading Synopsis
28221 Show the current value of a @value{GDBN} variable.
28223 @subsubheading @value{GDBN} Command
28225 The corresponding @value{GDBN} command is @samp{show}.
28227 @subsubheading Example
28236 @c @subheading -gdb-source
28239 @subheading The @code{-gdb-version} Command
28240 @findex -gdb-version
28242 @subsubheading Synopsis
28248 Show version information for @value{GDBN}. Used mostly in testing.
28250 @subsubheading @value{GDBN} Command
28252 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28253 default shows this information when you start an interactive session.
28255 @subsubheading Example
28257 @c This example modifies the actual output from GDB to avoid overfull
28263 ~Copyright 2000 Free Software Foundation, Inc.
28264 ~GDB is free software, covered by the GNU General Public License, and
28265 ~you are welcome to change it and/or distribute copies of it under
28266 ~ certain conditions.
28267 ~Type "show copying" to see the conditions.
28268 ~There is absolutely no warranty for GDB. Type "show warranty" for
28270 ~This GDB was configured as
28271 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28276 @subheading The @code{-list-features} Command
28277 @findex -list-features
28279 Returns a list of particular features of the MI protocol that
28280 this version of gdb implements. A feature can be a command,
28281 or a new field in an output of some command, or even an
28282 important bugfix. While a frontend can sometimes detect presence
28283 of a feature at runtime, it is easier to perform detection at debugger
28286 The command returns a list of strings, with each string naming an
28287 available feature. Each returned string is just a name, it does not
28288 have any internal structure. The list of possible feature names
28294 (gdb) -list-features
28295 ^done,result=["feature1","feature2"]
28298 The current list of features is:
28301 @item frozen-varobjs
28302 Indicates presence of the @code{-var-set-frozen} command, as well
28303 as possible presense of the @code{frozen} field in the output
28304 of @code{-varobj-create}.
28305 @item pending-breakpoints
28306 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28308 Indicates presence of Python scripting support, Python-based
28309 pretty-printing commands, and possible presence of the
28310 @samp{display_hint} field in the output of @code{-var-list-children}
28312 Indicates presence of the @code{-thread-info} command.
28316 @subheading The @code{-list-target-features} Command
28317 @findex -list-target-features
28319 Returns a list of particular features that are supported by the
28320 target. Those features affect the permitted MI commands, but
28321 unlike the features reported by the @code{-list-features} command, the
28322 features depend on which target GDB is using at the moment. Whenever
28323 a target can change, due to commands such as @code{-target-select},
28324 @code{-target-attach} or @code{-exec-run}, the list of target features
28325 may change, and the frontend should obtain it again.
28329 (gdb) -list-features
28330 ^done,result=["async"]
28333 The current list of features is:
28337 Indicates that the target is capable of asynchronous command
28338 execution, which means that @value{GDBN} will accept further commands
28339 while the target is running.
28343 @subheading The @code{-list-thread-groups} Command
28344 @findex -list-thread-groups
28346 @subheading Synopsis
28349 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28352 Lists thread groups (@pxref{Thread groups}). When a single thread
28353 group is passed as the argument, lists the children of that group.
28354 When several thread group are passed, lists information about those
28355 thread groups. Without any parameters, lists information about all
28356 top-level thread groups.
28358 Normally, thread groups that are being debugged are reported.
28359 With the @samp{--available} option, @value{GDBN} reports thread groups
28360 available on the target.
28362 The output of this command may have either a @samp{threads} result or
28363 a @samp{groups} result. The @samp{thread} result has a list of tuples
28364 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28365 Information}). The @samp{groups} result has a list of tuples as value,
28366 each tuple describing a thread group. If top-level groups are
28367 requested (that is, no parameter is passed), or when several groups
28368 are passed, the output always has a @samp{groups} result. The format
28369 of the @samp{group} result is described below.
28371 To reduce the number of roundtrips it's possible to list thread groups
28372 together with their children, by passing the @samp{--recurse} option
28373 and the recursion depth. Presently, only recursion depth of 1 is
28374 permitted. If this option is present, then every reported thread group
28375 will also include its children, either as @samp{group} or
28376 @samp{threads} field.
28378 In general, any combination of option and parameters is permitted, with
28379 the following caveats:
28383 When a single thread group is passed, the output will typically
28384 be the @samp{threads} result. Because threads may not contain
28385 anything, the @samp{recurse} option will be ignored.
28388 When the @samp{--available} option is passed, limited information may
28389 be available. In particular, the list of threads of a process might
28390 be inaccessible. Further, specifying specific thread groups might
28391 not give any performance advantage over listing all thread groups.
28392 The frontend should assume that @samp{-list-thread-groups --available}
28393 is always an expensive operation and cache the results.
28397 The @samp{groups} result is a list of tuples, where each tuple may
28398 have the following fields:
28402 Identifier of the thread group. This field is always present.
28403 The identifier is an opaque string; frontends should not try to
28404 convert it to an integer, even though it might look like one.
28407 The type of the thread group. At present, only @samp{process} is a
28411 The target-specific process identifier. This field is only present
28412 for thread groups of type @samp{process} and only if the process exists.
28415 The number of children this thread group has. This field may be
28416 absent for an available thread group.
28419 This field has a list of tuples as value, each tuple describing a
28420 thread. It may be present if the @samp{--recurse} option is
28421 specified, and it's actually possible to obtain the threads.
28424 This field is a list of integers, each identifying a core that one
28425 thread of the group is running on. This field may be absent if
28426 such information is not available.
28429 The name of the executable file that corresponds to this thread group.
28430 The field is only present for thread groups of type @samp{process},
28431 and only if there is a corresponding executable file.
28435 @subheading Example
28439 -list-thread-groups
28440 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28441 -list-thread-groups 17
28442 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28443 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28444 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28445 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28446 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28447 -list-thread-groups --available
28448 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28449 -list-thread-groups --available --recurse 1
28450 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28451 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28452 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28453 -list-thread-groups --available --recurse 1 17 18
28454 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28455 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28456 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28460 @subheading The @code{-add-inferior} Command
28461 @findex -add-inferior
28463 @subheading Synopsis
28469 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28470 inferior is not associated with any executable. Such association may
28471 be established with the @samp{-file-exec-and-symbols} command
28472 (@pxref{GDB/MI File Commands}). The command response has a single
28473 field, @samp{thread-group}, whose value is the identifier of the
28474 thread group corresponding to the new inferior.
28476 @subheading Example
28481 ^done,thread-group="i3"
28484 @subheading The @code{-interpreter-exec} Command
28485 @findex -interpreter-exec
28487 @subheading Synopsis
28490 -interpreter-exec @var{interpreter} @var{command}
28492 @anchor{-interpreter-exec}
28494 Execute the specified @var{command} in the given @var{interpreter}.
28496 @subheading @value{GDBN} Command
28498 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28500 @subheading Example
28504 -interpreter-exec console "break main"
28505 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28506 &"During symbol reading, bad structure-type format.\n"
28507 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28512 @subheading The @code{-inferior-tty-set} Command
28513 @findex -inferior-tty-set
28515 @subheading Synopsis
28518 -inferior-tty-set /dev/pts/1
28521 Set terminal for future runs of the program being debugged.
28523 @subheading @value{GDBN} Command
28525 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28527 @subheading Example
28531 -inferior-tty-set /dev/pts/1
28536 @subheading The @code{-inferior-tty-show} Command
28537 @findex -inferior-tty-show
28539 @subheading Synopsis
28545 Show terminal for future runs of program being debugged.
28547 @subheading @value{GDBN} Command
28549 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28551 @subheading Example
28555 -inferior-tty-set /dev/pts/1
28559 ^done,inferior_tty_terminal="/dev/pts/1"
28563 @subheading The @code{-enable-timings} Command
28564 @findex -enable-timings
28566 @subheading Synopsis
28569 -enable-timings [yes | no]
28572 Toggle the printing of the wallclock, user and system times for an MI
28573 command as a field in its output. This command is to help frontend
28574 developers optimize the performance of their code. No argument is
28575 equivalent to @samp{yes}.
28577 @subheading @value{GDBN} Command
28581 @subheading Example
28589 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28590 addr="0x080484ed",func="main",file="myprog.c",
28591 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28592 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28600 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28601 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28602 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28603 fullname="/home/nickrob/myprog.c",line="73"@}
28608 @chapter @value{GDBN} Annotations
28610 This chapter describes annotations in @value{GDBN}. Annotations were
28611 designed to interface @value{GDBN} to graphical user interfaces or other
28612 similar programs which want to interact with @value{GDBN} at a
28613 relatively high level.
28615 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28619 This is Edition @value{EDITION}, @value{DATE}.
28623 * Annotations Overview:: What annotations are; the general syntax.
28624 * Server Prefix:: Issuing a command without affecting user state.
28625 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28626 * Errors:: Annotations for error messages.
28627 * Invalidation:: Some annotations describe things now invalid.
28628 * Annotations for Running::
28629 Whether the program is running, how it stopped, etc.
28630 * Source Annotations:: Annotations describing source code.
28633 @node Annotations Overview
28634 @section What is an Annotation?
28635 @cindex annotations
28637 Annotations start with a newline character, two @samp{control-z}
28638 characters, and the name of the annotation. If there is no additional
28639 information associated with this annotation, the name of the annotation
28640 is followed immediately by a newline. If there is additional
28641 information, the name of the annotation is followed by a space, the
28642 additional information, and a newline. The additional information
28643 cannot contain newline characters.
28645 Any output not beginning with a newline and two @samp{control-z}
28646 characters denotes literal output from @value{GDBN}. Currently there is
28647 no need for @value{GDBN} to output a newline followed by two
28648 @samp{control-z} characters, but if there was such a need, the
28649 annotations could be extended with an @samp{escape} annotation which
28650 means those three characters as output.
28652 The annotation @var{level}, which is specified using the
28653 @option{--annotate} command line option (@pxref{Mode Options}), controls
28654 how much information @value{GDBN} prints together with its prompt,
28655 values of expressions, source lines, and other types of output. Level 0
28656 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28657 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28658 for programs that control @value{GDBN}, and level 2 annotations have
28659 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28660 Interface, annotate, GDB's Obsolete Annotations}).
28663 @kindex set annotate
28664 @item set annotate @var{level}
28665 The @value{GDBN} command @code{set annotate} sets the level of
28666 annotations to the specified @var{level}.
28668 @item show annotate
28669 @kindex show annotate
28670 Show the current annotation level.
28673 This chapter describes level 3 annotations.
28675 A simple example of starting up @value{GDBN} with annotations is:
28678 $ @kbd{gdb --annotate=3}
28680 Copyright 2003 Free Software Foundation, Inc.
28681 GDB is free software, covered by the GNU General Public License,
28682 and you are welcome to change it and/or distribute copies of it
28683 under certain conditions.
28684 Type "show copying" to see the conditions.
28685 There is absolutely no warranty for GDB. Type "show warranty"
28687 This GDB was configured as "i386-pc-linux-gnu"
28698 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28699 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28700 denotes a @samp{control-z} character) are annotations; the rest is
28701 output from @value{GDBN}.
28703 @node Server Prefix
28704 @section The Server Prefix
28705 @cindex server prefix
28707 If you prefix a command with @samp{server } then it will not affect
28708 the command history, nor will it affect @value{GDBN}'s notion of which
28709 command to repeat if @key{RET} is pressed on a line by itself. This
28710 means that commands can be run behind a user's back by a front-end in
28711 a transparent manner.
28713 The @code{server } prefix does not affect the recording of values into
28714 the value history; to print a value without recording it into the
28715 value history, use the @code{output} command instead of the
28716 @code{print} command.
28718 Using this prefix also disables confirmation requests
28719 (@pxref{confirmation requests}).
28722 @section Annotation for @value{GDBN} Input
28724 @cindex annotations for prompts
28725 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28726 to know when to send output, when the output from a given command is
28729 Different kinds of input each have a different @dfn{input type}. Each
28730 input type has three annotations: a @code{pre-} annotation, which
28731 denotes the beginning of any prompt which is being output, a plain
28732 annotation, which denotes the end of the prompt, and then a @code{post-}
28733 annotation which denotes the end of any echo which may (or may not) be
28734 associated with the input. For example, the @code{prompt} input type
28735 features the following annotations:
28743 The input types are
28746 @findex pre-prompt annotation
28747 @findex prompt annotation
28748 @findex post-prompt annotation
28750 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28752 @findex pre-commands annotation
28753 @findex commands annotation
28754 @findex post-commands annotation
28756 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28757 command. The annotations are repeated for each command which is input.
28759 @findex pre-overload-choice annotation
28760 @findex overload-choice annotation
28761 @findex post-overload-choice annotation
28762 @item overload-choice
28763 When @value{GDBN} wants the user to select between various overloaded functions.
28765 @findex pre-query annotation
28766 @findex query annotation
28767 @findex post-query annotation
28769 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28771 @findex pre-prompt-for-continue annotation
28772 @findex prompt-for-continue annotation
28773 @findex post-prompt-for-continue annotation
28774 @item prompt-for-continue
28775 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28776 expect this to work well; instead use @code{set height 0} to disable
28777 prompting. This is because the counting of lines is buggy in the
28778 presence of annotations.
28783 @cindex annotations for errors, warnings and interrupts
28785 @findex quit annotation
28790 This annotation occurs right before @value{GDBN} responds to an interrupt.
28792 @findex error annotation
28797 This annotation occurs right before @value{GDBN} responds to an error.
28799 Quit and error annotations indicate that any annotations which @value{GDBN} was
28800 in the middle of may end abruptly. For example, if a
28801 @code{value-history-begin} annotation is followed by a @code{error}, one
28802 cannot expect to receive the matching @code{value-history-end}. One
28803 cannot expect not to receive it either, however; an error annotation
28804 does not necessarily mean that @value{GDBN} is immediately returning all the way
28807 @findex error-begin annotation
28808 A quit or error annotation may be preceded by
28814 Any output between that and the quit or error annotation is the error
28817 Warning messages are not yet annotated.
28818 @c If we want to change that, need to fix warning(), type_error(),
28819 @c range_error(), and possibly other places.
28822 @section Invalidation Notices
28824 @cindex annotations for invalidation messages
28825 The following annotations say that certain pieces of state may have
28829 @findex frames-invalid annotation
28830 @item ^Z^Zframes-invalid
28832 The frames (for example, output from the @code{backtrace} command) may
28835 @findex breakpoints-invalid annotation
28836 @item ^Z^Zbreakpoints-invalid
28838 The breakpoints may have changed. For example, the user just added or
28839 deleted a breakpoint.
28842 @node Annotations for Running
28843 @section Running the Program
28844 @cindex annotations for running programs
28846 @findex starting annotation
28847 @findex stopping annotation
28848 When the program starts executing due to a @value{GDBN} command such as
28849 @code{step} or @code{continue},
28855 is output. When the program stops,
28861 is output. Before the @code{stopped} annotation, a variety of
28862 annotations describe how the program stopped.
28865 @findex exited annotation
28866 @item ^Z^Zexited @var{exit-status}
28867 The program exited, and @var{exit-status} is the exit status (zero for
28868 successful exit, otherwise nonzero).
28870 @findex signalled annotation
28871 @findex signal-name annotation
28872 @findex signal-name-end annotation
28873 @findex signal-string annotation
28874 @findex signal-string-end annotation
28875 @item ^Z^Zsignalled
28876 The program exited with a signal. After the @code{^Z^Zsignalled}, the
28877 annotation continues:
28883 ^Z^Zsignal-name-end
28887 ^Z^Zsignal-string-end
28892 where @var{name} is the name of the signal, such as @code{SIGILL} or
28893 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
28894 as @code{Illegal Instruction} or @code{Segmentation fault}.
28895 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
28896 user's benefit and have no particular format.
28898 @findex signal annotation
28900 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
28901 just saying that the program received the signal, not that it was
28902 terminated with it.
28904 @findex breakpoint annotation
28905 @item ^Z^Zbreakpoint @var{number}
28906 The program hit breakpoint number @var{number}.
28908 @findex watchpoint annotation
28909 @item ^Z^Zwatchpoint @var{number}
28910 The program hit watchpoint number @var{number}.
28913 @node Source Annotations
28914 @section Displaying Source
28915 @cindex annotations for source display
28917 @findex source annotation
28918 The following annotation is used instead of displaying source code:
28921 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
28924 where @var{filename} is an absolute file name indicating which source
28925 file, @var{line} is the line number within that file (where 1 is the
28926 first line in the file), @var{character} is the character position
28927 within the file (where 0 is the first character in the file) (for most
28928 debug formats this will necessarily point to the beginning of a line),
28929 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
28930 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
28931 @var{addr} is the address in the target program associated with the
28932 source which is being displayed. @var{addr} is in the form @samp{0x}
28933 followed by one or more lowercase hex digits (note that this does not
28934 depend on the language).
28936 @node JIT Interface
28937 @chapter JIT Compilation Interface
28938 @cindex just-in-time compilation
28939 @cindex JIT compilation interface
28941 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
28942 interface. A JIT compiler is a program or library that generates native
28943 executable code at runtime and executes it, usually in order to achieve good
28944 performance while maintaining platform independence.
28946 Programs that use JIT compilation are normally difficult to debug because
28947 portions of their code are generated at runtime, instead of being loaded from
28948 object files, which is where @value{GDBN} normally finds the program's symbols
28949 and debug information. In order to debug programs that use JIT compilation,
28950 @value{GDBN} has an interface that allows the program to register in-memory
28951 symbol files with @value{GDBN} at runtime.
28953 If you are using @value{GDBN} to debug a program that uses this interface, then
28954 it should work transparently so long as you have not stripped the binary. If
28955 you are developing a JIT compiler, then the interface is documented in the rest
28956 of this chapter. At this time, the only known client of this interface is the
28959 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28960 JIT compiler communicates with @value{GDBN} by writing data into a global
28961 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28962 attaches, it reads a linked list of symbol files from the global variable to
28963 find existing code, and puts a breakpoint in the function so that it can find
28964 out about additional code.
28967 * Declarations:: Relevant C struct declarations
28968 * Registering Code:: Steps to register code
28969 * Unregistering Code:: Steps to unregister code
28973 @section JIT Declarations
28975 These are the relevant struct declarations that a C program should include to
28976 implement the interface:
28986 struct jit_code_entry
28988 struct jit_code_entry *next_entry;
28989 struct jit_code_entry *prev_entry;
28990 const char *symfile_addr;
28991 uint64_t symfile_size;
28994 struct jit_descriptor
28997 /* This type should be jit_actions_t, but we use uint32_t
28998 to be explicit about the bitwidth. */
28999 uint32_t action_flag;
29000 struct jit_code_entry *relevant_entry;
29001 struct jit_code_entry *first_entry;
29004 /* GDB puts a breakpoint in this function. */
29005 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29007 /* Make sure to specify the version statically, because the
29008 debugger may check the version before we can set it. */
29009 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29012 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29013 modifications to this global data properly, which can easily be done by putting
29014 a global mutex around modifications to these structures.
29016 @node Registering Code
29017 @section Registering Code
29019 To register code with @value{GDBN}, the JIT should follow this protocol:
29023 Generate an object file in memory with symbols and other desired debug
29024 information. The file must include the virtual addresses of the sections.
29027 Create a code entry for the file, which gives the start and size of the symbol
29031 Add it to the linked list in the JIT descriptor.
29034 Point the relevant_entry field of the descriptor at the entry.
29037 Set @code{action_flag} to @code{JIT_REGISTER} and call
29038 @code{__jit_debug_register_code}.
29041 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29042 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29043 new code. However, the linked list must still be maintained in order to allow
29044 @value{GDBN} to attach to a running process and still find the symbol files.
29046 @node Unregistering Code
29047 @section Unregistering Code
29049 If code is freed, then the JIT should use the following protocol:
29053 Remove the code entry corresponding to the code from the linked list.
29056 Point the @code{relevant_entry} field of the descriptor at the code entry.
29059 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29060 @code{__jit_debug_register_code}.
29063 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29064 and the JIT will leak the memory used for the associated symbol files.
29067 @chapter Reporting Bugs in @value{GDBN}
29068 @cindex bugs in @value{GDBN}
29069 @cindex reporting bugs in @value{GDBN}
29071 Your bug reports play an essential role in making @value{GDBN} reliable.
29073 Reporting a bug may help you by bringing a solution to your problem, or it
29074 may not. But in any case the principal function of a bug report is to help
29075 the entire community by making the next version of @value{GDBN} work better. Bug
29076 reports are your contribution to the maintenance of @value{GDBN}.
29078 In order for a bug report to serve its purpose, you must include the
29079 information that enables us to fix the bug.
29082 * Bug Criteria:: Have you found a bug?
29083 * Bug Reporting:: How to report bugs
29087 @section Have You Found a Bug?
29088 @cindex bug criteria
29090 If you are not sure whether you have found a bug, here are some guidelines:
29093 @cindex fatal signal
29094 @cindex debugger crash
29095 @cindex crash of debugger
29097 If the debugger gets a fatal signal, for any input whatever, that is a
29098 @value{GDBN} bug. Reliable debuggers never crash.
29100 @cindex error on valid input
29102 If @value{GDBN} produces an error message for valid input, that is a
29103 bug. (Note that if you're cross debugging, the problem may also be
29104 somewhere in the connection to the target.)
29106 @cindex invalid input
29108 If @value{GDBN} does not produce an error message for invalid input,
29109 that is a bug. However, you should note that your idea of
29110 ``invalid input'' might be our idea of ``an extension'' or ``support
29111 for traditional practice''.
29114 If you are an experienced user of debugging tools, your suggestions
29115 for improvement of @value{GDBN} are welcome in any case.
29118 @node Bug Reporting
29119 @section How to Report Bugs
29120 @cindex bug reports
29121 @cindex @value{GDBN} bugs, reporting
29123 A number of companies and individuals offer support for @sc{gnu} products.
29124 If you obtained @value{GDBN} from a support organization, we recommend you
29125 contact that organization first.
29127 You can find contact information for many support companies and
29128 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29130 @c should add a web page ref...
29133 @ifset BUGURL_DEFAULT
29134 In any event, we also recommend that you submit bug reports for
29135 @value{GDBN}. The preferred method is to submit them directly using
29136 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29137 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29140 @strong{Do not send bug reports to @samp{info-gdb}, or to
29141 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29142 not want to receive bug reports. Those that do have arranged to receive
29145 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29146 serves as a repeater. The mailing list and the newsgroup carry exactly
29147 the same messages. Often people think of posting bug reports to the
29148 newsgroup instead of mailing them. This appears to work, but it has one
29149 problem which can be crucial: a newsgroup posting often lacks a mail
29150 path back to the sender. Thus, if we need to ask for more information,
29151 we may be unable to reach you. For this reason, it is better to send
29152 bug reports to the mailing list.
29154 @ifclear BUGURL_DEFAULT
29155 In any event, we also recommend that you submit bug reports for
29156 @value{GDBN} to @value{BUGURL}.
29160 The fundamental principle of reporting bugs usefully is this:
29161 @strong{report all the facts}. If you are not sure whether to state a
29162 fact or leave it out, state it!
29164 Often people omit facts because they think they know what causes the
29165 problem and assume that some details do not matter. Thus, you might
29166 assume that the name of the variable you use in an example does not matter.
29167 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29168 stray memory reference which happens to fetch from the location where that
29169 name is stored in memory; perhaps, if the name were different, the contents
29170 of that location would fool the debugger into doing the right thing despite
29171 the bug. Play it safe and give a specific, complete example. That is the
29172 easiest thing for you to do, and the most helpful.
29174 Keep in mind that the purpose of a bug report is to enable us to fix the
29175 bug. It may be that the bug has been reported previously, but neither
29176 you nor we can know that unless your bug report is complete and
29179 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29180 bell?'' Those bug reports are useless, and we urge everyone to
29181 @emph{refuse to respond to them} except to chide the sender to report
29184 To enable us to fix the bug, you should include all these things:
29188 The version of @value{GDBN}. @value{GDBN} announces it if you start
29189 with no arguments; you can also print it at any time using @code{show
29192 Without this, we will not know whether there is any point in looking for
29193 the bug in the current version of @value{GDBN}.
29196 The type of machine you are using, and the operating system name and
29200 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29201 ``@value{GCC}--2.8.1''.
29204 What compiler (and its version) was used to compile the program you are
29205 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29206 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29207 to get this information; for other compilers, see the documentation for
29211 The command arguments you gave the compiler to compile your example and
29212 observe the bug. For example, did you use @samp{-O}? To guarantee
29213 you will not omit something important, list them all. A copy of the
29214 Makefile (or the output from make) is sufficient.
29216 If we were to try to guess the arguments, we would probably guess wrong
29217 and then we might not encounter the bug.
29220 A complete input script, and all necessary source files, that will
29224 A description of what behavior you observe that you believe is
29225 incorrect. For example, ``It gets a fatal signal.''
29227 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29228 will certainly notice it. But if the bug is incorrect output, we might
29229 not notice unless it is glaringly wrong. You might as well not give us
29230 a chance to make a mistake.
29232 Even if the problem you experience is a fatal signal, you should still
29233 say so explicitly. Suppose something strange is going on, such as, your
29234 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29235 the C library on your system. (This has happened!) Your copy might
29236 crash and ours would not. If you told us to expect a crash, then when
29237 ours fails to crash, we would know that the bug was not happening for
29238 us. If you had not told us to expect a crash, then we would not be able
29239 to draw any conclusion from our observations.
29242 @cindex recording a session script
29243 To collect all this information, you can use a session recording program
29244 such as @command{script}, which is available on many Unix systems.
29245 Just run your @value{GDBN} session inside @command{script} and then
29246 include the @file{typescript} file with your bug report.
29248 Another way to record a @value{GDBN} session is to run @value{GDBN}
29249 inside Emacs and then save the entire buffer to a file.
29252 If you wish to suggest changes to the @value{GDBN} source, send us context
29253 diffs. If you even discuss something in the @value{GDBN} source, refer to
29254 it by context, not by line number.
29256 The line numbers in our development sources will not match those in your
29257 sources. Your line numbers would convey no useful information to us.
29261 Here are some things that are not necessary:
29265 A description of the envelope of the bug.
29267 Often people who encounter a bug spend a lot of time investigating
29268 which changes to the input file will make the bug go away and which
29269 changes will not affect it.
29271 This is often time consuming and not very useful, because the way we
29272 will find the bug is by running a single example under the debugger
29273 with breakpoints, not by pure deduction from a series of examples.
29274 We recommend that you save your time for something else.
29276 Of course, if you can find a simpler example to report @emph{instead}
29277 of the original one, that is a convenience for us. Errors in the
29278 output will be easier to spot, running under the debugger will take
29279 less time, and so on.
29281 However, simplification is not vital; if you do not want to do this,
29282 report the bug anyway and send us the entire test case you used.
29285 A patch for the bug.
29287 A patch for the bug does help us if it is a good one. But do not omit
29288 the necessary information, such as the test case, on the assumption that
29289 a patch is all we need. We might see problems with your patch and decide
29290 to fix the problem another way, or we might not understand it at all.
29292 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29293 construct an example that will make the program follow a certain path
29294 through the code. If you do not send us the example, we will not be able
29295 to construct one, so we will not be able to verify that the bug is fixed.
29297 And if we cannot understand what bug you are trying to fix, or why your
29298 patch should be an improvement, we will not install it. A test case will
29299 help us to understand.
29302 A guess about what the bug is or what it depends on.
29304 Such guesses are usually wrong. Even we cannot guess right about such
29305 things without first using the debugger to find the facts.
29308 @c The readline documentation is distributed with the readline code
29309 @c and consists of the two following files:
29311 @c inc-hist.texinfo
29312 @c Use -I with makeinfo to point to the appropriate directory,
29313 @c environment var TEXINPUTS with TeX.
29314 @include rluser.texi
29315 @include inc-hist.texinfo
29318 @node Formatting Documentation
29319 @appendix Formatting Documentation
29321 @cindex @value{GDBN} reference card
29322 @cindex reference card
29323 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29324 for printing with PostScript or Ghostscript, in the @file{gdb}
29325 subdirectory of the main source directory@footnote{In
29326 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29327 release.}. If you can use PostScript or Ghostscript with your printer,
29328 you can print the reference card immediately with @file{refcard.ps}.
29330 The release also includes the source for the reference card. You
29331 can format it, using @TeX{}, by typing:
29337 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29338 mode on US ``letter'' size paper;
29339 that is, on a sheet 11 inches wide by 8.5 inches
29340 high. You will need to specify this form of printing as an option to
29341 your @sc{dvi} output program.
29343 @cindex documentation
29345 All the documentation for @value{GDBN} comes as part of the machine-readable
29346 distribution. The documentation is written in Texinfo format, which is
29347 a documentation system that uses a single source file to produce both
29348 on-line information and a printed manual. You can use one of the Info
29349 formatting commands to create the on-line version of the documentation
29350 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29352 @value{GDBN} includes an already formatted copy of the on-line Info
29353 version of this manual in the @file{gdb} subdirectory. The main Info
29354 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29355 subordinate files matching @samp{gdb.info*} in the same directory. If
29356 necessary, you can print out these files, or read them with any editor;
29357 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29358 Emacs or the standalone @code{info} program, available as part of the
29359 @sc{gnu} Texinfo distribution.
29361 If you want to format these Info files yourself, you need one of the
29362 Info formatting programs, such as @code{texinfo-format-buffer} or
29365 If you have @code{makeinfo} installed, and are in the top level
29366 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29367 version @value{GDBVN}), you can make the Info file by typing:
29374 If you want to typeset and print copies of this manual, you need @TeX{},
29375 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29376 Texinfo definitions file.
29378 @TeX{} is a typesetting program; it does not print files directly, but
29379 produces output files called @sc{dvi} files. To print a typeset
29380 document, you need a program to print @sc{dvi} files. If your system
29381 has @TeX{} installed, chances are it has such a program. The precise
29382 command to use depends on your system; @kbd{lpr -d} is common; another
29383 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29384 require a file name without any extension or a @samp{.dvi} extension.
29386 @TeX{} also requires a macro definitions file called
29387 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29388 written in Texinfo format. On its own, @TeX{} cannot either read or
29389 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29390 and is located in the @file{gdb-@var{version-number}/texinfo}
29393 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29394 typeset and print this manual. First switch to the @file{gdb}
29395 subdirectory of the main source directory (for example, to
29396 @file{gdb-@value{GDBVN}/gdb}) and type:
29402 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29404 @node Installing GDB
29405 @appendix Installing @value{GDBN}
29406 @cindex installation
29409 * Requirements:: Requirements for building @value{GDBN}
29410 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29411 * Separate Objdir:: Compiling @value{GDBN} in another directory
29412 * Config Names:: Specifying names for hosts and targets
29413 * Configure Options:: Summary of options for configure
29414 * System-wide configuration:: Having a system-wide init file
29418 @section Requirements for Building @value{GDBN}
29419 @cindex building @value{GDBN}, requirements for
29421 Building @value{GDBN} requires various tools and packages to be available.
29422 Other packages will be used only if they are found.
29424 @heading Tools/Packages Necessary for Building @value{GDBN}
29426 @item ISO C90 compiler
29427 @value{GDBN} is written in ISO C90. It should be buildable with any
29428 working C90 compiler, e.g.@: GCC.
29432 @heading Tools/Packages Optional for Building @value{GDBN}
29436 @value{GDBN} can use the Expat XML parsing library. This library may be
29437 included with your operating system distribution; if it is not, you
29438 can get the latest version from @url{http://expat.sourceforge.net}.
29439 The @file{configure} script will search for this library in several
29440 standard locations; if it is installed in an unusual path, you can
29441 use the @option{--with-libexpat-prefix} option to specify its location.
29447 Remote protocol memory maps (@pxref{Memory Map Format})
29449 Target descriptions (@pxref{Target Descriptions})
29451 Remote shared library lists (@pxref{Library List Format})
29453 MS-Windows shared libraries (@pxref{Shared Libraries})
29457 @cindex compressed debug sections
29458 @value{GDBN} will use the @samp{zlib} library, if available, to read
29459 compressed debug sections. Some linkers, such as GNU gold, are capable
29460 of producing binaries with compressed debug sections. If @value{GDBN}
29461 is compiled with @samp{zlib}, it will be able to read the debug
29462 information in such binaries.
29464 The @samp{zlib} library is likely included with your operating system
29465 distribution; if it is not, you can get the latest version from
29466 @url{http://zlib.net}.
29469 @value{GDBN}'s features related to character sets (@pxref{Character
29470 Sets}) require a functioning @code{iconv} implementation. If you are
29471 on a GNU system, then this is provided by the GNU C Library. Some
29472 other systems also provide a working @code{iconv}.
29474 On systems with @code{iconv}, you can install GNU Libiconv. If you
29475 have previously installed Libiconv, you can use the
29476 @option{--with-libiconv-prefix} option to configure.
29478 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29479 arrange to build Libiconv if a directory named @file{libiconv} appears
29480 in the top-most source directory. If Libiconv is built this way, and
29481 if the operating system does not provide a suitable @code{iconv}
29482 implementation, then the just-built library will automatically be used
29483 by @value{GDBN}. One easy way to set this up is to download GNU
29484 Libiconv, unpack it, and then rename the directory holding the
29485 Libiconv source code to @samp{libiconv}.
29488 @node Running Configure
29489 @section Invoking the @value{GDBN} @file{configure} Script
29490 @cindex configuring @value{GDBN}
29491 @value{GDBN} comes with a @file{configure} script that automates the process
29492 of preparing @value{GDBN} for installation; you can then use @code{make} to
29493 build the @code{gdb} program.
29495 @c irrelevant in info file; it's as current as the code it lives with.
29496 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29497 look at the @file{README} file in the sources; we may have improved the
29498 installation procedures since publishing this manual.}
29501 The @value{GDBN} distribution includes all the source code you need for
29502 @value{GDBN} in a single directory, whose name is usually composed by
29503 appending the version number to @samp{gdb}.
29505 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29506 @file{gdb-@value{GDBVN}} directory. That directory contains:
29509 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29510 script for configuring @value{GDBN} and all its supporting libraries
29512 @item gdb-@value{GDBVN}/gdb
29513 the source specific to @value{GDBN} itself
29515 @item gdb-@value{GDBVN}/bfd
29516 source for the Binary File Descriptor library
29518 @item gdb-@value{GDBVN}/include
29519 @sc{gnu} include files
29521 @item gdb-@value{GDBVN}/libiberty
29522 source for the @samp{-liberty} free software library
29524 @item gdb-@value{GDBVN}/opcodes
29525 source for the library of opcode tables and disassemblers
29527 @item gdb-@value{GDBVN}/readline
29528 source for the @sc{gnu} command-line interface
29530 @item gdb-@value{GDBVN}/glob
29531 source for the @sc{gnu} filename pattern-matching subroutine
29533 @item gdb-@value{GDBVN}/mmalloc
29534 source for the @sc{gnu} memory-mapped malloc package
29537 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29538 from the @file{gdb-@var{version-number}} source directory, which in
29539 this example is the @file{gdb-@value{GDBVN}} directory.
29541 First switch to the @file{gdb-@var{version-number}} source directory
29542 if you are not already in it; then run @file{configure}. Pass the
29543 identifier for the platform on which @value{GDBN} will run as an
29549 cd gdb-@value{GDBVN}
29550 ./configure @var{host}
29555 where @var{host} is an identifier such as @samp{sun4} or
29556 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29557 (You can often leave off @var{host}; @file{configure} tries to guess the
29558 correct value by examining your system.)
29560 Running @samp{configure @var{host}} and then running @code{make} builds the
29561 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29562 libraries, then @code{gdb} itself. The configured source files, and the
29563 binaries, are left in the corresponding source directories.
29566 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29567 system does not recognize this automatically when you run a different
29568 shell, you may need to run @code{sh} on it explicitly:
29571 sh configure @var{host}
29574 If you run @file{configure} from a directory that contains source
29575 directories for multiple libraries or programs, such as the
29576 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29578 creates configuration files for every directory level underneath (unless
29579 you tell it not to, with the @samp{--norecursion} option).
29581 You should run the @file{configure} script from the top directory in the
29582 source tree, the @file{gdb-@var{version-number}} directory. If you run
29583 @file{configure} from one of the subdirectories, you will configure only
29584 that subdirectory. That is usually not what you want. In particular,
29585 if you run the first @file{configure} from the @file{gdb} subdirectory
29586 of the @file{gdb-@var{version-number}} directory, you will omit the
29587 configuration of @file{bfd}, @file{readline}, and other sibling
29588 directories of the @file{gdb} subdirectory. This leads to build errors
29589 about missing include files such as @file{bfd/bfd.h}.
29591 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29592 However, you should make sure that the shell on your path (named by
29593 the @samp{SHELL} environment variable) is publicly readable. Remember
29594 that @value{GDBN} uses the shell to start your program---some systems refuse to
29595 let @value{GDBN} debug child processes whose programs are not readable.
29597 @node Separate Objdir
29598 @section Compiling @value{GDBN} in Another Directory
29600 If you want to run @value{GDBN} versions for several host or target machines,
29601 you need a different @code{gdb} compiled for each combination of
29602 host and target. @file{configure} is designed to make this easy by
29603 allowing you to generate each configuration in a separate subdirectory,
29604 rather than in the source directory. If your @code{make} program
29605 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29606 @code{make} in each of these directories builds the @code{gdb}
29607 program specified there.
29609 To build @code{gdb} in a separate directory, run @file{configure}
29610 with the @samp{--srcdir} option to specify where to find the source.
29611 (You also need to specify a path to find @file{configure}
29612 itself from your working directory. If the path to @file{configure}
29613 would be the same as the argument to @samp{--srcdir}, you can leave out
29614 the @samp{--srcdir} option; it is assumed.)
29616 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29617 separate directory for a Sun 4 like this:
29621 cd gdb-@value{GDBVN}
29624 ../gdb-@value{GDBVN}/configure sun4
29629 When @file{configure} builds a configuration using a remote source
29630 directory, it creates a tree for the binaries with the same structure
29631 (and using the same names) as the tree under the source directory. In
29632 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29633 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29634 @file{gdb-sun4/gdb}.
29636 Make sure that your path to the @file{configure} script has just one
29637 instance of @file{gdb} in it. If your path to @file{configure} looks
29638 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29639 one subdirectory of @value{GDBN}, not the whole package. This leads to
29640 build errors about missing include files such as @file{bfd/bfd.h}.
29642 One popular reason to build several @value{GDBN} configurations in separate
29643 directories is to configure @value{GDBN} for cross-compiling (where
29644 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
29645 programs that run on another machine---the @dfn{target}).
29646 You specify a cross-debugging target by
29647 giving the @samp{--target=@var{target}} option to @file{configure}.
29649 When you run @code{make} to build a program or library, you must run
29650 it in a configured directory---whatever directory you were in when you
29651 called @file{configure} (or one of its subdirectories).
29653 The @code{Makefile} that @file{configure} generates in each source
29654 directory also runs recursively. If you type @code{make} in a source
29655 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29656 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29657 will build all the required libraries, and then build GDB.
29659 When you have multiple hosts or targets configured in separate
29660 directories, you can run @code{make} on them in parallel (for example,
29661 if they are NFS-mounted on each of the hosts); they will not interfere
29665 @section Specifying Names for Hosts and Targets
29667 The specifications used for hosts and targets in the @file{configure}
29668 script are based on a three-part naming scheme, but some short predefined
29669 aliases are also supported. The full naming scheme encodes three pieces
29670 of information in the following pattern:
29673 @var{architecture}-@var{vendor}-@var{os}
29676 For example, you can use the alias @code{sun4} as a @var{host} argument,
29677 or as the value for @var{target} in a @code{--target=@var{target}}
29678 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29680 The @file{configure} script accompanying @value{GDBN} does not provide
29681 any query facility to list all supported host and target names or
29682 aliases. @file{configure} calls the Bourne shell script
29683 @code{config.sub} to map abbreviations to full names; you can read the
29684 script, if you wish, or you can use it to test your guesses on
29685 abbreviations---for example:
29688 % sh config.sub i386-linux
29690 % sh config.sub alpha-linux
29691 alpha-unknown-linux-gnu
29692 % sh config.sub hp9k700
29694 % sh config.sub sun4
29695 sparc-sun-sunos4.1.1
29696 % sh config.sub sun3
29697 m68k-sun-sunos4.1.1
29698 % sh config.sub i986v
29699 Invalid configuration `i986v': machine `i986v' not recognized
29703 @code{config.sub} is also distributed in the @value{GDBN} source
29704 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29706 @node Configure Options
29707 @section @file{configure} Options
29709 Here is a summary of the @file{configure} options and arguments that
29710 are most often useful for building @value{GDBN}. @file{configure} also has
29711 several other options not listed here. @inforef{What Configure
29712 Does,,configure.info}, for a full explanation of @file{configure}.
29715 configure @r{[}--help@r{]}
29716 @r{[}--prefix=@var{dir}@r{]}
29717 @r{[}--exec-prefix=@var{dir}@r{]}
29718 @r{[}--srcdir=@var{dirname}@r{]}
29719 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29720 @r{[}--target=@var{target}@r{]}
29725 You may introduce options with a single @samp{-} rather than
29726 @samp{--} if you prefer; but you may abbreviate option names if you use
29731 Display a quick summary of how to invoke @file{configure}.
29733 @item --prefix=@var{dir}
29734 Configure the source to install programs and files under directory
29737 @item --exec-prefix=@var{dir}
29738 Configure the source to install programs under directory
29741 @c avoid splitting the warning from the explanation:
29743 @item --srcdir=@var{dirname}
29744 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29745 @code{make} that implements the @code{VPATH} feature.}@*
29746 Use this option to make configurations in directories separate from the
29747 @value{GDBN} source directories. Among other things, you can use this to
29748 build (or maintain) several configurations simultaneously, in separate
29749 directories. @file{configure} writes configuration-specific files in
29750 the current directory, but arranges for them to use the source in the
29751 directory @var{dirname}. @file{configure} creates directories under
29752 the working directory in parallel to the source directories below
29755 @item --norecursion
29756 Configure only the directory level where @file{configure} is executed; do not
29757 propagate configuration to subdirectories.
29759 @item --target=@var{target}
29760 Configure @value{GDBN} for cross-debugging programs running on the specified
29761 @var{target}. Without this option, @value{GDBN} is configured to debug
29762 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29764 There is no convenient way to generate a list of all available targets.
29766 @item @var{host} @dots{}
29767 Configure @value{GDBN} to run on the specified @var{host}.
29769 There is no convenient way to generate a list of all available hosts.
29772 There are many other options available as well, but they are generally
29773 needed for special purposes only.
29775 @node System-wide configuration
29776 @section System-wide configuration and settings
29777 @cindex system-wide init file
29779 @value{GDBN} can be configured to have a system-wide init file;
29780 this file will be read and executed at startup (@pxref{Startup, , What
29781 @value{GDBN} does during startup}).
29783 Here is the corresponding configure option:
29786 @item --with-system-gdbinit=@var{file}
29787 Specify that the default location of the system-wide init file is
29791 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29792 it may be subject to relocation. Two possible cases:
29796 If the default location of this init file contains @file{$prefix},
29797 it will be subject to relocation. Suppose that the configure options
29798 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29799 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29800 init file is looked for as @file{$install/etc/gdbinit} instead of
29801 @file{$prefix/etc/gdbinit}.
29804 By contrast, if the default location does not contain the prefix,
29805 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29806 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29807 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29808 wherever @value{GDBN} is installed.
29811 @node Maintenance Commands
29812 @appendix Maintenance Commands
29813 @cindex maintenance commands
29814 @cindex internal commands
29816 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29817 includes a number of commands intended for @value{GDBN} developers,
29818 that are not documented elsewhere in this manual. These commands are
29819 provided here for reference. (For commands that turn on debugging
29820 messages, see @ref{Debugging Output}.)
29823 @kindex maint agent
29824 @kindex maint agent-eval
29825 @item maint agent @var{expression}
29826 @itemx maint agent-eval @var{expression}
29827 Translate the given @var{expression} into remote agent bytecodes.
29828 This command is useful for debugging the Agent Expression mechanism
29829 (@pxref{Agent Expressions}). The @samp{agent} version produces an
29830 expression useful for data collection, such as by tracepoints, while
29831 @samp{maint agent-eval} produces an expression that evaluates directly
29832 to a result. For instance, a collection expression for @code{globa +
29833 globb} will include bytecodes to record four bytes of memory at each
29834 of the addresses of @code{globa} and @code{globb}, while discarding
29835 the result of the addition, while an evaluation expression will do the
29836 addition and return the sum.
29838 @kindex maint info breakpoints
29839 @item @anchor{maint info breakpoints}maint info breakpoints
29840 Using the same format as @samp{info breakpoints}, display both the
29841 breakpoints you've set explicitly, and those @value{GDBN} is using for
29842 internal purposes. Internal breakpoints are shown with negative
29843 breakpoint numbers. The type column identifies what kind of breakpoint
29848 Normal, explicitly set breakpoint.
29851 Normal, explicitly set watchpoint.
29854 Internal breakpoint, used to handle correctly stepping through
29855 @code{longjmp} calls.
29857 @item longjmp resume
29858 Internal breakpoint at the target of a @code{longjmp}.
29861 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
29864 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
29867 Shared library events.
29871 @kindex set displaced-stepping
29872 @kindex show displaced-stepping
29873 @cindex displaced stepping support
29874 @cindex out-of-line single-stepping
29875 @item set displaced-stepping
29876 @itemx show displaced-stepping
29877 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
29878 if the target supports it. Displaced stepping is a way to single-step
29879 over breakpoints without removing them from the inferior, by executing
29880 an out-of-line copy of the instruction that was originally at the
29881 breakpoint location. It is also known as out-of-line single-stepping.
29884 @item set displaced-stepping on
29885 If the target architecture supports it, @value{GDBN} will use
29886 displaced stepping to step over breakpoints.
29888 @item set displaced-stepping off
29889 @value{GDBN} will not use displaced stepping to step over breakpoints,
29890 even if such is supported by the target architecture.
29892 @cindex non-stop mode, and @samp{set displaced-stepping}
29893 @item set displaced-stepping auto
29894 This is the default mode. @value{GDBN} will use displaced stepping
29895 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
29896 architecture supports displaced stepping.
29899 @kindex maint check-symtabs
29900 @item maint check-symtabs
29901 Check the consistency of psymtabs and symtabs.
29903 @kindex maint cplus first_component
29904 @item maint cplus first_component @var{name}
29905 Print the first C@t{++} class/namespace component of @var{name}.
29907 @kindex maint cplus namespace
29908 @item maint cplus namespace
29909 Print the list of possible C@t{++} namespaces.
29911 @kindex maint demangle
29912 @item maint demangle @var{name}
29913 Demangle a C@t{++} or Objective-C mangled @var{name}.
29915 @kindex maint deprecate
29916 @kindex maint undeprecate
29917 @cindex deprecated commands
29918 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
29919 @itemx maint undeprecate @var{command}
29920 Deprecate or undeprecate the named @var{command}. Deprecated commands
29921 cause @value{GDBN} to issue a warning when you use them. The optional
29922 argument @var{replacement} says which newer command should be used in
29923 favor of the deprecated one; if it is given, @value{GDBN} will mention
29924 the replacement as part of the warning.
29926 @kindex maint dump-me
29927 @item maint dump-me
29928 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
29929 Cause a fatal signal in the debugger and force it to dump its core.
29930 This is supported only on systems which support aborting a program
29931 with the @code{SIGQUIT} signal.
29933 @kindex maint internal-error
29934 @kindex maint internal-warning
29935 @item maint internal-error @r{[}@var{message-text}@r{]}
29936 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
29937 Cause @value{GDBN} to call the internal function @code{internal_error}
29938 or @code{internal_warning} and hence behave as though an internal error
29939 or internal warning has been detected. In addition to reporting the
29940 internal problem, these functions give the user the opportunity to
29941 either quit @value{GDBN} or create a core file of the current
29942 @value{GDBN} session.
29944 These commands take an optional parameter @var{message-text} that is
29945 used as the text of the error or warning message.
29947 Here's an example of using @code{internal-error}:
29950 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
29951 @dots{}/maint.c:121: internal-error: testing, 1, 2
29952 A problem internal to GDB has been detected. Further
29953 debugging may prove unreliable.
29954 Quit this debugging session? (y or n) @kbd{n}
29955 Create a core file? (y or n) @kbd{n}
29959 @cindex @value{GDBN} internal error
29960 @cindex internal errors, control of @value{GDBN} behavior
29962 @kindex maint set internal-error
29963 @kindex maint show internal-error
29964 @kindex maint set internal-warning
29965 @kindex maint show internal-warning
29966 @item maint set internal-error @var{action} [ask|yes|no]
29967 @itemx maint show internal-error @var{action}
29968 @itemx maint set internal-warning @var{action} [ask|yes|no]
29969 @itemx maint show internal-warning @var{action}
29970 When @value{GDBN} reports an internal problem (error or warning) it
29971 gives the user the opportunity to both quit @value{GDBN} and create a
29972 core file of the current @value{GDBN} session. These commands let you
29973 override the default behaviour for each particular @var{action},
29974 described in the table below.
29978 You can specify that @value{GDBN} should always (yes) or never (no)
29979 quit. The default is to ask the user what to do.
29982 You can specify that @value{GDBN} should always (yes) or never (no)
29983 create a core file. The default is to ask the user what to do.
29986 @kindex maint packet
29987 @item maint packet @var{text}
29988 If @value{GDBN} is talking to an inferior via the serial protocol,
29989 then this command sends the string @var{text} to the inferior, and
29990 displays the response packet. @value{GDBN} supplies the initial
29991 @samp{$} character, the terminating @samp{#} character, and the
29994 @kindex maint print architecture
29995 @item maint print architecture @r{[}@var{file}@r{]}
29996 Print the entire architecture configuration. The optional argument
29997 @var{file} names the file where the output goes.
29999 @kindex maint print c-tdesc
30000 @item maint print c-tdesc
30001 Print the current target description (@pxref{Target Descriptions}) as
30002 a C source file. The created source file can be used in @value{GDBN}
30003 when an XML parser is not available to parse the description.
30005 @kindex maint print dummy-frames
30006 @item maint print dummy-frames
30007 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30010 (@value{GDBP}) @kbd{b add}
30012 (@value{GDBP}) @kbd{print add(2,3)}
30013 Breakpoint 2, add (a=2, b=3) at @dots{}
30015 The program being debugged stopped while in a function called from GDB.
30017 (@value{GDBP}) @kbd{maint print dummy-frames}
30018 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30019 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30020 call_lo=0x01014000 call_hi=0x01014001
30024 Takes an optional file parameter.
30026 @kindex maint print registers
30027 @kindex maint print raw-registers
30028 @kindex maint print cooked-registers
30029 @kindex maint print register-groups
30030 @item maint print registers @r{[}@var{file}@r{]}
30031 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30032 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30033 @itemx maint print register-groups @r{[}@var{file}@r{]}
30034 Print @value{GDBN}'s internal register data structures.
30036 The command @code{maint print raw-registers} includes the contents of
30037 the raw register cache; the command @code{maint print cooked-registers}
30038 includes the (cooked) value of all registers, including registers which
30039 aren't available on the target nor visible to user; and the
30040 command @code{maint print register-groups} includes the groups that each
30041 register is a member of. @xref{Registers,, Registers, gdbint,
30042 @value{GDBN} Internals}.
30044 These commands take an optional parameter, a file name to which to
30045 write the information.
30047 @kindex maint print reggroups
30048 @item maint print reggroups @r{[}@var{file}@r{]}
30049 Print @value{GDBN}'s internal register group data structures. The
30050 optional argument @var{file} tells to what file to write the
30053 The register groups info looks like this:
30056 (@value{GDBP}) @kbd{maint print reggroups}
30069 This command forces @value{GDBN} to flush its internal register cache.
30071 @kindex maint print objfiles
30072 @cindex info for known object files
30073 @item maint print objfiles
30074 Print a dump of all known object files. For each object file, this
30075 command prints its name, address in memory, and all of its psymtabs
30078 @kindex maint print section-scripts
30079 @cindex info for known .debug_gdb_scripts-loaded scripts
30080 @item maint print section-scripts [@var{regexp}]
30081 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30082 If @var{regexp} is specified, only print scripts loaded by object files
30083 matching @var{regexp}.
30084 For each script, this command prints its name as specified in the objfile,
30085 and the full path if known.
30086 @xref{.debug_gdb_scripts section}.
30088 @kindex maint print statistics
30089 @cindex bcache statistics
30090 @item maint print statistics
30091 This command prints, for each object file in the program, various data
30092 about that object file followed by the byte cache (@dfn{bcache})
30093 statistics for the object file. The objfile data includes the number
30094 of minimal, partial, full, and stabs symbols, the number of types
30095 defined by the objfile, the number of as yet unexpanded psym tables,
30096 the number of line tables and string tables, and the amount of memory
30097 used by the various tables. The bcache statistics include the counts,
30098 sizes, and counts of duplicates of all and unique objects, max,
30099 average, and median entry size, total memory used and its overhead and
30100 savings, and various measures of the hash table size and chain
30103 @kindex maint print target-stack
30104 @cindex target stack description
30105 @item maint print target-stack
30106 A @dfn{target} is an interface between the debugger and a particular
30107 kind of file or process. Targets can be stacked in @dfn{strata},
30108 so that more than one target can potentially respond to a request.
30109 In particular, memory accesses will walk down the stack of targets
30110 until they find a target that is interested in handling that particular
30113 This command prints a short description of each layer that was pushed on
30114 the @dfn{target stack}, starting from the top layer down to the bottom one.
30116 @kindex maint print type
30117 @cindex type chain of a data type
30118 @item maint print type @var{expr}
30119 Print the type chain for a type specified by @var{expr}. The argument
30120 can be either a type name or a symbol. If it is a symbol, the type of
30121 that symbol is described. The type chain produced by this command is
30122 a recursive definition of the data type as stored in @value{GDBN}'s
30123 data structures, including its flags and contained types.
30125 @kindex maint set dwarf2 always-disassemble
30126 @kindex maint show dwarf2 always-disassemble
30127 @item maint set dwarf2 always-disassemble
30128 @item maint show dwarf2 always-disassemble
30129 Control the behavior of @code{info address} when using DWARF debugging
30132 The default is @code{off}, which means that @value{GDBN} should try to
30133 describe a variable's location in an easily readable format. When
30134 @code{on}, @value{GDBN} will instead display the DWARF location
30135 expression in an assembly-like format. Note that some locations are
30136 too complex for @value{GDBN} to describe simply; in this case you will
30137 always see the disassembly form.
30139 Here is an example of the resulting disassembly:
30142 (gdb) info addr argc
30143 Symbol "argc" is a complex DWARF expression:
30147 For more information on these expressions, see
30148 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30150 @kindex maint set dwarf2 max-cache-age
30151 @kindex maint show dwarf2 max-cache-age
30152 @item maint set dwarf2 max-cache-age
30153 @itemx maint show dwarf2 max-cache-age
30154 Control the DWARF 2 compilation unit cache.
30156 @cindex DWARF 2 compilation units cache
30157 In object files with inter-compilation-unit references, such as those
30158 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30159 reader needs to frequently refer to previously read compilation units.
30160 This setting controls how long a compilation unit will remain in the
30161 cache if it is not referenced. A higher limit means that cached
30162 compilation units will be stored in memory longer, and more total
30163 memory will be used. Setting it to zero disables caching, which will
30164 slow down @value{GDBN} startup, but reduce memory consumption.
30166 @kindex maint set profile
30167 @kindex maint show profile
30168 @cindex profiling GDB
30169 @item maint set profile
30170 @itemx maint show profile
30171 Control profiling of @value{GDBN}.
30173 Profiling will be disabled until you use the @samp{maint set profile}
30174 command to enable it. When you enable profiling, the system will begin
30175 collecting timing and execution count data; when you disable profiling or
30176 exit @value{GDBN}, the results will be written to a log file. Remember that
30177 if you use profiling, @value{GDBN} will overwrite the profiling log file
30178 (often called @file{gmon.out}). If you have a record of important profiling
30179 data in a @file{gmon.out} file, be sure to move it to a safe location.
30181 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30182 compiled with the @samp{-pg} compiler option.
30184 @kindex maint set show-debug-regs
30185 @kindex maint show show-debug-regs
30186 @cindex hardware debug registers
30187 @item maint set show-debug-regs
30188 @itemx maint show show-debug-regs
30189 Control whether to show variables that mirror the hardware debug
30190 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30191 enabled, the debug registers values are shown when @value{GDBN} inserts or
30192 removes a hardware breakpoint or watchpoint, and when the inferior
30193 triggers a hardware-assisted breakpoint or watchpoint.
30195 @kindex maint set show-all-tib
30196 @kindex maint show show-all-tib
30197 @item maint set show-all-tib
30198 @itemx maint show show-all-tib
30199 Control whether to show all non zero areas within a 1k block starting
30200 at thread local base, when using the @samp{info w32 thread-information-block}
30203 @kindex maint space
30204 @cindex memory used by commands
30206 Control whether to display memory usage for each command. If set to a
30207 nonzero value, @value{GDBN} will display how much memory each command
30208 took, following the command's own output. This can also be requested
30209 by invoking @value{GDBN} with the @option{--statistics} command-line
30210 switch (@pxref{Mode Options}).
30213 @cindex time of command execution
30215 Control whether to display the execution time for each command. If
30216 set to a nonzero value, @value{GDBN} will display how much time it
30217 took to execute each command, following the command's own output.
30218 The time is not printed for the commands that run the target, since
30219 there's no mechanism currently to compute how much time was spend
30220 by @value{GDBN} and how much time was spend by the program been debugged.
30221 it's not possibly currently
30222 This can also be requested by invoking @value{GDBN} with the
30223 @option{--statistics} command-line switch (@pxref{Mode Options}).
30225 @kindex maint translate-address
30226 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30227 Find the symbol stored at the location specified by the address
30228 @var{addr} and an optional section name @var{section}. If found,
30229 @value{GDBN} prints the name of the closest symbol and an offset from
30230 the symbol's location to the specified address. This is similar to
30231 the @code{info address} command (@pxref{Symbols}), except that this
30232 command also allows to find symbols in other sections.
30234 If section was not specified, the section in which the symbol was found
30235 is also printed. For dynamically linked executables, the name of
30236 executable or shared library containing the symbol is printed as well.
30240 The following command is useful for non-interactive invocations of
30241 @value{GDBN}, such as in the test suite.
30244 @item set watchdog @var{nsec}
30245 @kindex set watchdog
30246 @cindex watchdog timer
30247 @cindex timeout for commands
30248 Set the maximum number of seconds @value{GDBN} will wait for the
30249 target operation to finish. If this time expires, @value{GDBN}
30250 reports and error and the command is aborted.
30252 @item show watchdog
30253 Show the current setting of the target wait timeout.
30256 @node Remote Protocol
30257 @appendix @value{GDBN} Remote Serial Protocol
30262 * Stop Reply Packets::
30263 * General Query Packets::
30264 * Architecture-Specific Protocol Details::
30265 * Tracepoint Packets::
30266 * Host I/O Packets::
30268 * Notification Packets::
30269 * Remote Non-Stop::
30270 * Packet Acknowledgment::
30272 * File-I/O Remote Protocol Extension::
30273 * Library List Format::
30274 * Memory Map Format::
30275 * Thread List Format::
30281 There may be occasions when you need to know something about the
30282 protocol---for example, if there is only one serial port to your target
30283 machine, you might want your program to do something special if it
30284 recognizes a packet meant for @value{GDBN}.
30286 In the examples below, @samp{->} and @samp{<-} are used to indicate
30287 transmitted and received data, respectively.
30289 @cindex protocol, @value{GDBN} remote serial
30290 @cindex serial protocol, @value{GDBN} remote
30291 @cindex remote serial protocol
30292 All @value{GDBN} commands and responses (other than acknowledgments
30293 and notifications, see @ref{Notification Packets}) are sent as a
30294 @var{packet}. A @var{packet} is introduced with the character
30295 @samp{$}, the actual @var{packet-data}, and the terminating character
30296 @samp{#} followed by a two-digit @var{checksum}:
30299 @code{$}@var{packet-data}@code{#}@var{checksum}
30303 @cindex checksum, for @value{GDBN} remote
30305 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30306 characters between the leading @samp{$} and the trailing @samp{#} (an
30307 eight bit unsigned checksum).
30309 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30310 specification also included an optional two-digit @var{sequence-id}:
30313 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30316 @cindex sequence-id, for @value{GDBN} remote
30318 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30319 has never output @var{sequence-id}s. Stubs that handle packets added
30320 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30322 When either the host or the target machine receives a packet, the first
30323 response expected is an acknowledgment: either @samp{+} (to indicate
30324 the package was received correctly) or @samp{-} (to request
30328 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30333 The @samp{+}/@samp{-} acknowledgments can be disabled
30334 once a connection is established.
30335 @xref{Packet Acknowledgment}, for details.
30337 The host (@value{GDBN}) sends @var{command}s, and the target (the
30338 debugging stub incorporated in your program) sends a @var{response}. In
30339 the case of step and continue @var{command}s, the response is only sent
30340 when the operation has completed, and the target has again stopped all
30341 threads in all attached processes. This is the default all-stop mode
30342 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30343 execution mode; see @ref{Remote Non-Stop}, for details.
30345 @var{packet-data} consists of a sequence of characters with the
30346 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30349 @cindex remote protocol, field separator
30350 Fields within the packet should be separated using @samp{,} @samp{;} or
30351 @samp{:}. Except where otherwise noted all numbers are represented in
30352 @sc{hex} with leading zeros suppressed.
30354 Implementors should note that prior to @value{GDBN} 5.0, the character
30355 @samp{:} could not appear as the third character in a packet (as it
30356 would potentially conflict with the @var{sequence-id}).
30358 @cindex remote protocol, binary data
30359 @anchor{Binary Data}
30360 Binary data in most packets is encoded either as two hexadecimal
30361 digits per byte of binary data. This allowed the traditional remote
30362 protocol to work over connections which were only seven-bit clean.
30363 Some packets designed more recently assume an eight-bit clean
30364 connection, and use a more efficient encoding to send and receive
30367 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30368 as an escape character. Any escaped byte is transmitted as the escape
30369 character followed by the original character XORed with @code{0x20}.
30370 For example, the byte @code{0x7d} would be transmitted as the two
30371 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30372 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30373 @samp{@}}) must always be escaped. Responses sent by the stub
30374 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30375 is not interpreted as the start of a run-length encoded sequence
30378 Response @var{data} can be run-length encoded to save space.
30379 Run-length encoding replaces runs of identical characters with one
30380 instance of the repeated character, followed by a @samp{*} and a
30381 repeat count. The repeat count is itself sent encoded, to avoid
30382 binary characters in @var{data}: a value of @var{n} is sent as
30383 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30384 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30385 code 32) for a repeat count of 3. (This is because run-length
30386 encoding starts to win for counts 3 or more.) Thus, for example,
30387 @samp{0* } is a run-length encoding of ``0000'': the space character
30388 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30391 The printable characters @samp{#} and @samp{$} or with a numeric value
30392 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30393 seven repeats (@samp{$}) can be expanded using a repeat count of only
30394 five (@samp{"}). For example, @samp{00000000} can be encoded as
30397 The error response returned for some packets includes a two character
30398 error number. That number is not well defined.
30400 @cindex empty response, for unsupported packets
30401 For any @var{command} not supported by the stub, an empty response
30402 (@samp{$#00}) should be returned. That way it is possible to extend the
30403 protocol. A newer @value{GDBN} can tell if a packet is supported based
30406 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30407 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30413 The following table provides a complete list of all currently defined
30414 @var{command}s and their corresponding response @var{data}.
30415 @xref{File-I/O Remote Protocol Extension}, for details about the File
30416 I/O extension of the remote protocol.
30418 Each packet's description has a template showing the packet's overall
30419 syntax, followed by an explanation of the packet's meaning. We
30420 include spaces in some of the templates for clarity; these are not
30421 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30422 separate its components. For example, a template like @samp{foo
30423 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30424 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30425 @var{baz}. @value{GDBN} does not transmit a space character between the
30426 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30429 @cindex @var{thread-id}, in remote protocol
30430 @anchor{thread-id syntax}
30431 Several packets and replies include a @var{thread-id} field to identify
30432 a thread. Normally these are positive numbers with a target-specific
30433 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30434 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30437 In addition, the remote protocol supports a multiprocess feature in
30438 which the @var{thread-id} syntax is extended to optionally include both
30439 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30440 The @var{pid} (process) and @var{tid} (thread) components each have the
30441 format described above: a positive number with target-specific
30442 interpretation formatted as a big-endian hex string, literal @samp{-1}
30443 to indicate all processes or threads (respectively), or @samp{0} to
30444 indicate an arbitrary process or thread. Specifying just a process, as
30445 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30446 error to specify all processes but a specific thread, such as
30447 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30448 for those packets and replies explicitly documented to include a process
30449 ID, rather than a @var{thread-id}.
30451 The multiprocess @var{thread-id} syntax extensions are only used if both
30452 @value{GDBN} and the stub report support for the @samp{multiprocess}
30453 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30456 Note that all packet forms beginning with an upper- or lower-case
30457 letter, other than those described here, are reserved for future use.
30459 Here are the packet descriptions.
30464 @cindex @samp{!} packet
30465 @anchor{extended mode}
30466 Enable extended mode. In extended mode, the remote server is made
30467 persistent. The @samp{R} packet is used to restart the program being
30473 The remote target both supports and has enabled extended mode.
30477 @cindex @samp{?} packet
30478 Indicate the reason the target halted. The reply is the same as for
30479 step and continue. This packet has a special interpretation when the
30480 target is in non-stop mode; see @ref{Remote Non-Stop}.
30483 @xref{Stop Reply Packets}, for the reply specifications.
30485 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30486 @cindex @samp{A} packet
30487 Initialized @code{argv[]} array passed into program. @var{arglen}
30488 specifies the number of bytes in the hex encoded byte stream
30489 @var{arg}. See @code{gdbserver} for more details.
30494 The arguments were set.
30500 @cindex @samp{b} packet
30501 (Don't use this packet; its behavior is not well-defined.)
30502 Change the serial line speed to @var{baud}.
30504 JTC: @emph{When does the transport layer state change? When it's
30505 received, or after the ACK is transmitted. In either case, there are
30506 problems if the command or the acknowledgment packet is dropped.}
30508 Stan: @emph{If people really wanted to add something like this, and get
30509 it working for the first time, they ought to modify ser-unix.c to send
30510 some kind of out-of-band message to a specially-setup stub and have the
30511 switch happen "in between" packets, so that from remote protocol's point
30512 of view, nothing actually happened.}
30514 @item B @var{addr},@var{mode}
30515 @cindex @samp{B} packet
30516 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30517 breakpoint at @var{addr}.
30519 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30520 (@pxref{insert breakpoint or watchpoint packet}).
30522 @cindex @samp{bc} packet
30525 Backward continue. Execute the target system in reverse. No parameter.
30526 @xref{Reverse Execution}, for more information.
30529 @xref{Stop Reply Packets}, for the reply specifications.
30531 @cindex @samp{bs} packet
30534 Backward single step. Execute one instruction in reverse. No parameter.
30535 @xref{Reverse Execution}, for more information.
30538 @xref{Stop Reply Packets}, for the reply specifications.
30540 @item c @r{[}@var{addr}@r{]}
30541 @cindex @samp{c} packet
30542 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30543 resume at current address.
30546 @xref{Stop Reply Packets}, for the reply specifications.
30548 @item C @var{sig}@r{[};@var{addr}@r{]}
30549 @cindex @samp{C} packet
30550 Continue with signal @var{sig} (hex signal number). If
30551 @samp{;@var{addr}} is omitted, resume at same address.
30554 @xref{Stop Reply Packets}, for the reply specifications.
30557 @cindex @samp{d} packet
30560 Don't use this packet; instead, define a general set packet
30561 (@pxref{General Query Packets}).
30565 @cindex @samp{D} packet
30566 The first form of the packet is used to detach @value{GDBN} from the
30567 remote system. It is sent to the remote target
30568 before @value{GDBN} disconnects via the @code{detach} command.
30570 The second form, including a process ID, is used when multiprocess
30571 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30572 detach only a specific process. The @var{pid} is specified as a
30573 big-endian hex string.
30583 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30584 @cindex @samp{F} packet
30585 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30586 This is part of the File-I/O protocol extension. @xref{File-I/O
30587 Remote Protocol Extension}, for the specification.
30590 @anchor{read registers packet}
30591 @cindex @samp{g} packet
30592 Read general registers.
30596 @item @var{XX@dots{}}
30597 Each byte of register data is described by two hex digits. The bytes
30598 with the register are transmitted in target byte order. The size of
30599 each register and their position within the @samp{g} packet are
30600 determined by the @value{GDBN} internal gdbarch functions
30601 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30602 specification of several standard @samp{g} packets is specified below.
30607 @item G @var{XX@dots{}}
30608 @cindex @samp{G} packet
30609 Write general registers. @xref{read registers packet}, for a
30610 description of the @var{XX@dots{}} data.
30620 @item H @var{c} @var{thread-id}
30621 @cindex @samp{H} packet
30622 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30623 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30624 should be @samp{c} for step and continue operations, @samp{g} for other
30625 operations. The thread designator @var{thread-id} has the format and
30626 interpretation described in @ref{thread-id syntax}.
30637 @c 'H': How restrictive (or permissive) is the thread model. If a
30638 @c thread is selected and stopped, are other threads allowed
30639 @c to continue to execute? As I mentioned above, I think the
30640 @c semantics of each command when a thread is selected must be
30641 @c described. For example:
30643 @c 'g': If the stub supports threads and a specific thread is
30644 @c selected, returns the register block from that thread;
30645 @c otherwise returns current registers.
30647 @c 'G' If the stub supports threads and a specific thread is
30648 @c selected, sets the registers of the register block of
30649 @c that thread; otherwise sets current registers.
30651 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
30652 @anchor{cycle step packet}
30653 @cindex @samp{i} packet
30654 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
30655 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
30656 step starting at that address.
30659 @cindex @samp{I} packet
30660 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
30664 @cindex @samp{k} packet
30667 FIXME: @emph{There is no description of how to operate when a specific
30668 thread context has been selected (i.e.@: does 'k' kill only that
30671 @item m @var{addr},@var{length}
30672 @cindex @samp{m} packet
30673 Read @var{length} bytes of memory starting at address @var{addr}.
30674 Note that @var{addr} may not be aligned to any particular boundary.
30676 The stub need not use any particular size or alignment when gathering
30677 data from memory for the response; even if @var{addr} is word-aligned
30678 and @var{length} is a multiple of the word size, the stub is free to
30679 use byte accesses, or not. For this reason, this packet may not be
30680 suitable for accessing memory-mapped I/O devices.
30681 @cindex alignment of remote memory accesses
30682 @cindex size of remote memory accesses
30683 @cindex memory, alignment and size of remote accesses
30687 @item @var{XX@dots{}}
30688 Memory contents; each byte is transmitted as a two-digit hexadecimal
30689 number. The reply may contain fewer bytes than requested if the
30690 server was able to read only part of the region of memory.
30695 @item M @var{addr},@var{length}:@var{XX@dots{}}
30696 @cindex @samp{M} packet
30697 Write @var{length} bytes of memory starting at address @var{addr}.
30698 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30699 hexadecimal number.
30706 for an error (this includes the case where only part of the data was
30711 @cindex @samp{p} packet
30712 Read the value of register @var{n}; @var{n} is in hex.
30713 @xref{read registers packet}, for a description of how the returned
30714 register value is encoded.
30718 @item @var{XX@dots{}}
30719 the register's value
30723 Indicating an unrecognized @var{query}.
30726 @item P @var{n@dots{}}=@var{r@dots{}}
30727 @anchor{write register packet}
30728 @cindex @samp{P} packet
30729 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30730 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30731 digits for each byte in the register (target byte order).
30741 @item q @var{name} @var{params}@dots{}
30742 @itemx Q @var{name} @var{params}@dots{}
30743 @cindex @samp{q} packet
30744 @cindex @samp{Q} packet
30745 General query (@samp{q}) and set (@samp{Q}). These packets are
30746 described fully in @ref{General Query Packets}.
30749 @cindex @samp{r} packet
30750 Reset the entire system.
30752 Don't use this packet; use the @samp{R} packet instead.
30755 @cindex @samp{R} packet
30756 Restart the program being debugged. @var{XX}, while needed, is ignored.
30757 This packet is only available in extended mode (@pxref{extended mode}).
30759 The @samp{R} packet has no reply.
30761 @item s @r{[}@var{addr}@r{]}
30762 @cindex @samp{s} packet
30763 Single step. @var{addr} is the address at which to resume. If
30764 @var{addr} is omitted, resume at same address.
30767 @xref{Stop Reply Packets}, for the reply specifications.
30769 @item S @var{sig}@r{[};@var{addr}@r{]}
30770 @anchor{step with signal packet}
30771 @cindex @samp{S} packet
30772 Step with signal. This is analogous to the @samp{C} packet, but
30773 requests a single-step, rather than a normal resumption of execution.
30776 @xref{Stop Reply Packets}, for the reply specifications.
30778 @item t @var{addr}:@var{PP},@var{MM}
30779 @cindex @samp{t} packet
30780 Search backwards starting at address @var{addr} for a match with pattern
30781 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30782 @var{addr} must be at least 3 digits.
30784 @item T @var{thread-id}
30785 @cindex @samp{T} packet
30786 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30791 thread is still alive
30797 Packets starting with @samp{v} are identified by a multi-letter name,
30798 up to the first @samp{;} or @samp{?} (or the end of the packet).
30800 @item vAttach;@var{pid}
30801 @cindex @samp{vAttach} packet
30802 Attach to a new process with the specified process ID @var{pid}.
30803 The process ID is a
30804 hexadecimal integer identifying the process. In all-stop mode, all
30805 threads in the attached process are stopped; in non-stop mode, it may be
30806 attached without being stopped if that is supported by the target.
30808 @c In non-stop mode, on a successful vAttach, the stub should set the
30809 @c current thread to a thread of the newly-attached process. After
30810 @c attaching, GDB queries for the attached process's thread ID with qC.
30811 @c Also note that, from a user perspective, whether or not the
30812 @c target is stopped on attach in non-stop mode depends on whether you
30813 @c use the foreground or background version of the attach command, not
30814 @c on what vAttach does; GDB does the right thing with respect to either
30815 @c stopping or restarting threads.
30817 This packet is only available in extended mode (@pxref{extended mode}).
30823 @item @r{Any stop packet}
30824 for success in all-stop mode (@pxref{Stop Reply Packets})
30826 for success in non-stop mode (@pxref{Remote Non-Stop})
30829 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
30830 @cindex @samp{vCont} packet
30831 Resume the inferior, specifying different actions for each thread.
30832 If an action is specified with no @var{thread-id}, then it is applied to any
30833 threads that don't have a specific action specified; if no default action is
30834 specified then other threads should remain stopped in all-stop mode and
30835 in their current state in non-stop mode.
30836 Specifying multiple
30837 default actions is an error; specifying no actions is also an error.
30838 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
30840 Currently supported actions are:
30846 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
30850 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
30855 The optional argument @var{addr} normally associated with the
30856 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
30857 not supported in @samp{vCont}.
30859 The @samp{t} action is only relevant in non-stop mode
30860 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
30861 A stop reply should be generated for any affected thread not already stopped.
30862 When a thread is stopped by means of a @samp{t} action,
30863 the corresponding stop reply should indicate that the thread has stopped with
30864 signal @samp{0}, regardless of whether the target uses some other signal
30865 as an implementation detail.
30868 @xref{Stop Reply Packets}, for the reply specifications.
30871 @cindex @samp{vCont?} packet
30872 Request a list of actions supported by the @samp{vCont} packet.
30876 @item vCont@r{[};@var{action}@dots{}@r{]}
30877 The @samp{vCont} packet is supported. Each @var{action} is a supported
30878 command in the @samp{vCont} packet.
30880 The @samp{vCont} packet is not supported.
30883 @item vFile:@var{operation}:@var{parameter}@dots{}
30884 @cindex @samp{vFile} packet
30885 Perform a file operation on the target system. For details,
30886 see @ref{Host I/O Packets}.
30888 @item vFlashErase:@var{addr},@var{length}
30889 @cindex @samp{vFlashErase} packet
30890 Direct the stub to erase @var{length} bytes of flash starting at
30891 @var{addr}. The region may enclose any number of flash blocks, but
30892 its start and end must fall on block boundaries, as indicated by the
30893 flash block size appearing in the memory map (@pxref{Memory Map
30894 Format}). @value{GDBN} groups flash memory programming operations
30895 together, and sends a @samp{vFlashDone} request after each group; the
30896 stub is allowed to delay erase operation until the @samp{vFlashDone}
30897 packet is received.
30899 The stub must support @samp{vCont} if it reports support for
30900 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
30901 this case @samp{vCont} actions can be specified to apply to all threads
30902 in a process by using the @samp{p@var{pid}.-1} form of the
30913 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
30914 @cindex @samp{vFlashWrite} packet
30915 Direct the stub to write data to flash address @var{addr}. The data
30916 is passed in binary form using the same encoding as for the @samp{X}
30917 packet (@pxref{Binary Data}). The memory ranges specified by
30918 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
30919 not overlap, and must appear in order of increasing addresses
30920 (although @samp{vFlashErase} packets for higher addresses may already
30921 have been received; the ordering is guaranteed only between
30922 @samp{vFlashWrite} packets). If a packet writes to an address that was
30923 neither erased by a preceding @samp{vFlashErase} packet nor by some other
30924 target-specific method, the results are unpredictable.
30932 for vFlashWrite addressing non-flash memory
30938 @cindex @samp{vFlashDone} packet
30939 Indicate to the stub that flash programming operation is finished.
30940 The stub is permitted to delay or batch the effects of a group of
30941 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
30942 @samp{vFlashDone} packet is received. The contents of the affected
30943 regions of flash memory are unpredictable until the @samp{vFlashDone}
30944 request is completed.
30946 @item vKill;@var{pid}
30947 @cindex @samp{vKill} packet
30948 Kill the process with the specified process ID. @var{pid} is a
30949 hexadecimal integer identifying the process. This packet is used in
30950 preference to @samp{k} when multiprocess protocol extensions are
30951 supported; see @ref{multiprocess extensions}.
30961 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
30962 @cindex @samp{vRun} packet
30963 Run the program @var{filename}, passing it each @var{argument} on its
30964 command line. The file and arguments are hex-encoded strings. If
30965 @var{filename} is an empty string, the stub may use a default program
30966 (e.g.@: the last program run). The program is created in the stopped
30969 @c FIXME: What about non-stop mode?
30971 This packet is only available in extended mode (@pxref{extended mode}).
30977 @item @r{Any stop packet}
30978 for success (@pxref{Stop Reply Packets})
30982 @anchor{vStopped packet}
30983 @cindex @samp{vStopped} packet
30985 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
30986 reply and prompt for the stub to report another one.
30990 @item @r{Any stop packet}
30991 if there is another unreported stop event (@pxref{Stop Reply Packets})
30993 if there are no unreported stop events
30996 @item X @var{addr},@var{length}:@var{XX@dots{}}
30998 @cindex @samp{X} packet
30999 Write data to memory, where the data is transmitted in binary.
31000 @var{addr} is address, @var{length} is number of bytes,
31001 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31011 @item z @var{type},@var{addr},@var{kind}
31012 @itemx Z @var{type},@var{addr},@var{kind}
31013 @anchor{insert breakpoint or watchpoint packet}
31014 @cindex @samp{z} packet
31015 @cindex @samp{Z} packets
31016 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31017 watchpoint starting at address @var{address} of kind @var{kind}.
31019 Each breakpoint and watchpoint packet @var{type} is documented
31022 @emph{Implementation notes: A remote target shall return an empty string
31023 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31024 remote target shall support either both or neither of a given
31025 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31026 avoid potential problems with duplicate packets, the operations should
31027 be implemented in an idempotent way.}
31029 @item z0,@var{addr},@var{kind}
31030 @itemx Z0,@var{addr},@var{kind}
31031 @cindex @samp{z0} packet
31032 @cindex @samp{Z0} packet
31033 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31034 @var{addr} of type @var{kind}.
31036 A memory breakpoint is implemented by replacing the instruction at
31037 @var{addr} with a software breakpoint or trap instruction. The
31038 @var{kind} is target-specific and typically indicates the size of
31039 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31040 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31041 architectures have additional meanings for @var{kind};
31042 see @ref{Architecture-Specific Protocol Details}.
31044 @emph{Implementation note: It is possible for a target to copy or move
31045 code that contains memory breakpoints (e.g., when implementing
31046 overlays). The behavior of this packet, in the presence of such a
31047 target, is not defined.}
31059 @item z1,@var{addr},@var{kind}
31060 @itemx Z1,@var{addr},@var{kind}
31061 @cindex @samp{z1} packet
31062 @cindex @samp{Z1} packet
31063 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31064 address @var{addr}.
31066 A hardware breakpoint is implemented using a mechanism that is not
31067 dependant on being able to modify the target's memory. @var{kind}
31068 has the same meaning as in @samp{Z0} packets.
31070 @emph{Implementation note: A hardware breakpoint is not affected by code
31083 @item z2,@var{addr},@var{kind}
31084 @itemx Z2,@var{addr},@var{kind}
31085 @cindex @samp{z2} packet
31086 @cindex @samp{Z2} packet
31087 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31088 @var{kind} is interpreted as the number of bytes to watch.
31100 @item z3,@var{addr},@var{kind}
31101 @itemx Z3,@var{addr},@var{kind}
31102 @cindex @samp{z3} packet
31103 @cindex @samp{Z3} packet
31104 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31105 @var{kind} is interpreted as the number of bytes to watch.
31117 @item z4,@var{addr},@var{kind}
31118 @itemx Z4,@var{addr},@var{kind}
31119 @cindex @samp{z4} packet
31120 @cindex @samp{Z4} packet
31121 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31122 @var{kind} is interpreted as the number of bytes to watch.
31136 @node Stop Reply Packets
31137 @section Stop Reply Packets
31138 @cindex stop reply packets
31140 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31141 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31142 receive any of the below as a reply. Except for @samp{?}
31143 and @samp{vStopped}, that reply is only returned
31144 when the target halts. In the below the exact meaning of @dfn{signal
31145 number} is defined by the header @file{include/gdb/signals.h} in the
31146 @value{GDBN} source code.
31148 As in the description of request packets, we include spaces in the
31149 reply templates for clarity; these are not part of the reply packet's
31150 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31156 The program received signal number @var{AA} (a two-digit hexadecimal
31157 number). This is equivalent to a @samp{T} response with no
31158 @var{n}:@var{r} pairs.
31160 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31161 @cindex @samp{T} packet reply
31162 The program received signal number @var{AA} (a two-digit hexadecimal
31163 number). This is equivalent to an @samp{S} response, except that the
31164 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31165 and other information directly in the stop reply packet, reducing
31166 round-trip latency. Single-step and breakpoint traps are reported
31167 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31171 If @var{n} is a hexadecimal number, it is a register number, and the
31172 corresponding @var{r} gives that register's value. @var{r} is a
31173 series of bytes in target byte order, with each byte given by a
31174 two-digit hex number.
31177 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31178 the stopped thread, as specified in @ref{thread-id syntax}.
31181 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31182 the core on which the stop event was detected.
31185 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31186 specific event that stopped the target. The currently defined stop
31187 reasons are listed below. @var{aa} should be @samp{05}, the trap
31188 signal. At most one stop reason should be present.
31191 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31192 and go on to the next; this allows us to extend the protocol in the
31196 The currently defined stop reasons are:
31202 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31205 @cindex shared library events, remote reply
31207 The packet indicates that the loaded libraries have changed.
31208 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31209 list of loaded libraries. @var{r} is ignored.
31211 @cindex replay log events, remote reply
31213 The packet indicates that the target cannot continue replaying
31214 logged execution events, because it has reached the end (or the
31215 beginning when executing backward) of the log. The value of @var{r}
31216 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31217 for more information.
31221 @itemx W @var{AA} ; process:@var{pid}
31222 The process exited, and @var{AA} is the exit status. This is only
31223 applicable to certain targets.
31225 The second form of the response, including the process ID of the exited
31226 process, can be used only when @value{GDBN} has reported support for
31227 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31228 The @var{pid} is formatted as a big-endian hex string.
31231 @itemx X @var{AA} ; process:@var{pid}
31232 The process terminated with signal @var{AA}.
31234 The second form of the response, including the process ID of the
31235 terminated process, can be used only when @value{GDBN} has reported
31236 support for multiprocess protocol extensions; see @ref{multiprocess
31237 extensions}. The @var{pid} is formatted as a big-endian hex string.
31239 @item O @var{XX}@dots{}
31240 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31241 written as the program's console output. This can happen at any time
31242 while the program is running and the debugger should continue to wait
31243 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31245 @item F @var{call-id},@var{parameter}@dots{}
31246 @var{call-id} is the identifier which says which host system call should
31247 be called. This is just the name of the function. Translation into the
31248 correct system call is only applicable as it's defined in @value{GDBN}.
31249 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31252 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31253 this very system call.
31255 The target replies with this packet when it expects @value{GDBN} to
31256 call a host system call on behalf of the target. @value{GDBN} replies
31257 with an appropriate @samp{F} packet and keeps up waiting for the next
31258 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31259 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31260 Protocol Extension}, for more details.
31264 @node General Query Packets
31265 @section General Query Packets
31266 @cindex remote query requests
31268 Packets starting with @samp{q} are @dfn{general query packets};
31269 packets starting with @samp{Q} are @dfn{general set packets}. General
31270 query and set packets are a semi-unified form for retrieving and
31271 sending information to and from the stub.
31273 The initial letter of a query or set packet is followed by a name
31274 indicating what sort of thing the packet applies to. For example,
31275 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31276 definitions with the stub. These packet names follow some
31281 The name must not contain commas, colons or semicolons.
31283 Most @value{GDBN} query and set packets have a leading upper case
31286 The names of custom vendor packets should use a company prefix, in
31287 lower case, followed by a period. For example, packets designed at
31288 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31289 foos) or @samp{Qacme.bar} (for setting bars).
31292 The name of a query or set packet should be separated from any
31293 parameters by a @samp{:}; the parameters themselves should be
31294 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31295 full packet name, and check for a separator or the end of the packet,
31296 in case two packet names share a common prefix. New packets should not begin
31297 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31298 packets predate these conventions, and have arguments without any terminator
31299 for the packet name; we suspect they are in widespread use in places that
31300 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31301 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31304 Like the descriptions of the other packets, each description here
31305 has a template showing the packet's overall syntax, followed by an
31306 explanation of the packet's meaning. We include spaces in some of the
31307 templates for clarity; these are not part of the packet's syntax. No
31308 @value{GDBN} packet uses spaces to separate its components.
31310 Here are the currently defined query and set packets:
31314 @item QAllow:@var{op}:@var{val}@dots{}
31315 @cindex @samp{QAllow} packet
31316 Specify which operations @value{GDBN} expects to request of the
31317 target, as a semicolon-separated list of operation name and value
31318 pairs. Possible values for @var{op} include @samp{WriteReg},
31319 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31320 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31321 indicating that @value{GDBN} will not request the operation, or 1,
31322 indicating that it may. (The target can then use this to set up its
31323 own internals optimally, for instance if the debugger never expects to
31324 insert breakpoints, it may not need to install its own trap handler.)
31327 @cindex current thread, remote request
31328 @cindex @samp{qC} packet
31329 Return the current thread ID.
31333 @item QC @var{thread-id}
31334 Where @var{thread-id} is a thread ID as documented in
31335 @ref{thread-id syntax}.
31336 @item @r{(anything else)}
31337 Any other reply implies the old thread ID.
31340 @item qCRC:@var{addr},@var{length}
31341 @cindex CRC of memory block, remote request
31342 @cindex @samp{qCRC} packet
31343 Compute the CRC checksum of a block of memory using CRC-32 defined in
31344 IEEE 802.3. The CRC is computed byte at a time, taking the most
31345 significant bit of each byte first. The initial pattern code
31346 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31348 @emph{Note:} This is the same CRC used in validating separate debug
31349 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31350 Files}). However the algorithm is slightly different. When validating
31351 separate debug files, the CRC is computed taking the @emph{least}
31352 significant bit of each byte first, and the final result is inverted to
31353 detect trailing zeros.
31358 An error (such as memory fault)
31359 @item C @var{crc32}
31360 The specified memory region's checksum is @var{crc32}.
31364 @itemx qsThreadInfo
31365 @cindex list active threads, remote request
31366 @cindex @samp{qfThreadInfo} packet
31367 @cindex @samp{qsThreadInfo} packet
31368 Obtain a list of all active thread IDs from the target (OS). Since there
31369 may be too many active threads to fit into one reply packet, this query
31370 works iteratively: it may require more than one query/reply sequence to
31371 obtain the entire list of threads. The first query of the sequence will
31372 be the @samp{qfThreadInfo} query; subsequent queries in the
31373 sequence will be the @samp{qsThreadInfo} query.
31375 NOTE: This packet replaces the @samp{qL} query (see below).
31379 @item m @var{thread-id}
31381 @item m @var{thread-id},@var{thread-id}@dots{}
31382 a comma-separated list of thread IDs
31384 (lower case letter @samp{L}) denotes end of list.
31387 In response to each query, the target will reply with a list of one or
31388 more thread IDs, separated by commas.
31389 @value{GDBN} will respond to each reply with a request for more thread
31390 ids (using the @samp{qs} form of the query), until the target responds
31391 with @samp{l} (lower-case el, for @dfn{last}).
31392 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31395 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31396 @cindex get thread-local storage address, remote request
31397 @cindex @samp{qGetTLSAddr} packet
31398 Fetch the address associated with thread local storage specified
31399 by @var{thread-id}, @var{offset}, and @var{lm}.
31401 @var{thread-id} is the thread ID associated with the
31402 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31404 @var{offset} is the (big endian, hex encoded) offset associated with the
31405 thread local variable. (This offset is obtained from the debug
31406 information associated with the variable.)
31408 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31409 the load module associated with the thread local storage. For example,
31410 a @sc{gnu}/Linux system will pass the link map address of the shared
31411 object associated with the thread local storage under consideration.
31412 Other operating environments may choose to represent the load module
31413 differently, so the precise meaning of this parameter will vary.
31417 @item @var{XX}@dots{}
31418 Hex encoded (big endian) bytes representing the address of the thread
31419 local storage requested.
31422 An error occurred. @var{nn} are hex digits.
31425 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31428 @item qGetTIBAddr:@var{thread-id}
31429 @cindex get thread information block address
31430 @cindex @samp{qGetTIBAddr} packet
31431 Fetch address of the Windows OS specific Thread Information Block.
31433 @var{thread-id} is the thread ID associated with the thread.
31437 @item @var{XX}@dots{}
31438 Hex encoded (big endian) bytes representing the linear address of the
31439 thread information block.
31442 An error occured. This means that either the thread was not found, or the
31443 address could not be retrieved.
31446 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31449 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31450 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31451 digit) is one to indicate the first query and zero to indicate a
31452 subsequent query; @var{threadcount} (two hex digits) is the maximum
31453 number of threads the response packet can contain; and @var{nextthread}
31454 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31455 returned in the response as @var{argthread}.
31457 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31461 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31462 Where: @var{count} (two hex digits) is the number of threads being
31463 returned; @var{done} (one hex digit) is zero to indicate more threads
31464 and one indicates no further threads; @var{argthreadid} (eight hex
31465 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31466 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31467 digits). See @code{remote.c:parse_threadlist_response()}.
31471 @cindex section offsets, remote request
31472 @cindex @samp{qOffsets} packet
31473 Get section offsets that the target used when relocating the downloaded
31478 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31479 Relocate the @code{Text} section by @var{xxx} from its original address.
31480 Relocate the @code{Data} section by @var{yyy} from its original address.
31481 If the object file format provides segment information (e.g.@: @sc{elf}
31482 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31483 segments by the supplied offsets.
31485 @emph{Note: while a @code{Bss} offset may be included in the response,
31486 @value{GDBN} ignores this and instead applies the @code{Data} offset
31487 to the @code{Bss} section.}
31489 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31490 Relocate the first segment of the object file, which conventionally
31491 contains program code, to a starting address of @var{xxx}. If
31492 @samp{DataSeg} is specified, relocate the second segment, which
31493 conventionally contains modifiable data, to a starting address of
31494 @var{yyy}. @value{GDBN} will report an error if the object file
31495 does not contain segment information, or does not contain at least
31496 as many segments as mentioned in the reply. Extra segments are
31497 kept at fixed offsets relative to the last relocated segment.
31500 @item qP @var{mode} @var{thread-id}
31501 @cindex thread information, remote request
31502 @cindex @samp{qP} packet
31503 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31504 encoded 32 bit mode; @var{thread-id} is a thread ID
31505 (@pxref{thread-id syntax}).
31507 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31510 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31514 @cindex non-stop mode, remote request
31515 @cindex @samp{QNonStop} packet
31517 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31518 @xref{Remote Non-Stop}, for more information.
31523 The request succeeded.
31526 An error occurred. @var{nn} are hex digits.
31529 An empty reply indicates that @samp{QNonStop} is not supported by
31533 This packet is not probed by default; the remote stub must request it,
31534 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31535 Use of this packet is controlled by the @code{set non-stop} command;
31536 @pxref{Non-Stop Mode}.
31538 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31539 @cindex pass signals to inferior, remote request
31540 @cindex @samp{QPassSignals} packet
31541 @anchor{QPassSignals}
31542 Each listed @var{signal} should be passed directly to the inferior process.
31543 Signals are numbered identically to continue packets and stop replies
31544 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31545 strictly greater than the previous item. These signals do not need to stop
31546 the inferior, or be reported to @value{GDBN}. All other signals should be
31547 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31548 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31549 new list. This packet improves performance when using @samp{handle
31550 @var{signal} nostop noprint pass}.
31555 The request succeeded.
31558 An error occurred. @var{nn} are hex digits.
31561 An empty reply indicates that @samp{QPassSignals} is not supported by
31565 Use of this packet is controlled by the @code{set remote pass-signals}
31566 command (@pxref{Remote Configuration, set remote pass-signals}).
31567 This packet is not probed by default; the remote stub must request it,
31568 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31570 @item qRcmd,@var{command}
31571 @cindex execute remote command, remote request
31572 @cindex @samp{qRcmd} packet
31573 @var{command} (hex encoded) is passed to the local interpreter for
31574 execution. Invalid commands should be reported using the output
31575 string. Before the final result packet, the target may also respond
31576 with a number of intermediate @samp{O@var{output}} console output
31577 packets. @emph{Implementors should note that providing access to a
31578 stubs's interpreter may have security implications}.
31583 A command response with no output.
31585 A command response with the hex encoded output string @var{OUTPUT}.
31587 Indicate a badly formed request.
31589 An empty reply indicates that @samp{qRcmd} is not recognized.
31592 (Note that the @code{qRcmd} packet's name is separated from the
31593 command by a @samp{,}, not a @samp{:}, contrary to the naming
31594 conventions above. Please don't use this packet as a model for new
31597 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31598 @cindex searching memory, in remote debugging
31599 @cindex @samp{qSearch:memory} packet
31600 @anchor{qSearch memory}
31601 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31602 @var{address} and @var{length} are encoded in hex.
31603 @var{search-pattern} is a sequence of bytes, hex encoded.
31608 The pattern was not found.
31610 The pattern was found at @var{address}.
31612 A badly formed request or an error was encountered while searching memory.
31614 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31617 @item QStartNoAckMode
31618 @cindex @samp{QStartNoAckMode} packet
31619 @anchor{QStartNoAckMode}
31620 Request that the remote stub disable the normal @samp{+}/@samp{-}
31621 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31626 The stub has switched to no-acknowledgment mode.
31627 @value{GDBN} acknowledges this reponse,
31628 but neither the stub nor @value{GDBN} shall send or expect further
31629 @samp{+}/@samp{-} acknowledgments in the current connection.
31631 An empty reply indicates that the stub does not support no-acknowledgment mode.
31634 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31635 @cindex supported packets, remote query
31636 @cindex features of the remote protocol
31637 @cindex @samp{qSupported} packet
31638 @anchor{qSupported}
31639 Tell the remote stub about features supported by @value{GDBN}, and
31640 query the stub for features it supports. This packet allows
31641 @value{GDBN} and the remote stub to take advantage of each others'
31642 features. @samp{qSupported} also consolidates multiple feature probes
31643 at startup, to improve @value{GDBN} performance---a single larger
31644 packet performs better than multiple smaller probe packets on
31645 high-latency links. Some features may enable behavior which must not
31646 be on by default, e.g.@: because it would confuse older clients or
31647 stubs. Other features may describe packets which could be
31648 automatically probed for, but are not. These features must be
31649 reported before @value{GDBN} will use them. This ``default
31650 unsupported'' behavior is not appropriate for all packets, but it
31651 helps to keep the initial connection time under control with new
31652 versions of @value{GDBN} which support increasing numbers of packets.
31656 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
31657 The stub supports or does not support each returned @var{stubfeature},
31658 depending on the form of each @var{stubfeature} (see below for the
31661 An empty reply indicates that @samp{qSupported} is not recognized,
31662 or that no features needed to be reported to @value{GDBN}.
31665 The allowed forms for each feature (either a @var{gdbfeature} in the
31666 @samp{qSupported} packet, or a @var{stubfeature} in the response)
31670 @item @var{name}=@var{value}
31671 The remote protocol feature @var{name} is supported, and associated
31672 with the specified @var{value}. The format of @var{value} depends
31673 on the feature, but it must not include a semicolon.
31675 The remote protocol feature @var{name} is supported, and does not
31676 need an associated value.
31678 The remote protocol feature @var{name} is not supported.
31680 The remote protocol feature @var{name} may be supported, and
31681 @value{GDBN} should auto-detect support in some other way when it is
31682 needed. This form will not be used for @var{gdbfeature} notifications,
31683 but may be used for @var{stubfeature} responses.
31686 Whenever the stub receives a @samp{qSupported} request, the
31687 supplied set of @value{GDBN} features should override any previous
31688 request. This allows @value{GDBN} to put the stub in a known
31689 state, even if the stub had previously been communicating with
31690 a different version of @value{GDBN}.
31692 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
31697 This feature indicates whether @value{GDBN} supports multiprocess
31698 extensions to the remote protocol. @value{GDBN} does not use such
31699 extensions unless the stub also reports that it supports them by
31700 including @samp{multiprocess+} in its @samp{qSupported} reply.
31701 @xref{multiprocess extensions}, for details.
31704 This feature indicates that @value{GDBN} supports the XML target
31705 description. If the stub sees @samp{xmlRegisters=} with target
31706 specific strings separated by a comma, it will report register
31710 This feature indicates whether @value{GDBN} supports the
31711 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
31712 instruction reply packet}).
31715 Stubs should ignore any unknown values for
31716 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31717 packet supports receiving packets of unlimited length (earlier
31718 versions of @value{GDBN} may reject overly long responses). Additional values
31719 for @var{gdbfeature} may be defined in the future to let the stub take
31720 advantage of new features in @value{GDBN}, e.g.@: incompatible
31721 improvements in the remote protocol---the @samp{multiprocess} feature is
31722 an example of such a feature. The stub's reply should be independent
31723 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31724 describes all the features it supports, and then the stub replies with
31725 all the features it supports.
31727 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31728 responses, as long as each response uses one of the standard forms.
31730 Some features are flags. A stub which supports a flag feature
31731 should respond with a @samp{+} form response. Other features
31732 require values, and the stub should respond with an @samp{=}
31735 Each feature has a default value, which @value{GDBN} will use if
31736 @samp{qSupported} is not available or if the feature is not mentioned
31737 in the @samp{qSupported} response. The default values are fixed; a
31738 stub is free to omit any feature responses that match the defaults.
31740 Not all features can be probed, but for those which can, the probing
31741 mechanism is useful: in some cases, a stub's internal
31742 architecture may not allow the protocol layer to know some information
31743 about the underlying target in advance. This is especially common in
31744 stubs which may be configured for multiple targets.
31746 These are the currently defined stub features and their properties:
31748 @multitable @columnfractions 0.35 0.2 0.12 0.2
31749 @c NOTE: The first row should be @headitem, but we do not yet require
31750 @c a new enough version of Texinfo (4.7) to use @headitem.
31752 @tab Value Required
31756 @item @samp{PacketSize}
31761 @item @samp{qXfer:auxv:read}
31766 @item @samp{qXfer:features:read}
31771 @item @samp{qXfer:libraries:read}
31776 @item @samp{qXfer:memory-map:read}
31781 @item @samp{qXfer:spu:read}
31786 @item @samp{qXfer:spu:write}
31791 @item @samp{qXfer:siginfo:read}
31796 @item @samp{qXfer:siginfo:write}
31801 @item @samp{qXfer:threads:read}
31807 @item @samp{QNonStop}
31812 @item @samp{QPassSignals}
31817 @item @samp{QStartNoAckMode}
31822 @item @samp{multiprocess}
31827 @item @samp{ConditionalTracepoints}
31832 @item @samp{ReverseContinue}
31837 @item @samp{ReverseStep}
31842 @item @samp{TracepointSource}
31847 @item @samp{QAllow}
31854 These are the currently defined stub features, in more detail:
31857 @cindex packet size, remote protocol
31858 @item PacketSize=@var{bytes}
31859 The remote stub can accept packets up to at least @var{bytes} in
31860 length. @value{GDBN} will send packets up to this size for bulk
31861 transfers, and will never send larger packets. This is a limit on the
31862 data characters in the packet, including the frame and checksum.
31863 There is no trailing NUL byte in a remote protocol packet; if the stub
31864 stores packets in a NUL-terminated format, it should allow an extra
31865 byte in its buffer for the NUL. If this stub feature is not supported,
31866 @value{GDBN} guesses based on the size of the @samp{g} packet response.
31868 @item qXfer:auxv:read
31869 The remote stub understands the @samp{qXfer:auxv:read} packet
31870 (@pxref{qXfer auxiliary vector read}).
31872 @item qXfer:features:read
31873 The remote stub understands the @samp{qXfer:features:read} packet
31874 (@pxref{qXfer target description read}).
31876 @item qXfer:libraries:read
31877 The remote stub understands the @samp{qXfer:libraries:read} packet
31878 (@pxref{qXfer library list read}).
31880 @item qXfer:memory-map:read
31881 The remote stub understands the @samp{qXfer:memory-map:read} packet
31882 (@pxref{qXfer memory map read}).
31884 @item qXfer:spu:read
31885 The remote stub understands the @samp{qXfer:spu:read} packet
31886 (@pxref{qXfer spu read}).
31888 @item qXfer:spu:write
31889 The remote stub understands the @samp{qXfer:spu:write} packet
31890 (@pxref{qXfer spu write}).
31892 @item qXfer:siginfo:read
31893 The remote stub understands the @samp{qXfer:siginfo:read} packet
31894 (@pxref{qXfer siginfo read}).
31896 @item qXfer:siginfo:write
31897 The remote stub understands the @samp{qXfer:siginfo:write} packet
31898 (@pxref{qXfer siginfo write}).
31900 @item qXfer:threads:read
31901 The remote stub understands the @samp{qXfer:threads:read} packet
31902 (@pxref{qXfer threads read}).
31905 The remote stub understands the @samp{QNonStop} packet
31906 (@pxref{QNonStop}).
31909 The remote stub understands the @samp{QPassSignals} packet
31910 (@pxref{QPassSignals}).
31912 @item QStartNoAckMode
31913 The remote stub understands the @samp{QStartNoAckMode} packet and
31914 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
31917 @anchor{multiprocess extensions}
31918 @cindex multiprocess extensions, in remote protocol
31919 The remote stub understands the multiprocess extensions to the remote
31920 protocol syntax. The multiprocess extensions affect the syntax of
31921 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
31922 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
31923 replies. Note that reporting this feature indicates support for the
31924 syntactic extensions only, not that the stub necessarily supports
31925 debugging of more than one process at a time. The stub must not use
31926 multiprocess extensions in packet replies unless @value{GDBN} has also
31927 indicated it supports them in its @samp{qSupported} request.
31929 @item qXfer:osdata:read
31930 The remote stub understands the @samp{qXfer:osdata:read} packet
31931 ((@pxref{qXfer osdata read}).
31933 @item ConditionalTracepoints
31934 The remote stub accepts and implements conditional expressions defined
31935 for tracepoints (@pxref{Tracepoint Conditions}).
31937 @item ReverseContinue
31938 The remote stub accepts and implements the reverse continue packet
31942 The remote stub accepts and implements the reverse step packet
31945 @item TracepointSource
31946 The remote stub understands the @samp{QTDPsrc} packet that supplies
31947 the source form of tracepoint definitions.
31950 The remote stub understands the @samp{QAllow} packet.
31955 @cindex symbol lookup, remote request
31956 @cindex @samp{qSymbol} packet
31957 Notify the target that @value{GDBN} is prepared to serve symbol lookup
31958 requests. Accept requests from the target for the values of symbols.
31963 The target does not need to look up any (more) symbols.
31964 @item qSymbol:@var{sym_name}
31965 The target requests the value of symbol @var{sym_name} (hex encoded).
31966 @value{GDBN} may provide the value by using the
31967 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
31971 @item qSymbol:@var{sym_value}:@var{sym_name}
31972 Set the value of @var{sym_name} to @var{sym_value}.
31974 @var{sym_name} (hex encoded) is the name of a symbol whose value the
31975 target has previously requested.
31977 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
31978 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
31984 The target does not need to look up any (more) symbols.
31985 @item qSymbol:@var{sym_name}
31986 The target requests the value of a new symbol @var{sym_name} (hex
31987 encoded). @value{GDBN} will continue to supply the values of symbols
31988 (if available), until the target ceases to request them.
31993 @item QTDisconnected
32000 @xref{Tracepoint Packets}.
32002 @item qThreadExtraInfo,@var{thread-id}
32003 @cindex thread attributes info, remote request
32004 @cindex @samp{qThreadExtraInfo} packet
32005 Obtain a printable string description of a thread's attributes from
32006 the target OS. @var{thread-id} is a thread ID;
32007 see @ref{thread-id syntax}. This
32008 string may contain anything that the target OS thinks is interesting
32009 for @value{GDBN} to tell the user about the thread. The string is
32010 displayed in @value{GDBN}'s @code{info threads} display. Some
32011 examples of possible thread extra info strings are @samp{Runnable}, or
32012 @samp{Blocked on Mutex}.
32016 @item @var{XX}@dots{}
32017 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32018 comprising the printable string containing the extra information about
32019 the thread's attributes.
32022 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32023 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32024 conventions above. Please don't use this packet as a model for new
32036 @xref{Tracepoint Packets}.
32038 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32039 @cindex read special object, remote request
32040 @cindex @samp{qXfer} packet
32041 @anchor{qXfer read}
32042 Read uninterpreted bytes from the target's special data area
32043 identified by the keyword @var{object}. Request @var{length} bytes
32044 starting at @var{offset} bytes into the data. The content and
32045 encoding of @var{annex} is specific to @var{object}; it can supply
32046 additional details about what data to access.
32048 Here are the specific requests of this form defined so far. All
32049 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32050 formats, listed below.
32053 @item qXfer:auxv:read::@var{offset},@var{length}
32054 @anchor{qXfer auxiliary vector read}
32055 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32056 auxiliary vector}. Note @var{annex} must be empty.
32058 This packet is not probed by default; the remote stub must request it,
32059 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32061 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32062 @anchor{qXfer target description read}
32063 Access the @dfn{target description}. @xref{Target Descriptions}. The
32064 annex specifies which XML document to access. The main description is
32065 always loaded from the @samp{target.xml} annex.
32067 This packet is not probed by default; the remote stub must request it,
32068 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32070 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32071 @anchor{qXfer library list read}
32072 Access the target's list of loaded libraries. @xref{Library List Format}.
32073 The annex part of the generic @samp{qXfer} packet must be empty
32074 (@pxref{qXfer read}).
32076 Targets which maintain a list of libraries in the program's memory do
32077 not need to implement this packet; it is designed for platforms where
32078 the operating system manages the list of loaded libraries.
32080 This packet is not probed by default; the remote stub must request it,
32081 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32083 @item qXfer:memory-map:read::@var{offset},@var{length}
32084 @anchor{qXfer memory map read}
32085 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32086 annex part of the generic @samp{qXfer} packet must be empty
32087 (@pxref{qXfer read}).
32089 This packet is not probed by default; the remote stub must request it,
32090 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32092 @item qXfer:siginfo:read::@var{offset},@var{length}
32093 @anchor{qXfer siginfo read}
32094 Read contents of the extra signal information on the target
32095 system. The annex part of the generic @samp{qXfer} packet must be
32096 empty (@pxref{qXfer read}).
32098 This packet is not probed by default; the remote stub must request it,
32099 by supplying an appropriate @samp{qSupported} response
32100 (@pxref{qSupported}).
32102 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32103 @anchor{qXfer spu read}
32104 Read contents of an @code{spufs} file on the target system. The
32105 annex specifies which file to read; it must be of the form
32106 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32107 in the target process, and @var{name} identifes the @code{spufs} file
32108 in that context to be accessed.
32110 This packet is not probed by default; the remote stub must request it,
32111 by supplying an appropriate @samp{qSupported} response
32112 (@pxref{qSupported}).
32114 @item qXfer:threads:read::@var{offset},@var{length}
32115 @anchor{qXfer threads read}
32116 Access the list of threads on target. @xref{Thread List Format}. The
32117 annex part of the generic @samp{qXfer} packet must be empty
32118 (@pxref{qXfer read}).
32120 This packet is not probed by default; the remote stub must request it,
32121 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32123 @item qXfer:osdata:read::@var{offset},@var{length}
32124 @anchor{qXfer osdata read}
32125 Access the target's @dfn{operating system information}.
32126 @xref{Operating System Information}.
32133 Data @var{data} (@pxref{Binary Data}) has been read from the
32134 target. There may be more data at a higher address (although
32135 it is permitted to return @samp{m} even for the last valid
32136 block of data, as long as at least one byte of data was read).
32137 @var{data} may have fewer bytes than the @var{length} in the
32141 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32142 There is no more data to be read. @var{data} may have fewer bytes
32143 than the @var{length} in the request.
32146 The @var{offset} in the request is at the end of the data.
32147 There is no more data to be read.
32150 The request was malformed, or @var{annex} was invalid.
32153 The offset was invalid, or there was an error encountered reading the data.
32154 @var{nn} is a hex-encoded @code{errno} value.
32157 An empty reply indicates the @var{object} string was not recognized by
32158 the stub, or that the object does not support reading.
32161 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32162 @cindex write data into object, remote request
32163 @anchor{qXfer write}
32164 Write uninterpreted bytes into the target's special data area
32165 identified by the keyword @var{object}, starting at @var{offset} bytes
32166 into the data. @var{data}@dots{} is the binary-encoded data
32167 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32168 is specific to @var{object}; it can supply additional details about what data
32171 Here are the specific requests of this form defined so far. All
32172 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32173 formats, listed below.
32176 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32177 @anchor{qXfer siginfo write}
32178 Write @var{data} to the extra signal information on the target system.
32179 The annex part of the generic @samp{qXfer} packet must be
32180 empty (@pxref{qXfer write}).
32182 This packet is not probed by default; the remote stub must request it,
32183 by supplying an appropriate @samp{qSupported} response
32184 (@pxref{qSupported}).
32186 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32187 @anchor{qXfer spu write}
32188 Write @var{data} to an @code{spufs} file on the target system. The
32189 annex specifies which file to write; it must be of the form
32190 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32191 in the target process, and @var{name} identifes the @code{spufs} file
32192 in that context to be accessed.
32194 This packet is not probed by default; the remote stub must request it,
32195 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32201 @var{nn} (hex encoded) is the number of bytes written.
32202 This may be fewer bytes than supplied in the request.
32205 The request was malformed, or @var{annex} was invalid.
32208 The offset was invalid, or there was an error encountered writing the data.
32209 @var{nn} is a hex-encoded @code{errno} value.
32212 An empty reply indicates the @var{object} string was not
32213 recognized by the stub, or that the object does not support writing.
32216 @item qXfer:@var{object}:@var{operation}:@dots{}
32217 Requests of this form may be added in the future. When a stub does
32218 not recognize the @var{object} keyword, or its support for
32219 @var{object} does not recognize the @var{operation} keyword, the stub
32220 must respond with an empty packet.
32222 @item qAttached:@var{pid}
32223 @cindex query attached, remote request
32224 @cindex @samp{qAttached} packet
32225 Return an indication of whether the remote server attached to an
32226 existing process or created a new process. When the multiprocess
32227 protocol extensions are supported (@pxref{multiprocess extensions}),
32228 @var{pid} is an integer in hexadecimal format identifying the target
32229 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32230 the query packet will be simplified as @samp{qAttached}.
32232 This query is used, for example, to know whether the remote process
32233 should be detached or killed when a @value{GDBN} session is ended with
32234 the @code{quit} command.
32239 The remote server attached to an existing process.
32241 The remote server created a new process.
32243 A badly formed request or an error was encountered.
32248 @node Architecture-Specific Protocol Details
32249 @section Architecture-Specific Protocol Details
32251 This section describes how the remote protocol is applied to specific
32252 target architectures. Also see @ref{Standard Target Features}, for
32253 details of XML target descriptions for each architecture.
32257 @subsubsection Breakpoint Kinds
32259 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32264 16-bit Thumb mode breakpoint.
32267 32-bit Thumb mode (Thumb-2) breakpoint.
32270 32-bit ARM mode breakpoint.
32276 @subsubsection Register Packet Format
32278 The following @code{g}/@code{G} packets have previously been defined.
32279 In the below, some thirty-two bit registers are transferred as
32280 sixty-four bits. Those registers should be zero/sign extended (which?)
32281 to fill the space allocated. Register bytes are transferred in target
32282 byte order. The two nibbles within a register byte are transferred
32283 most-significant - least-significant.
32289 All registers are transferred as thirty-two bit quantities in the order:
32290 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32291 registers; fsr; fir; fp.
32295 All registers are transferred as sixty-four bit quantities (including
32296 thirty-two bit registers such as @code{sr}). The ordering is the same
32301 @node Tracepoint Packets
32302 @section Tracepoint Packets
32303 @cindex tracepoint packets
32304 @cindex packets, tracepoint
32306 Here we describe the packets @value{GDBN} uses to implement
32307 tracepoints (@pxref{Tracepoints}).
32311 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32312 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32313 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32314 the tracepoint is disabled. @var{step} is the tracepoint's step
32315 count, and @var{pass} is its pass count. If an @samp{F} is present,
32316 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32317 the number of bytes that the target should copy elsewhere to make room
32318 for the tracepoint. If an @samp{X} is present, it introduces a
32319 tracepoint condition, which consists of a hexadecimal length, followed
32320 by a comma and hex-encoded bytes, in a manner similar to action
32321 encodings as described below. If the trailing @samp{-} is present,
32322 further @samp{QTDP} packets will follow to specify this tracepoint's
32328 The packet was understood and carried out.
32330 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32332 The packet was not recognized.
32335 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32336 Define actions to be taken when a tracepoint is hit. @var{n} and
32337 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32338 this tracepoint. This packet may only be sent immediately after
32339 another @samp{QTDP} packet that ended with a @samp{-}. If the
32340 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32341 specifying more actions for this tracepoint.
32343 In the series of action packets for a given tracepoint, at most one
32344 can have an @samp{S} before its first @var{action}. If such a packet
32345 is sent, it and the following packets define ``while-stepping''
32346 actions. Any prior packets define ordinary actions --- that is, those
32347 taken when the tracepoint is first hit. If no action packet has an
32348 @samp{S}, then all the packets in the series specify ordinary
32349 tracepoint actions.
32351 The @samp{@var{action}@dots{}} portion of the packet is a series of
32352 actions, concatenated without separators. Each action has one of the
32358 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32359 a hexadecimal number whose @var{i}'th bit is set if register number
32360 @var{i} should be collected. (The least significant bit is numbered
32361 zero.) Note that @var{mask} may be any number of digits long; it may
32362 not fit in a 32-bit word.
32364 @item M @var{basereg},@var{offset},@var{len}
32365 Collect @var{len} bytes of memory starting at the address in register
32366 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32367 @samp{-1}, then the range has a fixed address: @var{offset} is the
32368 address of the lowest byte to collect. The @var{basereg},
32369 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32370 values (the @samp{-1} value for @var{basereg} is a special case).
32372 @item X @var{len},@var{expr}
32373 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32374 it directs. @var{expr} is an agent expression, as described in
32375 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32376 two-digit hex number in the packet; @var{len} is the number of bytes
32377 in the expression (and thus one-half the number of hex digits in the
32382 Any number of actions may be packed together in a single @samp{QTDP}
32383 packet, as long as the packet does not exceed the maximum packet
32384 length (400 bytes, for many stubs). There may be only one @samp{R}
32385 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32386 actions. Any registers referred to by @samp{M} and @samp{X} actions
32387 must be collected by a preceding @samp{R} action. (The
32388 ``while-stepping'' actions are treated as if they were attached to a
32389 separate tracepoint, as far as these restrictions are concerned.)
32394 The packet was understood and carried out.
32396 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32398 The packet was not recognized.
32401 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32402 @cindex @samp{QTDPsrc} packet
32403 Specify a source string of tracepoint @var{n} at address @var{addr}.
32404 This is useful to get accurate reproduction of the tracepoints
32405 originally downloaded at the beginning of the trace run. @var{type}
32406 is the name of the tracepoint part, such as @samp{cond} for the
32407 tracepoint's conditional expression (see below for a list of types), while
32408 @var{bytes} is the string, encoded in hexadecimal.
32410 @var{start} is the offset of the @var{bytes} within the overall source
32411 string, while @var{slen} is the total length of the source string.
32412 This is intended for handling source strings that are longer than will
32413 fit in a single packet.
32414 @c Add detailed example when this info is moved into a dedicated
32415 @c tracepoint descriptions section.
32417 The available string types are @samp{at} for the location,
32418 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32419 @value{GDBN} sends a separate packet for each command in the action
32420 list, in the same order in which the commands are stored in the list.
32422 The target does not need to do anything with source strings except
32423 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32426 Although this packet is optional, and @value{GDBN} will only send it
32427 if the target replies with @samp{TracepointSource} @xref{General
32428 Query Packets}, it makes both disconnected tracing and trace files
32429 much easier to use. Otherwise the user must be careful that the
32430 tracepoints in effect while looking at trace frames are identical to
32431 the ones in effect during the trace run; even a small discrepancy
32432 could cause @samp{tdump} not to work, or a particular trace frame not
32435 @item QTDV:@var{n}:@var{value}
32436 @cindex define trace state variable, remote request
32437 @cindex @samp{QTDV} packet
32438 Create a new trace state variable, number @var{n}, with an initial
32439 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32440 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32441 the option of not using this packet for initial values of zero; the
32442 target should simply create the trace state variables as they are
32443 mentioned in expressions.
32445 @item QTFrame:@var{n}
32446 Select the @var{n}'th tracepoint frame from the buffer, and use the
32447 register and memory contents recorded there to answer subsequent
32448 request packets from @value{GDBN}.
32450 A successful reply from the stub indicates that the stub has found the
32451 requested frame. The response is a series of parts, concatenated
32452 without separators, describing the frame we selected. Each part has
32453 one of the following forms:
32457 The selected frame is number @var{n} in the trace frame buffer;
32458 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32459 was no frame matching the criteria in the request packet.
32462 The selected trace frame records a hit of tracepoint number @var{t};
32463 @var{t} is a hexadecimal number.
32467 @item QTFrame:pc:@var{addr}
32468 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32469 currently selected frame whose PC is @var{addr};
32470 @var{addr} is a hexadecimal number.
32472 @item QTFrame:tdp:@var{t}
32473 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32474 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32475 is a hexadecimal number.
32477 @item QTFrame:range:@var{start}:@var{end}
32478 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32479 currently selected frame whose PC is between @var{start} (inclusive)
32480 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32483 @item QTFrame:outside:@var{start}:@var{end}
32484 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32485 frame @emph{outside} the given range of addresses (exclusive).
32488 Begin the tracepoint experiment. Begin collecting data from
32489 tracepoint hits in the trace frame buffer. This packet supports the
32490 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32491 instruction reply packet}).
32494 End the tracepoint experiment. Stop collecting trace frames.
32497 Clear the table of tracepoints, and empty the trace frame buffer.
32499 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32500 Establish the given ranges of memory as ``transparent''. The stub
32501 will answer requests for these ranges from memory's current contents,
32502 if they were not collected as part of the tracepoint hit.
32504 @value{GDBN} uses this to mark read-only regions of memory, like those
32505 containing program code. Since these areas never change, they should
32506 still have the same contents they did when the tracepoint was hit, so
32507 there's no reason for the stub to refuse to provide their contents.
32509 @item QTDisconnected:@var{value}
32510 Set the choice to what to do with the tracing run when @value{GDBN}
32511 disconnects from the target. A @var{value} of 1 directs the target to
32512 continue the tracing run, while 0 tells the target to stop tracing if
32513 @value{GDBN} is no longer in the picture.
32516 Ask the stub if there is a trace experiment running right now.
32518 The reply has the form:
32522 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32523 @var{running} is a single digit @code{1} if the trace is presently
32524 running, or @code{0} if not. It is followed by semicolon-separated
32525 optional fields that an agent may use to report additional status.
32529 If the trace is not running, the agent may report any of several
32530 explanations as one of the optional fields:
32535 No trace has been run yet.
32538 The trace was stopped by a user-originated stop command.
32541 The trace stopped because the trace buffer filled up.
32543 @item tdisconnected:0
32544 The trace stopped because @value{GDBN} disconnected from the target.
32546 @item tpasscount:@var{tpnum}
32547 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32549 @item terror:@var{text}:@var{tpnum}
32550 The trace stopped because tracepoint @var{tpnum} had an error. The
32551 string @var{text} is available to describe the nature of the error
32552 (for instance, a divide by zero in the condition expression).
32553 @var{text} is hex encoded.
32556 The trace stopped for some other reason.
32560 Additional optional fields supply statistical and other information.
32561 Although not required, they are extremely useful for users monitoring
32562 the progress of a trace run. If a trace has stopped, and these
32563 numbers are reported, they must reflect the state of the just-stopped
32568 @item tframes:@var{n}
32569 The number of trace frames in the buffer.
32571 @item tcreated:@var{n}
32572 The total number of trace frames created during the run. This may
32573 be larger than the trace frame count, if the buffer is circular.
32575 @item tsize:@var{n}
32576 The total size of the trace buffer, in bytes.
32578 @item tfree:@var{n}
32579 The number of bytes still unused in the buffer.
32581 @item circular:@var{n}
32582 The value of the circular trace buffer flag. @code{1} means that the
32583 trace buffer is circular and old trace frames will be discarded if
32584 necessary to make room, @code{0} means that the trace buffer is linear
32587 @item disconn:@var{n}
32588 The value of the disconnected tracing flag. @code{1} means that
32589 tracing will continue after @value{GDBN} disconnects, @code{0} means
32590 that the trace run will stop.
32594 @item qTV:@var{var}
32595 @cindex trace state variable value, remote request
32596 @cindex @samp{qTV} packet
32597 Ask the stub for the value of the trace state variable number @var{var}.
32602 The value of the variable is @var{value}. This will be the current
32603 value of the variable if the user is examining a running target, or a
32604 saved value if the variable was collected in the trace frame that the
32605 user is looking at. Note that multiple requests may result in
32606 different reply values, such as when requesting values while the
32607 program is running.
32610 The value of the variable is unknown. This would occur, for example,
32611 if the user is examining a trace frame in which the requested variable
32617 These packets request data about tracepoints that are being used by
32618 the target. @value{GDBN} sends @code{qTfP} to get the first piece
32619 of data, and multiple @code{qTsP} to get additional pieces. Replies
32620 to these packets generally take the form of the @code{QTDP} packets
32621 that define tracepoints. (FIXME add detailed syntax)
32625 These packets request data about trace state variables that are on the
32626 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
32627 and multiple @code{qTsV} to get additional variables. Replies to
32628 these packets follow the syntax of the @code{QTDV} packets that define
32629 trace state variables.
32631 @item QTSave:@var{filename}
32632 This packet directs the target to save trace data to the file name
32633 @var{filename} in the target's filesystem. @var{filename} is encoded
32634 as a hex string; the interpretation of the file name (relative vs
32635 absolute, wild cards, etc) is up to the target.
32637 @item qTBuffer:@var{offset},@var{len}
32638 Return up to @var{len} bytes of the current contents of trace buffer,
32639 starting at @var{offset}. The trace buffer is treated as if it were
32640 a contiguous collection of traceframes, as per the trace file format.
32641 The reply consists as many hex-encoded bytes as the target can deliver
32642 in a packet; it is not an error to return fewer than were asked for.
32643 A reply consisting of just @code{l} indicates that no bytes are
32646 @item QTBuffer:circular:@var{value}
32647 This packet directs the target to use a circular trace buffer if
32648 @var{value} is 1, or a linear buffer if the value is 0.
32652 @subsection Relocate instruction reply packet
32653 When installing fast tracepoints in memory, the target may need to
32654 relocate the instruction currently at the tracepoint address to a
32655 different address in memory. For most instructions, a simple copy is
32656 enough, but, for example, call instructions that implicitly push the
32657 return address on the stack, and relative branches or other
32658 PC-relative instructions require offset adjustment, so that the effect
32659 of executing the instruction at a different address is the same as if
32660 it had executed in the original location.
32662 In response to several of the tracepoint packets, the target may also
32663 respond with a number of intermediate @samp{qRelocInsn} request
32664 packets before the final result packet, to have @value{GDBN} handle
32665 this relocation operation. If a packet supports this mechanism, its
32666 documentation will explicitly say so. See for example the above
32667 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
32668 format of the request is:
32671 @item qRelocInsn:@var{from};@var{to}
32673 This requests @value{GDBN} to copy instruction at address @var{from}
32674 to address @var{to}, possibly adjusted so that executing the
32675 instruction at @var{to} has the same effect as executing it at
32676 @var{from}. @value{GDBN} writes the adjusted instruction to target
32677 memory starting at @var{to}.
32682 @item qRelocInsn:@var{adjusted_size}
32683 Informs the stub the relocation is complete. @var{adjusted_size} is
32684 the length in bytes of resulting relocated instruction sequence.
32686 A badly formed request was detected, or an error was encountered while
32687 relocating the instruction.
32690 @node Host I/O Packets
32691 @section Host I/O Packets
32692 @cindex Host I/O, remote protocol
32693 @cindex file transfer, remote protocol
32695 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
32696 operations on the far side of a remote link. For example, Host I/O is
32697 used to upload and download files to a remote target with its own
32698 filesystem. Host I/O uses the same constant values and data structure
32699 layout as the target-initiated File-I/O protocol. However, the
32700 Host I/O packets are structured differently. The target-initiated
32701 protocol relies on target memory to store parameters and buffers.
32702 Host I/O requests are initiated by @value{GDBN}, and the
32703 target's memory is not involved. @xref{File-I/O Remote Protocol
32704 Extension}, for more details on the target-initiated protocol.
32706 The Host I/O request packets all encode a single operation along with
32707 its arguments. They have this format:
32711 @item vFile:@var{operation}: @var{parameter}@dots{}
32712 @var{operation} is the name of the particular request; the target
32713 should compare the entire packet name up to the second colon when checking
32714 for a supported operation. The format of @var{parameter} depends on
32715 the operation. Numbers are always passed in hexadecimal. Negative
32716 numbers have an explicit minus sign (i.e.@: two's complement is not
32717 used). Strings (e.g.@: filenames) are encoded as a series of
32718 hexadecimal bytes. The last argument to a system call may be a
32719 buffer of escaped binary data (@pxref{Binary Data}).
32723 The valid responses to Host I/O packets are:
32727 @item F @var{result} [, @var{errno}] [; @var{attachment}]
32728 @var{result} is the integer value returned by this operation, usually
32729 non-negative for success and -1 for errors. If an error has occured,
32730 @var{errno} will be included in the result. @var{errno} will have a
32731 value defined by the File-I/O protocol (@pxref{Errno Values}). For
32732 operations which return data, @var{attachment} supplies the data as a
32733 binary buffer. Binary buffers in response packets are escaped in the
32734 normal way (@pxref{Binary Data}). See the individual packet
32735 documentation for the interpretation of @var{result} and
32739 An empty response indicates that this operation is not recognized.
32743 These are the supported Host I/O operations:
32746 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
32747 Open a file at @var{pathname} and return a file descriptor for it, or
32748 return -1 if an error occurs. @var{pathname} is a string,
32749 @var{flags} is an integer indicating a mask of open flags
32750 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
32751 of mode bits to use if the file is created (@pxref{mode_t Values}).
32752 @xref{open}, for details of the open flags and mode values.
32754 @item vFile:close: @var{fd}
32755 Close the open file corresponding to @var{fd} and return 0, or
32756 -1 if an error occurs.
32758 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
32759 Read data from the open file corresponding to @var{fd}. Up to
32760 @var{count} bytes will be read from the file, starting at @var{offset}
32761 relative to the start of the file. The target may read fewer bytes;
32762 common reasons include packet size limits and an end-of-file
32763 condition. The number of bytes read is returned. Zero should only be
32764 returned for a successful read at the end of the file, or if
32765 @var{count} was zero.
32767 The data read should be returned as a binary attachment on success.
32768 If zero bytes were read, the response should include an empty binary
32769 attachment (i.e.@: a trailing semicolon). The return value is the
32770 number of target bytes read; the binary attachment may be longer if
32771 some characters were escaped.
32773 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32774 Write @var{data} (a binary buffer) to the open file corresponding
32775 to @var{fd}. Start the write at @var{offset} from the start of the
32776 file. Unlike many @code{write} system calls, there is no
32777 separate @var{count} argument; the length of @var{data} in the
32778 packet is used. @samp{vFile:write} returns the number of bytes written,
32779 which may be shorter than the length of @var{data}, or -1 if an
32782 @item vFile:unlink: @var{pathname}
32783 Delete the file at @var{pathname} on the target. Return 0,
32784 or -1 if an error occurs. @var{pathname} is a string.
32789 @section Interrupts
32790 @cindex interrupts (remote protocol)
32792 When a program on the remote target is running, @value{GDBN} may
32793 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32794 a @code{BREAK} followed by @code{g},
32795 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32797 The precise meaning of @code{BREAK} is defined by the transport
32798 mechanism and may, in fact, be undefined. @value{GDBN} does not
32799 currently define a @code{BREAK} mechanism for any of the network
32800 interfaces except for TCP, in which case @value{GDBN} sends the
32801 @code{telnet} BREAK sequence.
32803 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32804 transport mechanisms. It is represented by sending the single byte
32805 @code{0x03} without any of the usual packet overhead described in
32806 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32807 transmitted as part of a packet, it is considered to be packet data
32808 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32809 (@pxref{X packet}), used for binary downloads, may include an unescaped
32810 @code{0x03} as part of its packet.
32812 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32813 When Linux kernel receives this sequence from serial port,
32814 it stops execution and connects to gdb.
32816 Stubs are not required to recognize these interrupt mechanisms and the
32817 precise meaning associated with receipt of the interrupt is
32818 implementation defined. If the target supports debugging of multiple
32819 threads and/or processes, it should attempt to interrupt all
32820 currently-executing threads and processes.
32821 If the stub is successful at interrupting the
32822 running program, it should send one of the stop
32823 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
32824 of successfully stopping the program in all-stop mode, and a stop reply
32825 for each stopped thread in non-stop mode.
32826 Interrupts received while the
32827 program is stopped are discarded.
32829 @node Notification Packets
32830 @section Notification Packets
32831 @cindex notification packets
32832 @cindex packets, notification
32834 The @value{GDBN} remote serial protocol includes @dfn{notifications},
32835 packets that require no acknowledgment. Both the GDB and the stub
32836 may send notifications (although the only notifications defined at
32837 present are sent by the stub). Notifications carry information
32838 without incurring the round-trip latency of an acknowledgment, and so
32839 are useful for low-impact communications where occasional packet loss
32842 A notification packet has the form @samp{% @var{data} #
32843 @var{checksum}}, where @var{data} is the content of the notification,
32844 and @var{checksum} is a checksum of @var{data}, computed and formatted
32845 as for ordinary @value{GDBN} packets. A notification's @var{data}
32846 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
32847 receiving a notification, the recipient sends no @samp{+} or @samp{-}
32848 to acknowledge the notification's receipt or to report its corruption.
32850 Every notification's @var{data} begins with a name, which contains no
32851 colon characters, followed by a colon character.
32853 Recipients should silently ignore corrupted notifications and
32854 notifications they do not understand. Recipients should restart
32855 timeout periods on receipt of a well-formed notification, whether or
32856 not they understand it.
32858 Senders should only send the notifications described here when this
32859 protocol description specifies that they are permitted. In the
32860 future, we may extend the protocol to permit existing notifications in
32861 new contexts; this rule helps older senders avoid confusing newer
32864 (Older versions of @value{GDBN} ignore bytes received until they see
32865 the @samp{$} byte that begins an ordinary packet, so new stubs may
32866 transmit notifications without fear of confusing older clients. There
32867 are no notifications defined for @value{GDBN} to send at the moment, but we
32868 assume that most older stubs would ignore them, as well.)
32870 The following notification packets from the stub to @value{GDBN} are
32874 @item Stop: @var{reply}
32875 Report an asynchronous stop event in non-stop mode.
32876 The @var{reply} has the form of a stop reply, as
32877 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
32878 for information on how these notifications are acknowledged by
32882 @node Remote Non-Stop
32883 @section Remote Protocol Support for Non-Stop Mode
32885 @value{GDBN}'s remote protocol supports non-stop debugging of
32886 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
32887 supports non-stop mode, it should report that to @value{GDBN} by including
32888 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
32890 @value{GDBN} typically sends a @samp{QNonStop} packet only when
32891 establishing a new connection with the stub. Entering non-stop mode
32892 does not alter the state of any currently-running threads, but targets
32893 must stop all threads in any already-attached processes when entering
32894 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
32895 probe the target state after a mode change.
32897 In non-stop mode, when an attached process encounters an event that
32898 would otherwise be reported with a stop reply, it uses the
32899 asynchronous notification mechanism (@pxref{Notification Packets}) to
32900 inform @value{GDBN}. In contrast to all-stop mode, where all threads
32901 in all processes are stopped when a stop reply is sent, in non-stop
32902 mode only the thread reporting the stop event is stopped. That is,
32903 when reporting a @samp{S} or @samp{T} response to indicate completion
32904 of a step operation, hitting a breakpoint, or a fault, only the
32905 affected thread is stopped; any other still-running threads continue
32906 to run. When reporting a @samp{W} or @samp{X} response, all running
32907 threads belonging to other attached processes continue to run.
32909 Only one stop reply notification at a time may be pending; if
32910 additional stop events occur before @value{GDBN} has acknowledged the
32911 previous notification, they must be queued by the stub for later
32912 synchronous transmission in response to @samp{vStopped} packets from
32913 @value{GDBN}. Because the notification mechanism is unreliable,
32914 the stub is permitted to resend a stop reply notification
32915 if it believes @value{GDBN} may not have received it. @value{GDBN}
32916 ignores additional stop reply notifications received before it has
32917 finished processing a previous notification and the stub has completed
32918 sending any queued stop events.
32920 Otherwise, @value{GDBN} must be prepared to receive a stop reply
32921 notification at any time. Specifically, they may appear when
32922 @value{GDBN} is not otherwise reading input from the stub, or when
32923 @value{GDBN} is expecting to read a normal synchronous response or a
32924 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
32925 Notification packets are distinct from any other communication from
32926 the stub so there is no ambiguity.
32928 After receiving a stop reply notification, @value{GDBN} shall
32929 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
32930 as a regular, synchronous request to the stub. Such acknowledgment
32931 is not required to happen immediately, as @value{GDBN} is permitted to
32932 send other, unrelated packets to the stub first, which the stub should
32935 Upon receiving a @samp{vStopped} packet, if the stub has other queued
32936 stop events to report to @value{GDBN}, it shall respond by sending a
32937 normal stop reply response. @value{GDBN} shall then send another
32938 @samp{vStopped} packet to solicit further responses; again, it is
32939 permitted to send other, unrelated packets as well which the stub
32940 should process normally.
32942 If the stub receives a @samp{vStopped} packet and there are no
32943 additional stop events to report, the stub shall return an @samp{OK}
32944 response. At this point, if further stop events occur, the stub shall
32945 send a new stop reply notification, @value{GDBN} shall accept the
32946 notification, and the process shall be repeated.
32948 In non-stop mode, the target shall respond to the @samp{?} packet as
32949 follows. First, any incomplete stop reply notification/@samp{vStopped}
32950 sequence in progress is abandoned. The target must begin a new
32951 sequence reporting stop events for all stopped threads, whether or not
32952 it has previously reported those events to @value{GDBN}. The first
32953 stop reply is sent as a synchronous reply to the @samp{?} packet, and
32954 subsequent stop replies are sent as responses to @samp{vStopped} packets
32955 using the mechanism described above. The target must not send
32956 asynchronous stop reply notifications until the sequence is complete.
32957 If all threads are running when the target receives the @samp{?} packet,
32958 or if the target is not attached to any process, it shall respond
32961 @node Packet Acknowledgment
32962 @section Packet Acknowledgment
32964 @cindex acknowledgment, for @value{GDBN} remote
32965 @cindex packet acknowledgment, for @value{GDBN} remote
32966 By default, when either the host or the target machine receives a packet,
32967 the first response expected is an acknowledgment: either @samp{+} (to indicate
32968 the package was received correctly) or @samp{-} (to request retransmission).
32969 This mechanism allows the @value{GDBN} remote protocol to operate over
32970 unreliable transport mechanisms, such as a serial line.
32972 In cases where the transport mechanism is itself reliable (such as a pipe or
32973 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
32974 It may be desirable to disable them in that case to reduce communication
32975 overhead, or for other reasons. This can be accomplished by means of the
32976 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
32978 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
32979 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
32980 and response format still includes the normal checksum, as described in
32981 @ref{Overview}, but the checksum may be ignored by the receiver.
32983 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
32984 no-acknowledgment mode, it should report that to @value{GDBN}
32985 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
32986 @pxref{qSupported}.
32987 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
32988 disabled via the @code{set remote noack-packet off} command
32989 (@pxref{Remote Configuration}),
32990 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
32991 Only then may the stub actually turn off packet acknowledgments.
32992 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
32993 response, which can be safely ignored by the stub.
32995 Note that @code{set remote noack-packet} command only affects negotiation
32996 between @value{GDBN} and the stub when subsequent connections are made;
32997 it does not affect the protocol acknowledgment state for any current
32999 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33000 new connection is established,
33001 there is also no protocol request to re-enable the acknowledgments
33002 for the current connection, once disabled.
33007 Example sequence of a target being re-started. Notice how the restart
33008 does not get any direct output:
33013 @emph{target restarts}
33016 <- @code{T001:1234123412341234}
33020 Example sequence of a target being stepped by a single instruction:
33023 -> @code{G1445@dots{}}
33028 <- @code{T001:1234123412341234}
33032 <- @code{1455@dots{}}
33036 @node File-I/O Remote Protocol Extension
33037 @section File-I/O Remote Protocol Extension
33038 @cindex File-I/O remote protocol extension
33041 * File-I/O Overview::
33042 * Protocol Basics::
33043 * The F Request Packet::
33044 * The F Reply Packet::
33045 * The Ctrl-C Message::
33047 * List of Supported Calls::
33048 * Protocol-specific Representation of Datatypes::
33050 * File-I/O Examples::
33053 @node File-I/O Overview
33054 @subsection File-I/O Overview
33055 @cindex file-i/o overview
33057 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33058 target to use the host's file system and console I/O to perform various
33059 system calls. System calls on the target system are translated into a
33060 remote protocol packet to the host system, which then performs the needed
33061 actions and returns a response packet to the target system.
33062 This simulates file system operations even on targets that lack file systems.
33064 The protocol is defined to be independent of both the host and target systems.
33065 It uses its own internal representation of datatypes and values. Both
33066 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33067 translating the system-dependent value representations into the internal
33068 protocol representations when data is transmitted.
33070 The communication is synchronous. A system call is possible only when
33071 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33072 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33073 the target is stopped to allow deterministic access to the target's
33074 memory. Therefore File-I/O is not interruptible by target signals. On
33075 the other hand, it is possible to interrupt File-I/O by a user interrupt
33076 (@samp{Ctrl-C}) within @value{GDBN}.
33078 The target's request to perform a host system call does not finish
33079 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33080 after finishing the system call, the target returns to continuing the
33081 previous activity (continue, step). No additional continue or step
33082 request from @value{GDBN} is required.
33085 (@value{GDBP}) continue
33086 <- target requests 'system call X'
33087 target is stopped, @value{GDBN} executes system call
33088 -> @value{GDBN} returns result
33089 ... target continues, @value{GDBN} returns to wait for the target
33090 <- target hits breakpoint and sends a Txx packet
33093 The protocol only supports I/O on the console and to regular files on
33094 the host file system. Character or block special devices, pipes,
33095 named pipes, sockets or any other communication method on the host
33096 system are not supported by this protocol.
33098 File I/O is not supported in non-stop mode.
33100 @node Protocol Basics
33101 @subsection Protocol Basics
33102 @cindex protocol basics, file-i/o
33104 The File-I/O protocol uses the @code{F} packet as the request as well
33105 as reply packet. Since a File-I/O system call can only occur when
33106 @value{GDBN} is waiting for a response from the continuing or stepping target,
33107 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33108 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33109 This @code{F} packet contains all information needed to allow @value{GDBN}
33110 to call the appropriate host system call:
33114 A unique identifier for the requested system call.
33117 All parameters to the system call. Pointers are given as addresses
33118 in the target memory address space. Pointers to strings are given as
33119 pointer/length pair. Numerical values are given as they are.
33120 Numerical control flags are given in a protocol-specific representation.
33124 At this point, @value{GDBN} has to perform the following actions.
33128 If the parameters include pointer values to data needed as input to a
33129 system call, @value{GDBN} requests this data from the target with a
33130 standard @code{m} packet request. This additional communication has to be
33131 expected by the target implementation and is handled as any other @code{m}
33135 @value{GDBN} translates all value from protocol representation to host
33136 representation as needed. Datatypes are coerced into the host types.
33139 @value{GDBN} calls the system call.
33142 It then coerces datatypes back to protocol representation.
33145 If the system call is expected to return data in buffer space specified
33146 by pointer parameters to the call, the data is transmitted to the
33147 target using a @code{M} or @code{X} packet. This packet has to be expected
33148 by the target implementation and is handled as any other @code{M} or @code{X}
33153 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33154 necessary information for the target to continue. This at least contains
33161 @code{errno}, if has been changed by the system call.
33168 After having done the needed type and value coercion, the target continues
33169 the latest continue or step action.
33171 @node The F Request Packet
33172 @subsection The @code{F} Request Packet
33173 @cindex file-i/o request packet
33174 @cindex @code{F} request packet
33176 The @code{F} request packet has the following format:
33179 @item F@var{call-id},@var{parameter@dots{}}
33181 @var{call-id} is the identifier to indicate the host system call to be called.
33182 This is just the name of the function.
33184 @var{parameter@dots{}} are the parameters to the system call.
33185 Parameters are hexadecimal integer values, either the actual values in case
33186 of scalar datatypes, pointers to target buffer space in case of compound
33187 datatypes and unspecified memory areas, or pointer/length pairs in case
33188 of string parameters. These are appended to the @var{call-id} as a
33189 comma-delimited list. All values are transmitted in ASCII
33190 string representation, pointer/length pairs separated by a slash.
33196 @node The F Reply Packet
33197 @subsection The @code{F} Reply Packet
33198 @cindex file-i/o reply packet
33199 @cindex @code{F} reply packet
33201 The @code{F} reply packet has the following format:
33205 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33207 @var{retcode} is the return code of the system call as hexadecimal value.
33209 @var{errno} is the @code{errno} set by the call, in protocol-specific
33211 This parameter can be omitted if the call was successful.
33213 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33214 case, @var{errno} must be sent as well, even if the call was successful.
33215 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33222 or, if the call was interrupted before the host call has been performed:
33229 assuming 4 is the protocol-specific representation of @code{EINTR}.
33234 @node The Ctrl-C Message
33235 @subsection The @samp{Ctrl-C} Message
33236 @cindex ctrl-c message, in file-i/o protocol
33238 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33239 reply packet (@pxref{The F Reply Packet}),
33240 the target should behave as if it had
33241 gotten a break message. The meaning for the target is ``system call
33242 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33243 (as with a break message) and return to @value{GDBN} with a @code{T02}
33246 It's important for the target to know in which
33247 state the system call was interrupted. There are two possible cases:
33251 The system call hasn't been performed on the host yet.
33254 The system call on the host has been finished.
33258 These two states can be distinguished by the target by the value of the
33259 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33260 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33261 on POSIX systems. In any other case, the target may presume that the
33262 system call has been finished --- successfully or not --- and should behave
33263 as if the break message arrived right after the system call.
33265 @value{GDBN} must behave reliably. If the system call has not been called
33266 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33267 @code{errno} in the packet. If the system call on the host has been finished
33268 before the user requests a break, the full action must be finished by
33269 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33270 The @code{F} packet may only be sent when either nothing has happened
33271 or the full action has been completed.
33274 @subsection Console I/O
33275 @cindex console i/o as part of file-i/o
33277 By default and if not explicitly closed by the target system, the file
33278 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33279 on the @value{GDBN} console is handled as any other file output operation
33280 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33281 by @value{GDBN} so that after the target read request from file descriptor
33282 0 all following typing is buffered until either one of the following
33287 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33289 system call is treated as finished.
33292 The user presses @key{RET}. This is treated as end of input with a trailing
33296 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33297 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33301 If the user has typed more characters than fit in the buffer given to
33302 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33303 either another @code{read(0, @dots{})} is requested by the target, or debugging
33304 is stopped at the user's request.
33307 @node List of Supported Calls
33308 @subsection List of Supported Calls
33309 @cindex list of supported file-i/o calls
33326 @unnumberedsubsubsec open
33327 @cindex open, file-i/o system call
33332 int open(const char *pathname, int flags);
33333 int open(const char *pathname, int flags, mode_t mode);
33337 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33340 @var{flags} is the bitwise @code{OR} of the following values:
33344 If the file does not exist it will be created. The host
33345 rules apply as far as file ownership and time stamps
33349 When used with @code{O_CREAT}, if the file already exists it is
33350 an error and open() fails.
33353 If the file already exists and the open mode allows
33354 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33355 truncated to zero length.
33358 The file is opened in append mode.
33361 The file is opened for reading only.
33364 The file is opened for writing only.
33367 The file is opened for reading and writing.
33371 Other bits are silently ignored.
33375 @var{mode} is the bitwise @code{OR} of the following values:
33379 User has read permission.
33382 User has write permission.
33385 Group has read permission.
33388 Group has write permission.
33391 Others have read permission.
33394 Others have write permission.
33398 Other bits are silently ignored.
33401 @item Return value:
33402 @code{open} returns the new file descriptor or -1 if an error
33409 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33412 @var{pathname} refers to a directory.
33415 The requested access is not allowed.
33418 @var{pathname} was too long.
33421 A directory component in @var{pathname} does not exist.
33424 @var{pathname} refers to a device, pipe, named pipe or socket.
33427 @var{pathname} refers to a file on a read-only filesystem and
33428 write access was requested.
33431 @var{pathname} is an invalid pointer value.
33434 No space on device to create the file.
33437 The process already has the maximum number of files open.
33440 The limit on the total number of files open on the system
33444 The call was interrupted by the user.
33450 @unnumberedsubsubsec close
33451 @cindex close, file-i/o system call
33460 @samp{Fclose,@var{fd}}
33462 @item Return value:
33463 @code{close} returns zero on success, or -1 if an error occurred.
33469 @var{fd} isn't a valid open file descriptor.
33472 The call was interrupted by the user.
33478 @unnumberedsubsubsec read
33479 @cindex read, file-i/o system call
33484 int read(int fd, void *buf, unsigned int count);
33488 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33490 @item Return value:
33491 On success, the number of bytes read is returned.
33492 Zero indicates end of file. If count is zero, read
33493 returns zero as well. On error, -1 is returned.
33499 @var{fd} is not a valid file descriptor or is not open for
33503 @var{bufptr} is an invalid pointer value.
33506 The call was interrupted by the user.
33512 @unnumberedsubsubsec write
33513 @cindex write, file-i/o system call
33518 int write(int fd, const void *buf, unsigned int count);
33522 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33524 @item Return value:
33525 On success, the number of bytes written are returned.
33526 Zero indicates nothing was written. On error, -1
33533 @var{fd} is not a valid file descriptor or is not open for
33537 @var{bufptr} is an invalid pointer value.
33540 An attempt was made to write a file that exceeds the
33541 host-specific maximum file size allowed.
33544 No space on device to write the data.
33547 The call was interrupted by the user.
33553 @unnumberedsubsubsec lseek
33554 @cindex lseek, file-i/o system call
33559 long lseek (int fd, long offset, int flag);
33563 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33565 @var{flag} is one of:
33569 The offset is set to @var{offset} bytes.
33572 The offset is set to its current location plus @var{offset}
33576 The offset is set to the size of the file plus @var{offset}
33580 @item Return value:
33581 On success, the resulting unsigned offset in bytes from
33582 the beginning of the file is returned. Otherwise, a
33583 value of -1 is returned.
33589 @var{fd} is not a valid open file descriptor.
33592 @var{fd} is associated with the @value{GDBN} console.
33595 @var{flag} is not a proper value.
33598 The call was interrupted by the user.
33604 @unnumberedsubsubsec rename
33605 @cindex rename, file-i/o system call
33610 int rename(const char *oldpath, const char *newpath);
33614 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
33616 @item Return value:
33617 On success, zero is returned. On error, -1 is returned.
33623 @var{newpath} is an existing directory, but @var{oldpath} is not a
33627 @var{newpath} is a non-empty directory.
33630 @var{oldpath} or @var{newpath} is a directory that is in use by some
33634 An attempt was made to make a directory a subdirectory
33638 A component used as a directory in @var{oldpath} or new
33639 path is not a directory. Or @var{oldpath} is a directory
33640 and @var{newpath} exists but is not a directory.
33643 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
33646 No access to the file or the path of the file.
33650 @var{oldpath} or @var{newpath} was too long.
33653 A directory component in @var{oldpath} or @var{newpath} does not exist.
33656 The file is on a read-only filesystem.
33659 The device containing the file has no room for the new
33663 The call was interrupted by the user.
33669 @unnumberedsubsubsec unlink
33670 @cindex unlink, file-i/o system call
33675 int unlink(const char *pathname);
33679 @samp{Funlink,@var{pathnameptr}/@var{len}}
33681 @item Return value:
33682 On success, zero is returned. On error, -1 is returned.
33688 No access to the file or the path of the file.
33691 The system does not allow unlinking of directories.
33694 The file @var{pathname} cannot be unlinked because it's
33695 being used by another process.
33698 @var{pathnameptr} is an invalid pointer value.
33701 @var{pathname} was too long.
33704 A directory component in @var{pathname} does not exist.
33707 A component of the path is not a directory.
33710 The file is on a read-only filesystem.
33713 The call was interrupted by the user.
33719 @unnumberedsubsubsec stat/fstat
33720 @cindex fstat, file-i/o system call
33721 @cindex stat, file-i/o system call
33726 int stat(const char *pathname, struct stat *buf);
33727 int fstat(int fd, struct stat *buf);
33731 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
33732 @samp{Ffstat,@var{fd},@var{bufptr}}
33734 @item Return value:
33735 On success, zero is returned. On error, -1 is returned.
33741 @var{fd} is not a valid open file.
33744 A directory component in @var{pathname} does not exist or the
33745 path is an empty string.
33748 A component of the path is not a directory.
33751 @var{pathnameptr} is an invalid pointer value.
33754 No access to the file or the path of the file.
33757 @var{pathname} was too long.
33760 The call was interrupted by the user.
33766 @unnumberedsubsubsec gettimeofday
33767 @cindex gettimeofday, file-i/o system call
33772 int gettimeofday(struct timeval *tv, void *tz);
33776 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33778 @item Return value:
33779 On success, 0 is returned, -1 otherwise.
33785 @var{tz} is a non-NULL pointer.
33788 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33794 @unnumberedsubsubsec isatty
33795 @cindex isatty, file-i/o system call
33800 int isatty(int fd);
33804 @samp{Fisatty,@var{fd}}
33806 @item Return value:
33807 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33813 The call was interrupted by the user.
33818 Note that the @code{isatty} call is treated as a special case: it returns
33819 1 to the target if the file descriptor is attached
33820 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
33821 would require implementing @code{ioctl} and would be more complex than
33826 @unnumberedsubsubsec system
33827 @cindex system, file-i/o system call
33832 int system(const char *command);
33836 @samp{Fsystem,@var{commandptr}/@var{len}}
33838 @item Return value:
33839 If @var{len} is zero, the return value indicates whether a shell is
33840 available. A zero return value indicates a shell is not available.
33841 For non-zero @var{len}, the value returned is -1 on error and the
33842 return status of the command otherwise. Only the exit status of the
33843 command is returned, which is extracted from the host's @code{system}
33844 return value by calling @code{WEXITSTATUS(retval)}. In case
33845 @file{/bin/sh} could not be executed, 127 is returned.
33851 The call was interrupted by the user.
33856 @value{GDBN} takes over the full task of calling the necessary host calls
33857 to perform the @code{system} call. The return value of @code{system} on
33858 the host is simplified before it's returned
33859 to the target. Any termination signal information from the child process
33860 is discarded, and the return value consists
33861 entirely of the exit status of the called command.
33863 Due to security concerns, the @code{system} call is by default refused
33864 by @value{GDBN}. The user has to allow this call explicitly with the
33865 @code{set remote system-call-allowed 1} command.
33868 @item set remote system-call-allowed
33869 @kindex set remote system-call-allowed
33870 Control whether to allow the @code{system} calls in the File I/O
33871 protocol for the remote target. The default is zero (disabled).
33873 @item show remote system-call-allowed
33874 @kindex show remote system-call-allowed
33875 Show whether the @code{system} calls are allowed in the File I/O
33879 @node Protocol-specific Representation of Datatypes
33880 @subsection Protocol-specific Representation of Datatypes
33881 @cindex protocol-specific representation of datatypes, in file-i/o protocol
33884 * Integral Datatypes::
33886 * Memory Transfer::
33891 @node Integral Datatypes
33892 @unnumberedsubsubsec Integral Datatypes
33893 @cindex integral datatypes, in file-i/o protocol
33895 The integral datatypes used in the system calls are @code{int},
33896 @code{unsigned int}, @code{long}, @code{unsigned long},
33897 @code{mode_t}, and @code{time_t}.
33899 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
33900 implemented as 32 bit values in this protocol.
33902 @code{long} and @code{unsigned long} are implemented as 64 bit types.
33904 @xref{Limits}, for corresponding MIN and MAX values (similar to those
33905 in @file{limits.h}) to allow range checking on host and target.
33907 @code{time_t} datatypes are defined as seconds since the Epoch.
33909 All integral datatypes transferred as part of a memory read or write of a
33910 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
33913 @node Pointer Values
33914 @unnumberedsubsubsec Pointer Values
33915 @cindex pointer values, in file-i/o protocol
33917 Pointers to target data are transmitted as they are. An exception
33918 is made for pointers to buffers for which the length isn't
33919 transmitted as part of the function call, namely strings. Strings
33920 are transmitted as a pointer/length pair, both as hex values, e.g.@:
33927 which is a pointer to data of length 18 bytes at position 0x1aaf.
33928 The length is defined as the full string length in bytes, including
33929 the trailing null byte. For example, the string @code{"hello world"}
33930 at address 0x123456 is transmitted as
33936 @node Memory Transfer
33937 @unnumberedsubsubsec Memory Transfer
33938 @cindex memory transfer, in file-i/o protocol
33940 Structured data which is transferred using a memory read or write (for
33941 example, a @code{struct stat}) is expected to be in a protocol-specific format
33942 with all scalar multibyte datatypes being big endian. Translation to
33943 this representation needs to be done both by the target before the @code{F}
33944 packet is sent, and by @value{GDBN} before
33945 it transfers memory to the target. Transferred pointers to structured
33946 data should point to the already-coerced data at any time.
33950 @unnumberedsubsubsec struct stat
33951 @cindex struct stat, in file-i/o protocol
33953 The buffer of type @code{struct stat} used by the target and @value{GDBN}
33954 is defined as follows:
33958 unsigned int st_dev; /* device */
33959 unsigned int st_ino; /* inode */
33960 mode_t st_mode; /* protection */
33961 unsigned int st_nlink; /* number of hard links */
33962 unsigned int st_uid; /* user ID of owner */
33963 unsigned int st_gid; /* group ID of owner */
33964 unsigned int st_rdev; /* device type (if inode device) */
33965 unsigned long st_size; /* total size, in bytes */
33966 unsigned long st_blksize; /* blocksize for filesystem I/O */
33967 unsigned long st_blocks; /* number of blocks allocated */
33968 time_t st_atime; /* time of last access */
33969 time_t st_mtime; /* time of last modification */
33970 time_t st_ctime; /* time of last change */
33974 The integral datatypes conform to the definitions given in the
33975 appropriate section (see @ref{Integral Datatypes}, for details) so this
33976 structure is of size 64 bytes.
33978 The values of several fields have a restricted meaning and/or
33984 A value of 0 represents a file, 1 the console.
33987 No valid meaning for the target. Transmitted unchanged.
33990 Valid mode bits are described in @ref{Constants}. Any other
33991 bits have currently no meaning for the target.
33996 No valid meaning for the target. Transmitted unchanged.
34001 These values have a host and file system dependent
34002 accuracy. Especially on Windows hosts, the file system may not
34003 support exact timing values.
34006 The target gets a @code{struct stat} of the above representation and is
34007 responsible for coercing it to the target representation before
34010 Note that due to size differences between the host, target, and protocol
34011 representations of @code{struct stat} members, these members could eventually
34012 get truncated on the target.
34014 @node struct timeval
34015 @unnumberedsubsubsec struct timeval
34016 @cindex struct timeval, in file-i/o protocol
34018 The buffer of type @code{struct timeval} used by the File-I/O protocol
34019 is defined as follows:
34023 time_t tv_sec; /* second */
34024 long tv_usec; /* microsecond */
34028 The integral datatypes conform to the definitions given in the
34029 appropriate section (see @ref{Integral Datatypes}, for details) so this
34030 structure is of size 8 bytes.
34033 @subsection Constants
34034 @cindex constants, in file-i/o protocol
34036 The following values are used for the constants inside of the
34037 protocol. @value{GDBN} and target are responsible for translating these
34038 values before and after the call as needed.
34049 @unnumberedsubsubsec Open Flags
34050 @cindex open flags, in file-i/o protocol
34052 All values are given in hexadecimal representation.
34064 @node mode_t Values
34065 @unnumberedsubsubsec mode_t Values
34066 @cindex mode_t values, in file-i/o protocol
34068 All values are given in octal representation.
34085 @unnumberedsubsubsec Errno Values
34086 @cindex errno values, in file-i/o protocol
34088 All values are given in decimal representation.
34113 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34114 any error value not in the list of supported error numbers.
34117 @unnumberedsubsubsec Lseek Flags
34118 @cindex lseek flags, in file-i/o protocol
34127 @unnumberedsubsubsec Limits
34128 @cindex limits, in file-i/o protocol
34130 All values are given in decimal representation.
34133 INT_MIN -2147483648
34135 UINT_MAX 4294967295
34136 LONG_MIN -9223372036854775808
34137 LONG_MAX 9223372036854775807
34138 ULONG_MAX 18446744073709551615
34141 @node File-I/O Examples
34142 @subsection File-I/O Examples
34143 @cindex file-i/o examples
34145 Example sequence of a write call, file descriptor 3, buffer is at target
34146 address 0x1234, 6 bytes should be written:
34149 <- @code{Fwrite,3,1234,6}
34150 @emph{request memory read from target}
34153 @emph{return "6 bytes written"}
34157 Example sequence of a read call, file descriptor 3, buffer is at target
34158 address 0x1234, 6 bytes should be read:
34161 <- @code{Fread,3,1234,6}
34162 @emph{request memory write to target}
34163 -> @code{X1234,6:XXXXXX}
34164 @emph{return "6 bytes read"}
34168 Example sequence of a read call, call fails on the host due to invalid
34169 file descriptor (@code{EBADF}):
34172 <- @code{Fread,3,1234,6}
34176 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34180 <- @code{Fread,3,1234,6}
34185 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34189 <- @code{Fread,3,1234,6}
34190 -> @code{X1234,6:XXXXXX}
34194 @node Library List Format
34195 @section Library List Format
34196 @cindex library list format, remote protocol
34198 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34199 same process as your application to manage libraries. In this case,
34200 @value{GDBN} can use the loader's symbol table and normal memory
34201 operations to maintain a list of shared libraries. On other
34202 platforms, the operating system manages loaded libraries.
34203 @value{GDBN} can not retrieve the list of currently loaded libraries
34204 through memory operations, so it uses the @samp{qXfer:libraries:read}
34205 packet (@pxref{qXfer library list read}) instead. The remote stub
34206 queries the target's operating system and reports which libraries
34209 The @samp{qXfer:libraries:read} packet returns an XML document which
34210 lists loaded libraries and their offsets. Each library has an
34211 associated name and one or more segment or section base addresses,
34212 which report where the library was loaded in memory.
34214 For the common case of libraries that are fully linked binaries, the
34215 library should have a list of segments. If the target supports
34216 dynamic linking of a relocatable object file, its library XML element
34217 should instead include a list of allocated sections. The segment or
34218 section bases are start addresses, not relocation offsets; they do not
34219 depend on the library's link-time base addresses.
34221 @value{GDBN} must be linked with the Expat library to support XML
34222 library lists. @xref{Expat}.
34224 A simple memory map, with one loaded library relocated by a single
34225 offset, looks like this:
34229 <library name="/lib/libc.so.6">
34230 <segment address="0x10000000"/>
34235 Another simple memory map, with one loaded library with three
34236 allocated sections (.text, .data, .bss), looks like this:
34240 <library name="sharedlib.o">
34241 <section address="0x10000000"/>
34242 <section address="0x20000000"/>
34243 <section address="0x30000000"/>
34248 The format of a library list is described by this DTD:
34251 <!-- library-list: Root element with versioning -->
34252 <!ELEMENT library-list (library)*>
34253 <!ATTLIST library-list version CDATA #FIXED "1.0">
34254 <!ELEMENT library (segment*, section*)>
34255 <!ATTLIST library name CDATA #REQUIRED>
34256 <!ELEMENT segment EMPTY>
34257 <!ATTLIST segment address CDATA #REQUIRED>
34258 <!ELEMENT section EMPTY>
34259 <!ATTLIST section address CDATA #REQUIRED>
34262 In addition, segments and section descriptors cannot be mixed within a
34263 single library element, and you must supply at least one segment or
34264 section for each library.
34266 @node Memory Map Format
34267 @section Memory Map Format
34268 @cindex memory map format
34270 To be able to write into flash memory, @value{GDBN} needs to obtain a
34271 memory map from the target. This section describes the format of the
34274 The memory map is obtained using the @samp{qXfer:memory-map:read}
34275 (@pxref{qXfer memory map read}) packet and is an XML document that
34276 lists memory regions.
34278 @value{GDBN} must be linked with the Expat library to support XML
34279 memory maps. @xref{Expat}.
34281 The top-level structure of the document is shown below:
34284 <?xml version="1.0"?>
34285 <!DOCTYPE memory-map
34286 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34287 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34293 Each region can be either:
34298 A region of RAM starting at @var{addr} and extending for @var{length}
34302 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34307 A region of read-only memory:
34310 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34315 A region of flash memory, with erasure blocks @var{blocksize}
34319 <memory type="flash" start="@var{addr}" length="@var{length}">
34320 <property name="blocksize">@var{blocksize}</property>
34326 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34327 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34328 packets to write to addresses in such ranges.
34330 The formal DTD for memory map format is given below:
34333 <!-- ................................................... -->
34334 <!-- Memory Map XML DTD ................................ -->
34335 <!-- File: memory-map.dtd .............................. -->
34336 <!-- .................................... .............. -->
34337 <!-- memory-map.dtd -->
34338 <!-- memory-map: Root element with versioning -->
34339 <!ELEMENT memory-map (memory | property)>
34340 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34341 <!ELEMENT memory (property)>
34342 <!-- memory: Specifies a memory region,
34343 and its type, or device. -->
34344 <!ATTLIST memory type CDATA #REQUIRED
34345 start CDATA #REQUIRED
34346 length CDATA #REQUIRED
34347 device CDATA #IMPLIED>
34348 <!-- property: Generic attribute tag -->
34349 <!ELEMENT property (#PCDATA | property)*>
34350 <!ATTLIST property name CDATA #REQUIRED>
34353 @node Thread List Format
34354 @section Thread List Format
34355 @cindex thread list format
34357 To efficiently update the list of threads and their attributes,
34358 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34359 (@pxref{qXfer threads read}) and obtains the XML document with
34360 the following structure:
34363 <?xml version="1.0"?>
34365 <thread id="id" core="0">
34366 ... description ...
34371 Each @samp{thread} element must have the @samp{id} attribute that
34372 identifies the thread (@pxref{thread-id syntax}). The
34373 @samp{core} attribute, if present, specifies which processor core
34374 the thread was last executing on. The content of the of @samp{thread}
34375 element is interpreted as human-readable auxilliary information.
34377 @include agentexpr.texi
34379 @node Trace File Format
34380 @appendix Trace File Format
34381 @cindex trace file format
34383 The trace file comes in three parts: a header, a textual description
34384 section, and a trace frame section with binary data.
34386 The header has the form @code{\x7fTRACE0\n}. The first byte is
34387 @code{0x7f} so as to indicate that the file contains binary data,
34388 while the @code{0} is a version number that may have different values
34391 The description section consists of multiple lines of @sc{ascii} text
34392 separated by newline characters (@code{0xa}). The lines may include a
34393 variety of optional descriptive or context-setting information, such
34394 as tracepoint definitions or register set size. @value{GDBN} will
34395 ignore any line that it does not recognize. An empty line marks the end
34398 @c FIXME add some specific types of data
34400 The trace frame section consists of a number of consecutive frames.
34401 Each frame begins with a two-byte tracepoint number, followed by a
34402 four-byte size giving the amount of data in the frame. The data in
34403 the frame consists of a number of blocks, each introduced by a
34404 character indicating its type (at least register, memory, and trace
34405 state variable). The data in this section is raw binary, not a
34406 hexadecimal or other encoding; its endianness matches the target's
34409 @c FIXME bi-arch may require endianness/arch info in description section
34412 @item R @var{bytes}
34413 Register block. The number and ordering of bytes matches that of a
34414 @code{g} packet in the remote protocol. Note that these are the
34415 actual bytes, in target order and @value{GDBN} register order, not a
34416 hexadecimal encoding.
34418 @item M @var{address} @var{length} @var{bytes}...
34419 Memory block. This is a contiguous block of memory, at the 8-byte
34420 address @var{address}, with a 2-byte length @var{length}, followed by
34421 @var{length} bytes.
34423 @item V @var{number} @var{value}
34424 Trace state variable block. This records the 8-byte signed value
34425 @var{value} of trace state variable numbered @var{number}.
34429 Future enhancements of the trace file format may include additional types
34432 @node Target Descriptions
34433 @appendix Target Descriptions
34434 @cindex target descriptions
34436 @strong{Warning:} target descriptions are still under active development,
34437 and the contents and format may change between @value{GDBN} releases.
34438 The format is expected to stabilize in the future.
34440 One of the challenges of using @value{GDBN} to debug embedded systems
34441 is that there are so many minor variants of each processor
34442 architecture in use. It is common practice for vendors to start with
34443 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34444 and then make changes to adapt it to a particular market niche. Some
34445 architectures have hundreds of variants, available from dozens of
34446 vendors. This leads to a number of problems:
34450 With so many different customized processors, it is difficult for
34451 the @value{GDBN} maintainers to keep up with the changes.
34453 Since individual variants may have short lifetimes or limited
34454 audiences, it may not be worthwhile to carry information about every
34455 variant in the @value{GDBN} source tree.
34457 When @value{GDBN} does support the architecture of the embedded system
34458 at hand, the task of finding the correct architecture name to give the
34459 @command{set architecture} command can be error-prone.
34462 To address these problems, the @value{GDBN} remote protocol allows a
34463 target system to not only identify itself to @value{GDBN}, but to
34464 actually describe its own features. This lets @value{GDBN} support
34465 processor variants it has never seen before --- to the extent that the
34466 descriptions are accurate, and that @value{GDBN} understands them.
34468 @value{GDBN} must be linked with the Expat library to support XML
34469 target descriptions. @xref{Expat}.
34472 * Retrieving Descriptions:: How descriptions are fetched from a target.
34473 * Target Description Format:: The contents of a target description.
34474 * Predefined Target Types:: Standard types available for target
34476 * Standard Target Features:: Features @value{GDBN} knows about.
34479 @node Retrieving Descriptions
34480 @section Retrieving Descriptions
34482 Target descriptions can be read from the target automatically, or
34483 specified by the user manually. The default behavior is to read the
34484 description from the target. @value{GDBN} retrieves it via the remote
34485 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34486 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34487 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34488 XML document, of the form described in @ref{Target Description
34491 Alternatively, you can specify a file to read for the target description.
34492 If a file is set, the target will not be queried. The commands to
34493 specify a file are:
34496 @cindex set tdesc filename
34497 @item set tdesc filename @var{path}
34498 Read the target description from @var{path}.
34500 @cindex unset tdesc filename
34501 @item unset tdesc filename
34502 Do not read the XML target description from a file. @value{GDBN}
34503 will use the description supplied by the current target.
34505 @cindex show tdesc filename
34506 @item show tdesc filename
34507 Show the filename to read for a target description, if any.
34511 @node Target Description Format
34512 @section Target Description Format
34513 @cindex target descriptions, XML format
34515 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34516 document which complies with the Document Type Definition provided in
34517 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34518 means you can use generally available tools like @command{xmllint} to
34519 check that your feature descriptions are well-formed and valid.
34520 However, to help people unfamiliar with XML write descriptions for
34521 their targets, we also describe the grammar here.
34523 Target descriptions can identify the architecture of the remote target
34524 and (for some architectures) provide information about custom register
34525 sets. They can also identify the OS ABI of the remote target.
34526 @value{GDBN} can use this information to autoconfigure for your
34527 target, or to warn you if you connect to an unsupported target.
34529 Here is a simple target description:
34532 <target version="1.0">
34533 <architecture>i386:x86-64</architecture>
34538 This minimal description only says that the target uses
34539 the x86-64 architecture.
34541 A target description has the following overall form, with [ ] marking
34542 optional elements and @dots{} marking repeatable elements. The elements
34543 are explained further below.
34546 <?xml version="1.0"?>
34547 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34548 <target version="1.0">
34549 @r{[}@var{architecture}@r{]}
34550 @r{[}@var{osabi}@r{]}
34551 @r{[}@var{compatible}@r{]}
34552 @r{[}@var{feature}@dots{}@r{]}
34557 The description is generally insensitive to whitespace and line
34558 breaks, under the usual common-sense rules. The XML version
34559 declaration and document type declaration can generally be omitted
34560 (@value{GDBN} does not require them), but specifying them may be
34561 useful for XML validation tools. The @samp{version} attribute for
34562 @samp{<target>} may also be omitted, but we recommend
34563 including it; if future versions of @value{GDBN} use an incompatible
34564 revision of @file{gdb-target.dtd}, they will detect and report
34565 the version mismatch.
34567 @subsection Inclusion
34568 @cindex target descriptions, inclusion
34571 @cindex <xi:include>
34574 It can sometimes be valuable to split a target description up into
34575 several different annexes, either for organizational purposes, or to
34576 share files between different possible target descriptions. You can
34577 divide a description into multiple files by replacing any element of
34578 the target description with an inclusion directive of the form:
34581 <xi:include href="@var{document}"/>
34585 When @value{GDBN} encounters an element of this form, it will retrieve
34586 the named XML @var{document}, and replace the inclusion directive with
34587 the contents of that document. If the current description was read
34588 using @samp{qXfer}, then so will be the included document;
34589 @var{document} will be interpreted as the name of an annex. If the
34590 current description was read from a file, @value{GDBN} will look for
34591 @var{document} as a file in the same directory where it found the
34592 original description.
34594 @subsection Architecture
34595 @cindex <architecture>
34597 An @samp{<architecture>} element has this form:
34600 <architecture>@var{arch}</architecture>
34603 @var{arch} is one of the architectures from the set accepted by
34604 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34607 @cindex @code{<osabi>}
34609 This optional field was introduced in @value{GDBN} version 7.0.
34610 Previous versions of @value{GDBN} ignore it.
34612 An @samp{<osabi>} element has this form:
34615 <osabi>@var{abi-name}</osabi>
34618 @var{abi-name} is an OS ABI name from the same selection accepted by
34619 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
34621 @subsection Compatible Architecture
34622 @cindex @code{<compatible>}
34624 This optional field was introduced in @value{GDBN} version 7.0.
34625 Previous versions of @value{GDBN} ignore it.
34627 A @samp{<compatible>} element has this form:
34630 <compatible>@var{arch}</compatible>
34633 @var{arch} is one of the architectures from the set accepted by
34634 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34636 A @samp{<compatible>} element is used to specify that the target
34637 is able to run binaries in some other than the main target architecture
34638 given by the @samp{<architecture>} element. For example, on the
34639 Cell Broadband Engine, the main architecture is @code{powerpc:common}
34640 or @code{powerpc:common64}, but the system is able to run binaries
34641 in the @code{spu} architecture as well. The way to describe this
34642 capability with @samp{<compatible>} is as follows:
34645 <architecture>powerpc:common</architecture>
34646 <compatible>spu</compatible>
34649 @subsection Features
34652 Each @samp{<feature>} describes some logical portion of the target
34653 system. Features are currently used to describe available CPU
34654 registers and the types of their contents. A @samp{<feature>} element
34658 <feature name="@var{name}">
34659 @r{[}@var{type}@dots{}@r{]}
34665 Each feature's name should be unique within the description. The name
34666 of a feature does not matter unless @value{GDBN} has some special
34667 knowledge of the contents of that feature; if it does, the feature
34668 should have its standard name. @xref{Standard Target Features}.
34672 Any register's value is a collection of bits which @value{GDBN} must
34673 interpret. The default interpretation is a two's complement integer,
34674 but other types can be requested by name in the register description.
34675 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
34676 Target Types}), and the description can define additional composite types.
34678 Each type element must have an @samp{id} attribute, which gives
34679 a unique (within the containing @samp{<feature>}) name to the type.
34680 Types must be defined before they are used.
34683 Some targets offer vector registers, which can be treated as arrays
34684 of scalar elements. These types are written as @samp{<vector>} elements,
34685 specifying the array element type, @var{type}, and the number of elements,
34689 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
34693 If a register's value is usefully viewed in multiple ways, define it
34694 with a union type containing the useful representations. The
34695 @samp{<union>} element contains one or more @samp{<field>} elements,
34696 each of which has a @var{name} and a @var{type}:
34699 <union id="@var{id}">
34700 <field name="@var{name}" type="@var{type}"/>
34706 If a register's value is composed from several separate values, define
34707 it with a structure type. There are two forms of the @samp{<struct>}
34708 element; a @samp{<struct>} element must either contain only bitfields
34709 or contain no bitfields. If the structure contains only bitfields,
34710 its total size in bytes must be specified, each bitfield must have an
34711 explicit start and end, and bitfields are automatically assigned an
34712 integer type. The field's @var{start} should be less than or
34713 equal to its @var{end}, and zero represents the least significant bit.
34716 <struct id="@var{id}" size="@var{size}">
34717 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34722 If the structure contains no bitfields, then each field has an
34723 explicit type, and no implicit padding is added.
34726 <struct id="@var{id}">
34727 <field name="@var{name}" type="@var{type}"/>
34733 If a register's value is a series of single-bit flags, define it with
34734 a flags type. The @samp{<flags>} element has an explicit @var{size}
34735 and contains one or more @samp{<field>} elements. Each field has a
34736 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
34740 <flags id="@var{id}" size="@var{size}">
34741 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34746 @subsection Registers
34749 Each register is represented as an element with this form:
34752 <reg name="@var{name}"
34753 bitsize="@var{size}"
34754 @r{[}regnum="@var{num}"@r{]}
34755 @r{[}save-restore="@var{save-restore}"@r{]}
34756 @r{[}type="@var{type}"@r{]}
34757 @r{[}group="@var{group}"@r{]}/>
34761 The components are as follows:
34766 The register's name; it must be unique within the target description.
34769 The register's size, in bits.
34772 The register's number. If omitted, a register's number is one greater
34773 than that of the previous register (either in the current feature or in
34774 a preceeding feature); the first register in the target description
34775 defaults to zero. This register number is used to read or write
34776 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34777 packets, and registers appear in the @code{g} and @code{G} packets
34778 in order of increasing register number.
34781 Whether the register should be preserved across inferior function
34782 calls; this must be either @code{yes} or @code{no}. The default is
34783 @code{yes}, which is appropriate for most registers except for
34784 some system control registers; this is not related to the target's
34788 The type of the register. @var{type} may be a predefined type, a type
34789 defined in the current feature, or one of the special types @code{int}
34790 and @code{float}. @code{int} is an integer type of the correct size
34791 for @var{bitsize}, and @code{float} is a floating point type (in the
34792 architecture's normal floating point format) of the correct size for
34793 @var{bitsize}. The default is @code{int}.
34796 The register group to which this register belongs. @var{group} must
34797 be either @code{general}, @code{float}, or @code{vector}. If no
34798 @var{group} is specified, @value{GDBN} will not display the register
34799 in @code{info registers}.
34803 @node Predefined Target Types
34804 @section Predefined Target Types
34805 @cindex target descriptions, predefined types
34807 Type definitions in the self-description can build up composite types
34808 from basic building blocks, but can not define fundamental types. Instead,
34809 standard identifiers are provided by @value{GDBN} for the fundamental
34810 types. The currently supported types are:
34819 Signed integer types holding the specified number of bits.
34826 Unsigned integer types holding the specified number of bits.
34830 Pointers to unspecified code and data. The program counter and
34831 any dedicated return address register may be marked as code
34832 pointers; printing a code pointer converts it into a symbolic
34833 address. The stack pointer and any dedicated address registers
34834 may be marked as data pointers.
34837 Single precision IEEE floating point.
34840 Double precision IEEE floating point.
34843 The 12-byte extended precision format used by ARM FPA registers.
34846 The 10-byte extended precision format used by x87 registers.
34849 32bit @sc{eflags} register used by x86.
34852 32bit @sc{mxcsr} register used by x86.
34856 @node Standard Target Features
34857 @section Standard Target Features
34858 @cindex target descriptions, standard features
34860 A target description must contain either no registers or all the
34861 target's registers. If the description contains no registers, then
34862 @value{GDBN} will assume a default register layout, selected based on
34863 the architecture. If the description contains any registers, the
34864 default layout will not be used; the standard registers must be
34865 described in the target description, in such a way that @value{GDBN}
34866 can recognize them.
34868 This is accomplished by giving specific names to feature elements
34869 which contain standard registers. @value{GDBN} will look for features
34870 with those names and verify that they contain the expected registers;
34871 if any known feature is missing required registers, or if any required
34872 feature is missing, @value{GDBN} will reject the target
34873 description. You can add additional registers to any of the
34874 standard features --- @value{GDBN} will display them just as if
34875 they were added to an unrecognized feature.
34877 This section lists the known features and their expected contents.
34878 Sample XML documents for these features are included in the
34879 @value{GDBN} source tree, in the directory @file{gdb/features}.
34881 Names recognized by @value{GDBN} should include the name of the
34882 company or organization which selected the name, and the overall
34883 architecture to which the feature applies; so e.g.@: the feature
34884 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
34886 The names of registers are not case sensitive for the purpose
34887 of recognizing standard features, but @value{GDBN} will only display
34888 registers using the capitalization used in the description.
34895 * PowerPC Features::
34900 @subsection ARM Features
34901 @cindex target descriptions, ARM features
34903 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
34904 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
34905 @samp{lr}, @samp{pc}, and @samp{cpsr}.
34907 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
34908 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
34910 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
34911 it should contain at least registers @samp{wR0} through @samp{wR15} and
34912 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
34913 @samp{wCSSF}, and @samp{wCASF} registers are optional.
34915 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
34916 should contain at least registers @samp{d0} through @samp{d15}. If
34917 they are present, @samp{d16} through @samp{d31} should also be included.
34918 @value{GDBN} will synthesize the single-precision registers from
34919 halves of the double-precision registers.
34921 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
34922 need to contain registers; it instructs @value{GDBN} to display the
34923 VFP double-precision registers as vectors and to synthesize the
34924 quad-precision registers from pairs of double-precision registers.
34925 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
34926 be present and include 32 double-precision registers.
34928 @node i386 Features
34929 @subsection i386 Features
34930 @cindex target descriptions, i386 features
34932 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
34933 targets. It should describe the following registers:
34937 @samp{eax} through @samp{edi} plus @samp{eip} for i386
34939 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
34941 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
34942 @samp{fs}, @samp{gs}
34944 @samp{st0} through @samp{st7}
34946 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
34947 @samp{foseg}, @samp{fooff} and @samp{fop}
34950 The register sets may be different, depending on the target.
34952 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
34953 describe registers:
34957 @samp{xmm0} through @samp{xmm7} for i386
34959 @samp{xmm0} through @samp{xmm15} for amd64
34964 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
34965 @samp{org.gnu.gdb.i386.sse} feature. It should
34966 describe the upper 128 bits of @sc{ymm} registers:
34970 @samp{ymm0h} through @samp{ymm7h} for i386
34972 @samp{ymm0h} through @samp{ymm15h} for amd64
34976 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
34977 describe a single register, @samp{orig_eax}.
34979 @node MIPS Features
34980 @subsection MIPS Features
34981 @cindex target descriptions, MIPS features
34983 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
34984 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
34985 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
34988 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
34989 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
34990 registers. They may be 32-bit or 64-bit depending on the target.
34992 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
34993 it may be optional in a future version of @value{GDBN}. It should
34994 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
34995 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
34997 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
34998 contain a single register, @samp{restart}, which is used by the
34999 Linux kernel to control restartable syscalls.
35001 @node M68K Features
35002 @subsection M68K Features
35003 @cindex target descriptions, M68K features
35006 @item @samp{org.gnu.gdb.m68k.core}
35007 @itemx @samp{org.gnu.gdb.coldfire.core}
35008 @itemx @samp{org.gnu.gdb.fido.core}
35009 One of those features must be always present.
35010 The feature that is present determines which flavor of m68k is
35011 used. The feature that is present should contain registers
35012 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35013 @samp{sp}, @samp{ps} and @samp{pc}.
35015 @item @samp{org.gnu.gdb.coldfire.fp}
35016 This feature is optional. If present, it should contain registers
35017 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35021 @node PowerPC Features
35022 @subsection PowerPC Features
35023 @cindex target descriptions, PowerPC features
35025 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35026 targets. It should contain registers @samp{r0} through @samp{r31},
35027 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35028 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35030 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35031 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35033 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35034 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35037 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35038 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35039 will combine these registers with the floating point registers
35040 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35041 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35042 through @samp{vs63}, the set of vector registers for POWER7.
35044 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35045 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35046 @samp{spefscr}. SPE targets should provide 32-bit registers in
35047 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35048 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35049 these to present registers @samp{ev0} through @samp{ev31} to the
35052 @node Operating System Information
35053 @appendix Operating System Information
35054 @cindex operating system information
35060 Users of @value{GDBN} often wish to obtain information about the state of
35061 the operating system running on the target---for example the list of
35062 processes, or the list of open files. This section describes the
35063 mechanism that makes it possible. This mechanism is similar to the
35064 target features mechanism (@pxref{Target Descriptions}), but focuses
35065 on a different aspect of target.
35067 Operating system information is retrived from the target via the
35068 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35069 read}). The object name in the request should be @samp{osdata}, and
35070 the @var{annex} identifies the data to be fetched.
35073 @appendixsection Process list
35074 @cindex operating system information, process list
35076 When requesting the process list, the @var{annex} field in the
35077 @samp{qXfer} request should be @samp{processes}. The returned data is
35078 an XML document. The formal syntax of this document is defined in
35079 @file{gdb/features/osdata.dtd}.
35081 An example document is:
35084 <?xml version="1.0"?>
35085 <!DOCTYPE target SYSTEM "osdata.dtd">
35086 <osdata type="processes">
35088 <column name="pid">1</column>
35089 <column name="user">root</column>
35090 <column name="command">/sbin/init</column>
35091 <column name="cores">1,2,3</column>
35096 Each item should include a column whose name is @samp{pid}. The value
35097 of that column should identify the process on the target. The
35098 @samp{user} and @samp{command} columns are optional, and will be
35099 displayed by @value{GDBN}. The @samp{cores} column, if present,
35100 should contain a comma-separated list of cores that this process
35101 is running on. Target may provide additional columns,
35102 which @value{GDBN} currently ignores.
35116 % I think something like @colophon should be in texinfo. In the
35118 \long\def\colophon{\hbox to0pt{}\vfill
35119 \centerline{The body of this manual is set in}
35120 \centerline{\fontname\tenrm,}
35121 \centerline{with headings in {\bf\fontname\tenbf}}
35122 \centerline{and examples in {\tt\fontname\tentt}.}
35123 \centerline{{\it\fontname\tenit\/},}
35124 \centerline{{\bf\fontname\tenbf}, and}
35125 \centerline{{\sl\fontname\tensl\/}}
35126 \centerline{are used for emphasis.}\vfill}
35128 % Blame: doc@cygnus.com, 1991.